4 - Voluntary and Involuntary Movement Flashcards
How does your brain synthesize the movements for walking?
It doesn’t. Your spinal cord does.
After entering the cord, every sensory signal travels to two separate destinations:
One branch terminates in the gray matter and is responsible for reflexes
Another branch travels up the afferent tracts
Which two types of neurons make up the gray matter of the spinal cord?
Anterior Motor Neurons
Interneurons
What are the two types of anterior motor neurons?
Alpha motor neurons
Gamma motor neurons
What is the function of aplpha motor neurons?
Excite skeletal muscle groups (motor units)
What is the function of gamma motor neurons?
transmit signals to tiny type A gamma fibers that send signals to intrafusal fibers which make up the middle part of the muscle spindle
These are responsible for maintaining muscle tone
Within each anterior horn, which is more numerous: alpha motor neurons or interneurons?
Interneurons, by a lot
Where are interneurons found?
All gray matter in the spinal cord
What is the function of interneurons?
Most of the signals transmitted to the gray matter pass through interneurons first and are essentially interpreted
interneurons process information and form synapses with eachother and motor neurons
What are Renshaw Cells?
Inhibitory cells between the motor neurons that provide lateral inhibition (increasing specificity of motor actions)
What are propriospinal fibers?
run from one segment of the cord to another
Muscles and tendons are supplied with two types of sensory receptors:
muscles spindles (send information about length and rate of length change)
AND
Golgi tendon organs (transmit information about tendon tension and rate of tension change)
The receptor portion of the muscle spindle is its:
central portion
Compare dynamic and static reflex stretch
Dynamic reflex stretch only last a fraction of a second
the static stretch for a much longer period of time to ensure the muscle stretch remains relatively constant
The stretch reflex prevents ______ of body movements
oscillation and jerkiness
has a damping effect that smooths skeletal muscle movement
What does clonus indicate?
The degree of facilitation of the spinal cord’s reflex system
The golgi tendon organ helps control:
muscle tension
The golgi tendon organ detects _______
The muscle spindle detects _________
muscle tension
muscle length, and changes in muscle length
What happens when a tendon organ is triggered?
Transmitted to the cord
In the cord, a single interneuron inhibits that muscle (and no other muscle)
Continues on to the cerebral cortex
What is the flexor reflex?
almost any type of cutaneous sensory stimulus from a limb is likely to cause the flexor muscles of the limb to contract, thereby withdrawing the limb from the stimulating object
the many patterns of these reflexes in the different areas of the body are called withdrawal reflexes
What is a crossed extensor reflex?
About 0.2 to 0.5 second after a stimulus elicits a flexor reflex in one limb, the opposite limb begins to extend
can push the entire body away from the object that is causing the painful stimulus in the withdrawn limb
What is the positive support reaction?
Pressure on the footpad causes the limb to extend against that pressure
What is the magnet reaction?
Pressure on a specific area of the foot causes extension toward that area
keeps us from falling side to side
What usually causes a local muscle spasm?
Local pain
More than half of the primary motor cortex is responsible for controlling ______ and _______
muscles of the hands
muscles of speech
excitation of a single motor cortex neuron usually:
causes a specific movement rather than a contraction of a specific muscle
(smile rather than orbicularis twitch)
What is the purpose of the premotor cortex?
generates highly complex patterns of movement,
way more complicated than the discrete patterns of the primary cortex
generates a motor image, and then deciphers which movements are needed from the primary cortex and stimulates those areas
When you learn woodworking by watching youtube, what neurons are you using?
Mirror neurons!
What is the function of the supplementary motor area?
Provides bilateral movements rather than unilateral
Works with the premotor cortex to coordinate whole body positioning to support the fine motor movements needed from the primary cortex
Someone whose Broca’s Area is inhibited cannot:
form coherent words, other than an occasional yes or no
What is motor apraxia?
When hand movements become disorganized and uncoordinated
caused by tumors/damage in the premotor area responsible for hand movement
What is another name for the corticospianl tract?
Pyramidal Tract
Most of the pyramidal fibers cross over in the medulla and into ________.
A pass ipsilaterally down the spine via the _______
the lateral corticospinal tract
ventral corticospinal tract
Most of the fibers from the ventral corticospinal tract cross over at:
the neck or upper thorax
The largest, fastest fibers in the pyramidal tract arise from:
giant pyramidal cells called Betz cells
97% of the fibers in the pyramidal tract are _____ and conduct ______
tiny
background tonic signals to motor areas of the cord
What is the red nucleus?
area in the mesencephalon that serves as an alternative path to transmit cortical signals to the spinal cord
Dynamic pyramidal neurons ________
Static pyramidal neurons _________
are excited for a high rate for a short amount of time, causing the initial rapid action
are excited at a low level for a longer amount of time. They maintain the action for as long as it’s needed
Neurons of the red nucleus are primarily _______
whereas neurons of the primary motor cortex are primarily:
dynamic
static
This is probably because the red nucleus sits right next to the cerebellum, which is responsible for rapid movement
How does the brain activate walking, withdrawal, and scratching actions?
By sending a single command signal to the spinal cord, which then sends out signals to all of the muscles involved
If the area pyramidalis is removed, what happens?
All the betz cell fibers are severed
You will maintain voluntary movement, but will lose voluntary fine motor control of the hands
Why does facial droop and limb flaccidity occur with stroke?
Loss of the constant tonic stimulation from the cortex
The brain stem consists of:
Medulla
Pons
Mesencephalon
The pontine reticular nuclei ____
The medullary reticular nuclei _____
excites antigravity muscles
inhibits antigravity muscles
The two nuclei are antagonistic of each other’s actions
What are the antigravity support muscles?
vertebral column
extensor muscles of the limbs
Which two nuclei are responsible for supporting the body against gravity?
Reticular Nuclei
Vestibular Nuclei
What is the specific role of the vestibular nuclei?
selectively controls the excitatory signals to the different antigravity muscles to maintain equilibrium in response to signals from the vestibular apparatus
If you cut the brainstem so that the reticular and vestibular nuclei are severed from the brain, what happens?
Spastic Rigidity
Without signals from the brain, the medullary reticular nuclei is incapable of moderating extension of antigravity muscle groups and they become rigid
_____ is often called the silent area of the brain
cerebellum
What is the cerebellum’s role in motor movement?
compares actual movements depicted by peripheral sensory feedback information with intended movements
Allows for smooth, coordinated movements and helps the brain “plan ahead” in complicated sequential movements
Which part of the cerebellum controls equilibrium?
Flocculonodular lobe
works with the vestibular system
What causes action or intended tremors?
The limbs have momentum, and if the cerebellum isn’t functioning adequately, its damping function doesn’t account for/correct overshoot
Two of the most important symptoms of cerebellar dysfunction are ______ and ______
dysmetria
ataxia
What is dysmetria?
uncoordinated movements that result in ataxia
What is past pointing?
in the absence of the cerebellum, a person ordinarily moves the hand or some other moving part of the body considerably beyond the point of intention.
results from the fact that normally the cerebellum initiates most of the motor signal that turns off a movement after it is begun
if the cerebellum is not available to initiate this motor signal, the movement ordinarily goes beyond the intended mark.
Dysdiadochokinesia
inability to perform rapid alternating movements
Where are the basal ganglia located?
lateral to and surrounding the thalamus
What tasks are effected in the basal ganglia are damaged?
Any complex motor activities:
Writing, cutting with scissors
Many, many subconscious tasks
What ist he function of the basal ganglia?
Changes the timing and scales the intensity of movements
Name two diseases caused by dysfunction in the basal ganglia
Huntington’s
Parkinson’s
Wernicke’s Area involves:
Language Comprehension
Which area is needed for reading?
Angular Gyrus
What causes habituation?
progressive closure of calcium channels in presynaptic neurons, although no one is completely sure why
How does facilitation occur?
Serotonin is released from the sensory terminal
activates cAMP
cAMP blocks K conductance, prolonging firing
prolonged AP causes prolonged opening of presynaptic Ca channels, facilitating the release of more stimulant
Long term memory is caused by _______
Short term memory is caused by ________
structural changes
chemical changes
What structural changes cause long term memory?
- An increase in vesicle release sites for secretion of transmitter substance
- An increase in the number of transmitter vesicles released
- An increase in the number of presynaptic terminals
- Changes in structures of the dendritic spines that permit transmission of stronger signals
For short-term memory to be converted into long-term memory that can be recalled weeks or years later, it must become ________
consolidated
Anything that prevents consolidation is amnestic
What is anterograde amnesia?
Retrograde?
inability to create new long term memories
inability to recall long term memories made previously
