Ch 13-15 Flashcards
Why is an understanding of the motor system important for SLPs
Communication is a volitional motor act
Need to understand how it functions normally to know what a deficit is and how to treat it
What makes a movement skilled?
Speech is a skilled movement
It is accurate, efficient, and consistent
Helps motor patterns become more automatic
Reduces variability in errors
Reduces mental and physical effort to act in environment
3 types of muscles in mammals
Striated
Smoooth -in our organs - autonomic system - does not fatigue
Cardiac - consistent, rhythmic function
what type of muscles is used for voluntary movement?
Striated
Which type of muscles requires a great deal of metabolic energy and is susceptible to fatigue
Striated
Motor movement plan/pathway
Brains have intended goal and plan to achieve it
Makes sure action fits the goal so movement is smooth and coordinated (essential for skilled movement)
Send that message from primary motor cortex via UMN which synapse with LMN in brainstem and spinal cord - sends message via LMN to the muscles (CN and spinal nerves) to move them
Where does communication between the LMN and muscles occur?
At the neuromuscular junction (NMJ)
What are LMNs and where do they originate?
Originate on the brainstem and in the ventral gray area of spinal cord. Get information from UMN
Describe the NMJ
It is where the lower motor axon terminal and the muscle fiber meet.
It is a specialized synapse
Synapses with muscle at the motor end plate
Different from other synapses b/c there is a single presynaptic ap to one post-synaptic ap.
It is ONLY excitatory
Neurotransmitter is acetylcholine
What is a motor unit?
The smallest functional unit that the CNS can influence and regulate
Consists of a LMN and the muscle fiber that it innervates
What is the difference between the NMJ and motor unit
NMJ is where axon terminals are meeting muscle cell
The motor unit is the entire motor neuron and all the cells that innervates it - it is the final common pathway
Muscle fiber Innervation
A LMN can innervates multiple muscle fibers, however, a muscle fiber is only innervated by 1 LMN
Why is a muscle fiber innervated by only 1 LMN?
Ensures even a simultaneous effort by entire muscle group that is contracting.
No confusion as to which muscle fiber needs to respond. Directly lined up to help our muscles function simultaneously without recruiting other muscles into the movement
List the 4 systems involved in neuromotor control
Primary and premotor cortex
Basal ganglia
Cerebellum
LMN from brainstem - cranial nerves and spinal nerves
Define Innervation ratio. What is the relationship between Innervation ratio and skilled movement
Small ratio is used for fine motor movement and helps with decreased effort. Key in speech production and communication.
High ratio is less precise motor movement and more force is involved.
Differentiate between direct and indirect systems
Direct - message goes directly from the cortex to the muscle. Involves the primary and premotor cortex and LMN
Indirect - messages go to the body - final common pathway. Coordinating movement and the underlying control of what is happening in the direct motor system. Involves the basal ganglia and cerebellum
Where do UMN fit in
Pathways from cortex to LMN - taking information from primary and premotor cortex and the brainstem to connect with LMN at cranial and spinal nerves
6 descending UMN pathways where do they originate from?
2 from the cortex
4 from the brainstem
Brainstem are less relevant to skilled movements for speech production
Direct pathway from the cerebrum
Direct because they provide a direct link between the motor cortices and LMN
Pathways are: corticospinal and corticobulbar
Where are the cell bodies found for the cst and cbt pathways?
Found in the cortical layer V from pyramidal cells
Areas of the cortex that the cst and cbt pathways originate from
Primary and premotor cortex
Cingulate motor area
Primary sensory area
Posterior parietal cortex
Sensory gives feedback to guide the motor actions
CST course
Originate in primary motor cortex on the precentral gyrus of the frontal lobe
Down through the corona radiata and internal capsule to the crus cerebri at the level of the midbrain
Then pons and decussate at the pyramids of the medulla.
Here they become the lateral and anterior corticospinal tracts
What type of nerves are the LMNs from the CST
Spinal nerves
What is the difference in the decussation of the lateral CST vs. the anterior CST
Proportions are different
Lateral crosses and goes contralateral - 90%
Anterior is Ipsilateral - 10%
