Sensory and Motor Mechanisms pt. 3

Neural Control of Muscle Tension

• 2 mechanisms graded contractions of whole muscles– varying the number of fibers that contract• Recruitment of motor units to activate

– varying the rate at which fibers are stimulated• Twitches tetanus (smooth, sustained contraction)

– Connected via tendons and connective tissues

Motor units in a vertebrate skeletal muscle

REVIEW!!!• Know these for the AP:• Know the neuron • Neurons with myelin

sheath white matter.• Neurons without myelin

sheath gray matter.• Myelin sheath speeds up

the transmission white matter is faster than gray matter

• Electrical impulses are sent down the axon

REVIEW! (cont’d)• The neuron’s resting potential is -

70mV• Na+ rushes back… fires Action

potential • A neuron cannot fire during the

absolute refractory period• In order for an impulse to be fired it

much reach the threshold (-55 mV)• Depolarization- Na+ Channels open• Repolarization- K+ Channels open• Calcium:

– Too little Ca+ spasms– Too much Ca+ neuron is hard to

fire

KNOW THIS TOO!