SK Ch. 2 Neuromuscular Fundamentals

muscle functions

Provide protection, posture, and produce a large % of body heat.

Skeletal Muscles % body weight

40-50% of body weight

Muscle Nomenclature

Naming based on visual appearance, shape, size, number of divisions, anatomical location, points of attachment, and function.

Parallel Muscles

These muscles produce a greater range of movement and can be flat (e.g., rectus abdominis), fusiform (e.g., biceps brachii), strap (e.g., sartorius), radiate (e.g., pectoralis major), or sphincter/circular.

Pennate Muscles

These muscles have shorter fibers arranged obliquely like a feather, increasing cross-sectional area and force. They can be unipennate (e.g., biceps femoris), bipennate (e.g., rectus femoris), or multipennate (e.g., deltoid and gluteus maximus).

Epimysium

connective tissue surrounding entire muscle

Myosin

Thick filaments

Slow twitch

less tension, high fatigue resistance

Irritability or Excitability

muscle property of being sensitive or responsive to chemical, electrical, or mechanical stimuli

Hypertrophy

The increase in the size of an organ or tissue due to the enlargement of its cells.

Hyperplasia

A condition characterized by an increase in the number of cells in a tissue or organ.

Atrophy

The partial or complete wasting away of a part of the body, often caused by factors like immobilization or sedentary lifestyle.

How many pairs of skeletal muscles?

215 pairs

perimysium

tissue surrounding fascicles or muscle fibers

endomysium

Tissue surrounding individual muscle fibers

Actin

Thin filaments

Fast twitch fibers

Faster contraction, quick fatigue

contractility

ability to shorten when an adequate stimulus is received

extensibility

the ability to be passively stretched beyond its normal resting length

isometric (static)

when a significant amount of active tension may be developed in the muscle to maintain the joint angle in the same position

isotonic (dynamic)

varying degrees of active tension in the muscles are either causing joint angles to change or controlling the joint angle

elasticity

ability of a muscle to return to it's original resting length after stretching

Flat muscles

usually thin & broad, originating from broad, fibrous, sheet-like aponeuroses allows them to spread their forces over a broad area

Flat muscle examples

rectus abdominus & external oblique

Fusiform muscles

spindle-shaped; thick in the middle and tapered at each end

Fusiform muscle examples

biceps brachii, brachialis, brachioradialis

Strap muscles

more uniform in diameter with essentially all fibers arranged in a long parallel manner; enables a focusing of power onto small, bony targets

Strap muscle example

sartorius

Radiate muscles

also described sometimes as being triangular, fan-shaped or convergent; have combined arrangement of flat & fusiform
originate on broad aponeuroses & converge onto a tendon

Radiate muscle examples

pectoralis major, trapezius

Sphincter or circular muscles

technically endless strap muscles
surround openings & function to close them upon contraction

Sphincter or circular muscle examples

orbicularis oris surrounding the mouth

Unipennate muscle

run obliquely from a tendon on one side only

Unipennate muscle examples

biceps femoris, extensor digitorum longus, tibialis posterior

bipennate muscle

muscle fibers on both sides of the tendon

bipennate muscle examples

rectus femoris, flexor hallucis longus

Multipennate muscles

have several tendons with fibers running diagonally between them

Multipennate muscle example

deltoid

Intrinsic

pertaining usually to muscles within or belonging solely to body part upon which they act

Extrinsic

pertaining usually to muscles that arise or originate outside of (proximal to) body part upon which they act

Action

specific movement of joint resulting from a concentric contraction of a muscle which crosses joint

Innervation

occurs in the segment of the nervous system responsible for providing a stimulus to muscle fibers within a specific muscle or portion of a muscle

Amplitude

range of muscle fiber length between maximal and minimal lengthening

gaster

central, fleshy portion of the muscle that generally increases in diameter as the muscle contracts;
the contractile portion of muscle

Tendon

tough yet flexible bands of fibrous connective tissue, connects muscles to bones

Aponeurosis

A tendinous expansion of dense fibrous connective tissue that is sheet- or ribbonlike in appearance and resembles a flattened tendon; binds muscles together

Fascia

a band or sheet of fibrous connective tissue that covers, supports, and separates muscle

Retinaculum

connective tissue band that tendons from separate muscles pass under; common in joints of wrist and ankle

Origin

structurally: proximal attachment
Least moveable part of muscle

Insertion

Structurally: distal attachment
Most moveable part of muscle

Origin/Insertion example

biceps brachii muscles has origin on scapula (least movable bone) and its insertion on the radius (most movable bone)

Agonist

cause joint motion through a specified plane of motion

Anatgonist

opposite concentric action from agonist

Primary movers

muscle responsible for a particular movement- aka agonist

Stabilizers

surround the joint or body part and contract to fixate or stabilize the area to enable another limb to exert force and move

Synergist

Muscles that assist in the action of an agonist bus are not necessarily prime movers

Helping synergist

have an action in common but also have actions antagonistic to each other; help move joint in desried manner while also preventing undesired actions

true synergist

contract to prevent an undesired joint action of agonist and have no direct effect on agonist action

Neutralizers

counteract or neutralize the action of another muscle to prevent undesirable movements such as inappropriate muscle substitutions

Force couples

occur when two or more forces are pulling in different directions on an object, causing the object to rotate about its axis

Palpatation

the act of feeling with the hand, placing two fingers on the body to examine the muscle as it contracts

Isokinetics

a specific technique that may use any or all of the different types of contractions; type of dynamic exercise

Central Nervous System (CNS)

brain and spinal cord

Peripheral Nervous System (PNS)

nerves

somatic nervous system

the division of the peripheral nervous system that controls the body's skeletal muscles

Automic Nervous System

division of the PNS consisting of nerves that control all of the involuntary muscles, organs, and glands

Cerebral Cortex

controls voluntary muscle movement and aggregate muscle actions

basal ganglia

structures in the forebrain that help to control movement, posture, equilibrium

Cerebellum

A large structure of the hindbrain that controls fine motor skills, feedback control

Brainstem

responsible for automatic survival functions; arousal and maintenance of wakeful state

Afferent system

The part of the PNS that sends messages to the CNS.

Efferent system

the division of the peripheral nervous system that brings information from the brain to the body

Neurons

a nerve cell; the basic building block of the nervous system

Dendrites

Branchlike parts of a neuron that are specialized to receive information.

Cell body

Largest part of a typical neuron; contains the nucleus and much of the cytoplasm

Axon

the extension of a neuron, ending in branching terminal fibers, through which messages pass to other neurons or to muscles or glands

Myelin Shealth

A layer of fatty tissue segmentally encasing the fibers of many neurons; enables vastly greater transmission speed of neural impulses as the impulse hops from one node to the next.

Nodes of Ranvier

gaps in the myelin sheath

Axon terminal

The endpoint of a neuron where neurotransmitters are stored

Reciprocal inhibition

The simultaneous contraction of one muscle and the relaxation of its antagonist to allow movement to take place

Tension is proportional to...

the number of cross bridges connected

passive insufficiency

When a muscle cannot stretch anymore, occurs with the antagonist; no overlap/cross bridge

active insufficiency

When a muscle cannot shorten anymore, occurs with the agonist; too much overlap

Proprioception

The cumulative sensory input to the central nervous system from all proprioreceptors that sense body position and limb movement.

Kinesthetics receptors

Ruffini Receptors; joint capsule
Free nerve endings; connective tissue
Paciniform corpuscles; skin, tendons, joint capsules

Stretch reflex

the contraction of a muscle in response to stretch of that muscle; knee jerk

Golgi Tendon Organ (GTO)

A specialized sensory receptor located at the point where skeletal muscle fibers insert into the tendons of skeletal muscle; protect us from excessive tension

Dermatome

Area of skin supplied by a single spinal nerve

Myotome

muscle or group of muscles supplied by a specific spinal nerve

Sensory neurons

transmit impulses to the spinal cord and brain from all parts of the body

Motor neurons

transmit impulses away from the brain and spinal cord to muscle and glandular tissue

Interneurons

central or connecting neurons that conduct impulses from sensory neurons to motor neurons

Kinethesis

conscious awareness of position and movement of the body in space

All or none principle

Refers to the fact that the action potential in the axon occurs either full-blown or not at all.

Action potential

a neural impulse; a brief electrical charge that travels down an axon

subthreshold stimulus

stimulus not strong enough, so no contractions seen

threshold stimulus

minimal level of stimulation required to cause a muscle fiber to contract

submaximal stimulus

Stimuli of increasing strength that create more action potentials along more neurons

maximal stimulas

The stimulus above which no stronger contraction can be elicited, because all motor units are firing in the muscle.

latent period

time between application of a stimulus and the beginning of a response in a muscle fiber