functional anatomy - pe

muscle belly

-surrounded by an epimysium

-made up of bundles of fascicles, each surrounded by a perimysium

fascicle

contains individual muscle fibers, each surrounded by an endomysium

muscle fibers

arranged into myofibrils, running parallel to each other and the length of the muscle fiber

myofibrils

contain a chain of sarcomeres, which are composed of actin and myosin filaments responsible for creating movement

3 types of muscle contraction

• concentric

• eccentric

• isometric

concentric contraction

• opposite direction of gravity

• muscle shortens

• e.g bicep curl

eccentric contraction

• movement in the same direction as gravity

• muscle lengthens

• e.g down motion in a bicep curl

isometric contraction

• muscle contracts, but no movement occurs

• no change in muscle length

• e.g plank

actin

• thin protein filament attached to the z-line

myosin

• the thick protein filament

• contains cross bridges

z-line

• found either end of the sarcomere

• closer together in concentric contraction

• further in eccentric contraction

cross bridges

• tiny projections from myosin filaments that attach temporarily to actin filaments.

• pull actin to m-line

h-zone

• space between the actin filaments and the

i-band

• space between z-line and myosin filament

A-band

-length of myosin filament, remains constant

1-3 sliding filament model

1. a neurochemical stimulation releases calcium from the sarcoplasmic reticulum into the sarcomere

2. Actin filaments reveal a binding site for the myosin head to connect

3. myosin heads bind to the actin filaments, creating a cross bridge

4-5 sliding filament theory

4. breakdown of ATP releases energy to stimulate the myosin cross bridges to pull the actin filaments toward the m-line of the sarcomere

5. results in shortening of the sarcomere as the actin and myosin filaments ‘slide over’ each other causing the z-lines to come closer together and h zone to shorten

6-8 sliding filament theory

6. shortening each sarcomere shortens the myofibril, shortening the muscle, and movement occurs

7. cross bridges attach and re-attach at different times to create movement and maintain tension

8. the process keeps repeating if the neural impulse is present or the muscle relaxes if the neural impulse ends

brain

• sends messages in the form of action potential to the spinal cord

• analyses info delivered from the spinal cord and determines next action

spinal cord

• responsible for the transmission of the message between the brain and the muscle and from the muscle/body to the brain

nervous system 2 parts

• central nervous system (CNS)

• peripheral nervous system (PNS)

CNS

• central nervous system

• brain and spinal cord

PNS

• peripheral nervous system

• made up of sensory neurons and motor neurons

• transmits messages to and from CNS

motor neuron def

a cell within the nervous system that transmits impulses to ther nerve cells

motor neuron 3 parts

• dendrite

• cell body

• axon

dendrite

acts as an antenna 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 message to the axon

axon

transmits the message away from the cell body to the muscle

motor unit

the motor unit and the fibers it activates

all or nothing principle

when a motor unit receives action potential that exceeds the threshold, all the muscle fibers associated with it will contract to their max potential

muscle fiber types

• slow twitch - type I

• fast twitch - type IIa 

• very fast twitch - type IIb

slow twitch - type I characteristics

• slow contraction speed

• used for endurance

• aerobic system

• fatigue resistant

• increased capillary density - more delivery of oxygen to working muscles

• red

fast twitch - type IIa characteristics

• intermediate speed of contraction

• moderate force of contraction

• fatigue resistant 

• some aerobic characteristics

• e.g 400m, 800m run

very fast twitch - type IIb characteristics

• lrg cross sectional area, allows for greater muscle force and power to be generated

• high force of contraction

• rapid contraction speed

• purely anaerobic activities

• low resistance to fatigue

• e.g. 100m sprint/jumps and throws

force - velocity def

describes the relationship between force production and the velocity of movement

force - velocity concentric contraction

1. max force is achieved when a muscle contracts at a low velocity

2. as velocity of the contraction increases, the force generated decreases

3. only a small force is generated when the muscle contracts at max velocity

force - length def

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

force - length - shortened/contracted

• only a small force can be generated

• do to greatest overlap of actin and myosin filaments, reducing potential to contract

force - length - mid length

the greatest force is generated due to the optimal overlap of actin and myosin filaments

force - length - fully lengthened

• only small force can be generated 

• insufficient overlap of actin and myosin filament, reducing potential to contact