central nervous system: exam 2 review (spinal cord)

spinal cord

- inferior to brain

- exits cranium via foramen magnum

- descends vertebral canal

spinal cord segments

- 31 total

- 8 cervical

- 12 thoracic

- 5 lumbar

- 5 sacral

- 1 coccygeal

- 1 pair of spinal nerves per segment

- C1- C7 above

- C8- Co1 below

- nerves exit via intervertebral foramina

spinal cord enlargements

- swellings in the spinal cord

- nerves to limbs

- cervical enlargement

- lumbar enlargement

distal end of spinal cord

- known as CONUS MEDULARIS

- between L1 and L2 in adults

- FILIUM TERMINALE anchors end to sacrum

- CAUDA EQUINA is nerves to hip and legs

cross section of spinal cord

- central canal in center

- gray matter( H shaped, cell bodies of motor nerves)

- intermediate horns lateral

- distal horns are posterior (sensory nerves)

- white matter (myelinated axons, tracts are bundles of axons)

- ascending tracts move up the cord

- descending tracts move down the cord

spinal nerve anatomy

- spinal nerves connected to cord via 2 nerve roots

- DORSAL NERVE ROOTS are posterior (sensory nerves)

- DORSAL ROOT GANGLION (bundle of sensory nerve cell bodies in the dorsal root)

- VENTRAL NERVE ROOTS are anterior (motor nerves)

spinal nerve and axons

- SPINAL NERVES = contain sensory and motor nerve fibers)

- INDIVIDUAL AXONS =nerve fibers)

Neuriums

- ENDONEURIUM ( connective tissue covering of axon)

- FASCICLES (inside, bundles of axons)

- PERINEURIUM (connective tissue covering of fascicle) - EPINEURIUM- TOP CONNECTIVE TISSUE LAYER

spinal nerve anatomy

- entire spinal nerve composed of fascicles

- epineurium= (top, connective tissue covering of spinal nerve)

- perinerium = around nerve- -endoneriuem = around axon. dorsal ramus ( posterior branch of spinal cord)

- ventral ramus ( anterior branch of spinal nerve, larger than dorsal)

nerve plexuses

- network of nerves (4 main)

- 1. cervical plexus ( to neck and chest)

- 2. brachial plexus (to arms)

- 3. lumbar plexus (to anterior legs)

- 4. sacral plexus ( to posterior legs and buttocks)

spinal nerve reflex

- quick response to stimuli

- does not involve brain

- 4 or 5 steps

1. sensory receptor- detects environmental change

2. sensory nerve- carries impulse to cns

3. intermediate nerve- within cord and some reflexes do not involve this step

4. motor nerve- cns to periphery

5. effector organ- responds to stimulus (ex: patellar tendon reflex)

types of reflexes

- stretch

- golgi tendon reflex

- withdrawl reflex

- crossed extensor reflex

Stretch reflex

- prevents muscle from stretching too much

- receptors ( intrafusal + extrafusal muscle fibers)

- reciprocal inhibition of antagonist

golgi tendon reflex

- prevents muscle from contracting too much

- protects tendons

- receptor (golgi tendon organ)

- reciprocal excitation of antagonist

crossed extensor reflex

- one leg withdrawn

- one leg extended

meninges

- coverings of the central nervous system

- 3 layers

1. Dura mater- outer layer, dense irregular connective tissue, epidural space above dura mater

2. Arachnoid mater- middle layer, thinner than dura

- subarachnoid space- below arachnoid space, contains CSF

3. pia mater- inner layer, denticulate ligaments connect pia mater to spinal nerves

cerebral spinal fluid

- produced in brain

- covers cns

- protection, nutrition

menigitis

- inflammation / infection of spinal cord

- Streptococcus pneumoniae

- Neisseria meningitidus

- symptoms are headache, stiff neck, seizures

- diagnosis is blood culture and lumbar puncture

- treatment is antibiotics for bacterial infection, rest, fluid, pain medication, and supportive care

lumbar puncture

- also known as spinal tap

- samples cerbral spinal fluid

- needle inserted between L3 and L4 vertebrae

- avoids cord

vaccines for meningitis

- Pneumococcal polysaccharide vaccine

- Adults over 65

- Children over 2 with depressed immune system

Shingles

- Herpes zoster infection

- Chicken pox virus

- Retreats to dorsal root ganglion

- Reactivates in response to illness, stress

- symptoms are pain, redness, blisters; along distribution of sensory nerve (dermatome)

- treatment is shingles vaccine, and antiviral medication

distal end of the spinal cord and structures below

- ends at L1, L2

- called conus medularis

- filium terminale anchors end to sacrum

- cauda equina hangs below conus medularis