Hypothalamus - Martin

Question 1

The anterior pituitary is concerned with release of what types of hormones?

Answer 1

Releasing and inhibitory factors (LH, GH, ACTH, PRL,TSH, FSH)

These are released into the venous system to act INDIRECTLY at other sites.

Question 2

The posterior pituitary is concerned with release of what types of hormones?

Answer 2

Vasopressin and oxytocin.

These are active hormone that act DIRECTLY.

Question 3

The hypothalamus projects to:

Answer 3

Efferent pathways are neural and hormonal.
Neural: Reticular Formation, brainstem nuclei,
Hormonal: Endocrine regulation through the pituitary

Question 4

What are inputs to the hypothalamus?

Answer 4

NEURAL:
• Retina (circadian rhythm)
• Sensory info from limbic system
• Visceral sensation via nucleus of the solitary tract

HORMONAL: 
• temperature
• osmolality
• glucose
• peripheral hormones

**sample the blood through the circumventricular organs

Question 5

Light information from specialized retinal ganglion cells that are intrinsically photosensitive travels directly to the ____ nucleus of the hypothalamus via the retinohypothalamic tract.

Answer 5

suprachiasmatic

Question 6

____ neurons are exquisitely sensitive to the osmolarity of the blood, and respond to cell swelling.

Answer 6

OVLT (organum vasculosum lamina terminalis)

Question 7

Under what conditions is sham rage observed?

How can sham rage be abolished?

What is the conclusion drawn from these experiments?

Answer 7

Sham rage is observed when the hypothalamus is disconnected from higher brain areas (decorticate) but the hypothalamic connections to the brainstem and spinal cord remain intact.

In contrast, disconnecting the hypothalamus from the brainstem abolishes sham rage.

The hypothalamus can initiate this suite of somatic and autonomic reactions even without appropriate context.

Question 8

With an anterior lesion of the hypothalamus you would get (too hot/too cold)?

With the posterior?

Answer 8

ANterior lesion = too hot (regulates heat dissipation).

Posterior lesion = too cold (regulates thermogenesis).

Question 9

The posterior hypothalamus regulates thermogenesis. How does it know you are too cold

Answer 9

skin cold receptors

Question 10

Neurons in the preoptic anterior hypothalamus (POAH) will (increase or decrease) their firing rate in response to INcreased temperature?

Answer 10

INcrease.

Decreased temp slows the firing rate.

Question 11

Describe the interaction between the posterior hypothalamus and the POAH in terms of temperature regulation, specifically, thermogenesis.

Answer 11

POAH inhibits the posterior hypothalamus (even if the skin is cold) until the blood temperature drops, at which point the inhibition is dropped and thermogenic mechanisms can begin.

Question 12

How does IL-1 (and other exogenous pyogens) create fever?

Answer 12

Pyogenic substance crosses the BBB at the OVLT, and induces endothelial cells to produce PGE2, which diffuses to the anterior thalamus (POAH), reducing its firing rate (effectively telling the body it is cooler than it actually is). This raises the “set point,” allowing the fever to persist until levels drop.

Question 13

What is seen with lesions of the lateral vs. medial hypothalamus with regard to body weight homeostasis?

Answer 13

Lesion lateral = anorexia
Lesion medial =overfeeding

But, it’s much more complex than
just appetite. It’s actually the “drive”
to do anything.

Question 14

What part of the hypothalamus is critical for regulation of circadian rhythm?

Answer 14

the Suprachiasmatic nucleus. It appears that if you take it out, the regularity of the sleep/wake cycle goes haywire. Also this receives direct inputs from the retina.