BMS1052 Lecture Notes - Lecture 20: Homeostasis, Leptin, Amylin
30 May 2018
School
Department
Course
Professor
Week 9. Hypothalamus
HYPOTHALAMIC PITUITARY AXIS
• Functions of the Hypothalamus:
Functions
Important regions
o Control of metabolism
o Mediation of stress
o Control of reproductive behaviour and
growth
o Control of body temperature
o Integration of autonomic and endocrine
functions
o Secretes hormones directly from the brain
into the blood stream and as such can
influence functions (body temp, growth etc)
-> compares changes of environment to set
point to make appropriate adjustments
o Thin sheet of tissue in the human,
approximately 3-4mm on either side of the
third cerebra ventricle
o Compromised BBB in its ventro-medial part
• Hypothalamus and the pituitary:
o Hypothalamus is connected to the pituitary gland by a stalk comprised of nerve fibres
and portal vessels – the infundibulum
o Pituitary gland is divided into anterior and posterior parts
o Median eminence has leaky BBB
• Anterior pituitary gland function:
find more resources at oneclass.com
find more resources at oneclass.com
o Big controller of other glands
o Parvocellular neurosecretory cells from the paraventricular nucleus produces neuro-
hormones that are released into portal vessels in median eminence cells -> cause release
of hormones from specialised secretory cells
o Portal vessel = fed by own blood supply
o Different anterior pituitary cell types:
Hormone
Cell type
Target/function
Follicle stimulating
hormone/luteinising hormone
Gonadotrophs
Gonads/reproduction
Thyroid stimulating hormone
Thyrotrophs
Thyroid/development and
energy expenditure
Adrenocorticotropic hormone
Corticotrophs
Adrenal/stress
Growth hormone
Somatotrophs
Widespread anabolic actions
o Mediation of stress: pathways of stress hormones- an example of anterior pituitary
function
Detected in the brain and leads to release of corticotropin releasing hormone
(CRH) from nerve fibres originating from neurons in the paraventricular nucleus
CRH is transported via portal system to anterior pituitary where it acts on
corticotrophs that release adrenocorticotropic hormone (ACTH)
Adrenal gland cortex releases cortisol -> acts throughout body to mobilise
energy stores and suppresses the immune system
More likely to undergo infections
Also feedbacks onto hypothalamus to inhibit ongoing cycle
o Control of reproductive behaviour: control of sex hormones by hypothalamus and
pituitary
GnRH is produced in neurons of preoptic area of hypothalamus -> uner feedback
control of number of hormones
GnRH is released into portal system to act on gonadotrophs causing release of
FSH and LH which act on both ovaries and testes
-> males: testosterone and sperm
-> females: estrogen and release of LH and FSH menstrual cycle
find more resources at oneclass.com
find more resources at oneclass.com
• Posterior pituitary function:
o Control of vasopressin and oxytocin release produced in magnocellular neurons
o Vasopressin aka ADH
Acts predominantly on kidneys
Do’t ed up i edia eiee/portal syste
Projects straight through eminence and end around blood vessels in posterior
pituitary
o Dehydration:
Changes in tonicity -> detected by OVLT -> senses dehydration -> activates ADH
-> prevents further production of urine
o Haemorrhage:
Reduction in blood volume -> acts on vasopressin neurons -> decrease urine
output
o Suckling:
Oxytocin in blood -> release milk in response to suckling
-can also have emotional reflex eg. baby crying may trigger release of milk
o Role of oxytocin:
Love: eg. Prairie vole is monogamous -> oxytocin and vasopressin is released
during mating -> if blocked, sex becomes a fleeting affair (no longer
monogamous)
Oxytocin in female during sex is important for forming monogamous pair bond,
vasopressin has similar effect in males
Oxytocin and vasopressin activates reward pathways in the brain which releases
dopamine
Released in large amounts during labour and after suckling
Roles in orgasm, social recognition, bonding?
May raise trust in strangers? (nasal spray of oxytocin)
Higher concentrations in people claiming to be in love
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Hypothalamic pituitary axis: functions of the hypothalamus: Functions: control of metabolism, mediation of stress, control of reproductive behaviour and growth, control of body temperature. Integration of autonomic and endocrine functions: secretes hormones directly from the brain into the blood stream and as such can influence functions (body temp, growth etc) > compares changes of environment to set point to make appropriate adjustments: hypothalamus and the pituitary: Widespread anabolic actions: mediation of stress: pathways of stress hormones- an example of anterior pituitary function. Detected in the brain and leads to release of corticotropin releasing hormone (crh) from nerve fibres originating from neurons in the paraventricular nucleus. Crh is transported via portal system to anterior pituitary where it acts on corticotrophs that release adrenocorticotropic hormone (acth) Adrenal gland cortex releases cortisol -> acts throughout body to mobilise energy stores and suppresses the immune system.
