Chapter 8 - Movement

Question 0

What are smooth muscles?

Answer 0

Muscles which control the digestive system and other organs.

Question 1

Vertebrate muscles fall into 3 categories. What are they?

Answer 1

Smooth muscles, skeletal or striated muscles, and cardiac muscles.

Question 2

What are skeletal or striated muscles?

Answer 2

They control movement of the body in relation to the environment.

Question 3

What are cardiac muscles?

Answer 3

They are the heart muscles which have properties intermediate between those of smooth and skeletal muscles.

Question 4

How do muscles receive information?

Answer 4

Each muscle is composed of many fibres. A given axon can provide information for more than one muscle fibre. The eye muscles have a ratio of about one axon per 3 muscle fibres, the biceps muscles of the arm have a rain of one axon to more than a hundred fibres. This difference allows the eye to move more precisely than the biceps.

Question 5

What is the neuromuscular junction?

Answer 5

It is a synapse between a motor neuron axon and a muscle fibre. In skeletal muscles, every axon releases acetylcholine at the neuromuscular junction, and acetylcholine always excites the muscle to contract. A deficit of acetylcholine or its receptors impairs movement.

Each muscle makes just one movement, contraction. Muscles simply real when there is no message to contract.

Question 6

What are antagonistic muscles?

Answer 6

These muscles are opposing sets of muscles that are used for moving a leg or arm back and forth.

Question 7

What is a flexor muscle?

Answer 7

It is an antagonistic muscle. It can bring your hard towards your shoulder (like the biceps which contract in)

Question 8

What is an extensor muscle?

Answer 8

It is an antagonistic muscle that straightens the arm (like the triceps which lengthen when utilised)

Question 9

What are fast twitch fibres?

Answer 9

They are a type of muscles with fast contractions and rapid fatigue. Eg. We use these to run up a steep hill. Prolonged use of these causes fatigue because the process is anaerobic (that is they do not need oxygen at the time but need oxygen for recovery. Using them builds up an oxygen debt. Sprinters use fast twitch fibres.

Question 10

What are slow twitch fibres?

Answer 10

Muscles types with less vigorous contractions and no fatigue. Eg. We use these to talk (which we can do for a long time) and walking. These fibres do not fatigue because they are aerobic (that is they use oxygen during their movements. Marathon runners build up slow twitch fibres

Question 11

Describe what happens when you ride your bike?

Answer 11

At first your a giving is aerobic, using your slow twitch fibres. However, your muscles use glucose and after a while your glucose supplies begin to dwindle. Low glucose activates a gene that inhibits the muscles from using glucose, thereby saving the glucose for the brain. You start relying more on the fast twitch fibres that depend on anaerobic use of fatty acids. as you continue Bucy long, your muscles gradually fatigue.

People Cary in the percentages of fast twitch and slow twitch fibres.

Question 12

What is a proprioceptors ?

Answer 12

It is a receptor that detects the position or movement often a part of the body ie a muscle. It controls the movement. Muscle proprioceptors detect the stretch and tension of a muscle and send messages that enable the spinal cord to adjust its signals. When a muscle is stretched the spinal cord sends a reflexive signal to contract it. This stretch reflex is caused by a stretch, it does not produce one. (The knee jerk reflex is an example of a stretch reflex).

They also provide info to the brain.

Question 13

What is a muscle spindle?

Answer 13

It is a type of proprioceptor. It is a receptor parallel to the muscles that responds to a stretch. Whenever the muscle spindle is stretched, its sensory nerve sends a message to a motor neuron in the spinal cord, which in turn sends a message back to the muscles surrounding the spindle, causing a contraction.

When you set your foot down on a bump on the road, your knee bends a bit, stretching the extensor muscle of the leg. The sensory nerves of the spindles send action potentials to the motor neuron in the spinal cord, and the motor neuron sends action potentials to the extensor muscle. Contracting the extensor muscle straightens the leg, adjusting for the bump in the road.

Question 14

What are Golgi tendon organs?

Answer 14

These are also proprioceptors. They respond to increases in muscle tension. They are located in the tendons at opposite end of the muscle, they act as a brake against an excessively vigorous contraction. Some muscles are so strong that they could damage themselves if too many fibres contract at once.

The Golgi tendon organs detect tension , their impulses travel to the spinal cord, where they excite inter neurons that inhibit the motor neurons. In short, a vigorous muscle contraction inhibits further contraction by activating the Golgi tendon organs.

Question 15

What are reflexes?

Answer 15

They are constant automatic responses to stimuli. We think of them as being involuntary. Eg. Stretch reflexes, the constriction of the pupil in response to bright light.

Few behaviours are purely voluntary or involuntary. Walking involves voluntary movements and involuntary compensations for bumps in roads, etc, and you also swing your arms automatically.

Question 16

List some infant reflexes.

Answer 16

The grasp reflex (if you place an object in an infants hand they will grasp it), Babinski reflex (if you stroke the sole of the foot the baby will fan it’s toes), rooting reflex (if you touch it’s cheek the head will move and sucking will start, this is not a pure reflex as it depends on the hunger).

These reflexes are suppressed with age.

Question 17

What are ballistic movement?

Answer 17

A ballistic movement is executed as a whole, once initiated it cannot be altered. Reflexes are ballistic (as in the missiles). This is different to most other behaviours that are subject to feedback correction.

Question 18

What are central pattern generators?

Answer 18

Neural mechanisms in the spinal cord that generate rhythmic patterns of motor output. These are used for behaviours that consist of rapid sequences such as speaking, writing, dancing or playing a musical instrument. Cells in the lumbar segments of the spinal cord generate this rhythm.

Question 19

What is as motor program?

Answer 19

A fixed sequence of movements. The sequence is fixed from beginning to end. Eg. Yawning, some facial expressions like smiling and frowns.

Question 20

What elicits movement?

Answer 20

Direct electrical stimulation of the primary motor cortex.

Question 21

What is the primary motor cortex?

Answer 21

The precentral gyrus of the frontal cortex, just anterior to the central sulcus.

Question 22

How do messages get to the muscles?

Answer 22

The motor cortex axons extend to the brain stem and spinal cord, which generate the impulses that control the muscles.

Question 23

For which movements is the cerebral cortex important?

Answer 23

It is important for complex actions like talking and writing. It is less important for coughing, sneezing, gagging, laughing or crying. Perhaps the lack of cerebral control explains why it is hard to perform such actions voluntarily.

Question 24

Describe the different parts of the primary motor cortex.

Answer 24

Researchers have linked parts of the primary motor cortex with different parts of the body. Each brain area controls a structure on the opposite side of the body. Note that one region is not responsible for one structure as the regions overlap. Research found that repeated stimulation of a spot elicited the same result each time. It produced an outcome, not a particular muscle movement.

Question 25

The primary motor cortex is important for making movements but not for planning them. What parts of the brain help with the planning?

Answer 25

Posterior parietal cortex, supplementary motor cortex, premotor cortex, prefrontal cortex.

Question 26

Why is the posterior parietal cortex important for movement?

Answer 26

This area is one of the first areas to become active. It keeps track of the position of the body relative to the world. People with damage here tend to bump into things. The posterior parietal cortex is also important for planning movement.

When people are preparing to move people first see a signal that tells them what they are supposed to do and then they wait a few seconds for a second signal that says it is time for action. The posterior parietal cortex is active throughout the delay, evidently preparing for the movement.

Question 27

Describe the supplementary motor cortex.

Answer 27

This is important for planning and organising a rapid sequence of movement. It helps to inhibit behavioural habits

Question 28

Why is the premotor cortex important?

Answer 28

This is most active immediately before a movement. It receives info about the target to which the body is directing its movement as well as info about the body’s current position and posture.

Question 29

How is the prefrontal cortex linked to movement?

Answer 29

It stores sensory information relevant to a movement. It is also important for considering the probable outcomes of possible movements. Damage in this area can cause illogical or disordered movement like showering with clothes on. This area is inactive during dreams, hence the illogical nature.

Question 30

What are mirror neurons?

Answer 30

They are active both during preparation for a movement and while watching someone else perform the same or a similar movement. Mirror neurons in part of the frontal cortex become active when people smile or see someone else smile and they respond especially strong in people who report identifying strongly with the other person.

Mirror neurons are activated not only in seeing an action but also by any reminders of the action (hearing, seeing, doing, reading about it. At least some, maybe most, mirror neurons develop their responses by learning. Newborns are believed to have built in mirror neurons.

Question 31

Where do conscious decisions to move come from?

Answer 31

On average, people report that their decision to move occurred before the actual movement. Your motor cortex produces a kind of activity called a readiness potential before any voluntary movement, and the readiness potential begins at least 500ms before the movement. The key point is that the brain activity responsible for the movement apparently began before the person’s conscious decision. Therefore, your conscious decision is at first unconscious. Your decision to do something builds up to a certain strength before it becomes conscious.

Question 32

Where do movement messages from the brain go next?

Answer 32

The medulla and the spinal cord, which control movement. Diseases of the spinal cord impair the control of movement in various ways.

Question 33

What are corticospinal tracts?

Answer 33

Paths from the cerebral cortex to the spinal cord. We have 2 tracts, the lateral corticospinal tract (which controls the lateral parts of the body, the hands and feet) and the medial corticospinal tract (controls the medial parts of the body including the trunk and neck). Nearly all movements rely on a combination of both tracts but a movement may rely on one more than the other.

The tracks go through the medulla. Touch is also important for movement.

Question 34

Describe the lateral corticospinal tract.

Answer 34

It is a set of axons from the primary motor cortex, surrounding areas, and the red nucleus. Axons of the lateral tract extend directly from the motor cortex to their target neurons in the spinal cord. In bulges of the medulla called pyramids, the lateral tract crosses to the contralateral side of the spinal cord (they are also called pyramid tracts). It controls movements in peripheral areas like the hands.

Question 35

Describe the development of a child’s primary motor cortex.

Answer 35

In newborn humans, the immature primary motor cortex has partial control of both ipsilateral and contralateral muscles. As the contralateral control improves over the first year and a half of life, it displaces the ipsilateral control, which gradually becomes weaker. In some children with cerebral palsy, the contralateral path fails to mature and the ipsilateral path remains relatively strong. The resulting competition causes clumsiness.

Question 36

What is the red nucleus?

Answer 36

A midbrain area that is primarily responsible for controlling the arm muscles

Question 37

Describe the medial corticospinal tract.

Answer 37

This includes axons from many parts of the cerebral cortex, not just the motor cortex. It also includes axons from the midbrain tectum, the reticular formation, and the vestibular nucleus.

Axons of the medial tract go to both sides of the spinal cord (not just the contralateral side). The medial tract controls mainly the muscles of the neck, shoulders, trunk and therefore movement like walking, turning, bending, standing up, and sitting down. Note that these movements are bilateral (to walk you need to use both sides).

Question 38

What is the cerebellum important for?

Answer 38

It contains more neurons than the rest of the brain combined and an enormous number if synapses. It is a motor structure but it can respond to sensory stimuli even in the absence of movement. It can establish new motor program’s and thus damage can impair motor learning. Very important for tasks that require timing. Appears to be important for attention.

Question 39

Describe the effects if damage.

Answer 39

Has trouble with rapid movements that require aim, timing and alternations of movement. Eg. Trouble clapping hands, playing music, athletic activities, speaking, writing. They can do continuous motor activity. The symptoms can resemble those with alcohol intoxication due to clumsiness, slurred speech, and inaccurate eye movement.

Question 40

Describe the cellular organisation of the cerebellum.

Answer 40

The cribellum receives input from the spinal cord, from each of the sensory systems by way of the cranial nerve nuclei, and from the cerebral cortex. This informant reaches the cerebellar cortex (the surface of the cerebellum).

1. The neurons are arranged in precise geometric patterns
2. Purkinje cells are flat cells in sequential planes, parallel to each other
3. The parallel fibres are axons parallel to one another and perpendicular to the planes of the Purkinje cells.
4. Action potentials in parallel fibres excite one Purkinje cell after another. Each Purkinje cell then transmitte an inhibitory message to cells in the nuclei of the cerebellum (clusters of the cell bodies in the interior of the cerebellum) and the vestibular nuclei in the brain stem, which in turn send info to the midbrain and the thalamus
5. If the parallel fibres stimulate only the first few Purkinje cells the result is a brief message to the targeted cells. If they stimulate more, the message lasts ,longer. The output of the Purkinje cells controls the timing of a movement, including the onset and offset.
6. See diagram p250

Question 41

What is the basal ganglia?

Answer 41

It applies collectively to a group of large subcortical structures in the forebrain. People vary in the structures that they include in the basal ganglia but everyone agrees on the caudate nucleus, the putamen, and the globus pallidus.

Question 42

Describe the communication process within the basal ganglia.

Answer 42

1. Input comes to the caudate nucleus and putamen, mostly from the cerebral cortex
2. Output from the caudate nucleus and putamen goes to the globus pallidus. Then mainly to the thalamus, which sends it to the cerebral cortex, especially the motor areas and the prefrontal cortex.
3. Output from the globus pallidus to the thalamus releases GABA (an inhibitory transmitter). Input from the caudate nucleus and putamen tells the globus pallidus which movements to stop inhibiting (those with damage may have involuntary, jerky movements)
4. In effect, the basal ganglia select a movement by ceasing to inhibit it.
5. Note the basal ganglia is critical for learning new habits. People with damage Re impaired at learning motor skills and converting it into automatic responses.

Question 43

What is the antisaccade task?

Answer 43

A voluntary eye movement from one target to another.

Question 44

What are the main symptoms of Parkinson’s disease?

Answer 44

Rigidity, muscle emirs, slow movements and difficulty initiating physical and mental activity. Slow on cognitive tasks (eg imagining events or actions). A loss of olfaction is often an early symptom. Depression and memory loss are also common symptoms beginning early.

The basal ganglia have cells specialised for learning to start or stop a voluntary sequence of motions. These cells are impaired resulting in difficulty with spontaneous movements in the absence of stimuli to guide their actions. Eg. They walk surprisingly well when part of a parade or going up stairs.

Question 45

What is the immediate cause of Parkinson’s disease?

Answer 45

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.

Question 46

What is the main route between the substantia nigra and the verbal cortex?

Answer 46

Known as the direct pathway.

1. Axons from the substantia nigra release dopamine that excites the caudate nucleus and putamen.
2. The caudate nucleus and putamen inhibit the globus pallidus, which in turn inhibits parts of the thalamus
3. For people with Parkinson’s, decreased output from the substantia nigra means less excitation of the caudate nucleus and putamen, thus less inhibition of the globus pallidus, thus increase output to the thalamus. The net result is decreased activity in the thalamus and also parts of the cerebral cortex, leading to less stimulation of the motor cortex and slower onset of movements.
4. If the surviving substantia nigra neurons declines below 20 - 30% of normal, Parkinsons symptoms begin.

Question 47

What is the difference between early onset and late onset Parkinsons?

Answer 47

A twin study shows that for monozygotic twins, if one develops early onset, then the other will almost certainly get it too (gene related). If the twin gets late onset after 50 then the chance of the other twin getting it is the same as for the rest of the population (low hereditability).

Question 48

What environmental influences might be relevant to developing Parkinsons?

Answer 48

1. Hazardous chemical exposure (many damage the cells of the substantia nigra)
2. More common in farmers (exposure to herbicides and pesticides)
3. Cigarette smoking (including nicotine-free tobacco) and coffee drinking (caffeinated and decaffeinated) have less chance of developing Parkinsons
4. What the different causes have in common are damage to the mitochondria. When these begin to fail a process starts which damage neurons containing dopamine.

Question 49

What is L-dopa?

Answer 49

If Parkinson’s is due to a deficiency in dopamine then lets replace it. Dopamine does not cross the bold-brain barrier but L-dopa (a precursor to dopamine) does cross the barrier.

This is the main treatment for Parkinson’s. A daily pill, L-dopa reaches the brain where neurons convert it to dopamine.

Problems include the fact that it is ineffective in some patients, it does not prevent the continued loss of neurons, unpleasant side effects (nausea, restlessness, sleep problems, low blood pressure, delusions)

Question 50

What other treatments are there for Parkinsons?

Answer 50

1. High frequency electrical stimulation is especially effective for blocking tremors and enhancing movement. However, it also leads to depressed mood by inhibiting serotonin release. It also leads to impulsive decision making.
2. A new study tried to transplant substantia nigra from fetus rats. Only immature cells seemed to make the connection and even then the cells need to be retrained. The operation is difficult and expensive. Also where to get the cells from? They require the brain cells of 4-8 foetuses. Growing stem cells (immature cells that are capable of differentiating into a wide variety of other cell types) is an option. The results so far are modest at best. One limitation is that surgeons usually limit the procedure to ageing patients with advanced stages yet research shows that it is more effective in the early stages.

Question 51

What is Huntington’s disease?

Answer 51

A severe neurological disorder. Motor symptoms usually begin with arm jerks and facial twitches. Then tremors spread to other parts of the body and develop into writhing. 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.

It is gradual brain damage, especially in the caudate nucleus, putamen, and globus pallidus, but also the cerebral cortex.

Other symptoms include depression, sleep disorders, memory impairment, anxiety, hallucinations, delusions, poor judgement, alcoholism, drug abuse, sexual disorders. Deficits in memory and reasoning usually proceed the motor symptoms. Eventuate in death. Usually appears 30-50 years.

Question 52

What causes Huntington’s?

Answer 52

The disease results from a dominant gene on chromosome 4. An examination of a persons chromosomes can reveal with almost perfect accuracy whether or not hey will get Huntington’s disease (the more cytosine, adenine, guanine base repetitions someone has, the earlier the probable onset of the disease.

Question 53

what is the best gauge of insomnia?

Answer 53

how the person feels the next day

Question 54

What causes insomnia?

Answer 54

noise, uncomfy temp, stress, pain, diet, meds, epilepsy, Parkinson’s disease, brain tumors, depression, anxiety, neurological or psychiatric conditions, allergies, shifts in circadian rhythms eg the hypothalamus doesn’t think that it is late enough (phase delayed). Phase advanced means that they will fall asleep early.

Question 55

what is sleep apnia?

Answer 55

Impaired ability to breath while sleeping. They may be breathless for periods of a minute or so and wake up gasping. They suffer from sleepiness, impaired attention, depression and sometimes heart problems. People with sleep apnea have brain areas that appear to have lost neurons and consequently they show deficiencies of learning, reasoning, attention and impulse control. Correlational data do not tell us whether the brain abnormalities ld to sleep apnea or visa versa but research with rats suggests that the apnea leads to the brain changes.

Question 56

what causes sleep anpea?

Answer 56

genetics, hormones, old age deterioration of the brain mechanisms that regulate breathing. Obesity, especially in middle aged men. The obesity narrows the airways causing the men to breath faster which they can not keep up whilst asleep. People with sleep apnea are adviced to lose weight, avoid alcohol and tranquilisers.

Question 57

What is narcolepsy?

Answer 57

A condition characterised by frequent periods of sleepiness during the day. No gene has been identified. People usually have no close relative with the condition.

Question 58

What are the symptoms of narcolepsy?

Answer 58

Note that not every patient has all four. 1. gradual or sudden attacks of sleepiness during the day. 2. occasional cataplexy (an attack of muscle weakness whilst still awake). This is often triggered by strong emotions. 3. Sleep paralysis (an inability to move while falling asleep or waking up). 4. hypnagogic hallucinations (dreamlike experiences that the person has trouble distinguishing from reality, often occurring at the onset of sleep).

Question 59

what causes narcolepsy?

Answer 59

orexin. People with this lack the hypothalamic cells that produce and release orexin. People with Huntington’s often loose cells in the hypothalamus and have problems staying awake during the day and asleep during the night. The most popular treatment at the moment os ritalin which enhance dopamine and norepinephrine activity.

Question 60

what is periodic limb movement disorder?

Answer 60

A sleep disorder characterised by repeated involuntary movement of the legs and sometimes the arms. Mostly in middle aged and older.

Question 61

What is REM behaviour disorder?

Answer 61

This is a sleep disorder in which the person moves around vigorously in their sleep, apparently acting out their dreams that frequently involve defending themselves. Occurs mostly in older men, especially with brain damage that includes the pons (the pons sends inhibitory neurotransmitters to control movement)

Question 62

What are night terrors?

Answer 62

Experiences of intense anxiety from which a person awakens screaming in terror. These occur during NREM sleep and are more common in children than in adults.

Question 63

Describe sleepwalking

Answer 63

Sleepwalking runs in families and occurs mostly in children. Thy often have other sleep difficulties like snoring, bedwetting. Causes not well understood but more common when person is sleep deprived or under unusual stress. Most common during stages 3 and 4 and is not accompanied by dreams.

Question 64

what is sexsomnia?

Answer 64

people engage in sexual behaviour either with a partner or masturbation. They do not remember it afterwards.