IB SEHS Unit 4

Label a diagram of a neuron

Dendrite- Allows transfer of info

Cell body- Provides structure

Nucleus- Cells control center

Axon- Main component of nerve signal transmission

Motor end plate- Where the neuron is unmyelinated and joins with a muscle

Synapse- The gap between the muscle and the MEP

Muscle- Receives the message

Acetylcholines role in neuromuscular junctions

A small molecule that acts a chemical messenger that triggers the firing of motor neurons and affecting voluntary movements (contracts)

Cholinesterase role in neuromuscular junctions

Breaks down the acetylcholine (relaxes)

SFT steps

1. action potential arrives at the neuromuscular junction

2. cell membrane is depolarized, acetylcholine is released, sodium goes into cell

3. calcium is released from sarcoplasmic reticulum into muscle

4. calcium binds to troponin (on tropomyosin) causes movement and revealing myosin binding sites on actin

5. ATP is hydrolyzed to form ADP + phosphate

6. myosin head binds to actin and forms cross bridges (stays there until ATP molecule releases it) - if calcium is still there cross bridge is still there

7. ADP is released causing myosin heads to activate and move towards center of sarcomere (Power stroke)

8. power stroke is continued till z lines are pulled toward H zone

9. calcium is transported back causing termination of cross bridge.

10. myosin binding sites covered by tropomyosin and troponin (returns to original state)

Myofibril

Elongated contractile threads found in striated muscle cells

Myofilament

The structure that makes up the myofibril, examples include Actin and Myosin

Sarcomere

Structural unit of a myofibril consisting of a dark band and near a pale band

Actin (I band)

thin filaments only, The protein that forms the contractile filaments of muscle cells

H zones

Contains only thick filaments and shortens during contraction

Myosin (A band)

The fibrous protein that forms the contractile filaments of muscle cells, Thick bands

Z line

end of sarcomere

Tropomyosin

Found in actin, blocks muscle contraction

Sarcoplasmic reticulum

Contains and releases calcium

Calcium ions

Bonds to troponin and reveals the binding sites on the actin

ATP

Fuel for muscle contraction, splits into ADP and P

Type I

Activity- Light activity

Glycogen- Low

Type IIa

Activity- Long duration low intensity

Glycogen- High

Type IIb

Activity- Short duration high intensity

Glycogen- High

Flexion

Decrease the angle of a joint

Extension

Increase the angle of a joint

Abduction

movement away from the midline of the body

Adduction

Movement toward the midline of the body

Pronation

Rotation of Forearm where the palm of the hand is facing down

Supination

Rotation of Forearm where the palm of the hand is facing up

Elevation

Raising of the shoulder girdle

Depression

Lowering of the shoulder girdle

Rotation

Movement around a pivotal point

Circumduction

A circular movement/direction resembling a cone

Dorsiflexion

Raising of the foot/toes towards the body \n - Decreasing angle between tibia and foot

Plantar flexion

Pointing of the toes/ foot towards the body \n - increasing angle between tibia and foot

Eversion

Turning of the sole of the foot outwards

Inversion

Turning of the sole of the foot inwards

Isotonic

when the muscles either shortens or lengthens during contraction

Isometric

When a muscle contracts with no resulting movement

Isokinetic

A muscle contraction with constant speed

Concentric vs Eccentric

Muscle shortens, muscle lengthens

Agonist

Prime mover - contracts to cause movement

Antagonist

Relaxes to allow movement

DOMS

delayed onset muscle soreness (24-72 hours after eccentric muscle contraction) and is associated with structural muscle damage, inflammatory reactions in the muscle, overstretching and overtraining. \n \n DOMS is prevented/minimized by reducing the eccentric component of muscle actions during early training, starting training at a low intensity and gradually increasing the intensity, and warming up before exercise, cooling down after exercise.

Fixator

Stabilizes the origin of a prime mover

Synergist

Neutralizer, whom contract isometrically to prevent unwanted actions against the agonist/ antagonist