57 Homeostatic control by the CNS

Question 1

Which of the following are specific functions of the hypothalamus?

A. control endocrine functions, e.g. reproductive functions
B. control autonomic functions like emergency response to stress
C. control circadian cycle
D. control energy metabolism
E. control blood pressure
F. regulate body tempature

Answer 1

All of the above
D: feeding behaviour
C: sleep wake cycle

Question 2

What are the major inputs to the hypothalamus?

Answer 2

1. brainstem/ spinal cord
2. amygdala (limbic areas), hippocampus
3. cortex
4. eyes

Question 3

What are the major outputs of the hypothalamus? What control are they involved in?

Answer 3

1. Brainstem, spinal cord (autonomic control)
2. Limbic system: hippocampus/ amygdala (motivational control)
3. Cortex (motivational control)
4. Pituitary gland (neuroendocrine control)

Question 4

How can the hypothalamus access to blood composition?

Answer 4

1. Via circumventricular organs (subfornical organ,…) where the BBB are porous
2. via the pituitary gland to control endocrine functions

Question 5

______________ neurons in different hypothalamic nuclei (arcuate, paraventricular etc.) release different hypothalamic factors that reach capillary beds in the anterior pituitary

Answer 5

Parvocellular

Question 6

Magnocellular neurons release _____________ and _____________ into _________ pituitary.

Answer 6

Oxytocin and vasopressin; posterior

Question 7

Oxytocin and vasopressin are produced by the magnocelluplar neurons in the _____________ and ___________ nucleus.

Answer 7

supraoptic nucleus; paraventricular nucleus

Question 8

Main functions fo oxytocin and vasopressin?

Answer 8

Oxytocin: uterine contraction, lactation;
Vasopressin: antidiuretic hormone

Question 9

Briefly describe the endocrine response to stress.

Answer 9

Periventricular hypothalamus secretes CRH into hypopituitary circulation > triggers ACTH release into circulation.
ACTH stimulates release of cortisol from the adrenal cortex > increase energy resources and immunosuppression etc.

Question 10

In stress under emergency situation, activation of sympathetic/parasympathetic and release of ___________ from the adrenal _________; resulting in pupil dilation, increased pulmonary ventilation, glycogenolysis, increase in blood glucose level.

Answer 10

sympathetic;

adrenaline; medulla

Question 11

After receiving sensory information from the entire body, the hypothalamus compares the sensory information with ________________ such as ________________.

Answer 11

Biological set points;

temperature, plasma volume/osmolarity, fat reserve

Question 12

When detected a deviation from the set point, the hypothalamus adjusts ___________, __________ and ___________ responses to restore homeostasis.

Answer 12

Endocrine; autonomic, behavioural

Question 13

The ob gene and its project, _______, is a critical factor controlling feeding behavior, and therefore body fat reserve.

Answer 13

leptin

Question 14

Describe the events happen when body fat reserve increases.

Answer 14

When body fat increases, [leptin] increases, detected by leptin receptors in the arcuate nucleus expressing MSH + CART.

1. Hormonal: stimulate release of ACTH and TSH from the pituitary > increase metabolic rate
2. Autonomic: activate sympathetic preganglionic neurons > increase sympathetic activity
3. Behavioral: inhibit lateral hypothalamic area > inhibit feeding behaviour

Question 15

Leptin is a hormone released by ____________ to induce ___________. Mutation of the leptin gene is a cause of rare rely onset __________.

Answer 15

Fat cells in adipose tissue;
reduced food intake;
obesity

Question 16

What is the lateral hypothalamic area for? What will happen if there is a lesion?

Answer 16

For initiating feeding, hunger center;

lesioned > anorexia (lateral hypothalamic syndrome)

Question 17

What is the ventromedial hypothalamic area for? What will happen if there is a lesion?

Answer 17

satiety center;
lesioned > obesity

(paraventricular nucleus involved in feeding)

Question 18

Describe sequence of events when there is a decrease in body fat reserve in the body.

Answer 18

Decrease body fat > [leptin] decreases > decrease of leptin inhibition on a group of NPY + AgRP-expressing arcuate nucleus neurons.

NPY (Neuropeptide Y) and AgRP are orogenic (appetite promoting)

1. Hormonal response: inhibit ACTH and TSH, decrease metabolic rate
2. Autonomic: activate brainstem and spinal preganglionic neurons, increase parasympathetic activity
3. Behavioural: stimulate lateral hypothalamic area > stimulate feeding