129; Neurological Basis of Movement Flashcards
What is the Peripheral Nervous System?
All of the nerves outside of the brain and the spinal cord; Includes all Cranial Nerves except CN I and CN II
What is an Afferent Neuron?
Neuron conducting signals INTO the CNS
What is an Efferent Neuron?
Neuron conducting signals FROM the CNS
What is a Ganglion?
Collections of neurons (or nuclei of) usually collected outside of the brain
What are the 5 components of the reflex circuit?
- Sensory Receptor
- Afferent path to CNS
- Synapse with the CNS
- Efferent path from CNS
- Effector (muscle)
Describe the Myotatic reflex following a patellar tap
Patellar tap stretches the quadriceps muscle
- Muscle spindles are stretched
- Afferent neurone stimulated (1a afferent)
- Synapse with grey matter in spinal cord
- Direct synapse to excitatory à neuron
- Contraction of Quadriceps muscle (Homonymous muscle)
and
- Synapse with Inhibitory interneuron
- Inhibition of à motor neuron to the heterogymous muscle
What makes the reflex transient?
Recurrent inhibition
Renshaw cell is an inhibitory neuron
- It is excited by the à motor neuron
- Releases glycine back into à motor neuron
- Inhibits firing of à motor neuron
= Negative feedback
Glycine has the inhibitory effect here; the Tetanus toxin inhibits glycine release, which causes prolonged contraction of muscle.
Describe the inverse Myotatic reflex
It provides inhibitory feedback;
Golgi Tendon Organ has a higher threshold than Spindle
- It is activated by prolonged muscle tretch or contraction
- 1b afferent activation
Activation causes inhibition of homonymous muscle
Prevents damage to tendon
(eg, Drop heavy things)
What is the role of ŷ motor neurons?
Maintains tension on the muscle fiber, even following contraction of the muscle that may cause the spindle to become flacid
How do ŷ motor neurons maintain the tension over the spindle?
They stretch each end of the spindle causing contraction;
Set a reference range around which further muscle regulation is established.
Briefly describe à and ŷ motor neurones
à- cause muscle contraction
ŷ- cause spindle contraction
Where do motor neurones originate?
Pyramidal cells of the motor cortex
Describe the course of Motor Neurones through the Corticospinal tract
- Motor neurons originate in the pyramidal cells of the motor cortex
- They descend through the internal capsule
- Cross at ‘decussation of pyramids’ in the medulla
It is the largest descending ract
What are the major Cortical Motor Regions
- Primary Somatosensory Cortex- Parietal
- Pre-motor Area- Frontal
- Supplementalr Motor Area- Frontal
- Posterior Parietal Cortex- Parietal
What are the Main functions of the Primary somatosensory cortex?
- Recieve ascending sensory input from Thalamus
- (sensory homunculus)
- Sends descending fibers to sensory regions to filter irrelevant signals
What are the main functions of the Pre-motor area?
- Located in Frontal lobe
- Involved in planning of intended movements
- Particularly movements requiring visual guidance
What are the main functions of the Supplementary motor area?
- Coordination of voluntary movements
What are the main functions of the Posterior Parietal Cortex?
- Integration of other sensory information
What is Apraxia?
The inability to produce a specific motor event, even though sensory and motor pathways remain intact.
What is Apraxia and indication of?
- Damage to PMC, SMA or PPC
What is the difference between Ideomotor and Ideational Apraxia?
Ideomotor Apraxia
Cannot execute a specific movement upon request; alothough may understand concept, and able to do movement spontaneously
Ideational Apraxia
Unable to conceptualise the movement required
From where does tha Corticospinal tract arise?
Arises from the Cortex
What does the Reticulospinal tract modulate?
Spinal extensor reflexes
What does the Vestinulospinal tract modulate?
Posture & Balance
