CVS physiology

Question 1

What causes the rapid depolarisation of non-pacemaker cells

Answer 1

Na+ influx (Na+ voltage gated channels open during depolarisation phase)

Question 2

What maintains the resting membrane potential of non-pacemaker cells?

Answer 2

high resting permeability to K+

Question 3

What causes the initial depolarisation of non-pacemaker cells?

Answer 3

Increased permeability to Na+ voltage gated

(depolarisation is rapid)

NOT funny If channels

Question 4

What maintains the plateau phase of action potential in non-pacemaker cells

Answer 4

L-type Calcium channels open

decreases permeability to K+

Question 5

Repolarisation phase of non-pacemaker cells

Answer 5

decreased permeability to Ca2+ (L-type)

increased permeability to K+

Question 6

What causes the action potential of pacemaker cells?

Answer 6

L-type Ca2+ channels

Question 7

What is responsible for the pacemaker potential of pacemaker cells?

Answer 7

• Gradual decrease in permeability to K+
• Early increase in permeability to Na+ (If)
• Late increase in permeability to Ca2 (T-type)

Question 8

How will the adminstration of Ca2+ channel blockers effect the pumping activity of the heart?

Answer 8

• voltage gated Ca2+ are involved in the Action potentials of pacemaker and non-pacemaker cells
• Ca2+ blockers will reduce the speed that Ca2+ enters the cell and reduce the total concentration in others
  Will reduce HR and strength of contraction

Question 9

Hypercalcaemia (high plasma Ca2+) effect on the pumping activity of the heart

Answer 9

• Increases the HR and strength of contraction
• Increases the concentration gradient for Ca2+ entering the cell - so it enters faster and more enters

Question 10

How is skeletal muscle different from cardiac muscle?

Answer 10

• True syncytium - mutiple cells are fused together to form a large muscle fibre
• no gap junctions (hence true syncytium)
• AP is short (2-5ms)
• Short refractory periond
• Tetanic contraction
• Relies on the release on intracellular calcium which is releases via the propagation of Na+ cells

Question 11

Cardiac muscle forms a functional syncytium

a. true
b.false

Answer 11

a. true

• there is no fusion between cells
• they are connected by gap junctions (electrically) and desmosomes (physically)
• can co-ordinate activity despite being separate cells

Question 12

Gap junctions

Answer 12

• connect the cell electrically
• cytoplasm to cytoplasm - allows depolarisation to spread between cells

Question 13

Desmosomes

Answer 13

stich cardiac muscle cells together - so they can contract as one big muscle

Question 14

Length of action potential in cardiac muscle cells

Answer 14

250ms

long action potential (plateau phase)
no tetanus (heart needs time to fill with blood)

Question 15

Why is the AP in cardiac muscle cells so long (250ms)?

Answer 15

• Ca2+ floods in from outside the cell - you can modulate how much Ca2+ comes into the cell from the outside -> long plateau phase (where Ca2+ is coming in)

compared to skeletal muscle where - Ca2+ from sarcoplasmic recticulum is always enough to saturate binding sites on troponin and bring about a full twitch contraction

Question 16

the effect of hyperkalaemia (high plasma K+ on the pumping effect of the heart)

Answer 16

• depolarises myocardial cells and trigger spontaneous uncordinated contraction (fibrilation)
• depolarisation reduces the electrical gradient for positive ions entering the cell and therefore slows down thhe conduction of AP
• this may lead to conduction failure through AV node failure and depolarisation in the atria never reachs ventricles (heart block)

-> hypokalaemia has the same effect

Question 17

high temperature will increase the HR

a. true
b. false

Answer 17

a. true

Question 18

transmural necrosis

Answer 18

necrosis that involves full thickness of myocardium (all layers of myocardium)

(*ST segment elevation - STEMI -MI) - Acute coronary syndrome

lumen completely occluded

Question 19

Stemi

Answer 19

• ST segment is elevated
• all layers of myocardium involved (transmural necrosis)

Question 20

non-stemi

Answer 20

non-raised ST segment - vessel is not completely occluded/not all layers of myocardium involved

Question 21

chronotrophic

Answer 21

influence on HEART RATE

sympathetic NS (positive chronotrophic action)

Question 22

ionotrophic

Answer 22

influence on FORCE or SPEED of contraction

Sympathetic NS (has a positive ionotrophic effect) v parasympathetic has NO EFFECT on force/strength of contraction

Question 23

Veins have a thin tunica media compared to arteries

a. true
b. false

Answer 23

a. true

Question 24

Properities of veins

Answer 24

• thin tunica media
• big diameter
• low pressure (5-10mmHg)
• Large lumen
• capacitance vessels (2/3s /70% of blood flow)

Question 25

how do veins control venous return

Answer 25

* skeletal muscle pump * respiratory pump * valves (tunica intima forms valves that prevent the backflow) * Smooth muscle (in tunica media) venoconstriction - increased sympathetic tne

Question 26

3 factors that influence SV

Answer 26

1. pre-load (EDV/venous return) 2. contractility (SNS,ions) 3. afterload (TPR, stenosis, plaques)

Question 27

stroke volume

Answer 27

m/pumped out per beat EDV-ESV

Question 28

layers of blood vessel from inside to outside

Answer 28

* tunica intima (endothelial lining/sub-endothelial) * internal elastic lamina (proteins, collagen, fibrin) * Tunica media (smooth muscle) * External elastic lamina (stretch/recoil) * Tunica adventitia (dense irregular connective tissue)

Question 29

vasa vasorum

Answer 29

small blood vessels - provide nourishment to tunica adventitia and media

Question 30

Part blood vessel layer than is SMALLER in arteries than veins a. elastic lamina b. tunica media c. tunica adventitia e. internal elastic lamina

Answer 30

c. tunica adventitia the tunica adventitia is THICKER in veins

Question 31

arterioles have a small lumen a. true b. false

Answer 31

a. true

Question 32

velocity is related to total cross-sectional area a. true b. false

Answer 32

a. true (velocity fastest in aorta - which has the SMALLEST cross sectional area)

Question 33

capillaries have the largest cross-sectional area a. true b. false

Answer 33

a. true (and slowest velocity - needed for exchange)

Question 34

standing up makes it more difficult to push blood back to the heart a. true b. false

Answer 34

b. false gravity is pushing down on blood on both sides equally - cancel each other out * but gravity does affect blood vessels -> (veins - capacitance vessels)

Question 35

rough estimate of Central Venous Presssure

Answer 35

Raised jugular pressure (JVP) - could indicate high BP

Question 36

How does the respiratory pump work?

Answer 36

* When we inspire (the pressure in the thorax becomes negative) * Positive pressure below gets transmitted to the vessels causing larger pressure gradient pushing blood back to the heart * increasing venous return * if breathing faster + deeper - helps increase venous return and offset any V/Q mismatch

Question 37

factors affecting pressure and flow in the veins

Answer 37

a. gravity b. skeletal muscle pump c. respiratory pump d. venomotor tone e. difference in PRESSURE gradient /systemic filling pressure - pressure transmitted through ventricles to veins

Question 38

when taking blood pressure manually and cuff pressure is increased until silence why is it silent?

Answer 38

artery is completely occluded and you can hear nothing - silence 1st sound - tapping - systolic silence - normal - diastolic

Question 39

korotkoff sounds

Answer 39

**manual BP** 1st artery is occluded -> silence 1. tapping - systolic 2. silence - diastolic

Question 40

disadvantages of manual BP

Answer 40

* discontinuous (snap shot in time) * accuracy - needs calibrated/right size * care and skill required

Question 41

advantages of manual BP

Answer 41

* non-invasive * cheap * useful screening toool for hypertension

Question 42

what do automatic BP machines measure

Answer 42

oscillations instead of sounds (vibrations generated from turbulent blood flow) turbulent blood flow creates vibrations in blood vessel wall max vobrations occur at MAP

Question 43

what maintains driving arterial pressure during diastole

Answer 43

elastic recoil of arteries produces dicrotic notch

Question 44

if the velocity of ejection of blood is increased what happens to systolic and diastolic BP

Answer 44

* systolic BP increases * diastolic BP decreases (less elastic energy used to push blood along column. Blood pumped quickly, less time for aorta to stretch)

Question 45

What happens to systolic and diastolic Blood pressure if the elasticity of arteries decreases?

Answer 45

* systole increases * diastole decreases (aorta less able to act as a pressure resovoir) less recoil maintaining pressure

Question 46

factors affecting pressure in arteries

Answer 46

1. velocity of ejection 2. elasticity of arteries 3. TPR 4. SV (contractility)

Question 47

if TPR increases , diastolic pressure increases a. true b. false

Answer 47

a. true arterioles constrict - it is harder to push blood (falling phase will be more gradual = high diastolic pressure)

Question 48

if TPR is reduced , diastolic pressure will be reduced a. true b. false

Answer 48

a. true dilated arterioles - falling phase of pressure will be steeper

Question 49

veins are susceptible to external forces because ?

Answer 49

they have thin , distensible walls , that stretch or collaspe easily

Question 50

difference in pressure is the main factor needed to push blood back to the heart a. true b. false

Answer 50

a. true

Question 51

continuous capillaries

Answer 51

either * No clefts or pores (e.g. blood brain barrier) * Clefts alone (most capillaries/muscles)

Question 52

capillaries in the brain

Answer 52

continuous capillaries - with no clefts of pores (BBB)

Question 53

Fenestrated capillaries

Answer 53

* have CLEFTS and PORES * kidney and intestines * fluid exchange speciality

Question 54

type of capillaries in kidneys

Answer 54

fenestrated (has clefts and pores)

Question 55

discontinuous capillaries

Answer 55

* found in LIVER * clefts + MASSIVE pores * allows large proteins to cross

Question 56

why is diffusion perfect for gas exchange?

Answer 56

* self-regulating * non-saturable (like transport proteins) * non-polar substances (co2 and 02) can freely cross the phospholipid bi-layer

Question 57

Forces that pull water out of the capillary

Answer 57

* hydrostatic pressure of capillary * osmotic pressure of ISF

Question 58

Forces that pull water into the capillary

Answer 58

* osmostic pressure of capillary * hydrostatic pressure of ISF (usually 0)

Question 59

Bulk flow is determined by starlings forces a. true b. false

Answer 59

a. true Balance Difference in hydrostatic pressure - difference in osmostic pressure

Question 60

over a day how much fluid is lost and gained

Answer 60

*20L lost to hydrostatic pressure * 17L pulled back in via osmotic * 3L drains to lymph nodes * and returned to venous sytem

Question 61

how might the lymphatic system be overwhelemd

Answer 61

* raised CVP pressure * Left sides Heart failure - blood accumulates in lungs (increased hydrostatic pressure) * lymphatic obstruction * hypoproteinaemia (low protein) - kidney disease (protein leaks out into urine)/liver failure (doesnt synthesis protein) * increased permeability of capillaries

Question 62

capillaries do not have smooth muscle a. true b. false

Answer 62

a. true

Question 63

poisaelles law

Answer 63

resistance * viscosity * lenght * radius (power of 4) *radius change has a big effect on flow

Question 64

MAP =

Answer 64

CO x TPR (both are unrelated)

Question 65

two effects of varying the radius of arterioles

Answer 65

1. Regional redirection of blood flow 2. TPR - therefore regulating MAP

Question 66

Concerning the arterial baroreflex: Rising from a sitting to a standing position will cause a reflex increase in heart rate and total peripheral resistance. a. true b. false

Answer 66

True. But do you understand the mechanism? Standing causes pooling of blood in the venules of the feet and legs. This reduces end diastolic volume and therefore preload, stroke volume, cardiac output and mean arterial pressure. This fall in blood pressure is sensed by the arterial baroreceptors which trigger a reflex increase in, amongst other things, heart rate and total peripheral resistance to restore blood pressure.

Question 67

Concerning the electrical activity of the heart: The atrioventricular node is the only electrically conducting region connecting the atria and the ventricles. a.true b. false

Answer 67

True. The atria and the ventricles are separated by the non-conducting annulus fibrosus, except for the very slow-conducting atrioventricular node.

Question 68

Concerning the cardiac cycle: Most of the stroke volume leaves the ventricle during the first third of systole. a. true b. false

Answer 68

True. This is the rapid ejection phase.

Question 69

Concerning the pumping ability of the heart: Cutting the sympathetic and parasympathetic innervation of the sinoatrial node will cause an increase in resting heart rate. a. true b. false

Answer 69

True. The fastest (and therefore the) pacemaker cells of the heart have an inherent rate of about 100 beats per minute. This can be speeded up by the sympathetic system or slowed down by the parasympathetic system. At rest, the parasympathetic system dominates and so the heart is said to be under vagal restraint, giving the resting heart rate of about 70 beats per minute.

Question 70

Regarding control of the peripheral circulation: The endothelium has an important role in the control of the peripheral circulation. a. true b. false

Answer 70

True. Endothelial cells have a key role in sensing metabolite concentrations and releasing autocrine agents such as EDRF (NO) to enable the intrinsic control of blood flow in a vascular bed.

Question 71

Concerning the cardiac cycle: The left ventricular pressure is approximately 80 mmHg during diastole. a. true b. false

Answer 71

False. During diastole (the filling phase), the pressure in the left ventricle is very low – maybe even 0mmHg.

Question 72

Concerning the electrical activity of the heart: The QRS complex immediately precedes ventricular contraction. a. true b. false

Answer 72

True. The QRS complex is created by the wave of depolarization spreading through the ventricle, which in turn triggers ventricular contraction.

Question 73

Concerning the pumping ability of the heart: Increased venous return causes an increased stroke volume. a. true b. false

Answer 73

True. In vivo, increased venous return during the filling phase increases end diastolic volume which increases preload on the heart. Starling’s law tells you that this will cause an increased strength of contraction and therefore increases stroke volume.

Question 74

Concerning the electrical activity of the heart: The refractory period of the action potential is much shorter than the contraction it produces. a. true b. false

Answer 74

False. Unlike skeletal muscle, because of its long action potential the refractory period of cardiac muscle is almost as long as the twitch contraction it evokes. The result is that the cardiac muscle must relax before it can contract again. It cannot exhibit a tetanic contraction.

Question 75

Concerning the electrical activity of the heart: A gradual opening of leaky K+ channels contributes to the pacemaker potential. a. true b,. false

Answer 75

False. A gradual closing of K+ channels is one of the factors that contributes to the pacemaker potentials – the others being opening of the “funny” Na+ channels and T-type Ca2+ channels. Gradual opening of K+ channels would hyperpolarize the cell.

Question 76

Concerning the vascular system: A low concentration of protein in the blood (hypoproteinemia) may cause oedema. a. true b. false

Answer 76

True. In the periphery water is lost from the capillaries through the hydrostatic pressure gradient. This creates an osmotic gradient in the opposite direction which draws water back into the capillary. If the concentration of protein in the plasma is low, this osmotic gradient cannot develop and so less fluid is re-absorbed.

Question 77

Concerning the vascular system: The smooth muscle surrounding the arterioles of the coronary circulation expresses beta 2 receptors. a. true b. false

Answer 77

True. The heart and skeletal muscle are two locations in which the smooth muscle surrounding arterioles expresses many beta 2 receptors. These are coupled to second messenger pathways that relax the smooth muscle and therefore cause arteriolar dilation. This increases blood flow and contributes to the redirection of blood flow to these areas during exercise.

Question 78

The heart and skeletal muscle are two locations in which the smooth muscle surrounding arterioles expresses many beta 2 receptors. a. true b. false

Answer 78

True hese are coupled to second messenger pathways that relax the smooth muscle and therefore cause arteriolar dilation. This increases blood flow and contributes to the redirection of blood flow to these areas during exercise.

Question 79

Regarding control of the peripheral circulation: Metabolic autoregulation is a mechanism which matches the metabolic rate of a body region to its energy reserves. a, true b. false

Answer 79

False. Metabolic autoregulation is a mechanism that matches the blood flow of a body region to its metabolic demands.

Question 80

Concerning the electrical activity of the heart: The PR interval gives a good indication of the time taken for the spread of depolarisation across the atria. a. true b. false

Answer 80

False. The PR interval indicates the time between the start of atrial depolarization and the start of ventricular depolarization. This includes the time for depolrisation to spread across the atria, but it is mostly due to the slow conduction through the atrioventricular node.

Question 81

The PR interval is normally under 0.2 seconds. a. true b. false

Answer 81

True. The PR interval represents the time between the start of atrial depolarization and the start of ventricular depolarisation. Most of this is taken up by conduction through the atrio-ventricular node. An interval of over 0.2 seconds indicates that this is impaired and is classed as 1st degree heart block.

Question 82

Concerning the vascular system: Local arteriolar dilation, as occurs in exercising muscle, may cause oedema. a. true b. false

Answer 82

True. Arteriolar dilation will increase the hydrostatic pressure in downstream capillaries and increase the amount of fluid that is filtered out through Starling’s forces.

Question 83

Concerning the vascular system: Rhythmic contraction of skeletal muscle promotes venous return. a. true b. false

Answer 83

True. This the action of the skeletal muscle pump. It is one of several mechanism that increase venous pressure and venous return during exercise and therefore offset the reduction in end diastolic volume caused by heart heart rates. The others include the respiratory pump, venomotor tone, and increased systemic filling pressure.

Question 84

Regarding control of the peripheral circulation: Increasing the radius of an arteriole 2-fold, increases its resistance 16-fold. a. true b. false

Answer 84

False. Close. Varying radius does alter resistance to the power of 4, but increasing radius will reduce resistance, not increase it.

Question 85

Concerning the cardiac cycle: At resting heart rate, systole takes approximately twice as long as diastole. a. true b. false

Answer 85

False. At resting heart rate, systole takes about 1/3rd of the cardiac cycle, ie it is half as long as diastole. At higher heart rates, most of the time is taken out of diastole and so systole takes a proportionally greater proportion of the cycle.

Question 86

Concerning the cardiac cycle: Most of the stroke volume leaves the ventricle during the first third of systole. a. true b. false

Answer 86

True. This is the rapid ejection phase.

Question 87

Regarding control of the peripheral circulation: Circulating adrenaline causes arteriolar constriction in all body regions. a. true b. false

Answer 87

False. Whilst adrenaline activates alpha 1 receptors and causes arteriolar constriction in the vast majority of body regions, there are notable exceptions. These are the skeletal muscle and cardiac muscle which also express beta 2 receptors which cause arteriolar dilation and swamp the alpha 1 receptor mediated constriction.

Question 88

the skeletal muscle and cardiac muscle which also express beta 2 receptors which cause arteriolar dilation and swamp the alpha 1 receptor mediated constriction. a. true b. false

Answer 88

a. true

Question 89

Concerning the vascular system: Most arterioles are innervated only by parasympathetic nerves. a. true b. false

Answer 89

False. Most blood vessels are innervated only by sympathetic vessels. These release noradrenaline which activates alpha 1 receptors and causes vasoconstriction. Most vessels are not innervated by the parasympathetic system. The genitalia and salivary glands are the exceptions that prove the rule.

Question 90

Most vessels are not innervated by the parasympathetic system. a. true b. false

Answer 90

a. true The genitalia and salivary glands are the exceptions that prove the rule.