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Physiology > The Heart > Flashcards

The Heart Flashcards

1
Q

functions of the cardiovascular system

A
  • 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
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2
Q

what joins adjacent myocardial cells?

A

intercalating disks containing gap junctions

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3
Q

what are gap junctions?

A

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

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4
Q

what initiates myocardial contraction?

A

extracellular Calcium

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5
Q

what determines the heart rate?

A

the SA node

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6
Q

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

A

fibrous layer - electrical insulator

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7
Q

what are the 3 waves on an ECG?

A

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

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8
Q

systole

A

contraction

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9
Q

diastole

A

relaxation

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10
Q

what is the stroke volume

A

volume of blood ejected by each ventricle during systole

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11
Q

what is end-diastolic volume?

A

vol of blood in ventricle at the end of diastole

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12
Q

what is the equation for cardiac output?

A

cardiac output = stroke volume x cardiac rate

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13
Q

what is cardiac output at rest?

A

5.5 L/min

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14
Q

what is the sympathetic division of the autonomic nervous system?

A

nerves release noradrenaline which binds to adrenergic receptors

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15
Q

what is the parasympathetic division of the autonomic nervous system?

A

nerves release acetylcholine which binds to muscarinic acetylcholine receptors

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16
Q

how does the sympathetic division affect the heartbeat?

A

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

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17
Q

what triggers spontaneous depolarizations?

A

HCN (Na and Ca) channels

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18
Q

how does the parasympathetic division affect heartbeat?

A

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

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19
Q

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

A

parasympathetic nerves

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20
Q

what increases heart rate during exercise?

A

reduced vagus nerve activity and increased sympathetic nerve stimulation

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21
Q

what is the frank-starling law of the heart?

A

stroke volume = contractility = EDV

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

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22
Q

what determines mean arterial pressure?

A

the volume of blood in arterial system

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23
Q

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

A

peripheral resistance

24
Q

what is the mean arterial pressure equation?

A

MAP = cardiac output x total peripheral resistance

25
Q

how does the body detect changes in blood pressure?

A

stretch sensitive mechanoreceptors (baroreceptors) become active

26
Q

how do baroreceptors affect blood pressure?

A

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

27
Q

How is total peripheral resistance regulated?

A

by vasodilation and vasoconstriction

28
Q

what does vasoconstriction in the kidneys do?

A

minimizes urine formation

29
Q

does vasoconstriction increase or decrease blood pressure?

A

increases

30
Q

how is blood pressure lowered?

A

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

31
Q

what is the function of the baroreceptor reflex

A

to counter changes in blood pressure

32
Q

how do the kidneys help regulate blood volume?

A

long term - reabsorption of water and salt

33
Q

what is chronically elevated blood pressure known as?

A

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

34
Q

what drives filtration?

A

hydrostatic pressure

35
Q

what is colloid osmotic pressure?

A

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

36
Q

what is the net colloid osmotic pressure in the capillaries?

A

25 mmHg

37
Q

what are the starling forces?

A

opposing hydrostatic and osmotic pressures

38
Q

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

A

hydrostatic pressure

39
Q

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

A

colloid osmotic pressure

40
Q

what causes oedema?

A

an imbalance between absoprtion and filtration and poor lymphatic drainage

41
Q

three layers of blood vessels?

A

tunica externa, tunica media and tunica interna

42
Q

what is the tunica media of blood vessels composed of?

A

smooth muscle

43
Q

types of arteries?

A

muscular and elastic

44
Q

what is the difference between elastic and muscular arteries?

A

elastic arteries are made of elastin and expand and recoil

muscular have less elastin and more smooth muscle which regulates diameter of lumen

45
Q

is venous pressure higher or lower than arterial pressure?

A

much lower

46
Q

does smooth muscle contain sarcomeres?

A

no

47
Q

does SM contain more actin or myosin?

A

actin

48
Q

what determines the strength of smooth muscle contraction?

A

degree of opening of Ca channels caused by depolarisation

49
Q

what does calcium bind with in SM contraction?

A

calmodulin activates myosin light chain kinase

50
Q

what does MLCK do?

A

phosphorylates light chains in myosin head that drives contraction

51
Q

why is SM relaxation slow?

A

dephosphorylated myosin remains attached to actin for a period of time

52
Q

what does resistance to blood flow depend on?

A

the length and radium of blood vessels and viscosity of blood

53
Q

where is most of the blood in circulation?

A

veins and venules

54
Q

what is the MAP equation?

A

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

55
Q

what is pulse pressure equation?

A

PP = systolic pressure - diastolic pressure

Physiology (7 decks)

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