Lecture 9 The Spinal Cord and the Periphery

Question 1

Where does the axons of the sensory fibres enter in the spinal cord

Answer 1

Dorsal root into the dorsal horn

Question 2

Where does the axons of the motor fibres exit the spinal cord

Answer 2

Ventral root from the ventral horn

Question 3

What are the 3 columns of the white matter

Answer 3

Posterior
Lateral
Anterior

Question 4

Ascending pathways are___

Answer 4

Sensory

Question 5

Descending pathways are___

Answer 5

Motor

Question 6

Name 3 important tracts

Answer 6

Corticospinal/Pyramidal Tract
Posterior/dorsal column
Lateral spinothalmic tracts

Question 7

What is the purpose of Corticospinal/Pyramidal Tract

Answer 7

Carries motor impulses from motor cortex to skeletal muscle

Question 8

What is the purpose of the posterior/dorsal column

Answer 8

carries touch, tactile localisation, vibration sense, proprioception

Question 9

What is the purpose of the lateral spirothalmic tract

Answer 9

Pain and temperature

Question 10

Where does the corticospinal/pyramidal tract pathway Strat from

Answer 10

Primary motor cortex (area 4)

Question 11

Define Corticobulbar fibres

Answer 11

Cross before the medulla

Question 12

Define corticospinal fibres

Answer 12

Cross at decussation of pyramids at medulla

Question 13

How many neurons are between the peripheral receptor and the cortes of the posterior/dorsal column

Answer 13

3

Question 14

Where does the 1st neuron of the posterior/dorsal column synapse

Answer 14

With cell body of 2nd neuron at lower part of medulla

Question 15

Where does the 2nd order neuron of the posterior/dorsal column decussate

Answer 15

Medulla to become medial lemniscus and passes through the medulla, pons and midbrain to the thalamus

Question 16

Where does the 3rd neuron in the posterior/dorsal column head through

Answer 16

Starts from thalamus and axons pass through IC and radiate to post central gyrus

Question 17

What area does the posterior/dorsal column end up in, in the cortex

Answer 17

Area 1,2,3

Question 18

Where does the first order neuron of the spinothalamic tract begin and end

Answer 18

Enters into grey matter and ends at the same level

Question 19

What is the path of the second order neuron in the spinothalamic tract

Answer 19

Cross over to reach the lateral area and becomes the lateral spinothalimic tract

Question 20

Where does the 2nd order neuron end in the spinothalamic

Answer 20

Thalamus

Question 21

Where does the 3rd order neuron end in the spinothalamic tract

Answer 21

Begins at thalamus and ends at IC radiation to reach post-central gyrus

Question 22

What is the purpose of the stretch reflex

Answer 22

Important in control of muscle tone and posture (e.g. buckling and almost falling)

Question 23

What is the purpose of the flexor relfex

Answer 23

Prevent injury

Question 24

Why is Inhibitory neuron activated

Answer 24

In stretch reflex joints are controlled by two opposing sets of muscles, extensors and flexors, which must work in synchrony. Thus, when a muscle spindle is stretched and the stretch reflex is activated, the opposing muscle group must be inhibited to prevent it from working against the resulting contraction of the homonymous muscle

Question 25

What motor neuron mediates reflexes

Answer 25

LMN

Question 26

if LMN is not affected in an UMN lesion that causes paralysis what happens to the reflexes

Answer 26

Reflexes are exaggerated

Question 27

What are the consequences of an UMN

Answer 27

Spasticity
Hyper-reflexia
Increased tone

Question 28

What are the consequences of LMN

Answer 28

Flaccidity

Absent reflexes