A&P 2 Exam 3: The Heart & Circulatory System

Nodal cells

heart cells responsible for setting the rate of cardiac contraction

Intercalated discs

connect cardiac muscle fibers mechanically and electrically

Internodal pathways

link the SA node to the AV node for conduction of the stimulus

Conducting fibers

distribute stimulus from AV node to myocardium of the ventricles

Atrioventricular (AV) Bundle

Bundle of specialized fibers that conduct impulses from the AV node to the right and left ventricles; also called bundle of His.

Purkinje fibers

specialized conducting cardiac muscle cells in the ventricles of the heart

Sequence of events of Conduction System

1- SA node generates action potential. Impulse spreads throughout the atria causing then both to contract while the internodal pathway carries impulse to AV node

2- AV node receives impulse from SA node. AV node generates an AP that travels down the AV Bundle and bundle branches, to the Purkinje fibers, causing the ventricles to contract in a wave from the inferior apex upward to the base to force blood out of the heart

Electrocardiogram (ECG or EKG)

recording of electrical changes that occur during each cardiac cycle

Arrhythmias

abnormal heart patterns

Sinus rhythm

normal heart rate

P wave

atrial depolarization

QRS Complex

ventricular depolarization and atrial repolarization

AP in Cardiac Muscle

1- Rapid depolarization-- Purkinje fibers electrically stimulate voltage-regulated sodium channels to open and extracellular Na+ flows into contractile cell and causes rapid depolarization

2- The Plateau-- At +30 mV, the fast sodium channels close and slow voltage-regulated calcium channels open. Extracellular Ca++ enters heart cell and maintains the transmembrane potential above 0 mV. Prolongs AP in the heart cell

3- Repolarization-- when the slow voltage-regulated calcium channels begin to close, slow voltage-regulated potassium channels open and the membrane repolarizes and slowly returns to the resting potential

CAD

coronary artery disease

Coronary ischemia

reduced circulatory supply from partial or complete blockage of coronary arteries

Angina pectoris

chest pain that results when the heart does not get enough oxygen

Angiography

a medical imaging technique used to visualize the inside, or lumen, of blood vessels and organs of the body, with particular interest in the arteries, veins, and the heart chambers.

MI

myocardial infarction (heart attack)

Coronary thrombosis

damage to the heart muscle caused by a thrombus blocking a coronary artery

Atherectomy

minimally invasive endovascular surgery technique for removing atherosclerosis from blood vessels within the body

Balloon angioplasty

a procedure in which a balloon attached to the end of a catheter is used to clear blockages in blood vessels

CABG

Coronary Artery Bypass Graft, "Open heart surgery"

Cardiac cycle

one complete heartbeat, including atrial and ventricular systole and diastole

Systole

Contraction of the heart

Diastole

Relaxation of the heart

Regurgitation

backflow of blood into an atrium

due to dysfunction of an AV valve

Mitral valve prolapse

improper closure of the mitral valve

Isovolumetric contraction

refers to the short period during ventricular systole when the ventricles are completely closed chambers

Ventricular ejection

Phase of the cardiac cycle in which the semilunar valves open, blood spurts from each ventricle and the T Wave occurs

Dicrotic notch

brief rise in aortic pressure caused by backflow of blood rebounding off semilunar valves

Isovolumetric relaxation

period where all four heart valves are closed, and the ventricular myocardium is relaxed

Auscultation

listening to sounds within the body

Lubb-Dupp

The two separate heart sounds that can be heard with the use of a stethoscope.

Heart murmurs

sounds created by regurgitation and unusual chamber circulation of blood

Cardiac Output (CO)

Volume of blood pumped by heart per minute.

Heart Rate (HR)

The number of heartbeats during a specific time (usually 1 minute).

Stroke Volume (SV)

The amount of blood pumped out of the heart with each contraction.

Sympathetic nerves

involved in "fight or flight" responses (excitement, exercise, stress and survival situations)

NT = norepinephrine (increases the heart rate and force of contraction

Parasympathetic nerves

involved in "rest and digest" responses, a return to normal homeostasis

NT = acetylcholine (decreases heart rate and force of contraction)

Bainbridge (Atrial) reflex

adjusts heart rate in response to an increase in venous return of blood to the heart

What hormones influence heart rate?

epinephrine, norepinephrine, and thyroid hormone

Positive chronotropic

increase heart rate

Negative chronotropic

decrease heart rate

End-Diastolic Volume (EDV)

volume of blood in each ventricle at end of ventricular diastole

End-Systolic Volume (ESV)

Amount of blood remaining in each ventricle at the end of systole (contraction).

EDV determined by two factors

1- Filling time: length of ventricular diastole

2- Venous return: rate at which blood returns to the heart and fills the ventricles

Preload

the stretching of the ventricle by the blood

Frank-Starling principle

increasing EDV results in a corresponding increase in the stroke volume

Contractility

force produced during contraction

Positive inotropic factor

Any factor that results in an increased contractility

Negative inotropic factor

any factor that decreases contractility

Afterload

force necessary to open semilunar valve and eject blood

Blood flow

the amount (volume) of blood that passes through a vessel

Pressure

the force exerted by fluids against surfaces; key for blood circulation

Circulatory Pressure (CP)

difference in pressure across the entire systemic circuit, for circulation to occur this must overcome the total peripheral resistance.

Blood Pressure (BP or P)

Force exerted onto a given area of the vessel wall by the blood contained within it, measured in mm Hg

Pulse Pressure

the difference between systolic and diastolic blood pressure

Resistance (R)

the force that opposes movement

Total Peripheral Resistance

the resistance of the entire cardiovascular system

Vascular Resistance

depends on vessel diameter and vessel length

Arterial blood pressure

the pressure of circulating blood on arterial walls, measured as systolic over diastolic pressure

Systolic P

the peak arterial pressure measured during ventricular systole

Diastolic P

pressure measured in the walls of a muscular artery when the left ventricle is in diastole

Pulse P

rhythmic fluctuation in pressure that accompanies each heartbeat

Mean arterial P (MAP)

used to report a single blood pressure

Hypertension

abnormally high blood pressure

Hypotension

abnormally low blood pressure

Filtration

the movement of a fluid across a membrane whose pores restrict the passage of solutes based on size

Reabsorption

process by which water and dissolved substances are taken back into the blood

Capillary Hydrostatic pressure (CHP)

the pressure of blood within capillary walls

Osmotic pressure (BCOP)

the pressure that must be applied to prevent osmotic movement across a membrane

Net Filtration Pressure (NFP)

the difference between the net hydrostatic pressure and the net osmotic pressure

Dynamic center of a capillary

the point where the osmotic pressure equals the hydrostatic pressure, and no net fluid is exchanged through the capillary wall

Autoregulation

local control of blood flow

Neural Mechanisms

the medulla of the brain has sympathetic vasomotor centers to control vascular resistance

Baroreceptor reflexes

in the carotid sinues and aortic sinuses, they monitor pressure by detecting stretching of the vessel wall

Chemoreceptor reflexes

in carotid bodies and aortic bodies, they respond to changes in CO2, O2, or pH in the blood

Endocrine Mechanisms

hormones provide long-term control of vessel physiology

ADH

increases blood pressure by maintaining blood volume

Pulmonary circuit

carries oxygen-poor blood from the heart's lower right chamber, through the pulmonary arteries, to the lungs, and oxygen-rich blood back through the pulmonary veins to the heart's upper left chamber

Systemic circuit

carries oxygen-rich blood from the heart's lower left chamber, through the systemic arteries, and oxygen-poor blood through systemic veins back to the heart's upper right chamber

Where does the right atrium receive blood from and where does it pass blood to?

Receives blood from the systemic circuit and passes it to the right ventricle

Where does the left atrium receive blood from and where does it pass blood to?

Receives blood from the pulmonary circuit and passes it to the left ventricle

Cardiac skeleton

a crisscrossing, interlacing layer of dense connective tissue that anchors muscle fibers, supports the great vessels and heart valves, and limits the spread of action potentials

Pericardium

the fibrous sac that surrounds the heart; its inner, serous lining is continuous with the epicardium

Fibrous pericardium

outer layer of the pericardium; contains a dense network of collagen fibers that stabilize the position of the heart and associated vessels within the mediastinum

Serous pericardium

two-layered membrane composed of an outer parietal layer and an inner visceral layer

Pericardial membranes

acts as a lubricant, reducing friction between the opposing visceral and parietal surfaces as the heart beats

Cardiac tamponade

a compression of the heart due to fluid accumulation in the pericardial cavity

Auricle

expandable extension of an atrium

Coronary sulcus

deep groove that marks the border between the atria and the ventricles

Visceral layer of serous pericardium

covers the surface of the heart; consists of an exposed mesothelium and an underlying layer of areolar connective tissue that is attached to the myocardium

Parietal layer of serous pericardium

consists of an outer dense fibrous layer, an areolar layer, and an inner mesothelium

Myocardium

the cardiac muscle tissue of the heart that contains cardiac muscle cells, connective tissue, blood vessels, and nerves

Endocardium

the simple squamous epithelium that lines the heart and is continuous with the endothelium of the great vessels

Struts

fibrous cross-links that tie together adjacent cells

Function of connective tissue fibers

1- provide physical support for the cardiac muscle fibers, blood vessels, and nerves of the myocardium

2- help distribute the forces of contraction

3- add strength and prevent overexpansion of the heart

4- provide elasticity that helps return the heart to its original size and shape after a contraction

Aorta

the large, elastic artery that carries blood away from the left ventricle and into the systemic circuit

Septa

muscular partitions that separate the chambers of the heart

Valves

covered openings that direct the flow of blood between chambers and vessels