A&P chap 12 - Heart terms

Pericardium

• Loosely fitting sac that separates the heart from surrounding tissue

• Allows space for the heart to expand and contract

fibrous pericardium

outer layer of pericardium

Parietal layer of serous pericardium

• Delicate membrane lining inner surface of fibrous pericardium

• Forms the visceral layer of serous pericardium at the base

epicardium

• Thin membrane that tightly adheres to surface of the heart

Pericardial cavity

• Space between the parietal layer and visceral layer of serous pericardium

• Filled with pericardial fluid, Reduces friction

Myocardium

• Thick layer of cardiac muscle tissue

• Provides force for contraction

Epicardium

• Outer layer

• Contains blood vessels that nourish the heart

Endocardium

• Inner layer of simple squamous epithelium

• Continuous with the inner lining of the blood vessels attached to heart

atria

Receive blood from veins

ventricles

Pump blood into arteries

Interatrial septum

• thin wall separating the heart's right and left atria

Interventricular septum

• thick wall separating the heart's left and right ventricles

Atrioventricular valves

• Allow flow from atria to ventricles.

  • Prevents backflow when ventricles contract

Tricuspid valve

• Between R atrium and R ventricle

Mitral valve

• Between L atrium and L ventricle

Semilunar valves

• Located at bases of large arteries that carry blood from ventricles

  • Allow blood to flow from ventricles into blood vessels when ventricles contract

  • Prevent backflow from blood vessels when ventricles relax

AV valve structure

• Originate from the fibrous skeleton of the heart

• Provides valve support

• Serves as electrical insulation between atria and ventricles

Semilunar valve structure

Three pocket-like cusps

Pulmonary circuit

• Deoxygenated blood flows from R ventricle to lungs.

• Oxygenated blood flows from lungs to L atrium.

Systemic Circuit

• Oxygenated blood flows L ventricle to body.

• Deoxygenated blood flows from body to R atrium.

coronary arteries

• Arise from the aorta just above the aortic valve

• Supply myocardium with oxygenated blood

Cardiac veins

• Lie next to coronary arteries

• Return deoxygenated blood to the coronary sinus, which drains into the R atrium

Cardiac cycle

• the sequence of events that occur during one heartbeat

Systole

• Contraction phase

• Increases blood pressure within a chamber

Diastole

• Relaxation phase

• Decreases blood pressure within a chamber

• When ventricles contract, atria relax.

• When atria contract, ventricles relax.

Lub

• heart sound

• closing of AV valves at the start of ventricular systole

dup

• heart sound

• closing of semilunar valves at the start of ventricular diastole

SA node

• Located in right atrium near the SVC junction

• Pacemaker of the heart

• 60–100 beats per minute

• Rhythmically forms action potentials to initiate each heartbeat. Action potentials cause simultaneous contraction of atria.

AV Node

• In right atrium near lower portion of interventricular septum

  • Receives action potentials from S A node

  • secondary pacemaker (40-60 bpm)

AV bundle

• Divides into left and right bundle branches

• Carry action potentials down ventricular septum and up lateral ventricle walls

• Forms the subendocardial conducting network

Purkinje fibers

• Carry action potentials to myocardium of ventricles

• Contraction occurs from the apex upward

• last resort pacemaker, (20-40) beats per minute.

P wave

Atrial depolarization

QRS complex

Ventricular depolarization

T wave

Ventricular repolarization

Electrocardiogram

• Recording of the electrical current generated by the conducting system of the heart

• Performed using an electrocardiograph

Cardiac output

• the volume of blood pumped from each ventricle per minute.

  • Determined by, stoke volume and heart rate

  • CO = SV × HR

Stroke volume

• volume of blood pumped out of each ventricle per heartbeat.

Heart rate

• number of heartbeats per minute.

venous return

the rate of blood flow back to the heart's right atrium

medulla oblongata

• Cardiac control center

  • Also affected by emotions created by the limbic system.

Baroreceptors

• in the aortic arch and carotid sinuses.

• Stimulated by changes in vessel wall stretching due to blood pressure changes.

Chemoreceptors

• in aortic arch and carotid bodies.

• Stimulated by low blood pH, high blood CO2, very low blood O2.

Sympathetic neurons

• Axons exit thoracic region of spinal cord to innervate S A node (also A V node and parts of myocardium).

• Secrete norepinephrine

• Increases heart rate, Strengthens force of myocardial contraction

Parasympathetic neurons

• Axons exit in the vagus nerve (C N X) to innervate the S A and A V nodes.

• Secretes acetylcholine, Slows heart rate

Blood Vessels

• closed system of tubes carrying blood from the heart to tissue cells and back to the heart.

  • Arteries, Capillaries, Veins

Tunica externa

• Outermost layer

• Dense irregular connective tissue

• Provides support and elasticity

Tunica media

• Middle layer

• Smooth muscle fibers

• Supports the vessel

• Causes changes in blood vessel diameter

Tunica intima

• Deepest layer

• Internal lining of a blood vessel.

• Consists of endothelium supported by areolar connective tissue

capillary

• transfer oxygenated blood from arteries to veins

• Most numerous and smallest vessels

  • Walls contain only tunica intima.

Precapillary sphincters

• regulate blood flow into capillaries.

Sphincter contraction inhibits blood flow.

Sphincter relaxation allows blood flow.

Osmotic pressure

Due to plasma proteins in blood

Promotes reabsorption

“Pulls” fluid from interstitial fluid into blood by osmosis

Blood pressure

Promotes filtration

“Pushes” fluid out of blood capillaries and into interstitial fluid

 Venules

unite to form larger veins, which in turn unite to form even larger veins.

vein

Reducing venous volume can compensate for blood loss or increase in muscle activity:

Sympathetic part sends action potentials that trigger contraction of venous smooth muscle.

Reduces venous volume

Increases blood volume and pressure in heart, arteries, and capillaries

Blood pressure

The force of blood against the wall of blood vessels

Usually refers to arterial blood pressure in the systemic circuit

Systolic blood pressure:

Highest pressure during ventricular systole

Diastolic blood pressure

Lowest pressure during ventricular diastole

Pulse pressure

the difference between systolic and diastolic blood pressures.

Causes the pulse

Expansion and contraction of arterial walls

vasoconstriction

• An increase in the frequency of sympathetic action potentials

• Increases resistance.

  • Increases blood pressure and blood velocity.

  • Accelerates O2 and CO2 transport rates.

vasodilation

• A decrease in the frequency of sympathetic action potentials

• Decreases resistance

• Decreases blood pressure and velocity