Hypothalamus and Temp Regulation

Question 1

Hypothalamus

Answer 1

Bridge structure that sits in brain and modulates visceral motor, somatic motor, neuroendocrine, and behavioral responses

Homeostasis and emotional expression for survival of individual and species

Between optic chiasm and mamillary bodies

Question 2

How does the hypothalamus regulate the autonomic and somatic motor systems?

Answer 2

Efferent projections to:
•autonomic centers and preganglionic neurons
•motor nuclei in brainstem

Question 3

How does the hypothalamus regulate the endocrine system?

Answer 3

2 ways:

Direct (oxytocin and vasopressin): via the paraventricular nucleus and supraoptic nucleus

Indirect (releasing and inhibiting factors): Control release of anterior pituitary hormones from glandular cells (LH, GH, ACTH, PRL,TSH, FSH)

Question 4

Neural inputs to hypothalamus

Answer 4

direct input from retina

processed sensory information from limbic areas (hippocampus and amygdala)

visceral sensation via nucleus of the solitary tract

Question 5

Humoral inputs to hypothalamus

Answer 5

temperature
osmolality
glucose
peripheral hormones

Question 6

Regions with fenestrated capillaries (no Blood Brain Barrier):

Answer 6

OVLT (organum vasculosum lamina terminalis)
subfornical organ
posterior pituitary
median eminence

Question 7

OVLT

Answer 7

No blood brain barrier
Near lamina terminalis
Sensitive to osmolarity of blood

Question 8

Subfornical organ

Answer 8

No blood brain barrier

Responsive to chemical composition of blood

Question 9

Milk letdown

Answer 9

Lag in time from baby rat suckling for milk and actual change in pressure (milk letdown)

Because neural input but humoral output

Question 10

How does the hypothalamus recruit motivated behavior pathways?

Answer 10

projections to the limbic system:

amygdala, hippocampus, etc.

Question 11

Sham rage

Answer 11

Experiments doing transsections of the brain reomving cerebrum, but leaving hypothalamus intect:
Normal cat-like sham rage response (also get rage response more easily)

If remove hypothalamus in addition to cerebral cortex: no sham rage response

Question 12

Pair bonding in prairie voles

Answer 12

Hypothalamus regulates posterior pituitary with regulates this pair bonding

Question 13

Control of body temperature

Answer 13

Hypothalamus

Anterior hypothalamus: “I’m too hot area” Lesion - hyperthermia

Posterior hypothalamus: Heat generating mechanisms Lesion - hypothermia

Question 14

Preoptic Anterior Hypothalamus (POAH)

Answer 14

“I’m too hot area”
Depends on temp of blood running through brain (directly senses blood temp); also gets input from skin
Hypothalamic warm sensors
Causes heat loss through vasodilating skin and sweating

Question 15

Fever

Answer 15

Still regulated by hypothalamus but higher “set point” for body temp

Question 16

Pyrogens

Answer 16

Cause fever

Exogenous (bacteria or virus) and Endogenous (Cytokines, IL1 for ex)

Question 17

Posterior hypothalamus

Answer 17

Doesn’t directly sense temp of brain; gets input from skin receptors

Question 18

How is fever generated?

Answer 18

Cytokines are released and then sensed by the OVLT which then stimulates the POAH thermoreceptors through prostaglandins to increase their tempertaure setpoint, causing vasoconstriction, shivering, and fever.

Question 19

Brown adipose tissue

Answer 19

Heat generation in infants and baby mammals
Usually not much in adult mammals
UCP1
Increased in most humans in winter
Increased in response to NE signaling from hypothalamus

Question 20

Water regulation

Answer 20

Hypothalamus
pOsm=295mosm/kg H2O
Regulate intake through thirst
Regulate output through vasopressin (ADH)

Question 21

Body weight homeostasis

Answer 21

Hypothalamus
Lesions can make people lose appetite or have too much appetite
Short-term regulation of feeding behavior

Question 22

Circadian Rhythms

Answer 22

Suprachiasmatic nucleus in hypothalamus regulates endogenous circadian rhythm
Light/dark can influence cycle
Also input from peripheral clocks and transcriptional autoregulatory feedback loops

Question 23

Tumor in pituitary could do what

Answer 23

Endocrine problems: reproduction (pregnancy lactation), regulation of body temp, regulation of body weight, water balance and BP

Vision problems