Autonomic Control Of The CVS

Question 1

What is the ANS important in regulating?

Answer 1

Heart rate
BP
Body temperature
(Homeostasis)

Question 2

How is the autonomic nervous system divided?

Answer 2

Parasympathetic nervous system
Sympathetic nervous system
(Enteric nervous system = sympathetic and parasympathetic fibres)

Question 3

How long are the pre-ganglionic neurones and post-ganglionic neurones of sympathetic fibres?

Answer 3

Pre-ganglionic = Short
Post-ganglionic = Long

Question 4

How long are the Pre-ganglionic and post-ganglionic neurones of the parasympathetic fibres?

Answer 4

Pre-ganglionic = Long
Post-ganglionic = Short

Question 5

Where do the Preganglionic neurones of the Sympathetic nervous system originate (which part of the spine)?

Answer 5

Thoracic lumbar region (Thoracolumbar)

Question 6

Where do the Preganglionic neurones of the parasympathetic nervous system originate (which part of the spine)?

Answer 6

Craniosacral origin

Question 7

Which post-ganglionic neurone is close to the target tissue, sympathetic or parasympathetic?

Answer 7

Parasympathetic post-ganglionic is close to target tissue

Question 8

What neurotransmitter is released at the end of the pre-ganglionic neurones in both the sympathetic and parasympathetic nervous system?

Answer 8

Acetylcholine (ACh)

Question 9

What receptors are present on the post-ganglionic axon bodies in both the sympathetic and parasympathetic nervous system?

Answer 9

Nicotinic ACh receptors
nAChRs

Question 10

How does binding of ACh to nicotinic acetylcholine receptors affect the receptor?

Answer 10

Conformational change opens the ion channel of the receptor
Na+ influx
K+ efflux

Question 11

What type of receptors are all of the adrenergic (adrenoreceptors)?

Answer 11

G protein coupled receptors

Question 12

What is the neurotransmitter released from the post-ganglionic neurones acting on the effector cells in the Parasympathetic nervous system?

Answer 12

Acetylcholine (ACh)

Question 13

What are the receptors present in the parasympathetic nervous system that are on the effector cells following the post-ganglionic neurones?

Answer 13

Muscarinic ACh receptors

NOT NICOTINIC ACh Receptor

Question 14

How are muscarinic ACh receptors different to Nicotinic ACh receptors?

Answer 14

Are G protein coupled receptors

Don’t have ion channels in the receptor like Nicotinic ACh receptors

Question 15

How many Alpha adrenoreceptors are there?

Answer 15

2
Alpha 1 adrenoreceptors
Alpha 2 adrenoreceptors

Question 16

How many Beta adrenoreceptors are there?

Answer 16

3
Beta 1 adrenoreceptors
Beta 2 adrenoreceptors
Beta 3 adrenoreceptors

Question 17

How many Muscarinic receptors are there?

Answer 17

3
M1
M2
M3

Question 18

How do the sympathetic and parasympathetic nervous system work to maintain a balance together?

Answer 18

Sympathetic increases under stress
Parasympathetic increases under basal resting conditions

Question 19

Where are B1 receptors found?

Answer 19

Heart

Question 20

Where are B2 adrenoreceptors found?

Answer 20

Airways of lungs

Question 21

How does the Autonomic nervous system control the cardiovascular system?

Answer 21

Controls:
-Heart rate
-Force of heart contraction
-Peripheral resistance of blood vessels

Question 22

What is responsible for initiating the electrical activity of the heart?

Answer 22

The SAN
NOT the Autonomic Nervous System

Question 23

What happens to the heart if it is denervated and why?

Answer 23

Beats Faster
Not being parasympathetically stimulated by the Vagus nerve which slows the heart (Vagal influence)

Question 24

What nerve does the parasympathetic input to the heart come from/ where do the pre-ganglionic fibres come from?

Answer 24

10th (X) cranial nerve
Also called the Vagus nerve

Question 25

Where are the post-ganglionic cells located that the vagus nerve (parasympathetic input) interacts with at the heart?

Answer 25

SAN AVN

Question 26

What receptors does the parasympathetic input to the heart act on and what effects does this have?

Answer 26

M2-receptors (muscarinic ACh receptor) Decreases heart rate = negative chronotropic effect Decreases AVN conduction velocity/increases time delay initiated

Question 27

Where are the post-ganglionic fibres of the sympathetic input to the heart innervating?

Answer 27

SAN AVN Myocardium (This is not innervated by parasympathetic input only sympathetic)

Question 28

What neurotransmitter is released by the post-ganglionic fibres of the sympathetic input to the heart?

Answer 28

Noradrenaline

Question 29

What receptor does noradrenaline mainly act on in the sympathetic input to the heart?

Answer 29

Beta 1 adrenoreceptors

Question 30

What does activation of the B1 adrenoreceptors in the heart cause?

Answer 30

Positive chronotropic effect Positive Inotropic effect

Question 31

What is meant by +ve chronotropic effect?

Answer 31

Increases heart rate

Question 32

What is meant by +ve inotropic effect?

Answer 32

Increased force of contraction

Question 33

So where does the sympathetic input to the heart happen? What receptors are acted on?

Answer 33

SAN AVN Myocardium Beta-1 adrenoreceptors

Question 34

Where does parasympathetic input to the heart happen? What receptors are acted on?

Answer 34

SAN AVN Muscarinic-2 receptors

Question 35

What are baroreceptors? Where are they found?

Answer 35

Stretch mediated receptors that detect changes in arterial blood pressure

Question 36

How do action potentials take place in the pacemaker region (SAN) of heart?

Answer 36

Slow depolarisation (slow Na+ conductance due to HCN channels causing FUNNY CURRENT) UPSTROKE = Fast opening of Ca2+ (Calcium INFLUX) DOWNSTROKE = Opening of K+ channels (K+ EFFLUX) Ca2+ channels close

Question 37

How does the sympathetic nervous system affect pacemaker potentials/heart rate?

Answer 37

INCREASES heart rate It increases the speed threshold for an action potential is reached (faster APs)

Question 38

How does the parasympathetic nervous system affect pacemaker potentials/heart rate?

Answer 38

Decreases heart rate It decreases the speed which threshold for an action potential is reached (slower APs)

Question 39

How does sympathetic activity increase the speed by which threshold for an action potential is reached?

Answer 39

Noradrenaline binds to Beta 1 receptors Activates the G protein (Gs) which stimulates adenylate cyclase (enzyme) Increases the amount of cAMP More cAMP can act on HCN channels producing a steeper FUNNY CURRENT Threshold therefore reached quicker = faster heart rate

Question 40

How does parasympathetic activity decrease the speed by which threshold for action potentials are reached slowing heart rate?

Answer 40

ACh binds to M2 receptors G protein activated (Gi) which inhibits adenylyl cyclase (enzyme) Less cAMP produced Less HCN channels stimulated so less Na+ moves in, also increased K+ conductance Therefore take longer for cell to depolarise to threshold potential since takes longer for Na+ to move in through fewer HCN channels

Question 41

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

Answer 41

Binds to Beta-1 receptor Increases cAMP cAMP activates PKA (Protein Kinase A) PKA Phosphorylates Ca2+ channels allowing Ca2+ influx into cell Influx of Ca2+ causes more Ca2+ to be released from the Sarcoplasmic reticulum PKA also inhibits Phospholamban which brings Ca2+ back int SR More Ca2+ in cytoplasm = stronger contraction

Question 42

Do most vessel only have sympathetic innervation or parasympathetic innervation?

Answer 42

Sympathetic innervation

Question 43

What receptors do most arteries and veins have?

Answer 43

Alpha 1 adrenoreceptors

Question 44

What receptors do coronary and skeletal muscle vasculature have?

Answer 44

Alpha 1 + Beta 2

Question 45

What is Vasomotor tone and why is it important?

Answer 45

The normal amount that the smooth muscle of the blood vessel is contracted at rest Allows for vasodilation if it relaxes more Allows for vasoconstriction if it constricts more

Question 46

How does activation of the alpha 1 (A1) receptor on blood vessels with both A1 and B2 adrenoreceptors affect the blood vessel? What neurotransmitter activates A1?

Answer 46

Vasoconstriction Noradrenaline

Question 47

What neurotransmitter will preferentially bind to B2 adrenoreceptors in blood vessels with both A1 and B2 at physiological concentrations?

Answer 47

Adrenaline

Question 48

What affect does adrenaline binding to B2 have on a blood vessel?

Answer 48

Vasodilation

Question 49

What affect does noradrenaline or adrenaline binding to A1 adrenoreceptors have on a blood vessel?

Answer 49

Vasoconstriction

Question 50

In blood vessels that have both A1 and B2 receptors, at HIGH concentrations of adrenaline, which receptor will the adrenaline bind to? What effect does this have?

Answer 50

A1 Vasoconstriction

Question 51

In blood vessels that have both A1 and B2 receptors, which receptor will adrenaline preferentially bind to at normal physiological concentrations and what affect does this have?

Answer 51

B2 Vasodilation

Question 52

How does Activating B2 adrenoreceptors cause vasodilation of vascular smooth muscle?

Answer 52

G protein stimulates Adenylyl cyclase More cAMP PKA activated PKA Phosphorylates MLCK inhibiting it So MLC not phosphorylated preventing actin myosin interaction (no contraction)

Question 53

How does activating A1 adrenoreceptors cause vasoconstriction?

Answer 53

G protein stimulates IP3 (Inositol triphosphate) production IP3 stimulates SR to release Ca2+ Ca2+ interacts with Calmodulin Ca2+ - Calmodulin complex activates MLCK MLCK Phosphorylates MLC allowing myosin head to interact with actin CONTRACTION

Question 54

What affect do high amounts of metabolites have on vascular smooth muscle?

Answer 54

Vasodilation

Question 55

What receptors in the carotid sinus and aortic arch detect increased arterial blood pressure?

Answer 55

Baroreceptors

Question 56

What happens when Baroreceptors are stretched detecting increased blood pressure?

Answer 56

Fire AP to medulla Decreased sympathetic stimulation Vasodilation Bradycardia

Question 57

What is the baroreceptor reflex?

Answer 57

Maintains blood pressure over short periods Compensates for moment to moment changes in arterial BP

Question 58

What is the problem with the baroreceptor reflex?

Answer 58

With hypertension the baroreceptors re-set to a higher level

Question 59

What are the 3 categories of drugs that act on the ANS

Answer 59

Sympathomimetics Adrenoceptor antagonists Cholinergics

Question 60

What are sympathomimetic drugs?

Answer 60

Drugs that enhance the nerves of the sympathetic nervous system Alpha adrenoreceptor agonists Beta adrenoreceptor agonists

Question 61

What drug is administered in cardiac arrest and anaphylactic shock?

Answer 61

Adrenaline

Question 62

When adrenaline is administered in anaphylactic shock or cardiac arrest, which adrenoreceptor is being activated?

Answer 62

Alpha 1 (A1) Due to higher concentrations of adrenaline compared to normal physiological concentrations

Question 63

When there is cardiogenic shock/pump failure, DOBUTAMINE is given, what type of drug is this?

Answer 63

B1 agonist Sympathomimetic drug

Question 64

What affect does a B1 agonist (dobutamine) have on the heart?

Answer 64

Increased heart rate Increased strength of contraction

Question 65

When someone has asthma they are often treated with SALBUTAMOL, what type of drug is this?

Answer 65

B2 agonist Sympathomimetic

Question 66

How does the B2 agonist salbutamol help treat asthma?

Answer 66

Vasodilation of the smooth muscle Increased cAMP Inc PKA MLCK inhibited (K+ influx no Ca2+) Muscle relaxes

Question 67

What is an example of an alpha adrenoreceptor antagonist?

Answer 67

Prazosin

Question 68

What affect does an alpha 1 (A1) antagonist have on the body? Meachanism of action of Prazosin

Answer 68

Prevents noradrenaline binding to smooth muscle A1 receptors Prevents constriction so vasodilation happens

Question 69

What is a B-adrenoreceptor antagonist that is specifc to B1 receptor?

Answer 69

Atenolol

Question 70

What affect does the B1 selective adrenoreceptor antagonist Atenolol have on the body?

Answer 70

Affects the heart Prevents noradrenaline binding to B1 Slows heart rate Reduces force of contraction

Question 71

Propranolol is a non selective B1/B2 receptor antagonist, what affect will this have on the body?

Answer 71

Slows heart Reduces force of heart contraction Bronchial smooth muscle contraction (bronchoconstriction) Prevents noradrenaline binding to the B receptors

Question 72

What are cholinergics?

Answer 72

Muscarinic receptor agonists and antagonists

Question 73

How can I remember where the beta adrenoreceptors are found?

Answer 73

B1 in heart (only have 1 heart) B2 in lungs and (have 2 lungs)

Question 74

Where are alpha adrenoreceptors found?

Answer 74

Blood vessels

Question 75

What happens to blood vessels when there is: Increased noradrenaline? Decreased noradrenaline? What receptor is being activated more or less?

Answer 75

Increased noradrenaline = Vasoconstriction (increased activation of A1) Decreased noradrenaline = Vasodilation (Decreased activation of A1)