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86 terms

Chapter 13 Spinal cord and Nerves

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List two enlargements
Cervical and Lumbar
Conus Medullaris
End of a spinal cord that ends between the 1st and 2nd lumbar vertebrae in adults
Filum Terminal
Extension of pia mater that extends from the conus medullaries and anchors the spinal cord to the coccyx
Cauda Equina
"Horse's Tail" Formed from the ventral nerved roots that supply the lumber, sacral, and coccygeal regions
Sympathetic Chain Ganglia
Communication point for the two motor neurons in the autonomic nervous system
Sympathetic Chain Ganglia
Located on both sides of the vertebral bodies and are part of the motor division of the autonomic nervous system
Epidural Space
Located between the vertebrae and the duramater; Composed of adipose and blood connective tissue
Dura Mater
Most superficial covering of the spinal cord; composed of dense irregular connective tissue
Subdural Space
Between the dura mater and arachnoid mater; contains interstitial fluid
Arachnoid Mater
Composed of web-like collagen and elastic fibers; is deep to the dura mater
Subarachnoid Space
Deep to the arachnoid mater and contains cerebrospinal fluid
Pia Mater
Thin layer of collagen fibers, elastic fibers and blood vessels that touches the spinal crd
Denticulate Ligaments
Thickenings of the pia mater that stabilize the spinal cord and attach it to the arachnoid mater
Anterior Median Fissure
Deep, wide groove on the anterior (ventral) side
Posterior Median Sulcus
Shallow groove on the posterior side
Gray Mater
Shaped like a butterfly
Gray Matter
Contains interneurons and is the site of integration
Posterior Horns (Dorsal)
Contains axons from the somatic and autonomic sensory neurons
Lateral Gray Horns
Only present in the thoracic and upper lumber regions; contain autonomic preganglionic motor neuron cell
Anterior (Ventral) Horns
Contain the cell bodies of somatic motor neurons and autonomic preganglionic motor neurons
Gray Commissures
Allows communication between the right and left horns
Central Canal
Located within the grey commisure
Central Canal
Small space extending the length of the spinal and is filled with CSF
White Mater
arranged in columns contains ascending sensory and descending motor tracts, which are bundles of axons in the CNS
Sensory (ascending) Tracts
consists of axons that conduct nerve impulses toward the brain
Motor (descending) Tracts
Axons that carry nerve impulses from the brain
Anterior (Ventral) White Columns
Contain tracts involved with spinal cord reflexes
Posterior (Dorsal) White Columns
Ascending sensory tracts for touch, pressure, vibration and voluntary proprioception
Lateral White Columns
Contain both sensory and motor tracts
White Commisure
Allows communication between the right and left anterior columns
Dorsal (Sensory) Root Ganglia
Cell bodies of unipolar sensory neurons
Dorsal (Posterior) Roots
Carry information from the PNS to the CNS
Ventral (Anterior) Roots
Carry information from the CNS-Effector structures
Spinal Nerves
Connect the CNS to the sensory receptors, muscles and glands in all parts of the body
Spinal nerves have
31 pairs
Cervical
C1-C-8
Thoracic
T1-T12
Lumbar
L1-L5
Sacral
S1-S5
What makes up the spinal nerve
Cervical, Thoracic, Lumbar, Sacral, and the Coccygeal
Connective tissue coverings
Each spinal and cranial nerve consists of many individual axons and contains layers of protective __________________.
Endoneurium
Innermost layer; wrap individual axons within a nerve, whether myelinated or unmyelinated
Perineurium
Middle layer; wraps a group of axons with their endoneirium arranged in bundles called fascicles
Epineurium
Outermost covering over the entire nerve
Rami
Branches of the spinal nerve
Posterior Ramus
Dorsal
Anterior Ramus
Ventral
Plexuses
Network of axons from the anterior rami of spinal nerves, except for thoracic nerves T1-T11 form plexuses
Cervical Plexus
Formed by anterior rami of C1-C5
Phrenic Nerves
Important nerves from the cervical plexuses; supply the skin and muscles of the head, neck and superior part of the shoulders and chest
Brachial Plexus
Formed by the anterior rami of C5-C8 and T1; supply the shoulders and upper limbs
Brachial Plexus
Roots --> Trunks --> Divisions --> Cords --> Branches
Important nerves that arise from the brachial plexuses
Axillary, Musculocutaneous, Radial, Median, and Ulnar Nerve
Duchenne Palsy
"Waiter's Tip" Loss of sensation along the lateral side of the arm
Wrist Drop
Inability to extend the wrist and fingers
Median Nerve Palsy
Numbness, tingling and pain in the palm and fingers
Ulnar Nerve Palsy
Inability to abduct or adduct fingers
Winged Scapula
Arm cannot be abducted beyond the horizontal position
Lumbar Plexus
Formed by the anterior rami of L1-L4; supplies the anterolateral abdominal wall, external genitals, and part of the lower limbs
Sacral Plexus
Formed by the anterior rami of L4-L5 and S1-S4; supplies the buttocks, perineum, and lower limbs
Sciatic Nerve
Largest nerve in the body; formed by rami L4-L5 and S1-S4
Coccygeal Plexus
Formed by the anterior rami of S4-S5 and the coccygeal region
Dermatome
Area of the skin that provides sensory input to the CNS via one pair of spinal nerves or the trigeminal nerve serves most of the skin of the face and scalp
Sensory and Motor Tracts
Begins and ends on the white matter
Anterior Corticospinal Tract
Located in the anterior white column; Begins in the cerebral cortex (region in the brain) and ends in the spinal cord
Reflex
Autonomic, sudden, involuntary response to a stimulus
Somatic Reflex
Involve skeletal muscle effectors
Autonomic Reflexes
Involve smooth muscle; cardiac muscle or glands
Reflex Arc
Pathway followed by nerve impulses that produce a reflex
Monosynaptic Reflex Arc
Only one synapse within the gray mater of the CNS
Polysynaptic Reflex Arc
More than one synapse with the gray matter of the CNS
Ipsilateral
reflex when the signal passes from one side to the same side of the spinal cord, the SAME SIDE
Contralateral
Reflex when the signal passes from one side to the opposite side of the spinal cord, OPPOSITE SIDE
A reflex arc includes a
Sensory receptor, Sensory neuron, Integrating center, Motor neuron and Effector
Sensory Receptor
Responds to internal / external stimulus by producing a graded potential that triggers an action potential
Sensory Neuron
Carry the action potential from the receptor to the gray matter of the spinal cord
Integrating Center
One or more regions of gray matter in the CNS composed of interneurons
Motor Neuron
Carries action potentials out of the CNS to the effector organ
Effector
A muscle or gland
Stretch Reflex
Contraction of the skeletal muscle in response to stretching of the muscle; Monosynaptic reflex, ipsilateral; Patellar or knee-jerk reflex
Stretch Reflex
Stretching of a muscle--> activation of muscle spindles--> sensory neurons--> spinal cord--> motor neuron--> contraction of the agonist muscle & relaxation of the agonist muscle
Tendon Reflex
Controls muscle tension by causing muscle relaxation when muscle tension is great
Tendon Reflex
Golgi tendon organs--> tension applied to the tendon--> tendon organ stimulation--> sensory neuron carries information to the gray matter--> integration in the gray matter occurs-->motor neuron carries signal to effector; one motor neuron relaxes the agonist and the other motor neuron causes contraction of the agonist
Flexor (withdrawal) Reflex
Stepping on a tack (stimulus)--> sensory neuron carries signal to spinal cord--> activation of the interneuron to different spinal cord segments--> activation of the motor neuron in several segments of the spinal cord--> muscle contraction--> withdrawal of the leg
Crossed Extensor Reflex
Contraction of the muscles that extend joints in the opposite limb in response to a painful stimulus
Crossed Extension Reflex
Stepping on tack--> Nerve impulse--> Activation of several interneurons--> activation of the motor neurons--> muscle contraction causing flexion of the leg stepping on a tack and extension on the opposite side