CVS 5 Autonomic Nervous System

Question 1

What does the autonomic nervous system control?

Answer 1

All involuntary actions

Question 2

Divisions of the autonomic nervous system

Answer 2

Parasympathetic - rest + digest
Sympathetic - fight or flight

Question 3

Describe the preganglionic nerve in the sympathetic nervous system

Answer 3

Short
Myelinated

Question 4

Describe the postganglionic nerve in the sympathetic nervous system

Answer 4

Long
Non-myelinated

Question 5

Describe the preganglionic nerve in the parasympathetic nervous system

Answer 5

Long
Myelinated

Question 6

Describe the postganglionic nerve in the parasympathetic nervous system

Answer 6

Short
Non-myelinated

Question 7

What is released from the preganglionic nerve in the sympathetic nervous system?

Answer 7

Acetylcholine

Question 8

What is released from the postganglionic nerve in most sympathetic nervous system?

Answer 8

Noradrenaline

Question 9

What is released from the preganglionic nerve in the some sympathetic nervous system?

Answer 9

Acetylcholine

Question 10

What is released from the preganglionic nerve in the parasympathetic nervous system?

Answer 10

Acetylcholine

Question 11

What is released from the postganglionic nerve in the parasympathetic nervous system?

Answer 11

Acetylcholine

Question 12

What receptor does acetylcholine from the pregangionic nerve act on?

Answer 12

Nicotinic ACh receptors

Question 13

What receptor does acetylcholine from the postganglionic nerve act on?

Answer 13

Muscarinic ACh receptors

Question 14

What receptor does noradrenaline from the postganglionic nerve act on?

Answer 14

Adrenoreceptors

Question 15

Origins of the sympathetic nervous system

Answer 15

Thoracic + lumbar regions of spine

Question 16

Origins of parasympathetic nerves system

Answer 16

Cranial + sacral regions of spine

Question 17

Describe the action of parasympathetic input into the heart

Answer 17

• Via the vagus nerve
• Innervate with epicardial surface or SAN + AVN
• Releases acetylcholine
• Act on M2 Muscarinic receptors
• negative chronotropic effect (slows HR)
• decreases AVN conduction velocity

Question 18

Effect of acetylcholine on heart

Answer 18

Negative chronotropic effect (slows HR)
Decreases AVN conduction velocity

Question 19

Describe the sympathetic input to the heart

Answer 19

• From sympathetic trunk
• Innervates with SAN, AVN + myocardium
• Releases noradrenaline
• Act on B1 adrenoreceptor
• positive chronotropic effect (^ HR)
• positive inotropic effect (increased force of contraction)

Question 20

What does an positive or negative in chronotropic effect refer to?

Answer 20

Heart rate
Positive CE - increase
Negative CE - decrease

Question 21

What does the positive or negative inotropic effect refer to?

Answer 21

Force of contraction of heart
Positive IE - increased force
Negative IE - decreased force

Question 22

Effect of noradrenaline on heart

Answer 22

Positive chronotropic effect (^ HR)
Positive inotropic effect (^ force of contraction)

Question 23

How does noradrenaline have a positive inotropic effect on the heart ?

Answer 23

positive inotropic effect = ^ force of contraction

1- act on B1 adrenoreceptors in myocardium
2- ^ CAMP - activates protein kinase A
3- PKA phosphorylates Ca2+ channels
4- ^ Ca2+ uptake in sarcoplasmic reticulum
5- more Ca2+ for contraction

Question 24

How does noradrenaline have a positive chronotropic effect?

Answer 24

1- sympathetic nervous system speeds up relaxation (decreases diastole)
2- decreases time of 1 cardiac cycle
3- increase HR

Question 25

Effect of sympathetic nervous system on SAN

Answer 25

Speeds up pacemaker potential Steeper slope Increases CAMP

Question 26

Effect of parasympathetic nervous system on SAN

Answer 26

Slows down pacemaker potential Shallower slope Less CAMP

Question 27

What happens to blood vessels and airways in anaphylaxis?

Answer 27

Blood vessels dilate Airways constrict

Question 28

What is used to treat anaphylaxis? How does this work?

Answer 28

**High does of adrenaline injection intramuscularly** - acts on a1 receptors in vessels - vasoconstriction - increased BP - acts on B2 receptors in bronchi - bronchodilation - ^ airflow

Question 29

What receptors do noradrealine act on in vessels?

Answer 29

a1 adrenoreceptors

Question 30

What receptors do circulating (normal levels) adrenaline act on in vessels?

Answer 30

B2 adrenoreceptors

Question 31

What receptors does high concentrations of adrenaline act on in vessels? Example of when this may occur

Answer 31

a1 adrenoreceptors *e.g. adrenaline injection in anaphylaxis*

Question 32

What does activating B2 adrenoreceptors in vessels cause? Explain why

Answer 32

**Vasodilation** Gs 1- Gs stimulates adenylate cyclase 2- ^ cAMP made 3- PKA activated 4- PKA phosphorylates MLCK 5- MLCK inhibition 5 - Smooth muscle contraction inhibited 6- vasodilation

Question 33

Function of PKA in myocardium

Answer 33

Phosphorylates Ca2+ channels Increase force of contraction

Question 34

Function of PKA in vascular smooth muscle

Answer 34

Inhibits MLCK by phosphorlating it >> prevents vasoconstriction >> vasodilation occurs

Question 35

Describe contraction of vascular smooth muscle

Answer 35

1- Ca2+ enter via VGCC or from sarcoplasmic reticulum 2- Ca2+ binds to calmodulin 3- Ca2+ CaM complex activates MLCK 4- MLCK phosphorylates myosin light chain 5- MLC interacts with actin > contraction 6- as Ca2+ levels fall, MLCP dephosphorylates MLC

Question 36

What does activation of a1 adrenoreceptors in vascular smooth muscle cause? Explain why

Answer 36

**^ in intracellular Ca2+ >> Contraction** 1- IP3 production 2- release of Ca2+ from SR 3- Ca2+ CaM complex activates MLCK 4- MLCK phosphorylates MLC 5- contraction 1- DAG (diacylglycerol) activated 2- DAG inhibits MLCP

Question 37

What does activation of B1 adrenoreceptors in vascular smooth muscle cause? Explain why

Answer 37

**promotes relaxation** 1- adenylate cyclase activation 2- cAMP produced 3- PKA activated 4- PKA phosphorylates MLCK 5- MLCK inhibited 6 - decrease in MLC phosphorylation 7- relaxation + less contraction

Question 38

Where are baroreceptors found?

Answer 38

Aortic arch Carotid sinus

Question 39

Explain how baroreceptors respond to an increase in arterial pressure

Answer 39

1- ^ arterial pressure causes stretch 2- stretch detected by baroreceptors 3- impulse sent to medulla oblongata 4- sends signal to decrease HR + contractility 5- BP decreases

Question 40

What effect do local metabolites have on circulation?

Answer 40

Increase in metabolites leads to vasodilation which increases flow