Cervical Plexus
receives fibers from the anterior rami of nerves
C1-C5
Cervical Plexus Nerves
- lesser Occipital
- Great Auriculuar
- Transverse Cervical; Ansa Cervicalis
- Supraclavicular
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PHRENIC
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Brachial Plexus
C5-T1
innervates the pectoral girdle and upper limbs
Brachial Plexus Nerves
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BRACHIAL PLEXUS
passes over the 1st rib into the axilla and innervates the upper limbs and some of the muscles of the neck and shoulder
Lumbar Plexus Vertebrae
L1-L4 & T12
Lumbar Plexus Nerves
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Lumbar Plexus
innervates the hip and femur (upper/ inner leg)
Sacral & Coccygeal Plexus Vertebrae
Sacral- L4, L5, S1-S4
Coccygeal- S4, S5, Co1 (list of vertebrae)
Sacral and Coccygeal Nerves
- Superior Gluteal
- Inferior Gluteal; Posterior Cutaneous
- Tibial
- Fibular (Peroneal)(Common, deep, superficial)
- Pudendal
Sciatic Nerve
- nerve extending from the base of the spine down the thigh, lower leg, and foot; formed by the tibial and fibular nerves
Dermatome map
a diagram of the cutaneous regions innervated by each spinal nerve
Somatic Reflexes
unlearned skeletal muscle reflexes mediated by the brainstem and spinal cord
Reflex Arc
Stimulus, sensory, synapse, motor, response
Reflex Arc- Stimulus
somatic receptors in skin, muscles, and tendons are activated
Reflex Arc- Sensory
Afferent nerve fibers carry information from receptors to the brain stem
Reflex Arc- Synapse
integrating center; point of synaptic contact between neurons in the gray matter of the brain and spinal cord
Reflex Arc- Motor
Efferent fibers carry motor impulses to the muscles
Reflex Arc- Response
effectors (muscles that carry out the response to the initial stimulus) are activated
Afferent Fibers
carries sensory signals from receptors to the CNS (posterior nerve fibers)
Efferent Fibers
Carries motor signals from CNS to effectors (anterior nerve fibers)
Somatic Fibers
Innervate the skin, muscles, bones, and joints (voluntary control of limbs)
Visceral Fibers
innervate blood vessels, glands, and viscera
General Fibers
innervate widespread organs such as muscles, skin, glands, viscera, and blood vessels
Special Fibers
innervate more localized organs in the head, including the eyes, ears, olfactory and taste receptors, and muscles of chewing, swallowing, and facial expression
Ganglion
A cluster of nerve cell bodies, often of similar function, located in the PNS (cluster of
neurosomas
outside the CNS)
Meningial Branch
innervation of meninges, vertebrae, and spinal ligaments
Posterior Rami
innervation of muscles and skin of the back and vertebral column
Communicating Rami
converge on sympathetic chain ganglia (T1-L2) (anterior rami)
Intercostal Nerves
innervates skin, intercostals, obliques and transverse abdominals (T1-T12) (anterior rami)
Plexuses
converging and branching nerve fibers (anterior rami)
Sympathetic Chain Ganglia
deliver information to the body about stress and impending danger, and are responsible for fight-or-flight response.
Meninges
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Dura Mater
thick, outermost layer of the meninges surrounding and protecting the brain and spinal cord
Arachnoid Mater
weblike middle layer of the three meninges
Pia Mater
the thin, delicate innermost membrane enveloping the brain and spinal cord.
Anterior Median Fissure
a groove along the anterior midline of the spinal cord that incompletely divides it into symmetrical halves
White Matter
surrounds the gray matter, consists of bundles of of axons that course up and down the cord and provide avenues of communication between different levels of the CNS
Ascending Tracts
carry sensory information up the spinal cord to the brain
First Order Neuron
detects a stimulus and transmits a signal to the spinal cord or brainstem
Second Order Neuron
continues as far as a "gateway" called the thalamus at the upper end of the brainstem
Third Order Neuron
carries the signal the rest of the way to the sensory region of the cerebral cortex
Gracile Fasciculus
carries signals from the midthoracic and lower parts of the body; consists of first order nerve fibers that travel up the ipsilateral side of the spinal cord and terminate at the
gracile nucleus
in the medulla oblongata of the brain stem
Proprioception
nonvisual sense of the position and movements of the body
Cuneate Fasciculus
joins the gracile at the T6 level; occupies the lateral portion of the posterior column and forces the gracile fasciculus medially; fibers end in
cuneate nucleus
on the ipsilateral side of the medulla oblongata
Spinothalmic Tract
Has sensory fibers that transmit the sensations of pain, temperature, and light touch
Spinoreticular Tract
carries pain signals resulting from tissue injury
Posterior and Anterior Spinocerebellar tracts
travel through the lateral column and carry proprioceptive signals from the limbs and trunk to the cerebellum at the rear of the brain; non-conscious proprioception (joint position)
Descending Tracts
carry motor commands to spinal cord
corticospinal tract
carry motor signals from the cerebral cortex for precise, finely coordinated limb movements
tectospinal tract
reflex turning of head in response to sights and sounds
lateral and medial reticulospinal tracts
control muscles of upper and lower limbs, especially those for posture and balance
lateral and medial vestibulospinal
begin in the brainstem vestibular nuclei, which receive signals for balance from the inner ear
nerve
cordlike structure made up of fibers that carries impulses from one part of the body to another
Schwann Cells
Type of glia in the PNS, Supporting cells of the peripheral nervous system responsible for the formation of myelin.
Structures of a Nerve Cell
nerve fiber - Endoneurium - fascicle - perineurium - Epineurium (structures of a nerve cell)
sensory nerves
composed only of afferent fibers, are rare; include olfactory and optic nerves
Motor Nerves
carry only efferent fibers
Mixed Nerves
nerves carrying both sensory and motor fibers
ipsilateral
on the same side of the body as another structure
intercostal nerve
Travels along the inferior margin of a rib and innervates the skin and intercostal muscles; thus contributing to breathing.
muscle spindles
receptors sensitive to change in length of the muscle and the rate of that change; informs the brain of muscle length and body movements; contribute to proprioception
intrafusal fibers
the muscle fibers found within a muscle spindle; near tendon, enclosed in fibrous sheath
extrafusal fibers
regular muscle fibers
Gamma Motor Neurons
maintain tension in muscle spindles
sensory nerve fibers
react to heat, cold, touch, pressure, and pain. these sensory receptors send messages to the brain
Alpha motor Neurons
innervate extrafusal muscle fibers (working part of the muscle)
primary sensory nerve fibers
length and rate of change; Synapse with alpha motor neurons in posterior horn
secondary sensory nerve fibers
length only; Synapse with alpha motor neurons in posterior horn
Stretch reflex
myotatic; helps maintain equilibrium and posture
reciprocal inhibition
reflex phenomenon that prevents muscles from working against each other by inhibiting the antagonist (Antagonists relax)
monosynaptic reflex arc
when the primary afferent fibers synapse directly with the alpha motor neurons that return to the muscle
-ex: knee jerk reflex: when patellar tendon is stretched w/ reflex hammer, info travels up the sensory neuron to the spinal cord where it interfaces w/ the motor neuron that contracts the quadriceps muscles
flexor (withdrawal) reflex
the quick contraction of flexor muscles resulting in the withdrawal of a limb from an injurious stimulus
postsynaptic reflex arc
pathway in which signals travel over many synapses on their way back to the muscle
crossed extension reflex
contraction of extensor muscles in the limb opposite from the one that is withdrawn
ex. when you step on a lego, your immediate reflex is to lift up the foot that stepped on it,
in order to maintain balance your opposite leg must flex and keep you upright
contralateral reflex arc
one in which the input and output are on opposite sides
(crossed extension reflex)
REFLEX ARC
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