Muscle Physiology: Smooth & Cardiac Muscle

These flashcards cover key concepts related to smooth and cardiac muscle physiology as discussed in the lecture.

Cardiac Muscle

Muscle found in the heart, controlled autonomously, with striated appearance.

Smooth Muscle

Muscle found in internal organs, controlled autonomously, lacks striations.

Skeletal Muscle

Striated muscle attached to the skeleton, under voluntary control.

T-tubule

Transverse tubules that transmit the action potential into the muscle fiber.

Sarcoplasmic Reticulum (SR)

Organelle that stores calcium ions in muscle cells.

Gap Junctions

Specialized intercellular connections that allow for electrical communication between cardiac cells.

EC Coupling in Cardiac Muscle

The process by which an action potential triggers calcium release from the sarcoplasmic reticulum.

RyR Receptors

Ryanodine receptors that release calcium from the sarcoplasmic reticulum during cardiac excitation-contraction coupling.

Calmodulin

A calcium-binding protein that activates myosin in smooth muscle contraction.

Latch State

A state in smooth muscle where the muscle can maintain contraction with low ATP consumption.

Myocardial Cell

A heart muscle cell that can vary twitch tension by altering intracellular calcium concentration.

No Sarcomeres in Smooth Muscle

Smooth muscle lacks sarcomeres, allowing for greater contraction distances.

Calcium's Role in Muscle Contraction

Calcium ions trigger contractions by activating proteins like troponin in skeletal muscle and calmodulin in smooth muscle.

What is the mechanism of action for cardiac muscle contraction?

Cardiac muscle contraction is initiated by an action potential that leads to the opening of voltage-gated calcium channels, causing calcium influx and subsequent release of more calcium from the sarcoplasmic reticulum via RyR receptors.

How does calcium influence smooth muscle contraction?

Calcium ions bind to calmodulin, which activates myosin light chain kinase (MLCK). This activation causes phosphorylation of myosin, enabling cross-bridge cycling and contraction.

What is the role of T-tubules in muscle contraction?

T-tubules facilitate the rapid transmission of action potentials into the muscle fiber, ensuring that calcium is released from the sarcoplasmic reticulum in a coordinated manner.

What is the significance of gap junctions in cardiac muscle?

Gap junctions allow for the rapid electrical communication between myocardial cells, enabling synchronized contractions necessary for effective pumping of the heart.

Describe the latch state mechanism in smooth muscle.

The latch state mechanism allows smooth muscle to maintain contraction with minimal energy expenditure by reducing the activity of myosin light chain phosphatase (MLCP), resulting in prolonged contraction without increased ATP consumption.