Upload
docong
View
221
Download
0
Embed Size (px)
Citation preview
CHAPTER 4:THE NEUROMUSCULAR
BASIS OF HUMAN MOTION
KINESIOLOGYScientific Basis of Human Motion, 12th edition
Hamilton, Weimar & LuttgensPresentation Created by
TK Koesterer, Ph.D., ATCHumboldt State University
Revised by Hamilton & Weimar
Copyright © 2012 by The McGraw-Hill Companies, Inc. All rights reserved.McGraw-Hill/Irwin
4-2
Motor Cortex Sensory Cortex
CEREBRAL CORTEX
4-3
NEURONS
A single nerve cell consists of a cell body and one or more projections. Axons: Carry impulses away
from cell body. Dendrites: Carry impulses
toward cell body.
Fig 4.1
4-4
MOTOR NEURONS
Situated in anterior horns of spinal cordDendrite that synapses with sensory neurons
or connector neurons.Axon emerges from the spinal cord, travels by
way of a peripheral nerve to muscle. Each terminal branch ends at the motor
end plate of a single muscle fiber
4-5
SENSORY NEURONS
Situated in a dorsal root ganglion just outside the spinal cord.
Neuron may terminate in spinal cord or brain.
A long peripheral fiber comes from a receptor.
Fig 4.1b
4-6
CONNECTOR NEURONS
Exist completely within the CNS. Serve as connecting links. May be a single neuron, connecting
sensory to motor neurons.OR
An intricate system of neurons, whereby a sensory impulse may be relayed to many motor neurons.
4-7
NERVES
A bundle of fibers, enclosed within a connective tissue sheath, for transmission of impulses.
A typical spinal nerve consists of: Motor, outgoing (efferent) fibers Sensory, incoming (afferent) fibers
Each spinal nerve is attached to spinal cord by an anterior (motor) root and a posterior (sensory) root
Posterior root bears a ganglion
4-8
SPINAL NERVES
31 pairs – exit both sides of the vertebral column 8 Cervical 12 Thoracic 5 Lumbar 5 Sacral 1 Coccyx
9A-9
SPINAL COLUMN: STRUCTURE
7 Cervical Vertebrae 12 Thoracic
Vertebrae 5 Lumbar Vertebrae Sarcrum Coccyx
Fig 9.1
(7)
(12)
(5)
(5)
4-10
THE SYNAPSE Connection between neurons. May be thousands between
any two neurons. Is a proximity of the membrane
of an axon to the membrane of a dendrite or cell body.
The more often a synapse is used the faster a signal will pass through it.
The greater the number of synapses from receptor to effector, the longer the time from stimulus to response.
Transmission across the synapse depends on a chemical transmitter.
Substance diffuses the synapse and produces an action potential in the postsynaptic neuron.
4-11
MUSCLE INNERVATION
4-12
GRADATIONS IN THE STRENGTH OF MUSCULAR CONTRACTIONS
Experience tells us that the same muscles contract with various gradations of strength.
How do they adjust to such extremes?Number of motor units that are activated.Frequency of stimulation.
4-13
SENSORY RECEPTORS
Respond to different stimuliExteroceptors: near
body surface stimuli come from outside the body.
Interoceptors: sense heat, cold, pain and pressure.
Fig 4.5
4-14
PROPRIOCEPTORS
Stimulated by body movements.
Transmit information to CNS.
Two primary categories:Muscle receptors Joint & skin receptors
Fig 4.6
4-15
LABYRINTHINE SYSTEM
Utricle
Semicircular Canals
4-16
REFLEX MOVEMENT
A specific pattern of response without volition from the cerebrum.
Stimulus - receptor organ - sensory neuron -motor neuron - muscle (response)
Connector neurons often used.
4-17
PROPRIOCEPTIVE REFLEXESSTRETCH REFLEX Knee jerk response Sudden addition of weight to hand, elbow at
90°.Biceps stretches, then contracts.
Weight dropped Muscle contracts