Lecture 5- Hormones and behaviour part I: definitions and processes

Question 1

what is a hormone

Answer 1

chemical messenger released into the bloodstream, or a tissue fluid system, which affects the function of target cells some distance from the source

Question 2

3 classes of hormone

Answer 2

amine-derived- e.g. adrenaline, thyroxine
peptide- e.g. leptin, LH
lipid/phospholipid derived- androgens, oestrogen

Question 3

5 different types of mediation (probs dont need to know all of these)

Answer 3

○ Intracrine mediation- regulation of intracellular events
○ Autocrine mediation- substances feeding back to influence the same cells which secreted them
○ Paracrine mediation- secreting chemicals which affect adjacent cells
○ Endocrine mediation- chemicals secreted into the bloodstream, can travel to distant target cells
Ectocrine regulation- release into the environment by individuals to communicate with others

Question 4

3 classes of vertebrate ‘brain hormones’

Answer 4

hypothalamic- ‘releasing hormones’ which control regulation of other hormones in other parts of the body
pituitary- regulation of thyroid/adrenal/etc hormones, also oxytocin, prolactin
pineal gland- melatonin etc, helps regulate circadian rhythm

Question 5

connection between eyes and pineal gland

Answer 5

photoreceptor cells in non-mammalian vertebrates are related to pineal cells in mammals, in birds they have both functions

Question 6

some examples of gland hormones

Answer 6

thyroid/parathyroid
pancreatic
adrenal
gonadal

Question 7

homeostasis- important points

Answer 7

-definition, bringing internal state to an optimum
-positive vs negative fb
-example- can be more complex e.g. gonadotropin-releasing hormone leading to testosterone production

Question 8

factors which can affect hormone production (theres 7, but dont need them all)

Answer 8

○ 1) Age Juvenile vs adult
○ 2) Genetic sex - male, female, hermaphrodite
○ 3) Metabolic/emotional state - hungry, thirsty, tired, afraid
○ 4) Behaviour/experience - winning/losing, escape, social interaction
○ 5) Environment - Social group, temperature
○ 6) Biological/circadian rhythm - time of year, time of day
7) Reproductive state - pregnant, nursing, in heat

Question 9

example of how hormones can affect metabolism

Answer 9

thyroxin- lower levels leads to lower metabolic rate

Question 10

how hormones can lead to sex-specific traits

Answer 10

birds- high estrogen = duller plumage

Question 11

what gets light to the pineal gland in mammals

Answer 11

retinohypothalamic tract into the brain, then through structures towards the pineal gland where serotonin is triggered to be converted into melatonin at night

Question 12

important signalling structure after the retinohypothalamic tract

Answer 12

suprachiasmic nucleus- issues with this alter the circadian rhythm, and replacing it brings back the 24h cycle

Question 13

how do hunger circuits fit into this sleep circuit

Answer 13

prevention of hunger when sleeping, signals integrated along with others in the hypothalamus

Question 14

what is a ‘motivation state’

Answer 14

sum of all biological, social, cognitive forces which activate a behaviour, e.g. physiological need to maintain nutritional homeostasis, external feedback with safety etc

Question 15

example of how internal state can regulate behaviour

Answer 15

dust bathing in chickens, do it more when they have access to sand and when they haven’t done it in a while- increase in motivation over time

Question 16

example of breeding in guppies

Answer 16

males seem to take ‘interest’ in larger females, but older males with specific markings are more likely to court smaller females
time also affects motivation here- longer time since last breeding > more motivation