Chapter 13: The Cardiovascular System: Cardiac Function

cardiovascular system

The transport system of the body responsible for carrying oxygen and nutrients to the body and carrying away carbon dioxide and other wastes; composed of the heart, blood vessels, and blood.

pericardium

Double-layered membrane surrounding the heart.

epicardium

outermost layer of the heart

myocardium

muscular, middle layer of the heart

endocardium

inner lining of the heart

atrium

Each of the two upper chambers of the heart that receives blood that comes into the heart

ventricle

one of two lower chambers of the heart

atrioventricular (AV) valves

Valves located between the atrial and ventricular chambers on each side of the heart, prevent backflow into the atria when the ventricles are contracting.

semilunar valves

pulmonary and aortic valves located between the right ventricle and the pulmonary artery and between the left ventricle and the aorta

interventricular septum

partition between the right and left ventricles

base of heart

the posterior part of the heart formed by both atria, but mainly the left

apex of the heart

tip of the heart pointing down toward the 5th left intercostal space

artery

A blood vessel that carries blood away from the heart

capillary

A tiny blood vessel where substances are exchanged between the blood and the body cells.

vein

A blood vessel that carries blood back to the heart.

erythrocytes

another name for red blood cells

leukocytes

another name for white blood cells

platelets

a small colorless disk-shaped cell fragment without a nucleus, found in large numbers in blood and involved in clotting

plasma

liquid portion of blood

pulmonary circuit

system of blood vessels that carries blood between the heart and the lungs

systemic circuit

Circuit of blood that carries blood between the heart and the rest of the body.

series blood flow

The series of blood flow-related events that occur from the beginning of one heartbeat to that of the next

parallel blood flow

1.) Each organ is fed by a separate artery, and each receives fully oxygenated blood

2.) Blood flow to the organs can be independently regulated

-Systemic circulation

coronary arteries

blood vessels that branch from the aorta and carry oxygen-rich blood to the heart muscle

myocardial infarction

the occlusion of one or more coronary arteries caused by plaque buildup (heart attack)

right AV valve

The valve between the right atrium and right ventricle; the tricuspid valve

left AV valve

bicuspid valve

aortic valve

The semilunar valve separating the aorta from the left ventricle that prevents blood from flowing back into the left ventricle.

pulmonary valve

valve positioned between the right ventricle and the pulmonary artery

cardiac cycle

A complete heartbeat consisting of contraction and relaxation of both atria and both ventricles

pacemaker cells

heart cells that regularly produce spontaneous electrical impulses

conduction fibers

specialized muscle cells that rapidly conduct action potentials through the heart

contractile cells

produce contractions that propel blood

autorhythmic cells

Cells fire spontaneously, act as pacemaker and form conduction system for the heart

SA (sinoatrial) node

the pacemaker of the heart, located in the wall of the right atrium, that sets the rate and timing at which all cardiac muscle cells contract

AV node

(atrioventricular node) region of the heart between the right atrium and right ventricle from which electrical impulses spread to the ventricles during a heartbeat

gap junctions

Points that provide cytoplasmic channels from one cell to another with special membrane proteins. Also called communicating junctions.

intercalated disks

Specialized cell junctions in the myocardium where one muscle cell connects to the next.

AV node delay

slowing of electrical conduction through the AV node that allows atria to complete contraction before the ventricles begin

bundle of His

a bundle of modified heart muscle that transmits the cardiac impulse from the atrioventricular node to the ventricles causing them to contract

left and right bundle branches

branches from atrioventricular bundle, take signal to apex of heart

Purkinje fibers

specialized conductive fibers located within the walls of the ventricles

pacemaker potentials (prepotentials)

initiate the action potentials that spread throughout the heart to trigger its rhythmic contractions

funny channels

important part of the electrical conduction system of the heart and form a component of the natural pacemaker

T-type voltage-gated calcium channels

Channels that allow cardiac pacemaker cells to reach threshold.

L-type voltage gated Ca channels

transmembrane ion channel proteins that selectively conduct calcium ions through the cell membrane in response to the membrane potential during depolarization

depolarization

The process during the action potential when sodium is rushing into the cell causing the interior to become more positive.

repolarization

Return of the cell to resting state, caused by reentry of potassium into the cell while sodium exits the cell.

voltage-gated Na+ channels

membrane channels open, bringing about the depolarization phase of the action potential.

voltage-gated K+ channels

open when a particular membrane potential is reached; closed at resting potential

plateau

During the plateau phase of the action potential, calcium ions flow down this steep concentration gradient and enter the myocyte

summation

increased force of contraction by a skeletal muscle fiber when a twitch occurs before the previous twitch relaxes

refractory period

the time following an action potential during which a new action potential cannot be initiated

T tubules

Also called transverse tubules, these are deep invaginations of the plasma membrane found in skeletal and cardiac muscle cells. These invaginations allow depolarization of the membrane to quickly penetrate to the interior of the cell.

sarcoplasmic reticulum

specialized endoplasmic reticulum of muscle cells

troponin

A protein of muscle that together with tropomyosin forms a regulatory protein complex controlling the interaction of actin and myosin and that when combined with calcium ions permits muscular contraction

crossbridge cycling

1. Crossbridge formation

2. Power stroke

3. Release of myosin head

4. Reset myosin head

excitation-contraction coupling

sequence of events from motor neuron signaling to a skeletal muscle fiber to contraction of the fiber's sarcomeres

electrocardiogram (ECG or EKG)

A recording of the electrical activity of the heart

arrhythmia

Abnormal heart rhythm

P wave

depolarization of the atria

QRS complex

ventricular depolarization and atrial repolarization

T wave

ventricular repolarization

sinus rhythm

the normal (optimal) heart rhythm arising from the sinoatrial node

tachycardia

Abnormally rapid heartbeat

bradycardia

abnormally slow heartbeat

ventricular filling

Phase of the cardiac cycle in which the ventricles expand, their pressure drops, and the AV valves open and blood flows into the ventricles

systole

contraction phase of the heartbeat

diastole

relaxation phase of the heartbeat

ventricular fibrillation

the rapid, irregular, and useless contractions of the ventricles

isovolumetric contraction

an event occurring in early systole during which the ventricles contract with no corresponding volume change

ventricular ejection

the period of time when both semilunar valves are open and blood begins to leave the heart

isovolumetric relaxation

period when all four valves are closed and ventricular blood volume does not change

systolic pressure

Blood pressure in the arteries during contraction of the ventricles.

diastolic pressure

occurs when the ventricles are relaxed; the lowest pressure against the walls of an artery

mean arterial pressure

pressure forcing blood into tissues, averaged over cardiac cycle

End Diastolic Volume (EDV)

volume of blood in each ventricle at end of ventricular diastole

Stroke Volume (SV)

The volume of blood pumped forward with each ventricular contraction.

1st heart sound (lub)

closure of AV valves

2nd heart sound (dub)

closure of semilunar valves

heart murmur

an abnormal sound from the heart produced by defects in the chambers or valves

echocardiogram

ultrasound of the heart

Cardiac Output (CO)

measurement of the amount of blood ejected per minute from either ventricle of the heart

Heart Rate (HR)

number of heart beats per minute

autonomic nervous system

the part of the peripheral nervous system that controls the glands and the muscles of the internal organs (such as the heart). Its sympathetic division arouses; its parasympathetic division calms.

sympathetic nervous system

the division of the autonomic nervous system that arouses the body, mobilizing its energy in stressful situations

parasympathetic nervous system

the division of the autonomic nervous system that calms the body, conserving its energy

vagus nerve

the tenth cranial nerve that innervates digestive organs, heart and other areas

epinephrine

adrenaline

ventricular contractility

Capacity of heart ventricles to contract.

preload

The precontraction pressure in the heart as the volume of blood builds up.

Starling's Law

The more the heart is filled during diastole the more forcefully it contracts

afterload

The force or resistance against which the heart pumps.

autoregulation

the ability of tissues to regulate their own blood supply

length-tension curve

the curve that accounts for the active and passive elements of muscle tension and dictates that optimal tension is developed at one point known as the resting length, the point in its range where peak torque is developed

congestive heart failure

A condition resulting from the heart's inability to pump out all the blood that returns to it; blood backs up in the veins leading to the heart, causing an accumulation of fluid in various parts of the body