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Physiology 2nd Semester > PHS 206 CVS > Flashcards

PHS 206 CVS Flashcards

1
Q

Describe depolarization under action potential of cardiac muscle cells

A

Fast influx of Na+ from the outside to the inside changes the membrane potential to be more positive

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2
Q

Describe the plateau phase under action potential of cardiac muscle cells

A

Na+ stops moving in and Na+ channels close but there is a slow influx of Ca2+ through L-type calcium channels

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3
Q

Describe repolarization under action potential of cardiac muscle cells

A

Ca2+ stops moving in and there is an efflux of K+ creating a negative membrane potential

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4
Q

What is the absolute refractory period?

A

A period of time where it is impossible for the cell to send more action potentials
This is due to the gate in mechanisms on the voltage gated sodium channels

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5
Q

Describe the cardiac conducting system of the heart

A

The sinoatrial node is a structure that generates an electrical signal that causes the atria to contract. The signal is then passed to the AV node to the ventricles causing them to contract

The AV node is located in the Koch triangle, it’s a group of specialized cardiac muscle cells that transmit electrical signals down the bundle of His and then branch off

The bundle of His branches off into the left and right bundle which branches to go down to the intraventricular septum

They send the rest of the electrical activity into the myocardium of the ventricles, causing the ventricles to contract (after calcium ions come in) and push blood from the right side to the lungs and from the left side to the body

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6
Q

Define the cardiac cycle

A

The cardiac cycle is the sequence of coordinated events taking place in the heart during each beat. Each heartbeat consists of two major periods called systole (contraction) and diastole (relaxation)

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7
Q

What is the normal heart rate?

A

72 beats/min

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8
Q

What is an ECG/EKG?

A

A test used to trace the electrical activity in cardiac tissue

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9
Q

Layers of the heart

A

Pericardial
Myocardium
Endocardial

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10
Q

Properties of the heart

A
  • Automaticity,
  • Rhythmicity (chronotropism),
  • Conductivity (dromotropism),
  • Excitability (bathmotropism) and
  • Contractility (inotropism).
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11
Q

What is rhythmicity?

A

This is the ability of the heart to beat regularly (synchronously) without external stimulation
it is myogenic in origin not neurogenic
Nodal fibres and the conduction system are also excitable

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12
Q

What is conductivity?

A

The ability to conduct impulses from one cell to another facilitated by gap junctions that transmits electrical currents
Initiated in the SA node

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13
Q

What is excitability?

A

This is the ability of cardiac muscle to respond to adequate stimuli by generating an action potential

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14
Q

What is contractility?

A

Is the power of the heart muscle to convert electricity into mechanical work. Myocardial fibers have functional synctium and not anatomical synctium because they are present in touch but not in continuity

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15
Q

Why do atria and ventricles contract and relax the same time?

A

Because cardiac muscles act as one synctium
a group of cells are connected together with the aim of contracting and relaxing through gap junctions

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16
Q

Types of cardiac muscle fibers?

A
  1. Nodal fibers (form the sinoatrial and atrioventricular node)
  2. Conducting fibres (Purkinje fibres bundle of His), right and left bundle branches
  3. Contractile fibres (atria and ventricles)
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17
Q

Factors affecting contractility

A

Ions
preload
afterload
temperature

Rules:
All or none law
staircase or treppe phenomenon
starling law

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18
Q

What is the All or none law?

A

According to the all-or-none law, when a stimulus is applied, whatever may be the strength, the whole cardiac muscle gives maximum response or does not respond at all. Below the threshold level, i.e. if the strength of the stimulus is not adequate, the muscle does not give a response.

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19
Q

What is the staircase/treppe phenomenon?

A

It refers to the idea that an increase in heart rate increases the force of contraction generated by the myocardial cells with each heartbeat despite accounting for all other influences.

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20
Q

What is Frank starling law

A

The Frank–Starling law of the heart represents the relationship between stroke volume and end-diastolic volume.

The law states that the stroke volume of the heart increases in response to an increase in the volume of blood in the ventricles, before contraction, when all other factors remain constant

The greater the stretch, the greater the contraction

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21
Q

What are the regulations of the CVS?

A

Heart rate regulation
Blood flow regulation

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22
Q

Does the heart rate increase or decrease in a heart murmur?

A

Increase

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23
Q

Does the heart rate increase or decrease in a ventricular blockage?

A

Decrease

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24
Q

What is the vasomotor center?

A

Vasomotor center regulates the arterial blood pressure by causing vasoconstriction or vasodilatation. However, its actions depend upon the impulses it receives from other structures such as baroreceptors, chemoreceptors, higher centers and respiratory centers.

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25
Q

What do chemoreceptors do?

A

Chemoreceptors are sensors that detect changes in CO2, O2, and pH, and have been classified, as central or peripheral.

Peripheral chemoreceptors influence the vasomotor center.

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26
Q

Describe the sympathetic influence on the neural regulation of the heart

A

through celiac plexus to heart
•secretes norepinephrine and epinephrine
•increases force of contractions
•causes tachycardia and increased contractility

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27
Q

Describe the parasympathetic influence on the neural regulation of the heart

A

Parasympathetic: from medulla oblongata (vagus nerve)
•Nerve branches to S-A and A-V nodes, and secretes acetylcholine (slows rate)
• When parasympathetic activity/stimulation, it slower the heart rate and when parasympathetic activity decreases, heart rate becomes increased

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28
Q

Tachycardia

A

Increase in heart rate beyond what is normal for sex and age

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29
Q

Action of cardiac accelerator nerves

A

Sympathetic Fibers
•Innervate SA node & ventricles
•Increase heart rate
•Increase contractility
•Increase pressure

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30
Q

Action of the vagus nerve

A

Parasympathetic Nerve
•Innervates SA node & AV node
•Releases acetylcholine
•Slows heart rate
•Lowers pressure

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31
Q

Describe the cortical influences on the heart

A

Cerebral cortex impulses pass through cardiovascular control center in medulla oblongata.
–Emotional state affects cardiovascular response
–Cause heart rate to increase in anticipation of exercise

32
Q

Describe the cortical influence of the heart

A

Cerebral cortex impulses pass through cardiovascular control center in medulla oblongata.
–Emotional state affects cardiovascular response
–Cause heart rate to increase in anticipation of exercise

33
Q

Peripheral influences on the heart rate

A

Peripheral receptors monitor state of active muscle; modify vagal or sympathetic
•Chemoreceptors
–Monitor pCO2, H+, pO2
•Mechanoreceptors
–Heart and skeletal muscle mechanical receptors
•Baroreceptors

Baroreceptors in carotid sinus and aortic arch.
–↑ pressure → increase in HR & contractility
–↓ pressure → decrease in HR & contractility

34
Q

Factors affecting blood flow resistance

A

Favours resistance to blood flow
1.Viscosity or blood thickness
2.Length of conducting tube

Favour’s blood flow
3.Radius of blood vessel

35
Q

What does the opening of “dormant” capillaries do during exercise?

A

–Increases blood flow to muscle
–Reduces speed of blood flow
–Increases surface area for gas exchange

36
Q

What are the Local Factors Resulting in Dilation?

A

•↓ tissue O2 produces potent vasodilation in skeletal and cardiac muscle

•Increased temperature
•Elevated CO2
•Lowered pH
•Increased ADP
•Nitric Oxide (NO)
•Ions of Mg+2 and K+
•Acetylcholine

37
Q

What is cardiac output?

A

Cardiac output refers to the volume of blood pumped out per ventricle per minute.
Cardiac output is the function of heart rate and stroke volume.

Heart rate: It refers to the number of times the heart beats per minute (bpm).

Stroke volume: It refers to the quantity of blood pumped out of each ventricle with every heartbeat.

38
Q

Cardiac output is a determining factor during endurance activities. Describe how cardiac output is increased during endurance activities

A

1.Chemo/barorecetors detect.
2. Stimulate cardiac control center in the medulla
3. Initiates Sympathetic via accelerator.
4. Increased impulse at SA node.
5. Increased HR/SV = increased Q.

39
Q

Describe heart Regulation from Rest to Exercise

A

Preexercise “‘anticipatory” response -Activation of motor cortex & higher brain.
- Increase in HR, contractility and vasodilation

Exercise
Continued sympathetic adrenergic
outflow
Concomitant constriction of vasculature in inactive tissues

40
Q

Vascular heart diseases include

A

Pericarditis
Myocarditis
Endocarditis (most common) due to bacterial infection

41
Q

Where is the cardiac center

A

The medulla and is influenced by information form the cerebral cortex

42
Q

On an ECG, what event occurs at the p wave?

A

Atrial depolarization

43
Q

On an ECG, what event occurs at the QRS complex

A

Ventricular depolarization

44
Q

 On an ECG, what event occurs at the T wave

A

Ventricular repolarization

45
Q

Difference between action potential and impulse?

A

Electrical impulse is the transmitted action potential (stimulation of excitable tissue)

46
Q

SA node rate is approximately?

A

90bpm

47
Q

What is an electro cardiogram?

A

Graphical representation of the electrical activity of the heart

48
Q

What is an electrocardiograph

A

A machine that reads ECG

49
Q

What is electrocardiography

A

The process of taking an electrocardiogram

50
Q

Explain the two sounds of the heart

A

1st sound Lub: due to the closure of the atrioventricular valve (long soft not loud)

2nd sound dub: due to closure of the semilunar valves

51
Q

Abnormal heart sound within and outside of the heart is known as

A

Within: murmur
Outside: bruite

52
Q

Explain the bainbridge reflex

A

The stretch receptors of the atria (due to increase pressure) elicit the Bainbridge reflex transmit their
afferent signals through the vagus nerves to the
medulla of the brain. Then efferent signals are
transmitted back through vagal and sympathetic nerves to increase heart rate and strength of heart
contraction.
* Thus, this reflex helps prevent damming of blood in the veins, atria, and pulmonary
* The atria also secretes natriuretic peptides (↑ NaCl
Excretion)

53
Q

What are the reasons for blood pressure regulation?

A

– to keep blood flow constant to vital organs
– for the maintenance of homeostasis

54
Q

Types of regulatory mechanisms of blood pressure regulation

A

Nervous mechanism
Renal mechanism
Hormonal mechanism
Local mechanism

55
Q

Describe the control of blood pressure

A
  • Venous return : aided by respiratory and Muscular
    (SM) pump
  • End Diastolic Volume (EDV)
    – Strokes volume (SV): SV affects CO
  • Cardiac output (CO): directly proportional to systolic
    pressure – Heart rate (HR): HR affects CO
  • Peripheral resistance: directly proportional to diastolic
    pressure
56
Q

What is sinus tachycardia?

A

An increase in the discharge if impulse from the SA node, resulting in an increase in heart rate
Discharge of impulses from SA node is very rapid and the heart rate increases up to 100/ minute and sometimes up to 150/minute 

57
Q

What is sinus bradycardia?

A

A reduction in the discharge of impulse from the SA node resutling n decrease heart rate (less than 60bpm)

58
Q

Define arrhythmia

A

arrhythmias and conduction disorders are caused by abnormalities in the generation or conduction of these electrical impulses or both. In such cases the SA node may not be the pacemaker

59
Q

Classification of arrhythmia

A

Normotropic arrhythmia
ectopic arrhythmia

60
Q

Types of Normotropic arrhythmia

A

Sinus arrhythmia
sinus tachycardia
sinus bradycardia

61
Q

What is sinus arrhythmia

A

Is a normal rhythmical increase and decrease in heart rate in relation to respiration

62
Q

Describe the conducting system of the heart

A
  1. Sinoatrial node. Sinoatrial (SA) node is located in the wall of right atrium, just right to the opening of superior vena cava. Spontaneous rhythmical electrical impulses arise from the SA node and spread in all directions to:
    Cardiac muscles of atria,
    Interatrial tract to left atrium and
    Internodal tracts to AV node.
  2. Atrioventricular node. The AV node is located just
    beneath the endocardium on the right side of lower part of the atrial septum, near the tricuspid valve. It is stimulated by the excitation wave that travels through the internodal tracts and the atrial myocardium. From it, the cardiac impulse is conducted to the ventricles by the AV bundle.
  3. Atrioventricular bundle of His. The AV bundle arises
    from the AV node, descends through the fibrous skeleton of the heart and divides into right bundle branch for the right ventricle and the left bundle branch for the left ventricle. The branches break up and become continuous with the plexus of Purkinje fibres.
  4. Purkinje fibres. These are spread out deep to the endocardium and reach all parts of the ventricles including the bases of papillary muscles
63
Q

Rate of production of rhythmic impulses by different
parts of the heart is

A

Atrial muscle: 40–60/min and
Ventricular muscles: 20–40/min.
SA node: 70–80/min,
AV node: 40–60/min

64
Q

Clinical significance of contractility

A

A decreased cardiac contractility is the hallmark of a clinical condition called myocardial failure, which can result from coronary artery disease, myocardial ischemia, myocardial infarction, myocarditis, toxins or electrolyte imbalance. Myocardial failure impairs the pumping ability of one or more ventricles

65
Q

What is pulmonary circulation

A

Pulmonary circulation is between the heart and the lungs where deoxygenated blood will leave the right ventricle via the pulmonary artery to the lungs for oxygenation and being returned via the pulmonary vein to the left atrium

66
Q

What is the Systemic circulation

A

Systemic circulation is between the heart and the rest of the body during which oxygenated blood will leave the left ventricle via the systemic aorta to supply various parts of the body and deoxygenated blood being returned through the vena cava into the right atrium

67
Q

Whats is blood pressure

A

Blood pressure is the pressure of circulating blood against the walls of blood vessels.

68
Q

Blood pressure can be expressed in the following terms

A

– 1. Systolic blood pressure
– 2. Diastolic blood pressure
– 3. Pulse pressure
– 4. Mean arterial blood pressure

69
Q

What are the Physiological variations of BP

A
  • Sex: 5 mmHg less in females than in males of
    same age b4 menopause but same after
    menopause.
  • Body Build: more in obese persons than in lean
    persons.
  • Meal: Increased after meal
  • Diurnal Variation: low at morning; increases
    reaching maximum at noon; low in evening
  • Reduced by 15-20mmHg during sleep
  • Exercise, Anxiety or Excitement increases BP
70
Q

What are the Physiological variations of BP

A
  • Sex: 5 mmHg less in females than in males of
    same age b4 menopause but same after
    menopause.
  • Body Build: more in obese persons than in lean
    persons.
  • Meal: Increased after meal
  • Diurnal Variation: low at morning; increases
    reaching maximum at noon; low in evening
  • Reduced by 15-20mmHg during sleep
  • Exercise, Anxiety or Excitement increases BP
71
Q
  • Maximum BP occurs____
A

in the aorta during the systolic ejection phase (systolic pressure (Ps))

72
Q

minimum aortic pressure is reached during_____

A

the isovolumic contraction phase while the
aortic valves are closed (diastolic pressure
(Pd))

73
Q

Formula for pulse pressure

A

Ps – Pd = pulse pressure (PP),

74
Q

Formula for MAP

A

Mean arterial blood pressure = Diastolic pressure + 1/3 PP

75
Q

How to measure BP

A

Ascultatory: Using a stethoscope and a sphygmomanometer
* Palpation
* Invasive/cannulla

76
Q

Ectopic arrhythmia

A

Ectopic arrhythmia is the abnormal heartbeat, which one of the structures of the heart other than the SA node becomes the pacemaker. Impulses, produced by these structures are called ectopic foci

77
Q

Types of ectopic foci

A
  1. Heart block
  2. Extrasystole
  3. Paroxysmal tachycardia
  4. Atrial flutter
  5. Atrial fibrillation
  6. Ventricular fibrillation

Physiology 2nd Semester (7 decks)

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