Lecture 25- Spinal Cord Structure and Reflexes

Question 1

Is the Posterior Dorsal Horn sensory or motor?

Answer 1

Sensory

Question 2

Is the Posterior Dorsal Root sensory or motor?

Answer 2

Sensory

Question 3

Is the Anterior Ventral Horn sensory or motor?

Answer 3

Motor

Question 4

Is the Anterior Ventral Root sensory or motor?

Answer 4

Motor

Question 5

Does the horn go to CNS or PNS?

Answer 5

CNS

Question 6

Does the root go to CNS or PNS?

Answer 6

PNS

Question 7

How many pairs of cervical nerves are there?

Answer 7

12

Question 8

How many pairs of spinal nerves are there?

Answer 8

31

Question 9

What is a ganglion?

Answer 9

Collection of neural cell bodies in the PNS

Question 10

What is a nucleus?

Answer 10

Collection of neural cell bodies in the CNS

Question 11

What are interneurons?

Answer 11

Tiny neurons only found in the CNS that participate in reflex circuits

Question 12

What are reflexes?

Answer 12

Involuntary autonomic movement the body does unconsciously in response to a stimuli

Question 13

Where is all the information processing done?

Answer 13

Spinal cord

Question 14

What are the short steps for a reflex arc when touching a hot stove?

Answer 14

1. Touch hot stove
2. Primary sensory afferent (towards CNS) communicate to interneuron
3. Interneuron communicates to lower motor neuron
4. Lower motor neuron moves the muscles
5. Hand is pulled away

Question 15

What type of arc is most common?

Answer 15

Reflex Arc

Question 16

Which direction does Posterior/Dorsal go?

Answer 16

Towards the back

Question 17

Which direction does Anterior/Ventral go?

Answer 17

Towards the belly

Question 18

What does the myotatic stretch reflex not have that the reflex arc does?

Answer 18

Interneurons

Question 19

Which is faster; reflex arc or myotatic stretch reflex?

Answer 19

Myotatic Stretch Reflex

Highly myelinated

Question 20

What are the basic steps for a myotatic stretch reflex?

Answer 20

1. Patellar tendon tapped making quads stretch
2. Primary sensory afferent stretch receptor sends action potential which propagates in periphery (Dorsal Post Root ganglion)
3. Synapses directly onto the LMN
4. Releases NT and activates the LMN

Question 21

In the patellar stretch reflex, which part of the body is excited and inhibited?

Answer 21

Quads=excitatory LMN
Hamstrings=Inhibitory LMN

Question 22

What region of the spinal cord are the lower motor neurons located in?

Answer 22

Ventral/Anterior Horn

Question 23

What is special/significant about the spinal nerve?

Answer 23

Contains both Primary Sensory Afferent and Efferent neurons

Question 24

What does the Primary Sensory Afferent release?

Answer 24

Neurotransmitter: Glutamate

Question 25

When the action potentials reach threshold, what does the LMN innervate?

Answer 25

Muscle

Question 26

What region does the myotatic stretch action potential propagate in the periphery?

Answer 26

Dorsal-Posterior Root Ganglion

Question 27

True or False: The primary sensory afferent neuron must cross the demarcation line in the myotatic stretch reflex

Answer 27

True *Goes from Posterior-Dorsal Horn in CNS to Anterior-Ventral Horn*

Question 28

What region do the lower motor neurons leave the CNS?

Answer 28

Anterior-Ventral Root

Question 29

What does the excitatory LMN do?

Answer 29

The stimulated LMN will release acetylcholine onto the quadricep causing muscle contraction.

Question 30

What does the inhibitory interneuron do?

Answer 30

The inhibitory interneuron will form another synapse in the ventral horn with a LMN that innervates the muscle group that opposes the quad

Question 31

What is Reciprocal inhibition?

Answer 31

Excites muscle contraction in one muscle & inhibit muscle contraction in another muscle; the patellar tendon tap reflex is a classic example of reciprocal inhibition (quads=excite, hammies=inhibit)