muscle tissue

Smooth Muscle Tissue

Fusiform shape (tapered at ends), short, nonstriated, with one centrally located nucleus.

Cardiac Muscle Tissue

Short, bifurcated, striated, with one or two centrally located nuclei and intercalated discs between cells.

Skeletal Muscle Tissue

Long, cylindrical, parallel, unbranched, multinucleated fibers with nuclei along the periphery.

Functions of Smooth Muscle Tissue

Involuntary muscle movements to move materials through organs.

Functions of Cardiac Muscle Tissue

Involuntary contraction and relaxation to pump blood into the heart.

Functions of Skeletal Muscle Tissue

Moves bones along the skeleton, responsible for body movements and heat production.

Epimysium

Connective tissue that surrounds the entire muscle, providing strength and protection.

Perimysium

Connective tissue surrounding fascicles, allowing specific movements by activating certain muscle fibers.

Endomysium

Thin connective tissue layer surrounding each individual muscle fiber.

Role of Blood Vessels in Skeletal Muscle

Bring oxygen and nutrients to the muscle and carry away waste.

Role of Nerves in Skeletal Muscle

Send signals from the brain to tell the muscle when to contract.

Thin Filaments Components

Made of actin with active sites for binding, surrounded by tropomyosin and regulated by troponin.

Thick Filaments Components

Made of multiple myosin molecules containing heads that bind to actin during contraction.

Contractile Proteins in Skeletal Muscle

Myosin and actin that generate force and movement during muscle contraction.

Regulatory Proteins in Skeletal Muscle

Troponin and tropomyosin that control when muscles contract and relax.

Sliding Filament Mechanism

Muscle contraction occurs when thin filaments slide past thick filaments, shortening the sarcomere.

Action Potential at Neuromuscular Junction

Initiated when neurotransmitter acetylcholine (ACh) is released and binds to nicotinic receptors, leading to muscle contraction.

Creatine Phosphate

Quickly provides energy to regenerate ATP during the first few seconds of muscle contraction.

Anaerobic Glycolysis

Produces ATP without oxygen by breaking down glucose, resulting in lactic acid if oxygen is insufficient.

Aerobic Respiration

Produces ATP using oxygen by breaking down glucose, pyruvic acid, or fats in the mitochondria.

Muscle Fatigue Causes

Include low ATP levels, lactic acid buildup, ion imbalances, and damage to sarcoplasmic reticulum.

Motor Unit

Consists of one motor neuron and all the muscle fibers it controls; size affects movement precision.

Motor Unit Recruitment

Activating more motor units enhances muscle contraction strength.

Twitch Contraction Phases

Latent period, contraction phase, and relaxation phase characterize a twitch in muscle fibers.

Isotonic Contraction

Muscle tension remains constant while length changes; includes concentric and eccentric contractions.

Isometric Contraction

Muscle tension remains constant without changing length; occurs during posture holding.

Slow Oxidative Fibers (Type 1)

Contract slowly, resist fatigue, have many mitochondria and myoglobin, used in low-intensity activities.

Fast Oxidative Fibers (Type IIa)

Contract quickly, use both aerobic and anaerobic pathways, resistant to fatigue, used in walking or jogging.

Fast Glycolytic Fibers (Type IIx)

Contract quickly using anaerobic glycolysis, fatigues easily, used for high-intensity exercise.

Effects of Aging on Skeletal Muscle

Sarcopenia leads to muscle fiber loss, reduced force production, and difficulties in movement.

Disorders of Muscular Tissue

Can lead to muscle loss, reduced strength, balance issues, and increased fall risk in older adults.