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pharmacology > Cardiac System: Structure and Function > Flashcards

Cardiac System: Structure and Function Flashcards

1
Q

State the structures of the cardiac tissue.

A
  • Serous membrane
  • Pericardial cavity
  • Parietal pericardium
  • Fibrous pericardium
  • Coronary blood vessel
  • Endocardium
  • Myocardium
  • Epicardium
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2
Q

Describe the myocardium

A

Cardiac muscle fibres arranged into 4 chambers: 2 atria, 2 ventricles

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3
Q

Describe the conduction system

A

Specialised tissue which conducts nerve impulses through heart, SA and AV node, bundle of His, bundle branches and purkyne fibres

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4
Q

Describe the nerve supply

A

Nerve branches from both sympathetic and parasympathetic divisions of the ANS - regulates heart rate and force of contraction

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5
Q

Describe the thickness of cardiac walls

A

Myocardium of left ventricle is much thicker than the right.

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6
Q

Describe blood supply to the heart.

A
  • Coronary artery and vein system
  • Right and left coronary arteries branch off from aorta and into smaller vessels
  • Cardiac veins deliver blood to coronary sinus and back to the right atrium
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7
Q

How does coronary artery disease occur?

A

When coronary arteries cannot deliver blood adequately: plaques in arterial walls

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8
Q

How does a myocardial infarction occur?

A

When blood supply to heart is completely blocked; muscle dies

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9
Q

Describe the structure of the pericardium.

A

Double-walled sac around the heart composed of:
- superficial fibrous pericardium
- deep two-layer serous pericardium
- parietal layer lines the internal surface of the fibrous pericardium
- visceral layer lines the surface of the heart
- Separated by the fluid-filled pericardial cavity

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10
Q

Describe the function of the pericardium.

A
  • Protects and anchors the heart
  • Prevents overfilling of the heart with blood
  • Allows for the heart to work in a relatively friction-free environment
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11
Q

State the functions of the heart.

A
  • Regulates blood supply: changes in contraction rate and force to match changing metabolic needs
  • Generating blood pressure
  • Ensuring one-way blood flow: valves
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12
Q

State and describe the two circuits of the heart.

A
  1. Pulmonary circuit: blood to and from the lungs - eliminates CO2 via the lungs and oxygenates the blood
  2. Systemic circuit: blood to and from the rest of the body - delivers oxygen to all body cells and carries away wastes
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13
Q

Describe the movement of blood in the heart.

A
  • Venous return into the heart via the vena cava, into the right atrium and then the right ventricle
  • Venous blood pumped to the lungs via pulmonary arteries
  • Oxygenated blood (red blood) returns to heart via pulmonary veins, into the left atrium and then the left ventricle
  • Red blood then pumped to all body tissues via aorta
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14
Q

Define cardiac cycle

A

Electrical, pressure and volume changes that occur in functional heart between two heart beats

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15
Q

State and describe the two phases of the cardiac cycle

A

Diastolic phase: When myocardium is relaxing
Systolic phase: myocardium is contracting

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16
Q

Name the valve between the right atrium and right ventricle?

A

Tricuspid valve

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17
Q

Name the valve between the right ventricle and pulmonary trunk.

A

pulmonary semilunar valves

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18
Q

Name the valve between the left atrium and left ventricle.

A

bicuspid valve

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19
Q

Name the valve between the left ventricle and aorta.

A

Aortic semi-lunar valves

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20
Q

Describe atrial diastole and systole

A
  • Blood flows into and passively out of atria (80% of total); AV valves open
  • Atrial systole pumps only about 20% of blood into ventricles
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21
Q

Describe ventricular filling: mid-to-late diastole

A
  • Heart blood pressure is low as blood enters atria and flows into ventricles
  • 80% blood enters ventricles passively; atrial systole occurs pumping other 20%
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22
Q

Describe ventricular systole

A
  • Atria relax; rising ventricular pressure closes AV valves (‘lubb’)
  • Isovolumetric contraction phase
    – Ventricles contract, no blood leaving (Pressure too low to open semilunar valves)
    – Ventricular ejection phase opens semilunar valves
  • Ventricular pressure&raquo_space; pressure in arteries (aorta and pulmonary trunk)
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23
Q

Describe ventricular diastole

A

Ventricles relax; blood backflow, closes semilunar valves (“dubb”)
- Blood once again flowing into relaxed atria and passively into ventricles

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24
Q

Describe ‘lubb’ and ‘dubb’

A

Lubb - when the atrioventricular valves - tricuspid and bicuspid - close i.e atrial diastole

Dubb - when the semi-lunar valves - pulmonary and aortic - close i.e ventricular diastole

25
Q

What is the avg bpm for young adult females?

A

72-80

26
Q

What is the avg bpm for young adult males?

A

64-72 bpm

27
Q

State the resting heart rate in those with tachycardia

A

in excess of 100 bpm due to stress, anxiety, drugs, heart disease or increased body temp.

28
Q

State the heart rate of those with bradycardia

A

less than 60 bpm - in sleep and endurance trained athletes

29
Q

What is meant by premature atrial contractions?

A

Occasional shortened intervals between one contraction and next - occurs in healthy people

30
Q

Define cardiac output.

A

amount of blood pumped by each ventricle in one minute
CO = Heart Rate (beats/min) x Stroke Volume (ml/beat)

31
Q

What are the factors affecting cardiac output?

A

heart rate - autonomic innervation and hormones
stroke volume - end-diastolic volume and end-systolic volume

32
Q

What is stroke volume?

A

the volume of blood pumped by a ventricle per beat
SV - end diastolic volume (EDV) - end systolic volume (ESV)

33
Q

what is EDV?

A

amount of blood in a ventricle at the end of diastole

34
Q

what is ESV?

A

amount of blood remaining in a ventricle after contraction

35
Q

What does ejection fraction mean?

A

% of EDV pumped by the ventricle

36
Q

Define blood pressure.

A

Force exerted by blood against blood vessel walls

37
Q

Which receptors detect changes in blood pressure?

A

Baroreceptors - rising pressure stretches receptors - vagus nerve which in the parasympathetic system.

38
Q

Where and when is blood pressure the highest?

A
  • In large arteries
  • Highest with ventricular systole
39
Q

When is blood pressure the lowest?

A
  • Lowest with ventricular diastole
40
Q

How to calculate blood pressure?

A

Peak pressure divided by minimum pressure.

41
Q

Describe how blood pressure increases.

A
  • Blood volume increases
  • Heart rate increases
  • Stroke volume increases
  • Blood viscosity increases
  • Peripheral resistance increases
42
Q

Describe reducing blood pressure.

A
  1. Cardiac output increases
  2. Blood pressure rises
  3. Baroreceptors in aortic arch and carotid sinuses are stimulated
  4. Sensory impulses to cardiac centre
  5. Parasympathetic impulses to heart
  6. S-A node inhibited
  7. Heart rate decreases
  8. Blood pressure returns toward normal
43
Q

What is meant by preload?

A
  • Tension applied before the muscle performs any work = end diastolic volume
  • INCREASE IN FILLING PRESSURE=INCREASED PRELOAD
44
Q

What is meant by afterload?

A
  • Load that preloaded muscle has to work against
  • aortic pressure present at the instant that the aortic valve opens.
  • Higher aortic diastolic pressure- greater work to pump blood into heart.
  • Afterload = Ventricular Wall Stress that develops during systolic ejection.
    Estimated using Laplace’s Law: VWS = Pressure x radius / 2 (wall thickness)
45
Q

How does preload affect cardiac output?

A

Increased preload = increased cardiac output

46
Q

Describe Frank-Starling mechanism.

A
  • Increased venous return increases ventricular filling and thus preload
  • Myocyte stretching causes an increase in force generation
  • This enables the heart to eject the additional venous return, thereby increasing stroke volume
47
Q

How does after load affect cardiac output?

A

Increased after load decreases cardiac output

48
Q

How does contractility affect cardiac output?

A
  • Increased contractility leads to increased cardiac output
49
Q

What is meant by hypertension?

A
  • When arterial pressure is too high
  • The heart has to work harder
  • The left ventricle enlarges
  • Atherosclerosis can affect coronary arteries - leads to heart disease
  • Deficient blood supply to other parts of the body as damage to blood vessels increases - leads to heart heart failure
50
Q

What is renin?

A

Secreted by the kidney in response to reduced blood pressure or blood volume

51
Q

What is the treatment for hypertension?

A
  • Change lifestyle factors
  • Drug therapy to reduce heart rate
  • Ca2+ channel blockers; reduce calcium flow into heart muscle and thus heart rate
  • Beta blockers (reduce stimulation by sympathetic nervous system)
  • Diuretics reduce blood volume
  • ACE inhibitors interfere with renin- angiotensin pathway
  • Vasodilators (such as nitroglycerin) open up blood vessels (reduce resistance)
52
Q

What is the role of renin?

A

converts Angiotensinogen into Angiotensin I

53
Q

What is the role of ACE?

A

converts Angiotensin I into Angiotensin II

54
Q

What are the actions of angiotensin 2?

A
  • Intense vasoconstriction - increase total peripheral resistance
  • Causes release of Aldosterone from adrenal gland - promotes Na+ and
    H2 O reabsorption in kidney - cause increased blood volume.
  • Regulatory negative feedback on the release of Renin.
  • CNS: Stimulate thirst in hypothalamus, stimulate sympathetic outflow.
  • Designed to bring arterial blood pressure back up to normal set-point
55
Q

State the role of ACE inhibitors.

A
  • Inhibit formation of angiotensin
  • Decrease release of aldosterone, retaining sodium and water
56
Q

State the role of ACE receptor blockers

A
  • Block angiotensin receptors on blood vessels and adrenal cortex
  • Produce vasodilation and decrease the activity of aldosterone
57
Q

What happens as a result of systolic heart failure?

A
  • Less blood pumped out of ventricles
  • Weakened heart muscle can’t squeeze as well
58
Q

What happens as a result of diastolic heart failure?

A
  • Less blood fills the ventricles
  • Stiff heart muscle can’t relax normally

pharmacology (40 decks)

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