Bold = Main, general points

Highlight = shortened definitions/main idea of bolded thing, for easy remembering

Functions:

• Provides movement (locomotion of whole body, facial expressions, blood circulation, food passage) through contraction and relaxation of muscles.

• Maintains posture by stabilizing the body and supporting its structure (works against gravity)

• Produces heat as a byproduct of muscle activity/cellular respiration, contributing to body temperature regulation.

4 Characteristics of Muscle Tissue:

• Excitability: The ability to respond to stimuli (ex. nerve impulses) from motor neuron/hormone

• Contractility: Ability to shorten when stimulated (think like a bicep curl, your bicep contracts/gets shorter when pulling the weight closer)

• Extensibility: The ability to stretch without being damaged, allowing muscles to increase in length even past OG shape (think extend)

• Elasticity: Ability to return to its original length after being stretched

3 Types of Muscle Tissue:

Skeletal Muscle:

• Connected to bones

• Cylindrical

• Striated (striped)

• Multinucleated (multiple nuclei)

• Voluntarily controlled

• Contracts slowly or very quickly (most versatile in contraction speed)

Cardiac Muscle:

• In heart

• Branched (somewhat connected to each other)

• Striated (striped)

• Uninucleated (ONE nucleus)

• Involuntarily controlled

• Slow and steady contractions EXCEPT during short periods of activity/exercise

Smooth Muscle:

• In walls of internal organs

• Arranged in uniform layers

• Nonstriated (NOT striped)

• Uninucleated (ONE nucleus)

• Involuntarily controlled

• Slow contractions, sustained for long periods of time

Microscopic Structure of a Skeletal Muscle:

Largest - Smallest

Muscle -

• Skeletal muscle is attached to bone by tendons

• Made up of many bundles of fibers

Fascicle -

• Bundles of fiber within muscle

Muscle Fiber -

• Long, thin muscle cells

• Each covered by sarcoplasmic reticulum, which transmit an impulse to the muscle fiber

Myofibril -

• Thread-like organelles of muscle fibers

• Structure in long, striated units = sarcomeres

Myofilaments -

• Actin (thin) + Myosin (thick) make up sliding filament model of muscle (contraction)

Muscle Membranes:

Membranes allow for muscle fibers to slide and keeps them contained to prevent bursting during contractions

• Epimysium - covers whole muscle

• Perimysium - covers fascicle

• Endomysium - covers individual muscle fiber

Muscle Contraction:

Arrangement of myofilaments -

Actin + Myosin = Contraction

Attached to each other at Z line (Z disk on diagram woops)

Sarcomere = space between two Z lines

Actin and myosin interact to pull muscle fiber towards M-line, SHORTENS muscle fiber

Contraction:

1. Nerve impulses are sent to muscle fibers to begin contraction

2. Myosin filaments have round extensions/ heads that attach to twisted actin filaments and pull on them, bringing the Z-lines closer, making the sarcomere shorter

3. Repeats until contraction is complete

ATP FUELS THIS PROCESS