L2: Anatomy & Physiology Of The CV system

Question 1

What is the biggest part of the heart?

Answer 1

The left ventricle - thicker wall than the right

Atria structures are thin

Question 2

What is the role of the valves in the heart?

Answer 2

stop blood going the wrong way

increase efficiency of blood pumping through heart

Question 3

Myocardial structure

- What 2 things does intercalated disks contain?

Answer 3

1. Gap junctions- for cell to cell ion movement (rapid spread of electrical signal) –> contraction of heart
2. Desmosomes - transfer force from cell to cell (end to end), when cells contract, heart contracts

Question 4

What is the role of cardiomyocytes?

Answer 4

Consume lots of O2 in heart - most dense tissue for mitochondria

Question 5

What is the structure of cardiomyocyte sarcomeres?

Answer 5

I band: actin (thin filaments)
H band: myosin (thick filaments
Titin: 2 way spring : helps cell relax after contracting

Question 6

What is the cardiomyocyte length-tension relation?

Answer 6

• increase in myofilament (actin + myosin) overlap = increase in force
• more stretch (return of blood) = produces bigger contraction (increase in output of blood)

Question 7

What is systolic and diastolic?

Answer 7

Systolic: contraction of heart
Diastolic: relaxation of heart

Question 8

How is action potential conducted throughout the cardiomyocytes?

Answer 8

T-tubules allow conduction of rapid action potential

- releases calcium from Sarcoplasmic reticulum –> triggers synchronous contraction

Question 9

What is the big structural difference btwn cardiac and skeletal myocytes?

Answer 9

Heart has much more mitochondria than skeletal - bc need to continuously move

Question 10

Explain the cardiac excitation-contraction coupling process

Answer 10

1. Ca enters cell during AP plateau
2. Triggers release of more Ca from SR
3. Ca binds to myofilaments (troponin-C)
4. Activates cross-bridge cycling
5. Cell shortens
6. Most Ca pumped back in SR
7. Some Ca exits cell by Na-Ca exchanger and sarcolemmal Ca pump

Question 11

What is the role of the Troponin complex in the contraction and relaxation of cardiomyocytes?

Answer 11

Troponin complex = TnT + TnC + TnI

1. Ca2+ binds to TnC
2. TnC changes conformation
3. TnI moves away from actin myosin binding site
4. Actin binds to myosin and contraction occurs
5. As [Ca2+] falls - Ca2+ dissociated from TnC
6. TnI again blocks actin myosin binding site
7. Relaxation occurs

Question 12

What happens when TnI is phosphorylated by Beta adrenergic signalling?

Answer 12

Promotes dissociation of Ca2+ from TnC and myocyte relaxation

Question 13

What is the difference btwn Cardiac and skeletal ECC?

• no. of AP’s
• Excitation
• Regulation of force
• Metabolism

Answer 13

Cardiac

• One plateau (refractory period where heart cant contract again - prevent arrhythmia)
• gap junction spread
• Ca entry
• oxidative only

Skeletal

• many spikes
• motor unit
• AP freq and summation
• oxidative and glycolytic

Question 14

What happens during isovolumetric contraction?

Answer 14

The heart contract, there is no change in volume but there is change in pressure

Question 15

How can we measure cardiac function?

Answer 15

Echocardiography - systolic function

- assessed by looking at cross sectional view of heart

Question 16

How can we measure systolic function?

Answer 16

Echocardiography - systolic function

- assessed by looking at cross sectional view of heart

Question 17

how can we measure diastolic function?

Answer 17

Echocardiography

- assessed by looking at longitudinal view of heart

Question 18

How can we measure diastolic function?

Answer 18

Echocardiography

- assessed by looking at longitudinal view of heart

Question 19

What does the doppler flow (mitral inflow) measure?

and what do the E and A waves represent?

Answer 19

• measures blood flow velocity through mitral valve
• E wave = blood flowing into ventricle by passive filling (due to pressure gradient)
• A wave = blood flowing from atrium into ventricle by active filling (due to atrial contraction)

Question 20

Doppler flow (mitral inflow)

• what is normal E/A?
• What is impaired relaxation E/A?

Answer 20

normal: E/A > 1
- E wave bigger than A wave

Impaired relaxation: E/A < 1
- as heart stiffens, impaired diastolic function so E wave is similar to A wave

Question 21

What does tissue doppler (mitral valve movement) measure?

What is E’ wave and A’ wave represent?

Answer 21

• measures velocity of tissue movement at mitral valve
• E’ wave = passive LV filling
• A’ wave = filling due to atrial contraction

Question 22

Diastolic function

- what happens to E/e’ ratio with increased severity of heart failure?

Answer 22

E/e’ ratio increases with severity
correlates with HF biomarkers
E/e’ ratio declines when heart failure improves

Question 23

How does electrical activation of myocardium/heart occur?

Answer 23

1. Pacemaker in heart - SA node depolarizes the atria
2. depolarizes septum (left to right)
3. depolarize ventricular walls towards apex and up towards base

Question 24

What route does an AP travel through the conduction system of the heart?

Answer 24

Action potential travels from SA or AV node –> common bundle –> bundle branches –> purkinje fibres –> myocytes (cause contraction)

Question 25

ECG: what is... (refer to slides for diagrams) P wave QRS wave T wave

Answer 25

P - due to atria contracting (depolarisation) QRS - ventricles contracting (depolarisation) T - ventricular repolarization

Question 26

What are the biomarkers of heart damage? | What is the process of their release?

Answer 26

Enzymes such as CK-MB, Troponin I (troponin free in cytoplasm, troponin complex released from actin filament), myoglobin - used to diagnose myocardial infarction 1. onset of myocardial infarction 2. plasma membrane of necrotic (dead) myocytes become leaky 3. mlcs leak out of cell and into circulation

Question 27

What is the difference in pressure btwn arterial and venous circuit?

Answer 27

Arterial circuit: - high pressure Venous circuit - low pressure to deliver nutrients and O2 and remove waste

Question 28

Describe the venous return to the heart via calf muscle + role of valves

Answer 28

- the calf muscle acts as pump for deep leg veins - calf muscle relaxed: valves prevent backflow, valves closed - calf muscle contracted : valve open, blood flow caused by muscle contraction

Question 29

What are the characteristics of the diff. blood vessels? - large arteries - small arterioles - capillaries - large veins

Answer 29

(refer to slides) - large arteries - pressure reservoir - small arterioles - resistance vessels - capillaries - exchange - large veins - volume reservoir

Question 30

Where is there the most blood volume distribution?

Answer 30

Most volume in systemic veins and venules

Question 31

What is distribution of cardiac output through vascular tree and organ beds?

Answer 31

Vascular tree: perfused in series Organ beds: perfuse in parallel At rest: highest flow to gut and kidney Arterioles: control flow through each bed - by local and central signals

Question 32

What do the lymphatic vessels contain?

Answer 32

excess interstitial fluid, white blood cells, also transports fats from gut

Question 33

What is the role of the lymph nodes? How does lymph enter the blood?

Answer 33

Role: important in adaptive immune response Transport: enters blood via lymphatic duct (right side), thoracic duct (left side) - aided by smooth muscle contraction + valves

Question 34

What happens to the venous and interstitial fluid during oedema?

Answer 34

Oedema: accumulation of interstitial fluid - increase in venous pressure e. g. with congestive heart failure - venous pooling - fluid accumulation in lung - increase in interstitial pressure e.g. lymph vessel blockage, parasitic infection, gross oedema of limbs caused by poor lymph drainage (not capillary dysfunction)

Question 35

What is blood pressure?

Answer 35

the driving force to push blood through circulation

Question 36

Role of pressure in resistance of vessels - systemic and pulmonary resistance

Answer 36

``` Resistance systemic (narrower vessels) >> pulmonary resistance largest overall resistance in arterioles + biggest pressure drop ```

Question 37

How to calculate MAP (mean arterial pressure)?

Answer 37

``` MAP = DP + 1/3 PP PP = SP - DP ```

Question 38

How does vasoconstriction and vasodilation occur?

Answer 38

Vasoconstriction: smooth muscle cells contract + increase resistance of vessel Vasodilation: smooth muscle cells relax and decrease resistance of vessel

Question 39

Equation for: Blood flow (velocity) Cardiac output

Answer 39

Blood flow = pressure gradient (P2-P1)/ resistance - blood flow decreases with increased resistance - blood flow increases with increased pressure gradient Cardiac output = mean arterial pressure / total peripheral resistance (TPR) CO = HR x SV

Question 40

Role of Noradrenaline and Adrenaline in Sympathetic NS activation

Answer 40

Noradrenaline: - at smooth muscle cells Receptor - alpha AR Response - constrict Adrenaline - at smooth muscle cells receptor - beta 2 AR response - dilate muscle