Heart Anatomy and Function Flashcards

Flashcards to review the anatomy, physiology, and electrical activity of the heart.

Heart

The pump of the cardiovascular system that creates pressure to move blood.

Mediastinum

The region of the chest where the heart lies.

Pericardial Sac

The sac that contains the heart and provides a separate chamber for it to beat in.

Fibrous Pericardium

The outer, tougher layer of the pericardial sac.

Serous Pericardium

The inner, smooth layer of the pericardial sac; a serous membrane.

Parietal Pericardium

The layer of the serous pericardium that lines the body chamber.

Visceral Pericardium (Epicardium)

The layer of the serous pericardium that covers the surface of the heart itself.

Myocardium

The thick, muscular layer of the heart containing cardiac muscle cells.

Endocardium

The serous membrane that serves as a protective inner lining for the chambers and valves of the heart.

Fibrous Skeleton

The layer of dense connective tissue between the atria and ventricles that separates the myocardium and anchors the heart valves.

Atria

The two chambers of the heart that contract simultaneously to pump blood into the ventricles.

Ventricles

The two chambers of the heart that contract simultaneously to pump blood out of the heart.

Interatrial Septum

The thin septum between the two atria.

Interventricular Septum

The thicker septum between the two ventricles.

Trabeculae Carneae

Distinct ridges that line the ventricles and aid in strengthening them.

Pectinate Muscles

Ridges of muscle that line the atria.

Atrioventricular Valves (AV Valves)

Valves that allow blood to enter the ventricles and prevent backflow into the atria.

Semilunar Valves

Valves that allow blood to leave the ventricles into the arteries but prevent backflow into the ventricles.

Tricuspid Valve

The valve between the right atrium and right ventricle.

Pulmonary Semilunar Valve

The valve that allows blood to leave the right ventricle and enter the pulmonary trunk (artery).

Bicuspid (Mitral) Valve

The valve between the left atrium and left ventricle.

Aortic Semilunar Valve

The valve that prevents blood from flowing backward when the left ventricle relaxes.

Pulmonary Circuit

The circuit that carries blood to and from the lungs.

Systemic Circuit

The circuit that carries blood to and from the body.

Automaticity

The heart's ability to contract without innervation from the CNS.

Intrinsic Conduction System

The system within the heart that allows it to have spontaneous action potentials and spread them to the rest of the heart.

Sinoatrial (SA) Node

The pacemaker of the heart, responsible for initiating the electrical activity.

Atrioventricular (AV) Node

The node that delays the electrical activity briefly before sending it on to the ventricles; serves as the connecting point between atria and ventricles.

Bundle of His (AV Bundle)

The bundle that transfers the electrical impulse to the ventricles.

Right and Left Bundle Branches

The branches that carry the electrical impulse down the interventricular septum.

Purkinjie Fibers

The fibers that spread the electrical impulse over the ventricles, causing them to contract as a unit.

Pacemaker Potential

The slow depolarization in SA node cells due to leaky Na+ channels.

Depolarization (SA Node)

Rapid Ca++ influx through voltage-gated channels in SA node cells.

Repolarization (SA Node)

K+ channels opening around 0 mV, causing repolarization in SA node cells.

Internodal Pathway

Helps spread depolarization across the atria.

Fastest Pacemaker Always Wins

The rule that the SA node's higher bpm normally suppresses the pacemaker activity of the AV node.

Cardiac Muscle Action Potential

A special action potential that prevents heart cramps.

Plateau Phase

The period during cardiac muscle action potential where slow Ca++ channels open and Ca++ enters the cell, prolonging repolarization.

Refractory Period (Cardiac)

The long delay created by the plateau phase, allowing cardiac cells to relax fully before another contraction.

Electrocardiogram (EKG)

A means of looking at the electrical activity of the heart by measuring electrical differences on the surface of the skin.

P Wave

The part of the EKG that occurs as the atria are depolarized.

QRS Complex

The part of the EKG that occurs as the ventricles are depolarized.

T Wave

The part of the EKG that signals repolarization of the ventricles.

Bradycardia

A slow heart rate of less than 60 bpm.

Tachycardia

A resting heart rate of over 100 bpm.

Ectopic Pacemaker

Cells that undergo their own pacemaker activity at a faster rate than the SA node.

Ventricular Tachycardia

Ectopic pacemaker in the ventricles that causes them to beat at a faster rate independently of the atria.

Ventricular Fibrillation

Continuous recycling of ventricular waves through the myocardium, producing random contractions that fail to pump blood effectively.

Defibrillation

A powerful shock given to depolarize all heart cells at the same time, resynchronizing them to resume rhythmic contractions.

Conduction Blocks

Abnormal transmission of the impulse through the AV node.

First Degree Block

A subtle conduction block characterized by a prolonged P-R interval on the EKG.

Second Degree Block

A conduction block where the AV node fails to pass the impulse along to the ventricles, resulting in some P waves not followed by a QRS complex.

Third Degree Block

A conduction block where there is no transmission of the signal into the ventricles, resulting in no correlation between P waves and QRS complexes.

Gallons of blood pumped by heart per year

700,000

Times heart beats per day

100,000

Serous Fluid

Lubricating fluid secreted by serous membranes in the pericardial sac.

Function of Fibrous Skeleton

Separates myocardium of atria and ventricles, allowing them to contract on a different schedule. Also serves an anchor point for the heart valves.

Superior and Inferior Vena Cava

The veins that collect deoxygenated blood and return it to the right atrium.

Pulmonary Veins

The veins that return oxygenated blood from the lungs to the left atrium.

SA Node Location

Right atrium near where the superior vena cava enters.

Location of AV Node

fibrous skeleton of the heart. Connects atria and ventricles

Heart Rate set by SA node

70 -80 beats per minute (bpm)

Backup Heart Rate set by AV Node

40-50 bpm

Skeletal Muscle Cramps

Muscle contracts and stays contracted.

Resting potential of Myocardial cells

-90 mV

EKG Records

depolarization and repolarization of the heart as a whole that occur as the atria and ventricles relax and contract.

EKG can NOT detect?

heart murmurs and valve disorders

Fitness indicated by?

slow heart rate in athletes = Bradycardia

Atrial fibrillation

NOT life threatening

First degree conduction block

prolonged P-R interval

Second degree conduction block

QRS complexes are preceded by a P wave, but not all P waves result in a QRS

Third degree conduction block

no correlation between P waves and QRS complexes

Action Potential

the change in electrical potential associated with the passage of an impulse along the membrane of a muscle cell or nerve cell.

Depolarization

loss of the difference in charge between the inside and outside of the plasma membrane of a muscle or nerve cell due to a change in permeability and migration of sodium ions to the interior.

Repolarization

the reestablishment of polarity, especially the return of a cell's membrane potential to resting potential after depolarization.

Cardiac Muscle Cells

Branched, striated cells electrically connected by gap junctions.

Valve

a structure in the heart for maintaining one-way blood flow

Septum

a partition separating two chambers, such as that between the atria or ventricles of the heart.

The heart's location

lies in a region of the chest called the mediastinum

Size of the heart

described as being the size of a fist

Serous membrane

always come in pairs- the parietal pericardium and visceral pericardium that covers the surface of the heart itself

SA node description

a small group of cells located up in the right atrium near where the superior vena cava enters. It is about 15 mm long x 5mm wide and only 1.5 mm deep.

Ectopic pacemaker cause

abnormal SA node function, drugs

The EKG 3 basic parts:

the P wave, the QRS complex, and the T wave

The heart is capable of contracting

without innervation from our CNS

Epicardium capillaries

serous membrane with capillaries, nerve fibers, lymph capillaries

Heart beats on its own

it works on its own because there are special cells in the heart that are capable of having spontaneous action potentials which are then spread to the rest of the heart

Purkinjie fibers surrounding the Right and Left ventricles

allows them to contract as a single unit

SA node special cells

do not require any stimulus to get their action potentials going

Pacemakers

monitor the SA node for action potentials, then electrically stimulate the AV node at the same rate after a brief delay.

Myocardial cells undergo?

: action potentials of their own and then contract, pumping the blood from the ventricles.

Na+ rushes in

causing the membrane potential to hit just over +20 mV

EKG

performed by measuring electrical differences found on the surface of the skin as the heart beats.

SA node will cause

P waves at a rate of 70 –80 bpm

AV node will have pacemaker

activity at 40-50 bpm

AV node

One of the things it does it slows the electrical impulse down, so that the atria will contract and empty blood into ventricles before they begin their contraction

SA node fails

AV node as a backup, you can still live with a heart rate of 40-50 bpm

Cardiac Muscle Cell

must contract then relax fully before it can be stimulated again

intrinsic

built into the heart

Action potentials in ventricles

are spread over the ventricles so they contract as a unit