Hormones: Thyroxine, T3, T4 Show
Advantages: Study lifespan changes, wider range of studies (ethics), bigger sample, less
expensive, ease of replication & quantification, environmental control Peptide hormones: Short chain of Amino Acids ex. glucagon, insulin, leptin. Stored in endocrine cells and released via exocytosis, do not require carrier proteins, shorter half life, water and blood soluble. Steroid Hormones: Require carrier protein, larger, fat soluble, unique carbon structure, synthesized from cholesterol, not stored in cells, longer half life. Ex. Progesterone, testosterone, estrogen, cortisol, aldosterone Brain activity- fMRI, EEG, Electrodes, in vivo electrode physiology A. Altricial, precocial, semi-precocial Answer: B. Precocial, altricial, semi-precocial Sets with similar termsWhat is parental behavior? Any behavior that contributes directly to the survival of fertilized eggs or offspring that have left the body of the female What are the types of parental behavior? Maternal: mother, most common among mammals (90%) What type of parental care is most common in birds? biparental What type of parental care is most common in mammals? maternal Why Parental Behavior? From an evolutionary perspective, mating is not sufficient for reproduction to be successful Parental care is critical for reproductive success Parental care is critical for reproductive success Determined by their offspring that manage to survive and produce descendants How do parents maximize fitness? To maximize fitness, the optimal strategy for each parent is to provide sufficient care but no more than is necessary to produce successful offspring The amount of care a parent provides varies greatly within and among species Some species provide little or no parental
care: Cowbirds Cowbirds Nest parasites Brown trout Females simply release hundreds or even thousands of
eggs from their bodies Female Nile crocodiles Provide a low level of parental care: build nests and protect their newly hatched young by carrying them to the water in their mouths. What are altricial offspring? (e.g. dogs, rats)
what are precocial offspring? (e.g. sheep, deer, guinea pigs) what are semi-precocial offspring? (e.g. humans
and other primates) Rat maternal care Rats have a 22 day gestation period (pregnancy) What are the components of rat maternal behavior during gestation? Nest building What are the components of rat maternal behavior during parturition? Lick and groom area around the vagina and assist with uterine contractions by pulling pups out with the teeth What are the components of rat maternal behavior after birth? IMMEDIATELY AFTER BIRTH, mothers (dams) are maternal and display behaviors necessary for altricial young to survive: What is placentophagia? What are hypotheses as to why animals engage in this practice? Placentophagia (Kristal et al., 2012) - when the mother rat eats the placenta and umbilical cords of all the pups. Why? Placebo-controlled studies assessing the effects of placentophagy for postpartum recovery and health are needed to help elucidate any positive or negative effects What hormones regulate the immediate onset of maternal care at parturition (birth)? prolactin and estradiol increase greatly after parturition How do concentrations of these hormones change across gestation (pregnancy) and at parturition? Estradiol: is low throughout the entire pregnancy and spikes up a couple days before parturition, takes a dip down on day 22 and then spikes up even higher than before right after parturition What are two approaches that have been used to show that hormones regulate the onset of maternal behavior? 1) Foster pups are presented to adult females in different endocrine states. Whether and how quickly these females begin to behave maternally is measured. 1) Foster pups are presented to adult females in different endocrine states. Whether and how quickly these females begin to behave maternally is measured. Hormones significantly reduce the amount of time it takes for a virgin female to behave maternally and therefore promote maternal care 2) Pregnancy termination by hysterectomy (removal of the uterus, fetuses, and placenta) on days 16-19 pregnancy Results in maternal behavior towards foster pups within 1-2 days Hormonal profile of late pregnancy stimulates the onset of maternal care What is maternal sensitization or concaveation? when mothers learns to care for pups nulliparous females are fearful of pups at first but after 5-6 days of exposure they behave maternally - Hormones significantly reduce the amount of time it takes for a virgin female to behave maternally and therefore promote maternal care How long does it take the following groups to behave maternally when presented with foster pups: new mother, late pregnant female, virgin female, virgin female transfused with blood of new mother, OVX virgin female treated with a hormonal regimen that mimics changes seen during late pregnancy? Mothers that have recently given birth: immediately Late pregnant: 1-2 days Nulliparous (virgin): are fearful of pups and find them (odors) aversive Nulliparous females transfused with blood from a new mother: 1 day Nulliparous females that are ovariectomized and treated with a hormonal regimen (E+P+PRL) that mimics changes seen during late pregnancy: 1-2 days how long does it take female rat with previous maternal experience? female with maternal memory will display maternal behaviors to pups within one day How long does it take pregnant rat hysterectomized on days 16-19 of pregnancy? Results in maternal behavior towards foster pups within 1-2 days Be able to explain why and how hysterectomy induces maternal behavior. Produces similar endocrine profile to that found in a normal rat just prior to birth Hormonal profile of late pregnancy stimulates the onset of maternal care Does oxytocin act as a hormone or neurohormone to: facilitate maternal behavior? uterine contractions? milk ejection? Oxytocin peripherally (hormone): Oxytocin centrally (neurohormone): How do hormones promote maternal behavior? Approach-Avoidance Model: **why do the stimulatory effects of hormones on maternal behavior diminish after a few days? Latency to display maternal behavior towards foster pups measured in pregnant females at various time points after C-section: Hormonal events of pregnancy termination result in heightened maternal responsiveness for just a few days Is the maintenance of maternal behavior dependent on hormones? What is the evidence? If not, what maintains maternal behavior? Some hormones (i.e. oxytocin) may continue to play a role in modulating the quality and quantity of maternal care but hormones are not necessary to maintain maternal behavior during the remainder of the postpartum period Instead,
the maintenance of maternal behavior depends on pup stimulation (i.e. somatosensory or tactile feedback that a dam receives from the pups) Behaviors that maintain maternal behavior: Hormones induce maternal care but pup interactions maintain it **Somatosensory and tactile feedback that a dam receives from the pups is necessary to maintain maternal behavior - Anesthetizing or severing the nerves that innervate the mouth -->
nest building, licking and pup retrieval abolished **what are the interactions btw mother and pup that maintain behavior? - distal cues: of sight and sound stimulate contact seeking Understand the neural circuitry of maternal behavior, particularly the role of the MPOA in early to mid pregnancy MPOA inhibits circuit that promotes aversion to pup odors AVOID: pup odor activates olfactory bulb --> Medial and cortical amygdala --> Anterior hypothalamus and the Periaquiductal gray --> causes aversion to pups Understand the neural circuitry of maternal behavior, particularly the role of the MPOA in late pregnancy Na --> PVN --> triggers oxytocin release --> goes into the oxytocin receptors of the mPOA --> stimulates MPOA which activates Understand the neural circuitry of maternal behavior, particularly the role of the MPOA in lactation APPROACH Maternal care is disrupted when 1) interfere with DA
neurotransmission 2) disrupt the connection between the MPOA and VTA MPOA activates circuit that enhances approach/attraction to pups the VTA and NAcc interact with each other and create DA which leads to maternal behavior, rewarding, and motivation. MPOA and Maternal Behavior Neural activity in the MPOA (as measured by c-fos) increases in dams Lesions of MPOA disrupt maternal behavior Has receptors for E, PRL and OT which increase in number during pregnancy to maximize sensitivity
What about pups do adult nulliparous rats find aversive? How can this aversion be overcome? the odor What is maternal memory? What does it reveal about the hormonal regulation of maternal behavior? 1. Previous experience as a mother ("maternal memory") • How has it been shown that maternal care affects the maternal care of female offspring? What is affected? Are these effects due to genetic/prenatal factors or differences in postpartum maternal care? How has this been shown? Own experience of being mothered as an infant Individual variations in maternal care are transmitted across generations Individual Variations in Maternal Care are Associated with Differences in Oxytocin Receptor Levels What is the hormonal profile of pregnancy in humans? High estrogens and progesterone throughout pregnancy
(different than rodents) Why is studying hormonal correlates of parental care in humans difficult? Establishing hormonal correlates of human
maternal behavior is difficult: What hormonal changes have been associated with human maternal behavior and how are these hormonal changes thought to promote maternal behavior? Mothers with an increase in the ratio of estradiol to progesterone during pregnancy have more positive attachment to their infants than mothers with a decrease in the ratio of these hormones Plasma oxytocin levels at 2 weeks postpartum positively correlated with maternal bonding behaviors (gaze, vocalizations, positive affect, and affectionate touch) as assessed during a 15 min mother-infant interaction (Feldman et al., 2007)-correlational Handgrip force reaction to infant crying reduced in nulliparous women given intranasal oxytocin suggesting that oxytocin may inhibit parental hostility (Bakermans-Kranenburg et al., 2012) Mothers with higher concentrations of blood cortisol engage in more physically affectionate behaviors and talked more often to their babies than mothers with low cortisol (Fleming et al., 1987) What genetic factors have been linked to individual differences in human maternal care? Polymorphism in oxytocin receptor gene Polymorphism in dopamine receptor 4 gene What are the 4 major systems and the brain regions within those system that fMRI studies have implicated in maternal caregiving? - Empathy: STS --> IP --> IF (understanding child's facial expression), AI (understand what the child feels) More isn't necessarily better when it comes to activation of these brain systems. There may be an optimal range of activation of these neural systems -too low (neglectful) or too high (intrusive) may not support adequate parenting. Paternal behavior is uncommon and only found in ~10% of mammalian species Among mammals, what makes it more likely that a male will care for his offspring? Males care for offspring when they can increase their own reproductive fitness: Tends to occur in in species that are monogamous In California mice fathers: Exclusively monogamous and form long-term pair bonds With the exception of lactation, males and females of these species exhibit the same parental behaviors to the same extent In California mice fathers: Elevated prolactin levels are associated with paternal behavior in California mice In California mice
fathers: Aromatase inhibitor blocks effects of T suggesting that T promotes paternal behavior through conversion to estradiol Unusual pattern! In California mice fathers:
mPOA is important for parental behavior in male and female California Mice What hormonal changes have been associated with human paternal behavior? Oxytocin levels associated with greater parental care and more infant touch in fathers Prolactin increases in fathers prior to birth and in men who respond physiologically to the sounds of babies crying Testosterone and cortisol also linked to paternal care (Berg & Wynne-Edwards, 2001) How are the hormonal changes father thought to promote paternal care? Compare hormonal responses of new fathers and non-fathers exposed to sounds of baby crying What do fMRI studies suggest about the neural basis of human paternal care?
fMRI studies show that when a father hears his own child's cries, areas of heightened brain activity include the include the frontal cortex, insula, thalamus and superior temporal cortex (Swain, 2008) - same as mothers Difference: brain activity patterns don't change as quickly for fathers as they do for mothers What did the study looking at the relationship between paternal care and testicle size show? (Mascaro
et al., 2013) Other primates: • What two general categories can social behavior be divided into? Most animals must maintain a balance between affiliation and aggression • Affiliation is thought to evolve from what other behaviors? What hormone may be involved? thought to have evolved from parental behavior. • What are the overlapping brain regions controlling maternal love and romantic love? Theory of affiliative behavior evolving from parental behavior is supported by fMRI showing some overlapping areas of activation (orange) for people viewing photos of their babies and photos of romantic partners Areas such as: putamen, caudate What is interesting about these regions in relation to attachment? As well as involving a lot of the same hormones, a lot of the same brain regions are activated by both romantic and maternal love. What is the basis of pair-bonding differences? testosterone What is different about OTR in monogamous vs polygamous voles? Why do you see a difference? The prairie voles have more OTR in the nucleus accumbens, fronto-parietal cortex, lateral amygdala, and the thalamus. • What is the role of Dopamine in pair-bond formation? Also key areas in the mesolimbic dopamine reward system Reward processing depends on the mesocorticolimbic dopaminergic system consisting of dopamine neurons in the ventral tegmental area and their projections to the nucleus accumbens, prefrontal cortex and other brain areas27. The ventral pallidum is a major target of the nucleus accumbens28, 29, and it further processes and relays stimuli from the nucleus accumbens to mediate locomotor responses to rewarding stimuli **3. Vasopressin: Different AVP receptor distribution between monogamous and polygamous voles too what two things work together to promote pair-bonding? prairie voles have higher expression levels of __________ As we saw on the previous slide, AVP and Da act together to promote pair-bonding in monogamous species like prairie voles. Prairie voles have have higher expression levels of the V1aR in the ventral pallidum compared to polygamous meadow voles. Where a receptor is expressed changes what kind of behavior it influences • What is the three-chamber preference test? What type of results do you see with this test? What happens when you increase AVP receptor expression in polygamous voles and test in the three-chamber preference test? Lim et al., 2004 Used a viral vector to introduce DNA into cells in Resulted in 3-fold more V1aR binding in V1aR overexpression in wrong area Test: Partner preference test Measure: Huddling time (significant preference indicates a pair-bond has formed) Results 1: Increased expression of this single gene for
V1aR in the VP resulted in normally polygamous voles that do not show social bonds to now display significant preference for huddling with partner over stranger. This Results 2: Administration of a Dopamine D2- receptor antagonist prior to the 24 hours of housing with partner prevented this pair-bond from forming in the V1aR-overexpressing Meadow voles. Indicates that Da transmission is necessary for pair-bonding to be rewarding and for forming conditioned partner preference. • Are high levels of testosterone expected in polygamous or monogamous species? What is the benefit of having low levels of testosterone? Males from monogamous species have lower testosterone concentrations and smaller testes than those of polygamous species benefit of having low testosterone: inhibits aggression, tolerant of other voles Affiliation Summary: Affiliative behaviors were evolutionarily co-opted from parental behaviors and depend on similar hormones Hormones can control the type of social bonds species form and their mating systems, namely: Testosterone, Oxytocin, and Vasopressin For monogamous species, OT and AVP activity in structures of the mesolimbic reward pathway serves to make pair-bonding rewarding • What is the definition of aggression (Moyer, 1968)? Aggressive behaviors keep animals apart; involves overt behavior with the intention of causing harm or other
unpleasantness to another individual What are some types of aggression? Different types of aggression appear in different contexts and have different physiological causes Most natural occurrences of aggressive behavior take place because of competition over limited resources • What circumstantial evidence links androgen levels to aggression? Circumstantial evidence that androgenic steroid hormones mediate aggression: There is overwhelming circumstantial evidence that androgenic steroid hormones mediate aggression. • Why do male red deer display aggressive behavior during the fall? Intermale aggression and growth of antlers in red deer is dependent upon a large increase in testosterone production leading up to annual mating season. What is the correlation between testosterone, antler growth, and aggression in red deer? At the end of the summer, T levels increase and peak in mid autumn, the rising androgen levels are accompanied by antler growth, and aggressive behavior. Mating occurs for about 2 weeks in mid autumn. After mating, T levels diminish, aggressive behaviors wane, antler growth ceases, and males engage in few agonistic interactions. What are the effects of castration in red deer? Fighting helps to establish the social rank of male deer. Higher status results in higher access to mates. So from these results you can gather that testosterone levels are playing a large role in the aggression and social behavior of the deer and that the timing of it is important. Having more T when other males have low T is an advantage. Having lower T than the other males is a disadvantage. The effects of testosterone implantation in summer and winter? Castrated males given slow-releasing
capsules of T during winter were more aggressive, retained their antlers, and rose in social rank while the T of other males was dropping. Demonstrates that T affects social status of males in 2 ways: • What allows group living in winter in rodents and why is it beneficial? What hormone mediates this? Rodent species (e.g., meadow voles) that are more aggressive during breeding season and warmer weather become more tolerant of other rodents in winter to increase survival This decrease in aggression is accompanied by lower androgen concentrations, decreased number of androgen receptors, and reproductive regression In some species, castrated males still exhibit seasonal aggression In other species like Syrian and Siberian hamsters, decreased androgen levels due to winter-like conditions results in an increase in aggressive behavior This means Androgens are not mediating aggression here • What is another possible mediator of aggression in some rodent species? How does this mediator change effects based on season? Explanation: An estrogen signaling system that also mediates aggression seasonally Rapid effects of injection in winter are mediated by nongenomic mechanisms (phosphorylation of kinases & regulation of transmitter release) Inhibitory effect of estradiol injection on aggression in summer conditions is mediated by changes in gene expression (slower) • In what season do we expect humans to behave more aggressively? Human males show seasonal variation in blood testosterone concentration, but a direct causal link to increased aggression has not been established • What causes increased levels of circulating androgens in males during puberty? The testes grow
larger Aggression & Puberty In Syrian hamsters, fighting style follows a defined pattern across development • What are the different areas hamsters focus on when they attack other con-specifics and how does this focus change during puberty? Prepuberty: attacks aimed at face- mostly play fighting • Why do male rodents show enhanced aggressive behavior during puberty? What is the evolutionary advantage of this behavior? What is the benefit of aggression peaking around puberty far male rodents? There is evolutionary value in increased
aggression The higher the population density, the more aggression males are exposed to, and in turn, the more aggressive they become, like in the case of the socially stressed syrian hamsters • What are the two strategies primates use to join a new group during the pubertal period and what hormones are associated with each of these strategies? Dispersal also occurs in primates during
puberty. For example, young male rhesus monkeys become the target of adult aggressive behaviors in their natal group at this time, and must find a new group to join Behavioral and endocrine factors predict what strategy a monkey will use: • What were the 3 major theories discussed that help to explain sex differences in aggression in boys and girls? 1. Males have higher concentrations of circulating androgens • Understand how we know that aggression is organized perinatally by androgens but requires the presence of androgens after puberty to be fully expressed. male mice castrated before day 6 + T in adulthood = low levels of
aggression What does this tell us? - In other words, males normally act more aggressive than females due to perinatal organization by androgens, but also that androgens must be present after puberty for the behavior to be expressed • In which species are females more aggressive than males? Female Syrian Hamsters are usually more aggressive than males. Housing condition does not significantly affect aggression level in intact hamsters. Estradiol and progesterone are acting like testosterone • How can behavior affect hormone concentrations? What hormones are affected? What are some examples of how this happens? Competition in Animals: • Describe the winner effect seen in California mice. In male California mice, winning fight enhances ability to win and motivation to engage in subsequent fights, but only if previous win was in its home cage. This effect is mediated by androgens via up-regulation of androgen receptors in reward processing brains areas (e.g., VTA and nucleus accumbens) • Understand how hormones are affected in human competition. Competition in Humans: Males students played a doubles tennis match, best of 5 wins $200. Measured testosterone 1 hour before and after the game > Blood T levels are more likely to be affected by winning a contest if the outcome is due to the man's effort. • What is conditioned social defeat? A Syrian hamster defeated in its home cage will subsequently fail to defend their own home cage, even if the new intruder is smaller or
non-aggressive • What are the two main theories for the effects of androgens on human antisocial behaviors? There is a positive correlation between circulating blood androgen concentrations and violence in people incarcerated for violent crimes Affect of androgens on human antisocial behavior: 2 hypotheses Indirect effect: Androgens promote a constellation of traits including social dominance, competitiveness, and thrill seeking that can be expressed as either anti-social or prosocial behavior depending on the individual's resources and background (AKA environment as a moderator) Key Aggression Circuit Ares: Prefrontal cortex • What is the aggression circuit in rodents? A) in rodents information from the OB is processed by the medial amygdala and sent to the lateral septum (LAS), Bed Nucleus of the Stria terminalis, and the anterior hypothalamic area (AHA). It ultimately ends in the PAG which promotes species specific aggression. Stress can inhibit aggression via inhibitory inputs from the OFC (orbitofrontal), hippocampus and PVN (paraventricular nuc). what is the aggression circuit in primates? B) in primates, aggression is evoked by visual or vocal signals. Activation of the MEA results in activation of BNST and anterior hypothalamus (AHA) which activate PAG for aggressive output. Inputs from OFC might inhibit aggression by reducing MeA responsiveness. What is a common structure in both that mediates aggression? the PAG mediates aggression for both **Physiological Mechanisms- Rats fMRI study of male rats exposed to a male intruder and a female cage mate during
scan Decreasing Aggressive response: Treatment with Vasopressin Va1 receptor antagonist also suppressed this activation • How does 5HT affect aggression? Nearly all neurotransmitters have been implicated in some way
in aggressive behavior, of these, serotonin (5-HT) is considered the most influential regulator of aggression Social Behavior Summary Oxytocin and Vasopressin are associated with affiliate behaviors and work in combination with Dopamine to promote affiliation in monogamous species • What is homeostasis? The process by which animals maintain a fairly stable internal environment Be able to describe the analogy of a thermostat as a homeostatic device. Most homeostatic systems operate like a thermostatically controlled heating and cooling system • How do endotherms regulate temperature? Most mammals and birds How do ectotherms regulate temperature? Not by physiological methods • How does body temp change when we are ill and why? How do iguanas regulate their body temp when they are ill? What is the adaptive consequence? In the laboratory, iguanas will regulate their body temp by moving toward or away from a heat source and settle where it can maintain its body temp at 37o C If an iguana is infected with a bacteria they will behaviorally produce a fever to fight the infection by positioning themselves closer to the heat This has adaptive consequences because a greater percentage of iguanas survive if they able to elevate their temperature • What are thermoreceptors? Where are they found? detect blood temperature there are also thermoreceptors in the skin that detect external temperature • What area of the brain controls thermoregulation? the hypothalamus controls thermoregulation What input does it (the hypothalamus) receive? central (anterior hypothalamus) and peripheral input. What effectors do they regulate? The thermoregulatory center of the
hypothalamus regulates the following effectors: Be able to describe the various responses to high and low temps. PHYSIOLOGICAL AND BEHAVIORAL RESPONSES to adjust body temp: Be able to describe the various responses to high and low temps. low temperatures: muscles contract using vasoconstriction. less heat is carried from the core to the surface of the body, maintaining core temperature.
extremities can turn blue and feel cold and can even be damaged (frostbite) Be able to describe the various responses to high and low temps. low temp: no sweat produced Be able to describe the various responses to high and low temps. low temp: muscles contract, raising skin hairs and trapping an insulating layer of still, warm air next to the skin. now very effective in humans, just causing
goosebumps Be able to describe the various responses to high and low temps. low temp: muscles contract and relax repeatedly generating heat by friction and from metabolic reactions Be able to describe the various responses to high and low temps. low temp: glands secrete adrenaline and thyroxine respectively, which increase the metabolic rate in different tissues, especially the liver, so generating heat. Be able to describe the various
responses to high and low temps. low temp: curling up, huddling finding shelter, putting on more clothes • What are the two types of thirst and what are they caused by? Osmotic thirst: If the concentration of NaCl in the extracellular fluid increases osmosis will
draw water out of the cells --> cellular dehydration --> potent stimulus for osmotic thirst Hypovolemic thirst: Caused by reduced blood volume as a result of hemorrhage or excessive diarrhea, vomiting, perspiration How are they (the two types of thirst) detected (know the types of receptors and where they are found)? Osmotic: Hypovolemic: What hormone(s) does each type of thirst stimulate the secretion of and what effects do they have? osmotic: Hypovolemic: What quenches each type of thirst? Drinking water quenches osmotic thirst Drinking water will NOT quench hypovolemic thirst! Must replace water, as well as sodium, and other solutes. (gatorade) • What is diabetes insipidus? What are its causes, symptoms and treatment? What animal model mimics this disorder? ADH important for fluid balance • What hormone maintains physiological homeostasis of sodium balance? How? Because Na+ is a major component of extracellular fluid and is important for fluid balance, it too must be maintained at a within precise limits (135-145 mmol/L in blood plasma) • What happens to a rat if the adrenal glands are removed? Why? What can prevent this? What is salt intake like before and after adrenalectomy? How is this an example of behavioral homeostasis? Adrenalectomized (ADX) rats usually die within one week because without aldosterone, they cannot retain enough sodium How is this different in Syrian hamsters? Does this prove that hamsters are less intelligent than rats? Why or why not? Like rats, Syrian hamsters will
perish if ADX • Are herbivores adapted to retain or excrete sodium? Why? Obtain sodium from plants Are carnivores adapted to retain or excrete sodium? Why? Not
under the same sodium pressures as herbivores • What did the Blair West et al. (1968) study demonstrate? Demonstrated that animals can cope with a variations in sodium availability in their environment by adapting their physiology, morphology and behavior to maintain sodium homeostasis Be able to describe the differences between snowy mountain rabbits and desert rabbits. Snowy
Mountain Rabbits (low sodium) Desert Rabbits (high sodium) • What are the two phases of energy utilization and storage after a meal? What occurs during each? What hormone promotes energy storage? How? After eating a meal, there are two phases of energy utilization and storage : 1. Postprandial 2. Postabsorptive • In a fasting state, what hormone promotes the release of stored energy? How? glucagon Eventually, blood concentrations of glucose drop and the body must shift from putting energy into storage into getting it out of storage • What endocrine gland releases the hormones involved in energy storage and release? Know the specific cell types. pancreas insulin: Glucagon Glucose and ketone bodies power the brain • Know the different causes of type I diabetes as well as the population most affected and treatments. Type I
• Know the different causes type II diabetes as well as the population most affected and treatments. Type II What is the main consequence of both types? What are the symptoms? Individuals with either type of diabetes have trouble moving surplus glucose out of the blood resulting in symptoms which include: • What is the "dual-center" hypothesis? Is it accurate? For many years "Dual-center" hypothesis though to be correct This hypothesis proved to be too simple to account for the regulation of feeding • What hormone that we discussed in class acts as an adiposity signal? In what brain region are receptors for this hormone found? leptin acts as an adiposity signal In the arcuate nucleus region, what are the two signaling molecules produced by the feeding stimulatory circuit? Feeding Stimulatory Circuit (Anabolic) produces two orexigenic peptides that stimulate food intake, reduce metabolism and promote weight gain: In the arcuate nucleus region, what are the two signaling molecules produced by the feeding inhibitory circuit? Feeding Inhibitory Circuit (Catabolic) produces two signaling molecules that inhibit food intake, increases metabolism and promotes weight loss: Where do these (feeding inhibitory and stimulatory) circuits project? Both circuits: send signals to PVN and LH which then directly modulate feeding behaviors NPY/AgRP circuit projects into the PVN What effect do high levels of leptin have on the stimulatory pathway and inhibitory pathway? What effect do low levels of this hormone have on the stimulatory pathway and inhibitory pathway? High leptin (high energy reserves) decreases feeding behavior by inhibiting NPY/AgRP neurons and stimulating POMC/CART neurons What happens when leptin levels are low (low energy reverses)? • What effect does ghrelin have on feeding? How? Ghrelin acts to stimulate feeding by activating AGRP/NPY neurons • What role does the nucleus of the solitary tract (NTS) play in hunger and satiety? What effect does cholecystokinin (CCK) have on food intake? NTS (nucleus of the solitary tract) in
brainstem receives and integrates appetite signals from a variety of sources in addition to the hypothalamus including: both anabolic and catabolic pathways feed into the NTS. Together these signals regulate food intake CCK decreases food intake (satiety signal) • Why do humans have a tendency to accumulate excess energy? Like it or not, our evolutionary history has optimized our bodies for obtaining and storing energy to enhance survival in environments where energy availability fluctuates What are some approaches being investigated to treat obesity or that are being used currently? -Increased metabolism: thyroid hormones (unwanted side effects i.e. high rate unless can activate TH-R associated with metabolism without affecting TH-R associated with cardiovascular function) Can leptin be used to treat obesity? Why or why not? Many obese people have abnormally HIGH levels of leptin because lots of adipose tissue. Which, if any, are effective? Anti-obesity surgery : • What are the key components of biological rhythms? Over what time scale(s) do biological rhythms vary? Biological rhythms are characterized by: Period of biological rhythms range from ms to years Different lengths of biological rhythms can occur in same measure • What are isolations experiments? What do they determine? isolation experiments determine whether a rhythm is the result of exogenous or endogenous factors If remove environmental cues and the biological rhythm: Be able to describe the experiment and findings of Jean Jacques d'Ortous de Mairan and why they were important. De Marian's experiment (1729) - Tension-relaxation pattern of heliotropic plants (move in response to sun) - Persist even if plants isolated from exogenous factors (i.e. sun) - Rhythm is ENDOGENOUS • What are 3 types of evidence that biological clocks are endogenous and not driven by the environment? Animals maintained in space (away from tides, light/dark cues, etc...) maintain biological rhythms similar to those observed on earth Animals maintained in adjacent, but individual, cages in the absence of environmental cues display biological rhythms with slightly different periods suggesting that are not being driven by the same geophysical cues Period and phase of biological rhythm of one individual can be 'transferred' to another by means of a tissue transplant (master biological clock) • What is a free running rhythm? What does it represent? What is entrainment? What is a zeitgeber? Entrainment: process of synchronizing a an endogenous biological rhythm to an environmental cue (zeitgeber or "time-giver") These rhythms persist when animals are isolated from their environmental cues but only approximately (free running
rhythms) • What are 4 types of biological rhythms that are synchronized with ENVIRONMENTAL cues? What are their entrained period lengths (i.e. when environmental cues are present)? What are their free-running period lengths (i.e. when animals are isolated from their respective environmental cues)? circadian: revolution of the earth (environmental
cycle), 24 hours entrained, 22-26 hours free-running • What is an important experimental technique used in the study of circadian rhythms in small mammals like hamsters? locomotion Newer set-ups use live-tracking to image when and where animals are active • What is an important environmental time cue for hamsters and most other species? Zeitgeber: light • If a hamster is housed in conditions where lights are off for 12 hours, then on for 12 hours, when will the hamster run? What happens if the environmental light-dark cycles are phase shifted (e.g. lights are turned off 4 hours later)? If the hamster is housed in constant dim light, what happens? What does this tell us about circadian rhythms? When housed in a light/dark cycle, animal becomes active during night Circadian rhythms are endogenous (self-sustained) but they are adjusted or entrained to the environment by external cues called zeitgebers, the primary one of which is daylight. • What happens to the sleep wake cycle of humans placed in a dark cave with no external cues? What does this suggest? Human subjects were placed voluntarily in a dark cave with all cues to external stimuli removed example of endogenous circatidal rhythms Locomotor activity pattern of fiddler crabs: If moved to aquarium, will retain cycle of activity and become active at approx. same time as low tide (12.4 hr tidal cycle) example of circalunar rhythms Antlion hunts by building pit to catch prey example of circannual rhythms. Migratory patterns of birds Even when kept in lab, birds show 10-12 month cycles of pre-migratory restlessness, weight gain and reproductive competence • What are two types of biological rhythms that persist in constant conditions and do not correspond to any known geophysical cues? How often do they occur? Be able to provide examples of each. Ultradian Infradian • What is the usefulness of biological clocks? Conductor of orchestra-makes sure everything timed appropriately Example: peak CORT occurs just prior to awakening --> increase blood pressure and cardiac output --> prepare you for onset of locomotor activity Conductor of orchestra-makes sure everything timed appropriately • What are the six general characteristics of biological clocks and rhythms? Inherited General characteristics of biological clocks - 1 When mutant animals with free-running circadian rhythms > 25 hr are mated with one another, their offspring tend to have longer free-running periods than the offspring of mutants with free-running rhythms < 23 hr (and vice versa) General characteristics of biological clocks - 2 Temperature independent Activities or events that change body temp don't significantly alter circadian clocks Otherwise there would be speed-ups and slowdowns and eventually all resemblance to a 24 hr period would be lost General characteristics of biological clocks - 3 If not, the food consumed would constantly be altering biological clocks A few pharmacological manipulations have been shown, however, to affect clocks: Protein synthesis inhibitors, Alcohol (EtOH), Lithium, Heavy water (deuterium) These interfere with processes like membrane permeability & protein synthesis needed for biological clocks to function General characteristics of biological clocks - 4 A circadian rhythm can be entrained to a 23 hr day by providing 11.5 hr of light and 11.5 hr of dark (same for 12.5 hr light/12.5 hr dark). However, 10 hr light and 10 hr dark does not result in entrainment to a 20 hr day. Instead, results in free-running with sporadic entrainment attained at irregular intervals. General characteristics of biological clocks - 5 Suppose a hamster
housed in DD is expressing a 24.25 h cycle of wheel running onset. General characteristics
of biological clocks -6 Single-celled organisms (i.e. algae) possess circadian rhythms...machinery necessary to generate a rhythm must exist at the level of individual cells. So, in multi-cellular organisms, does every cell possess its own biological clock? Perhaps, but in multi-cellular organisms, it appears as if these individual biological clocks have been organized into some sort of hierarchical fashion with feedback imposed from above. E.g., cells taken from hamster adrenals and maintained in culture will free-run at different rates. In the intact hamster, they free-run at the same rate. • Where is the master circadian clock found in amphibians, fish, reptiles and birds? Mammals? in amphibians, fish, reptiles, and birds, they have photoreceptors in the pineal gland. Suprachiasmatic
nucleus (SCN) Suprachiasmatic nucleus (SCN) ~10,000 cells per side In mammals, what is the evidence? 1) Greater activity in the SCN during the light phase (as measured using autoradiography for glucose usage) 4) SCN transplant studies using mutant tau hamster • How does the master clock work? Takes advantage of the time it takes to make and degrade proteins from mRNA In humans, "larks" versus "night owls" have different versions of the clock gene 1. Two proteins, clock and cycle, bind together to form a dimer • Be able to describe the major input and output pathways to and from the master clock in mammals. light information goes from the eye to the SCN via the retinohypothalamic pathway. The RHT consists of retinal ganglion cells that project to the SCN Most of these retinal ganglion cells contain the photopigment When the retinal ganglion cells of the RHT containing melanopsin detect light, they release glutamate in the SCN. Glutamate leads to increased transcription of per gene entraining the molecular clock to the day-night cycle Because biological rhythms are so pervasive, there are probably hundreds of SCN outputs. 1) PVN: regulates rhythms in most endocrine function 2) Pineal gland (indirect pathway): regulates sleep/wake rhythm eye --> RHT --> SCN --> MFB --> RF --> SCG --> pineal gland Neural circuitry to and from the SCN in mammals Because biological rhythms are so pervasive, there are probably hundreds of SCN outputs. 1) PVN: regulates rhythms in most endocrine function eye --> RHT --> SCN --> MFB --> RF --> SCG --> pineal gland • How is the clock entrained by external cues? Circadian rhythms entrain to light-dark cycles using different pathways, some outside of the eye Amphibians and birds have photoreceptors in the brain and pineal gland • Where is melatonin secreted from? When is it secreted? Is the duration of secretion important? What information does this provide an animal? Pineal gland releases melatonin Production inhibited by light coming in via RHT Hormone of darkness because secreted almost exclusively at night (peaks at 4 am) Melatonin tells the body it is dark and thus plays a role in sleep onset The duration of secretion is important because when the days are long and the nights are short, there are less melatonin secretions,and when nights are longer there is more melatonin secretion. Seasonal species like hamsters can use this as a way to time seasonal cyles and their behaviors associated with those cycles. Syberian hamsters, when the days are short , they don't reproduce, their coat changes, don't mate, all by measuring melatonin secretions. • What is photoperiodism? Melatonin
plays a role in photoperiodism: • Describe the seasonal cycle of reproduction in hamsters. How can seasons be mimicked in the lab? What is the critical day length for reproduction? In the fall: wild Siberian hamsters suppress their reproductive systems and develop winter coat for camoflage in the snow Keeping day length at 12.5 hr and maintain testis size If day lengths held at short days in the lab (less than 12.5 hr), testes will regress When day length reaches threshold, indicated by melatonin, abrupt change in reproductive status How is the seasonal cycle of reproduction regulated? In autumn --> short days (increased melatonin): • What are some examples of non-reproductive seasonal changes? In wild voles, brain weights and hippocampal mass higher in summer What evidence exists showing the hormones directly impact aggressive behavior?What evidence exists showing that hormones directly impact aggressive behavior? In controlled experiments, men who were randomly assigned to be castrated at birth show lower levels of aggression in adulthood than men who were not randomly assigned to be castrated.
Do hormones influence behavior?Generally speaking, hormones change gene expression or cellular function, and affect behavior by increasing the likelihood that specific behaviors occur in the presence of precise stimuli. Hormones achieve this by affecting individuals' sensory systems, central integrators, and/or peripherial effectors.
How is most of the research investigating the causal impact of hormones on behavior conducted quizlet?How is most of the research investigating the causal impact of hormones on behavior conducted? By performing experiments on non-human animals.
What is the scientific study of the interaction between hormones and behavior called answer choices?This field of study is also called behavioral endocrinology, which is the scientific study of the interaction between hormones and behavior.
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What evidence exists showing that maternal behavior is mediated by hormones quizlet?
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