Biology: Muscle Terminology

Evidence of muscle tissue adaptation

Muscle fibers are multinucleated and long.

Proteins of the sarcomere

Actin, myosin, titin, tropomyosin, and troponin.

Functions of titin

Provides elasticity and maintains the structure of sarcomere.

Two types of movement

Voluntary (conscious control, e.g., walking) and involuntary (automatic, e.g., heartbeat).

Fulcrum in the arm

Fulcrum is the elbow joint.

Effort in the arm

Effort is applied by muscles during bicep contraction.

Load in the arm

Load is the weight of the forearm or an object being held.

Range of movement: hinge joint

Allows flexion and extension (e.g., elbow, knee).

Range of movement: ball-and-socket joint

Allows rotation and full range of motion (e.g., shoulder, hip).

Origin of a muscle

The fixed attachment point of a muscle.

Insertion of a muscle

The end of the muscle that moves during contraction.

Synovial fluid in joints

Lubricates joints and reduces friction between bones.

Purpose of synovial fluid

Provides lubrication, shock absorption, and nutrient delivery to cartilage.

Muscle contraction mechanism

Actin and myosin slide past each other in the sliding filament model.

Effect of bones on movement

Bones provide structure and act as levers.

Effect of muscles on movement

Muscles generate force for movement.

Effect of nerves on movement

Nerves send signals to control muscle contraction.

Definition of joints

Joints are where two bones meet and allow movement and flexibility.

Motor neurons and myofibril contraction

Motor neurons send impulses that trigger muscle fiber contraction via calcium release.

Adaptation of dolphins: blubber

Blubber provides insulation and buoyancy.

Adaptation of dolphins: dorsal fin

Dorsal fin provides stability during swimming.

Adaptation of dolphins: smooth skin

Smooth skin reduces drag for faster movement.

Step 1 of Sliding Filament Model

The myosin heads are attached to the binding site on actin forming a crossbridge.

Step 2 of Sliding Filament Model

ATP binds the myosin head breaking the crossbridge.

Step 3 of Sliding Filament Model

ATP is hydrolyzed causing the myosin head to change angles, to become
"cocked" storing potential energy.

Step 4 of Sliding Filament Model

The head uses the energy to attach to another binding site on actin

Step 5 of Sliding Filament Model

With the release of the ADP + P (created during the hydrolysis of ATP) the myosin head pushes the actin filament forward towards the center of the sarcomere.

Contracted muscles

Muscles are shortened with more overlap of actin and myosin.

Relaxed muscles

Muscles are elongated with less overlap of actin and myosin.

Key parts of sarcomere

Includes actin, myosin, Z-line, H-zone, and M-line.

Antagonistic muscles: internal intercostals

Pull ribs down for exhalation.

Antagonistic muscles: external intercostals

Lift ribs up for inhalation.