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Chapter 13
Spinal Cord and Spinal Nerves
44
Anatomy
Undergraduate 2
12/04/2010

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Cards

Term
Spinal Cord Functions
Definition

1. Processes reflexes

2. Site for integration of APs that aries locally (or triggered by impulses from PNS and brain)

3. Conduction pathway for sensory & motor nerve impulses

Term
Protective Structures
Definition

1. Vertebral Column

2. Meninges

3. Cerebrospinal Fluid

Term
Vertebral Column
Definition
bony covering of spinal cord
Term
Meninges
Definition

-tough CT

-spinal- surround spinal cord

-cranial- surround brain

 

Term

Meninges Layers:

Dura Mater

Definition

outermost layer "leather jacket"

 

Term
Subdural Space
Definition

between Dura and arachnoid mater

-contains interstitial fluid

Term

Meninges Layers:

Arachnoid mater

Definition
middle layer
Term
subarachnoid space
Definition

between arachnoid and pia mater

-contains cerebrospinal fluid (CSF)

Term

Meninges Layers:

Pia Mater

Definition

innermost layer "t-shirt"

-thin, transparent CT layer

-adheres to surface of spinal cord and brain

 

Term

Meninges Layers:

CSF

Definition

helps with protection

-shock absorber; supplies nutrients

Term
External Anatomy of Spinal Cord
Definition

-begins as continuation of medulla oblongata

-terminates at coneus medullary

-roughly cylindrical with slightly flattened regions

-16-18 inches long

-3/4 inch diameter

-contains cervical and lumbar enlargements (point of origin for nerves to extremities)

Term
Spinal Nerves
Definition

-31 pairs

-paths of communication between SC & most of body

-Named & numbered according to region & level of SC they emerge

-part of PNS

-connect CNS to sensory receptors, muscles, & glands


Term
Spinal Nerves
Definition

Cervical: 8

Thoracic: 12

Lumbar: 5

Sacral: 5

Coccygeal: 1

Term
Roots of SC
Definition

-connect each spinal nerve to a segment of SC

-2 points of attachment: posterior root and anterior root

Term
Posterior (dorsal or sensory) root
Definition

-contains sensory fibers

-conducts impulses from PNS->CNS

-has swelling = posterior root ganglion: mass of cell bodies of sensory neurons

Term
Anterior (ventral or motor) root
Definition

-contains motor neuron axons

-conducts impulses from CNS->PNS & effector cells

-cell bodies of motor neurons in gray matter of SC

Term
Internal anatomy of SC
Definition

1. Gray Matter

2. White matter

3. Central Canal

Term
Gray Matter
Definition

-shaped like H

-Consists of: cell bodies of neurons, neuroglia, unmyelinated axons, dendrites of interneurons, motor neurons

-receives & integrates incoming & outgoing information

Term
White Matter
Definition

-outside-surrounds gray matter

-consists of: bundles of myelinated & unmyelinated sensory axons, interneurons, motor neurons

-highways of impulse propagation to and from brain

Term
Central Canal
Definition
contains CSF
Term

CT covering of spinal nerves

 

Definition

-axons grouped within CT sheathes

-3 layers: epineurium, perineurium, and endoneurium 

Term
Epineurium
Definition

-surrounds entire nerve

 

Term
nerve
Definition
bundle of fascicles
Term
Perineurium
Definition
-surrounds individual fascicle
Term
fascicle
Definition
bundle of axons
Term
Endoneurium
Definition

-surrounds individual axon

 

Term

Distribution of Spinal Nerves:

Branches

Definition

a. posterior ramus: serves deep dorsal trunk muscles and skin

b. anterior ramus: serves muscles of upper and lower limbs; serves skin of lateral and ventral trunk

Term

Distribution of Spinal Nerves:

Plexuses

Definition

-network of axons from many anterior rami

-cervical, brachial, lumbar, sacral, coccygeal

Term

Distribution of Spinal Nerves:

Intercostal nerves

 

Definition

-thoracic nerves

-T2-T12 directly innervate structures they support

Term
Dermatomes
Definition

-skin is supplied by spinal nerves (carry somatic sensory nerve impulses to SC)

-spinal nerves innervate specific, constant skin segments (except C1, skin segments = DERMATOMES)

-helps physicians to determine segment of SC or which spinal nerve is malfunctioning

Term

Spinal Cord Physiology:

2 Functions

Definition

1. White matter are highways for impulse conduction to and from brain

2. Gray matter receives and integrates incoming and outgoing information

Term
Tract
Definition

-distinct bundles of axons

-have common origin or destination

-carry similar information

-may extend long distance up or down SC

Term

Sensory Tract

 

Definition

-ascending

-axons conduct impulse towards brain

Term
 Motor Tract
Definition

-descending

-axons conduct impulses down SC

Term
Reflexes
Definition

-fast, predictable, automatic response to changes in environment

-helps to maintain homeostasis (permitting body to make exceedingly rapid adjustments)


Term

Reflexes:

4 types

Definition

1. Spinal reflex: integration in SC gray matter

2. Cranial reflex: integration in Brain

3. Somatic reflex: skeletal muscle contracts

4. Autonomic (visceral) reflex: smooth and cardiac muscle, glands

Term
Reflex Arc
Definition

-simplest type of pathway

-pathways = specific neuronal circuits

-include at least one synapse


Term

Reflex Arc:

5 functional components

Definition

1. sensory receptor: responds to stimulus

2. sensory neuron: moves signal to CNS

3. Integrating center: processes input and starts response

4. motor neuron: carries response signal

5. effector: part that responds

Term

Stretch Reflex:

monosynaptic

Definition

1 sensory neuron and 1 motor neuron

 

Term

Stretch Reflex:

Ipsilateral reflex

Definition
-sensory and motor impulse same side of SC
Term
Stretch Reflex
Definition

-maintains muscle tone

-muscle coordination during exercise

-ex: patellar reflex

Term
Tendon Reflex
Definition

-polysynaptic: 2 nuerons

-ipsilateral

-prevents damage to muscles & tendons from stretching

-operates as a feedback mechanism

-controls muscle tension by causing relaxation when force too extreme

Term
Flexor (withdrawal) reflex
Definition

-polysynaptic

-ipsilateral

-intersegmental: several SC segments involved

-protective withdrawal reflex

-moves a limb to avoid pain

-contraction of flexor muscles to move a limb

-works with crossed extensor reflex to maintain balance

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