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Transcript
Neural Control
of Movement
Chapter 2
CENTRAL NERVOUS SYSTEM
• Brain
–Cerebral Cortex/Cerebrum
• Motor cortex
–Basal Ganglia/Diencephalon – sensory input
–Cerebellum – motor control
–Brain stem – sensory input
• Spinal Cord
CENTRAL AND PERIPHERAL
NERVOUS SYSTEM
• Central nervous system
• Peripheral nervous system
PERIPHERAL NERVOUS SYSTEM
• Somatic
–Sensory (Afferent) Neuron
–Motor (Efferent) Neuron
• Autonomic [FYI]
– Parasympathetic
– Sympathetic
SENSORY
NEURONS
• Carry impulse towards the CNS
Towards CNS
MOTOR NEURONS
•Carry impulse away from the CNS (e.g. motor
nerves)
•Stimulatory
•Inhibitory
Spinal Nerves
Cervical spinal nerves (C1 to C8)
These nerves (eight pairs) supply the
back of the head, the neck and
shoulders, the arms and hands, and
the diaphragm.
Thoracic spinal nerves (T1 to T12)
These nerves (12 pairs) supply the
chest, some muscles of the back, and
parts of upper abdomen.
Lumbar spinal nerves (L1 to L5)
These nerves (five pairs) supply parts
of the lower abdomen and the back.
Sacral spinal nerves (S1 to S5)
These nerves (five pairs) supply the
thighs and parts of lower legs, and
the feet.
NEURON ANATOMY
• Dendrite
• Cell Body
• Axon
NEURON
ANATOMY
Neuron
…a single nerve cell
Nerve
….a bundle or group of neurons
A nerve contains both motor and sensory
neurons
Proprioception and
Kinesthesis
•
•
•
•
What is kinethesis?
…awareness of the position and movement of the
body
What is proprioception?
…ability to regulate posture and movement by
responding to stimuli from receptors throughout
the body
MUSCLE
SPINDLES
MUSCLE
SPINDLES
Provide proprioception
Sense the amount of stretch and the
rate of stretch
Reflexes involving the muscle
spindles is how we ‘feel’ a movement
was done correctly
Spindles are a part of learning; we
develop such reflexes as we practice
skills and movements
GOLGI TENDON
ORGAN
GOLGI TENDON
Sensitive to muscle tension and active
ORGAN
contraction
Protect muscle from excess contraction
force
Stimulation of GTO an afferent impulse
is sent to the central nervous system
In turn, efferent impulses are sent to
the…
…Agonist muscle causing it to relax
Other Receptors
Proprioceptors of the joints and skin
Examples: Meissner’s corpuscles, Ruffini’s
corpuscles, Pacinian corpuscles, Krause’s
end-bulbs
NEUROMUSCULAR
CONCEPTS
Motor Unit
•
•
One motor neuron
and all the muscle
fibers it innervates
All-or-none principle
Factors Affecting
Muscle Tension
•
•
•
The number of motor units activated
Type of motor units activated (fast or slow twitch)
The frequency of stimulation of the motor units
Factors Affecting
Muscle Tension
•
Stimulation
•
•
Subthreshold stimulus
Threshold stimulus
•
•
Submaximal stimulations
Maximal stimulation
Factors Affecting
Muscle Tension
•
•
•
Twitch
Summation
Tetanus
Neuromuscular
Summary
•An example from baseball.
•A pitcher throws a curve ball to
Derrek Lee
•Derek’s eyes see the ball coming
towards him and is able to identify
the pitch as a curve ball
•Sensory nerves (afferent) send that
information to the CNS
•In the CNS the sensory nerve
synapses with motor nerves
•The motor nerves in turn stimulates
the muscles (deltoid and pectoralis
major) required to swing the bat in
•
•
•
•
•
•
Neuromuscular
Summary
Inside the fibers of the deltoid and
pectoralis major, calcium is released
The calcium allows myosin heads to attach
to actin
When the heads swivel the fibers of the
deltoid muscle will shorten
The shortening of the fibers will pull on the
humerus causing Derrek to swing the bat
The muscle spindles “tell” the CNS when
the arm is in the correct position
If all goes as planned, the deltoid and
pectoralis major will move his arms into a
position to hit the ball
Neuromuscular
Summary
• An example from weight training.
• A man is having his muscular strength tested on the
bench press
• For his first lift, 50 pounds is put on the bar
• He will be using his pectoralis major muscle with has 500
motor units (300 slow twitch and 200 fast twitch) and his
triceps muscle
• His CNS stimulates 280 motor units leading to his
pectoralis major muscle (180 slow twitch and
100 fast twitch)
• Remember, each nerve ending stimulates a
separate muscle fiber
Neuromuscular
Summary
•
•
•
•
•
The pectoralis major and triceps muscles shortens and his
arm extends outward raising the bar with 50 pounds on it.
After a few minutes of rest, 100 pounds is place on the bar
This time he stimulates 380 motor units (260 slow twitch
and120 fast twitch)
The weight is successfully lifted
After a few minutes of rest, 150 pounds
is place on the bar
•
•
•
•
•
Neuromuscular
Summary
This time he stimulates 460 motor units (280 slow twitch
and 180 fast twitch)
As the pectoralis major muscle contracts the GTO in the
pectoralis major are stimulated
They stimulate a sensory nerve leading to the CNS
In the CNS, the sensory nerve synapses
with a motor nerve that will inhibit (relax)
the pectoralis major muscle
The man is unable to lift the 150 lb