Unit 3: Lecture 17 Somatic Nervous System

Decussation

Crossing white matter tracts in the brainstem or spinal cord

Neurons from the left side of the brains travels across to the right side effectors

Neural Pools

Can have 1000s of interneurons

takes one piece of info to multiple effectors

takes many pieces of info to one specific area

Diverging Circuit

Motor neurons

upper neurons send off to multiple lower motor neurons

increase innervation to effectors at the same time

Converging Circuit

Sensory Neurons

Multiple Neurons sending to one neuron

Spatial Summation

Delivers IPSP and EPSP

Sight, Hearing, Balance

Serial Circuit

Sensory Pathways

1 presynaptic to 1 postsynaptic neuron

Touch/pain

Parallel Circuit

Similar to diverging

Multiple pools move signals at the same time

Ex: Walking

Reverberating Circuit

Positive Feedback Loops

First neurons transmit to a second neuron to another neuron AND circles back to the first

Ex: levels of consciousness, keeping yourself awake

Somatic Sensory Pathways

Ascending Tracts

Descending Tracts

Ascending Tracts

1st order neuron

2nd order neuron

3rd order neurons

1st order neurons

neurons in posterior root

2nd order neurons

Interneurons from spinal cord to brain

3rd order neurons

Brain to motor pathways

Descending Tracts

Upper Motor neuron

Lower motor neuron

Upper Motor Neuron

Brain to anterior horn of spinal cord

Lower Motor Neuron

Anterior root to the effector

Effectors=Skeletal Muscle