Chapter 8- The Control of Movement Flashcards
Name the three categories of vertebrate muscles
Smooth muscles
Skeletal or Striated muscles
Cardiac Muscles
What are Smooth Muscles?
Muscles that control digestive systems and other organs
What are Skeletal or Striated Muscles?
Ones that control movement
What are Cardiac Muscles?
Heart muscles, these have properties of both smooth and skeletal muscles
What is the Main Neurotransmitter in the Movement Systems?
Acetylcholine
What is a Neuromuscular Junction?
A Synapse between a motor neuron and muscle fiber
Muscles are composed of…
mainly individual fibers
Each Muscle receives information from how many axons?
Only on, but an axon may innervate many muscle fibers
What are Antagonistic Muscles?
Muscles that are opposing sets. Movement requires contraction of these.
What are the two types of Antagonistic muscles?
Flexor muscles and Extensor muscles
What do flexor muscles do?
flexes/ raises
What do extensor muscles do?
extends/ straightens
What does acetylcholine always do to skeletal muscles on contact?
Excites them
What is Myasthenia Gravis?
An Autoimmune disease in which there is a deficit in Acetylcholine and impairs movement
What are Fast- Twitch Fibers?
Fibers that produce fast contractions and fatigue quickly.
Ex. Running
What are Slow-Twitch Fibers?
Fibers that produce a less vigorous contraction and do not fatigue.
Ex. Lips
Which fibers are Aerobic?
Slow-Twitch fibers are aerobic and use oxygen .
Fast- Twitch fibers are anaerobic and do not use oxygen at the time, which is why they fatigue
What is a Proprioceptor?
receptor that detects position or movement of a part of the body. Fluidity of movement depends on this
What is a Stretch Reflex?
Occurs when muscle proprioceptors detect the stretch and tension of a muscle and send messages to the spinal cord to contract it
What is a Muscle Spindle?
Receptor parallel to the muscle that responds to a stretch, causing a contraction of the muscle
What are Golgi Tendon Organs?
another type of proprioceptor that responds to increases in muscle tension.
located in the tendons at the opposite ends of the muscle
Besides controlling important reflexes, what else do Proprioceptors do?
provide the brain with information. They act as a brake against excessively vigorous contractions by sending an impulse to the spinal cord where the motor neurons are inhibited
What are Reflexes?
Consistent, involuntary, automatic responses to stimuli
True or False. Few behaviors can be classified as purely voluntary or involuntary, reflexive or nonreflexive?
True.
True or False. In some cases, voluntary behavior requires inhibiting an involuntary response?
True.
What is Ballistic movement?
Movements that once they are initiated, cannot be altered or corrected. Ex. Stretch reflex, dilation of pupil.
True or False. Most behaviors are subject to feedback correction?
True. Ex. Wavering of Pitch
Many behaviors consist of rapid sequences of..
Individual movements
What is a Central Pattern Generator?
Neural mechanisms in spinal cord that generate rhythmic patterns of motor output
What is a Motor Program?
A Fixed Sequence of movements that is either learned or built into the nervous system
Ex. Mouse grooming itself, or yawning
Once begin, the sequence is fixed from beginning to end. It is automatic in the sense that thinking or talking about it interferes with the action
The Grasp reflex is…
When you place an object in an infants palm and it closes its hand around it
The Babinski reflex is…
when you run your finger down the sole of a baby’s foot, it extends it’s big toe and fans others
The Rooting reflex is…
Rooting for food, turns head a sucks when cheek is stimulated
What happens to the infant reflexes as we age?
They fade away but the connections remain intact
Why is understanding how the brain controls movement important?
The possibility of curing paralysis
What did Fritsch and Hitzig find concerning the Primary Motor Cortex?
Direct stimulation of the Primary Motor Cortex elicits movement
Where is the Primary Motor Cortex located?
In the Precentral Gyrus in the frontal lobe
True or False. The Motor Cortex sends messages directly to the muscles?
False. Axons from the precentral gyrus connect to the brainstem and spinal cord, which generate impulses that control the muscles
What it the Cerebral Cortex particularly important for?
Complex Actions
When is the Primary Motor Cortex active?
When people “ intend” a movement. It “orders” an outcome
What does the Posterior Parietal Cortex do?
Keeps track of the position of the body relative to the world.
What are the effects of damage to the Posterior Parietal Cortex?
Difficulty is coordinating visual stimulus with movement, which is important to planning movement
What does the Prefrontal Cortex do?
Stores sensory information relevant to a movement and also plans movement according to their probable outcomes.
It responds to lights, noises and other sensory information that can lead to movement.
When is the Premotor Cortex most active?
Immediately before a movement.
Receives information about a target to which the body is directing its movement, as well as information about the body’s current position and posture
What is the Supplementary Motor Cortex?
with the prefrontal cortex, it is important for planning and organizing a rapid sequence of movements in a particular order.
Active seconds before the movement, inhibitory in necessity
What are Mirror Neurons?
Neurons that are active both during preparation for a movement and while watching someone else perform that same or similar movement. May be important for understanding, imitating and identifying other people
The Conscious decision to move and the movement itself occur…
at two different times
Your motor cortex produces a readiness potential before any voluntary movement when?
at an average of at least 500ms before a movement
True or False. We become conscious of the decision to move after the process has already begun?
True. Voluntary decisions are at first unconscious
Messages from the brain and spinal cord must reach where?
The medulla and spinal cord, which control the muscles
What are Corticospinal Tracts?
Paths from Cerebral Cortex to the spinal cord.
Name the two Corticospinal Tracts
1) Lateral Corticospinal tract
2) Medial Corticospinal tract
What is the Lateral Corticospinal Tract?
set of axons from the primary motor cortex, surrounding areas and the red nucleus .
Controls movement in peripheral areas ( hand and feet)
Red nucleus- midbrain area in which output is mainly to arm muscles
What is the Medial Corticospinal Tract?
Includes axons from many parts of Cerebral Cortex and also axons from the midbrain tectum, reticular formation and the vestibular nucleus.
What is the Vestibular Nucleus?
A brain area that receives information from Vestibular senses (useful for walking, turning, bending , standing and siting)
axons go to both sides of spinal cord and allows control of neck, shoulders and trunk
Concerning Movement, what is the Cerebellum important for?
Balance and Coordination. Contains 70% of all neurons in the nervous system.
Is also important for establishment of mew motor programs that allow the execution of a sequence of actions as a whole .
Critical for certain aspects of attention shifting
What is one effect of Cerebellar damage?
Trouble with rapid movements requiring aim/timing. Ex. clapping hands, speaking and writing
Where does the Cerebellum receive information from?
From Spinal Cord and all sensory systems, Cerebral cortex and sends it to the Cerebellar cortex which is the surface of the Cerebellum
What three steps does the Finger-to-nose test consist of?
It tests the Cerebellum and is
1) a Rapid Ballistic Movement
2) Goes almost to the nose
3) Actually touches the nose
What part of the brain does alcohol affect?
The Cerebellum
The Cerebellum receives input from spinal cord, each sensory system by way of the cranial nerve nuclei and from the cerebral cortex eventually reaching the…
Cerebellar Cortex
The neurons in the cerebellar cortex are organized in…
Precise Geometric Patterns
What are Purkinje cells?
Flat cells in sequential planes
What are Parallel fibers?
axons parallel to one another and perpendicular to the planes of the Purkinje cells.
Regular pattern allows outputs of well-controlled duration
The greater the number of excited Purkinje cells…
the greater their collective duration of response
What is the 3 steps process of Purkinje cells?
1) Action potentials in parallel fibers excite on Purkinje cell after another
2) each Purkinje cell transmits an inhibitory message to cells in the nuclei of the cerebellum and vestibular nuclei in the brainstem
3) Cerebellum and Vestibular nuclei sends information to the midbrain and the thalamus
What is the Basal Ganglia?
Group of large subcortical structures in the forebrain including :
Putamen
Caudate Nucleus
Globus Pallidus
What is the Basal Ganglia responsible for?
Initiating an action not guided by a stimulus. Is also critical for learning motor skills, organizing sequences of movement and “ automatic” behaviors such as driving a car
Where does input to the caudate nucleus and putamen mostly come from?
The Cerebral Cortex
Where does output from the caudate nucleus and putamen go to?
To the Globus Pallidus and then to the thalamus .
the thalamus then relays it to the cerebral cortex, especially its motor and areas of the prefrontal cortex
Most of the output from Globus Pallidus to the Thalamus releases…
GABA
Globus Pallidus is constantly inhibiting the thalamus
input from caudate nucleus and putamen tells the Globus Pallidus which movements to stop inhibiting
How is the Basal Ganglia particularly important for self-initiated behaviors?
the Basal Ganglia select a movement by ceasing to inhibit it, this circuit is important for these self- initiated behaviors
True or False. The Cerebral Cortex is the only brain area responsible for learning new skills?
False. All brain areas responsible for control of movement are important for learning new skills
Explain the process of the neurons in the motor cortex as a person or animal learns a new motor skill
Movements are slow and inconsistent at first.
As movements become faster, relevant neurons increase their firing rates
After prolonged training, movement patters become more consistent from trial to trial.
Motor cortex increases its signal to noise ratio
What is Saccade?
A voluntary eye movement from one target to another.
What is an anticaccade task?
Inhibiting the voluntary eye movement away from a target.
Performing this task well requires sustained activity in parts of the prefrontal cortex and basal ganglia by seeing the moving stimulus. Ability to perform this task matures throughout adolescence
What is Parkinson’s Disease?
a disease characterized by rigidity, muscle tremors, slow movements, difficulty initiating physical and mental activity, and slow on cognitive tasks. Caused by impairment of the Basal Ganglia.
Associated with an impairment in initiating spontaneous movement in the absence of a stimulus to guide the action
What are some possible causes of Parkinson’s disease?
An immediate cause is gradual progressive death of neurons, especially in the substania nigra which leads to increased inhibition of thalamus and then decreased excitation of cerebral cortex- loss of dopamine activity leads to less stimulation of motor cortex and slower onset of movement
Environmental influences can also contribute to Parkinsosn’s- MPTP- a chemical that converts to MPP+ accumulates in the brain and then destroys neurons that release dopamine . ( found in herbicides, pesticides and some illegal drugs)
What does the Substania Nigra do?
Sends dopamine- releasing axons to the caudate nucleus and putamen ( basal ganglia)
dopamine excites the caudate nucleus and putamen and a decrease in that excitation causes decreased inhibition of the globus pallidus
What happens if there is a loss of dopamine?
less stimulation of motor cortex which results in slower movements. the thalamus is inhibited
Cigarette smoking and coffee drinking have what effect on the chance of developing Parkinson’s disease?
A Decreased chance of developing Parkinson’s
What is the most common factor of increase risk of Developing Parkinson’s?
Damaged Mitochondria. When Mitochondria begin to fail, a chemical called alpha-synuclein clots into clusters that damage neurons containing dopamine
How is L-Dopa used to treat Parkinson’s?
Taken as a daily pill, L-Dopa is a precursor to dopamine and can cross the blood-brain barrier. The goal is to restore the missing dopamine.
What are some problems with L-Dopa as a treatment for Parkinson’s?
Ineffective for some patients, especially those in the late stages of the disease. It does not prevent continued loss of neurons, and it produces unpleasant side effects
Besides L-Dopa, what are some other therapies for treatment of Parkinson’s?
Anti-oxidant drugs, Electrical stimulation, Drugs that decreases apoptosis, Neurotrophins to promote survival of neurons, stimulation of cannabinoid receptors, transplanting brain tissue from aborted fetuses ( controversial and only partially effective)
How do we decrease the need for aborted fetuses tissue for Parkinson’s patients?
Stems cells grown in tissue cultures that are capable of differentiation.
What is Huntington’s Disease?
a sever neurological disorder that strikes about 1 in 10,000 people. symptoms include arm jerks, facial twitches and the develop into writhing of other parts of the body. Ability to learn and improve new movements is limited.
Associated with gradual, extensive brain damage.
What parts of the brain does Huntington’s damage?
Caudate Nucleus, Putamen and Globus Pallidus ( Basal Ganglia). Also in Cerebral Cortex
A what age does Huntington’s present?
between 30 and 50. As symptoms emerge, they grow progressively worse, culminating in death as basic functions are affected
In Huntington’s, where is the gene controlled?
An Autosomal dominant gene on chromosome #4.
critical area of the gene includes a sequence of bases C-A-G which repeats 11-24 times in most people. People with up to 35 repetitions are safe, 36-38 have a low risk, but not till old age, 39 or more are highly likely to get it
What is Huntingtin?
The protein that codes the disease’s gene.
The mutant form impairs neurons in the brain, future drug therapy may address huntingtin
