Ch 9.1 Cardiovascular Physiology

What kind of pump is the heart?

Pulsatile pump

The cardiovascular system is a ______ system?

closed

Systemic circulation

Provides oxygen and nutrients to the body while pulling away carbon dioxide

Pulmonary circulation

System that oxygenates the blood and expels carbon dioxide

The purpose of the circulatory system is to…?

Keep extracellular fluid in homeostasis, regulates pH, [O2], and [CO2]

Plasma

Fluid portion of the blood

Mostly water and contains ions, fats, amino acids, hormones, et.

What composites the formed elements of blood?

Red blood cells

White blood cells

Platelets

Hematocrit

% of blood volume that is red blood cells

What makes up extracellular fluid?

Plasma and interstitial fluid

Valves

Prevent backwards flow of blood, found in heart and veins

What are the 2 special arrangements of circulation?

Blood supply to the digestive tract and liver (Hepatic portal vein)

2 capillary beds in the kidneys

Systolic

Top part of blood pressure

Represents the pressure against the arterial walls during heart contraction

Diastolic

Bottom part of blood pressure

Represents arterial pressure when the heart isn’t contracting

Pressure gradient

Necessary for blood circulation

Formed by pulsatile contraction of the heart and aided by valves within the veins

How does the diastolic pressure of the heart differ from arteries?

Heart is empty/filling during diastoly while arteries have blood due to heart valves being closed

Arteries have a higher diastolic pressure than the heart

Majority of species have an average blood pressure that sits around?

120/80

Atria

Top chambers of the heart

Ventricles

Bottom chambers of the heart

The right side of the heart pumps blood to the…

Lungs

The left side of the heart pumps blood to the…..

Body

Coronary circulation

Part of the bodies circulation that supplies the heart itself, stem off the aorta

Pericardium

Membrane enclosing the heart, consisting of an outer fibrous layer and an inner double layer of serous membrane

Parietal pericardium

Part of the serous pericardium, fused and inseparable from the fibrous pericardium

Visceral pericardium

Layer of the serous pericardium that is part of the pericardium

Pericardial cavity

Fluid filled space that sits between the visceral and parietal pericardium

Pericardial effusion

When the pericardial cavity fills with excess fluid “choking” the heart

Endocardium

Inner most layer of tissue that lines the chambers of the heart, similar to endothelial cells that lines the blood vessels

Provides protection to the valves and heart chambers

Myocardium

Muscular tissue responsible for the contraction of the heart

Epicardium

A serous membrane that forms the innermost layer of the pericardium and the outer surface of the heart

What are the 3 type of cardiac muscle?

Atrial

Ventricular

Specialized excitatory and conductive

What is the structure of cardiac muscle

Striated myofibrils in a lattice with cells electrically connected through gap junctions and joined with intercalated disks

What unique attribute of cardiac muscle aids in the pulsatile nature of the heart?

Electrically connected allowing action potentials to propagate consistently

Order of blood flow through the heart

Lungs → pulmonary veins → left atrium → left ventricle → aorta → body tissues → vena cava → right atrium → right ventricles → pulmonary arteries → lungs

Ventricular muscles have a very consistent ____ _____ _____ meaning they do not fire on their own like the rest of the heart can

Resting membrane potential

What unique aspect of cardiac muscle contraction prevents the heart from twitching?

Slow repolarization due to increased calcium release after depolarization

What is the resting membrane potential of cardiac muscle?

-85 to -95 mV

What channels cause depolarization in cardiac muscle?

Voltage gated sodium and potassium channels

“L” type calcium channels

Channel responsible for plateau in cardiac action potentials

Slowly releases calcium during the depolarization into repolarization phase keeps membrane potential high

Phase 0 (depolarization)

Voltage gated fast sodium channels open

Causes quick depolarization

Phase 1 (initial repolarization)

Fast sodium channels close

Voltage gated fast potassium channels open allowing potassium out and beginning repolarization

Phase 2 (plateau)

“L” type calcium channels open and fast potassium channels close

Calcium channels slow the rate of repolarization

Phase 3 (rapid repolarization)

“L” type calcium channels close and slow potassium channels open repolarizing the cell

Absolute refractory period

Period at which repolarization is occurring by membrane potential is still high meaning another action potential cannot occur

Relative refractory period

Period during repolarization where resting membrane potential has not been reached but another action potential could occur

What are the 2 sources of calcium for cardiac muscle

Extracellular and intracellular

What it’s he process of contraction coupling in cardiac muscle?

Voltage gated L type calcium channels close to the SR they release calcium which triggers the calcium sensitive ryanodine receptor within the SR. This releases more calcium which bind to troponin initiating contraction

What is unique about cardiac muscle ryanodine receptors?

They are calcium sensitive and are calcium induced calcium release

What is the relaxation process of ventricular muscle?

Voltage gated calcium channels close and potassium channels open and the cells repolarize

Once calcium stops entering the cell ryanodine receptor closes meaning no more calcium is released from the SR

Calcium is pumped out through Calcium ATPase and pumped back into the SR through SERCA

SERCA

Calcium pump within the SR that pumps calcium back into the SR

Which section of the heart has a shorter action potential?

Atria

Duration of contraction in cardiac muscle is directly tied to….

Duration of action potential