CARDIO: Heart (pt.3)

Cardiac muscle

it has features that support its great demand for energy, including an extensive blood supply, numerous mitochondria, and other structures such as myoglobin and creatine kinase (

Cardiac muscle

it relies almost exclusively on aerobic cellular respiration

fibrous skeleton

it provides structural support at the boundary between the atria and the ventricles

fibrous skeleton

it provides a rigid framework for the attachment of cardiac muscle tissue

coronary circulation

The diffusion of oxygen and nutrients at the needed rates through the thick wall of the heart is not possible; instead, an intricate distribution system called the

coronary arteries

The vessels that transport oxygenated blood to the wall of the heart are called

coronary veins

they transport deoxygenated blood away from the heart wall.

Right and left coronary arteries

they are positioned within the coronary sulcus of the heart to supply the heart wall

right marginal artery

The right coronary artery typically branches into the ____ to supply the lateral wall of the right ventricle

circumflex artery

The left coronary artery typically branches into the ___ to supply the lateral wall of the left ventricle

end artery

Body tissues are generally served by one artery called

functional end arteries.

the coronary arteries are more accurately called

great cardiac vein, middle cardiac vein, small cardiac vein

Transport of deoxygenated blood from the myocardium occurs through one of several cardiac veins. These include:

coronary sinus

These cardiac veins all drain into the ___

coronary sinus

The ___ then returns this deoxygenated blood directly into the right atrium of the heart.

heart’s conduction system

Specialized cardiac muscle cells are found within the heart located internal to the endocardium; they are collectively called

1. SA node

2. AV node

3. AV bundle (bundle of His)

4. Purkinje fibers

The conduction system includes the following structures:

sinoatrial (SA) node

is located in the posterior wall of the right atrium, adjacent to the entrance of the superior vena cava.

sinoatrial (SA) node

The cells here initiate the heartbeat and are commonly referred to as the pacemaker of the heart.

atrioventricular (AV) node

is located in the floor of the right atrium between the right AV valve and the opening for the coronary sinus.

atrioventricular bundle (bundle of His)

it extends from the AV node into and through the interventricular septum. It divides into left and right bundles.

Purkinje fibers

it extend from the left and right bundles beginning at the apex of the heart and then continue through the walls of the ventricles.

autonomic nervous system (specifically by the cardiac center within the medulla oblongata)

While the heartbeat is initiated by the SA node, both the heart rate and the strength of con- traction are regulated by __

Parasympathetic innervation

it comes from the cardioinhibitory center via the right and left vagus nerves

Sympathetic innervation

it arises from the cardioacceleratory center.

Conduction system.

Electrical activity is initiated at the SA node, and an action potential is then transmitted through the conduction system.

Cardiac muscle cells.

he action potential spreads across the sarcolemma of the cardiac muscle cells, causing sarcomeres within cardiac muscle cells to contract.

atria ; ventricles

These events occur twice in cardiac muscle cells during a heartbeat, first in the cells of the ___ and then in the cells of the ___.

Nodal cells in the SA node

are the pacemaker cells that initiate a heart- beat by spontaneously depolarizing to generate an action potential.

resting membrane potential (RMP)

This electrical charge difference when the nodal cell is at rest is called the

K* leak channels, Na* leak channels, and Na*/K* pumps

An RMP is established and maintained by __

Na*/K* pumps

The primary function of the ____ is to maintain the concentration gradients for Na+and K+

autorhythmicity (or automaticity)

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

threshold value

The Na* flows into the nodal cells, changing the resting membrane potential from —60 mV to —40 mV, which is the ___

1. Action potential is distributed throughout both atria and is relayed to the AV node.

2. The action potential is delayed at the AV node.

3. The action potential travels from the AV node through the AV bundle to Purkinje fibers.

4. The action potential spreads throughout both ventricles via gap junctions.

Cardiac muscle stimulation requires that the action potential initiated by the SA node be spread through the conduction system. The sequence of events occurs as follows

gap junctions

The action potential initiated in the SA node is spread between cardiac muscle cells in the atria by gap junctions____ that allow almost instantaneous excitation of all muscle cells in the atrial walls.

electrocardiogram

The electrical signals are collected and charted as ____

ECG

it provides a composite tracing of all cardiac action potentials generated by myocardial cells.

P wave

it reflects electrical changes of atrial depolarization that originates in the SA node.

QRS complex

it represents the electrical changes associated with ventricular depolarization.

T wave

is the electrical change associated with ventricular repolarization.

plateau

where there is essentially no electrical change

P-Q segment

it is associated with the atrial plateau at the sarcolemma when the cardiac muscle cells within the atria are contracting,

S-T segment

is the ventricular plateau when the cardiac muscle cells within the ventricles are contracting.

P-R interval

represents the period of time from the beginning of the P wave (atrial depolarization) to the beginning of the QRS deflection (ventricular depolarization).

P-R interval

It is the time required to transmit an action potential through the entire conduction system.

heart block

P-R intervals that extend longer than 0.20 second generally indicate an impaired conduction within the ventricles, often indicating a ___

Q-T interval

represents the time from the beginning of the QRS (ventricular depolarization) to the end of the T wave (ventricular repolarization).

Q-T interval

This is the time required for the action potential to occur within the ventricles.

tachyarrhythmia

Changes in the Q-T intervals may result in a fast, irregular heart rate, which is called

ECG

is a common diagnostic tool that is used in physical exams and after surgery to detect many changes to the heart, including abnormal heart rhythms

dysrhythmia

is any abnormality in the electrical activity of the heart.