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!!

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.

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.

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.

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!!

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

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

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

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

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

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

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

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 …’

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

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

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

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

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

Exam question 8 marks QWC!