Hypothalamus

Question 1

What is the function of the hypothalamus?

Answer 1

Homeostasis and survivalby maintaining the set point of parameters. Involved in motivated behaviour.
It influences the ANS, endocrine system and behaviour by integrating all three.

Question 2

The hypothalamus integrates somatic and autonomic responses. Give examples of functions under hypothalamic control.

Answer 2

CVS
Blood compostion and volume
Food and water intake
Temperature control
Circadian rhythms
Reproductive behaviour
Emotional behaviour

Question 3

What supplies input into the hypothalamus?

Answer 3

Internal: Sensory receptors
External: Limbic regions, olfactory regions, retina, hippocampus

Question 4

Where are the receptors located for homeostatic control?

Answer 4

Lie in hypothalamus or in circumventricular organs e.g. viscera

Question 5

What outputs arise from the hypothalamus?

Answer 5

To pituitary for hormones
To brainstem for ANS control and coordinated behaviour
To limbic for emotion and coordinated behaviour

Question 6

What do the external input areas provide information about or for?

Answer 6

Limbic = emotional state
Olfactory region = Influences motivated behaviour
Retina = Light to SCN
Hippocampus = memory

Question 7

What is the structure of the hypothalamus?

Answer 7

Subdivided into regions that contain many nuclei. Has a heterogenous 3D structure. The nuclei work together to integrate ANS, endocrine and behaviour

Question 8

What can be identified along the anterior-posterior axis of the hypothalamus?

Answer 8

Anteriorly: Preoptic area near optic chiasm. Contains SCN and nuclei concerned with set points of homeostasis.
Posteriorly: Contains mamillary bodies

Question 9

What are mamillary bodies?

Answer 9

A collection of neurons involved in emotional processing. 1 located in each hemisphere.

Question 10

What causes Korsokoff’s syndrome?

Answer 10

Disruption of mamillary body.

Question 11

What can be identified along the medial-lateral axis of the hypothalamus?

Answer 11

3 zones located around the 3rd ventricle:

• Periventricular zone
• Medial zone
• Lateral zone

Question 12

What is within the periventricular zone of the hypothalamus?

Answer 12

A thin area containing SCN and the arcuate nucleus which is sealing off the bottom of the 3rd ventricle

Question 13

What is the arcuate nucleus involved in?

Answer 13

Feeding and anterior pituitary regulation

Question 14

What is within the medial zone of the hypothalamus? What is its function?

Answer 14

Paraventricular nuclei that release hormones to the posterior pituitary and involve feeding.

Question 15

What is within the lateral zone of the hypothalamus? What is its function?

Answer 15

Contains the lateral hypothalamic area for feeding and supraoptic nuclei which releases hormones to posterior pituitary.

Question 16

Where is ANS input received from?

Answer 16

Exteroreceptors and interoreceptors (homeostasis)

Question 17

Where is ANS output sent to?

Answer 17

Paraventricular nuclei and onto the brainstem nuclei for origin of preganglionic sym and parasym fibres for control.

Question 18

Give an example of the types of ANS functions the hypothalamus influences?

Answer 18

HR and BP

Question 19

How is the hypothalamus connected to the pituitary for endocrine control?

Answer 19

Indirectly connected to anterior pituitary via parvocellular neurosecretory cells which pass down the pituitary stalk and terminate on the capillary bed, releasing NT into blood of anterior pituitary. Releases hypophysiotropic hormones - GnRH, TRH etc that cause release of the anterior hormones into the body.
Directly connected to the posterior pituitary via magnocellular neurosecretory cells that terminate and release NT into the capillaries directly. Releases the neurohormones oxytocin and ADH that are produced in the hypothalamus.

Question 20

How is food intake regulated short term and long term? What happens if the regulation is disrupted?

Answer 20

Body continuously demands glucose, but we only provide intermittent supply so it must be stored. A disruption in glucose intake leads to starvation or obesity.

Short term regulation:

• Hypothalamic inputs from mechanoreceptors in gut and glucose receptors in the liver.
• Hypothalamic glucose and ghrelin receptors for daily intake

Long term regulation:
Body weight is regulated through adipose tissue. Adipose tissue release leptin which acts on the hypothalamus to increase satiety and reduce intake and increase metabolism (ANS to liver, pituitary hormones)

Question 21

Which hypothalamic nuclei are involved in food intake?

Answer 21

Arcuate - Has high leptin R density to detect adipose volume
Paraventricular nucleus - Controls ANS and signals to pituitary
Lateral hypothalamic area - Causes motivation to search for food and projects across cortex

Question 22

What does a lesion in the paraventricular nucleus result in?

Answer 22

Unwanted feeding = obesity

Question 23

What does a lesion in the lateral hypothalamic area cause?

Answer 23

Cessation of eating = starvation.

Linked to cancer and MS

Question 24

Which nuclei/receptors are involved in temperature control?

Answer 24

Hypothalamic thermoreceptors - Change set point temporarily during fever
Anterior hypothalamic nuclei - For heat dissipation of excess
Posterior hypothalamic nucleu - For heat rentention

Question 25

How do ANS, endocrine and behaviour all influence temperature control?

Answer 25

ANS for vasomotor changes in skin.
Endocrine increases/decreases metabolism for long term heat production and acclimatising.
Behavioural for shivering or seeking warmth/shade

Question 26

How does the hypothalamus control reproductive behaviour?

Answer 26

Integrates endocrine for puberty and cycles, ANS for sexual organs and behavioural for courtship

Question 27

What is sexual dimorphism?

Answer 27

Anatomical differences between males and females particularly in the preoptic area (sex hormone R lies within) resulting in differences in reproductive behaviour.

Question 28

Why is a brain injury to the hypothalamus rare?

Answer 28

Due to location. Located bilaterally so if one is damaged the other takes over. Location makes it inoperable due to access.

Question 29

Why is a tumour hard to identify in the hypothalamus?

Answer 29

Presents with diverse symptoms that are progressive.