APHY102 - marieb - Chapter 18 - The Heart Flashcards

Terms Definitions
Describe the location of the heart,
Superior surface of diaphragm, left of midline, anterior to the vertebral column, posterior to sternum
What's the pulmonary circuit?
It's a short loop that oxygenates blood. Consists of left and right pulmonary artery, left and right pulmonary vein, and capillary bed of left and right lung.
What's the systemic circuit?
It's a long loop that carries blood to and from body tissues.
What two valves lie between the atria and the ventricles, maintaining unidirectional blood flow?
The "Atrioventricular valves," also known as the bicuspid valve (left side) and tricuspid valve (right side)
What valves prevent backflow into the atria when ventricles contract?
The atrioventricular valves (bicuspid on the left and tricuspid on the right)
What tendons anchor the AV valves to papillary muscles?
Chordae tendinae (singular chorda tendinea)
Blood flows into the right ventricle through which valve?
Tricuspid valve
What is the tricuspid valve made up of?
Three cusps composed of dense connective tissue (CT) covered by endocardium
What is the bicuspid valve composed of?
Two cusps composed of dense CT, anchored to the papillary muscles by the chordae tendineae
Which valves prevent backflow of blood into the ventricles?
Semilunar valves. The aortic semilunar valves prevent backflow from the aorta to the left ventricle, and the pulmonary semilunar valves prevent backflow from the pulmonary trunk into the right ventricle.
What arteries leaving the heart provide arterial blood supply?
right and left coronary (in atrioventricular groove), marginal, circumflex, anterior and posterior interventricular arteries.
What vessels return blood to the heart?
Superior and inferior vena cavae, right and left pulmonary veins, small cardiac, anterior, and great cardiac veins (into the coronary sinus -- these three constitute the "venous return."
What is angina pectoris?
The medical term for chest pain due to coronary heart disease.
Of what condition is angina a symptom?
myocardial ischemia
When does angina pectoris occur?
When the heart muscle (myocardium) doesn't receive enough blood, thus enough oxygen. It occurs when one or more of the heart's arteries is narrowed or blocked.
What's insufficient blood supply called?
What's ischemia?
Insufficient blood supply
What's the medical term for a heart attack?
Myocardial infarction (MI). Also "Acute myocardial infarction" or AMI.
What are the symptoms of a myocardial infarction?
chest pain or discomfort, weakness, sweating, nausea, vomiting, and arrhythmias sometimes resulting in loss of consciousness
Describe cardiac muscle fibers.
Striated, short, quadrangular-shaped, branching fibers with a single centrally located nucleus. Cells are connected with intercalated discs with gap junctions.
Cardiac muscle has a much greater concentration of ____ than skeletal muscle.
Mitochondria --- reflecting the heart's dependence on cellular respiration for ATP.
What are the two types of cardiac muscle cells?
99% are contractile cardiac muscle cells (mitochondrial). The rest are autorhythmic cells of the heart, which lack the elaborate sarcomeres and other contractile machinery.
Describe autorhythmic cells.
Self excitable, able to initiate their own depolarization (action potentials), they have unstable resting potentials called pacemaker potentials.
What two ions are required for cardiac contraction to occur?
Sodium and calcium
What ions initiate the action potential in cardiac muscle?
Which ions cause depolarization for a greater duration after the action potential is initiated?
Calcium ions
What protein do calcium ions bind to, allowing myosin and actin to associate through cross-bridge formation?
Where is the sinoatrial (SA) node located?
Adjacent to the SVC opening in the right atrium --- and it generates impulses about 75 times per minute
How frequently does the sinoatrial node generate impulses?
75 times per minute, and it's located right next to the SVC (superior vena cava) opening in the right atrium.
Where is the atrioventricular node and what does it do?
It's located near the right atrioventricular (AV) valve at the bottom of the interatrial septum, it delays the impulses about 0.1 second.
What bundle of modified heart muscle carries impulses from the atrioventricular node to the ventricles, causing them to contract?
The atrioventricular bundle (Bundle of his)
What's the atrioventricular bundle?
A bundle of modified cardiac muscle that carries impulses from the atrioventricular node to the ventricles, causing them to contract.
Where does the atrioventricular bundle split into two pathways?
In the interventricular septum
What's another word for the atrioventricular bundle?
Bundle of His
What's another name for the Bundle of His?
Atrioventricular bundle
Where are impulses directed from the AV bundle branches at the interventricular septum?
Towards the apex of the heart
What fibers throughout the ventricles carry impulses to the heart apex and ventricular walls?
Purkinje fibers
What do Purkinje fibers do?
Carry impulses to the heart apex and ventricular walls.
What "center" stimulates the heart?
The sympathetic cardioacceleratory center
What "center" inhibits the heart?
The parasympathetic cardioinhibitory center
What branch of the autonomic nervous system inhibits the heart?
The parasympathetic
What branch of the autonomic nervous system stimulates the heart?
Parasympathetic fibers inhibiting the heart travel down which cranial nerve?
Vagus nerve
What device can measure electrical activity created by the heart?
electrocardiogram (ECG or EKG) machine
Which wave measured by an ECG machine corresponds to depolarization of the SA node?
P wave
What does the P wave as measured by an ECG machine correspond to?
Depolarization of the SA node
The QRS complex of an EKG signifies what?
ventricular depolarization
The T wave of an EKG corresponds to what?
ventricular repolarization
What portion of an EKG masks atrial repolarization?
QRS complex
Where can you see atrial repolarization on an EKG?
Nowhere -- it's masked by the QRS complex
What are the scientific terms for repetitive contraction and relaxation of the heart?
Contraction = systole
Relaxation = diastole
What happens during diastole?
The heart relaxes and blood fills the atria, then begins to fill the ventricles
What stage of the cardiac cycle is characterized by relaxation of the heart and filling of the atria and ventricles?
What happens during systole?
First, both atria contract almost simultaneously, filling the ventricles with blood.

Then the ventricles contract several tenths of a second later and pump blood out to the body.
What event is the cause for the first heart sound (S1)?
Closure of the atrioventricular valves as ventricular systole begins.
What is the cause for the second heart sound (S2)?
Closure of the aortic and pulmonary semilunar valves at the beginning of ventricular diastole.
Occasionally you hear a third heart sound. What causes it?
Turbulent bloodflow into the the ventricles during the first third of diastole
Define cardiac output (CO)
The amount of blood pumped by each ventricle in one minute.
CO is the product of what other two measurements?
Stroke volume (SV) and heart rate (HR)
What is stroke volume?
The amount of blood the heart pumps with each beat
What is cardiac reserve?
The difference between resting and maximal CO
What term is defined as "the difference between resting and maximal CO?"
Cardiac reserve
What term is defined as "the amount of blood the heart pumps with each beat?"
Stroke volume
What is preload?
Preload is the stretched condition of the heart after diastole
What factors increase stroke volume?
exercise, slow heartbeat
What factors decrease stroke volume?
extremely high HR, blood loss
Define contractility as it relates to cardiac muscle
Contractile force due to factors other than end diastolic volume
What factors can increase contractility?
Increased sympathetic stimuli, certain hormones, CA2+ and some drugs
Define "afterload."
Back pressure exerted by blood leaving the large arteries leaving the heart
Which hormones increase heart rate?
epiniphrene and thyroxine
Define "tachycardia"
HR above 100 BPM
Define "bradycardia"
HR below 60 BPM
What's the average resting heart rate?
70 BPM for males, 75 for women
What term describes an HR above 100 BPM?
What term describes an HR below 60 BPM?
What causes congestive heart failues (CHF)?
1) Coronary atherosclerosis
2) Persistent high blood pressure
3) Multiple myocardial infarcts
4) Dilated myocardiopathy (DCM)
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