Lecture Quiz 5 (L12-13)

Motor control

Somatic Nervous System

• voluntary

• innervates skeletal muscle

• 1 efferent neuron

• Acetylcholine

  • Neurotransmitter that acts synapse between muscle and neuron

• ALWAYS EXCITATORY

Autonomic Nervous System

• involuntary

• innervates internal organs

  • example: cardiac muscle, smooth muscle, glands

• 2 neurons connect CNS

• NE / Epinephrine is used as neurotransmitter

  • OR Acetylcholine for PARASYMPATHETIC

• can be excitatory or inhibitory

  • example:

    • NE speeds up heart rate (sympathetic)

    • Acetylcholine lowers heart rate (parasympathetic)

Somatic Motor Control - Initiation

• Brain has to be involved

• Descending neurons

• TWO MOTOR NEURON CHAIN (1 EFFERENT NEURON)

To initiate voluntary movement:

• signals are sent to descending neurons from the primary motor cortex and then to the efferent motor neuron in the ventral horn of spinal cord

• primary motor cortex → descending neuron → ventral horn → efferent motor neuron → skeletal muscle

Motor (Descending) Pathways for Somatic Motor Control

• Decussation occurs in the brainstem or spinal cord

• Are two-neuron circuits from Primary motor cortex to the muscle

• Synapse in the spinal cord

Somatic Motor Control - Pathway

The cerebellum calculates and refines the details of a movement. It then sends this signal to the motor cortex. The motor cortex sends the final command down the spinal cord to the muscle to cause movement.

Somatic reflexes

Golgi tendon organ and muscle spindle

Stretch Reflex - Steps

Knee-jerk reflex

Stretch reflex - Maintaining Contractions

Tendon Reflex

Tendon Reflex - Protection

Voluntary movements requre coordination from middle and higher level brain regions