Chapter Eight Movement 1 of 34 James W. KalatBiological Psychology, 8th Edition Chapter 8: Movement.

Chapter Eight Movement

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James W. Kalat Biological Psychology, 8th Edition

Chapter 8: Movement

Muscles and Their Movements

• Smooth muscles control internal organs– long thin cells

• Skeletal or striated muscles control movement of body in relation to the environment – long cylindrical with stripes– neuromuscular junction: synapse of motor neuron with

muscle fiber

• axons release acetylcholine at synapse– each muscle moves in one direction and in absence of

acetlycholine it relaxes– movement in two directions requires antagonistic

muscles: flexor to raise arm and extensor to lower arm

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James W. KalatBiological Psychology, 8th Edition

Chapter 8: Movement

Figure 8.3 A pair of antagonistic muscles. The biceps of the arm is a flexor; the triceps is an extensor. (Source: From Biology: The Unity and Diversity of Life, 5th Edition, by C. Starr and R. Taggert, p.331. Copyright © 1989 Wadsworth. Reprinted by permission.)

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Chapter 8: Movement

Muscles and Their Movements cont.

• Cardiac or heart muscles– fibers that fuse together at points– somewhat between smooth and skeletal muscles

• Myasthenia Gravis is autoimmune disease– immune system anti-bodies attack acetylcholine

receptors; – weakness and rapid fatigue of muscles because motor

neurons can’t constantly produce maximum acetylcholine– treated by drugs that inhibit acetylcholinesterase to

prolong acetylcholine

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Chapter 8: Movement


• Fish– white muscles: fast contractions, easily fatigued, needed

to maintain speed in cold water– pink muscles: intermediate speed contractions, less

easily fatigued, used to support activity in warm-cool water

– red muscles: slow contractions, resistant to fatigue, relies on red muscles in warm water

• Human– fast twitch fibers: fast contractions, easily fatigued,

increased by sprinting– slow twitch fibers: slow contractions resistant to fatigue,

increased by long-distance running

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Chapter 8: Movement


• Proprioceptors: receptor that is sensitive to the position or movement of a part of the body– muscle spindle: senses stretch of muscle and sends

negative feedback to motor neuron to contract– golgi tendon organ: senses increase in muscle tension

and sends message to inhibit motor neuron and brake contraction

– knee jerk: tap stretches spindle and feedback jerks leg up– loss of proprioceptor

• no automatic control from sensors

• requires constant visual monitoring to provide feedback

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Chapter 8: Movement

Figure 8.5 Two kinds of proprioceptors regulate the contraction of a muscle. When a muscle is stretched, the nerves from the muscle spindles transmit an increased frequency of impulses, resulting in a contraction of the surrounding muscle. Contraction of the muscle stimulates the Golgi tendon organ, which acts as a brake or shock absorber to prevent a contraction that is too quick or extreme.

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Chapter 8: Movement

Voluntary and Involuntary Movements

• Reflexes such as the stretch reflex or constriction of pupil to light are involuntary– infant reflexes include rooting, grasp, and Babinski – allied reflexes are strong in infants and still in adults, e.g.,

sneezing, closing eyes in strong sunlight

• Most movements, e.g., walking, are a combination of voluntary and involuntary muscle control– involuntarily adjust to irregularities in road and

automatically swing your arms

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Chapter 8: Movement

Sensitivity to Feedback

• Ballistic movements, e.g., reflexes, cannot be altered once started

• Central pattern generators– neural mechanisms in spinal cord and elsewhere that

generate rhythmic patterns, e.g., wing flapping in birds and fin movements in fish

– started by stimulus but motor program sets frequency of movement, e.g., cats scratch themselves 3-4 times/sec

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Chapter 8: Movement

Sensitivity to Feedback cont.

• Motor program is a fixed sequence of movements– Ex: cat washing face, gymnast with complex movements,

yawn– automatic patterns may be disrupted when thinking about

them, e.g., typing or playing piano– evolutionary holdover: chicken still flaps wings when

dropped even though can’t fly

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Chapter 8: Movement

Role of Cerebral Cortex

• Cerebral cortex important for complex actions such as writing– less voluntary movements e.g., coughing, laughing,

crying are controlled by subcortical areas

• Stimulation of primary motor cortex elicits certain outcome movements in corresponding body area– 500 msec stimulation of arm region of monkey results in

grasping movement and moving hand toward head– also, finger area of cortex active when pianist hears

music

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Chapter 8: Movement

Role of Cerebral Cortex cont.

• Posterior parietal cortex keeps track of position of body relative to environment – if damaged we can describe what we see but can’t walk

toward it, pick it up, or step over object

• Primary somatosensory cortex is main receiving area for touch and other body information– responds to shape of object and grasping, lifting or

lowering

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Chapter 8: Movement

Role of Cerebral Cortex cont.

• Prefrontal cortex active when planning and calculating possible outcomes of a movement– damage results in badly planned movements, showering

with clothes on, salting tea instead of food, etc.– inactive during dreaming and dreams are usually

haphazard

• Premotor cortex is active during preparations for a movement– receives information about target and body location

• Supplementary motor cortex active during preparations for a rapid series of movements; typing, dancing, speaking, playing musical instrument

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Chapter 8: Movement

Figure 8.8 Principal areas of the motor cortex in the human brain. Cells in the premotor cortex and supplementary motor cortex are active during the planning of movements, even if the movements are never actually executed.

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Chapter 8: Movement

Figure 8.9 Map of body areas in the primary motor cortex. Stimulation at any point in the primary motor cortex is most likely to evoke movements in the body areas shown. However, actual results are usually messier than this figure implies: For example, individual cells controlling one finger may be intermingled with cells controlling another finger. (Source: Adopted from Penfield & Rasmussen, 1950.)

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Chapter 8: Movement

Connections From Brain to Spinal Cord

• Messages from brain reach the medulla and spinal cord through dorsolateral or ventromedial tracts

• Dorsolateral (pyramidal tract)– originate from primary motor cortex, surrounding areas

and red nucleus – in pyramids of medulla, axons cross over to opposite side

of spinal cord but contralateral control develops gradually

• clumsiness in children with cerebral palsy comes from competition between contralateral and ipsilateral paths

– controls movement in hands, fingers, toes– damage here means loss of fine movements

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Chapter 8: Movement

Figure 8.11 The dorsolateral tract. This tract originates from the primary motor cortex, neighboring areas, and the red nucleus. It crosses from one side of the brain to the opposite side of the spinal cord and controls precise and discrete movements of the extremities, such as hands, fingers, and feet.

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Chapter 8: Movement

Connections From Brain to Spinal Cord cont.

• Ventromedial tract– includes axons from the primary and supplementary

motor cortex, midbrain tectum, reticular formation and vestibular nucleus

– do not cross to contralateral side because axons control bilateral movement of the neck, shoulders, and trunk

– damage here impairs walking, turning, bending, standing up and sitting down

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Chapter 8: Movement

Figure 8.12 The ventromedial tract. This tract originates from many parts of the cerebral cortex and several areas of the midbrain and medulla. It produces bilateral control of trunk muscles for postural adjustments and bilateral movements such as standing, bending, turning, and walking.

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Chapter 8: Movement

Role of Cerebellum

• Important for motor control and has more neurons than rest of brain

• Enhances new motor programs and skills

• Processes information about guiding movement, not the movement itself – active when weighing objects with hands or when objects

rub hands

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Chapter 8: Movement

Role of Cerebellum cont.

• Damage causes difficulty with:– rapid, ballistic movements, sequences that require

accurate aiming and timing, e.g., tapping rhythm, speaking, writing, playing musical instrument

– finger-to-nose task: initial rapid movement may strike face or hold segment of task may waver, as when intoxicated

– judging differences in delay in pairs of tones– normal shifting of attention within 100 msec: may take up

to a second

• Damage does not effect controlling force of movement or judging loudness of tones

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Chapter 8: Movement

Cellular Organization in Cerebellum

• Receives input from the spinal cord, sensory systems through the cranial nerve nuclei, and from the cerebral cortex

• Cells are arranged in precise, repeating geometrical patterns– Purkinje cells are very flat and exist in sequential planes– parallel fibers are perpendicular to the planes of the

Purkinje cells– parallel fibers excite Purkinje cell

• the more excited, the longer the duration of the Purkinje output which may control either a movement or a cognitive process

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Chapter 8: Movement

Figure 8.14 Cellular organization of the cerebellum. Parallel fibers (yellow) activate one Purkinje cell after another. Purkinje cells (red) inhibit a target cell in one of the nuclei of the cerebellum (not shown, but toward the bottom of the illustration). The more Purkinje cells that respond, the longer the target cell is inhibited. In this way the cerebellum controls the duration of a movement.

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Chapter 8: Movement

Role of Basal Ganglia

• Basal ganglia: group of large subcortical structures in the forebrain– caudate nucleus and putamen receive input from

thalamus and cortex– globus pallidus sends information to the thalamus where it

goes on to the motor and premotor cortices– stores sensory information to guide movements, learn

rules and organize sequences of movements into a smooth, automatic whole

• Organize action sequence into chunks or units like learning to drive a car (habit learning)

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Chapter 8: Movement

Role of Basal Ganglia cont.

• Active in selection or inhibition of movements, e.g.:– surgery patients had activity when they made a

movement with finger in response to signal– drawing a new line on computer

• Linked to obsessive-compulsive disorder– OCD is marked by repetitive thoughts and actions that

person knows is pointless or nonsensical– OCD increases activity in caudate nucleus and this may

be linked to strong habits

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Chapter 8: Movement

Figure 8.15 Location of the basal ganglia. The basal ganglia surround the thalamus and are surrounded by the cerebral cortex.

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Chapter 8: Movement

Parkinson’s Disease

• Gradual progressive death of neurons especially in substantia nigra – decrease in dopamine results in decreased excitation of

cerebral cortex

• Symptoms begin when neurons decrease 20%-30%– slow on cognitive tasks– some depression and cognitive deficits but no emotional

outbursts – rigidity, muscle tremors, slow movements and difficulty

initiating physical and mental activity

• but patients function well with visual cues, e.g., follow parade, climb stairs and step on lines at fixed intervals

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Chapter 8: Movement

Figure 8.17 Connections from the substantia nigra: (a) normal and (b) in Parkinson’s disease. Excitatory paths are shown in green; inhibitory are in red. The substantia nigra’s axons inhibit the putamen. Axon loss increases excitatory communication to the globus pallidus. The result is increased inhibition from the globus pallidus to the thalamus and decreased excitation from the thalamus to the cerebral cortex. People with Parkinson’s disease show decreased initiation of movement, slow and inaccurate movement, and psychological depression. (Source: Based on Wichmann, Vitek, &Delong, 1995.)

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Chapter 8: Movement

Parkinson’s Disease cont.

• Possible Causes– genetics

• early onset in identical twin good predictor for other twin but less so after 50 years of age

• 5 genes more common in patients but no specific gene for disease

– one cause is exposure to toxins, e.g., MPTP designer drug which destroys dopamine releasing neurons

• Smoking and caffeine decreases risks – inconsistent findings for caffeine

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Chapter 8: Movement

Figure 8.18 Probability of developing Parkinson’s disease if you have a twin who developed the disease before or after age 50. Having a monozygotic (MZ) twin develop Parkinson’s disease before age 50 means that you are very likely to get it too. A dizygotic (DZ) twin who gets it before age 50 does not pose the same risk. Therefore early-onset Parkinson’s disease shows a strong genetic component. However, if your twin develops Parkinson’s disease later (as is more common), your risk is the same regardless of whether you are a monozygotic or dizygotic twin. Therefore late-onset Parkinson’s disease has little or no heritability. (Source: Based on data of Tanner et al., 1999.)

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Chapter 8: Movement

L-Dopa Treatment

• Most common treatment– precursor for dopamine that crosses blood-brain barrier– effective in early to intermediate stages but some patients

do not benefit at all– does not stop progression of the disease, may do harm– side effects: nausea, restlessness, sleep problems, low

blood pressure, hallucinations, and delusions

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Chapter 8: Movement

Other Treatment

• One or more of following usually combined with L-Dopa– drugs: antioxidants, dopamine receptor stimulants,

glutamate blockers, drugs that decrease apoptosis, – electrical stimulation of globus pallidus, or surgery – neurotrophins to promote growth of remaining neurons– cell transplants

• most successful with substantia nigra cells transplanted from fetuses into young rats

• slight benefits with fetal brain transplants to patients

• neurotrophins may help if researchers can get them past blood-brain barrier

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Chapter 8: Movement

Huntington’s Disease

• Severe neurological disorder striking 1 in 10,000

• Extensive damage to caudate nucleus, putamen, and globus pallidus, and some in the cerebral cortex

• Symptoms most often appear between 30-50 years– begin with jerky arm movements, then facial twitch, later

tremors spread and develop into writhing – cannot learn new or improve movements– includes depression, memory impairment, anxiety,

hallucination

• may be misdiagnosed as schizophrenic

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Chapter 8: Movement

Chapter Eight Movement 1 of 34 James W. KalatBiological Psychology, 8th Edition Chapter 8: Movement.

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