The brain as an endocrine organ

Question 1

Monogamy and polygyny species features

Answer 1

M:
[Dik dik}
Males and females share resources
No weapons for the intrasexual conflict
Dimorphic behaviour minimal
Both sexes share care/defence of common family territory

P:
[Elephant seals]
Intense male: male competition for females
Evolution of weapons
Dimorphic behaviour driven by sex steroids
Abandonment of parental care by male

Question 2

Increased [ ] and [ ] from monogamy to polygyny

Answer 2

Sexual dimorphism
Androgenic action/ exposure to androgens

Question 3

Reproductive costs

Answer 3

Evolution of preg and lactation = Reproductive costs largely female borne
Males = less opportunity to share energy costs of rearing offspring opening up selective forces for polygynous behaviour
M - more common in birds (males feeding females for quality eggs)
P - mammalian

Question 4

What has lead to dimorphic behaviour, growth and physiology

Answer 4

Difference in reproductive costs = different reproductive strategies
Intense male-male competition for access to females (limiting resource)

Question 5

Define sexual dimorphism

What is it driven by

Answer 5

Distinct difference in size or appearance between the sexes of an animal in addition to the sexual organs themselves

Sexual selection

Question 6

Sexual selection

Answer 6

Depends on the success of certain indivudals over others of the same sex
[Darwin]

Question 7

Aristotle

Answer 7

Effects of castration 2000 years ago
Organ in animal mutilated animal passes from male to female form.
The castration is considered as a sexual inversion and, since only the emasculation (animal or human) seems to hold attention of the philosopher, it means feminization

Question 8

Have the hypothalamus and forebrain undergone different evolutionary history?

Answer 8

H - develops in early embryonic life
YES
Scaling of size of forebrain to body disproportionate
H - scales linearly to body size (same relative size)

Question 9

Hypothalamus

Answer 9

Fluid filled ventricle lined by neuronal structures regionally defined
Different regions and different circuits that drive hormonal and behavioural circuitry

Question 10

Hypothalamic-portal blood system

Answer 10

Blood supply from hypothalamus forms a plexus transmit the blood down into the AP
Axons of the hypothalamus release signal into portal blood supply carrying hormonal signal down to main pituitary gland
Different populations of cells involved in the control of different processes

Question 11

GnRH

Answer 11

Gonadotrophin releasing hormone

Decapeptide
Released by preoptic nucleus in hypothalamus
Stimulates Gonadotrophic cells in AP
Stimulates release of LH and FSH
Information in endocrine encoded through frequency (pulses)
Pulsatile action controlled by interneurons with direct connections with cell body of GnRH neurones [few cell types]
Modulation by environment and regulation of puberty control of male-female difference
High frequency = LH release
Low frequency = FSH release

Each GnRH pulse elicits an LH pulse
LH acts on Gonads

Question 12

Decapeptide

Answer 12

Released by specialised neurones in hypothalamus
Very potent
Mutation = can be sterile (no capacity to produce reproductive response)

Question 13

Posterior pituitary gland

Answer 13

Neurons transmit signal into the main body of pp then picked up by vascular system to the rest of the body
Magnocellular neurones (very big) produce hormonal signals including oxytocin

Question 14

Secretion of oxytocin and Vasopressin

Answer 14

Direct action on brain behaviour
Vascular system and carried to organs

Question 15

Two-way pathway

Answer 15

As well as into the AP and PP neurones in hypothalamus transmit directly to other structures of the brain

Question 16

Gonads

Answer 16

Produce sex steroids
- Act locally to regulate gonadal behaviour
- Act on body to differentiate development and physiology
-Act on brain to regulate behaviour

Question 17

Behavioural and physiological function are?

Answer 17

Interlocked and clearly have co-eveloved