Lecture 8 -control And Regulation Of Contraction

Question 1

How do you measure strength?

Answer 1

You look at the volume of blood that is ejected

Question 2

What does the sympathetic nervous system do to the heart?

Answer 2

Increases heart rate as it innervates the nodes of the cell

Question 3

What do the right sympathetic nerves do?

Answer 3

Innervates the SA node and causes the heart rate to go up

Question 4

What is a positive chronotropic affect?

Answer 4

Increase in heart rate

Question 5

What do the left side of the sympathetic nerves do?

Answer 5

Innervates the ventricular muscle which increases the stroke volume (increasing contractility)

Question 6

What does the parasympathetic nervous system do to the heart?

Answer 6

Decreases heart rate

Question 7

What does the right side of the parasympathetic nerves do?

Answer 7

Innervates the SA node

Question 8

What does the left side parasympathetic nerves do?

Answer 8

Innervates the AV node

Question 9

Can parasympathetic innervation happen in the ventricular muscle?

Answer 9

No only in the nodal tissues

Question 10

What is a negative chronotropic affect?

Answer 10

Decrease in heart rate

Question 11

What type of receptors do sympathetic nerve cells have?

Answer 11

Beta 1 receptors

Question 12

What does sympathetic stimulation do to the regulation of heart rate?

Answer 12

Depolarises the SA node and increases the rate of depolarisation - depolarises the pacemaker of the cell

Question 13

What happens when the rate of depolarisation increases?

Answer 13

Calcium channels are opened quicker as you have reached the threshold more quickly - more action potentials

Question 14

What receptors are involved in the parasympathetic regulation of heart rate? And what is the neurotransmitter involved?

Answer 14

M2 muscarinic receptors and acetylcholine

Question 15

What does parasympathetic stimulation do to the SA node (pacemaker)?

Answer 15

Hyperpolarises the cell and slows the heart rate - membrane potential becomes more negative

Question 16

What happens when there is a slower depolarisation?

Answer 16

Means it takes longer to reach the threshold so the calcium channels don’t open as quick which decreases the heart rate

Question 17

What drug blocks the muscarinic receptors?

Answer 17

Atropine

Question 18

What does Adenylyl cyclase reduce?

Answer 18

Cyclic AMP and produces PKA

Question 19

What does PKA phosphorylate?

Answer 19

The voltage operating calcium channel (VOC) so ca2+ channels activate quicker

Question 20

What protein is the muscarinic receptor linked to?

Answer 20

GI protein which inhibits Adenylyl cyclase

Question 21

What happens to the betagamma subunit in the parasympathetic system?

Answer 21

The betagamma subunit separates from the alpha subunit and the alpha subunit goes off in the membrane and binds and activates the K+ channel

Question 22

What happens when the K+ channel is activated by the alpha subunit?

Answer 22

The k+ ions leave the cell and the cell repolarises which is why the parasympathetic stimulation hyperpolarises the SA and AV node

Question 23

Why in the sympathetic response are the intracellular mechanisms more gradual?

Answer 23

Because cAMP levels have to build up, little NE is released during each cardiac cycle

Question 24

What is the sympathetic response unable to do?

Answer 24

To alter the cardiac behaviour very much within one cardiac cycle

Question 25

Why is the parasympathetic response rapid?

Answer 25

Because of the direct activation of K+ channels by betagamma subunit (there is no second messenger required)

Question 26

What are vagus nerves able to do in the parasympathetic response?

Answer 26

Able to exert beat-by-beat control of heart rate - removal of vagus results in increase in heart rate

Question 27

What stimulation dominates at rest?

Answer 27

The parasympathetic

Question 28

Extrinsic contraction?

Answer 28

Outside influence on the muscle cells e.g. neurotransmitter or a hormone causes contractility

Question 29

Intrinsic contraction?

Answer 29

Inherent in the muscle cells, a unique property of cardiac muscles in the cell

Question 30

Positive inotropic effect?

Answer 30

Increase stroke volume

Question 31

Positive chronotropic effect?

Answer 31

Increased heart rate

Question 32

What is an increase in contractility associated with?

Answer 32

An increase in ca2+ ion concentration - have to have more calcium ions as calcium ions trigger contraction

Question 33

What happens when there is an increased strength of contraction from a build up of pressure?

Answer 33

Stroke volume goes up

Question 34

How does activation of beta 1 receptors result in more calcium and stronger contraction?

Answer 34

Because PKA phosphorylates the voltage operating calcium channel so you get more trigger ca2+ which means more CICR and stronger contractions

Question 35

More CICR and stronger contractions =?

Answer 35

Stroke volume increases and contractility increases

Question 36

What needs to happen for the muscle to relax?

Answer 36

Cytoplasm needs to get ride of ca2+ which occurs by sympathetic stimulation when PKA phosphorylates phospholamban

Question 37

What happens when phospholamban is phosphorylated?

Answer 37

It speeds up the SERCA pump and you get an increase rate of pumping the ca2+ ions back out the cytoplasm

Question 38

Where are RYR receptors located?

Answer 38

Underneath the calcium channels

Question 39

What does maximum sympathies stimulation =

Answer 39

An increase in HR and SV independently

Question 40

What are class 2 - beta blockers known as?

Answer 40

Negative inotropic

Question 41

What do class 5 - cardiac glycosides do?

Answer 41

Inhibit the Na+/K+ ATPase pump

Question 42

What happens when the Na+/K+ATPase pump is inhibited?

Answer 42

Means the intracellular Na+ concentration rises in the cell which depolarises the cell

Question 43

How does the cell keep the Na+ levels normal when the Na/K+ ATPase pump is inhibited?

Answer 43

The Na/Ca exchanger reverses its led to get rid of the Na+ ions so Ca2+ will enter the cell - triggering a contraction

Question 44

What are class 5 - cardiac glycosides?

Answer 44

Positive ionotropes

Question 45

What is the mechanism for intrinsic regulation of stroke volume?

Answer 45

Frank-starling mechanism

Question 46

What does an increased filling pressure of the atria or the ventricles lead to?

Answer 46

An increase in end diastolic volume (the volume in the atria before contraction)

Question 47

What does an increase in filling pressure lead to?

Answer 47

An increase in EDV (end diastolic volume) which leads to an increase stretch int eh cardiac muscle which leads to an increase force of contraction