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Cardio > Physiology > Flashcards

Physiology Flashcards

1
Q

What feature of the heart allows in to continue beating in the absence of external stimuli?

A

Autorhythmicity

The electrical impulses are generated from within the heart

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2
Q

What kind of rhythm is a heart beating normally said to be in?

A

Sinus rhythm

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3
Q

Where is the SA node?

A

Upper right atrium

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4
Q

Do pacemaker cells have a stable resting membrane potential?

A

No, always drifting towards action potential

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5
Q

What ions are moving into the cell during the pacemaker potential phase?

A 
Funny current (Na + K influx)
Ca influx (T-type channels)
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6
Q

What occurs to the ions during depolarisation of the pacemaker cells?

A

Rapid Ca influx (L-type channels)

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7
Q

What occurs during the repolarisation of pacemaker cells in the SA node?

A

K efflux

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8
Q

What course does electrical impulses follow through the heart?

A 
SA node,
Across right atrium by cell-cell conduction
AV node (rate limiting)
Bundle of His
Right and left branches
Purkinje fibres
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9
Q

What type of junction are electrical signals spread via?

A

Gap junctions

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10
Q

What is the only point of electrical activity spread between the atria and the ventricles?

A

AV node

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11
Q

Describe the phases of an action potential in myocytes.

A 
Phase 0 (rising phase): Fast Na influx
Phase 1: K efflux
Phase 2 (plateau phase): Ca influx
Phase 3: K efflux
Phase 4: resting membrane potential
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12
Q

How does symp/parasymp activity affect the heart rate?

A

Symp: increases it
Parasymp: decreases it

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13
Q

What is the normal range for heart rate?

A

60-100bpm

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14
Q

What is used to speed up the heart rate?

A

Atropine

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15
Q

Which receptors does noradrenaline from sympathetic stimulation act upon?

A

B1

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16
Q

Which wave on an ECG indicates atrial depolarisation?

A

P wave

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17
Q

What does the QRS complex indicate?

A

Ventricular depolarisation

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18
Q

What does the T wave indicate?

A

Ventricular repolarisation

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19
Q

Why is atrial repolarisation not seen on an ECG?

A

Masked by the QRS complex

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20
Q

What does the PR interval show?

A

AV nodal delay

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21
Q

Which types of muscle are striated?

A

Cardiac and skeletal

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22
Q

What provide adhesion between cardiac muscle cells for when tension develops?

A

Desmosomes

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23
Q

What is required for contraction of muscles?

A

ATP
Ca
(to allow Actin + myosin to slide of each other)

24
Q

Where does most of Ca for contraction in muscle cells come from?

A

Sarcoplasmic reticulum

25
Q

What happens to Ca during diastole (heart relaxed)?

A

Is pumped back into the SR

26
Q

What types of muscle cells does a refractory period occur in?

A

Cardiac only

27
Q

What is the refractory period and what is its purpose?

A

The time following an action potential where it is not possible to produce another action potential, to prevent generation of tetanic contractions

28
Q

What is the frank-starling hypothesis?

A

The more the ventricle is filled during diastole (the end diastolic volume), the greater the amount fo blood ejected during systole (the stroke volume)

29
Q

What is the after load?

A

The resistance against high the heart is pumping

30
Q

What is the cardiac output and how do you calculate it?

A

The amount of blood ejected from the ventricles per minute

CO = HR x SV

31
Q

What creates the first and second heart sounds?

A

First ‘lub’: closure of tricuspid and mitral valves at start of systole
Second ‘dub’: closure of aortic and pulmonary valves at the end of systole

32
Q

What is the JVP and what type of waveform is it?

A

Bifid pulsation

Caused by increased pressure in the right atrium and a backlog of blood

33
Q

Describe the cardiac cycle

A

Filling of atria + ventricles
Contraction of atria + increased filling of ventricles
Closure of tricuspid and mitral valves - lub
Contraction of ventricular muscle and increased pressure in the ventricles
Opening of aortic and pulmonary valves
Release of contents of ventricles
Closure of aortic + pulmonary valves - dub
Filling of atria
Opening of tricuspid + bicuspid valves

34
Q

Which phases of the cardiac cycle do the lub and dub indicate

A 
Lub = beginning of systole
Dub = beginning of diastole (d=d)
35
Q

How do you calculate the mean arterial blood pressure (MAP)?

A 
2D+S/3
or
D + 1/3(S-D)
or
MAP = SV x HR x SVR
36
Q

What are the major resistance vessels?

A

Arterioles

37
Q

What are used for the short term regulation of BP?

A

Baroreceptors

38
Q

What is postural hypotension?

A

Brief drop in BP when someone stands up

39
Q

What effect does a short-term drop in BP cause?

A

Vasoconstriction,
Increased HR,
Increased SV

40
Q

What hormones influence the extracellular (blood) fluid volume long term?

A

RAAS
Natriuretic Peptides
ADH

41
Q

What is the process of RAAS?

A

Renin released from kidneys in response to decreased pressure in renal arteries
Stimulates formation of angiotensin I
Angiotensin converting enzyme (ACE) stimulates conversion of Angiotensin I to angiotensin II
Angiotensin II stimulates release of aldosterone
Aldosterone increases Na and water retention in the kidneys (osmosis of water following Na) - increases BP

42
Q

What is the effect of natriuretic peptides (NPs) on the blood pressure?

A

Cause Na and water excretion in the kidneys (opposite of RAAS) to decrease BP

43
Q

What is the effect of ADH on the blood pressure?

A

Increases water retention in the kidneys - increase BP

44
Q

What hormones cause vasoconstriction?

A

Angiotensin II,
Adrenaline,
ADH

45
Q

What adrenoceptors does adrenaline from the adrenal medulla act upon?

A

Alpha (to cause vasoconstriction)
B2 (for vasodilation)
Alpha adrenoceptors are predominant in arterioles so has vasconstrictory effect

46
Q

Which chemical factors cause localised vasodilation?

A 
Decreased O2,
Increased CO2,
Increased [H+] (decreased pH)
Adenosine 
Nitric Oxide (NO)
Bradykinin,
Histamine
47
Q

What chemical factors cause localised vasoconstriction?

A

Endothelin,
Leukotrienes,
Serotonin

48
Q

What increases venous return?

A

Respiratory pump,
Skeletal muscle pump,
Venomotor tone,
Blood volume

49
Q

What is the effect of exercise on pulse pressure?

A

It increases (systole increases and diastole decreases)

50
Q

What is hypovolaemic shock?

A

Loss or decreased blood volume resulting in inadequate cardiac output for tissue perfusion

51
Q

What are the 4 types of shock?

A

Hypovolaemic,
Cardiogenic,
Obstructive,
Distributive

52
Q

What is hypovolaemic shock?

A

Loss or decreased blood volume resulting in inadequate cardiac output for tissue perfusion

53
Q

What is cardiogenic shock?

A

Decreased cardiac contractility causing hypotension and loss of tissue perfusion

54
Q

What causes obstructive shock and how?

A

Tension pneumothorax

Increased interthoracic pressure decreasing venous return and thus cardiac output

55
Q

What causes distributive shock?

A

Neurogenic loss of sympathetic tone which decreases BP and thus CO

56
Q

How is cerebral blood pressure maintained?

A

Myogenic response

Cardio (10 decks)

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