Physiology

Question 1

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

Answer 1

Autorhythmicity

The electrical impulses are generated from within the heart

Question 2

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

Answer 2

Sinus rhythm

Question 3

Where is the SA node?

Answer 3

Upper right atrium

Question 4

Do pacemaker cells have a stable resting membrane potential?

Answer 4

No, always drifting towards action potential

Question 5

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

Answer 5

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

Question 6

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

Answer 6

Rapid Ca influx (L-type channels)

Question 7

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

Answer 7

K efflux

Question 8

What course does electrical impulses follow through the heart?

Answer 8

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

Question 9

What type of junction are electrical signals spread via?

Answer 9

Gap junctions

Question 10

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

Answer 10

AV node

Question 11

Describe the phases of an action potential in myocytes.

Answer 11

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

Question 12

How does symp/parasymp activity affect the heart rate?

Answer 12

Symp: increases it
Parasymp: decreases it

Question 13

What is the normal range for heart rate?

Answer 13

60-100bpm

Question 14

What is used to speed up the heart rate?

Answer 14

Atropine

Question 15

Which receptors does noradrenaline from sympathetic stimulation act upon?

Answer 15

B1

Question 16

Which wave on an ECG indicates atrial depolarisation?

Answer 16

P wave

Question 17

What does the QRS complex indicate?

Answer 17

Ventricular depolarisation

Question 18

What does the T wave indicate?

Answer 18

Ventricular repolarisation

Question 19

Why is atrial repolarisation not seen on an ECG?

Answer 19

Masked by the QRS complex

Question 20

What does the PR interval show?

Answer 20

AV nodal delay

Question 21

Which types of muscle are striated?

Answer 21

Cardiac and skeletal

Question 22

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

Answer 22

Desmosomes

Question 23

What is required for contraction of muscles?

Answer 23

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

Question 24

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

Answer 24

Sarcoplasmic reticulum

Question 25

What happens to Ca during diastole (heart relaxed)?

Answer 25

Is pumped back into the SR

Question 26

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

Answer 26

Cardiac only

Question 27

What is the refractory period and what is its purpose?

Answer 27

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

Question 28

What is the frank-starling hypothesis?

Answer 28

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

Question 29

What is the after load?

Answer 29

The resistance against high the heart is pumping

Question 30

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

Answer 30

The amount of blood ejected from the ventricles per minute | CO = HR x SV

Question 31

What creates the first and second heart sounds?

Answer 31

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

Question 32

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

Answer 32

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

Question 33

Describe the cardiac cycle

Answer 33

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

Question 34

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

Answer 34

``` Lub = beginning of systole Dub = beginning of diastole (d=d) ```

Question 35

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

Answer 35

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

Question 36

What are the major resistance vessels?

Answer 36

Arterioles

Question 37

What are used for the short term regulation of BP?

Answer 37

Baroreceptors

Question 38

What is postural hypotension?

Answer 38

Brief drop in BP when someone stands up

Question 39

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

Answer 39

Vasoconstriction, Increased HR, Increased SV

Question 40

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

Answer 40

RAAS Natriuretic Peptides ADH

Question 41

What is the process of RAAS?

Answer 41

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

Question 42

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

Answer 42

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

Question 43

What is the effect of ADH on the blood pressure?

Answer 43

Increases water retention in the kidneys - increase BP

Question 44

What hormones cause vasoconstriction?

Answer 44

Angiotensin II, Adrenaline, ADH

Question 45

What adrenoceptors does adrenaline from the adrenal medulla act upon?

Answer 45

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

Question 46

Which chemical factors cause localised vasodilation?

Answer 46

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

Question 47

What chemical factors cause localised vasoconstriction?

Answer 47

Endothelin, Leukotrienes, Serotonin

Question 48

What increases venous return?

Answer 48

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

Question 49

What is the effect of exercise on pulse pressure?

Answer 49

It increases (systole increases and diastole decreases)

Question 50

What is hypovolaemic shock?

Answer 50

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

Question 51

What are the 4 types of shock?

Answer 51

Hypovolaemic, Cardiogenic, Obstructive, Distributive

Question 52

What is hypovolaemic shock?

Answer 52

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

Question 53

What is cardiogenic shock?

Answer 53

Decreased cardiac contractility causing hypotension and loss of tissue perfusion

Question 54

What causes obstructive shock and how?

Answer 54

Tension pneumothorax | Increased interthoracic pressure decreasing venous return and thus cardiac output

Question 55

What causes distributive shock?

Answer 55

Neurogenic loss of sympathetic tone which decreases BP and thus CO

Question 56

How is cerebral blood pressure maintained?

Answer 56

Myogenic response