The Central Nervous System

Components:

- Brain and spinal cord- Bone: skull/vertebral

column- Membranes and fluid

Meninges: membranes that surround the CNSThree Layers:1. Dura Mater: outer layer

next to bone and continues in vertebral column

2. Arachnoid mater: middle layer; covers brain/spinal cord

3. Pia mater: inner layer that covers nervous tissue. FX: nourishmenst of nerve

Meningitis: inflammation of meninges that is caused by bacteria/virus- Mainly infects children- May cause:

- Loss of vision/hearing- Paralysis- Mental Retardation

Cerebral Spinal Fluid (CSF): clear, watery substance that brings nutrients and protection to neurons

- Fills the subarachnoid space

- 500 ml secreted daily/absorbed by blood

- Absorbs forces which may damage brain

Spinal Cord:

- 31 segments (vertebrae)

- Each segment has a pair of spinal nerves

- Branch out into body (PNS)

- Central canal filled with CSF

White vs. Gray Matter

White Matter: neuron tissue with myelinated axons

Gray Matter: neuron tissue with unmyelinated axons

Spinal Cord Functions

1. Conduct nerve impulse along nerve tracts

Two Nerve Tracts:A. Ascending: sensory to

brainB. Descending: motor

impulse to organ/gland

2. Center for spinal reflexes

Reflexes: quick, involuntary, predictable reactions

- does not involve the brain

- Reflex arc: sensory neuron interneuron motor neuron

Ex. Knee-jerk reaction, pain reaction

The Brain

Primary Functions:1. Interprets sensory

information2. Issues motor commands to

skeletal muscles3. Carries higher mental

functions (memory/reasoning)

4. Coordinates muscle movements

5. Centers/pathways for regulatory visceral activities

Brain Organization:

1. Cerebrum (frontal, parietal, temporal, occipital lobes)

2. Cerebellum3. Brain Stem – connect

brain to spinal stem- Diencephalon- Midbrain- Pons- Medulla oblongata

Cerebrum:

- Largest part of the brain- Divided into two

primary lobes:-right and left cerebral hemispheres

Corpus Callosum: nerve fibers for connections and communications between hemispheres

Cerebrum

Surface Features:1. Sulcus: shallow

grooves2. Fissure: deep grooves3. Gyrus: elevated ridges

Cerebral Cortex: outside of the cerebrum

- Gray matter, 2-5mm, white matter beneath

FX:1. Motor areas

(voluntary):2. Sensory areas

(interpretation)3. Association areas

(conscious behavior)

1. Primary Motor Areas: in the frontal lobe- Located in the Post-

central and Pre-central gyrus

- Brocc’s: controls muscle action of mouth, tongue, larynx

- Pgs: 410-414

2. Association Areas: higher info processes

- Control memory, reasoning, verbalizing, judgment, emotion, concentration, planning, problem solving

Cerebral Lobes and Their FX:Sensory Function Motor Function Assoc. Function

Frontal:

Parietal:

Temporal:

Occipital:

Voluntary muscle Concentration, planning, judgment,

problem solving

Temp., touch, pressure, pain

Understand speech; words to express

thought

Remembering visuals; musichearing

visionCombining visual

images

Basal Ganglia

1. Serve as a relay station for motor impulses

2. Coordinates motor activities

3. Passes impulses from brain stem to spinal cord

4. Secretes dopamine- Gray matter deep in

cerebrum

Ventricles (409)

- Interconnecting cavities deep in cerebral hemispheres and brain stem

- Continuous with central canal of spinal cord

- Filled with CSF- Creates bouancy for the

brain

Brain Stem:

- Region of brain that connects the cerebrum to spinal cord

Four Parts:1. Pons2. Diencephalon3. Mid brain4. Medulla oblongata

Diencephalon: 3 parts

1. Thalamus – relay station for incoming sensory inputs

2. Hypothalamus – maintains homeostasis

3. Limbic System: produces emotions and modifies behavior; fear, anger, pleasure, sorrow

Pons: “bridge”

- Regulates breathing rhythm

- Relays impulses from cerebrum to spinal cord

- 3 cranial nerves from pons

Medulla Oblongata

FX:1. Control hear rate2. Vasometer center

(dilates/constricts blood vessels)

3. Regulates breathing with pons

Reticular Formation:

FX: consciousness by interconnecting several portions of the brain

Sleep: suspension of voluntary body functions and consciousness (partial)

Two Types: determined by electro encephalogram (EEG)

1. Non Rapid Eye Movement (NREM)

- Waves are slower; longer wavelength

- 4 stages (I – IV)- “light” sleep to “deep”

sleep

2. Rapid Eye Movement (REM)- “Paradoxical Sleep”- Most important type of sleep- Allows the portions of the

brain to rest- Higher oxygen consumption

in brain than when awake- Dreaming occurs- Increased body temp., heart

rate, respiratory and blood pressure

- Muscle inhibition- 90 minutes after sleep begins

Sleep Importance:- 1/3 of our lives is spent asleep- Lack of REM leads to depression

and other disorders- Brain works through days

events/emotions- Dream: “frustrated desires and

attempts to fulfill one’s wishes” – Freud

- Alcohol suppresses REM- Sleep requirements change as we

age (16 hrs to 7 hrs as adults)- Adults are light sleepers- Daily mediation/prayer increases

REM

The Peripheral Nervous System

Two Branches1. Somatic NS (voluntary

nerves)2. Autonomic NS

(involuntary )Two Nerve Types3. Cranial Nerves (brain)4. Spinal Nerves (spinal

cord)

Cranial Nerves:

- 12 pairs- All originate from brain

stem (except 1st pair)- Designated by number

and function (p. 469)

1. Olfactory Nerve (smell)

2. Optic Nerve (sight)

3. Oculomotor Nerve (eye muscle)

4. Trochlear Nerve (eye muscle)

5. Trigeminal Nerve (mouth)

6. Abducens Nerve (eye muscle)

7. Facial Nerve (facial muscle) – 5 branches (pg 471)

8. Vestibulocochlear Nerve (auditory)

9. Glossopharangeal Nerve (tongue/pharynx)

10. Vagus Nerve (neck and chest)

11. Accessory Nerve (soft palate, pharynx)

12. Hypoglossal Nerve (tongue, speaking, chewing/swallowing)

Spinal Nerves:

- 31 pairs from spinal cord- Each contains 1000s of

nerve fibers- Named after the

vertebral column

Spinal Nerves

- C: 8- T: 12- L: 5- S: 5- Co: 1- Total: 31

-Very short Nerves

- Divided into dorsal root, ventral root, dorsal ramus, and ventral ramus

Cauda Equina: “horse tail”

- the end of the spinal cord

- Between L1 and L2- Many nerve roots and

rootlets

Dermatomes

- Area of skin that has sensory nerve fibers from a particular nerve