cardiac output and control

Question 1

what is HR primarily determined by

Answer 1

autonomic influences on the SAN

Question 2

what are the 2 kinds of activity to the SAN and their purpose

Answer 2

parasympathetic - lowers heart rate

sympathetic- increases heart rate

Question 3

what is parasympathetic activity via

Answer 3

vagus nerve

Question 4

what is sympathetic activity via

Answer 4

cardiac sympathetic nerves

Question 5

what 2 hormones are released and by what

Answer 5

acetylcholine release promoted by parasympathetic

epinephrine release promoted by sympahtetic

Question 6

how does parasympathetic activity decrease heart rate -4 ways

Answer 6

decreased rate of depolarisation in the SAN
increased AVN delay
decreased contractibility
acetylcholine secretion

Question 7

how does sympathetic activity increase heart rate- 4 ways

Answer 7

increased rate of depolarisation in SAN
decreased AVN delay
increased contractibility
epinephrine secretion

Question 8

what is EDV

Answer 8

end diastolic volume

blood in ventricles after diastole (maximum ventricular volume)

Question 9

what is the frank starling law of the heart

Answer 9

a greater EDV will increase the contractile strength of the ventricles, increasing the stroke volume

Question 10

what is the stroke volume

Answer 10

EDV-ESV

amount of blood pumped by left ventricle in one contraction

Question 11

how is stroke volume intrinsically controlled

Answer 11

increased EDV will stretch the myocardium
sarcomeres increase in length and become more sensitive to Ca2+
stronger contraction

Question 12

what is cardiac output

Answer 12

volume of blood pumped by a ventricle in a minute

CO = HR X SV

Question 13

extrinsic control of stroke volume

Answer 13

sympathetic stimulation and epinephrine release increase contractibility of heart
increases affects of greater EDV even more

Question 14

what are baroreceptors

Answer 14

mechanoreceptors in the aortic arch that sense pressure changes as tension in arterial wall
they maintain BP at a constant level

Question 15

what is the haemorrhage baroreceptor reflex

Answer 15

1. blood loss lowers BP
2. baroreceptors detect drop in BP and fire APs to vasomotor centre of brain
3. increase sympathetic activity, decrease in parasympathetic activity
4. BP is increased to near initial value
5. baroreceptor reflex shuts off if BP increased to initial value