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Principles of physiology > Lecture 9 -Cardiac Physiology I: Structure, function, electrical conductance > Flashcards

Lecture 9 -Cardiac Physiology I: Structure, function, electrical conductance Flashcards

1
Q

How can the cardiovascular system be anatomically split up?

A

The cardiovascular system can be
anatomically subdivided into the heart
and the blood vessels

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2
Q

What is the main function of the heart?

A

The heart’s main function is to pump
oxygenated blood into systemic
circulation (to all body organs) and
deoxygenated blood into pulmonary
circulation (to the lungs)

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3
Q

What are blood vessels and how are they split up?

A

Blood vessels are the distribution
system and are divided into:
Arterial system (oxygenated blood)
Venous system (deoxygenated blood)

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4
Q

Design a diagram that splits the circulatory system up between the venae cavae and the pulmonary artery

A
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5
Q

What are systemic and pulmonary circulation?

A

Systemic circulation: (Both arterial and
venous system)
Blood is pumped from the left site of the
heart (left ventricle) and circulate around
body then returns to the heart through the
right ventricle
(Circuit of vessels carrying blood between
heart and other body systems)

Pulmonary circulation: Where
the blood pumped from the right
ventricle into the pulmonary
artery to the lungs and gets
oxygenated
(Closed loop of vessels carrying
blood between heart and lungs)

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6
Q

How is blood divided between the 2 systems?

A

Systemic circulation:

Pulmonary circulation:

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7
Q

How big is the heart and how much does it weigh?

A

Approximately the size of your fist

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8
Q

Where is the heart located?

A

centre left of chest

– Superior surface of diaphragm
– Left of the midline
– Anterior to the vertebral column, posterior to the sternum

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9
Q

What is the myocardium? What is it composed of? What is the thicker side and why?

A

The heart normally weighs about 300 g in an adult

 The heart (myocardium) is composed of 4 chambers:
2 atria: left (LA) and right (RA) 2 ventricles: left (LV) and right (RV)

The left ventricular
wall is thicker than
that of the right
ventricle because it pumps blood around the body

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10
Q

What are the heart valves needed for?

A

The heart valves are present to aid the unidirectional flow of
blood

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11
Q

What are the atria needed for? How does blood enter the atria?

A

Atria are the receiving chambers of the heart
Blood enters right atria from superior and inferior venae cavae
Blood enters left atria from pulmonary veins

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12
Q

What are the ventricles and how does it enter the heart?

A

Ventricles are the discharging chambers of the heart
Right ventricle pumps blood into the pulmonary artery
Left ventricle pumps blood into the aorta

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13
Q

On the right side of the heart what is blood pumped through and why? What happens when the ventricle contracts?

A

Right side
From the great
veins and right
atrium blood
flows through
the tricuspid
valve (atrioventricular
valve) to fill
the right
ventricle

When the right
ventricle
contracts
blood flows
through the
pulmonary
valve to the
lungs.

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14
Q

Where does blood enter from to get into the left atria and what happens when the left atria contracts?

A

Left side
From the
pulmonary
vein and left
atrium blood
flows through the mitral
valve (atrioventricular
valve) to fill
the left
ventricle

When the left ventricle
contracts
blood flows
through the
aortic valve
to the aorta
and hence
the body.

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15
Q

Name all the valves

A

(right side)
Pulmonary
valve
Tricuspid
valve

(left side)
Aortic
valve
Mitral
valve

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16
Q

What is the pericardium? Where is it located and What is it needed for?

A

Pericardium – a double-walled sac around the heart composed of:
1. A superficial fibrous pericardium
2. A deep two-layer serous pericardium
a. The parietal layer lines the internal surface of the fibrous
pericardium

17
Q

What is the heart wall made up of? What are the 3 layers for?

A

Epicardium – visceral layer of the serous pericardium

Myocardium – cardiac muscle layer forming the bulk of the heart

Endocardium – endothelial layer of the inner myocardial surface

18
Q

What are the major vessels that return blood to the heart from external anterior view?

A

Arteries – right and left coronary (in atrioventricular groove),
marginal, circumflex, and anterior interventricular arteries

Veins – small cardiac, anterior cardiac, and great cardiac veins

19
Q

From the anterior view, What are the major vessels that convey blood away from the heart and name the branches of the aorta?

A

Vessels returning blood to the
heart include:
1. Superior and inferior venae
cavae
2. Right and left pulmonary
veins

Vessels conveying blood away
from the heart include:
3. Pulmonary trunk, which
splits into right and left
pulmonary arteries

  1. Ascending aorta (three
    branches) –
    a. Brachiocephalic
    b. Left common carotid
    c. Subclavian arteries
20
Q

Front the posterior view what are the major blood vessels that take blood too and from the heart?

A

Vessels returning blood to
the heart include:
1. Right and left
pulmonary veins
2. Superior and inferior
venae cavae

Vessels conveying blood
away from the heart
include:
3. Aorta
4. Right and left
pulmonary arteries

21
Q

When does most blood flow happen and why? Where does most blood flow take place?

A

Most of the blood flow through the coronary
arteries occurs when the heart is relaxed.
The contraction of the heart is so powerful it closes
the
arteries during this time.

22
Q

How is the heart affected by ischaemia?

A

when blood flow to the heart muscle is constricted because of an artery spasm

Atherosclerosis is one of the main
causes of myocardial ischemia

23
Q

What muscles make up the heart muscle and how is the heart contracted?

A

Heart muscle (cardiac myocytes) :
– Is stimulated by nerves and is self-excitable (automaticity)
– Contracts as a unit
– Has a long (250 ms) absolute refractory period

the heart is conducted by:
autorythmic fibres in the SA node, located in the right atrial wall act as the hearts pacemaker.
-The hearts pacemaker initiates cardiac action potentials that cause contractions of the hearts chanbers

24
Q

What are pacemaker cells?

A

Pacemaker cells differentiate
from other cardiomyocytes to
have this specialist function

25
Q

What are the 3 steps in the cardiac action potential?

A
  1. rapid depolarization due to Na+ inflow when voltage-gated fast Na+ channels open
  2. plateau of membrane potential (a maintained depolarization) due to Ca2+ ions flowing in when voltage-gated slow Ca2+ channels open and K+ outflow when some K+ channels open
  3. repolarization due to the closure of Ca2+ channels and K+ outflow when additional-gated K+ channels open
26
Q

Why is the SA important?

A

The cardiac conduction system
regulates the heart rate
and rhythm

27
Q

How does the action potential spread through the heart?

A

1 The heart has a natural
pacemaker from where APs
originate - the sinoatrial (SA)
node, also known as the
natural pacemaker

  1. AP propagates across the atria
    and depolarises and excites the
    atrial myocardium (muscle)
  2. 2 The AP reaches the atrioventricular (AV) node - the only
    electrical connection between
    atria and ventricles
    *The AP is delayed at the
    AV node. This allows the
    atria to be excited (and
    contract) before the
    ventricles
  3. 3 The AP then propagates
    rapidly down the bundle of
    His
  4. The AP next propagates rapidly
    down to the left and right
    branches of His
  5. The AP next propagates rapidly
    down to the left and right
    branches of His
  6. then down Purkinje fibre bundles
  7. Impulse rapidly disperses
    throughout the myocardium via
    Purkinje fibres
  8. Thus, the ventricular
    myocardium is depolarised at
    nearly the same time
    due to rapid cell-to-cell spread of
    impulse through gap junctions
28
Q

How are action potentials regulated? How many times do they occur per minute?

A

Usually there are ~75-80 AP
generated per min
This can be regulated externally:
* Heart is stimulated by the
sympathetic cardioacceleratory
centre
* Heart is inhibited by the
parasympathetic
cardioinhibitory centre

29
Q

Can the nervous system elicit cardiac action potentials?

A

BUT – the nervous system cannot
elicit cardiac action potentials:
this can only happen via the SA
node

30
Q

What does the ECG teach you?

A

*The electrocardiogram (ECG) is a body surface recording of the
overall cardiac electrical activity with time.
* It is not a direct recording of actual electrical activity of heart

31
Q

What are the standard limb leads for the heart?

A

1, 2, 3

32
Q

How is the p wave developed by a cardiac impulse?

A

Atrial depolarisation generates
a ‘P wave’ on the ECG

33
Q

How are QRS impulses developed?

A

Ventricles invaded by impulse and
depolarised generating a QRS
complex

34
Q

What can you learn about a rhythm from an ECG?

A

the rhythm of the heart is usually determined by the difference between the R peaks (the regular RR interval)

Each QRS complex is preceded by a P wave

35
Q

What are the normal ecg values?

A

P-R interval= 0.12-0.20 sec

QRS width= 0.08-0.12 sec

Q-T interval= 0.35-0.43 sec

36
Q

How can ECGs be used to measure heart rate?

A

R-R interval can be used to measure the heart rate (HR).
*Measure the distance between the peaks of 2
consecutive QRS complexes at a known recording speed.
*Heart rate = 1/R-R interval; Normal range 55-75
beats/minute.

37
Q

How can you use ECGs to learn about sinus arrhythmias?

A

Sinus Rhythm- normal spacing

Sinus Bradycardia- very large gaps in the RR peaks

Sinus Tachycardia-
very small gaps in the RR peaks- more AP being fired

38
Q

How can you spot a myocardial infarction using an ECG?

A

ST depression of elevation

39
Q

from the posterior view what vessels supply and drain the heart?

A

Arteries – right
coronary artery (in
atrioventricular groove)
and the posterior
interventricular artery (in
interventricular groove)
Veins – great cardiac
vein, posterior vein to left
ventricle, coronary sinus,
and middle cardiac vein

Principles of physiology (21 decks)

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