h&h exam 1- lecture 1b hypothalamus & pituitary gland

How much does the pituitary gland weigh

600mg

where is the pituitary gland located

within the sella turcica (turkish saddle)

Are the hypothalamus and pituitary gland located within the blood brain barrier? Why

No! because it needs access to blood so it can release hormones into the bloodstream

label (top two, middle, bottom 3)

top: optic chiasm, hypothalamus
middle: pituitary stalk
bottom: pituitary gland: anterior lobe (left) and posterior lobe (right)

label: top 3 (top to bottom) (last one has description of function as well)

neurons synthesizing posterior pituitary hormones, hypothalamus, neurons synthesizing trophic hormones release them into capillaries of the portal system

label left two (bottom one has description of function as well)

capillary beds, endocrine cells release their hormones into the second set of capillaries for distribution to the rest of the body

label right column bottom 5 (top to bottom) (2nd has description of function as well)

artery, portal vessels carry the trophic hormones directly to the anterior pituitary, terminals of hypothalamic neurons, posterior pituitary, anterior pituitary

portal circulation description

passage of blood by a vein from one to a second capillary bed

Label the red, left column

optic chiasma, portal vein, anterior lobe

Label the red, right column

hypothalamic nuclei, mamilary body (gray matter of the brain), pituitary stalk, posterior lobe

most basic functions of the anterior and posterior pituitary

anterior pituitary: portal system
posterior pituitary: neurosecretion

basic differences between anterior and posterior pituitary (3)

anterior: endocrine cells, contains capillary bed, portal system
posterior: no endocrine cells but has nerve endings from the hypothalamus, neurosecretion

Hypothalamus releasing hormones → anterior pituitary examples (6)

GHRH - GH
Dopamine - Inhibiting release of PRL (prolactin)
Somatostatin - Inhibiting release of GH
Thyrotropin-RH (TRH) - TSH (Thyroid Stimulating Hormone)
Corticotropin-RH (CRH) - ACTH
Gonadotropin-RH (GnRH) - 1) LH (Luteinizing Hormone), 2) FSH (Follicle Stimulating Hormone)

Hypothalamus (hormones released in) → posterior pituitary examples (2)

AVP (cell bodies) - ADH
SO (cell bodies) - oxytocin

somatostatin description

somatotropin release inhibiting factor

Anterior pituitary important point regarding the amount of blood that is there

the amount of blood is really small (only a few capillaries) so even a few hormones can have effects on a local level, can easier change concentrations with smaller amounts of molecules

what is this an example of

simple feedback loop

What is this an example of?

Hierarchical control

label

long-loop feedback, short-loop feedback

HPA axis simple (8 steps) (things in brackets are hormones that are released by the preceeding structure)

cerebral cortex - hypothalamus - (CRH) - ant. pituitary - (ACTH) - adrenal cortex - (cortisol) - target tissue

What is the HPA axis an example of?

Hierarchical control

HPA axis long

hypothalamo-pituitary-adrenal axis

primary function of HPA axis

regulate the stress response

CRH long

corticotropin releasing hormone

ACTH long

adrenocorticotropic hormone

Cortisol effects on the HPA axis

short loop feedback: on the anterior pituitary releasing ACTH
long loop feedback: on the hypothalamus releasing CRH

Relation between ACTH and cortisol secretion

they have an episodic, pulastile pattern, ACTH normally increases first and then cortisol follows, except around 5am where cortisol peaks before ACTH (getting ready to wake up)

Hormones of the neurohypophysis & their actions (2)

vasopressin (effect on the kidney, effect on fluid maintenance, thirst)
oxytocin (love and bonding)

deficiencies of vasopressin secretion and action

diabetes insipidus, adipsic hypernatremia

adipsia meaning

absence of thirst

excess vasopressin secretion and action

hyponatremia

What is the neurohopophysis

posterior pituitary gland

Posterior pituitary description

axons originate in the hypothalamus, peptide hormones released by exocytosis in the posterior pituitary into the blood stream

Similarities between ADH and oxytocin

both contain 9 amino acids

actions of oxytocin (5)

uterine myometrium contraction (final stages of pregnancy) (cause of onset of labour is debated), suckling (milk ejection), maternal behaviour, possible: sexual and mating behaviour, oxytocin as a neurotransmitter

social-psychological effects of oxytocin (8)

trust (contested), sexual arousal, receptor polymorphism (sociopaths, etc), reduced function linked to autism, romantic attachment/mate bonding, improved memory for faces, empathy, dog’s attachment to humans

Dogs attachment to humans and oxytocin

after long petting session concentration of oxytocin in cerebro spinal fluid (CSF) of dog and human rose significantly

Trust and oxytocin

when administered nasally, subjects displayed “highest level of trust” twice as often as controlled (contested though)

oxytocin and romantic attachement (3)

positive correlation between oxytocin plasma levels and self-perceived romantic attachment; in praire vole - oxytocin administered in the CNS increases monogamy; reduces incidence of infanticidal behavior in animals

oxytocin and autism (2)

correlation between some forms of autism and deletion of oxytocin receptor gene; people with some forms of autism fail to produce oxytocin, nasally administered oxytocin decreased some of the symptoms

oxytocin and social behaviour and empathy (4)

administered intranasal oxytocin induces improved memory for (happy) human faces, increased empathy, improved recognition for +ve social cues over threatening social cues, increased generosity

MDMA and oxytocin

100mg of MDMA increased oxytocin levels significantly in humans, activation of serotonin 5-HT1A receptors → secretion of oxytocin

oxytocin and sexual stimulation

plasma levels of oxytocin rise during sexual stimulation up to orgasm

Pheromones in humans

testosterone derivative (AND) activates the hypothalamus in females but not in males, estrogen-like compound (EST) did the opposite