Sensory and Motor Mechanisms pt. 3

1. Sensory and Motor Mechanisms pt. 3

2. 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

3. Motor units in a vertebrate skeletal muscle

4. 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

5. 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

6. KNOW THIS TOO!