Test 3 Flashcards
The afferent neuron is _____ neuron in the sensory system
1st order
Where does the afferent (1st order neuron) enter the CNS?
At the dorsal horn
Efferent neurons are ____, which cell bodies are in the anterior horn and it’s axon is in the _____. It’s role is to innervate its motor unit.
- Alpha
- peripheral nervous system
Stretch reflex is monosynaptic meaning…
It only has 2 neurons in its reflex arc
What is the purpose of the stretch reflex?
To protect the muscle belly from overstretch injury
Reflex arc of stretch reflex is…
1a -> a (alpha motor neuron)
1a -> a synapse causes ____
Excititation
What is 1a releasing toward a during stretch reflex arc?
Acetylcholine
Muscle stretch reflex arc: the stretch of the muscle spindle causes reflex contraction
What is the purpose of GTO reflex?
To protect the tendon from overstretch injury
What is the GTO reflex arc?
1b (sensory neuron) -> interneuron -> a (alpha motor neuron)
What does the interneuron of the gto reflex arc release into its synapse with a (alpha motor neuron)?
An inhibitory neurotransmitter
1b release ____ towards the interneuron which activates it. The interneuron releases _____, which is inhibitory toward a
- Acetylcholine
- Gaba
Simple inverse stretch reflex arc: the stretch of Golgi tendon organ causes reflex inhibition (relaxation)
Reciprocal inhibition: 1a synapses with the interneuron for the reciprocal inhibition reflex. When 1a of a muscle is activated by stretch in addition to initiating stretch reflex response it also activates a _____in the partner muscle.
- relaxation response
These internal muscle fibres, _____, will add to the stretch detected by 1a if they shorten or reduce the stretch detected by 1a if they are relaxed.
- intrafusal fibres
The efferent neurons that innervate the intrafusal fibres which cell bodies are in the anterior horn…
Y motor neurons
What is spasticity?
Muscle hypertonia as a result of exaggerated, dysregulated reflex responses.
Spasticity: the ability of the hmc to exert their balance of excitation and inhibition is compromised by some type of upper motor neuron injury or disease caused damage.
Spasticity typically results from____ lesions
White matter (where myelin is)
Spasticity vs Rigidity:
Which is caused by white matter lesions typically in the the pyramidal tract (i.e upper motor neurons)
- brain injury
- SC compression
- Motor neuron disease
Spasticity
[rigidity is typically seen in extrapyramidal lesions i.e parkinson’s]
Spasticity vs Rigidity:
Which has increased muscle tone even at rest and is usually present during PROM?
Rigidity
[spasticity generally only occurs during muscle stretch and usually accompanied by increased tendon reflexes and a Babinskis’s response.
Spasticity vs Rigidity:
Which has more resistance in one direction than the other and more tone in initial part of movement?
Spasticity
[Rigidity has the same resistance in all directions and affects all mm surrounding a particular joint equally]
Spasticity vs Rigidity:
Which is velocity dependent. And more rapid movement triggers a stronger involuntary contraction or “catch” of affected muscles.
Spasticity
[ Rigidity is not velocity dependent and does not vary with speed of movement of m groups involved]
The spinal cord runs from the ____ to _____
- The base of the skull
- L1/L2
List the meninges in order from outer to most inner
Dura Mater, Arachnoid Mater, Pia Mater
The Spinal vertebrae
__ vertebrae
__ cervical
__ Thoracic
__ Lumbar
__ Sacral
__ cocygeal
- 33
- 7
- 12
- 5
- 5
- 4
Enlargements at the vertebral bodies exist at ___ as well as from ___
- C5 - T1
- L2 - S2
This is because these areas have a lot of nerves coming from them. They are enlarged to protect these nerves which receive a lot of information.
Right and Left Motor output nerve rootlets branch out _____
- ventrally (anteriorly)
Right and Left sensory (input) nerve rootlets branch____
Dorsally (posteriorly)
Mixed motor and sensory nerves are…
Spinal nerves. Made up of ventral and dorsal roots.
How many pairs of spinal nerves are there?
___ cervical
___ thoracic
___ lumbar
___ sacral
___ coccygeal
- 31 pairs
- 8
- 12
- 5
- 5
-1
Where does the spinal cord end in adults? What does this form?
- L1/L2
- Conus Medullaris
Which spine has spinal nerves exit above the corresponding vertebra?
- The cervical spine
(Spinal nerves in the Thoracic, Lumbar, Sacral and coccygeal spines exit below their corresponding vertebra)
Central grey matter contains…
Neuronal cell bodies and synapses
Peripheral white matter contains…
Ascending Sensory (afferent signals) and Descending Motor (efferent signals) pathways
Interneurons determine _______ of spinal cord
- reflex response (spinal reflexes)
_____ pathways usually start with “spino-“ and end w/ the name of the brain region where they first synapse
- ascending sensory
What is the signal transmitted by the Anterior Spinothalamic Tract?
Crude touch (non discriminative)
What is the signal transmitted by the Lateral Spinothalamic tract?
Pain and Temp
What is the signal transmitted by the Dorsal columns?
Discriminative touch, vibration, conscious proprioception
What is the signal transmitted by the spinocerebellar tract?
Unconcious proprioception
Which ascending tracts are located in the lateral white matter?
Lateral Spinothalamic tract & Spinocerebellar tract
Which tracts ascend contralaterally?
Anterior Spinothalamic and Lateral Spinothalamic
Which tracts ascend ipsilaterally?
Dorsal column and Spinocerebellar
Which ascending tracts decussate immediately upon entry into the SC?
Anterior Spinothalamic and Lateral Spinothalamic
Where does the dorsal column tract decussate?
The Brain stem (medulla)
Where does the spinocerebellar tract decussate?
It does not cross over
Deacending motor pathways begin with the region of the brain that give rise to fibres and end with the suffix “-spinal”
What is the signal transmitted by the corticospinal a.k.a Pyramidal tracts?
Voluntary Skeletal muscles
What is the signal transmitted by extra-pyramidal tracts?
Involuntary skeletal (dampens erratic motions, maintains muscle tone)
Where is the extra-pyramidal tract located in the SC?
Lateral white matter
The Corticospinal tract (a.k.a pyramidal) is located ___ in lateral white matter & ___ in anterior white matter of the SC
- 80%
- 20%
Does the corticospinal tract descend the SC contralaterally or ipsilateral?
- both
Does the extra pyramidal tract descend the SC contralaterally or ipsilaterally?
Ipsilateral
Where does the corticospinal tract decussate?
At the brainstem & at spinal level
Where does the extra-pyramidal tract decussate?
At spinal level
At which vertebral levels do SCIs occur more frequently?
- c5 to c7
- T10 - T12
- L1 - L2
When are secondary injuries reversible?
4 to 6 hours after the injury
Injured neurons in the SC will release ____ which when present in large concentrations is toxic to other neurons
- glutamate
How long can neurogenic shock lasts?
7 - 10 days
Occurs following SC innuries only
- spinal shock
