1. Chapter Eight Movement

2. Control of Movement Muscles and Their Movements Fast Muscles
fast contractions but easily fatigued
Used for rapid activity
Slow Muscles
slow contractions but resistant to fatigue
Used for walking, nonstrenuous activity

3. Control of Movement Muscles and their Movement
Muscle Control by Proprioceptors
proprioceptors-receptor that is sensitive to the position or movement of a part of the body
muscle spindle-receptor parallel to the muscle that responds to the stretch of the muscle
golgi tendon organ-responds to increases in muscle tension

4. acts as a brake or shock absorber to prevent a contraction
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.

5. Units of Movement Voluntary Movements
most movements are a combination of voluntary and involuntary (ex: walking)
Involuntary Movements
Reflexes-consistent automatic responses to stimuli

6. Brain Mechanisms of Movement
Cerebral Cortex
Primary Motor Cortex-stimulation along this cortex can elicit coordinated movements
Posterior Parietal Cortex-some neurons respond to visual or somatosensory stimuli, some respond mostly to current or future movements, or some respond to stimulus/response mixtures
Prefrontal cortex-responds to sensory signals that lead to a movement
Premotor cortex-most active during preparations for a movement
Supplementary motor cortex-most active during preparations for a rapid series of movements

7. 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.

8. Connections from the Brain to the Spinal Cord
Dorsolateral Tract
set of axons from primary motor cortex and surrounding areas
also arises from red nucleus
controls movement in peripheral areas (ex: toe)
Ventromedial Tract
many axons from the primary motor cortex and supplementary cortex, midbrain, reticular formation and vestibular nucleus
controls muscles of the neck, shoulders, and trunk

9. 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.

10. 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.

11. Cerebellum Functions habit formation timing attention
coordination of movements
Organization
cells are arranged in precise geometrical patterns
Purkinje cells exist in sequential planes
parallel fibers are parallel to one another but perpendicular to the planes of the Purkinje cells

12. 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.

13. Basal Ganglia Basal Ganglia
Large subcortical structures in the forebrain
Substructures
Caudate nucleus-receive input from thalamus/cortex
putamen-receive input from thalamus/cortex
globus pallidus-sends information to the thalamus and on to the motor and premotor cortices
Role in movement
Organize action movements
Selection or inhibition of movements
Control of muscle force

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

15. Parkinson’s Disease
Symptoms-rigidity, muscle tremors, slow movement, difficulty initiating movement
Brain Changes-Selective loss of cells in substantia nigra and amygdala/decrease in dopamine
Possible Causes
genetics
exposure to toxins (MPTP)
smoking decreases risks/these data have been questioned

16. Figure 8.16  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.

17. Figure 8.17  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.

18. Parkinson’s Disease L-Dopa Treatment precursor for dopamine
demonstrates individual effectiveness
does not stop progression of the disease
numerous side effects (nausea, restlessness, sleep problems, low blood pressure, hallucinations, and delusions)
Therapies Other Than L-Dopa
antioxidants, dopamine receptor stimulants, glutamate blockers, neurotrophins, drugs that decrease apoptosis, pallidotomy, cell transplants

19. Huntington’s Symptoms facial twitch, tremors across body, writhing
Cause
genetic-autosomal dominant gene
huntingtin-abnormal protein found inside the cells of Huntington’s victims