Spinal Tracts

Question 1

What are the ascending afferent sensory pathways to the brain?

Answer 1

Spinothalamic tract

Posterior while colum-medial lemniscal system

Question 2

What does the spinothalamic tract transmit?

Answer 2

Pain
Temperature
Pressure
Crude touch

Question 3

What does the posterior white column-medial lemniscal system transmit?

Answer 3

Discriminating touch and proprioception

Question 4

How neurons relay ascending afferent sensory to the cerebral cortex?

Answer 4

3 neurons

Question 5

What are the neurons associated with the relay of ascending afferent sensory from the periphery to the cerebral cortex?

Answer 5

• Sensory neuron I - conducts impulses from periphery to the cord or lower brain stem
• sensory neuron II - conducts from cord or lower brain stem to the thalamus
• sensory neuron III - conducts from thalamus to general sensory are of cerebral cortex

Question 6

At which point in the spinal tract does crude awareness of sensations occur?

Answer 6

When impulses reach the thalamus

Question 7

At which point in the spinal tract does discriminating awareness occur?

Answer 7

When impulses reach the cerebral cortex

Question 8

What does it mean for the sensory neuron II in an afferent tract to decussate and what are the implications?

Answer 8

Decussate means to cross - this means that one side of the brain registers mainly sensations from the opposite side of the body

Question 9

Does the principle of divergence apply to mainly sensory impulse or motor impulse?

Answer 9

Sensory impulse

Question 10

What is the principle of divergence?

Answer 10

Each sensory neuron synapses with more than one neuron - impulses diverge and may activate many effectors

Question 11

What are the descending efferent motor pathways to the skeletal muscles?

Answer 11

Pyramidal

Extrapyramidal

Question 12

What are two general principles of descending efferent motor tracts to the skeletal muscles?

Answer 12

Principle of the common path

Principle of Convergence

Question 13

What is the principle of the common path?

Answer 13

Motor neurons in the anterior gray horns are FINAL common path for impulses to skeletal muscles

Question 14

What is the principle of convergence?

Answer 14

Axons from many neurons converge to synapse with EACH anterior motor neuron

Question 15

How are motor pathways from the cerebral cortex to anterior horn cells classified?

Answer 15

Classified according to the way fibers travel to the spinal cord

Question 16

What is the motor tract whose axon fibers travel through the pyramids of the medulla oblongata on their way to the spinal cord?

Answer 16

Pyramidal tract