Lecture 29: Neurocircuitry of Metabolism 1

Question 1

What is energy balance?

Answer 1

when energy intake is equivalent to energy expenditure

Question 2

Why have complex internal regulatory mechanisms evolved to store energy in the body?

Answer 2

to store energy in the body so that it is available when needed

Question 3

Why are we motivated to eat?

Answer 3

to keep reserves at a sufficient level to ensure there will be no energy shortfall

Question 4

What are the three main components of energy balance?

Answer 4

energy intake, energy expenditure and storage

Question 5

What does energy intake include?

Answer 5

three major macronutrient groups which are carbohydrate, protein, and fat

Question 6

What does faecal loss amount to?

Answer 6

2-10%

Question 7

What does energy expenditure involve?

Answer 7

absorbed carbohydrates, proteins, and fats are transformed in vivo to substrates that can ultimately either be oxidized to produce metabolically useful energy that drives biological processes or they may be stored

Question 8

Which compounds are stored in the body?

Answer 8

triglycerides and glycogen

Question 9

What is energy used for?

Answer 9

basal metabolic rate; digestion, growth, reproduction
work/exercise; non-exercise activity thermogenesis
shivering and non-shivering thermogenesis

Question 10

How are triglycerides stored?

Answer 10

stored in adipose tissue

Question 11

How are carbohydrates stored?

Answer 11

mainly in the form of intracellular glycogen in skeletal muscle and liver

Question 12

What happens when there is an imbalance between the intake and utilisation of macronutrients?

Answer 12

this will lead to an alteration in body composition

Question 13

How much glycogen is there in the body?

Answer 13

the total mass of glycogen is relatively small, several hundred grams, and turnover is rapid; maximal amounts are observed in the post meal state

Question 14

What occurs during anabolism?

Answer 14

the body’s energy stores are replenished during and immediately after consuming a meal

Question 15

What is the condition in which blood is filled with nutrients?

Answer 15

the prandial state

Question 16

Where is glycogen and triglycerides found in the body?

Answer 16

glycogen is found in the liver and skeletal muscle

triglycerides are found in the adipose tissue

Question 17

What is the assembly of macromolecules such as glycogen and triglycerides from simple precursors known as?

Answer 17

anabolism or anabolic metabolism

Question 18

What occurs during catabolism?

Answer 18

the stored glycogen and triglycerides are broken down to prove the body with a continuous supply of the molecules used as fuel for cellular metabolism

Question 19

What is the process of breaking down complex macromolecules called?

Answer 19

catabolism or catabolic metabolism

Question 20

What will happen when underfed and overfed animals are given the ability to eat whenever they want?

Answer 20

overfed animals will lose weight and underfed animals will gain weight and both groups will match that of the controls

Question 21

What is the set point for body mass determined by?

Answer 21

physiological responses that regulate both food intake and energy expenditure -> seek to maintain an appropriate fat mass and can counteract even modest imposed changes in energy intake and fat mass

Question 22

Where is the hypothalamus located?

Answer 22

sits below the thalamus, along the walls of the third ventricle and is connected via a stalk to the pituitary gland, which dangles below the brain just above the roof of the mouth

Question 23

What is the role of the hypothalamus?

Answer 23

regulates temperature, hunger, satiety, thirst, sexual development, fight or flight stress response, and sleep

Question 24

What is the hypothalamus made up of?

Answer 24

several distinct divisions or nuclei which are bilateral

Question 25

What does each nuclei of the hypothalamus contain and coordinate?

Answer 25

each nuclei contains different cell types and coordinates different physiological functions

Question 26

What does each nuclei of the hypothalamus receive input from?

Answer 26

each nuclei receives input from different brain regions and in turn output to different parts of the brain

Question 27

Why is the neurocircuitry of the hypothalamus incredibly complex?

Answer 27

because there is significant intra-nuclei connectivity

Question 28

What is the role of the arcuate nucleus of the hypothalamus?

Answer 28

plays a critical role in

feeding behaviour, energy expenditure and is capable of sensing metabolic hormones in the blood

Question 29

What is the role of the ventral medial hypothalamus?

Answer 29

plays a critical role in feeding behaviour, energy expenditure and reproduction

Question 30

What is the role of the dorsomedial hypothalamus?

Answer 30

plays a key role in adaptive thermogenesis and feeding behaviour

Question 31

What is the role of the lateral hypothalamus?

Answer 31

plays a role in sleep and arousal and acts as a critical reply between the Arc and VMH and higher centres of the brain involved in motivation and reward

Question 32

What is the role of the paraventricular hypothalamus?

Answer 32

important autonomic control centres in the brain, with neurons playing essential roles in controlling stress, metabolism, reproduction and gastrointestinal, renal and cardiovascular functions

Question 33

What is the role of the median eminence?

Answer 33

circumventricular organ which has permeable capillaries and serves as an interface between the neural and peripheral endocrine systems

Question 34

What did lesions in the lateral hypothalamus result in?

Answer 34

caused anorexia and weight loss

leaves the animal inappropriately satiated so they don’t eat

Question 35

What did lesions in the ventral medial hypothalamus result in?

Answer 35

caused hyperphagia and obesity

leaves the animal insatiable so they over eat

Question 36

What are the two main cell types contained in the arcuate nucleus of the hypothalamus?

Answer 36

AgRP / neuropeptide Y neurons and proopiomelanocortin neurons

Question 37

What is the role of AgRP neurons?

Answer 37

are orexigenic (increase
food intake) and decrease energy expenditure

Question 38

What is the role of POMC neurons?

Answer 38

are anorexigenic (decrease food intake) and promote energy
expenditure

Question 39

What do AgRP neurons promote?

Answer 39

positive energy balance

Question 40

What did ablation of AgRP neurons in adult mice lead to?

Answer 40

profound weight loss, loss of feeding and death within 10 days unless force fed

Question 41

What did ablation of POMC neurons in adult mice lead to?

Answer 41

profound weight gain, increased adiposity and enhanced food intake

Question 42

What are tanycytes?

Answer 42

a subtype of ependymal cells with long processes that extend into the hypothalamic parenchyma

Question 43

What is the role of tanycytes?

Answer 43

their tight junctions prevent the diffusion of blood-borne molecules into the adjacent CSF

Question 44

What do tanycytes share some features with?

Answer 44

glia/astrocytes and express GABA receptors like neurons

Question 45

Where are alpha 1 and alpha 2 tanycytes found and where do they project?

Answer 45

found along the ependymal surface of the VMH and ARC

project to adjacent hypothalamic regions and contact blood vessels and neurons

Question 46

Where do beta 1 tanycytes reside?

Answer 46

in the lateral extensions of the infundibular recess whereas beta 2 tanycytes line the floor of the ventricle

Question 47

What do tanycytes play a crucial role in?

Answer 47

controlling energy balance and regulating the access of peripheral metabolic signals to the ARC