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Physiology 2nd Semester > PHS 206 CVS > Flashcards

PHS 206 CVS Flashcards

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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
What do chemoreceptors do?
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.
26
Describe the sympathetic influence on the neural regulation of the heart
through celiac plexus to heart •secretes norepinephrine and epinephrine •increases force of contractions •causes tachycardia and increased contractility
27
Describe the parasympathetic influence on the neural regulation of the heart
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
28
Tachycardia
Increase in heart rate beyond what is normal for sex and age
29
Action of cardiac accelerator nerves
Sympathetic Fibers •Innervate SA node & ventricles •Increase heart rate •Increase contractility •Increase pressure
30
Action of the vagus nerve
Parasympathetic Nerve •Innervates SA node & AV node •Releases acetylcholine •Slows heart rate •Lowers pressure
31
Describe the cortical influences on the heart
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
Describe the cortical influence of the heart
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
Peripheral influences on the heart rate
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
Factors affecting blood flow resistance
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
What does the opening of “dormant” capillaries do during exercise?
–Increases blood flow to muscle –Reduces speed of blood flow –Increases surface area for gas exchange
36
What are the Local Factors Resulting in Dilation?
•↓ 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
What is cardiac output?
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
Cardiac output is a determining factor during endurance activities. Describe how cardiac output is increased during endurance activities
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
Describe heart Regulation from Rest to Exercise
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
Vascular heart diseases include
Pericarditis Myocarditis Endocarditis (most common) due to bacterial infection
41
Where is the cardiac center
The medulla and is influenced by information form the cerebral cortex
42
On an ECG, what event occurs at the p wave?
Atrial depolarization
43
On an ECG, what event occurs at the QRS complex
Ventricular depolarization
44
 On an ECG, what event occurs at the T wave
Ventricular repolarization
45
Difference between action potential and impulse?
Electrical impulse is the transmitted action potential (stimulation of excitable tissue)
46
SA node rate is approximately?
90bpm
47
What is an electro cardiogram?
Graphical representation of the electrical activity of the heart
48
What is an electrocardiograph
A machine that reads ECG
49
What is electrocardiography
The process of taking an electrocardiogram
50
Explain the two sounds of the heart
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
Abnormal heart sound within and outside of the heart is known as
Within: murmur Outside: bruite
52
Explain the bainbridge reflex
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
What are the reasons for blood pressure regulation?
– to keep blood flow constant to vital organs – for the maintenance of homeostasis
54
Types of regulatory mechanisms of blood pressure regulation
Nervous mechanism Renal mechanism Hormonal mechanism Local mechanism
55
Describe the control of blood pressure
* 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
What is sinus tachycardia?
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
What is sinus bradycardia?
A reduction in the discharge of impulse from the SA node resutling n decrease heart rate (less than 60bpm)
58
Define arrhythmia
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
Classification of arrhythmia
Normotropic arrhythmia ectopic arrhythmia
60
Types of Normotropic arrhythmia
Sinus arrhythmia sinus tachycardia sinus bradycardia
61
What is sinus arrhythmia
Is a normal rhythmical increase and decrease in heart rate in relation to respiration
62
Describe the conducting system of the heart
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
Rate of production of rhythmic impulses by different parts of the heart is
 Atrial muscle: 40–60/min and  Ventricular muscles: 20–40/min.  SA node: 70–80/min,  AV node: 40–60/min
64
Clinical significance of contractility
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
What is pulmonary circulation
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
What is the Systemic circulation
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
Whats is blood pressure
Blood pressure is the pressure of circulating blood against the walls of blood vessels.
68
Blood pressure can be expressed in the following terms
– 1. Systolic blood pressure – 2. Diastolic blood pressure – 3. Pulse pressure – 4. Mean arterial blood pressure
69
What are the Physiological variations of BP
* 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
What are the Physiological variations of BP
* 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
* Maximum BP occurs____
in the aorta during the systolic ejection phase (systolic pressure (Ps))
72
minimum aortic pressure is reached during_____
the isovolumic contraction phase while the aortic valves are closed (diastolic pressure (Pd))
73
Formula for pulse pressure
Ps – Pd = pulse pressure (PP),
74
Formula for MAP
Mean arterial blood pressure = Diastolic pressure + 1/3 PP
75
How to measure BP
Ascultatory: Using a stethoscope and a sphygmomanometer * Palpation * Invasive/cannulla
76
Ectopic arrhythmia
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
Types of ectopic foci
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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