Lecture 25- Spinal Cord Structure and Reflexes Flashcards
Is the Posterior Dorsal Horn sensory or motor?
Sensory
Is the Posterior Dorsal Root sensory or motor?
Sensory
Is the Anterior Ventral Horn sensory or motor?
Motor
Is the Anterior Ventral Root sensory or motor?
Motor
Does the horn go to CNS or PNS?
CNS
Does the root go to CNS or PNS?
PNS
How many pairs of cervical nerves are there?
12
How many pairs of spinal nerves are there?
31
What is a ganglion?
Collection of neural cell bodies in the PNS
What is a nucleus?
Collection of neural cell bodies in the CNS
What are interneurons?
Tiny neurons only found in the CNS that participate in reflex circuits
What are reflexes?
Involuntary autonomic movement the body does unconsciously in response to a stimuli
Where is all the information processing done?
Spinal cord
What are the short steps for a reflex arc when touching a hot stove?
- Touch hot stove
- Primary sensory afferent (towards CNS) communicate to interneuron
- Interneuron communicates to lower motor neuron
- Lower motor neuron moves the muscles
- Hand is pulled away
What type of arc is most common?
Reflex Arc
Which direction does Posterior/Dorsal go?
Towards the back
Which direction does Anterior/Ventral go?
Towards the belly
What does the myotatic stretch reflex not have that the reflex arc does?
Interneurons
Which is faster; reflex arc or myotatic stretch reflex?
Myotatic Stretch Reflex
Highly myelinated
What are the basic steps for a myotatic stretch reflex?
- Patellar tendon tapped making quads stretch
- Primary sensory afferent stretch receptor sends action potential which propagates in periphery (Dorsal Post Root ganglion)
- Synapses directly onto the LMN
- Releases NT and activates the LMN
In the patellar stretch reflex, which part of the body is excited and inhibited?
Quads=excitatory LMN
Hamstrings=Inhibitory LMN
What region of the spinal cord are the lower motor neurons located in?
Ventral/Anterior Horn
What is special/significant about the spinal nerve?
Contains both Primary Sensory Afferent and Efferent neurons
What does the Primary Sensory Afferent release?
Neurotransmitter: Glutamate
When the action potentials reach threshold, what does the LMN innervate?
Muscle
What region does the myotatic stretch action potential propagate in the periphery?
Dorsal-Posterior Root Ganglion
True or False: The primary sensory afferent neuron must cross the demarcation line in the myotatic stretch reflex
True
Goes from Posterior-Dorsal Horn in CNS to Anterior-Ventral Horn
What region do the lower motor neurons leave the CNS?
Anterior-Ventral Root
What does the excitatory LMN do?
The stimulated LMN will release acetylcholine onto the quadricep causing muscle contraction.
What does the inhibitory interneuron do?
The inhibitory interneuron will form another synapse in the ventral horn with a LMN that innervates the muscle group that opposes the quad
What is Reciprocal inhibition?
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)
