regulation of stroke volume and heart rate

Question 1

how does sympathetic nervous system affect heart rate

Answer 1

release noradrenaline which acts on b1 receptors on sinoatrial node

increased slope of pacemaker potential - increases HR

Question 2

how does parasympathetic nervous system affect heart rate

Answer 2

vagus nerve releases Ach which acts on muscarinic receptors on SA node

hyperpolarises cells and decreases slope of pacemaker potential - decreases HR

Question 3

starlings law

Answer 3

energy of contraction is proportional to the initial length of cardiac muscle fibre

Question 4

what is preload affected by

Answer 4

end diastolic volume

Question 5

how does EDV affect preload

Answer 5

inc venous return - inc EDC and so inc SV

dec venous return - dec EDV and so dec SV

Question 6

afterload

Answer 6

is the load against which the muscle tries to contract

Question 7

what if afterload set by

Answer 7

afterload is set by the aterial pressure against which blood is expelled - total peripheral resistance

Question 8

increasing TPR

Answer 8

= stroke volume goes down

Question 9

factors affecting stroke volume

Answer 9

preload
afterload
neural
pathological

Question 10

sympathetic effects on stroke volume

Answer 10

noradrenaline actts on B1 receptors on myocytes

increase contractility to give stronger (but shorter) contraction

Question 11

parasympathetic effect on SV

Answer 11

little effect
(vagus nerve does not innervate ventricular muscle)

Question 12

hypercalaemic effect on graph

Answer 12

shifts curve up and left

Question 13

hypocalcaemi effect on graph

Answer 13

shifts curve down and right

Question 14

ischaemia effect on graph

Answer 14

shifts curve down and right

Question 15

CO =

Answer 15

HR x SV