Endocrine System Flashcards

Question

Different forms of hormone function

Answer 1

Concerted/ Additive Non-additive Synergistic Permissive Consider two hormones A & B. For concerted or additive effects the individual effects of A & B are just combined. For non-additive effect B has no really effect on the effect of A, whereas for synergistic effects the combined effect of A&B is greater than the sum of A & B. For permissive effects hormone A has an effect but B does not but when A is in the presence of B the effect is magnified.

Answer 2

Located above kidneys different hormones are produced by different parts of the gland The cortex is multi-layered and each layer produces different hormone types Zona reticularis – androgen steroids Zona fasciculata – glucocorticoids, e.g. cortisol – mediates stress response Zona glomerulosa – aldosterone – regulates Na+ and K + in kidney The medulla produces the catecholamines epinephrine and norepinepherine

Answer 3

Androgen steroids

Answer 4

Insulin is produced within the endoplasmic reticulum and Golgi apparatus Vesicles containing the hormone bud off the Golgi and can act as a store Release to the blood stream is via exocytosis

Answer 5

synthesised on demand and released via diffusion across the plasma-lemma

Answer 6

many hormones are produced by neurosecretory cells in the brain but there are also endocrine glands such as the prothoracic gland that produces ecdysone

Answer 7

Glucocorticoids eg cortisol

Answer 8

Aldosterone

Answer 9

Catecholamines Epinephrine Norepinephrine

Answer 10

The pineal gland, conarium, or epiphysis cerebri, is a small endocrine gland in the brain of most vertebrates. Associated with exposure to light produces melatonin, a serotonin-derived hormone which modulates sleep patterns in both circadian and seasonal cycles. It is likely that the common ancestor of all vertebrates had a pair of photo-sensory organs on the top of its head, similar to the arrangement in modern lampreys, and many lizards

Answer 11

produced by one animal - released outside the body into the environment - received by other animal/s typically by their sense of smell Evolved to enable communication between members of the same species Pheromone signalling elicits a specific reaction in the receiver: stereotyped behaviour developmental process Not all smells are pheromones

Answer 12

2 or more hormones controlling the same thing

Answer 13

Thyrotropin-releasing hormone (TRH) is secreted by the hypothalamus in the brain, which stimulates production of thyrotropin-stimulating hormones (TSH) from the nearby pituitary gland. This is released into the blood and travels to the thyroid glands where T3 and T4 are produced in response. These hormones act on tissue metabolism and feedback via the blood on the hypothalamus and the pituitary to reduce TRH and TSH secretion.

Answer 14

Certain hormones can ‘self prime’ own production - gland makes even more hormone e.g. oxytocin and control of suckling

Answer 15

The act of suckling triggers nerves in the nipple which trigger milk production by lactocytes in the breast and oxytocin release in the hypothalamus and posterior pituitary. The oxytocin then stimulates myoepithelial cells lining the ducts of the milk glands to push the milk to the nipple. This release of milk encourages suckling and so increases production of milk and oxytocin.

Answer 16

Feeding Fleeing Securing a mate Reproducing

Answer 17

Hypothalamus Pituitary Gonads

Answer 18

Environmental factors interact with hormones to stimulate secretion of hormones such as gonadotropin-releasing hormones and gonadotropin-inhibiting hormones, which interact with the pituitary to stimulate (or inhibit) secretion of luteinising hormones and follicle stimulating hormone. These are produced in both males and females alike. These travel via the blood to interact with the gonads (testis and ovary) where they stimulate sex steroids – male androgens and female oestrogens. Vasoactive intestinal protein is secreted in the hypothalamus and promotes secretion of prolactin. Arginine vasotocin (AVT) has direct actions on factors such as oviposition in birds.

Answer 19

Testosterone Androstenedione

Answer 20

Progesterone Oestrone Oestrodiol 17(beta)

Answer 21

Mate searching Courtship Copulation Parental care

Answer 22

Japanese red-bellied newt (Cynops pyrrhogaster) 7α-Hydroxypregnenolone produced by neurones in parts of the brain stimulates locomotor activity during mate searching

Answer 23

Plasma androgens activate calling behaviour and increase in response to calling Increased calling effort leads to higher energetic demands and rise in plasma corticosterone Plasma corticosterone reaches threshold and inhibits androgen secretion by negative feedback on the hypothalamic-gonadal axis Plasma androgen levels drop and calling decreases allowing males to increase energy stores Restored energy stores cause corticosterone levels to drop and androgen levels increase and calling begins again

Answer 24

Movement of females attracted to calling males

Answer 25

Prolactin is formed in the pars distalis of the pituitary and is under the control of vasoactive intestinal protein (VIP) produced in endocrine neurons in the hypothalamus

Answer 26

stimulates the mammary glands to produce milk (lactation): increased serum concentrations of prolactin during pregnancy cause enlargement of the mammary glands and prepare for milk production, which normally starts when levels of progesterone fall by the end of pregnancy and a suckling stimulus is present.

Answer 27

implicated in migration behaviour, reproductive development and attainment of sexual maturity, steroidogenesis and gonadogenesis, and brood care behaviour Mouth brooding Nest building Egg fanning Pit-digging behaviour Nest guarding and defence Guarding of schooling fry ‘Pregnancy’ Nutrient provision to offspring

Answer 28

Several lineages of fish incubate eggs and larvae in their oral cavity (mouth brooding). In cichlids a combination of PRL and oestrogen promotes oral egg carrying behaviours Pituitary tiPRL177 concentrations increase in female Mozambique tilapia brooding eggs or early stage embryos Serum concentrations of tiPRL177 also increasing in females brooding late-stage larvae

Answer 29

Japanese red-bellied newt Prolactin released in response to cold temperature Prolactin is important in the physiological transition of salamanders from a terrestrial refugia to the aquatic habitat of the breeding pond Prolactin is important in courtship behaviour Injected anti-newt prolactin receptor antibody decreased the incidence and frequency of courtship tail-fanning behaviours

Answer 30

Stimulates maternal behaviours Prolactin levels are only elevated in the males that are group-living and breeding (black bar) and the females (white bar in graph). Outside of the breeding season males and females exhibit no differences in prolactin levels (right graph).

Answer 31

Wild groups of cooperatively breeding meerkats, male helpers that decided to babysit had significantly higher levels of prolactin, coupled with lower levels of cortisol, before initiating a babysitting session compared with similarly aged individuals that decided to forage. Hormonal differences disappeared over the course of the day, suggesting that hormone levels changed in a fundamentally different way in meerkats that babysat versus those that foraged. In contrast, long-term contributions to babysitting were not significantly associated with plasma levels of prolactin, cortisol, or testosterone in individual male helpers.

Answer 32

Long-term contributions to pup provisioning were significantly and positively correlated with plasma levels of cortisol rather than prolactin, while plasma levels of testosterone were not related to individual patterns of pup-feeding.. A playback experiment used pup begging calls to increase the feeding rates of male helpers gave rise to parallel increases in plasma cortisol levels, whilst prolactin and testosterone levels remained unchanged.

Answer 33

Bird lay eggs that require contact incubation to raise temperature to promote embryonic development through to hatching Reproductive behaviours involve incubation of the eggs and subsequent care of chicks Gonadotropin Releasing Hormone and Luteinising Hormone, and sex steroids all implicated in courtship and nest-building Female ring doves (Streptopelia risoria) require oestrogen and progesterone for nest building and incubation Males require testosterone to show nest-building behaviour

Answer 34

Prolactin levels are high during incubation and chick rearing Both male and female Adelie penguin (Pygoscelus adeilie) show rise in Prolactin during courtship Prolactin secretion stimulates incubation behaviour but incubation behaviour is stimulated by prolactin secretion Difficult to tease apart cause and effect

Answer 35

Pigeons and doves differ from other birds Prolactin not usually elevated until incubation is well established Oestrogen and progesterone seem to act synergistically to initiate incubation behaviour, which is then maintained by prolactin secretion Ring doves removed a nest but injected with prolactin maintain nest attachment and incubation drive but controls don’t In chickens chemical suppression of prolactin secretion limits broody behaviour Inhibition of AVT secretion in turkeys prevents incubation behaviour

Answer 36

Vasoactive Intestinal Protein and Dopamine produced in the brain express antagonistic roles in stimulating prolactin release from the pituitary The brood patch is typically characterised as being an area of featherless, swollen skin, rich in blood vessels on the ventral side of the thorax and abdomen. Good evidence of feedback loop between brood patch and prolactin secretion Denervation of the brood patch leads to drop in prolactin levels and loss of incubation behaviour

Answer 37

typically characterised as being an area of featherless, swollen skin, rich in blood vessels on the ventral side of the thorax and abdomen.

Answer 38

Post-hatching parental care seems to be regulated by prolactin – high correlation between level of parental care and prolactin Varies from independent precocial species to highly dependent altricial species Prolactin levels fall by ~50% at hatching but persist during rearing if the chicks require considerable parental care Patterns are variable according to individual species life histories – seabirds that spend a lot of time out to sea have persistence of prolactin

Answer 39

stosterone is high during courtship and mating but there is a dramatic decline when the eggs are laid in species where males contribute to parental care Challenge hypothesis…. Low levels of testosterone promote courtship and gonadal development but high levels promote aggression Drop in testosterone leads to improved fitness as aggression can be in conflict with parental care Supplementation with androgens decreases or disrupts parental care – promotes other behaviours that conflict with parental care

Answer 40

Peptide hormone released from endocrine glands in mucosal lining of stomach and upper intestines Key role in stimulating hunger Stomach empty – ghrelin secreted. Stomach stretched – secretion stops.

Answer 41

Acts on hypothalamic cells both to increase hunger, and to increase gastric acid secretion and gastrointestinal motility to prepare the body for food intake Loss of weight affects magnitude of ghrelin signal so increases secretion in advance of a meal Adjusts both energy input (hunger signals) and energy output – by adjusting the allocation of energy to usage or storage

Answer 42

Stretching of the stomach wall leads to secretion of peptides and neuronal signally with the vagus nerve CCK Peptide YY Glucagon-like peptide-1 (GIP) Glucagon Amylin

Answer 43

Polypeptide hormone produced by white adipose tissue Secretion is in proportion of stored fat in the body – ‘adiposity signal’ of body reserves Peptide YY secreted for a long time after meal and so suppresses appetite Receptor for ghrelin, the ghrelin/growth hormone secretagogue receptor (GHS-R), is found on same cells in the brain as the receptor for leptin

Answer 44

In response to acute stress, the body's sympathetic nervous system is activated due to the sudden release of hormones. The sympathetic nervous system stimulates the adrenal glands triggering the release of catecholamines, which include epinephrine and norepinephrine (adrenaline and noradrenaline) This results in an increase in heart rate, blood pressure, and breathing rate After the threat is gone, it takes between 20 to 60 minutes for the body to return to its pre-arousal levels

Answer 45

to kill for food, to defend offspring, to win a mate, to scare off a potential adversary

Answer 46

to kill for food, involves attacks against a member of a different species for the purpose of obtaining food; NOT associated with high levels of activity in the sympathetic division of the ANS;

Answer 47

for show, involves vocalisation and threatening or defensive posture high levels of activity in the sympathetic division.

Answer 48

regulated by androgens, and that aggression itself can modulate androgen levels, is well established in males. This response has been interpreted as a mechanism for adjusting aggressive motivation to a changing social environment. Adaptive to anticipate social challenges and reacting to their clues with an anticipatory androgen response to adjust agonistic motivation to an imminent social challenge.

Answer 49

Some evidence for gonadotropins influencing social aggression Postneonatal gonadectomy removes major source of sex steroids – suppresses aggression in a range of vertebrates Therapy with aromatisable androgens (testosterone) increases aggression in gonadectomised individuals Therapy with oestrogens – increases aggression in gonadectomised individuals but suppresses aggression in intact individuals

Answer 50

The "challenge" hypothesis asserts that testosterone and aggression correlate only during periods of heightened interactions between males. Under more stable social conditions relationships among males are maintained by other factors (e.g. social inertia, individual recognition of status, and territorial boundaries) and testosterone levels remain low. Testosterone is produced by the gonads and is transported to the brain – influences expression of reproductive behaviours

Answer 51

Correlations between levels of testosterone and aggression are convincing in birds but social context and environmental influences must be taken into account If testosterone is associated with territorial aggression then blood levels should parallel behaviour Free-living, monogamous species Testosterone is highest when territories are first established and aggressive interactions between males are highest – declines thereafter Nest site availability often drives competition – if low then testosterone is reduced

Answer 52

Males spend longer periods of time defending territories so testosterone is elevated when territories are first established but are maintained for longer Pied flycatchers have both monogamous (grey) and polygynous (blue) males and exhibit both patterns Brood parasite cowbirds defend females rather than territories

Answer 53

Testosterone is highest when territories are first established and aggressive interactions between males are highest – declines thereafter Nest site availability often drives competition – if low then testosterone is reduced

Answer 54

Males gain from polygyny, whereas monogamy increases female fitness. Cost of polygyny to females lead to intense female–female competition Physiological regulation of such female aggression in starlings is not yet known.

Answer 55

Environmental cues… Light, territory or signals from rival male Increasing day length stimulates Luteinising Hormone (LH) release from the pituitary, which stimulates testosterone secretion from the gonads High circulating levels of testosterone are not required for expression of sexual behaviour Free-living males – high testosterone is associated with aggression

Answer 56

Visual, auditory, tactile(??) or chemical (??) Males exposed to only a song playback (auditory only) or to a devocalised male (visual only), do not exhibit rise in hormone levels Both cues required and it is species-specific Are there hormone specific receptors on the neurons that allow for rapid effects? Organisational effect – affects song control nuclei in brain Immediate aggressive behaviour is not associated with a rapid peak in Testosterone