A&PII Ch. 20-The Heart

Depolarization

A change in the trans-membrane potential from a negative value toward 0mV.

Electrocardiogram (EKG, ECG)

A graphic record of the electrical activities of the heart, as monitored at specific locations on the body surface.

Systole

A period of contraction in a chamber of the heart, as part of the cardiac cycle.

Action Potential

A propagated change in the trans-membrane potential of excitable cells, initiated by a change in the membrane permeability to sodium ions;

Epicardium (visceral pericardium)

A serous membrane covering the outer surface of the heart;

Isovolumetric contraction

All the heart valves are closed, the volumes of the ventricles to not change, and ventricular pressures are rising;

Foramen Ovale

An oval opening the penetrates the interatrial septum and connects the two atria of the fetal heart;

Relative refractory period

Begins when sodium channels regain their normal resting condition, and continues until the transmembrane potential stabilizes at resting levels.

Higher, lower

Blood flows through the heart from an area of ______ pressure to an area of ______ pressure.

Nerve network at the base of the heart.

Cardiac plexus

*Sympathetic *Norepinephrine(NE) *Sodium and Calcium *Speed up

Cardioacceleratory Center of the medulla oblongata is associated with the _____ division of the nervous system, which release _____, a neurotransmitter, at the SA node which opens both the channels and the _____ channels, causing the heart to _____.

*Parasympathetic *Acetylcholine *Potassium *Slow down

Cardioinhibitory Center of the medulla oblongata is associated with the _____ division of the nervous system, which releases _____, a neurotransmitter, at the SA node which opens the ___channels causing the heart to _____.

Pacemaker cells

Cells in the SA node, which establish the heart rate.

SA node activity and atrial activation begin----->Stimulus spreads across the atrial surfaces and reaches the AV node----->There is a 100-msec delay at the AV node. Atrial contractions begin----->The impulse travels along the interventricular septum within the AV bundle and the bundle branches to the Purkinje fibers and, via the moderator band, to the papillary muscles of the right ventricle----->The impulse is distributed by Purkinje fibers and relayed throughout the ventricular myocardium. Atrial contraction is completed, and ventricular contraction begins.

Create a flowchart that maps out the conduction of the heart.

Autonomic innervation. Cardiac centers in the medulla oblongata. Effects on the SA node. Atrial reflex.

Factors affecting heart rate.

Parietal pericardium

Lines the inner surface of the tough pericardial sac surrounding the heart;

Step 1: Rapid Depolarization; At threshold, voltage-gated sodium channels open and a massive influx of sodium ions rapidly depolarize; at +30 mV, the voltage-gated sodium channels close. Step 2: The Plateau: trans-membrane potential drops to -60mV and the cells begin to pump sodium out of cell. Voltage-gated calcium channels are open, calcium ions enter sarcoplasm. Step 3: Repolarization: calcium channels begin closing, and potassium channels begin opening. Potassium ions rush out of cell, and net result is a period of rapid repolarization that restores the resting potential.

List the basic steps of the action potential going through a contractile cell especially focusing on the influx of ions across the membrane.

Myocardium

Muscular wall of the heart that forms the atria and ventricles.

Cardiac Cycle

One complete heartbeat, including atrial and ventricular systole and diastole.

Contractile cells

Produce the powerful contraction that propel blood.

Diastole

Relaxation; the chamber fills with blood and prepares for the next cardiac cycle.

1.) Atrial systole a.) Atria contract, AV valves open, semilunar valves closed. 2.) Ventricular systole a.) Atria relax, ventricles contract, AV valves forced closed, semilunar valves still closed. b.) Atria relax, ventricles contract, AV valves remain closed, semilunar valves forced open. 3.) Ventricular diastole a.)Atria and ventricles relax, AV valves and semilunar valves closed, atria begin passively filling with blood. b.) Atria and ventricles relax, atria passively fill with blood as AV valves open, semilunar valves closed.

Steps in the cardiac cycle

Pericardial Sac

Surrounds the heart; stabilizes the position of the heart and associated vessels within the mediastinum.

Atrial reflex, venous return

The _____ involves adjustments in heart rate in response to an increase in the _____.

Cardiac output

The amount of blood ejected by the left ventricle each minute; normally about 5 liters.

Stroke volume

The amount of blood pumped out of each ventricle during a single beat;

End Systolic Volume

The amount of blood remaining in the ventricle when the semilunar valve closes.

Repolarization

The movement of the transmembrane potential away from the positive value and toward the resting potential.

Sinoatrial Node (SA)

The natural pacemaker of the heart; stimulated in the wall of the right atrium.

Mediastinum

The region between the two pleural cavities; The heart sits in the anterior portion.

Automaticity

The spontaneous depolarization to threshold, characteristic of cardiac pacemaker cells.

Summation

The temporal or spatial addition of contractile force or neural stimuli.

Ventricular ejection

Ventricles contract isotonically: Muscle cells shorten, and tension production remains relatively constant.

Isovolumetric Relaxation

Ventricular pressures are higher than atrial pressures, blood cannot flow into the ventricles.

rhythmically and spontaneously generate action potentials that spread to other type of cardiac muscle cell

What allows pacemaker cells of the heart to spontaneously depolarize?

Pericarditis

When pathogens infect the pericardium, producing inflammation.

Absolute Refractory Period

during this period, the membrane cannot respond to further stimulation.

Intercalated discs

interlocking membranes of adjacent cells are held together by desmosomes and linked by gap junctions; transfer the force of contraction from cell to cell and propagate action potentials.

Venous return

the amount of blood returning to the heart through veins.

End Diastolic Volume

the quantity each ventricle contains in the cardiac cycle of the heart. In an adult who is standing at rest, the volume is typically about mL.