L14 - Motivated Behaviour: Role of the Hypothalamus

Question 1

What are the general functions of the hypothalamus?

Answer 1

1 - Homeostasis

2 - Motivated behaviours

Question 2

Why is loss of hypothalamus function due to physical injury 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 (bilateral)

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 - ANS via the brainstem.

2 - Endocrine systems via the pituitary gland

3 - Behaviour via the limbic system

Question 5

What are the most anterior and posterior parts of the hypothalamus?

Answer 5

1 - Preoptic nucleus (anterior)

2 - Mamillary body (posterior)

Question 6

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

What are the functions of these nuclei?

Answer 6

1 - Suprachiasmatic nucleus (sleep cycle regulation)

2 - Arcuate nucleus (feeding)

3 - Paraventricular nucleus (posterior pituitary control + feeding) - spans the periventricular and medial areas, hence ‘para’ventricular

Question 7

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

What are the functions of these nuclei?

Answer 7

1 - Lateral hypothalamic area (feeding)

2 - Supraoptic nuclei (posterior pituitary control)

Question 8

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 8

• 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 9

Which receptors found in the hypothalamus have a role in regulating food intake?

Answer 9

1 - Glucose receptors

2 - Leptin and ghrelin receptors

Question 10

Which neuronal inputs to the hypothalamus have a role in regulating food intake?

Answer 10

1 - Mechanoreceptors from the GIT

2 - Glucose receptors from the liver

Question 11

What is the predominant receptor in the arcuate nucleus?

To which receptors does the arcuate nucleus send its output?

Answer 11

• 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 12

What is the function of the paraventricular nucleus in feeding?

How does it do this?

Answer 12

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

Question 13

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

How does it do this?

Answer 13

• 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 14

What is pyrexia?

What is the cause of pyrexia?

Answer 14

• Pyrexia = fever

- The immune system alters the set point for temperature to allow increased temperature

Question 15

What autonomic, endocrine and behavioural changes are caused by the hypothalamus responding to temperature changes?

Answer 15

• ANS – vasomotor changes in skin
• Endocrine – increased or decreased metabolism
• Behavioural – shivering, panting, seeking warmth or shade

Question 16

What autonomic, endocrine and behavioural changes relating to reproduction are mediated by the hypothalamus?

Answer 16

• ANS – sexual organ functioning
• Endocrine – influence of puberty through release of GnRH
• Behavioural – changes in courtship patterns (more important in animals)

Question 17

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

Answer 17

The sexually dimorphic nucleus (SDN) is larger in males than females