Chapter 8 – Movement Flashcards
Those muscles that control the digestive system and other organs
Smooth muscles
Muscles that control movement of the body in relation to the environment
Skeletal muscles or striated muscles
Muscles of the heart that have properties intermediate between those of smooth and skeletal muscles
Cardiac muscles
A synapse between a motor neuron axon and a muscle fibre
Neuromuscular junction
Opposing sets of muscles that are required to move a leg or arm back-and-forth
Antagonistic muscles
Muscle that flexes the limb
Flexor
Muscle that straightens the limb
Extensor
Why can the eye muscles move with greater precision then the biceps muscles?
Each axon to the biceps muscles innervates about 100 fibers, therefore, it is not possible to change the movement by a small amount. In contrast, an axon of the eye muscle innervates only about three fibres
Which transmitter causes a skeletal muscle to contract?
Acetylcholine
Although each muscle fibre receives information from only one ____, a given ____ may innervate more than one muscle fibre
Axon
Each muscle makes just one movement:
Contraction
Understand the need for antagonistic muscles
Each muscle makes just one movement, contraction. There’s no message causing relaxation; the muscle simply relaxes when it receives no message to contract. There was also no message to move a muscle in the opposite direction. Moving a leg or arm back-and-forth requires opposing sets of muscles, called antagonistic muscles
Muscle fibres that produce fast contractions but fatigue rapidly
Fast-twitch fibres
Muscle fibres that have less vigourous contractions and no fatigue
Slow-twitch fibres
Proceeding without using oxygen at the time of a reaction.
Need oxygen for recovery.
Anaerobic
The use of oxygen during movements
Aerobic
Slow-twitch fibres do not fatigue because they are ______ – They use oxygen during their movements.
Prolonged use of fast-twitch fibres results and fatigue because the process is _______ – Using reactions that do not require oxygen at the time but need oxygen for recovery. Using them builds up an oxygen debt.
Aerobic; anaerobic
In what way are fish movements impaired in cold water?
Although a fish can move rapidly in cold water, it must rely on white muscles that fatigue easily
Duck breast muscles are red “dark meat”, whereas chicken breast muscles are white. Which species probably can fly for a longer time before fatiguing?
Ducks can fly great distances, as they often do during migration. The white muscles of a chicken breast has the power necessary to get a heavy body off the ground, but it fatigues rapidly. Chicken seldomly fly far
Why is an ultramarathoner like Bertil Jarlaker probably not impressive at short-distance races?
An ultramarathoner builds up large numbers of slow-twitch fibres at the expense of fast-twitch fibers. Therefore, endurance is great, but maximum speed is not
Describe the three kinds of muscles of a fish
Red, pink, and white
Red: produce the slowest movements, but they do not fatigue
White: produce the fastest movements, but they fatigue rapidly
Pink: intermediate in speed and rate of fatigue
At high temperatures, a fish relies mostly on red and pink muscles. At colder temperatures, the fish realize more and more on white muscles, maintaining its speed but fatiguing faster
A receptor that detects the position or movement of a part of the body
Proprioceptor
Muscle proprioceptor’s detect the stretch and tension of a muscle and send messages that enable the spinal cord to adjust its signals.
A reflexive contraction of a muscle in response to a stretch of that muscle
Stretch reflex
The stretch reflex is caused by a stretch; it does not produce one
A receptor parallel to the muscle that responds to a stretch
Muscle spindle
Whenever the muscle spindle is stretched, it’s sensory nerve sends a message to a motor neuron in the spinal cord, which in turn send a message back to the muscles surrounding the spindle, causing a contraction.
Note that this reflex provides for negative feedback; when a muscle and it’s spindle are stretched, the spindle sends a message that results in a muscle contraction that opposes the stretch.
Receptors that respond to increases in muscle tension; inhibit further contractions
Golgi tendon organs
Act as a break against an excessively vigourous contraction
If you hold your arm straight out and someone pulls it down slightly, it quickly bounces back. Which proprioceptor is responsible?
The muscle spindle
What is the function of Golgi tendon organs?
They respond to muscle tension and thereby prevent excessively strong muscle contractions
Automatic muscular responses to stimuli
Reflexes
A reflexive grasp of an object placed firmly in the hand
Grasp reflex
When an infants cheek is touched, the infant turns toward the stimulated cheek and begins to suck
Rooting reflex
The extension of the big toe and fanning of the others, by an infant, when the sole of the foot is stroked
Babinski reflex
Motion that proceeds as a single organized unit that cannot be redirected once it begins
Ballistic movement
Reflexes are ballistic
Neural mechanisms in the spinal cord that generate rhythmic patterns of motor output
Central pattern generators
Examples: the mechanisms that generate wing flapping in birds, fin movements in fish, and the wet dog shake.
A fixed sequence of movements
Motor program
Example: a mouse periodically grooms itself by sitting up, licking its paws, wiping them over his face, closing its eyes as the paws passover them, licking the paws again, and so forth. Once begun, the sequence is fixed from beginning to end.
A motor program can be gained or lost through evolution: a chicken dropped above the ground will extend its wings and flap, whereas ostriches, emails, and rheas which have not use their wings for flight for millions of generations, have lost the genes for flight movements and do not flap their wings when dropped.
Yawn in humans is another example
Area of the prefrontal cortex just anterior to the central sulcus; a primary point of origin for axons conveying messages to the spinal cord.
Direct electrical stimulation here elicits movements.
Does not send messages directly to the muscles. It’s axons extend to the brainstem and spinal cord, which generate the impulses that control the muscles. Particularly important for complex actions such as talking or writing. Less important for coughing, sneezing, gagging, laughing, or crying.
Primary motor cortex
What evidence indicates that cortical activity represents the “idea” of the movement and not just the muscle contractions?
Activity in the motor cortex leads to a particular outcome, such as movement of the hand to the mouth, regardless of what muscle contractions are necessary given the hand’s current location
Area with a mixture of visual, somatosensory, and movement functions, particularly in monitoring the position of the body relative to objects in the world
Posterior parietal cortex
One of the first areas to become active. Keeps track of the position of the body relative to the world.
Posterior parietal damage – have trouble finding objects in space, even after describing their appearance accurately. Bump into obstacles while walking.
Anterior portion of the frontal lobe, which responds mostly to the sensory stimuli that signal the need for a movement.
Active during a delay before movement, and stores sensory information relevant to a movement. Important for considering the probable outcomes of possible movements.
Prefrontal cortex
Damage to this area – many movements would be a logical or disorganized, such as showering with your clothes on or pouring water on the tube of toothpaste instead of the toothbrush. Inactive during dreams
Area of the frontal cortex, active during the planning of a movement.
Most active immediately before a movement. Receives information about the target to which the body is directing its movement, as well as information about the body’s current position and posture
Premotor cortex
Area of the frontal cortex; active during preparation of a rapid sequence of movements.
Supplementary motor cortex
If you have a habitual action, such as turning left when you get to a certain corner, the supplementary motor cortex is essential for inhibiting that habit when you need to do something else
How does the posterior parietal cortex contribute to movement? The premotor cortex? The supplementary motor cortex? The prefrontal cortex?
The posterior parietal cortex is important for perceiving the location of objects and the position of the body relative to the environment. It is also active for planning a movement.
The premotor cortex and supplementary motor cortex are also active in preparing a movement shortly before it occurs.
The prefrontal cortex stores sensory information relevant to a movement and considers possible outcomes of a movement.
Cells that are active during a movement and while watching someone else perform the same movement
Mirror neurons
When expert pianists listen to familiar, well-practised music, they imagine the finger movements, and the finger area of their motor cortex becomes active, even if they are not moving their fingers. If we regard those neurons as another kind of mirror neuron, what do these results tell us about the origin of mirror neurons?
These neurons must have acquired these properties through experience. That is, they did not enable pianists to copy what they hear; they developed after pianists learned to copy what they hear.
Different for different cells and movements. Some newborn infants imitate a few facial movements, especially tongue protrusion, which implies built-in mirror neurons that connect the site of a movement to the movement itself.
However, at least some – maybe most – mirror neurons develop their responses by learning
Recordable activity in the motor cortex prior to voluntary movement
Readiness potential
Explain the evidence that someone’s conscious decision to move does not cause the movement
Researchers recorded responses in peoples cortex that predicted the upcoming response. Those brain responses occurred earlier than the time people reported as “when they made the decision”
On what basis are some researchers sceptical of the evidence that someone’s conscious decision to move does not cause the movement?
The studies assume that people accurately report the times of their intentions. However, people’s reports are influenced by events after the movement, and therefore we cannot be confident of their accuracy
Paths from the cerebral cortex to the spinal cord
Corticospinal tracts
A set of axons from the primary motor cortex, surrounding areas, and midbrain area that is primarily responsible for controlling the peripheral muscles
Lateral corticospinal tract
A midbrain area that is primarily responsible for controlling the arm muscles
Red nucleus
Set of axons from many parts of the cerebral cortex, midbrain, and medulla; responsible for control of bilateral muscles of the neck, shoulders, and trunk
Medial corticospinal tract
Cluster of neurons in the brain stem, primarily responsible for motor responses to vestibular sensation.
Vestibular nucleus
Axons of this tract extend directly from the motor cortex to their target neurons in the spinal cord. In bulges of the medulla called pyramids, it crosses to the contralateral or opposite side of the spinal cord. It controls movement in the peripheral areas, such as the hands and feet.
Lateral Corticospinal tract
Axons of this track go to both sides of the spinal cord, not just to the contralateral side. Controls mainly the muscles of the neck, shoulders, and trunk and therefore such movements as walking, turning, bending, standing up, and sitting down. These movements are necessarily bilateral. You can move your fingers on just one side, but any movement of your neck or trunk must include both sides.
Medial corticospinal tract
Lack of voluntary movement in part of the body caused by damage to spinal cord, motor neurons, or their axons
Paralysis
Loss of sensation and voluntary muscle control in both legs. Reflexes remain. Although no messages pass between the brain and the genitals, the genital still respond reflexively to touch- have no genital sensations, but they can still experience orgasm.
Caused by a cut through the spinal cord above the segments attached to the legs.
Paraplegia
Loss of sensation and muscle control in all four extremities caused by a cut through the spinal cord above the segments controlling the arms
Quadriplegia
Loss of sensation and muscle control in the arm and leg on one side caused by a cut halfway through the spinal cord or damage to one hemisphere of the cerebral cortex
Hemiplegia
Impaired sensation in the legs and pelvic region, impaired reflexes and walking, loss of bladder and bowel control caused by late stage of syphilis or dorsal root of the spinal cord deteriorate
Tabes dorsalis
Paralysis caused by virus that damages cell bodies of motor neurons
Poliomyelitis
Gradual weakness and paralysis, starting with the arms and later spreading to the legs. Both motor neurons and axons from the brain to the motor neurons are destroyed – cause is unknown
Amyotrophic lateral sclerosis
What kinds of movements does the lateral tract control? The medial tract?
The lateral tract controls detailed movements in the periphery on the contralateral side of the body. For example, the lateral tract from the left hemisphere controls the right side of the body. The medial tract controls trunk movements bilaterally.
Describe the functions of the cerebellum
Decades ago, most texts describe the function as balance and coordination but has many more functions and more neurons than the rest of the brain combined.
Damage causes: trouble with rapid movements that require aim, timing, and alternations of movements. Such as tapping a rhythm, clapping hands, pointing out a moving object, speaking, writing, typing, or playing a musical instrument.
Impaired at almost all athletic activities except those that do not require aim or timing.
People with damage to this area are normal at continuous motor activity such as drawing continue with circles.
Functions other than movement:
Establishes new motor programs that enable one to execute a sequence of actions as a whole. Important for behaviours that depend on precise timing of short intervals such as judging which of two visual stimuli is moving faster or listening to two pairs of tones and comparing the delays between them.
Critical for certain aspects of attention
What kind of perceptual task would be most impaired by damage to the cerebellum?
Damage to the cerebellum impairs perceptual tasks that depend on accurate timing
The surface of the cerebellum
Cerebellar cortex
Flat cells in sequential planes, in the cerebellar cortex, parallel to one another
Purkinje cells
Axons parallel to one another and perpendicular to the plains of the Purkinje cells in the cerebellar cortex
Parallel fibres
Describe the action of parallel fibres and Purkinje cells
Action potentials in parallel fibres excite one Purkinje cell after another. Each Purkinje cells and transmits and inhibitory message to cells in the nuclei of the cerebellum (clusters of cell bodies in the interior of the cerebellum) and the vestibular nuclei in the brainstem, which in turn send information to the midbrain and the thalamus.
Depending on which and how many parallel fibres are active, they might only the first few Purkinje cells or a long series of them. Because the parallel fibres messages reach different Purkinje cells one after another, the greater the number of excited Purkinje cells, the greater their collective duration of response.
The output of Purkinje cells controls the timing of a movement, including both its onset and offset.
How are the parallel fibres arranged relative to one another and to the Purkinje cells?
The parallel fibres are parallel to one another and perpendicular to the planes of the Purkinje cells
If a larger number of parallel fibres are active, what is the effect on the collective output of the Purkinje cells?
As a larger number of parallel fibres become active, the Purkinje cells increase their duration of response
A group of large subcortical structures in the forebrain. Includes the caudate nucleus, the putamen, and the globus pallidus.
This area selects movement by seizing to inhibit it. Particularly important for self initiated behaviors.
This area is critical for learning new habits, especially learning motor skills and converting new movements into smooth automatic responses
Basal ganglia
Describe the action of the areas of the basal ganglia
Input it comes to the caudate nucleus and putamen, mostly from the cerebral cortex. Output from the caudate nucleus and putamen goes to the globus pallidus and from there mainly to the thalamus, which relays it to the cerebral cortex, especially its motor areas and the prefrontal cortex.
Most of the output from the globus pallidus to the thalamus releases GABA, and inhibitory transmitter and neurons in the globus pallidus show much spontaneous activity. Thus, the globus pallidus is constantly inhibiting the thalamus. Input from the caudate nucleus and putamen tells the globus pallidus which movements to stop inhibiting.
In effect, the basal ganglia select a movement by seizing to inhibit it. Particularly important for self-initiated behaviors.
Damage to this area results in decreased inhibition and therefore involuntary, jerky movements as seen in Huntington’s disease
Why does damage to the basal ganglia lead to involuntary movements?
Output from the basal ganglia to the thalamus releases the inhibitory transmitter GABA. Ordinarily, the basal ganglia produce steady output, inhibiting all movements or all except the one selected at the time. After damage to the basal ganglia, the thalamus, and therefore the cortex, receive less inhibition. Thus, they produce unwanted actions.
What kind of learning depends most heavily on the basal ganglia?
The basal ganglia are essential for learning motor habits that are difficult to describe in words, such as driving a car
What areas of the brain are important for restraining yourself from following some strong impulse, such as in the antisaccade task?
These tasks require sustained activity in parts of the prefrontal cortex and basil ganglia. The brain prepares itself, it sets itself to be ready to inhibit the unwanted action and substitute a different one.
Ability to perform the antisaccade task matures slowly because the prefrontal cortex is one of the slowest brain areas to reach maturity.
Malady caused by damage to a dopamine pathway, resulting in slow movements, difficulty initiating movement, rigidity of the muscles, and tremors
Parkinson’s disease
Describe the immediate physiological causes of Parkinson’s disease
The cells in the basal ganglia are specialized for learning to start or stop a voluntary sequence of emotions. These cells are impaired and Parkinson’s disease, and the result is a difficulty with spontaneous movements in the absence of stimuli to guide their actions.
Describe the causes of Parkinson’s disease
The immediate cause is the gradual progressive death of neurons, especially in the substantia nigra, which sends dopamine-releasing axons to the caudate nucleus and putamen. People with Parkinson’s disease lose these axons and therefore dopamine.
Axons from the substantia nigra release dopamine that excites the caudate nucleus and putamen. The caudate nucleus and putamen inhibit the globus pallidus, which in turn inhibits parts of the thalamus. For people with Parkinson’s disease, decreased output from the substantia nigra means less excitation of the caudate nucleus and putamen, and therefore less inhibition of the globus pallidus. The globus pallidus, freed from inhibition, increases its (inhibitory ) output to the thalamus. So the net result is decreased activity in the thalamus, and therefore also in parts of the cerebral cortex.
In summary, a loss of dopamine activity in the substantia nigra leads to less stimulation of the motor cortex and slower onset of movements.
Do monozygotic twins resemble each other more than dizygotic twins do for early-onset Parkinson’s disease? For late-onset? What conclusion do these results imply?
Monozygotic twins resemble each other more than dizygotic twins do for early-onset Parkinson’s disease, but not for late-onset. The conclusion is that early-onset Parkinson’s disease has higher heritability than the late-onset condition.
If you have a monozygotic twins who develops early onset Parkinson’s disease, you are almost certain to get it too. However, if your twin developed Parkinson’s disease after age 50, your risk is about the same regardless of whether your twin is monozygotic or dizygotic. These results imply that genes only weakly influence the risk of late onset Parkinson’s disease
Describe the environmental causes of Parkinson’s disease
An accidental discovery implicated exposure to toxins. In 1982, several young adults develop symptoms of Parkinson’s disease after using a drug similar to heroin. The substance responsible for the symptoms was MPTP, a chemical that the body converts to MPP+, which accumulates in, and then destroys, neurons that release dopamine.
It is more likely that Parkinson’s disease results from exposure to hazardous chemicals and herbicides and pesticides.
People who smoke cigarettes or drink coffee have less of a chance of developing Parkinson’s disease.
A chemical that the body converts to MPP+
MPTP
A chemical that accumulates in, and then destroys, neurons that release dopamine
MPP+
How does MPTP exposure influence the likelihood of Parkinson’s disease? What are the effects of cigarette smoking?
Exposure to MPTP can induce symptoms of Parkinson’s disease. Cigarette smoking is correlated with decreased prevalence of the disease.
Chemical precursor to dopamine
L-dopa
Describe the most common treatment for Parkinson’s disease
L-dopa
Used because dopamine does not cross the blood brain barrier, whereas L-Dopa does cross the barrier. L-dopa reaches the brain, where neurons convert it to dopamine.
Describe the problems with using L-dopa as a treatment for Parkinson’s disease
It is ineffective for some patients, especially those in the late stages of the disease
Does not prevent the continued loss of neurons
Produces unpleasant side effects such as nausea, restlessness, sleep problems, low blood pressure, repetitive movements, hallucinations, and delusions
How does L-dopa relieve the symptoms of Parkinson’s disease?
L-dopa enters the brain, where neurons convert it to dopamine, thus increasing the supply of a depleted neurotransmitter
In what ways is L-dopa treatment disappointing?
L-dopa is ineffective for some people and has only limited benefits for most others. It does not stop the loss of neurons. It has unpleasant side effects.
What are some possible treatments for Parkinson’s disease other than L-dopa?
Possible treatments include antioxidants, drugs that stimulate dopamine receptors, drugs that block glutamate or adenosine receptors, transferring a gene into the brain to increase dopamine synthesis, neurotrophins, drugs that decrease apoptosis, high-frequency electrical stimulation of the globus pallidus, and transplants of neurons or stem cells
A severe neurological disorder characterized by jerky arm movements and facial twitches and later by tremors, writhing movements, and psychological symptoms
Huntington’s disease
Gradually, the tremors interfere more and more with walking, speech, and other voluntary movements. The ability to learn and improve new movements is especially limited. The disorder is associated with gradual, extensive brain damage, especially in the caudate nucleus, putamen, and globus pallidus but also in the cerebral cortex.
People with Huntington’s disease also suffer psychological disorders, including depression, sleep disorders, memory impairment, anxiety, hallucinations and delusions, poor judgment, alcoholism, drug abuse, and sexual disorders.
Describe the genetic cause of Huntington’s disease
Results from a dominant gene on chromosome #4.
Protein produced by the gene whose mutation leads to Huntington’s disease
Huntingtin
What procedure enables physicians to predict who will or will not get Huntington’s disease and to estimate the age of onset?
Physicians can count the number of consecutive repeats of the combination C-A-G on one gene on chromosome 4. If the number is fewer than 36, the person will not develop Huntington’s disease. For repeats of 36 or more, the larger the number, the more certain the person is to develop the disease and the earlier the probable age of onset
People with up to 35 repetitions are considered safe. Those with 36 to 38 might get it, but probably not until old age. People with 39 or more are likely to get the disease, unless they die of other causes earlier.
