Term
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Definition
bundles of axons in CNS
Nerve impulse “highways” between spinal cord and brain |
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Term
| Sensory (ascending) tracts |
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Definition
| consist of axons that conduct nerve impulses toward the brain |
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Term
| Sensory (ascending) tracts |
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Definition
Keep CNS informed of changes in external and external environment; this information is integrated or processed by interneurons in spinal cord and brain
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Term
| Motor (descending) tracts |
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Definition
| consist of axons that carry nerve impulses away from the brain |
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Term
| Motor (descending) tracts |
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Definition
Responses to integrative decisions are brought about by motor activities (muscular contractions and glandular secretions)
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Term
| White matter of spinal cord |
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Definition
| contains both sensory and motor tracts |
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Definition
| sensory (ascending) tract that conveys nerve impulses for sensing pain, warmth, coolness, itching and tickling to CNS |
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Definition
| motor (descending) tract that conveys nerve impulses that originate in brain and are destined to cause voluntary movements of skeletal muscles |
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Term
| White matter of spinal cord |
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Definition
| cord contains sensory and motor tracts, the “highways” for conduction of sensory nerve impulses toward the brain and motor nerve impulses from the brain toward effector tissues |
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Term
| Gray matter of spinal cord |
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Definition
| cord is a site for integration (summing) by interneurons of incoming excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs) |
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Term
| Spinal nerves and the nerves that branch from them |
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Definition
| connect the CNS to the sensory receptors, muscles, and glands in all parts of the body |
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Definition
| is a fast and automatic involuntary response to a specific stimulus |
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Definition
| pulling hand away from hot surface |
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Definition
| slam on car brakes during emergency |
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Definition
involves spinal cord gray matter
Patellar (knee-jerk) reflex
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Term
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Definition
involves brain stem
Tracking movements of eyes while reading
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Term
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Definition
| involves contraction of skeletal muscles |
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Term
| Autonomic (visceral) reflex |
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Definition
| involves unconscious responses of smooth and cardiac muscle, and glands |
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Term
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Definition
| pathway followed by nerve impulses that produce a reflex. |
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Term
| 5 Components of a reflex arc |
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Definition
1. Sensory receptor
2. Sensory neuron
3. Integrating Center
4. Motor Neuron
5. Effector |
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Term
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Definition
distal end of a sensory neuron (dendrite) or an associated sensory structure
Detects/responds to specific stimulus (change in internal or external environment)
Produces a graded potential – if it reaches threshold it will trigger nerve impulse in sensory neuron
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Term
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Definition
| sends nerve impulse along its axon to the integrating center |
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Term
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Definition
located in gray matter of CNS
Brainstem: for cranial reflexes
Spinal Cord: for spinal reflexes
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Term
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Definition
| only one synapse between sensory and motor neuron (no interneurons) |
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Definition
| interneurons occur between sensory and motor neurons, more than one synapse involved |
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Definition
| Sends nerve impulse away from integrating center to effectors |
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Definition
part of the body that produces response
Skeletal muscles in somatic reflex
Cardiac or smooth muscles or glands in autonomic reflex
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Term
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Definition
Causes contraction of a skeletal muscle in response to stretching of the muscle.
Helps maintain posture
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Term
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Definition
| sensory nerve impulses enter the spinal cord on the same side from which motor impulses leave it (entire reflex arc on same side of body) |
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Term
| Patellar or knee-jerk reflex |
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Definition
| : Stretching of quadriceps femoris muscle →activation of sensory receptors →sensory neuron →spinal cord→motor neuron → contraction of quadriceps femoris muscle. |
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Term
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Definition
| contraction of flexor muscles moves a limb away from source of possible damaging stimulus |
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Term
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Definition
nerve impulses from one sensory neuron ascend and descend in spinal cord and activate interneurons in several segments of spinal cord
Allows stimulation of more than one effector e.g. to move an entire upper or lower limb involves contraction of several limb muscles!
Stepping on a tack (stimulus) → activation of sensory receptor → nerve impulse → activation of several interneurons → activation of motor neurons →muscle contraction of flexor muscles→withdrawal of the leg.
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Term
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Definition
| Damage or disease anywhere along a reflex arc can cause a reflex to be |
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Definition
absence of this somatic reflex could mean damage of motor or sensory neurons, or spinal cord injury in 2nd, 3rd or 4th lumbar segments of spinal cord
Often absent in people with chronic diabetes mellitus
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Term
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Definition
somatic reflex where great toe dorsiflexes to gentle stroking of lateral outer margin of sole
Normal for children under 18 mos. of age
Abnormal after 18 mos. of age: damage to corticospinal tract
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Definition
| curling under of all toes |
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Definition
autonomic reflex where pupils of both eyes decrease in diameter when either eye is exposed to light
Absence indicates brain damage or injury
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Term
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Definition
Spinal cord injury outcomes range from little to no long-term effects to paralysis or even death.
Most spinal cord injuries are due to trauma as a result of automobile accidents, falls, contact sports, diving, or acts of violence
Effects of injury depend on extent of direct trauma to spinal cord or compression of the cord by fractured or displaced vertebrae or blood clots.
Common sites of injury are in cervical, lower thoracic and upper lumbar regions
Patients may have improved outcome if an anti-inflammatory corticosteroid is given within 8 hrs of injury
Decreases edema (collection of fluid in tissue) due to immune response to injury |
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Term
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Definition
spinal cord is severed from one side to another
Cuts all sensory and motor tracts
Loss of all sensations and voluntary movement below level of transection
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Term
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Definition
| quadriplegic; ventilator needed for breathing |
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Term
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Definition
| quadriplegic, can breathe |
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Definition
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Definition
| most thigh muscles can be used; walk with long leg braces |
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Definition
| most leg muscles can be used; walk with some assistance |
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Term
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Definition
Stretch reflex pathway is monosynaptic, however a polysynaptic reflex arc to the antagonistic muscles operates at the same time
Three neurons and two synapses
Inhibitory interneuron inhibits a motor neuron that would normally excite antagonistic muscles
Prevents conflict between opposing muscles and is vital in coordinating body movements
Axon collaterals of sensory neuron also relay nerve impulses to the brain over specific ascending tracts
Brain receives input of stretch or contraction of skeletal muscles, enables it to coordinate movements
Allows conscious awareness that the reflex has occurred.
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