Neuromuscular Control of Movement

Organization of Brain Motor Centers

The -Motor Neuron Innervates skeletal muscle Receives input from higher centers Receives sensory input from muscle stretch and tension receptors

Motor Unit Schwann cells, cell body, dentrites, “splintering,” nodes of ranvier, integrate signals from above and below, axon hillock, myelin sheets

The -Motor Neuron All or none Size principle Once you reach threshold an action potential is initiated. EPSP/IPSP Size principle

Motor Unit

Motor Unit

Motor Unit The ratio of nerves to muscle fiber is specific to a motor unit and defined by the task. Fine movements (focusing eyes) Gross movements (muscles involved in jumping)

Motor Unit

Motor Unit

Muscle Recruitment Training In the lab!

Motor Unit Stim Freq Large Motor Unit, Brief Contraction Time Small Motor Unit, Long Contraction Time Motor units with brief contraction times (larger units) require a higher stimulating frequency to produce tetanus than do smaller slow-twitch units. In Fig-13 a large and small motor unit from the gastrocnemius of the cat were stimulated repeatedly at 5, 10, 20,50, and 100 stimuli per second. Notice that the large unit in column A showed little tetanus until the frequency reached 20 per second and didn't develop maximum tension until the frequency reached 100 per second. By comparison, the small motor unit in column B began to tetanize at the relatively low frequency of 10 per second and was nearly maximal at 20 per second. Column C shows the response of a soleus motor unit similar in size to the small gastrocnemius motor unit in column B. Remember that most of the motor units in the gastrocnemius muscle have shorter contraction times than most of the soleus units. It is not surprising to find that the average frequency required for tetanization of the gastrocnemius motor units is greater than we find in the soleus motor units.

Neuromuscular Junction

Neurodengerative disorder. David Rabin. Steven Hawking. Jason Becker

Muscle Sensors Allow for fine control and adjustments of muscle movements. Protect musculoskeletal system from injury.

Fine Control of Motor Movements

Muscle Spindle

Golgi Tendon Organ

Chemical Feedback Control of Breathing

“Muscle Memory”

“Muscle Memory”

“Muscle Memory”

“Muscle Memory” is a form of Neural Memory

Spinal Cord Autonomy

Nerve determines Muscle Characteristics

Nerve determines Muscle Characteristics F S F Sc Fc mitochondrial  -glycerolphosphate-dehydrogenase

Nerve determines Muscle Characteristics Stimulation Frequency Soleus by FDL Nerve S F S F Soleus by Soleus Nerve Sc Fc FDL by Soleus Nerve FDL by FDL Nerve mitochondrial  -glycerolphosphate-dehydrogenase

Training the Motor Unit?