functional anatomy

Question 1

what does skeletal muscle link?

Answer 1

links two bones across its connecting joint

• as a result it is responsible for moving the skeleton via contraction of muscles
• occurs via voluntary control

Question 2

what are the two types of skeletal muscle?

Answer 2

• fast twitch (white)- power based athletes

- slow twitch (red)- endurance based athletes

Question 3

How is a muscle structured (from epimysium to muscle fibre)

Answer 3

• skeletal muscle surrounded by epimysium
• made up of bundles of muscle fibres (fascicles) surrounded by perimysium
• each fascicle contains individual muscle fibres, surrounded by endomysium
• fibres arranged into myofibrils, running parallel to each other the length of muscle fibre
• myofibrils contain chain of sarcomeres, composed of actin and myosin filaments which create movement

Question 4

what is the epimysium?

Answer 4

connective tissue sheath surrounding each muscle

Question 5

what is perimysium?

Answer 5

connective tissue which surrounds each bundle of muscle fibres

Question 6

what is endomysium?

Answer 6

connective tissue which surrounds each individual muscle fibre

Question 7

what is a fascicle?

Answer 7

a bundle of skeletal muscle fibres surrounded by the perimysium

Question 8

what is a myofibril?

Answer 8

• small, thread like stands that run through each muscle fibre

Question 9

what is the origin point of a bone attachment?

Answer 9

• the attachment onto the bone that doesn’t move when the muscle contracts
• it is the attachment point at the proximal end

Question 10

what is the insertion point of a bone attachment?

Answer 10

• attached to the bone which moves when the muscle contracts

- is the attachment point at the distal end

Question 11

how do muscles work in pairs?

Answer 11

muscles can only pull not push
the agonist (prime mover) is the muscle responsible for the movement
the muscle that relaxes to allow this to occur is the antagonist

Question 12

what is reciprocal inhibition?

Answer 12

• describes the coordinated relaxing of muscles on one side of a joint to accomodate contraction on the other side of that joint

Question 13

What is a sarcomere?

Answer 13

comprises of the unit between the two Z-lines and makes up the functional unit of a muscle fibre

Question 14

what are the z-lines?

Answer 14

• found at either end of the sarcomere, the z-lines come closer together in concentric contraction and spread further apart as muscles relax or in eccentric contraction

Question 15

what is actin?

Answer 15

the thin protein filament attached to the z-lines. Cross bridges on the myosin attach to the actin when stimulated by the release of calcium to create movement
- they pull the z-line towards the midline of the sarcomere in concentric contraction

Question 16

what is myosin?

Answer 16

• thick protein filaments that contain cross bridges

the myosin cross bridges attach to the actin when stimulated in the presence of calcium

Question 17

what are the contractile filaments?

Answer 17

actin and myosin

Question 18

what are the cross bridges?

Answer 18

tiny projections on myosin filaments that attach to the actin filaments, pulling the actin filaments towards the midline of the sarcomere, making the H-zone smaller which shortens the sarcomere

Question 19

what is the H-zone?

Answer 19

• the space between the actin filaments which gets longer or shorter as the sarcomere changes in length

Question 20

what is the sliding filament theory?

Answer 20

it explains how the sarcomeres within each myofibril shorten
- shortening of the sarcomere results in the shortening of the myofibril, which shortens the muscle resulting in movement

Question 21

Explain the steps in the sliding filament theory:

Answer 21

1. a neurochemical stimulation results in calcium being released into the muscle
2. this results in a reaction in each muscle fibre between contractile proteins
3. myosin filaments have cross bridges spaced along at regular intervals
4. when stimulated by the release of calcium, the cross-bridges attach to the actin filaments and pull the actin filaments towards the midline of the sarcomere
5. this results in the shortening of the sarcomere. the actin and myosin filaments ‘slide-over’ each other as the muscle shortens
6. shortening each sarcomere shortens the myofibril resulting in the shortening of the muscle fibres and movement occurs
7. cross bridges attach and re-attach at different times on them to create movement and maintain tension
8. when the contraction finishes, the myosin and actin filaments return to a relaxed position

Question 22

what occurs in a concentric contraction?

Answer 22

• muscle shortens
• movement is in the opposite direction to the gravitational pull
• z-lines come closer together
• h-zone gets smaller
• sarcomere shortens
• myofibril shortens
• muscle fibre shortens
• tension develops across a joint
• movement occurs

Question 23

what occurs in an eccentric contraction?

Answer 23

• muscle lengthens
• movement is in the same direction as gravitational pull
• z-lines move further apart
• h-zone gets bigger
• sarcomere shortens
• myofibril lengthens
• muscle fibre lengthens
• tension develops across a joint
• movement occurs

Question 24

what occurs in an isometric contraction?

Answer 24

• muscle length doesn’t change
• muscle contracts but no movement occurs
• no change in muscle length
• greatest potential for force generation as maximum number of cross bridges can be attached to the actin at the same time

Question 25

what is the nervous control process over muscular contraction?

Answer 25

sensory neurons- detect the information from the ears, eyes that start the signal or bell had been sounded and the receptors pass the information to the cell body that then sends the signal to the brain brain- interprets the information received from the sensory neuron, processes it and select an appropriate response. Sends out a signal to the CNS for movement to begin Spinal cord- receives the signal from the brain and passes it on to the appropriate motor neurons for movement to occur Motor neuron- dendrites receive the signal from the spinal cord, passes it to the cell body and then it travels down the axon to the muscle fibres that need the innervating movement to occur Motor unit- comprises of the motor neuron and the muscle fibres that it innervates. Receives the signal from spinal cord and passes it along until it reaches the neuromuscular junction for the muscle fibres to contract

Question 26

what is the spinal cord?

Answer 26

responsible for the transmission of messages between the brain and muscle fibres -it relays information from the brain to the body and back

Question 27

what is a motor neuron?

Answer 27

refers to the neurons located in the CNS that protect their axons outside the CNS and directly or indirectly control muscles responsible for carrying impulses away from the spinal cord and brain to muscles or glands

Question 28

what does a motor neuron consist of?

Answer 28

cell body- directs neurons activities dendrites- act as branches to pick up the impulse axon- transmits the message to the muscle and away from the cell body motor end plates- which attach to the muscle fibres

Question 29

How do you increase the strength of a muscular contraction?

Answer 29

send more signals resulting in the recruitment of more motor units

Question 30

what does the number of muscles in each unit generally show about the muscle?

Answer 30

the less number of fibres the smaller the motor unit- the more precise the action (eg muscle of the eye) the larger motor unit usually results in recreation of large gross motor skills (thigh kicking a ball)

Question 31

what are type 1 muscle fibres?

Answer 31

slow twitch fibres endurance based athletes aerobic ATP production

Question 32

characteristics of type 1 muscle fibres:

Answer 32

- slow contraction speed - small motor neuron - high resistance to fatigue - uses aerobic energy system - low force production - high capillary density - high oxidative density - low glycolytic capacity - major fuel source is tryglycerides and glycogen

Question 33

what are type 2 muscle fibres?

Answer 33

fast twitch muscle fibres speed and power events type 2a and 2b

Question 34

characteristics of type 2a muscle fibres:

Answer 34

- fast contraction speed - large motor neuron - medium resistance to fatigue - long term aerobic activities - high force production - intermediate capillary density - moderate oxidative density - high glycolytic capacity - major fuel source is creatine phosphate

Question 35

characteristics of type 2b muscle fibres:

Answer 35

- very fast contraction speed - very large motor neuron - low resistance to fatigue - short term anaerobic activities - very high for production - low capillary density - - low oxidative density - high glycolytic capacity - creatine phosphate major fuel source

Question 36

what is force velocity in the body?

Answer 36

describes the relationship between force production and the velocity of movement

Question 37

describe the relationship between force velocity in an eccentric contraction?

Answer 37

1. when velocity of contraction is low a small force is generated 2. as velocity of contraction increases, force generated increases 3. max force achieved when velocity of contraction is max the greater force required, faster velocity of contraction and vice versa

Question 38

describe the relationship between force velocity in a concentric contraction:

Answer 38

1. maximum force is achieved when a muscle contracts at low velocity 2. as velocity of contraction increases, force generated decreases 3. only a small force is generated when muscle contracts at maximum velocity greater force required, slower speed of contraction vice versa

Question 39

what does force length relate to in FA?

Answer 39

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

Question 40

how does length of muscle affect how much force is produced?

Answer 40

tension is best achieved when muscle is at normal resting length as it increases number of cross bridges that can be attached between the myosin and actin muscles generate less force as it contracts beyond optimal length -muscles generate less force as lengthen beyond optimal length

Question 41

how is the force produced influenced by the joint angle?

Answer 41

- as muscle changes length during contraction, joint angle around which movement occurs changes - angle of the joint across which the muscle is contracting influences how much force can be generated - joint angle at which the muscle can generate its greatest force varies but usually is near middle of joint ROM as it allows greatest number of cross bridges to be attached - decrease in force generated when joint angle is large/small as it affects number of cross bridges which can attach

Question 42

how does the brain maximise the force produced?

Answer 42

1. brain increases size of stimulus (more motor reach their stimulus threshold and innervating results in more muscle fibres contracting which will increase force produced 2. increasing frequency at which the impulses are sent to the motor unit. More often sent= more force produced