control of cardia output I

Question 1

cardiac output =

Answer 1

heart rate x stroke volume

Question 2

what is cardiac output CO

Answer 2

the volume of blood ejected bty each ventricle per minute

Question 3

what is heart rate HR

Answer 3

the number of contractions (beats) per minute

Question 4

what is stroke volume SV

Answer 4

the volume of blood ejected by each ventricle per beat

Question 5

compare the cardiac output of an athlete to a non athlete

Answer 5

a non athlete has a greater resting cardiac output, a lower resting heart rate and produces a greater cardiac output when exercising

Question 6

three pathways of innervaton of the heart

Answer 6

blood volume reflexes
autonomic
sympathetic via adrenal glands

Question 7

describe blood volume reflexes

Answer 7

baroreceptors in the wall of carotid artery and carotid body chemoreceptor travel along sensory nerve fibers to the cardioregulatory center and chemoreceptors in the medulla oblongata

Question 8

describe autonomic innervation of the heart

Answer 8

involuntary
parasympathetic nerve fibers end at the SAN. acetylcholine from vagus nerve
sympathetic nerve fibres hit the SAN and travel across the ehart. noradrenaline

Question 9

describe innervation of the heart via the adrenal glands

Answer 9

sympathetic

signal comes out cns to adrenal medulla, produces adrenaline and noradrenaline

Question 10

what is meant by chronotropic

Answer 10

increases the heart rate, cuts donwn the time that the SAN rests

Question 11

what does an increase in heart rate do to cardiac output

Answer 11

increases it

Question 12

what effect do noradrenaline and adrenaline have on the heart

Answer 12

positive chronotropic
stimulates the hyperpolarisation of ion channels at the SAN so more action potentials
(there is reduced repolarisation so the peak goes back up faster)

Question 13

what effecr does acetylcholine have on heart rate

Answer 13

slows it, ie negative chronotropic
shifts the threshold for an action potential to more hyperpolarise potentials via activated K+ channels to hyperpolarise.

Question 14

why do trained atheltes have lower heart rates

Answer 14

increased vagal tone

vagus nerve releases acetylcholine

Question 15

tachycardia

Answer 15

fast heart rate

Question 16

bradycardia

Answer 16

slow heart rate

Question 17

what is the end diastolic volume

Answer 17

the volume of blood in the ventricle at the end of loading or filling

Question 18

what is end systolic volume

Answer 18

the volume of blood at the end of a contraction and beginning of a filling
is the lowest volume of blood in the ventricle at any point in cardiac cycle

Question 19

what is the formula for stroke volume

Answer 19

EDV-ESV

end diastolic volume - end systolic volume

Question 20

what factors affect the end diastolic volume

Answer 20

preload- the amount of blood returned to the atria
contractility- the processes that control contraction of the heart
afterload- the resistance the blood faces as it leaves the ventricle

Question 21

what does preload depend on

Answer 21

the filling of the ventricles depends on the atrial filling which is determined by central venous pressure or venous return

Question 22

what does an increase in end diastolic volume lead to

Answer 22

an increase in the initial length of the cardiac muscle fibres (they become stretched) and this increases stroke volume and therefore cardiac output

Question 23

what is starlings law of the heart

Answer 23

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

Question 24

what three factors affect venous return/ central venous pressure

Answer 24

posture
muscle pump-constriction of veins by skeletal muscle
respiratory pump- inspiration creates an internal pressure difference . moves blood back to heart