HUMAN PHYSIOLOGY

Highest level is in cerebral cortexControl is mostly feedforward

Middle level is cortex,basal ganglia, thalamus, brain stem, cerebellum Control is mixed feedbackand feedforward

Lowest level is in spinal cord Control is mostly feedback

• •Primary motor cortex
• •Premotorcortices (premotorarea + supplementary motor area)
• •Posterior parietal cortex•Frontal lobe

Intentionand long range planningare accomplished in prefrontal cortex

Short-term planning and movement programming are accomplished in premotorcortices and posterior parietal cortexakamedial

Signals to muscles are organized in and sent from the primary motor cortex

Primary motor cortex has a homunculus very similar to the one on primary somatosensorycortex

Primary motor cortex sends axons directly to the spinal cord

• •The spinal cord receives commands from the cortex and brain stem
• •It contains circuits that can themselves control complicated movements and sequences of movements
• •These circuits use feedback from sensors in muscles, joints and skin to regulate movements
• •The spinal cord contains all of the motor neurons that turn muscles on and off and regulate their force

A muscle spindle senses muscle stretch

A golgitendon organsenses muscle force

on and off and regulate their force

• •Motor neuron action potentials are all or nothing events
• •Transmission to muscle fibers is through a specialized synapse –the neuromuscular junction
• •Every motor neuron action potential causes a motor unit action potential (muap)
• •Motor unit action

big, highly structured, reliable

twitch

Recruitment: action potentials in more motor units

Rate coding: higher frequency of action potentials in each recruited motor unit

• As force increases,smaller motor neuronsare recruited first.
• Smaller motor neuronsgenerally have smalleraxons and muscle fibers

• 1.We move by using muscle cells.
• 2.They are specialized for doing work.
• 3.They use ATP to run molecular motors along protein filaments

Ca++signals regulatory proteins to uncover actinbinding sites

• Ca++binds to regulatory proteins
• to uncover actinbinding sites

Molecular motors use ATP to run along protein filaments