nervous system pathways

Question 1

types of pathways

Answer 1

ascending pathway (sensory)
descending pathway (motor)

Question 2

ascending pathway (sensory)

Answer 2

conducts impulses from general sense receptors into brain

Question 3

ascending pathway has three successive neurons from receptor to cortex

Answer 3

first order neuron
second order neuron
third order neuron

Question 4

first order neuron

Answer 4

receptor to spinal cord (PNS)

Question 5

second order neuron

Answer 5

• interneuron, multipolar (CNS)
• cell body in dorsal horn of spinal cord of medulla (CNS)
• decussates (Crosses over) in spinal cord or medulla

Question 6

third order neuron

Answer 6

• interneuron, multipolar (CNS)

- cell body in thalmus-impulses to postcentral gyrus (sensory cortex) (CNS)

Question 7

axons of 1st or 2nd order neurons from ascending spinal tracts:

Answer 7

1. posterior (dorsal) column pathway/tracts
2. spinothalamic pathway/tracts
3. spinocerebellar pathway/tracts

Question 8

posterior (dorsal) column pathway/tracts

Answer 8

• sensations can be precisely located (touch)

- receptors = free nerve endings, Meissner’s etc

Question 9

spinothalamic pathway/tracts

Answer 9

• non-specific, difficult to localize

- receptors = temperature, pain

Question 10

spinocerebellar pathway/tracts

Answer 10

• ascending tracts from spinal cord to cerebellum
• receptors=proprioceptors
• 2nd order neuron directly to cerebellum (no 3rd order)
• no conscious perception
• no decussation

Question 11

descending pathway (motor)

Answer 11

-conduct impulses from brain to effector

-

Question 12

descending pathway has 2 neuron pathway :

Answer 12

upper motor neuron

lower motor neuron

Question 13

upper motor neuron

Answer 13

(CNS)

• multipolar interneurons
• cell bodies in cortex or brainstem nuclei

Question 14

lower motor neuron

Answer 14

cell bodies in ventral horn (CNS) and axons in PNS

Question 15

axons of upper motor neurons from descending spinal tracts

Answer 15

corticospinal tracts

indirect tracts

Question 16

corticospinal tracts

Answer 16

• cell bodies in cerebral cortex

- tract mainly decussate in medulla

Question 17

indirect tracts

Answer 17

• cell bodies in brainstem nuclei

- receive impulses from motor cortex, basal nuclei, cerebellum