UNIT 3 - pe studies

muscle belly

the large, central part of the muscle which is responsible for contracting and generating force

epimysium

outer connective tissue layer that surrounds the entire muscle belly and helps protect the muscle and provides structure

endomysium

the connective tissue that surrounds each individual muscle fiber, provides support and helps transport nutrients and wastes

fascicle

a bundle of muscle fibers within the muscle which are grouped together by the perimysium

perimysium

the connective tissue surround each fascicle which provides structure and a conduit point for nerves and blood vessels

muscle fibers

individual muscle cells that make up the fascicle and are elongated, multinucleated cells which are capable of contracting

myofibril

thread like structures within the muscle fiber and they contain actin and myosin filaments responsible for creating movement

three types of connective tissue

epimysium, perimysium and endomysium

type I

slow twitch fibers are used for longer duration events and are purely aerobic events

type IIa

fast twitch fibers are used for speed and power events and requires both aerobic and anaerobic elements

producing movement

skeletal muscles that are consciously controlled are attached to two different bones across the joint, which creates movement which enable the human body to perform day to day tasks and respond quickly to changes in the external environment

origin

the attachment to the bone that does not move when the muscle contracts which is the attachment point at the proximal end

insertion

the attachment to the bone that does move when the muscle contracts which is the attachment point at the distal end

agonist

the muscle responsible for the movement

antagonist

the muscle that relaxes to allow the movement to occur

reciprocal inhibition

describes the coordinated relaxing of muscles on one side of a joint to accommodate contraction on the other

reciprocal inhibition - examples

bicep curls: agonist is the biceps which contracts and antagonist is the triceps which relaxes

three types of muscle contraction

concentric: muscle shortens, eccentric: muscle lengths and isometric: muscle stays the same

concentric contraction

movement is in the opposite direction to gravitational pull which the muscle shortens when tension is developed

eccentric contraction

movement is in the same direction as gravitational pull which the muscle lengthens when tension is developed

isometric contraction

muscle contracts but no movement occurs, no change in muscle length and the greatest potential for force generation as maximum number of cross bridges can be attached to actin simultaneously

sarcomere

comprises the unit between the two z lines and make up the functional unit of a muscle fiber

actin

thin protein filament which is attached to the Z line which pulls the z line towards the midline of the sarcomere in a concentric contraction

myosin

thick protein filaments attached to the midline, contains cross bridges which can attach to actin when stimulated by calcium

interaction between calcium and muscle proteins that bring about muscle contractions

without calcium: troponin-tropomyosin blocks binding sites on actin so that actin and myosin cant interact + with calcium: troponin-tropomyosin unblocks binding sites enabling actin and myosin to interact

z lines

found at either end of a sarcomere which come closer together in concentric contractions and spread further apart during eccentric contractions

cross bridges

tiny projections from myosin that attach temporarily to actin, pulling the actin filaments towards the midline of a sarcomere creating movement through concentric contraction

h zone

space between the actin which gets longer or shorter as the sarcomere changes lengths

i band

the light band that contains the thin actin filaments as in a relaxed muscle the actin does not completely overlap the myosin

a band

it contains both actin and myosin and is the center of the sarcomere

sliding filament theory

a theory used to explain the mechanism of muscle contraction based on the interaction of actin and myosin filaments to generate movement

steps 1-4 of the sliding filament theory

a neurochemical stimulation releases calcium from the sarcoplasmic reticulum into the sarcomere - causes actin to reveal binding sites for myosin head to bind to - myosin heads bind to actin which creates cross bridges - breakdown of ATP releases energy to stimulate the myosin cross bridges to pull the actin towards the midline of the sarcomere

steps 5-8 of the sliding filament theory

causes shortening of the sarcomere as the actin and myosin filaments slide over each other, causing z line to come close together - shortening each sarcomere, shortens myofibril, shortens muscle and movement occurs - cross bridges attach and reattach at different times to create movement and maintain tension - this process keeps repeating if the neural impulse is present or the muscle relaxes if the neural impulse ends

force velocity relationship definition (concentric contraction)

describes the relationship between force production and the velocity of movement

force velocity relationship summary (concentric contraction)

greater force required the slower the speed of contraction due to the number of cross bridges that can be attached eg. it is easier to lift heavy weights upwards (concentric) slowly than it is quickly

force length relationship definition

relates to the amount of muscle force that can be produced at varying muscle lengths

force length relationship summary

when a muscle is fully contracted/fully lengthened, only a small force can be generated due to the greatest overlap/insufficient overlap of actin and myosin, reducing potential to contract

nervous control of muscular system

brain: sends messages in the form of action potentials to the spinal cord - spinal cord: transmits the messages between the brain and the muscle - motor neurons: receive the message and deliver it to the targeted muscles - sensory neurons: sends messages back to the brain via spinal cord - brain: analyses the information to determine the next action and then the process repeats

functions of the nervous system

through sensory organs and neurons it receives information about changes in the body and the environment which sends to the spinal cord and brain, the brain determines a suitable response and the brain sends commands to muscles to carry out selected response

central nervous system: CNS

the brain and spinal cord are the two main parts, the spinal cord is responsible for delivering messages to and from the body and brain and the brain is responsible for analysing, determining a response and sending messages to targeted muscles so movement can occur

peripheral nervous system: PNS

it is made up of a sensory and motor division which includes sensory and motor neurons which transmit messages to and from the CNS

two main components of the peripheral nervous system

sensory and motor division

two main components of the nervous system

central and peripheral nervous system

sensory division

made up of sensory neurons which carry messages from the body and environment to the spinal cord and brain

motor division

made up of motor neurons which carry messages from the brain to the muscles to respond appropriately

motor neuron

a cell within the nervous system that transmits impulses/signals to other nerve cells/muscles

three parts of a motor neuron

dendrites, axon and cell body

dendrites

act as antennas to detect the impulse from the sensory receptors and then deliver it to the cell body

cell body

contains the nucleus which directs the neurons activities and sends the messages to the axon

axon

transmits messages away from the cell body to the muscle

motor end plates

motor neurons attach to muscles at the motor end plate which joins the neuron to the muscle and delivers impulses

motor unit definition

the motor neuron and the fibers it activates/innervates

size of the motor unit

the number of muscle fibers within each motor unit can vary with some innervating a small number of fibers and others comprise of more muscle fibers

size of the motor unit - small

the smaller the motor unit, a small number of muscle fibers it innervates, the more precise the action of the muscle is resulting in a lower action potential eg. eye

size of the motor unit - large

the larger the motor unit, a large number of muscle fibers it innervates, the gross motor skills of muscles resulting in a higher action potential eg. quadricep when kicking a ball

all or none principle

when a motor unit receives stimulation/impulse/action potential that exceeds the threshold, all the muscle fiber associated with it will contract to their maximum potential

type IIb

fast twitch fibers are used for speed and power events and purely anaerobic events

motor unit recruitment

refers to the increasing number of motor units firing to increase the force being generated and it is based on exercise intensity

four relationships between muscle contraction and nerve function

all or none principle, size of motor unit, motor unit recruitment and frequency impulse

frequency impulse

force produced by a muscle can be increased by either increasing the number of motor units which increases stimulus size or increasing the frequency at which impulses are sent to the motor unit resulting in the motor unit firing repeatedly

concentric and eccentric contraction

eccentric contractions everything increases except a band stays the same and concentric contractions everything decreases except a band stays the same

role of nervous system at the beginning of a sprint

sensory neurons detect the sound and send electric impulses to the brain - brain interprets the information and sends impulse for movement to occur - spinal cord transmits signals to the muscles via motor neurons - motor neurons transmit electrical signal away from the cell body to the muscle fibers - motor units receives signal to cause contraction of the associated muscle fibers

muscle fiber characteristics - type I, type IIa and type IIb

colour: red, white, white - contraction speed: slow, fast, very fast - force production - low, high, very high - resistance to fatigue: high, medium, low - activity type: aerobic, long term anaerobic, short term anaerobic