Class 10 Cardio

ens 304

What are the 4 chambers of the heart?

Left Atrium, Right Atrium, Left Ventricle, Right Ventricle

Where does the right atrium and ventricle receive and pump blood from?

Receives: from systemic circulation

Pumps: to pulmonary circulation

Where does the Left atrium and ventricle receive and pump blood from?

Receives: from pulmonary circulation

Pumps: to systemic circulation

What do the valves in the heart do?

Prevent backflow of blood

The “lub-dub” sound of the heart is caused by?

Closure of valves

Myocardium

Muscle of the heart, composed by cardiomyocytes (cardiac muscle cells)c

Cardiomyocyctes

Single nucleated cells connected by intercalated disks

Intercalated disks

Allow electrical signals to flow between cells

Do cardiomyocytes have different “types” like in skeletal muscle?

NO

Does myocardium contract as multiple units or a single unit?

Single unit

Calcium-induced calcium release

Depolarization of the membrane allowing extracellular calcium influx

Is calcium activation of the myofilaments similar (not equal) to skeletal muscle? And what proteins are similar?

YES they are similar. Myosin, actin, troponin, SERCA

Does myocardium contract by stimulation of motor neurons?

NO

Where is the location of cardiac muscle?

Heart and adjacent portions of large blood vessels

What kind of contraction does cardiac muscle do?

COntinuous, rhythmic contraction through calcium-induced calcium release

Is contraction of cardiac muscle voluntary or involuntary?

Involuntary

Which of the following statements about cardiac muscle contraction is TRUE?

A. Cardiomyocytes have different fiber “types” similar to skeletal muscle

B. The myocardium contracts only when stimulated by motor neurons

C. Depolarization of the membrane allows extracellular Calcium influx, triggering calcium-induced calcium release.

D. Myocardium contracts as independent units rather than a single unit.

C. Depolarization of the membrane allows extracellular Calcium influx, triggering calcium-induced calcium release.

What specialized cardiac muscle cells serve as pacemakers of the heart?

SA node, AV node, AV bundle, Purkinje Fibers

Electrocardiogram (ECG or EKG)

P Wave: Atria contraction

-Atrial depolarization > atrial contraction > stimulation of ventricles

-Electrical impulse travelling from the SA node.

QRS complex: Contraction of ventricle & relaxation of atria

-Ventricular depolarization: greater electrical signal change

-Electrical impulse spreads from AV node to the Purkinje fibers

T wave: Relaxation of ventricle

-Ventricular repolarization 

Parasympathetic Nervous system: Extrinsic control of HR

-Mostly from vagus nerve

-PS neurotransmitter release ACh

-hyperpolarizated membrane

-Heart primarily under parasympathetic control during resting

Sympathetic Nervous system: Extrinsic control of HR

-Sympathetic neurotransmitter norepinephrine (NE)

-Increase rate of depolarization of SA node

Endocrine system: extrinsic control of HR

-Hormone epinephrine (EPI) from adrenal medulla

How do epinephrine (EPI) and norepinephrine (NE) act on cardiomyocytes?

• Membrane depolarization

• Myosin–actin shortening

• SR calcium release

• SR calcium uptake via SERCA

• increases rate of contraction and relaxation

How does heart rate change with exercise intensity?

Heart rate increases proportionally/linear to the body’s oxygen consumption (exercise intensity).

What happens to the HR–VO₂ relationship near maximal heart rate (HRmax)?

Lower increase in HR until it reaches the max HR.

What does HRmax indicate about exercise intensity?

HRmax occurs near VO₂max, making it a good predictor of exercise intensity at maximum aerobic capacity.

What causes variations in heart rate during exercise?

Variations are due to changes in the time interval between consecutive heartbeats (R-R interval), known as heart rate variability.

Time between peaks.

Resting HR

-Obtained before rising from bed in the morning

-Decreases with exercise training due to greater activation of the vagal tone.

-increasing HR variability

MAximal HR

-decreases through age.

-220-age

HR reserve (HRR)

The difference between a person’s HR max and their HR rest.

Used to predict the % VO2 reserve.