Motivated behaviour: Role of the hypothalamus

Question 1

What is the anatomical location of the hypothalamus?

Answer 1

Sits in the midline at the base of the brain

Question 2

What extends from the hypothalamus?

Answer 2

Pituitary gland.

Question 3

Where does the hypothalamus receive inputs from and send outputs to?

Answer 3

It receives inputs from the periphery and elsewhere in the brain and sends outputs across the brain to control a large number of functions.

Question 4

What are the general functions of the hypothalamus?

Answer 4

1. Maintains homeostasis. 2. Controls motivated behaviour.

Question 5

What is homeostasis?

Answer 5

Constant internal environment (e.g., blood glucose levels, body temperature) important for survival.

Question 6

What is a set point in homeostasis?

Answer 6

Allows the body to compare the actual measures to the set point.

Question 7

What does the hypothalamus ultimately integrate?

Answer 7

Integration of somatic and autonomic responses.

Question 8

Examples of what the hypothalamus controls?

Answer 8

1. Temperature control. 2. Reproductive behaviour via its action on the pituitary. 3. Emotional behaviour (e.g., crying when upset). 4. Food/water intake. 5. Blood composition/volume. 6. Cardiovascular system. 7. Circadian rhythms (e.g., sleep).

Question 9

What are the possible causes of hypothalamic damage?

Answer 9

1. Physical brain injury (rare due to anatomical location). 2. Damage via a tumour growth or interruption to blood supply.

Question 10

What are the impacts and clinical considerations of hypothalamic lesions?

Answer 10

1. Diverse range of symptoms depending on the affected part. 2. Progressive changes over time. 3. Difficult to operate if inoperable.

Question 11

How does the hypothalamus control various functions?

Answer 11

It influences and integrates the ANS, endocrine system (via pituitary), and behaviour.

Question 12

What are the two mechanisms by which inputs arise in the hypothalamus?

Answer 12

1. Sensory inputs from monitoring our internal environment. 2. Sensory inputs from outside the body/other parts of the brain.

Question 13

How do we get from processing in the hypothalamus to changes in the body?

Answer 13

Outputs from the hypothalamus to the pituitary, brainstem, and limbic system control homeostatic functions.

Question 14

What is the hypothalamus made up of?

Answer 14

A collection of many nuclei with individual connections and functions.

Question 15

Which axes are used to identify regions in the hypothalamus?

Answer 15

1. Anterior-posterior axis. 2. Medial-lateral axis.

Question 16

What are the three zones of the hypothalamus?

Answer 16

1. Periventricular zone. 2. Medial zone. 3. Lateral zone.

Question 17

What nuclei do we find in each zone along the medial-lateral axis?

Answer 17

Periventricular zone: SCN, arcuate nucleus, paraventricular nucleus. Medial zone: paraventricular nucleus. Lateral zone: lateral hypothalamic area, supraoptic nuclei.

Question 18

Which nuclei are involved in feeding?

Answer 18

Arcuate, paraventricular, and lateral hypothalamic nuclei.

Question 19

Which nucleus controls the ANS and how?

Answer 19

The Paraventricular nucleus controls the ANS by sending outputs to the brainstem.

Question 20

How does the hypothalamus have endocrine control?

Answer 20

It connects to the pituitary via direct and indirect pathways.

Question 21

What type of behaviours does the hypothalamus control?

Answer 21

Motivated behaviours that fulfill needs or desires.

Question 22

Examples of behaviours where the three control systems are integrated by the hypothalamus?

Answer 22

1. Feeding. 2. Temperature control. 3. Reproductive behaviours.

Question 23

Why is food intake important for the hypothalamus?

Answer 23

The brain needs glucose for neuronal function, requiring a regulated storage system.

Question 24

What can happen if there’s disruption in the hypothalamus?

Answer 24

Disruption can lead to food intake regulatory mechanism issues.

Question 25

Why do we need just the right amount of storage?

Answer 25

If we do not have enough, we run the risk of starving the body of fuel. However, if we have too much, we can become obese. Our intake of food and the use of our stores is therefore very highly regulated and very accurate.

Question 26

What can happen if there's disruption in the hypothalamus?

Answer 26

Disruption of the hypothalamus leads to set point disruption, affecting food intake regulatory mechanisms. For example, those with MS or neurodegenerative diseases may experience changes in food intake regulation.

Question 27

What is involved in the short-term regulation of food intake?

Answer 27

The hypothalamus contains receptors that sample glucose levels in the blood and signals from the digestive system, such as Ghrelin. Immediate input of information also comes from mechanoreceptors in the gut and glucose receptors in the liver.

Question 28

What is involved in long-term regulation of food intake?

Answer 28

Signaling from peripheral fat stores to the brain occurs via the hormone leptin, produced by adipocytes. Leptin informs the hypothalamus about the fullness of fat stores, influencing feeding behavior.

Question 29

What happens if there are lesions in the paraventricular nucleus (PVN)?

Answer 29

Lesions in the PVN result in uncontrolled feeding and obesity, as this nucleus can control the autonomic nervous system and the pituitary gland, affecting metabolic rate.

Question 30

What happens if there are lesions in the lateral hypothalamic area (LHA)?

Answer 30

Lesions in the LHA lead to cessation of eating, resulting in starvation, as this region is responsible for motivation to seek food.

Question 31

What is the summary of the roles of the PVN and LHA?

Answer 31

The PVN suppresses food intake while the LHA promotes eating, creating a seesaw effect to control food intake.

Question 32

What is the role of the hypothalamus in food intake regulation?

Answer 32

The hypothalamus affects pituitary hormone secretion to influence metabolic rate, helping to maintain normal body weight and storage levels through adjustments in motivation and activity.

Question 33

How does the hypothalamus control body temperature?

Answer 33

The hypothalamus contains neurons that act as thermoreceptors, regulating body temperature within a narrow range.

Question 34

What happens when body temperature goes outside the normal range?

Answer 34

Infections can alter the normal setpoint in hypothalamic neurons, leading to conditions like fever.

Question 35

How is normal body temperature controlled?

Answer 35

The hypothalamus integrates responses through the autonomic nervous system, endocrine systems, and behavioral changes to maintain normal body temperature.

Question 36

What role do the three control systems play in reproductive behavior?

Answer 36

The ANS controls sexual organ activity, endocrine systems regulate reproductive cycles, and behavioral systems induce reproductive behaviors such as courtship.

Question 37

Do male and female brains differ biologically?

Answer 37

Generally, male and female brains function similarly, but sexual dimorphism refers to anatomical differences between the sexes, particularly in the hypothalamus.

Question 38

What is sexual dimorphism in relation to the brain?

Answer 38

The sexual dimorphic nucleus in non-human animals and the interstitial nucleus of the anterior hypothalamus in humans show the greatest anatomical differences between male and female brains, influencing sexual reproductive behavior.

Question 39

What is an analogy for understanding differences between male and female brains?

Answer 39

Similar to height differences, while on average males are taller than females, there is significant overlap in height distributions, indicating that individual differences can be greater than average differences.