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Chapter 6: Movement
Three Kinds of Muscle Fibers
1.
Smooth
2.
Skeletal (striated)
3.
Cardiac
More about Fibers
1.
Each muscle in our bodies is made up of
thousands of muscle fibers
2.
A motor neuron may innervate several
hundred individual fiber or just a few fibers


What would you guess about differences in
muscular control between these two types of
innervation?
Where do you think you might see small
innervation ratios vs. larger ratios?
Relationship of Muscles to Each Other
1.
Antagonistic pairs


Consists of a flexor muscle and an extensor
muscle
Biceps and triceps are the best example
Antagonistic Pair
Neurotransmitter Control of Muscles
1.
Neuromuscular junctions
2.
Neurotransmitter: acetylcholine (ACh)
3.
ACh release always causes a muscular
contraction
Slow and Fast Twitch Fibers
1.
2.
Some animal species have separate ‘speeds’ of
muscles
Humans have different speeds of fibers as well, but
they aren’t distinct groups


Fast twitch fibers = anaerobic running
Slow twitch fibers = aereobic  talking
How do muscles ‘know’ what they are
doing?
1.
Our old friend the proprioceptor
2.
These receptors control muscular reflexes
3.
There are two kinds of proprioceptors:


muscle spindle
Golgi tendon organ
Proprioceptors
Types of Movement
1.
Voluntary movement
2.
Involuntary or reflexive movements


3.
You are born with at least 10 reflexive
Ballistic movements
A motor program is a sequence of coordinated,
separate movements that occur together – animals
and humans both have them
Movement in the Cortex


Primary motor cortex
is used to direct
voluntary, complex
movements
Just like with the
somatosensory cortex,
there is a map of the
body on the cortex
Other areas in the Cortex


premotor
cortex
supplementary
motor cortex
From the Brain to the Cord
1.
There are two distinct tracts of information
running through the spinal cord


Dorsolateral tract
Ventromedial tract
2.
Most movements require activity of both tracts
3.
Cross-over (for contralateral control) occurs in the
brainstem
The Cerebellum
1.
The cerebellum (where is that again??) 
coordination
2.
Rats with cerebellar damage would have a hard
time grooming itself, humans…
The Basal Ganglia
1.
2.
3.
The basal ganglia are a group of subcortical
forebrain structures
These structures are also involved in deciding
when and when not to move
People with OCD have over-activity in the basal
ganglia = may be involved in habit formation
 More notes in class following group activity.