1. What key words does this bring to mind
Starter
Asked to cover coordinating movement synapses/neuromuscular junctions ……
JOINTS
What key words does this bring to mind
Whiteboards!
GCSE!!

2. Learning Outcomes
Describe how coordinated movement requires the action of skeletal muscles about joints – with reference to the elbow joint.
Compare and contrast the action of synapses and neuromuscular junctions.

3. Joints and Movements
All movement is controlled by muscles pulling on a joint.
Muscles can only pull therefore at least two muscles must be used to move bones back and forth.
Muscles which work in this way are known as antagonistic
Any muscle which contracts and causes extension of a joint is called an extensor
The corresponding flexor muscle contracts to reverse the movement
NB – these are also the ‘general’ terms for the muscles found in the forearm.

4. The action of antagonistic muscles
Raise and lower your lower arm at the elbow and FEEL/DESCRIBE what is happening in upper arm!!!!
Using appropriate terminology explain how antagonistic muscles act together to raise and lower a limb.

5. Muscles can only contract and relax, therefore they can only pull on a bone, not push it
To produce movement, 2 muscles must act as antagonistic pairs to move a bone to and from different positions
To raise a limb, the flexor contracts pulling the limb bone up (extensor relaxed)
To lower the limb, the extensor contracts, pulling the limb down (flexor relaxed)
FEEL IT!!

6. Synovial joint structure
Synovial joints occur where a large amount of movement is required

7. Synovial joint structure
Synovial joint: bones move in joints separated by a cavity filled with synovial fluid
Tendon: Joins muscle to bone, allows muscle to power movement
Ligaments: joins bone-bone, strong, flexible, restrict movement of joint (protection)
Cartilage: protects bones in joints, acts as shock absorber, absorbs synovial fluid.
Synovial membrane: secretes synovial fluid
Synovial fluid: lubricant
Fibrous capsule: encloses joint

8. Action of muscles A joint is a place where two or more bones meet.
Synovial joints are adapted to allow smooth movement between the bones
The elbow is a hinge joint, allowing movement in one plane
Two antagonistic muscles act across the elbow
The biceps contract to flex the arm
The triceps contract to extend the arm

9. Movement of the elbow joint
The contraction of the triceps muscle lowers the arm
extension

10. Movement of the elbow joint
The contractions of the biceps and brachialis muscles raises the lower arm
flexion

11. Movement of the elbow joint
In some movements, both the muscles contract to some degree.
For example, the triceps may contract to act as a steadying force ensuring that the contraction caused by the biceps produces a controlled and steady movement

12. MINI Plenary: individually onto whiteboards
When you contract your biceps muscle what happens to your arm? Flex It holds bones together. Ligament When you contract your triceps what happens to your elbow joint? Extends It attaches muscle to bone Tendon A moveable joint. Synovial

13. Prevents wear and tear in the joint
Prevents wear and tear in the joint. Cartilage/synovial fluid When you straighten your leg what happens to your knee joint? Extends Must be passively stretched to allow movement. Antagonistic Can be damaged with overuse of a joint. Cartilage, tendon, ligament Complete this sentence: ‘When you bend your arm your biceps muscle is contracting and your triceps is relaxing. The muscles are …’

14. Neuromuscular junction
This is a specialised synapse between the end of a motor neurone and the muscle fibre membrane adjacent to it
The end of the motor neurone is often referred to as an end plate or motor end plate
In pairs verbally: Compare the arrival of a nerve impulse at a synapse to a neuromuscular junction

17. Neuromuscular junction
Synapse
Neuromuscular junction
An action potential/impulse arrives at the presynaptic knob.
The presynaptic membrane depolarises
Calcium ion channels in the membrane open.
Calcium ions enter the presynaptic knob these cause the
Vesicles holding neurotransmitter fuse with the presynaptic membrane.
Neurotransmitter/ acetylcholine is released into the synaptic cleft.
Neurotransmitter diffuses across the synaptic cleft.
Neurotransmitter binds to specific receptors on the postsynaptic membrane.
Protein channels on the postsynaptic membrane open.
Sodium ions enter the postsynaptic neurone.
The postsynaptic membrane is depolarised.
An action potential is triggered in the postsynaptic neurone.
Acetylcholinesterase breaks down acetylcholine
An action potential/impulse arrives at the neuromuscular junction Vesicles holding neurotransmitter fuse with the presynaptic membrane. Neurotransmitter diffuses across the synaptic cleft. Neurotransmitter binds to specific receptors on the muscle fibre membrane (sarcolemma) called the motor end plate Depolarisation travels down T system tubules This depolarisation leads to release of calcium ions from the sarcoplasmic reticulum The calcium ions bind to proteins in the muscle that lead to contraction Acetylcholinesterase breaks down acetylcholine so muscle contraction only occurs when impulses arrive continuously

18. NOW:
Compare and contrast the action of synapses and neuromuscular junctions

19. Neuromuscular junction
Compare and contrast the features of synapses and neuromuscular junctions
Synapse
Neuromuscular junction
Neurone to neurone
Neurone to skeletal muscle cell
Post synaptic stimulation leads to action potential in post synaptic neurone: muscle/gland
Post synaptic stimulation leads to depolarisation of sarcolemma, muscle contraction
Excitatory/inhibitory
Always excitatory
Synaptic knob is smooth and rounded
End plate has brushed appearance: microvilli and is flattened up to muscle fibre
Neurotransmitter in vesicles in presynaptic cytoplasm
Vesicles release neurotransmitter into cleft on stimulation: synaptic cleft
Vesicles release neurotransmitter into cleft on stimulation: neuromuscular cleft

20. Neuromuscular junction
Compare and contrast the features of synapses and neuromuscular junctions
Synapse
Neuromuscular junction
Neurotransmitter diffuses across synaptic cleft and binds to post synaptic receptor
Neurotransmitter diffuses across synaptic cleft and binds to post synaptic receptor: sarcolemma
Binding of neurotransmitter results in opening of sodium channels and depolarisation of the post synaptic membrane
Binding of neurotransmitter results in opening of sodium channels and depolarisation of the post synaptic membrane: T-system tubules
Enzymes present to breakdown neurotransmitter to avoid continual stimulation of postsynaptic membrane.
Enzymes present to breakdown neurotransmitter to avoid continual stimulation of postsynaptic membrane. And muscle contraction

21. Exam question
8 marks
QWC!