Ch 7

Question 1

Muscles and Their Movements [placeholder]

Answer 1

Vertebrate muscles fall into 3 categories

Question 2

Smooth muscles

Answer 2

• control internal organs (intestines)

Question 3

Cardiac or heart muscles

Answer 3

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Question 4

Skeletal or striated muscles

Answer 4

• control movement of body in relation to the environment
• long cylindrical with stripes

Question 5

Neuromuscular junction

Answer 5

• synapse of motor neuron with muscle fiber
• axons release acetylcholine at synapse, Ach excites the muscle to contract (move)
• each muscle can move in one only direction and in absence of acetlycholine it relaxes
• movement in the opposite direction requires another set of antagonistic muscles: flexor to raise arm and extensor to lower arm

Question 6

Myasthenia Gravis

Answer 6

• is autoimmune disease
• immune system anti-bodies attack acetylcholine receptors;
• If Ach can’t work on the receptors, muscles can’t contract
• Symptoms are weakness and rapid fatigue of muscles
• Motor neurons compensate by pumping out more Ach – not good for our motor neurons to constantly produce maximum acetylcholine
• treated by drugs that inhibit acetylcholinesterase to prolong acetylcholine

Question 7

fast twitch fibers

Answer 7

: fast contractions, easily fatigued, used when sprinting

• Fast twitch fibers are anaerobic – they do not require oxygen at the time of movement
• Also produce lactate and phosphate, which accumulate and make our muscles fatigued
• slow twitch fibers: slow contractions resistant to fatigue, used when talking or walking
• Slow twitch fibers are aerobic – they use oxygen in their movements

Question 8

anaerobic

Answer 8

– they do not require oxygen at the time of movement

Question 9

aerobic

Answer 9

they use oxygen in their movements

Question 10

Muscle Proprioceptor

Answer 10

• receptor that is sensitive to the position or movement of a muscle. Proprioceptors detect the stretch and tension of a muscle and send messages to the spinal cord to adjust its signals
• Sometimes when a muscle is stretched, a stretch reflex occurs, which is the spinal cord sending a reflexive signal to contract it

Question 11

muscle spindle

Answer 11

type of proprioceptor sensitive to stretch. It senses stretch of muscle and sends feedback to motor neuron to contract. This helps us to walk and hold things. (Contact!)

Question 12

golgi tendon organ

Answer 12

• type of proprioceptor sensitive to increases in muscle tension, sends message to inhibit motor neuron and brake contraction (too much muscle contraction can actually tear the muscle) (Don’t Contract!)
• loss of proprioception
• no automatic control from sensors
• requires constant visual monitoring to provide feedback

Question 13

Voluntary and Involuntary Movements [placeholder]

Answer 13

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Question 14

Reflexes

Answer 14

• consistent, automatic responses to stimuli (e.g., the stretch reflex or constriction of pupil to light)

—> infant reflexes include rooting, grasp, and Babinski

• Reflexes are considered ballistic movements because they cannot be altered once started
• 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 unless you tell yourself not to.

Question 15

Sensitivity to Feedback

Answer 15

• Many movements are rhythmic in nature (e.g., birds’ wings flapping)
• These types of movements are controlled by Central Pattern Generators

Question 16

Central Pattern Generators

Answer 16

• neural mechanisms in the spinal cord that generate rhythmic patterns
• They’re started by a stimulus then the pattern determines the frequency of movement, e.g., cats scratch themselves 3-4 times/sec

Question 17

Motor Program

Answer 17

• is a fixed sequence of movements caused by CPGs – in general, once started, they continue automatically until their completion
• Sometimes they’re there when we’re born, sometimes we learn them
• Ex: mouse washing face, gymnast with complex movements, yawn
• automatic patterns may be disrupted when thinking about them, e.g., typing or playing piano

Question 18

Role of Cerebral Cortex

Answer 18

• Remember, the primary motor cortex (precentral gyrus) is involved in controlling our movements
• But nothing there is directly attached to muscles, and the information has to follow several paths to get to them
• Cerebral cortex important for complex actions such as writing

—> less complex movements e.g., coughing, laughing, crying are controlled by subcortical areas

• Stimulation of primary motor cortex elicits movements in corresponding body area

Question 19

Areas Near the Primary Motor Cortex [placeholder]

Answer 19

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Question 20

Posterior parietal cortex

Answer 20

• keeps track of position of body relative to environment. Integrates our senses and motion
• if damaged we can describe what we see but can’t walk toward it, pick it up, or step over object (what pathway was that from the vision chapter?)

Question 21

Primary somatosensory cortex

Answer 21

• is main receiving area for touch and other body information
• responds to shape of object and grasping, lifting or lowering
• For example, if I put a door knob and a drawer handle, both attached to a board, under a cover, by touching it, you would know how to hold it in order to exert action on it. This is governed by your primary somatosensory cortex

Question 22

Areas Near the Primary Motor Cortex [placeholder] {small info dump}

Answer 22

• The prefrontal, pre-motor, and supplementary motor cortices all help us prepare to move. They all send messages to the primary motor cortex which then instigates the movement

Question 23

Prefrontal cortex

Answer 23

• 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.

Question 24

Premotor cortex

Answer 24

• is active during preparations for a single or few movements
• receives information about target and body location
• Works in conjunction with the posterior parietal cortex

Question 25

Supplementary motor cortex

Answer 25

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

Question 26

Connections From Brain to Spinal Cord [placeholder]

Answer 26

• Messages from brain reach the medulla and spinal cord through 2 tracts (pathways) dorsolateral or ventromedial

Question 27

Dorsolateral (pyramidal tract)

Answer 27

• originate from primary motor cortex, surrounding areas and red nucleus (small area of midbrain primarily responsible for control of arm muscles)
• in “pyramids” of medulla, axons cross over to opposite side of spinal cord
• controls movement in our body’s periphery: hands, fingers, toes
• damage here means loss of fine movements

Question 28

Ventromedial tract

Answer 28

• includes axons from the primary and supplementary motor cortex and other areas of the cortex
• Go to both sides of the spinal cord because axons control bilateral movement of the neck, shoulders, trunk, large leg muscles (can move the fingers on one hand independently, but can’t just turn one side of your neck or walk with one leg)
• damage here impairs walking, turning, bending, standing up and sitting down
• **most movements require a combination of both the dorsolateral and ventromedial tracts (throwing a ball)

Question 29

Role of Cerebellum [info dump]

Answer 29

• Also very important for motor control
• Has more neurons than rest of brain
• Processes information about guiding movement, not the movement itself

Damage causes:

• Difficulty with sequences that require accurate aiming and timing, e.g., tapping rhythm, speaking, writing, playing musical instrument
• Difficulty with finger-to-nose task: initial rapid movement may strike face or hold segment of task may waver
• Clumsiness, slurred speech, inaccurate eye movements
• Since this is an area that alcohol typically affects first, these are good tests of intoxication!

Question 30

Cellular Organization in Cerebellum [placeholder]

Answer 30

• Receives input from the spinal cord, each of the sensory systems, and from the cortex
• All this info eventually reaches the cerebellar cortex (surface of the cerebellum)

Question 31

Purkinje cells

Answer 31

• are very flat and exist in sequential planes

Question 32

Parallel fibers

Answer 32

• are perpendicular to the planes of the Purkinje cells
• Action potentials in parallel fibers excite one Purkinje cell after another
• Then Purkinje cells send messages to the nuclei of the cerebellum (clusters of cell bodies at the bottom of the cerebellum)
• This works to control the timing of a movement (the more Purkinje cells excited, the longer the duration of the behavioral response)

Question 33

Role of Basal Ganglia [placeholder]

Answer 33

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Question 34

Basal ganglia

Answer 34

: group of large subcortical structures in the forebrain

• caudate nucleus and putamen receive sensory input from thalamus and cortex
• globus pallidus sends information to the thalamus where it goes on to the motor and premotor cortices
• As a whole they store 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)

—> OCD has been linked to increased activity of the BG – one theory is that this area may be responsible for habit formation, and so perhaps over activity is linked to excessively strong, life-dominating habits

Question 35

Parkinson’s Disease

Answer 35

Symptoms include:

• Some cognitive slowing
• some depression
• Most defining symptoms: rigidity, muscle tremors, slow movements and difficulty initiating physical and mental activity
• Onset typically after age 50, strikes about 1% of population
• Gradual progressive death of neurons especially in the substantia nigra, an area of the brain that sends dopamine axons to the caudate nucleus and putamen

—> Symptoms begin when neurons decrease 20%-30%

—> decrease in dopamine results in decreased excitation of motor involved areas of the brain

Question 36

Substantia nigra

Answer 36

• an area of the brain that sends dopamine axons to the caudate nucleus and putamen

Question 37

Parkinson’s Disease cont.

Answer 37

Possible Causes:

• Genetics appear to play a small role

—> 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 as to why, though

—> Certainly don’t start smoking to lessen your chances of getting Parkinson’s!!!

Question 38

Treatment for Parkinson’s

Answer 38

• Most common treatment – L-Dopa
• If we know Parkinson’s results from a DA deficiency, then we need to restore the missing DA. But DA can’t cross the blood brain barrier, so they got creative
• L-Dopa is a precursor for dopamine that crosses blood-brain barrier
• Once in the brain, neurons convert it to DA
• 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

Question 39

Other Treatment for Parkinson’s

Answer 39

One or more of following usually combined with L-Dopa:

• drugs: e.g., dopamine receptor stimulants, drugs that decrease apoptosis,
• electrical or surgical destruction of globus pallidus (tends to blocks the tremor, but very risky)
• neurotrophins to promote growth of remaining neurons
• cell transplants

—> most successful with substantia nigra cells transplanted from rat fetuses into young rats

—> slight benefits with human fetal brain transplants to patients

—> neurotrophins (even from pigs) may help if researchers can get them past blood-brain barrier

Question 40

Huntington’s Disease

Answer 40

• Severe neurological disorder striking 1 in 10,000
• Extensive damage to caudate nucleus, putamen, and globus pallidus, and some in the cerebral cortex from severe neuronal degeneration
• Symptoms most often appear between 30-50 years
• Earlier the onset, the worse the progression, eventually this will kill you

—> 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

—> No known treatments 

Question 41

Huntington’s Disease

Answer 41

Cause: dominant gene. If one of your parents has it, you have a 50% chance of getting it.

• Would you want to know or not know? A Presymptomatic Test can look at your genes and let you know with almost perfect accuracy whether or not you will get it
• The gene produces a protein, which attaches to certain neurons and destroys them