Chapter 17- Section 3

three components to the purkinje fiber system

AV bundle, the right and left bundle branches, and the terminal branches of the perkinje fibers.

if the SA node ceases to function, the _____ node can successfully pace the heart, albeit somewhat slowly.

AV node

A group of atypical (bc their action potentials rely on different ion channels. and they function in a slightly different way.) pacemaker cells located in the ventricles.

Purkinje fiber system

cardiac muscle cells contract in response to electrical excitation in the form of

action potentials.

The _____ bundle penetrates the heart's fibrous skeleton in the inferior interatrial septum and the superior interventricular septum.

artrioventricular (AV) bundle

A cluster of pacemaker cells in the inferior right atrium that delays the propagation of the cardiac action potential from the atria to the ventricles

atrioventricular node

cardiac muscle has the property of ________- it sets its own rhythm without a need for input from the nervous system.

autorhythmicity

the right and left __________ course along the right and left sides of the interventricular septum. and propagate action potentials

bundle branches

three populations of pacemaker cells in the heart: the sinoatrial node, the atrioventricular node, and the Purkinje fiber system

cardiac conduction system

an ECG is recorded by placing electrodes on the surface of a patients skin: six on the ______ and two on each _____.

chest; extremity

An ECG only shows electrical changes that occur in _____ cells

contractile

the pacemaker cells in cardiac muscle tissues rhythmically and spontaneously generate action potentials that trigger the other type of cardiac muscle cell, known as _______ cells, to also have action potentials.

contractile cells.

demonstrate voltage-gated opening but time-gated closing, meaning that they close after a certain period regardless of voltage. these are present in all cardiac muscle cells.

demonstrate voltage-gated opening but time-gated closing, meaning that they close after a certain period regardless of voltage

a graphic depiction of the electrical activity occuring in all cardiac muscle cell over a period of time

electrocardiogram (ECG)

the cells of the heart are sometimes referred to as a

functional syncytium

Gap junctions in these discs allow the electrical activity generated by the pacemaker cells to rapidly spread to all cardiac muscle cells via electrical synapses. This permits the heart to contract as a unit and produce a coordinated _____

heart beat

cardiac muscle cells contain abundant _____, a protein that carries oxygen, and nearly half of their cytoplasmic volume is composed of _____. Both of these facts reflect their high energy demands.

myoglobin, mitochondria

unique to certain pacemaker cells is a type of _______ known as ______. This voltage gated channel is unusual in that it is activated by hyperpolarization. When opened it allows sodium ions to enter the cell while potassium ions simultaneously exit.

nonselective cation channels; HCN channel

the cardiac muscle cells do not require stimulation from the nervous system to generate action potentials because their electrical activity is coordinated by a very small, unique population of modified cardiac muscle cells called ________ cells.

pacemaker cells.

an action potential spontaneously generated by a pacemaker cell in cardiac or smooth muscle.

pacemaker potential

Some are voltage gated and some are ligand-gated

potassium ion channels

A cluster of pacemaker cells in the superior right atrium that normally sets the pace for the heart

sinoatrial node

The SA node is the normal pacemaker of the entire heart; electtrical rhythms generated and maintained by the SA node are known as _______

sinus rhythms

penetrate ventricles and finally come into contact with the contractile cardiac muscle cells.

terminal branches.

Open in response to voltage changes but not found in certain pacemaker cells

voltage-gated sodium ion channels