3 - CV Physiology

Question 1

Myocardium (key points)

Answer 1

• 95% of the heart
• responsible for pumping
• cardiac muscle (involuntary)
• fibers swirl diagonally around the heart

Question 2

Cardiac muscle tissue (structural components of cell connections)

Answer 2

• sarcolemma (cell wall)
• cells connect at intercalated discs (1) containing:
  
  • gap junctions (allow cells to communicate)
  • desmosomes (keep fibers connected)

1-thickened sarcolemma

Question 3

quiz on:
cardiac conduction system

Answer 3

see goodnotes

Question 4

Sinoatrial (SA) node
(electrical signal)

Answer 4

fires constantly (100 times/min) which would translate to our bpm if nothing controlled it

Question 5

cardiac conduction system anatomy

Answer 5

• sinoatrial (SA) node
• atriventricular (AV) node
• bundle of HIS
• right and left bundle branches
• purkinje fibers

Question 6

Action potential phases in ventricular myocyte

Answer 6

RMP roughly -90mV (1)
rapid depolarization (+20mV)
- Na+ channels open
- Na+ inflow depolarizes the cell
plateau (+10mV)
- Ca2+ inflow
- some K+ outflow
repolarization (90mV)
- Ca2+ channels close
- K+ outflow

refractory period (2) from depolarization to mid repolarization
contraction starts right after RP and ends right before

1-voltages are just examples, 2-cardiac AP cannot trigger

Question 7

Electrocardiogram (ECG) 3 waves
(draw + label)

also called ECG or EKG, see goodnotes for graph

Answer 7

in order:
- P wave: small wave (+0.1mV/0.1s)
- QRS complex: 3 spikes (0.2,+1,-0.4mV/0.1s)
- T wave: large wave (+0.2mV/0.2s)
- U wave: tiny wave (not visible on most graphs)

voltages and times are just example values

info on how ECG functions is on avenue, not neccessary

Question 8

Events corresponding to sections of the ECG graph

Answer 8

• P: atria depolarize (action potential at SA node)
• flat: atrial systole (1)
• QRS: ventricles depolarize
• flat: ventricular systole
• T: ventricles repolarize
• flat: ventricles relax

1-contraction

Question 9

average values for adult:
- cardiac cycle length
- native bpm
- stroke volume
- blood pressure

Answer 9

• 0.8s
• 75bpm
• 70mL
• < 120/80 mmHG

Question 10

Pressure waves vs ECG
(draw wave + label valve changes)

see goodnotes for graph

Answer 10

pressure waves: aortic, V, A
- AV close: R spike, first dip in LV/LA P
- SL open: QRS end, start of 1st wave for aortic P, 2nd wave peak LA
- SL close: mid T, dip in aortic P
- AV open: T end, end of wave in LV and aortic P, small wave in LA

systole –> increased pressure

Question 11

aortic valve pressure wave
(notable points)

Answer 11

• aortic valve opens
• aortic valve closes
• dicrotic wave due to rebound off valve closure

Question 12

heart sounds

Answer 12

loudest
- S1: AV valves close
- S2: SL valves close
- S3: ventricles fill (much quieter
- S4: atrial systole (almost silent)

Question 13

Pressure phases (cardiac cycle) in order

Answer 13

• atrial contraction (AV open)
• isovolumetric contraction (all closed)
• ventricular ejection (SL open)
• isovolumetric relaxation (all closed)
• ventricular filling (AV open)
• atrial contraction (AV open)…

Question 14

Ventricular volume curve
(draw + label)

Answer 14

• end diastolic volume (V systole start)
• end systolic volume (V systole end)
• stroke volume = EDV - ESV (∆volume in a V)

Question 15

Cardiac output
(definition + equation)

Answer 15

volume of blood ejected from a ventricle into it’s respective vessel each minute
CO = HR x SV

heart rate x stroke volume

Question 16

cardiac reserve
(definition + equation)

Answer 16

difference between our maximum HR and our resting HR
CR = HR(max) - HR(rest)

Question 17

Factors regulating stroke volume
(names + definitions)

Answer 17

increased x will increase SV:
- preload: stretch on heart before contracts
- contractility: contraction force of muscle fibers

increased x will decrease SV:
- afterload: pressure in V required to open SL valves

Question 18

Frank-Starling Law

Answer 18

stroke volume (SV) is proportional to muscle stretch and end diastolic volume (EDV)

only to a point, muscle can’t stretch indefinitely

Question 19

what affects preload?

Answer 19

• duration of ventricular diastole
  
  • increase leads to slower HR
• venous return
  
  • eg: increased by exercise, decreased by hemorrhage

increase in either leads to increased preload

Question 20

what affects contractility?

Answer 20

changes in cytosolic Ca2+
altered by inotropes:
- positive (increase C) eg: epinephrine
- negative (decrease C) eg: hypoxia(1)

1-low O2 levels in body tissues

Question 21

what affects afterload?

Answer 21

• blood pressure
  
  • high BP –> increased afterload
• vessel structure
  
  • vasoconstriction –> increased afterload

Question 22

qualities of the conductive fibers in the heart

Answer 22

• autoarithmic: will depolarize spontaneously (act as pacemakers)
• SA node is fastest and will set the pace
• if preceding structures are impaired, the next structure sets a slower pace (eg: damaged SA node will lead to slower pace set by AV node)

Question 23

Factors regulating HR

Answer 23

• Autonomic NS (+ symp. -parasymp.)

Chemical:
- Hormones ( +E&NE +Thyroxine)
- Cations (+Ca -Na -K)
- Hypoxia (-less oxygen)
- Acidosis (-excess H+)
- Alkalosis (-high pH)

Other:
- Age (+infants -older)
- Body Temp (+high T -low T)

Question 24

Nervous system control of the heart

Answer 24

Input:
- proprioceptors (monitor movement)
- chemoreceptors (measure blood chemistry)
- baroreceptors (monitor blood pressure)
Processing:
- cardiovascular center in medulla oblongata
Output:
- cardiac accelerator nerves (sympathetic) - increase HR and stroke volume
- vagus nerves (CN X, parasympathetic) - decrease HR

remember: SNS - adrenergic receptors, PSNS - cholinergic receptors