Term
| The Nervous System & Basic Nerve Functions: |
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Definition
Central nervous system (CNS)
A. Brain
B. Spinal cord
II. Peripheral nervous system (PNS)
A. Cranial nerves (12 pairs)
B. Spinal nerves (31 pairs)
III. Autonomic nervous system
A. Sympathetic
B. Parasympthetic |
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Definition
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. |
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Definition
Situated in anterior horns of spinal cord
Dendrite 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 |
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Definition
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. |
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Definition
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. |
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Term
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Definition
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 – a collection of cell bodies |
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Definition
31 pairs – exit both sides of the vertebral column
8 Cervical
12 Thoracic
5 Lumbar
5 Sacral
1 Coccyx
Table 4.1 outlines spinal innervation patterns |
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Definition
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. |
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Definition
Threshold level is the minimum level of stimulus (chemical transmitter) necessary to initiate or propagate a signal.
Facilitation – an excitatory stimulus
Inhibition – an inhibitory stimulus
Stimulus may be from more than one neuron
The sum total of excitatory and inhibitory determine impulses determine if the postsynaptic neuron will produce an action potential. |
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Definition
Consists of a single motor neuron and all the muscle fibers its axon supplies
All muscle fibers in a motor unit are of the same muscle fiber type |
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Definition
Vary widely in the number of muscle fibers.
Gastrocnemius: 2,000 or more muscle fibers per motor unit.
Eye muscles: may have fewer than 10 fibers per motor unit.
A small ratio of muscle fibers to motor neurons is capable of more precise movements.
Size of the motor unit has a direct bearing on the precision of movement. |
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Term
| How do they adjust to such extremes? |
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Definition
Number of motor units that are activated.
Frequency of stimulation. |
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Definition
| : If the stimulus is of threshold value, all muscle fibers of the motor unit will contract. |
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Definition
has an orderly sequence:
Smaller slow twitch fibers are recruited first.
They have lower thresholds
Larger fast twitch fibers are recruited later.
They have higher thresholds |
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Term
| Gradiation in The strength of muscle contractions |
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Definition
At low frequency stimuli, muscle fibers relax between impulses.
At high frequency stimuli, fibers do not have time to relax and result in summation or maximal contraction.
A combination of maximum number of fibers stimulated and high frequency of stimuli results in a maximal strength of contraction. |
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Definition
Respond to different stimuli
Exteroceptors: near body surface stimuli come from outside the body.
Interoceptors: sense heat, cold, pain and pressure. |
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Definition
Stimulated by body movements.
Transmit information to CNS.
Two primary categories:
Muscle receptors
Joint & skin receptors |
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Definition
Located in muscle belly, parallel with fibers.
When stretched, sensory nerve sends impulses to CNS, which activates the motor neurons facilitating contraction of the same muscle.
More spindles are located in muscles controlling precise movements. |
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Term
Extrafusal fibers
Intrafusal fibers |
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Definition
"regular muscle fibers
muscle fibers inside spindles |
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Term
| Primary or annulospiral endings |
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Definition
coiled around noncontractile midsection.
Sensitive to velocity of change (phasic).
Sharp decline in impulses with static change. |
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Definition
at end of noncontractile midsection.
Respond to static muscle length.
Impulses directly proportional to change in length |
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Definition
| stimulate the intrafusal fibers to contract, shortening the muscle spindle. |
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Definition
Embedded “in series” in the tendon.
As tension in tendon increases GTO is activated.
Signals CNS to relax muscle.
Protective mechanism. |
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Definition
In regions around joint capsules, ligament, and tendons sheaths.
End-organ has concentric layers of capsule.
Activated by joint angle changes & pressure.
Transmits impulses for only a very brief time. |
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Definition
In deep layers of skin and joint capsule.
Activated by mechanical deformation.
Stimulated strongly by sudden joint movement.
Sense joint position and changes in joint angle.
The CNS knowing which receptors is stimulated can tell the joint angle. |
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Term
Cutaneous Receptors
- Meissner corpuscles
- Pacinian corpuscles
- Free nerve endings |
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Definition
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Definition
| Concerned with sense of balance. |
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Definition
| sensitive to linear acceleration and head position with respect to gravity. |
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Definition
| sensitive to angular acceleration. |
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| Joint Receptors of the neck |
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Definition
| sensitive to angle between the body and the head. |
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Term
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Definition
A specific pattern of response without volition from the cerebrum.
Stimulus - receptor organ - sensory neuron - motor neuron - muscle (response)
Connector neurons often used. |
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Term
| Exteroceptive Reflexes Extensor Thrust Reflex |
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Definition
Stimulus - pressure.
Receptor -Pacinian corpuscles.
Response - contraction of the extensor muscles of that limb. |
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Definition
Stimulus - pain, noxious stimuli.
Receptor - free nerve endings.
Response - Quick withdrawal from source of pain (flexion). |
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Definition
Stimulus - flexor reflex or unweighting
Response - opposite extensors contract for support. |
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Term
| Proprioceptive Reflexes Stretch Reflex |
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Definition
| A reflex contraction of stretched muscle and synergists and relaxation of antagonists. |
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Term
| Stretch Reflex - Phasic Responses |
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Definition
Stimulus - high velocity stretch.
Receptor - annulospiral endings of muscle spindle.
Response - facilitates proportional contraction of stretched muscle. |
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Term
| Stretch Reflex - Tonic Response |
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Definition
Tonic Response:
Stimulus - Slow, sustained stretch(>.02 s).
Receptor - flower spray endings of muscle spindle.
Response - gamma efferent system resets spindle tension using intrafusal fiber contraction or relaxation. |
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Term
| Stretch Reflex - Phasic Response Application |
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Definition
Phasic preparatory phase can take advantage of the stretch reflex.
Results in a stronger contraction.
Postural control feedback. |
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| Stretch Reflex - Tonic Response Application |
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Definition
Slow preparatory phase should be used when the desired outcome is accuracy.
Result in a low level, sustained contraction. |
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Definition
Stimulus - high level of stretch, due to muscle stretch, or muscle contraction.
Receptor - Golgi tendon organ.
Response - relaxation of stretched muscle and facilitation of antagonist.
Feedback mechanism to control tension.
May effect skills of beginners until GTO threshold develops. |
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Definition
Stimulus - head not upright with respect to gravity.
Receptor - utricle and semicircular canals.
Response - bring the head to the upright position. |
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Definition
Symmetrical response:
Stimulus - head/neck(H/N) flexion/hyperextension.
Receptor - neck receptors.
Response - H/N flexion facilitates upper extremity flexion; H/N hyperextension facilitates upper extremity extension. |
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| Tonic Reflex Response - Asymmetrical Response |
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Definition
Stimulus - head/neck rotation.
Receptor - neck receptors.
Response - H/N rotation facilitates upper extremity chin side abduction & extension; back of head side adduction and flexion. |
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Definition
| where consciousness occurs, initiation of voluntary movement. |
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Definition
| responsible for homeostasis, coordination & some learned acts of posture. |
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Definition
| key role in sensory integration, regulates timing & intensity of muscle contraction. |
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Definition
| arousal and monitoring of physiological parameters, key facilitory and inhibitory centers. |
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Definition
| contains cell bodies of lower motor neurons, common pathway between CNS & PNS, final point for integration and control. |
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Definition
| predominately axons of motor neurons, controls muscles for precision. |
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Definition
| synapses with all levels of CNS, functions in stabilization and control of posture. |
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Definition
| synapses with all levels of CNS, functions in stabilization and control of posture. |
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Term
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Definition
The conscious awareness of position of body parts and the amount and rate or joint movement.
Without rapid transmission & processing, accurately controlled movements could not proceed.
Kinesthetic perception and memory are the basis for voluntary movement and motor learning. |
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