Lecture 30: Excitable Tissue Flashcards

Flashcards about excitable tissue: muscle.

The three main types of muscle are skeletal, cardiac, and __.

smooth

__ muscle (skeletal and cardiac) has a highly ordered contractile system whereas smooth muscle has not.

Striated

__ muscle is under conscious control and is responsible for movement of limbs.

Skeletal

__ muscle includes cardiac muscle and smooth muscle.

Involuntary

A group of muscle cells which are innervated by single neuron is known as a __.

motor unit

The cells of skeletal muscle are long and comparatively wide and often referred to as __.

muscle fibres

The basic contractile element is the __.

sarcomere

The __ is the calcium store which releases the calcium that activates contraction.

sarcoplasmic reticulum (SR)

The __ invaginate the surface membrane of the muscle cell (sarcolemma).

t-tubules

At either end of the sarcomere, the thin filaments are attached to the __.

Z line

Each thin filament is composed of four main proteins: F-actin, nebulin, __, and __.

tropomyosin, troponin

The myosin molecules can also form filaments with the myosin molecules polarised along the __.

filament

__ refers to the activation of myosin’s cross bridges.

Contraction

As the sarcomere contracts the thin filaments are pulled over the thick filaments: The Z-discs are pulled toward the __ and the I band and H zone become narrower, while the A bands do not change in length.

M-line

Actin binding promotes __ and therefore when it binds it will promote myosin taking on a new conformation.

ATP hydrolysis

Rebinding ‘fresh’ __ allows the myosin and actin molecules to detach from each other and a return of conformation.

ATP

The cross-bridge cycle includes energization, crossbridge formation, __ and detachment.

power stroke

__ is the only naturally occurring ion which can initiate muscle activation.

Calcium

Muscle is typically relaxed when the calcium level is less than __ mM and activated at 0.001 – 0.01 mM.

0.0001

Removal of the calcium from the cytoplasm is an active process which is ultimately linked to ATP hydrolysis by __ in the surface membrane.

ion pumps

Under normal conditions, maximum isometric force is attained at a sarcomere length of __ µm.

2.0 - 2.2

At lengths < 2.0 µm, active force development is reduced because the __ collide and start to interfere with each other.

ends of filaments

At lengths >2.2 µm, __ increases as elastic connective tissue around the muscle cells is stretched.

passive force

In skeletal muscle opening of __ in the SR allows the movement of calcium ions into the cytosol.

calcium channels

In __ contraction, the muscle changes in length but the tension remains constant.

isotonic

In __ contraction, the muscle does not shorten, so length is constant but tension varies.

isometric