Chapter 19: Cardiovascular System - Heart Physiology

auto-rhythmicity

The term for: generating rhythmic action potential independent of the nervous system

• the heart is auto-rhythmic

auto-rhythmicity

What triggers muscular contraction from initiating action potential between cardiac cells?

myocardial contractile cells and myocardial conducting cells

What are the two types of cardiac muscle cells

intercalated discs

What connects the contractile cells of the heart?

striated

Heart cells are marked with parallel bands; grooved

striated

Cardiac cells are ______, meaning they have actin, myosin, tropomyosin, and troponin

myocardial conducting cells

Which cardiac cell is

• neuron-like

• auto-rhythmic

• has a pace set by the fastest cell

myocardial conducting cells

What cardiac has the following components:

• sinoatrial node (SA)

• atrioventricular node (AV)

• atrioventricular bundle

• right and left bundle branches

• Purkinje fibers

the fastest one (first one to generate an action potential) → sinoatrial node (SA)

The components of conducting cells (i.e. SA, AV, Purkinje fibers, etc.) all generate an action potential, but which one sets the pace for the rest?

sinoatrial node (SA)

What is the fastest component of myocardial conducting cells to generate the first action potential?

sinoatrial node (SA)

What is known as the pacemaker node?

myocardial conducting cells

Action potential starts through what type of cardiac cell?

myocardial contractile cells

The action potential from the conducting cells spreads where?

tetany

What does it mean when the heart stays contracted?

the plateau phase from the slow Ca²⁺ channels and K⁺ channels opening

What prevents the heart from going into tetany?

electrocardiogram (EKG or ECG)

What is the tracing of cardiac electrical activity?

• composite of conducting & contacting cells

typically 12

How many electrical leads are placed on a patient for an ECG/EKG

P wave

On the EKG tracing, what wave occurs first as a result of atrial depolarization?

atrial depolarization

P wave results from this; this is when the SA node depolarizes, and it spreads throughthe atrial myocardium.

QRS complex

On the EKG tracing, what wave occurs first as a result of ventricular depolarization AND atrial repolarization?

QRS complex

At what point of the EKG tracing do the atria repolarize?

T wave

On the EKG tracing, what wave occurs first as a result of ventricular repolarization?

P-Q segment

On the EKG tracing, what is associated with atrial cells' plateau (atria are contracting)?

S-T segment

On the EKG tracing, what is associated with ventricular plateau (entire ventricular myocardium depolarized)

P-R interval

On the EKG tracing, what is the interval from the start of atrial depolarization to the start of the QRS complex?

Q-T interval

On the EKG tracing, what is the interval that begins ventricular depolarization through ventricular repolarization?

cardiac cycle

What is the sequence of events in one heartbeat?

systole

What is the contraction of the heart

diastole

What is the relaxation of the heart

ventricular filling

When does the cardiac cycle "begin"?

ventricular relaxation

When does the cardiac cycle "end"?

atrial systole

Depolarization of the atria leads to...

atrial diastole

Repolarization of the atria leads to...

stroke volume (SV)

What is the volume of blood that is ejeted out of the ventricles during ventricular contraction?

end diastolic volume (EDV)

What is the volume of blood in each ventricle at end of ventricular diastole

end systolic volume (ESV)

What is the volume of blood remaining in each ventricle after systole

S1 sound

What is the "lub" sound?

S1 sound

Which heart sound is caused by the closure of the atrioventricular (AV) valves?

mitral valve

What is the noisiest atrioventricular valve?

S2 sound

What is the "dub" sound?

S2 sound

Which heart sound is caused by the closure of the semilunar valves?

aortic valve

What is the noisiest semilunar valve?

S3 sound

Which heart sound is abnormal, caused from blood sloshing

(not tested)

S4 sound

Which heart sound is always abnormal, caused by blood pushing against the stiff left ventricle?

ECG tracing

What can be used to measure heart rate?

dysrhythmia

Define the diagnosis:

• an abnormal cardiac rhythm

bradycardia

Define the diagnosis:

• a type of dysrhthymia

• < 60 bpm

• abnormally slow resting heart rate

tachycardia

Define the diagnosis:

• a type of dysrhthymia

• > 100 bpm

• abnormally fast resting heart rate

heart block

Define the diagnosis:

• a type of dysrhthymia

• conduction system failure

•

fibrillation

Define the diagnosis:

• a type of dysrhthymia

• uncontrolled contractions

• "heart fluttering"

stroke volume (SV)

What is the volume of blood pumped forward with each ventricular contraction?

end diastolic volume (EDV) - end systolic volume (ESV)

What is the stroke volume equation (SV)?

ejection fraction (EF)

What is the measurement of the volume percentage of left ventricular contents ejected with each contraction?

stroke volume (SV) / end-diastolic volume (EDV)

What is the ejection fraction equation?

cardiac output

What is the volume of blood pumped by heart per minute?

HR x SV

What is the formula for cardiac output (CO)?

preload, contractility, afterload

What factors affect stroke volume (SV)

end diastolic volume (EDV)

Preload is directly proportional to _____________

Frank-Starling law

What's the rule where the greater the stretch, the stronger is the heart's contraction?

direct

Preload has a ____________ relationship with stroke volume

increases

If you increase preload... end diastolic volume ________, which _________ stroke volume (SV)

increases

If you increase duration of diastole... end diastolic volume ________, which _________ stroke volume (SV)

decreases

If the heart rate exceeds 160 bpm, the heart is beating to hard for the ventricles to fill with blood. This ________ stroke volume

decreases

If there is impaired venous return, this _________ stroke volume

direct

Contractility has a ________ relationship with stroke volume

increases

Stronger contractility ________ stroke volume

+ inotropic agents

What type of agents increase contractility?

What is the type of inotropic agent?

• increased Ca2+

• increased glucagon

• sympathetic stimulation

• digitalis

- inotropic agents

What type of agents decrease contractility?

- inotropic agents

What is the type of inotropic agent?

• increased K+ and H+

• sympathetic inhibition

• calcium channel blockers

afterload

What factor affecting SV is significant in HTN patients?

afterload

What is the resistance in the great vessels from accepting the blood that the vesicles are attempting to eject.

indirect

Afterload has a _______ relationship with stroke volume

heart rate (HR)

What is the number of beats per minute?

75 bpm

What is the normal heart rate?

< 60 bpm

What is the heart rate for someone with bradycardia?

> 100 bpm

What is the heart rate for someone with tachycardia?

+ chronotropic effects

What increases the heart rate?

- sympathetic stimulation

- nicotine, caffeine, thyroid hormone

- chronotropic effects

What decreases the heart rate?

- parasympathetic stimulation

- K+ and Ca2+ (hyper)

parasympathetic

Which nervous system sets the cardiac tone, in other words, slows down the pacemaker cells?

parasympathetic

Which nervous system DECREASES your heart rate?

sympathetic

Which nervous system INCREASES your heart rate?

sympathetic

Which nervous system increases the strength of contraction of the chambers in the heart?

coronary artery disease

Define the diagnosis

• The condition for atherosclerosis of coronary arteries

• Ischemia

• angina pectorsis

• depressed S-T segment

atherosclerosis

Define the diagnosis

• hardening of the arteries

ischemia

Define the diagnosis

• lack of blood supply

angina pectoris

Define the diagnosis

• chest pain that results when the heart does not get enough oxygen

myocardial infarction (MI)

Define the diagnosis

• heart attack

• cardiac muscle tissue death

• results in chest & left arm pain

• elevated S-T segments

• cardiac enzymes are elevated in the blood

heart failure

Define the diagnosis

• cardiac insufficiency

• a chronic condition in which the heart is unable to pump out all of the blood that it receives

• caused multiple things: cardiomyopathy, atherosclerosis, chronic hypertension, myocardial infarction (MI)

right-sided heart failure

Define the diagnosis:

• systemic circulation back-up

• lower extremity edema

left-sided heart failure

Define the diagnosis:

• pulmonary circulation back-up

• pulmonary edema