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LCRS > Neuroscience 9 - The autonomic nervous system > Flashcards

Neuroscience 9 - The autonomic nervous system Flashcards

1
Q

Is the trachea and bronchioles innervated by sympathetic fibres?

A
  1. No, the smooth muscle in the tissue is instead influenced by catecholamines that are released into circulation.
  2. This is the same with blood vessels dilating as a result of catecholamines.
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2
Q

What happens when you denervate the heart? And why?

A
  1. The heart rate would increase.

2. This is because the heart is normally parasympathetic dominant.

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3
Q

How many parasympathetic nerves are there? And what are they?

A
  1. 4 cranial nerves:
    - Oculomotor nerve (CN III).
    - Facial nerve (CN II).
    - Glossopharyngeal nerve (CN IX).
    - Vagus nerve (CN X).
  2. 1 sacral nerve:
    - Splachnic nerve.
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4
Q

What does the Vagus nerve (CN X) innervate?

A

It innervates the organs such as the heart, lungs, stomach, pancreas and small intestine.

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5
Q

Describe the structure of the parasympathetic nervous system.

A
  1. Starts at the cranial or sacral region.
  2. Very long pre-ganglionic fibre.
  3. Ganglion located close to the target organ.
  4. Short post-ganglionic fibre innervates from the target organ.
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6
Q

What is the important neurotransmitter in the parasympathetic nervous system?

A

Acetyl choline (released by both the pre and post ganglionic fibres).

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7
Q

Where do sympathetic nerves originate from?

A

Thoracolumbar outflows, from the thoracic and lumbar regions.

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8
Q

Describe the structure of the sympathetic nervous system.

A
  1. Starts at the thoracic or lumbar region.
  2. Short pre-ganglionic fibres leave spinal cord and form the sympathetic trunk (row of linked ganglia adjacent to spinal cord).
  3. Long post-ganglionic fibres then innervate the target tissue. One pre-ganglionic fibre can link to many post-ganglionic fibres.
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9
Q

What are the neurotransmitters of the sympathetic nervous system?

A

Acetyl choline released by the pre-ganglionic fibres and noradrenaline released by the post-ganglionic fibres.

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10
Q

What are 2 exceptions to the normal sympathetic nervous system?

A
  1. There is only one pre-ganglionic fibre going to the adrenal gland (there is no post-ganglionic fibre). The adrenal gland then releases adrenaline and noradrenaline and acts like a post-ganglionic fibre.
  2. Some post-ganglionic fibres to the skin and sweat glands release ACh instead of noradrenaline.
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11
Q

Why does the adrenal gland release noradrenaline?

A
  1. Noradrenaline released by neurones are removed very quickly from synapses.
  2. Hence the effect is very short lived.
  3. However, noradrenaline released into the blood stream stays for a longer time and hence has an effect for a longer period.
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12
Q

How is noradrenaline removed from the blood?

A

It is metabolized in the liver.

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13
Q

Why are most of the pre-ganglionic fibres of the sympathetic nervous system synapsed to form the sympathetic trunk?

A

To allow highly coordinated responses. Lots of tissues being activated together.

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14
Q

Explain how pupillary constriction works.

A
  1. The cranial parasympathetic pre-ganglionic nerve projects down to the ganglion located close to the eye.
  2. The parasympathetic post-ganglionic nerve then innervates the iris muscle (releases ACh).
  3. Pupil constriction.
  4. Sympathetic system has opposite effect (dilation).
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15
Q

How does the ciliary muscle contract?

A

As a result of the parasympathetic nervous system. Releases ACh and causes lens to bulge.

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16
Q

How is the stomach controlled by the parasympathetic nervous system?

A
  1. The vegas nerve from the cranial region projects down to the ganglion close to the stomach.
  2. The short post-ganglionic fibre innervates the stomach to stimulate the secretion of acids and enzymes as well as muscle contraction.
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17
Q

What is the enteric nervous system?

A
  1. It is a system that controls the GI.
  2. It can work independently of the brain.
  3. Sensory neurones detect chemical substances or tension caused by food = motor neurones then change secretions or cause vasoconstriction/vasodilation.
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18
Q

How does sympathetic and parasympathetic affect the GI?

A
  1. Sympathetic - decreases motility, stimulates contraction of sphincters and inhibits secretory activity.
  2. Parasympathetic - increases motility, causes relaxation of sphincters and stimulates secretory activity.
19
Q

How does the sympathetic and parasympathetic affect the heart?

A
  1. SNS increases heart rate.

2. PNS decreases heart rate.

20
Q

How is blood pressure measured by the body?

A

Baroreceptors in large arteries measure the pressure and an afferent nerve conducts the signal to the CNS.

21
Q

What effect does increased sympathetic activity have on TPR (total peripheral resistance)?

A

Increased TPR.

22
Q

How does increased sympathetic activity increase BP?

A

Increased CO (from increased HR and contractility) and increased TPR.

23
Q

Are the lungs innervated by sympathetic or parasympathetic nerves?

A

Only innervated by parasympathetic nerves.

24
Q

How does the sympathetic nervous system increase oxygen delivery to the lungs?

A

Via noradrenaline/adrenaline from the adrenals = dilation of airways.

25
Q

What is the micturition reflex?

A
  1. Pressure build up in bladder.
  2. Stimulation of parasympathetic = detrussor muscle contracts.
  3. Inhibition of sympathetic = internal sphincter relaxes.
  4. External sphincter needs to be opened via voluntary control (not ANS).
26
Q

What are the main neurotransmitters used by the autonomic nervous system?

A
  1. Acetyl Choline.
  2. Noradrenaline.
  3. Adrenaline.
    Last two are catecholamines.
27
Q

Which neurotransmitters does the Parasympathetic nervous system use?

A

Acetyl Choline.

28
Q

Which neurotransmitters does the sympathetic nervous system use?

A
  1. Acetyl Choline in pre-ganglionic fibres.
  2. Noradrenaline in post-ganglionic fibres.
  3. Adrenaline released by adrenal medulla.
  4. ACh in some post-ganglionic fibres.
29
Q

What is the effect on the heart when you block ACh action in autonomic ganglia?

A

Depends:

  1. At rest = parasympathetic dominant, hence inhibition of ACh increases HR.
  2. During exercise = sympathetic dominant, hence inhibition of ACh decreases HR.
30
Q

What are the receptors for ACh?

A
  1. Nicotinic - ion channel receptor, K+ in Na+ out (quick).

2. Muscarinic - G-protein receptor. In target organ (slower response).

31
Q

Where are nicotinic receptors located?

A

In ganglions.

32
Q

Where are muscarinic receptors located?

A
  1. At the end of parasympathetic nerves and a few exceptions of sympathetic nerves (post-ganglionic nerves). 2. At target organs.
33
Q

What is an effect of blocked nicotinic receptors in an individual at rest?

A

Constipation.

34
Q

What are the receptors for adrenaline?

A
  1. Adrenoreceptors (G-protein)

2. A1, A2, B1. B2.

35
Q

Where are adrenaline receptors located?

A

At effector organs

  1. A1 in blood vessels (constriction).
  2. B1 in the heart.
  3. B2 in lungs (dilating).
36
Q

How is Acetyl Choline synthesised?

A

Acetyl CoA + Choline using Choline acetyl transferase.

37
Q

How is Acetyl Choline released into the synapse?

A
  1. ACh is stored in vesicles close to the membrane.
  2. Action potential stimulates Ca2+ influx.
  3. ACh released into synapse.
38
Q

How is ACh metabolised?

A

Using Acetylcholinesterase to form Choline + Acetate.

39
Q

How is noradrenaline synthesised?

A
  1. Tyrosine => DOPA using Tyrosine hydroxylase.
  2. DOPA => Dopamine using DOPA decarboxylase.
  3. Dopamine => Noradrenaline (in vesicle) using beta dopamina hydroxylase.
40
Q

How is Noradrenaline degraded?

A
  1. First taken into neurone or tissue.

2. Broken down by enzymes (COMT or MAO-A).

41
Q

How is Adrenaline synthesised?

A
  1. Tyrosine => DOPA using Tyrosine hydroxylase.
  2. DOPA => Dopamine using DOPA decarboxylase.
  3. Dopamine => Noradrenaline (in vesicle) using beta dopamina hydroxylase.
  4. Noradrenaline => Adrenaline using PNMT.
42
Q

Where is Adrenaline produced and by what cells?

A

Medulla in the adrenal glands by Chromaffin cells.

43
Q

Where is adrenaline released to?

A

Released into the interstitial space and diffuses into the capillaries.

LCRS (22 decks)

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