The Heart

Question 1

functions of the cardiovascular system

Answer 1

• transport o2 and co2
• carry digestion products to liver and nutrients to tissues
• carry wastes to kidneys
• carry hormones
• blood clotting
• fight infection
• temperature control

Question 2

what joins adjacent myocardial cells?

Answer 2

intercalating disks containing gap junctions

Question 3

what are gap junctions?

Answer 3

fluid filled channels that allow action potentials spread rapidly from cell to cell

Question 4

what initiates myocardial contraction?

Answer 4

extracellular Calcium

Question 5

what determines the heart rate?

Answer 5

the SA node

Question 6

what prevents action potentials from spreading to the ventricles from the atria?

Answer 6

fibrous layer - electrical insulator

Question 7

what are the 3 waves on an ECG?

Answer 7

P- atrial depolarization
QRS - ventricular depolarisation
T- ventricular repolarisation

Question 8

systole

Answer 8

contraction

Question 9

diastole

Answer 9

relaxation

Question 10

what is the stroke volume

Answer 10

volume of blood ejected by each ventricle during systole

Question 11

what is end-diastolic volume?

Answer 11

vol of blood in ventricle at the end of diastole

Question 12

what is the equation for cardiac output?

Answer 12

cardiac output = stroke volume x cardiac rate

Question 13

what is cardiac output at rest?

Answer 13

5.5 L/min

Question 14

what is the sympathetic division of the autonomic nervous system?

Answer 14

nerves release noradrenaline which binds to adrenergic receptors

Question 15

what is the parasympathetic division of the autonomic nervous system?

Answer 15

nerves release acetylcholine which binds to muscarinic acetylcholine receptors

Question 16

how does the sympathetic division affect the heartbeat?

Answer 16

noradrenaline binds to B adrenergic receptors and causes opening of HCN channels in pacemaker cells of the SA node

Question 17

what triggers spontaneous depolarizations?

Answer 17

HCN (Na and Ca) channels

Question 18

how does the parasympathetic division affect heartbeat?

Answer 18

acetylcholine binds to muscarinic acetylcholine receptors on SA node- opening of K channels hyperpolarizes cell membrane and inhibits HCN channels

Question 19

what slows the rate of depolarization of SA node and reduces heart rate?

Answer 19

parasympathetic nerves

Question 20

what increases heart rate during exercise?

Answer 20

reduced vagus nerve activity and increased sympathetic nerve stimulation

Question 21

what is the frank-starling law of the heart?

Answer 21

stroke volume = contractility = EDV

Larger the vol of blood in ventricle = larger vol of blood ejected

Question 22

what determines mean arterial pressure?

Answer 22

the volume of blood in arterial system

Question 23

what determines the rate of blood flow out of the arteries?

Answer 23

peripheral resistance

Question 24

what is the mean arterial pressure equation?

Answer 24

MAP = cardiac output x total peripheral resistance

Question 25

how does the body detect changes in blood pressure?

Answer 25

stretch sensitive mechanoreceptors (baroreceptors) become active

Question 26

how do baroreceptors affect blood pressure?

Answer 26

stretch stimulates sensory nerves in cardiovascular control centre in medulla oblongata which alters HR, SV, TPR

Question 27

How is total peripheral resistance regulated?

Answer 27

by vasodilation and vasoconstriction

Question 28

what does vasoconstriction in the kidneys do?

Answer 28

minimizes urine formation

Question 29

does vasoconstriction increase or decrease blood pressure?

Answer 29

increases

Question 30

how is blood pressure lowered?

Answer 30

vagus nerve reduces cardiac output, vasodilation decreases peripheral resistance, kidneys stimulated to increase water secretion

Question 31

what is the function of the baroreceptor reflex

Answer 31

to counter changes in blood pressure

Question 32

how do the kidneys help regulate blood volume?

Answer 32

long term - reabsorption of water and salt

Question 33

what is chronically elevated blood pressure known as?

Answer 33

hypertension- can be primary or secondary (occurs due to another condition ie diabetes)

Question 34

what drives filtration?

Answer 34

hydrostatic pressure

Question 35

what is colloid osmotic pressure?

Answer 35

osmotic pressure created by plasma which promotes movement of water out of tissue fluid into capillaries

Question 36

what is the net colloid osmotic pressure in the capillaries?

Answer 36

25 mmHg

Question 37

what are the starling forces?

Answer 37

opposing hydrostatic and osmotic pressures

Question 38

what part of the starling forces causes net filtration of fluid?

Answer 38

hydrostatic pressure

Question 39

what part of the starling forces causes net reabsorption of fluid back into capillaries?

Answer 39

colloid osmotic pressure

Question 40

what causes oedema?

Answer 40

an imbalance between absoprtion and filtration and poor lymphatic drainage

Question 41

three layers of blood vessels?

Answer 41

tunica externa, tunica media and tunica interna

Question 42

what is the tunica media of blood vessels composed of?

Answer 42

smooth muscle

Question 43

types of arteries?

Answer 43

muscular and elastic

Question 44

what is the difference between elastic and muscular arteries?

Answer 44

elastic arteries are made of elastin and expand and recoil | muscular have less elastin and more smooth muscle which regulates diameter of lumen

Question 45

is venous pressure higher or lower than arterial pressure?

Answer 45

much lower

Question 46

does smooth muscle contain sarcomeres?

Answer 46

no

Question 47

does SM contain more actin or myosin?

Answer 47

actin

Question 48

what determines the strength of smooth muscle contraction?

Answer 48

degree of opening of Ca channels caused by depolarisation

Question 49

what does calcium bind with in SM contraction?

Answer 49

calmodulin activates myosin light chain kinase

Question 50

what does MLCK do?

Answer 50

phosphorylates light chains in myosin head that drives contraction

Question 51

why is SM relaxation slow?

Answer 51

dephosphorylated myosin remains attached to actin for a period of time

Question 52

what does resistance to blood flow depend on?

Answer 52

the length and radium of blood vessels and viscosity of blood

Question 53

where is most of the blood in circulation?

Answer 53

veins and venules

Question 54

what is the MAP equation?

Answer 54

MAP = diastolic pressure + 1/3 (systole - diastole pressure)

Question 55

what is pulse pressure equation?

Answer 55

PP = systolic pressure - diastolic pressure