Muscular System Intro

What are the 3 types of muscle? Are they un/striated? are they in/voluntary?

1. Skeletal, voluntary, striated

2. Cardiac, involuntary, striated

3. Smooth, involuntary, non-striated

What are the universal properties of skeletal muscle?

Excitability, conductivity, contractility, extensibility, and elasticity.

What is the thin covering of loose connective tissue surrounding each individual muscle fiber called?

Endomysium

What are the thicker connective tissue that wraps muscle fibers together into bundles called fascicles called?

Perimysium

What is the fibrous connective tissue sheath surrounding the entire skeletal muscle called?

Epimysium

What does the epimysium extend between?

Fascicles, to form the perimysium.

Which type of muscle is thick in the middle and tapered at the ends (e.g., biceps brachii); and fairly strong?

Fusiform muscles

Which type of muscle has uniform width and parallel fascicles, and has less strength due to fewer muscle fibers?

Parallel muscles

Which type of muscle is flat and fan-shaped, with fibers radiating from a narrow attachment at one end to a broad attachment at the other, and is relatively strong?

Triangular muscles

Which type of muscle is feather-shaped and fascicles run obliquely to a tendon (unipennate, bipennate, multipennate)?

Pennate muscles

Which type of muscle forms a ring around body openings (orbicularis oculi, urethral and anal sphincters) where contractions prevent passage of material?

Circular Muscles (sphincters)

What is indirect muscle attachment?

Muscle ends in a fibrous tendon that strongly attaches to the periosteum and matrix of the bone (e.g., calcaneal tendon).

What is direct attachment?

Very little separation between muscle and bone. Epimysium fused to periosteum of bone or perichondrium of cartilage

What is an intrinsic muscle?

entirely contained within a particular region, having both its origin and insertion there

What is an extrinsic muscle?

muscle that acts upon a designated region but has its origin elsewhere

Which muscle produces the most force during a particular action?

The agonist (Prime Mover)

Which muscle aids the agonist, helps stabilize a joint, or modifies movement direction?

The synergist

Which muscle opposes the agonist by maintaining tension and limiting speed or excessive movement?

The antagonist

Which muscle prevents the movement of a bone?

The fixator

What is the plasma membrane of a muscle fiber?

The sarcolemma

What is the cytoplasm of a muscle fiber?

The sarcoplasm

What are the microscopic protein filaments that make up muscle cells called?

Myofibrils

What is the carbohydrate that stores and provides energy to cells during exercise?

Glycogen

What is the red pigment that provides some oxygen to cells?

Myoglobin

What smooth endoplasmic reticulum forms a network around myofibrils and serves as a Ca2+ reservoir?

The sarcoplasmic reticulum (SR)

What are the tunnels formed by the sarcolemma that penetrate the cell and carry electrical signals deep inside called?

Transverse (T) tubules

What is composed of hundreds of molecules of the motor protein myosin?

Thick filaments

What is composed of F-actin, G-actin, tropomyosin, and troponin?

Thin filaments

What blocks the active sites of actin when muscle is relaxed to prevent myosin from binding?

Tropomyosin

What is made of titin; anchor thick filaments to Z discs and M line, stabilizing them?

Elastic Filaments

What is a motor unit?

One nerve fiber and all the muscle fibers it innervates. Muscle fibers contract in unison.

What is the point where a nerve fiber meets its target cell called?

Synapse

What is the synapse between a nerve fiber and a muscle fiber (also called motor end plate) called?

Neuromuscular Junction (NMJ)

What is the end of a nerve fiber that contains acetylcholine called?

Axon terminal

What consists of a mat of collagen + glycoprotein that separates muscle fiber and nerve ending from CT?

Basal lamina

What enzyme in the basal lamina and sarcolemma breaks down ACh to turn off muscle contraction?

Acetylcholinesterase (AChE)

What is it called when there is a stable voltage of about -90mV across the sarcolemma of a resting cell, and is maintained by the sodium-potassium pump?

Resting Membrane Potential (RMP)

What happens when Na+ channels open, Na+ rushes in, and the inside becomes positive?

Depolarization

What happens when Na+ channels close, K+ channels open, K+ flows out, and the inside turns negative again?

Repolarization

What is the process where action potentials on the sarcolemma lead to Ca2+ release from the SR and activation of myofilaments?

Excitation-Contraction Coupling

What is the mechanism of contraction called where thin filaments slide over thick filaments, pulling Z discs closer without the filaments themselves shortening?

The sliding filament theory

What takes place when there is a delay between stimulation and the start of contraction, consumed by excitation, ECF coupling, and tensing?

The latent period of muscle twitch

What takes place when the muscle begins to produce external tension and move a resisting object (bone or limb)?

The contraction phase of muscle twitch

What occurs when there is a sustained fluttering contraction where a muscle relaxes only partially between high-frequency stimuli?

Incomplete tetanus

What occurs when if stimulation frequency is high enough, the muscle never begins to relax, and is in continuous contraction?

Complete tetanus

What contraction has no change in muscle length, and tension is absorbed by elastic components?

An isometric contraction

What contraction has a change in muscle length and moves loads?

An isontonic contraction

What is the isotonic contraction called when the muscle shortens as it maintains tension?

A concentric contraction

What is the isotonic contraction called when the muscle lengthens as it maintains tension?

Eccentric Contraction

What type of fiber has red, fatigue-resistant fibers abundant in mitochondria, myoglobin, and capillaries, and is adapted for endurance?

Slow-Twitch (Type I) fibers

What type of fiber has pale, fast-fatiguing fibers adapted for quick, stop-and-go anaerobic activity?

Fast-Twitch (Type II) Fibers

What are the dark lines joining cardiac muscle cells (cardiocytes), containing electrical gap junctions and mechanical junctions called?

Intercalated discs

What type of muscle is striated, has intercalated discs, one nucleus/cardiocyte, and T tubules?

Cardiac muscle

What type of muscle is non-striated, has fusiform cells with a single nucleus, lacks T tubules and sarcomeres, and uses dense bodies for contraction?

Smooth muscle