20. Pathways

Question 1

Types of pathways and how relayed?

Answer 1

Ascending pathway and descending pathway
Pathways are relayed by several neurons

Question 2

Characteristics of ascending pathway

Answer 2

Carry sensory information to brain
Travel through ascending tracts in spinal cord

Question 3

Characteristics of descending pathway

Answer 3

Carry motor information from brain to targets
Travel through descending tracts in spinal cord

Question 4

Funiculi

Answer 4

Functionally distinct regions of white matter in spinal cord
Each contain multiple tracts

Question 5

Types of funiculi

Answer 5

Dorsal (posterior) funiculus
Lateral funiculus
Ventral (anterior) funiculus

Question 6

Characteristics of sensory pathways

Answer 6

3 major somatosensory pathways
Utilize 2-3 neurons in a series to transmit information to brain
Called primary, secondary, and tertiary neurons

Question 7

Types of somatosensory pathways

Answer 7

Posterior funiculus-medial lemniscal pathway
Spinothalamic pathway
Spinocerebellar pathway

Question 8

Function of spinocerebellar pathway

Answer 8

Relay proprioception from limbs and trunk
Cerebellum uses information to coordinate ipsilateral body movements

Question 9

Neurons locations of spinocerebellar pathway

Answer 9

Cell bodies of secondary neurons in dorsal horn of SC and axons ascend in lateral funiculus
Secondary neuron terminates on cerebellum
No tertiary neuron

Question 10

Function of posterior-medial lemniscal pathway

Answer 10

Carries information on fine touch, pressure, conscious proprioception

Question 11

Neuron locations of posterior funiculus-medial lemniscal pathway

Answer 11

Primary neuron ascends in posterior funiculus
Primary neuron synapses with secondary neuron in medulla oblongata
Secondary neuron decussates in medulla (medial lemniscal tract) and travels to thalamus
Tertiary neuron in thalamus sends axon to post central gyrus (primary somatosensory cortex)

Question 12

Function of anterolateral spinothalamic pathway

Answer 12

Carries information on pain, temp, pressure, non-discriminative touch (unpleasant sensation)

Question 13

Neuron locations in anterolateral spinothalamic pathway

Answer 13

Primary neuron synapse in dorsal horn
Secondary neuron decussates and ascends lateral or ventral funiculi to thalamus
Tertiary neuron terminates on primary somatosensory cortex (post central gyrus)

Question 14

Characteristics of motor pathways

Answer 14

Originate in cerebral cortex or cerebral nuclei and descend from brain
At least 2 neurons in pathway (upper motor neuron and lower motor neuron)
UMN synapses with LMN directly or with interneurons
Direct and indirect pathways

Question 15

Direct pathways of motor pathways

Answer 15

Through pyramidal tracts, precise voluntary movement

Question 16

Indirect pathways of motor pathways

Answer 16

Subcritical motor nuclei, subconscious or coarse movement

Question 17

Function of corticospinal tract

Answer 17

Control precise, skilled voluntary movement (skeletal muscle)

Question 18

Neuron locations of corticospinal tract

Answer 18

UMN originates in pre-central gyrus (primary motor cortex)
Decussates at medulla into lateral CS tract and spinal cord into ventral CS tract
LMN originates in ventral horn of spinal cord