Chapter 19: Cardiovascular System: The Heart

tetany

tension; prolonged, continuous muscle contraction

Cardiac output is normally expressed as ______.

liters per minute

The cardiac center is within the ______.

medulla oblongata

By day 19 (middle of week 3), two endocardial tubes form from ______ in the embryo.

mesoderm

The heart is innervated by the ______ nervous system.

autonomic

Which of the following are part of the cardiac muscle cells? myofibrils T tubules fasciculi sarcolemma

myofibrils T tubules sarcolemma

Cardiac muscle cells contain Ca2+ pumps that keep more Ca2+_________ the cell

outside

The ability to reach threshold without stimulation is called the_____ _____ of the SA node.

pacemaker potential

In the heart, action potentials spread across the ______ of cardiac muscle cells, causing them to contract.

sarcolemma

The two categories of heart valves are ______.

semilunar and atrioventricular

refractory period

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

1. Atrial relaxation and ventricular filling

-Atria and ventricles are relaxed -Blood continues to return to right and left atrium -Passive filling of ventricles, no contraction of the atria -Av valves open because pressure exerted by blood in the atria is greater than the pressure exerted by the blood in the resting ventricles -Semilunar valves are closed because pressure of blood in the ventricles is less than the blood pressure in the arterial trunks.

The anterior part of each atrium is a flaplike extension called a(n) _______________.

Auricle

The tetralogy of Fallot is: A) a condition in which the left and right sides of the heart are completely reversed. B) a developmental disorder that is a cardiac septal defect.Correct an exceptionally fast heart rate. C) an inadequate cardiac output due to poorly contracting heart chambers. D) occlusion of the left coronary artery.

B)

resting membrane potential

The electrical charge difference when the nodal cell is at rest.

Stroke volume(SV) is equal__________ to minus___________ . Use abbreviations for your answers.

EDV-ESV

Describe the location and position of the heart.

Located in the thoracic cavity, posterior to the sternum, left of the body midline.

The movement of ______ is responsible for the depolarization phase of the action potential in cardiac muscle cells.

Na+

The cells of the ___________ act as the heart's pacemaker, which establishes the pace for cardiac activity. atrioventricular (AV) node sinoatrial (SA) node atrioventricular (AV) bundle Purkinje cells

Sinoatrial (SA) node

Fossa ovalis

an oval depression in the wall of the right atrium and occupies the former location of the fetal foramen ovale, which shunts blood from the RA to the LA.

Toward the end of ventricular filling, the left and right ______ contract simultaneously.

atria

The fibrous skeleton of the heart is located between the ______.

atria and ventricles

Differentiate among the three primary types of blood vessels.

1. Arteries: carry blood away from the heart. 2. Veins: carry blood towards the heart. Capillaries: serve as sights of exchange, either between the blood and the alveoli of the lungs or between the blood and the systemic cells.

List the electrical events of an action potential that occur at the sarcolemma.

1. Depolarization: An action potential triggers the opening of fast voltage-gated Na+ channels in the sarcolemma. The resulting resting membrane potential changes from -90 mV to +30 mV. Voltage-gated Na+ channels close to inactivated state. 2. Plateau: Depolarization triggers the opening of voltage-gated K+ channels and K+ leave the cardiac muscle cells. Slow voltage-gated Ca+ channels open and Ca+ enters the cell. The exit of K+ and simultaneous entrance of Ca+ results in no electrical change, and the sarcolemma remains in a depolarized state. 3. Repolarization: Voltage-gated Ca+ channels then close and K+ channels remain open to complete repolarization as K+ exits the cells. Membrane potential of -90 mV is then reestablished.

Describe the conditions at the sarcolemma of cardiac muscle cells at rest.

1. RMP is -90 mV. 2. Contains fast voltage-gated Na+ channels for depolarization and K+ voltage-gated channels for repolarization of membrane. 3. Also contains slow voltage-gated Ca+ channels.

Describe the steps for SA nodal cells to spontaneously depolarize and serve as the pacemaker cells.

1. Reaching threshold: Slow voltage-gated Na+ channels open and changes resting membrane potential from -60 mV to -40 mV 2. Depolarization: change of membrane potential to threshold trigger opening of voltage-gated CA+ channels and moves the membrane potential from -40 to just above positive. 3. Repolarization: Ca+ channels close and voltage-gated K+ channels open. K+ flows out and changes the membrane potential from a positive value back to -60 mV. This triggers the reopening of slow voltage-gated Na+ channels to repeat the process.

Describe the general structure and function of the heart.

1. The heart is a hollow 4-chambered heart serving to pump blood throughout the body. Composed of left and right atria, and left and right ventricles. The right side receives deoxygenated blood and the left side receives deoxygenated blood. 2. Great arteries: pulmonary trunk transports deoxygenated blood from RV to the pulmonary veins to the heart. Aorta transports from LV. Veins: Venae cavae drain into RA. Pulmonary veins drains into the LA. 3. Valves: Atrioventricular (AV) valves: between an atrium and a ventricle. Semilunar valves: between a ventricle and an arterial trunk.

Cell-to-cell junctions, called intercalated discs, contain distinct structural features called gap junctions and T-tubules. myofilaments. desmosomes. branching.

Desmosomes Cell-to-cell junctions, called intercalated discs, contain distinct structural features called gap junctions and desmosomes. Desmosomes are protein filaments that anchor cardiac muscle cells strongly together. Gap junctions are protein pores between adjacent cardiac muscle cells that allows an action potential to move continuously between cardiac muscle cells.

The sarcoplasmic reticulum is more extensive in smooth muscle fibers than in skeletal muscle fibers.

False

List the structure components of the pericardium.

Fibrous pericardium: Dense irregular C.T. that encloses the heart but does not attach to it, but rather is attached inferiorly to the diaphragm and superiorly to the pulmonary trunk and aorta. Parietal layer: simple squamous epithelium and areolar C.T. Adheres to the inner layer of the fibrous pericardium. Visceral layer: composed of simple squamous epithelial cells and areolar C.T. Adheres directly to the heart Pericardial cavity: area between the parietal and visceral layers where serous fluid is found.

The wave of an ECG that reflects the electrical changes of atrial depolarization is the_______ wave.

P

The complex of an ECG that represents the electrical changes that are associated with ventricular depolarization is the_______ complex

QRS

Define autorhythmicity

SA nodal cells are unique in that they exhibit autorhythmicity, meaning that they are capable of depolarizing and firing an action potential spontaneously without external influence.

The sarcolemma of the cardiac muscle cells has fast voltage-gated,_____________ channels that participate in the depolarization of the

Sodium

tendinous cords

String-like tendons used to attach the atrioventricular valves of the heart to the sides of the ventricle wall. Sometimes called heart strings.

Name the three layers of the heart wall and the tissue components of each.

Superficial Epicardium: areolar and adipose C.T. with a simple squamous epithelium. Myocardium: cardiac muscle tissue. Endocardium: Areolar C.T. with a simple squamous layer(endothelium). Deep

vagal tone

The constant inhibition provided to the heart by the vagus nerve. Vagal tone reduces the intrinsic firing rate of the SA node from 120 beats/minute to around 80 beats/minute.

Briefly summarize the mechanical events of muscle contraction.

The entry of Ca+ into the sarcoplasm from the plateau allows Ca+ to bind to troponin and begin cross-bridge cycling within a sarcomere, similar to skeletal muscle contraction. The closing of voltage-gates Ca+ channels, reuptake of Ca+ into the sarcoplasmic reticulum by Ca+ pumps, and removal of Ca+ from the cell by plasma membrane Ca+ pumps decrease Ca+ levels in the sarcoplasm. Calcium is released from troponin with subsequent decrease in cross-bridges between thin and thick filaments. Sarcomeres return to their original resting length.

Describe a nodal cell at rest.

The nodal cells are at rest when the cytosol inside the the nodal cells is relatively negative in comparison to the fluid outside the cells.

Describe the function of the pericardium and the purpose of the serous fluid within the pericardial cavity.

The pericardium helps hold the heart in position and prevents the chambers from overfilling with blood through the pericardial cask which is composed of the fibrous pericardium and the parietal layer. Serous fluid serves as lubrication and reduces friction with each heart beat.

Explain the significance of the plateau phase.

The plateau phase delays repolarization and allows the sarcomeres of cardiac muscle cells to fully contract and relax before following each stimulation. This prevents cardiac muscle cells from exhibiting tetany which would result in the locking up of heart chambers.

Describe the general function of the cardiovascular system.

To transport blood throughout the body to allow for the exchange of substances, respiratory gases, nutrients, and waste products, between the blood of capillaries and the body's cells.

The cells of the cardiac conduction system do not contract. True or False

True

The general function of the cardiovascular system is to transport blood throughout the body to allow the exchange of respiratory gases, nutrients, and waste products between the blood of capillaries and body cells, through the continual pumping action of the heart and vessels. True or False

True

The ventricles begin to fill during ventricular diastole. True or False

True

Cardiac output (CO) is equivalent to heart rate (HR) multiplied by stroke volume (SV). True or False

True Cardiac Output (CO) in mL ejected per minute = Heart Rate (HR), in beats per minute, times the Stroke Volume (SV), in mL ejected per beat. The typical cardiac output for a human heart is: CO = 75 beats per minute (HR) x 70 ml (SV) = 5250 mL per minute or 5.25 liters per minute. This is equivalent to about the human body's total blood volume pumped through the heart per minute.

Identify the components of the ECG recording

Waves 1. P wave: Reflects atrial depolarization that originates in the SA node. Typically lasts 0.008 to 0.1 seconds. 2. QRS complex: Represents ventricular depolarization 3. T wave: Represents ventricular repolarization. Segments P-Q segment: Associated with atrial plateau when the cardiac muscle cells within the atria are contracting. S-T segment: The ventricular plateau when cardiac muscle cells within the ventricles are contracting. Intervals P-R interval: represents the period of time between the beginning of the P wave to the beginning of the QRS deflection. Q-T interval: time from the beginning of the QRS complex to the end of the T wave.

Referred pain, often down the left shoulder and arm, in response to myocardial ischemia is called: myocardial infarction. ischemic pain. angina pectoris. traveling pain.

angina pectoris.

The____________ reflex protects the heart from overfilling.

atrial or Brainbridge

Cardiac output is defined as the amount of blood pumped by one____________ and is expressed as liters per minute.

chamber

Coronary Sinus

enlarged vessel on the posterior aspect of the heart that empties blood into the right atrium

The heart wall consists of three distinctive layers:__________ ,___________ , and endocardium.

epicardium, myocardium

ventricular balance

equal amounts of blood are normally pumped by the two ventricles through the two circulations

Cardiac muscle can use fatty acids,_________ , lactic acid, amino acids, and_______ bodies as fuel sources.

glucose, ketone bodies

As the cardiac cycle begins, the semilunar valves are closed because the pressure exerted by the blood in the ventricles is_________ than the pressure the blood exerts in the great arteries.

less

papillary muscles

responsible for pulling the atrioventricular valves closed by means of the chordae tendineae

The heartbeat is initiated by the specialized cardiac muscle cells of the ______, which are located in the posterior wall of the right atrium, adjacent to the entrance of the ______.

sinoatrial node superior vena cava

The purpose for the delay in the conduction of the action potential from the AV node to the bundle branches of the ventricles is to allow ______, before the ventricles contract.

the atria to complete their contraction

Describe the spread of the action potential through the heart's conduction system.

1. Action potential is distributed throughout both atria via gap junctions and is relayed to the AV node. 2. The action potential is delayed at the AV node. 3. Action potential travels from AV node to the AV bundle, bundle of His, and to the left and right AV bundle branches to the Purkinje fibers. 4. The action potential spreads throughout both ventricles via gap junctions.

Stroke volume (SV) in a healthy adult is approximately ______.

70 mV

The pulmonary trunk receives blood from the right ventricle and conducts it toward the lung. The pulmonary trunk is a(n) artery. capillary. vein.

Artery

______ cells cannot exhibit tetany. Cardiac muscle Skeletal muscle

Cardiac Muscle

_________ _____________is a measure of how effective the cardiovascular system is in fulfilling its function in transporting life supporting substances through the body.

Cardiac output

Perfusion

Circulation of blood within an organ or tissue in adequate amounts to meet current needs of the cells.

Atrial contraction accounts for most of the ventricular filling. True or False

False

Purkinje fibers are small fibers within the atria that conduct impulses rapidly. True or False

False

From which view is the connection between the pulmonary veins and the heart most visible? Anterior view Posterior view

Posterior view

The right side of the heart pumps blood through vessels to the lungs and back to the left side of the heart through the __________ circulation. pulmonary fetal coronary systemic

Pulmonary

The___________ atrium and ventricle are prominent when viewing the heart from the anterior view.

Right

The inferior chambers of the heart are called ________________.

Ventricles

What is the average RMP of resting nodal cells?

about -60 mV.

The atrial reflex is initiated when___________ in the atrial walls are stimulated by an increase in venous return.

baroreceptors

What is the sequence of events in the transmission of an impulse through the heart muscle? a: AV node b: AV bundle c: SA node d: Through the atria e: Through the ventricles f: Bundle branches g: Purkinje fibers

c, d, a, b, f, g, e

The time from the start of one heartbeat to the initiation of the next is called a(n)_____________ cycle.

cardiac

Nodal cells in the SA initiate a heartbeat by spontaneously___________ , to generate an action potential.

depolarizing