PHYSL 212 Lecture 9: Cardiac and Smooth Muscle (Terms)

Cardiac Myoctes

Branched muscle cells found in cardiac muscle

Intercalated Disks

Specialized cell junctions that longitudinally connect cardiac myoctes to form cardiac muscle

L-Type Ca²⁺ Channel

Voltage gated calcium channels found on the cardiac myocyte membrane that act as a channel for extracellular calcium to enter the myocyte

Calcium-Induced Calcium Release (CICR)

The excitation-contraction coupling mechanism in cardiac muscle, where the binding of calcium causes more calcium to be released, ultimately allowing for cross-bridging

SERCA 1

The SERCA pump found on the sarcoplasmic reticulum membrane of skeletal muscle mainly responsible for moving Ca²⁺ out of the cytoplasm

SERCA 2A

The SERCA pump found on the sarcoplasmic reticulum membrane of cardiac muscle mainly responsible for moving Ca²⁺ out of the cytoplasm

Phospholambin

A cAMP protein that regulates SERCA 2A via phosphorylation

Smooth Myocytes

Small, spindle shaped muscle cells found in smooth muscle

Dense Bodies

Electron-dense regions in smooth muscle where multiple actin filaments join together, found immediately beneath the membrane and deep into the cell

Myosin Light Chain Kinase

An enzyme found in smooth muscle that phosphorylates the light chains of myosin to promote cross-bridging and contraction

Myosin Light Chain Phosphatase

An enzyme found in smooth muscle that dephosphorylates the light chains of myosin to terminate contraction

Multiunit Smooth Muscle

Organization of smooth muscle such that individual myocytes are unconnected by gap junctions, thus acting independently of one another

Unitary Smooth Muscle

Organization of smooth muscle such that individual myocytes are electrically coupled via gap junctions, allow contraction as a single unit

Varicosity

The expansion of the point of innervation by a neuron on smooth muscle, responsible for holding and releasing neurotransmitter across the cell

Slow Wave Contraction

The electrical activity of smooth muscle in which waves of slow hyperpolarization and action potential spikes occur without outside stimulus

Calmodulin

The calcium-binding protein found in smooth myocytes that activates myosin light chain kinase

Store-Operated Ca²⁺ Channels

Channels found on the membrane of smooth muscle that is opened by the sarcoplasmic reticulum upon depletion of the SR calcium stores

RyR3

Ryanodine receptors found on the sarcoplasmic reticulum of smooth muscle

RyR2

Ryanodine receptors found on the sarcoplasmic reticulum of cardiac muscle

RyRs

Ryanodine receptors found on the sarcoplasmic reticulum of skeletal muscle

IP3

Second messengers of G-protein coupled receptors in smooth muscle that activate SR calcium channels

Calreticulin

The protein found in the smooth muscle sarcoplasmic reticulum that keeps Ca²⁺ bound, reducing the free concentration of calcium ions

Latch-Bridge Mechanism

The mechanism in sustained-contracting smooth muscle where myosin cross-bridges remain attached to actin filaments for a long period of time after dephosphorylation in order to preserve muscle tension and energy