Anatomy-Hypothalamus Flashcards
Where in the brain is the hypothalamus located?
In the walls of the third ventricle. Posterior to the lamina terminalis, below the hypothalamic sulcus and superior to the mammillary bodies.
What is the hypothalamus’s general role in maintaining homeostasis?
Body conditions move from set point -> Change detected -> Corrective mechanisms activated -> Conditions returned to set point -> Corrective mechanisms deactivated.
What regulatory feedback loops depend on the hypothalamus?
Energy metabolism (hunger), fluid balance (thirst), body temperature, response to stress (emotions), reproduction, immune response.
What are the three hypothalamic controls?
Autonomic response (activates brainstem and spinal cord), behavior response (activates cortex, amygdala and hippocampus) and endocrine response (release of pituitary hormones)
What regions of the hypothalamus are responsible for parasympathetic control? What parts are responsible for sympathetic control?
Parasympathetic = anterior and medial. Sympathetic = lateral and posterior.
It’s a nasty day in August and you are running. How does the hypothalamus mediate thermoregulation so you don’t burn up?
Unconscious pathway (parasympathetic vasodilation + sweating = heat loss) and conscious pathway (signaling to cortex initiates behavioral responses).
When you get mad because the Yankees lost, what is the hypothalamus’s role in emotional response?
It receives input from the frontal cortex and responds accordingly.
It’s a freezing day in December and you are running. How does the hypothalamus mediate thermoregulation so you don’t freeze?
Unconscious (parasympathetic increased muscle tone = shivering, sympathetic core vasodilation, thyroid hormone = increased metabolism)
You get sick and tell your mommy that you have the fever. How does the hypothalamus cause fever?
Pyrogen binds to pre optic area (OVLT) -> Prostaglandin production -> Fever, chills -> Higher set point -> Pyrogen removed -> Decreased fever.
Why might blind people feel constantly jet lagged?
CN II fibers project to the suprachiasmatic nucleus in the hypothalamus (retinohypothalamic tract). The hypothalamus causes melatonin release form the pineal gland during night time. If you are blind and cannot receive light signals, your circadian rhythm will be off.
Where do vasopressin (ADH) and oxytocin come from?
They are made in the paraventricular and supraoptic nuclei of the hypothalamus and then transported along axons in the hypothalamoneurohypophysial tract to the posterior pituitary where they are secreted into the blood.
How are ACTH, TH, GH, LH and prolactin
The medial hypothalamic neurons generate releasing or inhibiting factors that are transported to the hypophysial portal system in the anterior pituitary via the tuberohypophysial tract. Once they arrive in the anterior pituitary, they bind to cells, causing them to secrete or retain their respective hormones.
How does the hypothalamus mediate the stress response for your pending exam?
Hypothalam-pituitary-adrenal (HPA) axis. Danger sensed by limbic system -> corticotropin releasing hormone (CRH) released by hypothalamus -> Ant. pituitary released ACTH into blood -> ACTH binds to adrenal cortex -> glucocorticoid released into blood by adrenal gland -> glucocorticoids inhibit CRH and ACTH
How could brain damage result in diabetes insipidus?
Damage to the paraventricular or supraoptic nucleus in the hypothalamus prevents synthesis of vasopressin.
When you are stranded in the desert, how does the hypothalamus help you retain water?
The OVLT monitors blood osmolality. As you get dehydrated, the OVLT causes vasopressin neurons to fire. Vasopressin will decrease diuresis.
