muscle 2 flash cards

Skeletal Muscle

Type of muscle that is voluntary and striated.

Myofibril

The basic unit of muscle structure that contracts and is made of myofilaments.

Sarcoplasmic Reticulum

A specialized type of smooth endoplasmic reticulum in muscle cells that helps conduct impulses and initiates contraction.

Neuromuscular Junction

The connection point where a motor neuron communicates with a muscle cell.

Acetylcholine (ACh)

A neurotransmitter released at the neuromuscular junction that stimulates muscle contraction.

Motor Unit

A motor neuron and all the muscle fibers it innervates.

Myofilaments

The proteins, actin (thin) and myosin (thick), that make up myofibrils and are responsible for muscle contraction.

Striations

The alternating light and dark bands on skeletal and cardiac muscle that result from the arrangement of myofilaments.

Sarcoplasm

The cytoplasm of a muscle cell.

T-tubules

Transverse tubules that extend from the sarcolemma into the muscle cell, conducting impulses.

Acetylcholinesterase

An enzyme that breaks down acetylcholine, preventing continuous stimulation of muscle contraction.

Synapse

The junction between two neurons or a neuron and another cell, including muscle or gland cells.

Intercalated Disks

Specialized junctions between cardiac muscle cells that facilitate synchronized contraction.

Smooth Muscle Fiber

Type of non-striated muscle that is involuntary.

Contractile Mechanism

The process in which actin filaments slide over myosin filaments, requiring ATP energy for muscle contraction.

Motor Neuron

A neuron that transmits impulses to muscles, enabling them to contract.

Sarcoplasmic Reticulum

An organelle that releases Ca++ into the sarcoplasm during muscle contraction.

Impulse to Neurotransmitter Terminal

The process in which a nerve impulse travels to a terminal and releases neurotransmitters to initiate muscle contraction.

Calcium (Ca++)

An ion that, when present in the sarcoplasm, initiates the contraction of myofibrils by allowing actin and myosin myofilaments to hook and slide together.

ATP (Adenosine Triphosphate)

A molecule required for both muscle contraction and relaxation processes, specifically for pumping calcium back into the sarcoplasmic reticulum.

Hypertrophy

An increase in size of individual muscle cells due to exercise, leading to an overall increase in muscle size.

Atrophy

A decrease in size of muscle fibers after reaching normal adult size, which can occur due to disuse or nerve injury.

Tetany

A continuous state of muscle contraction often caused by conditions such as low blood calcium.

Fatigue

A decrease in work capacity caused by the depletion of ATP and lack of oxygen, leading to reduced muscle contraction.

Rigor

Muscle stiffness due to a lack of ATP, often resulting from extreme fatigue or death (rigor mortis).

Muscle Tone

Slight muscle tautness at rest, due to continuous low-level nervous stimulation that prevents flaccidity.