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Physiology & metabolism > week 4 - neuronal control of metabolism > Flashcards

week 4 - neuronal control of metabolism Flashcards

1
Q

How is neuronal control carried out?

A
  1. By signalling between different brain regions
  2. By signalling from CNS to peripheral organs
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2
Q

What does innervated/innervation mean?

A

It means “to supply nerves to”

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3
Q

Where are the different nutrient sensors in the body?

A

Glucose sensing neurons in hepatic portal veins and mesenteric veins.

Beta cells in the pancreas

Tate buds which express a glucose sensor

The small intestine also expresses a glucose sensor

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4
Q

What does glucose do?

A

Provides an essential energy source for cells.

Glucose needs to be regulated and maintained within a narrow range.

If you have a glucose imbalance, you may have metabolic conditions such as obesity, diabetes.

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5
Q

Which brain areas are involved in neuronal control of metabolism?

A

Hypothalamus
Cortex
Brain stem

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6
Q

What is the hypothalamus made of?

A

Clusters of neurons with specific functions.

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7
Q

What is the accurate nucleus?

A

It is part of the hypothalamus.

Contains 2 major neuronal populations:
AgRP
POMC

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8
Q

What are astrocytes?

A

Thy are in the accurate nucleus.
They hold high capacity glucose transporters that work as nutrients sensors for appetite controlling neurones.

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9
Q

What is POMC?

A

POMC neurones secrete MSH which signals fullness and suppresses your appetite.

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10
Q

What happens if you have a mutation with the POMC gene?

A

you can gain weight as you don’t really feel full anymore.

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11
Q

What is AgRP?

A

It signals when you’re hungry.
It signals an increased appetite, decreases metabolism.

Levels increase during periods of fasting as you are more hungry.

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12
Q

What is the anorexigenic response?

A

It is the response in which POMC secretes MSH to suppress your appetite.

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13
Q

What is the oxigenic response?

A

It is the response in which AgRP/NY is secreted to increase your appetite.

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14
Q

What happens at the ARC (accurate nucleus) and PVN (paraventricular nucleus)?

A

POMC neurones and AgRP project from the ARC and PVN to control food intake and energy balance.

This above is influenced by glucocorticoids like cortisol, insulin, leptin

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15
Q

What does GABA do?

A

GABA helps to inhibit POMC neurones so you don’t feel full

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16
Q

What happens to AgRP when you are fasting?

A

AgRP signals increase to make you feel more hungry.

AgRP also release GABA to inhibit POMC neurones (remember POMC neurones make you feel full)
so POMC activity decreases.

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17
Q

What is the ventromedial hypothalamus?

A

It also signals the feeling of satiety (feeling full)

Involved in thermogenesis (forming of heat)

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18
Q

What is the paraventricular nucleus (PVN)

A

It has autonomic functions like controlling metabolism, reproduction, growth, stress.

Source of oxytocin, vasopressin etc

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19
Q

What are the 2 cell types in the paraventricular nucleus (PVN)

A
  1. Parvocellular
  2. Magno cellular
20
Q

What are parvocellular cells?

A

They secrete vasopressin, CRH and TRH into the hypophyseal portal system. Then, these above hormones can act at the anterior pituitary gland to regulate hormone secretion.

They project into the limbic system, brain stem, spinal cord.

21
Q

What are magnocellular cells/

A

They secrete oxytocin, vasopressin DIRECTLY to the posterior pituitary.

22
Q

What is the lateral hypothalamus/

A

Stimulates feeding behaviour, wakefulness, body temp regulation, digestion, pain perception.

Contains orexigenic nucleus for orexigenic reaction which increases appetite,.

23
Q

What are melanocortins?

A

They are anorexigenic peptides (increase fullness)

They are cleaved from POMC precursor polypeptide.

24
Q

What is the dorsal vagal complex (DVC)?

A

It is part of the brain stem.
It regulates energy balance.
Integrates peripheral satiety (feeling full) signals.

Made of :
area postrema
nucleus of solitary tract
dorsal motor nucleus of vagus nerve

25
Q

What is the area postrema?

A

It is an area with leaky BBB - it has permeable capillaries.

It detects messengers in the blood and turns them into electrical signals.

Detects circulating hormones.

26
Q

What is the nucleus of the solitary tract?

A

It is a sensory nuclei

Contributes to autonomic functions/regulations as it projects to the hypothalamus/thalamus etc

27
Q

How do the nutrients cross the BBB?

A

Via transport mechanisms.
Or via leaky regions such as in the area postrema

28
Q

What is the dorsal motor nucleus of the vagus nerve?

A
29
Q

What are the different neuroendocrine signals?

A

Leptin
Insulin
Orexin
Ghrelin
CCK
GLP-1

30
Q

Describe what insulin is/

A

Produced by beta cells in the pancreas

Released when there is high blood glucose levels

Promotes glucose to be absorbed by liver, and promoted glucose to be stored as glycogen in adipose tissue.

Stops hepatic glucose production like gluconeogenesis, glycolysis etc

Signals satiety(fullness) in the brain

31
Q

What is the process of insulin transport and signalling in the brain?

A
  1. Receptor mediated transcytosis occurs - this is where molecules essential for brain function are transported across the BBB.
  2. Passive diffusion then occurs
  3. Insulin in the CSF (cerebrospinal fluid) is transported by tanycytes (nutrient sensing cells)
32
Q

how is hepatic glucose production regulated?

A
33
Q

How is adipose thermogenesis regulated?

A
34
Q

What is intranasal insulin?

A

Insulin is delivered through the nose to CNS when there is an absence of systemic insulin uptake

Travels along olfactory pathway

Exerts its functional effects on metabolism?

35
Q

Describe what leptin is?

A

It is a hormone released by adipocytes (fat cells)

Signals satiety (Feeling full)

LEARN MORE OF THIS

36
Q

What is the ob/ob gene?

A
37
Q

What is orexin?

A

It is a hormone which increases appetite and stimulates wakefulness

The cells that produce orexin can be inhibited by leptin (which signals fullness) and by glucose

If you have a lack of orexin, it can cause narcolepsy because orexin link sleep regulation and metabolism.

38
Q

Describe what ghrelin does?

A

Ghrelin is the hunger hormone.

it activates AgRP cells in the ARC

Produced by cells in the GI tract

39
Q

Describe what CCK (cholecystokinin)?

A

Signals satiety (increases fullness) and helps with digestion

Produced by cells in small intestine and causes the release of bile and digestive enzymes.

If there is no CCK satiety is delayed so you consume larger meals.

40
Q

describe GLP-1 (glucagon-like peptide)?

A

Signals satiety (feeling full)
Inhibits gastric emptying

It decreases blood glucose because it enhances the secretion of insulin which makes you feel more full by decreasing your appetite.

41
Q

What is obesity?

A

It is the accumulation of excessive fat

It causes chronic inflammation.

There could be insulin/leptin resistance (remember these signal fullness) so without these you feel less full so may eat more.

Comorbidities including cancer, cardiovascular diseases etc

42
Q

What is insulin resistance?

A

It is when the pancreas produces insulin but cells STOP RESPONDING to insulin.

Therefore, blood glucose levels remains elevated

43
Q

What is leptin resistance?

A

It is where you have leptin in your body but your body doesn’t respond to it meaning you can’t detect the feeling of satiety (feeling full)

So leads to increased hunger.

44
Q

What happens if you have a leptin mutation?

A

You can get extreme obesity with hyperphagia (great desire for food)

45
Q

How can you treat leptin mutations/.

A

Treat with recombinant leptin for weight loss and to normalise plasma lipid and insulin levels.

46
Q

What is brown adipose tissue (BAT)?

A

Produces heat to maintain body temp in cold conditions

Physiology & metabolism (8 decks)

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