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7. CVS > 8. The Autonomic Nervous System and the CNS > Flashcards

8. The Autonomic Nervous System and the CNS Flashcards

1
Q

What are the two divisions of the autonomic nervous system?

A

Parasympathetic nervous system and sympathetic nervous system.

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2
Q

What is the organisation of the sympathetic division of the ANS?

A

Thoracolumbar origin - thoracic and lumbar. Preganglionic neurones arise from T1 to L2 or L3. Most synapse with postganglionic neurones in the paravertebral chain of ganglia, some synapse in pre vertebral ganglia.

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3
Q

How is the parasympathetic division of the ANS organised?

A

Craniosacral origin. Preganglionic fibres travel in the cranial nerves or sacral outflow. Synapse with neurones in ganglia close to target tissue.

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4
Q

How is the arrangement of pre and post-ganglionic neurones different in sympathetic and parasympathetic ANS?

A

Sympathetic has nearly equal lengthened pre and post ganglionic neurones, the postganglionic neurone synapses next to the target tissue.
Parasympathetic has a longer preganglionic than postganglionic, the postganglionic neurone synapses in the target tissue.

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5
Q

What do preganglionic neurones release?

A

Acetylcholine. This acts on nAChR on the postganglionic cell.

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6
Q

What do postganglionic neurones response to in the sympathetic ANS and parasympathetic ANS?

A

Sympathetic - noradrenergic, noradrenaline is the transmitter.
Except sympathetic Innervation of sweat glands, have muscarinic ACh receptors.
Parasympathetic - choline rigid, acetylcholine is the transmitter.

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7
Q

What are chromaffin cells?

A

Specialised postganglionic sympathetic neurones in the adrenal medulla. They release adrenaline into the blood stream.

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8
Q

What do noradrenaline and adrenaline act on?

A

Adrenoreceptors.

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9
Q

What are the different types of adrenoreceptors?

A

a-adrenoreceptors: a1 and a2

B-adrenoreceptors: B1, B2 and other subtypes.

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10
Q

Why is the fact that different tissues have different adrenoreceptors types clinically important?

A

It allows for selectivity of drug action.

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11
Q

What receptors does ACh act on in the parasympathetic nervous system?

A

Muscarinic receptors on effector cells, G protein-coupled receptors.

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12
Q

What are the functions of the autonomic nervous system?

A

Regulates physiological functions. Sympathetic activity increase under stress and parasympathetic system is more dominant in basal conditions, so the two work together for a balanced regulation.

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13
Q

What does the ANS not affect in the heart?

A

Does not initiate electrical activity in he heart.

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14
Q

How does parasympathetic input affect the heart?

A

Postganglionic cells release ACh which acts on M2-receptors. This decreases the heart rate and decreases AV node conduction velocity.

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15
Q

How does sympathetic input affect the heart?

A

Innervates the SA node, AV node and myocardium from release of noradrenaline. NA acts mostly on B1-adrenoreceptors to increase the heart rate and increase force of contraction.

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16
Q

What are the three keys events in action potential in the SA node?

A

Slow depolarisation (pacemaker potential) from funny current, HCN channels. Rapid opening of Ca2+ channels. Closing of Ca2+ channels and opening of K+ channels.

17
Q

How does the ANS effect the pacemaker potentials?

A

Sympathetic activity increases the slope of the pacemaker potential so raises heart rate.
Parasympathetic activity decreases the slope of the pacemaker potential so decreases the heart rate.

18
Q

How does noradrenaline increase force of contraction?

A

It acts on B1-receptors in myocardium and causes an increase in cAMP so PKA is activated. Phosphorylation of Ca2+ channels so Ca2+ entry increases in plateau of the action potential. Increased uptake of Ca2+ in SR and increased sensitivity of contractile machinery to Ca2+ so there is an increased force of contraction.

19
Q

How does the ANS effect vasculature?

A

Most vessels have sympathetic innervation, except some specialised tissue.
Most arteries artery and veins have a1-adrenoreceptors, coronary and skeletal muscle vasculature have B2-receptors too.

20
Q

How does vasomotor tone allow for vasodilation and vasoconstriction to occur?

A

Decreased sympathetic output leads to vasodilation, increased sympathetic output leads to vasoconstriction.

21
Q

What does circulating adrenaline bind to?

A

B2-adrenoceptors preferentially, higher concentrations will also bind to a1-adrenoceptors.

22
Q

What effect does activating a1 and B2-adrenceptors have on vascular smooth muscle have?

A

Activating B2-adrenoceptors causes vasodilation. It increases cAMP so activates PKA and opens K+ channel and inhibits MLCK so relaxes smooth muscle.
Activating a1-adrenoceptors causes vasoconstriction. It stimulates IP3 production so increase [Ca2+]i from stores and influx of extracellular Ca2+. This leads to contraction of smooth muscle.

23
Q

What is the effect of local metabolites?

A

Strong vasodilator effect. This ensures adequate perfusion of skeletal and coronary muscle.

24
Q

Overall, how is the CVS controlled?

A

Changes in state are communicated to the brain via baroreceptors and atrial receptors. This alters the activity of efferent nerves.

25
Q

What change do baroreceptors detect?

A

Increased arterial pressure, by stretching the receptors. Q

26
Q

What are the three main categories of dugs that act on the ANS?

A

Sympathomimetics (mimic action of the sympathetic nervous system), adrenoceptors antagonists and cholinergics.

27
Q

What are the cardiovascular uses of sympathomimetics?

A

Adrenaline to restore function in cardiac arrest.
B1-agonist, dobutamine, in cardio genie shock.
Adrenaline for anaphylactic shock.

28
Q

What are some uses other than cardiovascular for sympathomimetics?

A

B2-agonist, salbutamol, for asthma.

29
Q

What are the uses of adrenoreceptors antagonists?

A

a-adrenoreceptors antagonists - antihypertensive. Inhibits the action of NA on vascular smooth muscle a1-receptors.
B-adrenoreceptors antagonists - propranolol (non-selective B1/B2 antagonist). Slows heart rate and reduces force of contraction, B1, causes bronchoconstriction, B2.
- atenlol, B1 selective so less risk of bronchoconstriction.

30
Q

What is a use for muscarinic agonist cholinergics?

A

Pilocarpine - used in glaucoma (pressure build up in the eye), activates constrictor papillae muscle to drain and reduce pressure in eye.

31
Q

What is the muscarinic antagonist use of cholinergics?

A

Atropine or tropic amide. Increases heart rate and causes bronchial dilation. Also can dilate pupils for examination of the eye.

32
Q

What does the autonomic nervous system have control over?

A

Smooth muscle, exocrine secretion, rate and force of contraction in the heart.

7. CVS (21 decks)

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