Neuromechanics

• Electrical signals • for communication between periphery and brain • must be generated by a stimulus • must be propagated down an axon • must be transmitted to next cell in line

Afferent neurones- carry information from sensory receptors (skin) to the central nervous system (cell bodies located outside the spinal cord and along the axon) Efferent neurones- carry motor information away from the central nervous system/brain to the muscles and glands to initiate an action. (Cell body is a the end, and inside spinal cord)

Spinal cord makes a decision instead of the brain

• cerebral cortex initiates nervous command. • lower nervous centres process commands, interact with other areas and process Afferent (sensory) feedback. • feedback used to modulate and correct neural commands • a reflex does not require any thought input.

Relay neurones are found between sensory and motor neurones (in the brain and spinal cord) and allow sensory and motor neurones to communicate.

• differences in electrical potential • high energy electrons and low energy electrons cause potential energy difference

Movement down the concentration gradient (chemical force)

The myelin sheath is a greatly extended and modified plasma membrane wrapped around the nerve axon in a spiral fashion. It allows electrical impulses to transmit quickly and efficiently along the nerve cells.

A periodic gap in the myelin sheath on the axon of certain neurones that serves to facilitate the rapid conduction of nerve impulses (recharge the action potential that runs along the axon)

Describes the way an electrical impulse skips from node to node down the full length of an axon. Myelin speeds up propagation: - fatty sheath around axon - not continuous (nodes of ranvier) - multiple sclerosis - axon diameter (larger faster)

• resting membrane potential, maintained by sodium-potassium pumps. • depolarisation, Na+ channels open for Na+ to move in (depolarising it) • overshoot. Na+ Channels close and K+ channels open to re-polarise the cell. • Re-polarisation. K+ moves out of the cell. • Afterhyperpolarisation. Additional K+ moves out of cell, hyperpolarising it. • cell returns to resting membrane potential.

• during depolarisation • neurone unable to respond to another stimulus • Na+ channels already open, can’t open more.

• during re-polarisation • neuron responds only to a very strong stimulus • K+ channels open (Na+ closed could open again)

Muscle fascicles- muscle fibres bundled as a unit. Muscle fibres- consists of a single muscle cell. Myofibril- muscle cell basic rod like unit (within fibre) Filaments- within the myofibril Proteins

Skeletal muscle Cardiac muscle Smooth muscle

• striated • elongated cells • multinucleated cells • voluntary

• striated • branched cells • 1-3 central nuclei • involuntary

• nonstriated • single central nucleus • involuntary

P-CSA- area of the cross section of a muscle perpendicular to its fibres A-CSA- area of the cross section of a muscle perpendicular to its longitudinal axis

• the angle between the longitudinal axis of the whole muscle and it’s fibres • in some cases the aponeurosis runs nearly the whole length of the muscle • muscle fibres can be relatively short, but run at a large angle to the aponeurosis.

• direction of force therefore is not the same as the direction of pull • this is offset by a larger physiological cross-sectional area • pennation angle alters the relationship between shortening of the fibres and the shortening of the whole muscle. • muscles with greater angles of pennation have more sarcomeres in parallel so can generate more force.

• tough coat that covers the entire surface of the muscle belly. • separate muscles from surrounding tissues and organs. • connected to deep fascia

• cover of the muscle bundle • loose connective tissue • intramuscular nerve branches • arterioles, venules • intramuscular nerve branches

• surrounds individual muscle fibres • pathway ➡️ blood vessels and nerves