Hypothalamus Lecture 28

Question 1

What are the functions of the hypothalamus?

Answer 1

primary function is to maintain homeostasis secondarily involved in complex emotions and behaviors as part of the limbic system
Major functions are:
circadian rhythm , water balance, feeding behavior, thermoregulation, reproduction/sexual behavior, emotional behavior, and autonomic control

Question 2

Where do the axons of the hypothalamus extend to?

Answer 2

pituitary gland

Question 3

explain what happens in the anterior pituitary?

Answer 3

neurotransmotters are relaeased from hypothalamic neurons enter the blood stream of the anteripr pituitary they reease releasing factors so the anteror pituitart can release hormones

Question 4

what hormones are released from anterior pituitary?

Answer 4

TSH--> thyroid
ACTH--> adrenal cortex
FSH/LH--> testes and ovaries
GH--> entire body
Prolactin--> mammary glands

Question 5

explain what happens in the posterior pituitary with hypothalamic neurons?

Answer 5

hypothalamic neurons go down to the posterior pituitary and a hormone is released that extend to the blood vessles of posterior pituitary

Question 6

what hormones are released from hypothalamic neurons to posterior pituitary

Answer 6

ADH–> act on renal tubules–> enhance water reabsorption

Oxytocina ct on uterine muscle

Question 7

How does hypothalamus regulate circadian rhthym

Answer 7

the suprachiasmatic nucleus of the hypothalamus sets the basic circadian via the light and dark cycles and melatonin
there are light and dark cycle’s when eyes see dark the pineal gland responds and releases melatonin the melatonin acts on the suprachiasmatic nuclei to regulate circadian rhythm

Question 8

what is temperature setpoint?

Answer 8

the body temperature is regulated at 37 degrees celsius

Question 9

What is hyperthermia

Answer 9

High temperature at around 41 degrees celsius experience convulsions (CNS effect) and at 43 death occurs( irreversible damage to cells)

Question 10

What is hypothermia

Answer 10

Low temperature As temperature falls confusion results at at 28 degrees the body looses the ability to thermoregulate and temp will decline further and death will eventually occur

Question 11

Mechanism in temperature regulation stimulated by cold

Answer 11

Decrease in heat loss–> vasoconstriction and behavioral

increase in heat production–> increase in thyroid hormone and epinephrine and shivering occur

Question 12

Mechanism in temperature regulation stimulated by heat

Answer 12

Increase heat loss–> vasodilation, sweating, behavioral

Decrease heat production–> decrease tone, activity, decrease thyroid hormone, epi, decrease appetite

Question 13

Explain mechanism of a Fever

Answer 13

If you have an infection→ macrophages secrete endogenous pyrogens
Endogenous pyrogens are immune response which are chemical messengers that cause hypothalamic messengers to be raised
The release of endogenous pyrogens→ firing of neural receptors and increase plasma → hypothalamus increases temperature setpoint
Increase in temp setpoint→
Skeletal muscle: curl up put on clothes and blanket→ less heat loss
Skeletal muscle : shivering→ increase heat production
Skin arterioles→increase in vasoconstriction→ decrease in heat loss
All these effects lead to heat production greater than heat loss→ heat retention → increase in body temperature

Question 14

Explain hypothalamic regulation of water balance

INCREASE THIRST

Answer 14

thirsty –> If you ingest a lot of H2o → decrease in fluid osmolarity and an increase in H2O concentration→ decrease in firing by Hypothalamic osmoreceptors→ decrease in vasopressin secreted by posterior pituitary→ decrease in plasma vasopressin→ decrease in tubular permeability to H20 and decrease H20 reabsorption→ increase in H2O excretion

Question 15

what signals Satiety

Answer 15

there are many signals for satiety. combination of plasma glucose, temperature, distension of GI, alterations in number of peptide hormones

Question 16

What are the appetite stimulation hormones

Answer 16

Neuropeptide Y= peptide hormone in hypothalamus and SNS its a potent feeding stimulus and is involved in fat storage circadian rhythm and blood pressure control
Ghrelin= hunger hormone released by stomach and upper intestines in response to significant weight loss acts on hypothalamus to stimulate appetite also released in response to stress
Orexins= neuropeptide hormone released by hypothalamic neurons stimulate appetite and promote wakefulness occurs in gut and CNS

Question 17

What are the appetite Inhibiting hormones

Answer 17

Leptin= released by fat cells and counteracts the effects of Neuropeptide Y and inhibits orexin release
Insulin= released from pancreas acts similarly to leptin but less potent
CCK(cholecystokinin)= rapidly released in gut in response to nutrients in gut especially proteins and fats
Peptide Y(PYY)= released by gut in response to ingestion of fats acts slower than CCK