Neuromotor Basis For Motor Control Part 2 Flashcards
Grey matter
H shaped central portion
Contains cell bodies and axons
2 horns of spinal cord
Dorsal (posterior) horns
Ventral (anterior) horns
Dorsal horns
Sensory neurons
Ventral horns
Alpha motor neurons (terminated in skeletal muscle)
Interneurons
Function of spinal cord
Reflexive movement
Transmit ascending and descending neural signals
2 types of reflexive movement
Monosynaptic
Polysynaptic
monosynaptic reflex
- 1a afferent
- muscle spindle detects a stretch in the muscle
- direct synapses from sensory to motor neuron of same muscle causes contraction
Polysynaptic reflex
- 1b afferent
- from tendon send signal of change in muscle force
- sensory nerve synapses on interneuron
- interneuron if excitatory can cause contraction of antagonist (withdrawal) or inhibitory and inhibit contraction of same muscle (relaxation)
What is reciprocal inhibition
Relaxation of the antagonist muscle during activity of the agonist
What happens during reciprocal inhibition
Muscle spindle detects change in length
- 1a afferent directly synapses on alpha motor neuron and on inhibitory interneuron
- then synapses with alpha motor neuron of antagonist muscle
Neural pathway of motor
Descending
Neural pathway of sensory neurons
Ascending
2 types of descending motor tracts
Lateral corticospinal tract
Lateral vestibulospinal tract
Lateral corticospinal tract (motor)
- Motor commands send down from motor cortex
- Cross after medulla
- And travel to spinal cord to synapse on motor and interneurons
Very shortened version of motor neural pathway- lateral corticospinal tract
Cortex - medulla - spinal cord- signal to skeletal muscle(s)
Lateral vestibulospinal tract (motor)
- Motor output sent down from lateral vestibular nuclei
- To medulla
- Travels without crossing to spinal cord
- Synapses on motor and interneurons
Shortened version of motor neural pathway - lateral vestibulospinal tract
Brainstem- lateral vestibular nucleus - medulla - spinal cord - signal to skeletal muscle(s)
What are extrapyrimidal tracts
Brainstem pathways
What do the fibers of the extrapyrimidal tracts not do
Cross to other side of body
what are extrapyrimidal tracts involved in
Postural control and control of hand and finger flexion/extension
What does the lateral vestibulospinal tract excite
Antigravity muscles to maintain extension and prevent collapse
What happens when you spin around until feeling dizzy and then stagger around
Have experience over active lateral vestibulospinal tract
2 ascending sensory tracts
Dorsal column tract
Posterior spinocerebellar tract
Dorsal column tract (sensory)
Sensory info from proprioceptors and touch receptors
Sent to spinal cord
Crosses in medulla
Travels to somatosensory cortex via thalamus
What are examples of sensory info from touch receptors
Touch
vibration
Two point discrimination
Shortened version of sensory neural pathway - dorsal column tract
Signal from proprioceptors and touch receptors - spinal cord - medulla - thalamus - cortex
Posterior spinocerebellar tract (sensory)
Sensory info from lower limb proprioceptors
Sent up spinal cord
Does not decussate in medulla
Travels to ipsilateral cerebellum
Shortened version of sensory neural pathway - posterior spinocerebellar tract
Signal from proprioceptors - spinal cord - medulla - cerebellum
Motor unit
An alpha motor neuron and all the skeletal/extrafusal muscle fibers it innervates
Example of motor unit for fine movement
Eye muscles = 1 fiber/motor unti
Example of motor unit for a gross movement
Postural control = up to 700 fibers/motor unti
Amount of contractile force is directly related to what
Number of motor units activated
Recruitment
Process of increasing number of motor units involved
What does recruitment follow
Size principle
What does size = in motor unit recruitment
Motor unit cell body diameter
What is the size principle
Recruit smallest motor units first then systematically increase size of unit recruited until desired force is achieved
3 parts of neural control of voluntary movement that determine motor control
- Perception (detecting visual, auditory, tactile cues)
- Cognition (reaction time, intent)
- Emotion (fear of falling)
Where is the intent located
Higher centers of the cortex
Planning and organization of the required movement occurs where
The middle center of the brain including the sensorimotor cortex, diencephalon, cerebellum, and brainstem
Execution of the movement plan involves
Brainstem, spinal cord, muscle fired and sensory receptors
