skeletal muscle activity and movement

excitability

ability to receive and respond to stimuli

2 other terms for excitability

responsiveness, irritability

contractility

ability to shorten when adequate stimulus is received

extensibility

ability of muscle cells to be stretched

elasticity

ability to recoil and resume resting length after stretching

skeletal muscles must be stimulated by a ______ _______ to contract

motor neuron

another term for motor neuron

nerve cell

motor unit

one motor neuron and all skeletal muscle cells that it stimulates

muscle fiber contraction is ____ or _____

all or none

within a skeletal muscle, not all ______ may be stimulated during the same __________

fibers, interval

different combinations of muscle fiber ___________ may give different _________

contractions, responses

graded responses

different degrees of skeletal muscle shortening

2 types of muscle contractions

isotonic, isometric

isotonic contraction and example

muscle shortens, movement occurs (bending knee)

isometric contraction and example

tension increases but muscle doesn’t shorten or produce movement (pushing against wall with bent elbows)

golden rule 1: with a few exceptions, all skeletal muscles cross…

at least one joint

golden rule 2: typically, bulk of skeletal muscle lies __________ to _____ crossed

proximal, joint

golden rule 3: all skeletal muscles have at least…

two attachments (origin, insertion)

golden rule 4: skeletal muscles can only _____, they never _____

pull, push

golden rule 5: during contraction, skeletal muscle __________ moves toward the _______

insertion, origin

body movement is attained due to…

muscle moving an attached bone

origin

attachment to moveable bone

insertion

attachment to immovable bone

flexion

brings bones closer together, decreases angle of joint

extension

moves bones apart, increases angle of joint

rotation

movement of a bone around its longitudinal axis, common in ball and socket joints

abduction

movement of limb away from midline

adduction

movement of limb towards midline

circumduction

combination of flexion, extension, adduction, and abduction

dorsiflexion

lifting foot so toes point up

plantar flexion

depressing foot so toes are pointed

supination

forearm rotates laterally so palms face up

pronation

forearm rotates medially so palms face down

in pronation, radius and ulna…

cross over each other

opposition

move thumb to touch other fingers on same hand

body movement opposite pairs

flexion and extension, adduction and abduction, dorsiflexion and plantar flexion, supination and pronation