NERVES, MUSCLES AND MOVEMENT

14.1.1     Outline the general organisation of the human nervous system including CNS (brain and spinal cord) and PNS (nerves).

14.1.2     Draw the structure of a motor neuron.

14.1.3     Define resting potential.

14.1.4     Define action potential.

14.1.5     Explain how a nerve impulse passes along a non-myelinated neuron (axon) including the role of Na⁺ ions, K⁺ ions, ion channels, active transport and changes in membrane polarisation.

14.1.6     Explain the principles of synaptic transmission as exemplified by the neuromuscular junction including Ca²⁺ influx and release, diffusion and binding of neurotransmitter, polarisation of the post-synaptic membrane, and subsequent removal of neurotransmitter.

View this video for an overview of the synaptic transmission

Notes: Students should not learn long lists of names of bones, nerves and muscles (except in 14.2.3 where the bones and muscles at the elbow joint only are required).

14.2.1     List the functions of the human skeleton.

14.2.2     Describe the roles of nerves, muscles and bones in producing movement or locomotion.

14.2.3     Draw a diagram of the human elbow joint including cartilage, synovial fluid, tendons, ligaments, named bones and named antagonistic muscles.

14.2.4     Outline the functions of the above named structures of the human elbow joint.

14.2.5     Draw the structure of skeletal muscle as seen in electronmicrographs.

Electronmicrographs are readily available and can be interpreted to show myofibrils and the characteristic patterning of dark and light bands.

14.2.6     Explain how skeletal muscle contracts including the roles of Ca2' ions, troponin, tropomyosin, actin, myosin, cross-bridge formation, movement and breakage, and ATP.

The detailed structure can be deduced so that thin actin filaments and thick myosin filaments interdigitate. Ratchet mechanism depends on bridges forming between thick and thin filaments. The two proteins tropomyosin and troponin act to cover and expose binding sites. Ca²⁺ ions activate troponin molecules and ATP is needed by the contracting muscle.

 

 

 

 

ONE SARCOMERE

 

 

 

 

ACTIN FILAMENT SHOWING TROPONINS AND TROPOMYOSIN

 

 

 

 

MUSCLES RELAXED - NO Ca²⁺ IONS RELEASED.  NO CROSS-BRIDGE FORMATION POSSIBLE

 

 

MUSCLES CONTRACT - Ca²⁺ IONS RELEASED TROPOMYOSIN MOVES ALLOWING CROSS-BRIDGE FORMATION