APP hypothalamus Flashcards
Name the nuclei and their functions
- Suprachiasmatic nucleus (biological clock, input from light-sensitive retinal ganglion cells).
- Anterior hypothalamus (thermoregulation). Fever
- Posterior hypothalamic area (sympathetic) - fear and aggression.
- Supraoptic/paraventricular nucleus (posterior pituitary secretion oxytocin & Anti-diuretic hormone).
- Median eminence/arcuate nucleus/paraventricular nucleus (control of appetite, metabolic rate, anterior pituitary).
- Ventromedial nucleus (satiety ‘centre’).
- Lateral hypothalamus (hunger ‘centre’); Orexin-hypocretin.
- Mammillary body (memory); Korsakov syndrome
Afferents
From sensory receptors, visceral (via reticular formation and solitary tract);
from brainstem (locus coeruleus, raphe, periaqueductal grey);
higher centres (hippocampal formation, amygdala, orbitofrontal cortex via mediodorsal thalamus).
Efferents
Endocrine control via posterior pituitary, and anterior pituitary via portal system;
descending control of autonomic centres in brainstem and
spinal cord;
mammillothalamic tract
Blood supply of hypothalamus
- from the internal carotid → gives superior and interior hypophyseal arteries
- inferior = posterior pituitary directly
- superior = hypothalamus including the CAPILLARY PLEXUS IN THE MEDIAN EMINENCE from which port veins pass to the anterior pituitary
Death of neurons in which nuclei would lead to diabetes insipidus?
SO/PVN
Broadly speaking, what does the hypothalamus have roles in?
Homeostasis Rhythms Development (e.g. puberty) Metabolism Control of the autonomic nervous system Endocrine system control
What does the hypothalamus secrete to control the anterior pituitary?
Releasing hormones: GnRH GHRH TRH CRH
Inhibiting factors:
DA
Somatostatin
Which two releasing hormones are released from the paraventricular nucleus (also doing OXY and ADH)?
CRH and TRH
Which releasing hormone comes from the anterior HT?
Somatostatin
How do cells in the SO and PVN know that blood osmolarity has changed?
Osmosensitive neurons - osmosensitive neurons in the OVLT, SFO and NTS project directly to SO and PVN
They are sensitive as shrinking + swelling can cause changes in stretch in gated ion channels
Candidate ion channels TRPV1 (hypertonic stimulus), TRPV4 (opens in response to hypotonic stimulus)
Give the pathway leading to ADH release
Increased blood osmolarity → OVLT neuron shrinking → TRPV1 open and APs → make connections with SO nuclei → promotes ADH release
What does FSH do?
Males - sperm production
Females - follicle ovum maturation
What does LH do?
Males - testosterone secretion
Females - ovulation
What does GH do?
Growth of tissue and secretion of IGF-1
What does TSH do?
Secretion of thyroid hormones which regulate base metabolic rate
What does ACTH do?
Secretion of glucocorticoids, mainly cortisol, and production of androgens
What does PRL do?
Milk production in females
What inhibits PRL release?
DA
Describe the negative feedback loops within the hypothalamus
Give an example
The ultra-short feedback loop is mediated by the hypothalamic releasing factors limiting their own release by a type of autocrine effect on targets in the hypothalamus.
Inhibition of releasing-factor secretion by pituitary hormones comprises short loop feedback.
Finally, peripheral hormone inhibition of pituitary secretion comprises the direct long-loop feedback and inhibition on hypothalamic secretion of the releasing factors comprises the indirect long-loop feedback.
The regulation of GHRH release by somatostatin is an example of ultra-short loop feedback, regulation of release by GH is an example of short-loop feedback, and regulation by IGF is an example of indirect long loop feedback.
Describe release and role of oxytocin
release: stimulated by suckling, & by +ve feedback during labour, as well as by
different sexual stimuli.
In females: induces contractions during labour & lactation, central effects
on food intake & maternal & reproductive behaviour.
Men: influence sexual arousal & ejaculation.
What does ADH do?
acts on kidney, acts to inc aquaporin expression & insertion to membrane of collecting
duct, inc retention of water in response to either decreased volume or increased osmolarity of
blood.
What non-endocrine roles does the hypothalamus play?
Food and drink intake
Thermoregulation
Circadian rhythms
(ANS control)
Describe the lateral hypothalamic area?
‘Hunger centre’
Recieves olfactory input via the medial forebrain bundle
Describe the VMN?
‘Satiety centre’
Receptors for glucose and FFAs
