Cardiac Muscle, L32, Flashcards

Flashcards to review key concepts of cardiac muscle physiology.

Cardiac muscle is and all the cells are electrically connected.

striated

Unlike skeletal muscle, the force of contraction in cardiac muscle cannot be modulated by .

recruitment

Atrial cells are joined to each other by that allow electric activity to spread from one cell to the next.

gap junctions

Ventricular cells have a well-developed which carries excitation into the interior of the cell.

t-tubular system

Cardiac muscle tissue is primarily and consequently deep red in colour.

oxidative

In cardiac muscle ventricle cells, t-tubules occur at the level of the and the SR is less well developed.

z-disks

Cardiac muscle is – it initiates contractions without nervous input.

myogenic

Action potentials in the heart are initiated in the .

sino-atrial node

The cardiac action potential is much than that of nerve and skeletal muscle.

longer

The presence of a large sustained inward ICa (calcium current) produces a significant into the cell.

calcium influx

Calcium-induced calcium release (CICR) is triggered by .

calcium influx

A large calcium influx is balanced by a large calcium extrusion capacity via a mechanism.

Na+/Ca2+ exchange

During cardiac action potential repolarization, the membrane is highly during most of the twitch, re-excitation is unlikely.

depolarized

It is not normally possible to cardiac muscle.

tetanize

A notable difference between cardiac and skeletal muscle is that the troponin in cardiac muscle has only calcium specific site.

one

As the cardiac action potential starts to repolarise, calcium is pumped back into the SR by a .

Ca-ATPase

The influx of Ca++ through in the sarcolemma and T tubules is required for excitation-contraction coupling in the heart.

L-type calcium channels

Increasing the rate of contraction in cardiac muscle is normally determined by the action potential rate in the cells.

pacemakers

Unlike skeletal muscle, all cardiac muscle fibres are .

activated

The force of contraction in cardiac muscle can be modulated by a change in the amplitude of the .

calcium transient

Law of the Heart states that as resting ventricular volume is increased the force of contraction of the ventricle is increased.

Starling's

The sympathetic neurotransmitter has several effects on the heart via the second messenger cAMP and protein kinase A.

noradrenaline

is a neurotransmitter released by the parasympathetic nervous system that slows the rate of discharge of SA cells.

Acetylcholine (ACh)

Cardiac muscle cells are coupled, unlike skeletal muscle cells which are electrically isolated.

electrically

In cardiac muscle calcium influx is induced but in skeletal muscle it is Na+ induced.

Ca2+

is set by the pacemaker cells in the sinoatrial node.

Heart Rate (HR)

is increased by certain neurotransmitters such as Noradrenaline.

Stroke volume (SV)

The ‘pacemaker potential’ is due to current, mostly Na+ driven.

If

Noradrenaline (NE = NA) acting on β receptors cause calcium to enter the cell.

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