The Motor System Flashcards
What is the motor system
-extremely complex system
- includes parts of the motor system that control voluntary movement, allowing thought to be turned into movement
The type of motor speech disorder depends on?
Location & extent of damage to the motor system
Two main components of the motor system?
Central Nervous System & Peripheral Nervous System
The CNS consists of?
The brain and spinal cord
The PNS consists of?
-12 pairs of cranial nerves
-31 pairs of spinal nerves
What is the most complex and important part of the nervous system?
The brain
Function of the brain?
-initiates or controls actions- almost all nervous system activity originates in or is processed by the brain
-Brain sends motor commands
-Brain receives sensory commands and controls cognitive functions
Voluntary motor commands go in what direction
Descending
Away from the CNS
Sensory commands go in what direction
Ascending
Accessing the CNS
Primary divisions of the brain?
- Cerebrum
- Brain stem
- Cerebellum
What is the largest and most prominent part of the brain
The cerebrum
Division of the cerebrum?
-Divided into 2 hemispheres by the longitudinal fissure
-Consists of 4 lobes
What are the primary lobes of the cerebrum
-frontal lobe
-temporal lobe
-parietal lobe
-occipital lobe
What are the 2 additional cerebrum lobes?
-insular lobe
-limbic system
What is the surface of the cerebrum called?
Cerebral cortex
The cerebral cortex is known as ___, why?
Gray matter
It is called this because of its color. Soma’s (or cell bodies) are present in the cerebral cortex, giving it a pinkish-gray color.
Function of the cerebral cortex
Higher order functioning
Responsible for consciousness, thought, and cognitive activities (motor planning, problem solving, sensory perception, and language)
The surface of the cerebrum consists of what?
Sulci, which are the grooves or indentations
Gyri, which are the projections or humps
What are the two main sulci on the cerebrum
Lateral sulcus- separating the frontal lobe from the temporal lobe
Central sulcus- separating the frontal lobe from the parietal lobe
What are the two main gyri on the cerebrum
Precentral gyrus = primary motor cortex = motor strip
Postcentral gyrus = primary sensory cortex = sensory strip
Main function of the primary motor cortex
Sends out motor signals for motor movement
Main function of the primary sensory cortex
Receives all sensory information
Where is the brainstem located?
Between the cerebrum and the spinal cord
What structures make up the brainstem
Midbrain
Pons
Medulla oblongata
Which nerves originate in the brainstem area?
Cranial nerve pairs 3 through 12
What is the attachment point for the brainstem to the cranial nerve?
The cranial nerve nuclei
Function of the brainstem
- passageway for descending and ascending neural tracts traveling between the cerebrum and spinal cord
- controls certain integrative and reflexive actions (such as automatic body functions, respiration, and consciousness)
- conveys motor impulses from the CNS to the articulation muscles (larynx, face, tongue, pharynx, and velum)
Which structure is attached to the back of the brainstem?
Cerebellum
Divisions of the cerebellum
-Divided into two lobes by a fissure (like the cerebrum)
-Vermis is a mass of tissue connecting the two cerebellum lobes
Function of the cerebellum
-coordinates voluntary movements so the muscles contract with correct force at the appropriate times
-Makes neural connections with cerebrum/cerebral cortex and other parts of the brain
The cerebellum regulates …?
-Muscle tone
-maintenance of balance
-coordination of skilled motor movements
-posture
-support
-equilibrium
What is the process to initiating a voluntary movement?
10 steps
-Desire to move
-Association cortex
-Basal ganglia
-Cerebellum
-Thalamus
-Primary Motor Cortex
-Pyramidal system
-Extrapyramidal system
-Cranial and Spinal nerve nuclei
-Neuromuscular junction
What is the first step to produce a voluntary movement?
The desire to move- you must first think and desire to produce any voluntary movement
What structure/system initiates the plan to move? Explain this
The association cortex
Here, the association cortex makes sense of sensory information and creates the initial, rough gross movement plan sequence
The association cortex consists of?
4 areas of corticies
What would be an example of an initial rough gross motor plan sequence
After having the desire to pick up a pencil, recognizing that some amount of grip is needed to pick up the pencil
The basal ganglia consists of what 3 structures?
-caudate nucleus
-putamen
-global pallidus
How does the basal ganglia assist in the production of a voluntary movement
It serves as the link between the association cortex and the PMC
It refines the planning of slow and continuous movement to occur in a controlled manner
If the basal ganglia is impaired what can happen?
-Hyperexcited neurons in the basal ganglia (increased activity) can lead to hypokinetic dysarthria
-Degenerating neurons in the basal ganglia (cell death/less activity) can lead to hyperkinetic dysarthria
Hyperexcited neurons in the basal ganglia is often seen in which neurologic disorder?
Parkinson’s disease
Degenerating neurons in the basal ganglia is often seen in which neurologic disorder?
Huntington’s disease
How does the cerebellum contribute to the production of voluntary movements?
It refines the fine motor control of movements (speed, range, and direction) by maintaining the muscle tone, balance, and coordination of skilled motor movements
How would an impaired cerebellum disrupt movement?
This would cause disturbed fine motor control of movement, which is known as ataxic dysarthria
Impaired speed, range, and/or direction of movements
What is cerebellar ataxia?
Disease in which movement is clumsy and often falling forward (drunklike)
How does the thalamus contribute to the production of voluntary movements?
Integrates sensory impulses from the body into the refined motor impulses & then sends it to the primary motor cortex
The information integrated by the thalamus is often defined as?
Reactionary (sensory) impulses
How does the primary motor cortex contribute to the production of voluntary movements?
It receives the motor impulse, integrates all the information, and adds additional information from the premotor area & supplementary motor area before sending the impulse out
What are the two parts of the primary motor cortex?
-Premotor area
-Supplementary motor area
How to impulses in the primary motor cortex get to other parts of the CNS?
They descend along 2 pathways called the pyramidal system
What is the pyramidal system also called?
Motor tracts
Descending pathways
What impulses go along the pyramidal system?
Impulses that control voluntary fine motor movement
The pyramidal system functions at what level?
Conscious level
What happens when impulses go along the pyramidal system?
Impulses take 2 direct paths here through the medulla oblongata
The bundle of neurons go through the medulla oblongata to either the brainstem or the spinal cord
What is meant by direct activation system?
The pyramidal system is a direct activation system because the impulses take a direct path to reach the brainstem or spinal cord (not making a lot of stops along the way)
What are the tracts of the pyramidal system?
- corticobulbar tract
- corticospinal tract
What is the corticobulbar tract?
-Nerves that go from the cortex to the bulbar area (Medulla oblongata) of the brainstem
-These nerve impulses join/synapse with cranial nerves
What is the corticospinal tract?
-Nerves that go from the cortex to the spinal cord
-These nerve impulses join/synapse with spinal nerves
What type of pattern do the nerves along the corticobulbar tract follow?
Bilateral pattern
This results in bilateral cortical innervation- some impulses are contralateral (control the opposite side) & some are ipsilateral (stay on the same side they control)
What is the pyramidal decussation?
-This happens along the corticospinal tract
-The crossoverpoint at the medulla, resulting in pimarily contralateral activation (meaning impulses cross over at the medulla and control the other side of the body)
If the pyramidal system is impaired, what happens?
Muscle weakness and rapid fatigue (which are characteristics of unilateral upper motor neuron dysarthria)
The extrapyramidal system functions at what level?
Unconscious level
What impulses go along the extrapyramidal system?
-impulses that control postural support needed by fine motor movements
What happens when impulses go along the extrapyramidal system?
-Impulses take 4 different, interconnected, indirect paths with multiple stops
-These impulses DONT originate in the cortex. They descend from other areas and bypass the medulla oblongata and go to the spinal level
-Neurons join/synapse with peripheral nerves
What is meant by indirect activation path?
The extrapyramidal system is an indirect path
Meaning it makes multiple stops
What are the tracts of the extrapyramidal system?
- Rubrospinal tract (nerves from midbrain of the brainstem to the spinal cord)
- Reticulospinal tract (nerves from the reticular formation of the brainstem to the spinal cord)
- Vestibulospinal tract (nerves from vestibular nuclei of the brainstem to the spinal cord)
- Tectospinal tract (nerves from cerebellum to the spinal cord)
How does the extrapyramidal system influence speech
It is not completely understood
But, they have many synaptic connections with the CN’s influencing reflexes and muscle tone. Which means they probably influence some voluntary muscles of the speech mechanism
What is the place where the pyramidal system synapse (join) with nerves?
Nerve Nuclei
-Cranial nerve nuclei- come out of the cranial (Brainstem)
-Spinal nerve nuclei- come out of the spine (spinal cord)
What is the last step of producing a voluntary movement?
Neuromuscular junction
What is the neuromuscular junction
Point where axon of the lower motor neurons make synaptic connections with muscle cells, entering the muscle system, to move the body
What is the innervation ratio?
Neuromuscular junction has an innervation ratio
This is the ability for aa single axon to innervate different numbers of multiple muscle fibers
3 primary components of neurons
-Soma: Cell body
-Dendrites
-Axon (ending in terminal boutons)
What are dendrons
*Receive electrochemical (electricity and chemical nerve signals) impulses from other neurons or sensory organs
*Large branch that extends from the soma/nucleus, branching into smaller dendrites
What are axons
-Whitish single long extension from the soma
-Conducts neural impulses away from the soma and transfers the impulses to muscles, glands, and other neurons
-Terminal boutons (terminal ramifications)- small branches at the end of the axon. Allow one axon to communicate with many additional neurons
-Collaterals- longer branches from the axon, further extending the influence of a neuron to other parts of the nervous system
What is myelin sheath
white, lipid-protein membrane coverings over the length of the axon
it Provides insulation to electrochemical impulses (preventing electrical energy leakage) from the surrounding tissues and fluids which weaken the strength of impulses
What is node of ranvier
breaks/gaps between the myelin sheath coverings which allow the electrical signals to travel longer lengths by jumping from one node to the next (instead of being continuous, which would cause shorter travels)
type of neuron is classified by?
by the type of information carried OR the direction information is carried
What are motor neurons
send neural impulses that cause muscle contractions (movement)
Send motor information away from the CNS (Descending)
What are sensory neurons
carry information related to sensory stimuli to the CNS (Ascending neuron)
What are interneurons
-link neurons with other neurons, forming connections
-Helps in controlling movement
What is the most common type of neuron
Interneurons
What are efferent neurons
impulses EXIT the CNS
What are afferent neurons
impulses ACCESS the CNS
What are other types of nervous system cells (just the names)
-Glial cells (neuroglia)- aid the NS functioning & there are 10x as many glial cells as other cells, making up more than half the NS
-Schwann cells- provide the myelin sheath around axons in the PNS
-Microglia cells- scavenger cells, removing the dead cells and other waste
-Oligodendroglia cells- form myelin around axons in the CNS
-Astrocytes- make up connective tissue within CNS
What are bundles of axons called?
-Tracts- bundles of axons found in the CNS
-Nerves- bundles of axons found in the PNS
Define neurotransmitters
chemical messengers held within the vesicles present in the terminal boutons, until they’re released with charge
What are two important neurotransmitters in the motor system
Two important neurotransmitters in the motor system= acetylcholine & dopamine
Define presynaptic and post synaptic
-Pre-synaptic neurons send a signal to the dendron of the next neuron
-Post-synaptic neurons receive a signal at the dendron
What is an action potential
minimal charge needed to charge the electrical signal
Explain excitatory and inhibitory function of neurotransmitters
excitatory function—they increase the probability of an electrochemical impulse being stimulated in the adjoining neuron. excite the next neuron and move through
inhibitory—they decrease the probability of an impulse occurring in the adjoining neuron. inhibit the next neuron and reduce the strength of the nerve signal
Where did the pyramidal system get its name?
neurons in the PMC descend through the medulla oblongata to the spinal cord, which is like ancient hieroglyphics
What is motor homunculus
neuronal (topographic) representation of the body’s structures represented in an inverted body scheme. It is disproportionate because the size represents the amount of motor commands needed to function (i.e., the bigger the structure, the more motor commands needed to function & vice versa)
Percent of the body controlled contralaterally and ipsilaterally
80% of the body is controlled contralaterally, while 20% of the body is controlled ipsilaterally
What are upper motor neurons?
Upper Motor Neurons are motor fibers WITHIN the CNS (pyramidal + extrapyramidal systems)
What are lower motor neurons
Lower Motor Neurons are motor fibers WITHIN the PNS (cranial and spinal nerves)
The upper motor neurons consist of tracts located where?
Tracts from the cortex to the brainstem & spinal cord
The lower motor neurons consist of tracts located where?
Tracts that come out and synapse with a CN or spinal nerve
An impaired upper motor neuron will lead to?
Unilateral damage will cause unilateral upper motor neuron dysarthria
Bilateral damage will cause spastic dysarthria
An impaired lower motor neuron will lead to?
Flaccid dysarthria
