Module 1 Lecture 2 Flashcards

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1
Q

Why is the cardiovascular system

important?

A

• Transports O2 & nutrients to tissues
• Removes waste products (e.g. CO2) from the
body
• Transports hormones around the body
• Helps maintain body temperature by shifting
heat around the body

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2
Q

What is the cardiac cycle?

A

The cardiac cycle is the period between one heartbeat

& the next

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3
Q

In each cycle, what happens to the Atria and ventricles?

A

In each cycle, the atria & ventricles undergo separate
phases of systole (contraction & emptying) and diastole
(relaxation & filling) in response to electrical activity
Recall that the atrioventricular (AV; tricuspid & mitral)
and semilunar valves (aortic and pulmonary) ensure
forward blood flow & prevent backwards flow

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4
Q

What is an ECG?

A
Electrical currents generated &
transmitted throughout the heart
spread throughout the body ->
these can be measured by
electrocardiography
• An electrocardiograph (ECG)
provides a graphical presentation
• An ECG is the sum of all action
potentials in the heart at a given
time – not a single action potential
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5
Q

Label the eletrical events of the cardiac cycle!

A

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6
Q

What occurs in the P wave?

A

atrial depolarization

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7
Q

What is the QRS complex

A

ventricular depolarization

& atrial repolarization

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8
Q

What occurs in the T wave?

A

ventricular repolarization

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9
Q

What occurs in PR interval

A

AV node delay

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10
Q

What occurs in the ST segement?

A

Entire ventricle is depolarized

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11
Q

NOTE

A

Electrical events alwats precede contraction and relaxation

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12
Q

What happens in normal sinus rhythm?

A

8 beats in 6 seconds = 80bpm

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13
Q

What occurs in junctional rhythm

A

the SA node is non-functional, resulting in P waves being absent and AV node paces heart at 40-60bpm

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14
Q

What occurs in a second degree heart block?

A

The AV nodes fails to conduct some SA node impulses, resulting in more P waves than QRS waves, usually 2 P waves for each QRS wave

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15
Q

What occurs in ventricular fibrillation?

A

Electrical activity is disorganised, AP occur randomly throughout the ventricles, results in chaotic, grossly abnormal ECG deflections, seen in acute attacks and after electric shock

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16
Q

What are the mechanical phases of the cardiac cycle?

A

P-Q Interval: atria contract –> R-S interval: isovolumetric contraction phase (valves closed) –> S-T: ventricles contract and eject, atria relax –>Post T wave: ventricles relax (isovolumetric relaxation phase)

17
Q

Label the diagram, pressure changes and valve closures/openings during a cardiac cycle

A
Valves open when
pressure is higher in the
first compartment
(direction of blood flow) andValves close when
pressure is higher in the
next compartment
(direction of blood flow)
18
Q

Define heart rate

A

HR) – number of times the heart beats (i.e. completes one cardiac
cycle of systole & diastole) in 1 minute

19
Q

Stroke volume (SV)?

A
Stroke volume (SV) - volume of blood pumped out by each ventricle with each
beat
20
Q

End diastolic volume (EDV)?

A

End diastolic volume (EDV) - volume of blood in ventricle when filling is
complete (‘preload’)

21
Q

End systolic volume (ESV)

A

End systolic volume (ESV) - volume of blood remaining in ventricle when
ejection is complete

22
Q

Cardiac output?

A

Cardiac output (CO) - amount of blood pumped out by each ventricle in 1
minute
CO (ml/min) = HR (beats/min) X SV (ml/beat)
average CO is 5L/min

23
Q

Cardiac reserve?

A
  • difference between resting and maximal CO (i.e. during

exercise CO ↑ 5-fold)

24
Q

CO diagram !!

A

25
Q

How is heart rate determined?

A

Determined by:
• Autonomic influences on the SA node:
– Sympathetic stimulation ↑ HR
– Parasympathetic stimulation ↓ HR
• Other factors: hormone adrenalin, thyroxine (T4), blood
ions (e.g. Ca2+, K+), age, body temperature

26
Q

How is SV determined?

A

Determined by:

  • EDV (venous return)
  • Contractility
27
Q

Regulation of SV by EDV?

A

Venous return affects stretch of cardiac muscle cells
(called preload). The relationship between preload & SV is
called the Frank-Starling Law
↑ venous return/EDV achieved by:
- Sympathetic stimulation squeezing veins
- Skeletal muscle & respiratory pumps
- More filling time due to ↓ HR

28
Q

Regulation of SV by contractility?

A

Contractility is the contractile strength at any given muscle
length. ↑ cytoplasmic [Ca2+] = ↑ cross bridge cycling à
myocardium generates more force
↑ contractility achieved by:
• Sympathetic stimulation (adrenalin & noradrenalin) via
cyclic AMP 2nd messenger system
• Other factors: hormone adrenalin, thyroxine (T4),
glucagon, acidosis, high blood Ca2+, certain drugs

29
Q

What does increased contractility mean?

A
Increased contractility (most likely due to sympathetic
stimulation) shifts Frank-Starling Law curve to the left, cardiac muscles does not normally operate withing the descending limb of the length tension curve.