The Spinal CordChapter 13

I. Gross Anatomy of the Spinal Cord

A. ~18 inches long by ~1/2 inches wide

B. See handout for diagram of anatomyFind and know these terms:

Posterior medial sulcus Anterior median fissure Cervical & lumbar enlargements Conus medullaris Filum terminale (“terminal thread”) Dorsal root ganglion Dorsal & ventral roots Spinal nerves Cauda equina (“horse tail”)

C. Spinal Meninges

1. a series of specialized membranes that provide physical stability and shock absorption

2. Blood vessels lie within the layers to deliver oxygen and nutrients.

3. are continuous with the cranial meninges surrounding the brain

4. Bacterial/viral infection can cause meningitis

a) inflammation of the meninges

b) can disrupt circulation of cerebrospinal fluid (CSF)

c) can be deadly

d) Meningitis & college… should you get vaccinated?

5. Three meningeal layers

a) Dura Mater (“hard mother”)

i. tough, fibrous, outermost covering

ii. padded from vertebrae by adipose tissue in the epidural space

► Injecting an anesthetic into this space will affect spinal nerves near the injection site.

► May be used in the lower lumbar or sacral region during childbirth.

b) Arachnoid (“spider”)

i. middle layer

ii. encloses the subarachnoid space

► contains a network of collagen and elastic fibers (arachnoid trabeculae)

► filled with CSF- shock absorption- diffusion of nutrients and wastes

► Spinal taps occur here- withdrawal of CSF with a hollow needle

in the lower lumbar region- used to diagnose problems like

meningitis

c) Pia Mater (“delicate mother”)

i. innermost layer

ii. contain blood vessels that service the spinal cord

iii. bound firmly to the underlying neural tissue

II. Sectional Anatomy of the Spinal Cord

A. See handout for diagram of anatomy

B. Organization of Gray Matter

1. Reminder: gray matter= unmyelinated neuron cell bodies

2. Functional groups:a) Sensory nucleib) Motor nuclei

C. Organization of White Matter

1. Reminder: white matter = myelinated axons

2. Each side is divided into three regions called columns or funiculi:

a) Posterior white columnsb) Anterior white columnsc) Lateral white columns

3. Each column contains tracts (bundles of axons):

a) Ascending tracts – sensory infob) Descending tracts – motor info

III. Spinal NervesA. Each spinal nerve is covered by a

series of connective tissue layers1. Epineurium- outermost layer

2. Perineurium a) middle layerb) surrounds bundles of axons (fascicles)c) contains blood vessels

3. Endoneurium a) innermost layerb) surrounds individual axons

B. See handout for diagram of anatomy

C. Dermatomes:

1. a specific region of the body surface that is monitored by a pair of spinal nerves

2. Damage or infection of a spinal nerve will produce a loss of sensation in the specific skin region

► example: Shingles (ask Ms. Schroeder!)

D. Nerve Plexuses (“nerve braid”)

1. complex, interwoven network of nerves

2. Three major plexuses:

a) Cervical plexus- spinal nerves C1-C5

b) Brachial plexus- spinal nerves C5-T1

c) Lumbosacral plexus- T12-S4

The BrainChapter 14

I. Introduction to the Organization of the Brain

A. Contains ~98% of body’s neural tissue

B. Weighs ~3lbs & has a volume ~1200 cm3

1. Can vary from 750 cm3 – 2100 cm3

2. Men’s brains are ~10% larger than females

3. No correlation exists between size & intelligence

C. Preview of Major Regions & Landmarks

1. Cerebrum

a) Largest in size of all the regions

b) Consists of paired cerebral hemispheres

c) Conscious thoughts, sensations, intellect, memory & complex movements originate here

d) Surfaces are highly folded and covered by neural cortex, a superficial layer of gray matter (cerebral cortex)

2. Cerebellum

a) Second largest in size

b) Also divided into hemispheres, partially hidden by the cerebral hemispheres

c) Adjusts ongoing movements on the basis of comparisons between new and old sensations

3. Diencephalon

a) Links the cerebral hemispheres and the brain stem

b) Left & right thalamus

► Contain relay and processing centers for sensory information

c) Hypothalamus

i. Floor of diencephalon

ii. Connected to the pituitary gland

iii. Involved with emotions, autonomic function & hormone production

4. Brain stem

a) Contains a variety of important processing centers that relay information headed to or from the cerebrum or cerebellum

b) Includes:

i. Mesencephalon

► Contain sensory nuclei that process visual & auditory information & control reflexes for these stimuli

ii. Pons (“bridge”)

► Connects cerebellum to brain stem

► Contains tracts, relay centers & nuclei involved with somatic & visceral motor control

iii. Medulla Oblongata

► Connects brain to spinal cord

► Relays sensory information to the thalamus and the brain stem

► Contains major centers concerned with regulation of autonomic function (heart rate, blood pressure, digestion)

D. Ventricles of the Brain

1. Chambers filled with CSF and lined by ependymal cells

2. CSF continually circulates between the ventricles, central canal & subarachnoid space

3. 4 chambers:a) 1st Lateral Ventricleb) 2nd Lateral Ventriclec) 3rd Ventricle - in the diencephalond) 4th Ventricle

II. Protection & Support of Brain

A. Brain is protected by:1. Cranial bones2. Cranial meninges

a) same 3 from spinal cord are continuous in the brain w/ some differencesi. Dura mater has 2 layers w/ the superficial layer

fused w/ the periosteum of the cranial bones

ii. No epidural space

iii. Dural layers are separated by a small gap & in some places large channels called dural sinuses

b) Functions of the Cranial Meninges

i. Tough, fibrous dural folds hold brain in position

ii. CSF acts as a shock absorber

3. Cerebrospinal fluid

a) Produced by ependymal cells in the choroid plexus

b) ~150 ml of CSF in the nervous system

c) Entire volume of CSF is replaced every 8 hrs

4. Blood-brain-barrier