Motivated Behaviour: Role of the Hypothalamus

Question 1

List the 2 general functions of the hypothalamus.

Answer 1

1 - Homeostasis.

2 - Motivated behaviours.

Question 2

List 2 reasons that explain why loss of hypothalamus function due to physical injury is rare.

Answer 2

1 - Its deep anatomical position means it is protected from surrounding tissues.

2 - One side of the hypothalamus can compensate for a loss of function in the other side.

Question 3

List 4 sources of inputs to the hypothalamus.

Answer 3

1 - Sensory inputs, e.g. olfactory and retina.

2 - Limbic regions, e.g. the hippocampus.

3 - Peripheral interoceptors, e.g. from viscera via the brainstem.

4 - Receptors within the hypothalamus.

Question 4

List 3 targets of outputs of the hypothalamus.

Through which structures does the hypothalamus send these outputs?

Answer 4

1 - Autonomic nervous system via the brainstem.

2 - Endocrine systems via the pituitary gland.

3 - Behaviour via the limbic system.

Question 5

List 2 nuclei of the hypothalamus.

Where in the axial plane are these nuclei located?

*NB there are many more than 2 nuclei in the hypothalamus.

Answer 5

1 - Preoptic nucleus (anterior).

2 - Mamillary body (posterior).

Question 6

What is the shape of the hypothalamus?

Why might this be?

Answer 6

• It is spindle shaped (enlarged in the middle).

- This is because the predominant nuclei are in the middle / intermediate area of the hypothalamus.

Question 7

List the areas of the hypothalamus.

Answer 7

1 - Periventricular.

2 - Medial.

3 - Lateral.

Question 8

List 3 nuclei found in the periventricular area of the hypothalamus.

What are the functions of these nuclei?

Answer 8

1 - Suprachiasmatic nucleus (sleep cycle regulation).

2 - Arcuate nucleus (feeding).

3 - Paraventricular nucleus (posterior pituitary control + feeding).

*NB the paraventricular nucleus spans the periventricular and medial areas, hence ‘para’ventricular.

Question 9

List 2 nuclei found in the lateral area of the hypothalamus.

What are the functions of these nuclei?

Answer 9

1 - Lateral hypothalamic area (feeding).

2 - Supraoptic nuclei (posterior pituitary control).

Question 10

Give an example of a hypothalamic nucleus that is strongly linked to control of the autonomic nervous system.

How does it exert its effects on the autonomic nervous system?

Answer 10

• The paraventricular nucleus.
• It controls the autonomic nervous system by modulating autonomic neurones originating in the brainstem that project into the periphery (e.g. the neurones that constitute thoracolumbar and craniosacral autonomic outflow).

Question 11

List 2 nuclei that are involved in the release of neurotransmitters into the posterior pituitary.

Answer 11

1 - Paraventricular nucleus.

2 - Supraoptic nucleus.

Question 12

List 2 receptors found in the hypothalamus.

*NB there are many more than 2 receptors in the hypothalamus.

Answer 12

1 - Glucose receptors.

2 - Leptin and ghrelin receptors.

Question 13

List 2 neuronal inputs to the hypothalamus.

*NB there are many more than 2 neuronal inputs to the hypothalamus.

Answer 13

1 - Mechanoreceptors from the GIT.

2 - Glucose receptors from the liver.

Question 14

What is the predominant receptor in the arcuate nucleus?

To which receptors does the arcuate nucleus send its output?

Answer 14

• The arcuate nucleus mostly contains leptin receptors.
• The arcuate nucleus then sends its outputs to the paraventricular nucleus and the lateral hypothalamic area.
• Remember all of these nuclei have functions in feeding.

Question 15

What is the function of the paraventricular nucleus in feeding?

How does it do this?

Answer 15

• The paraventricular nucleus gives a stop signal for feeding.
• It modulates autonomic and endocrine activity to adjust metabolic rate.

Question 16

What is the function of the lateral hypothalamic area in feeding?

How does it do this?

Answer 16

• The lateral hypothalamic area drives feeding.
• It modulates cortical activity to promote certain behaviours, e.g. searching for food.
• Since it is involved in decision making, it has many projections throughout the cortex.

Question 17

What is pyrexia?

What is the cause of pyrexia?

Answer 17

• Pyrexia is a raised body temperature that is characteristic of a fever.
• It is the result of the increase in the set-point of body temperature by the hypothalamus.

Question 18

List 1 autonomic, 1 endocrine and 3 behavioural changes caused by the hypothalamus responding to temperature changes.

Answer 18

• Autonomic: Vasomotor changes in the skin.
• Endocrine: Change in metabolism.
• Behavioural: Shivering, panting, seeking warmth / shade.

Question 19

List 1 autonomic, 2 endocrine and 1 behavioural changes relating to reproduction that are mediated by the hypothalamus.

Answer 19

• Autonomic: Sexual organ function.
• Endocrine: puberty and the menstrual cycle.
• Behavioural: Courtship behaviour.

Question 20

Give an example of an anatomical difference between male and female brains.

Answer 20

The sexual dimorphic nucleus of the hypothalamus is significantly larger in males than in females.