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32 Cards in this Set
- Front
- Back
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Spinal Cord
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located within vertebral canal of vertebral column; protected by:
a) bone of vertebral column b) fat layer of epidural space c) 3 layers of meninges d) subarachnoid space filled with serebrospinl fluid |
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Meninges x 3
1) Dura Mater |
dense, fibrous outer layer of meinges
a) forms continuous tube around spinal cord 1) attached superiorly to skull at margins of foramen magnum 2) extends as tube down to S2 level of sacrum, then narrows & attaches to coccyx |
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Meninges x 3
2) Arachnoid Mater |
a) Subarachnoid space - between pia & arachnoid; filled with cerebrospinal fluid
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Meninges x 3
3) Pia Mater |
thin, innermost covering; tightly adherent to spinal cord
a) from inferior end of spinal cord, continues as thin cord, filum terminale; attaches to coccyx - anchors inferior end of spinal cord |
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Spinal Cord
(Descriptive) 1 - 3 |
1) begins at foramen magnum of skull - continuous with inferior end of brain stem
2) conus medullaris - conical tapered terminal end of spinal cord 3) dorsal and ventral roots - of spinal nerves formed by union of dorsal and ventral rootlets a) rootlets emerge continuously along lateral sides of spinal cord b) rootlets combine to form single dorsal or ventral root 1) dorsal & ventral roots join to form single spinal nerve - exits via intervertebral foramen 2) dorsal root = entering sensory axons; ventral root = exiting motor axons 3) Reminder: SAME DAVE |
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Spinal Cord
(Descriptive) 4 - 6 |
4) spinal cord approximately 18 inches long in adult - shorter than length of vertebral column
a) spinal cord & vertebral column same length in fetus b) spinal cord stops growing well before vertebral column reaches full adult length c) adult spinal cord ends at L1 - L2 vertebral level - spinal tap for CSF done below this level 5) because of length differences, spinal cord levels do not correspond to vertebral levels a) spinal nerves still exit through intervertebral foramen of vertebral column at appropriate levels b) only upper cervical spinal nerves exit horizontally c) lower spinal nerves descend obliquely within vertebral canal before exiting d) rootlets of lower spinal cord descend before joining & exiting as spinal nerve - descending nerve rootlets below end of spinal cord form cauda equina 6) two areas of spinal cord enlargement (extra neurons for innervation of limbs) a) cervical enlargement - spinal levels C5-T1 1) forms brachial plexus - innervates upper limb b) lumbosacral enlargment - spinal levels L1-S4 1) form lumbar and sacral plexuses - innervate lower limb |
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Gray Matter
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contains neuron cell bodies, dendrites, and synapses
a) centrally located in the spinal cord; divided into: 1) dorsal horn - receives axons of sensory neurons 2) ventral horn - contains neuron cell bodies of motor (somatic efferent) neurons that supply skeletal (voluntary) muscles of body 3) lateral horn - contains neuron cell bodies of preganglionic autonomic (visceral efferent) neurons; found only in T1-T2 & S2-S4 spinal cord levels |
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White matter
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myelinated axons
a) peripherally located in spinal cord b) axons are bundled together into functionally related groups called tracts - form ascending tracts (sensory information) or descending tracts (motor information) |
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Spinal Cord tracts
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1) Tracts are bilateral (one on each side of spinal cord) and precisely located within white matter - named for position within spinal cord and the brain region they connect to
a) descending tracts - carry motor information from brain to spinal cord b) ascending tracts - carry sensory information from spinal cord to brain |
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Descending Tracts
1 of 3 |
a) there are different descendig tracts for different types of motor information (fine motor control versus balance, postural, or walking motor control)
1) all systems consist of 2 neurons: a) upper motor neuron located either in the primary motor cortex of the precentral gyrus of the frontal lobe, or in the brain stem b) lower motor neuron located in the ventral horn of spinal cordgray matter |
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Descending Tracts
2 of 3 |
b) direct (pyramidal) pathways - provide for fine motor control (especially of face, hands)
1) formed by upper motor neuron axons passing from primary motor cortex of frontal lobe to lower motor neurons in spinal cord ventral horn 2) as they descend, axons from upper motor neurons pass through a) cerebral peducles of midbrain b) pyramids of medulla oblongata 3) example: corticospinal tract for fine control of hand movements (other pathways for fine motor control of head and face movements) |
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Descending Tracts
3 of 3 |
c) indirect (extrapyramidal) pathways - for unconscious control of balance & posture
1) begin with upper motor neurons in brain stem motor nucleus - project to lower motor neurons in spinal cord ventral horn 2) fibers do not pass through pyramids of medulla 3) brain stem nuclei receives inputs from motor control areas of cerebrum & cerebellum 4) includes rubrospinal, vestibulospinal, reticulospinal, and tectospinal tracts |
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Lateral Corticospinal Tract
1 of 2 |
1) Descending motor tract for fine motor control of hands, located in lateral-posterior spinal cord
2) Originates with neurons of the primary motor cortex, located in the precentral gyrus of the frontal lobe a) primary motor cortex contains distorted map (motor homunculus) of the body - foot and leg represent on medial surface of frontal lobe; rest of body represented along length of precentral gyrus b) body map is distorted - areas of body with finest motor control (hands/face) utilize the largest brain regions (fine control requires more neurons) c) primary motor cortex provides motor control for contralateral (opposite) side of body (ipsilateral = same side) |
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Lateral Corticospinal Tract
2 of 2 |
3) Axons from primary motor cortex neurons descend through white matter of cerebral hemishere as lateral corticospinal tract
a) pass through cerebral peduncles (connect cerebrum to midbrain) b) pass through midbrain and pons to medulla oblongata (within pyramid of medulla) c) pyramidal decussation - in medulla, axons cross over (decussate) to opposite side of brainstem d) axons descend in whit matter of spinal cord (within corticospinal tract) e) at appropriate level of spinal cord, axons enter gray matter and synapse onto lower motor neurons located in ventral horn (anterior horn) of spinal cord f) spinal cord motor neurons send their axons out via ventral root of spinal cord; axons then follow spinal nerve-plexus- peripheral nerve to reach target muscle g) two neuron chain for fine motor control: 1) upper motor neurons - neuron of primary motor cortex (axons descend as lateral corticospinal tract to reach spinal cord) 2) lower motor neurons - ventral horn motor neurons of spinal cord (axons travel to muscle of body) |
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Ascending Tracts - consist of 2 or 3 chain:
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a) sensory neuron - dorsal root ganglion neurons that respond to sensory stimulus
b) 1 or 2 relay neurons c) termination - brain area that receives sensory input 1) primary somatosensory cortex of parietal lobe for conscious perception of sensation 2) cerebellum for proprioception information (provide sensory feedback for control of muscle activities and body movement) 3) brainstem for reflex responses, such as blood pressure control or changes in pupil diameter d) there are different ascending tracts for different types of sensory information 1) dorsal column system - 2 point touch discrimination, pressure, vibration |
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Dorsal Column Pathway
1 of 2 |
1) Ascending general sensory tract for touch and pressure localization;
a) ascends in white matter on dorsal (posterior) side of spinal cord 2) has 2 components running next to each other witin spinal cord: a) Gracile fascicle - carries sensory information derived from lower half of body b) Cuneate fascicle - sensory information from upper half of body (gracile = L, slender; cuneate ' L, wedge shaped) 3) System consists of a 3 neuron chain - primary, secondary, and tertiaty neurons a) begins with dorsal root ganglion neuron (primary neuron) - sensory neuron cell body located in dorsal root ganglion 1) peripheral process (axon) of dorsal root ganglion neuron responds to sensory input 2)central process (axon) enters dorsal horn of spinal cord and then ascends within gracilis fascicle or cuneatus fascile tract 3) axon of dorsal root ganglion neuron terminates in medulla oblongata of brainstem |
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Dorsal Column Pathway
2 of 2 |
b) in medulla, dorsal root ganglion neurons synapses onto secondary neuron of the chain
1) secondayr neuron located in either nucleus gracile or nucleus cuneate (depending on fascicle) 2) within medulla, axon of secondary gracile nucleus or cuneate nucleus neuron crosses over to opposite side of brain stem 3) axon then ascends through pons, midbrain, & cerebral peduncle to reach the thalmus d) in thalmus, axon of nucleus gracilis/cuneatus neuron synapse onto neuron of tertiary neuron 1) thalmus is sensory relay center for all types of sensory information e) axon of thalmic neuron ascends through white matter of cerebral hemisphere to synapse onto neuron in primary somatosensory cortex of parietal lobe (termination of pathway) |
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Primary somatosensory cortex
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processes general sensory information from body
a) located in postcentral gyrus of parietal lobe b) has distorted map of body surface (sensory homunculus) - areas with finest sense of touch (hands, face) have largest areas of brain devoted to processing that information c) sensory information arrives from the contralateral (opposite) side of the body) |
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Autonomic Nervous System
1 of 2 |
1) has two divisions - Sympathetic and Parasympathetic Nervous System
2) provides visceral efferent (motor) output to smooth muscle, cardiac muscle, & glands 3) consists of two neuron chain between central nervous system and target tissue a) first neuron (preganglionic neuron) - cell body located within CNS; sends axon out b) second neuron (postganglionic neuron) - cell body located in peripheral ganglion 1) pregagnglionic neuron synapses onto postganglionic neuron at ganglion 2) axon at postganglionic neuron extends to target tissue |
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Autonomic Nervous System
2 of 2 |
4) output to target tissue either excitatory or inhibitory
a) excitatory = organ or gland activated; smooth muscle contracts; heart rate increase b) inhibitory = organ or gland activity declines; smooth muscle relaxes; heart slows 5) most organs receive both sympathetic and parasympathetic inputs a) systems have both opposite actions (one excitatory, other inhibitory) b) effect determined by target tissue - one system not always excitatory or inhibitory (think of functional need of body to determine response by specific target tissue) |
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Parasympathetic Nervous System
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1) Parasympathetic system active when body is at rest, relaxed ("Rest and Digest")
2) craniosacral output - preganglionic parasympatheticneuron cell bodies located in: a) brainstem - axons exit with four cranial nerves - oculomotor III, fascial VII, glossopharyngeal IX, and vagus X 1) largest is vagus X nerve, supplies preganglionic parasympathetic innervation to all thoraicic and most abdominal organs 2) in abdomen, vagal fibers follow arteries (branches of abdominal aorta) to reach their target organ b) sacral S2 - S4 spinal cord - neuron cell body located in lateral horn of gray matter; axons exit spinal cord via ventral root and then run with sacral spinal nerves 3) postganglionic neuron cell body in terminal ganglion - located in or near target tissue a) in head, terminal ganglia from discrete (named) structures (ie. ciliary ganglion for eye) b) terminal ganglia for thoracic, abdominal, & pelvic organs are small and embedded within wall of organ - not grossly visible nor individually named |
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Sympathetic Nervous System
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1) sympathetic nervous system active with exercise or in emergency situations - "Fight or Flight"
2) thoracolumbar output - preganglionic sympathetic neuron cell bodies located only in thoracic and upper lumbar spinal cord T1 - T12; L1-L2 spinal nerves a) neuron cell bodies located in lateral horn of spinal cord gray matter - exit via ventral root 3) postganglionic sympathetic neurons - 2 locations a) chain ganglia of sympathetic trunk - provides sympathetic innervation to body wall (sweat glands, blood vessels), to heart and lungs, and to head (sweat & salivary glands; iris & ciliary muscles of eye) b) collateral ganglia of abdominal region - provide sympathetic innervation to abdominal organs |
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Sympatheitc trunk
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a) consists of a series of interconnected chain ganglia - trunk runs up/down along lateral sides of entire vertebral column (extends from base of skull to sacrum)
1) superior cervical ganglia - largest and most superior of chain ganglia b) receives preganglionic sympathetic inputs from T1-L2 spinal nerves only 1) White rami communicantes - connection from T1 - L2 spinal nerves to sympathetic trunk for passage of preganglionic sympathetic axons into sympathetic trunk 2) Preganglionic fibers may synapse onto postganglionic sympathetic neuron within chain ganglion near point of entry, or may travel to higher or lower level within sympathetic trunk before synapsing onto postganglionic neuron |
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Collateral Ganglion
1 of 2 |
a) postganglionic sympathetic ganglia located in abdominal cavity
b) provide sympathetic innervation to abdominal and pelvic organs: 1) axons of preganglionic sympathetic neurons enter sympathetic tunk via white rami communicantes from T1-L2 spinal nerves 2) these preganglionic sympathetic axons do not synapse in the chain ganglion a) instead, they exit sympathetic trunk and run as independent splanchnic nerves carrying only preganglionic sympathetic fibers) b) spanchnic nerves arise from thoracic region of sympathetic trunk, then run inferiorly, through th diaphragm, to enter abdominal cavity |
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Collateral Ganglion
2 of 2 |
3) In abdominal cavity, preganglionic axons synapse onto postganglonic sympathetic neurons located in a collateral ganglion
a) collateral ganglion located on abdominal aorta, at base of major arteries b) ganglia named for associated blood vessel 4) postganglionic sympathetic axons follow branches of associated artery - distribute to target tissue with arterial branches |
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Preganglionic parasympathetic axons to abdomin
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from CN X Vagus nerve also follow arterial branches from abdominal aorta to reach target tissues (terminal ganglia)
a) combination of preganglionic parasympathetic fibers & postganglionic sympathetic fibers form nerve plexus along blood vessels b) preganglionic parasympathetic fibers do not synapse until they reach the parasympathetic terminal ganglia located within the wall of abdominal organ |
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Adrenal Medulla
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receives splanchnic (preganglionic sympathetic) nerve innervation
a) release epinephrine (adrenaline) into the blood when sympathetic system is activated b) epinephrine reinforces sympathetic nervous system action on body |
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Visceral Afferent (Sensory) System
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1) visceral afferent information from viscera carried by afferent neurons - neuron cell bodies located in dorsal root ganglion
2) visceral afferent fibers enter spinal cord together with somatic afferent fibers (sensory from body surface, muscles, and joints) a) referred pain - visceral pain (when strong enough to reach conscious awareness) perceived as pain from that body surface region served by same spinal cord level 1) ex: pain of heart attack felt in lt shoulder and arm |
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Parasympathetic Nervous System
Functions |
"Rest & Digest"
Everyday homeostatic functions: - increase salivary gland secretions - decrease heart rate - increase gastric secretions - increase gastric motility - constrict pupils of eye - adjust lens of eye for near vision Generally organ specific function |
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Parasympathetic Nervous System
Anatomy: |
a) 2 neuron chain
1) Preganglionic neurons (craniosacral) Cranial nerves: CN III Oculomotor Nerve CN VII Facial Nerve CN IX Glossopharyngeal Nerve CN X Vagus Nerve S2,S3,S4 spinal cord levels 2) Postganglionic Neurons - terminal ganglia - in or near target tissue b) distribution - to eye, salivary glands, nasal cavity, and thoracic/abdominal viscera |
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Sympathetic Nervous System
Functions |
"Fight of Flight"
Emergency & Exercise response - increased blood pressure - increased heart rate - increased sweat production - decrease gastric secretions - decreased intestinal motility pupil dilation for distant viewing - release adrenaline/norepinephrine Generally wide spread body responses |
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Sympathetic Nervous System
Anatomy |
a) 2 neuron chain
1) Preganglionic neurons (thoracolumbar) - T1 - T12 & L1 - L2 spinal cord levels 2) Postganglionic Neurons x 2: a) Chain (paravertebral) ganglia of sympathetic trunk b) collateral (prevertebral) ganglia b) distribution - to all parts of body: blood vessels, sweat glands, errector pili muscle of skin, eye, heart, bronchial muscles, digestive organs, and salivary glands |
