NERVOUS SYSTEM

Nervous System

• composes 3% of total body weight (2 kg)

  intricate network of neurons and neuroglia - accessory cells, help in processing the nervous system

neurology

deals with normal functioning and disorders

Nerve

basic unit of the nervous system

Central Nervous System

brain and spinal cord (encased in bone - surrounded by bone)

Peripheral Nervous System

everything beyond the nervous system

2 divisions of PNS

Motor Division, Sensory Division

under CNS

brain and spinal cord

foramen magnum

spinal cord connects to brain (opening)

CNS

encased by the skull and spinal column

spinal cord connects to brain via foramen magnum

contains thoughts, emotions, memory, controls movement, and many other functions

spinal cord: cervical, thoracic, lumbar, sacral, coccygeal

PNS

all nervous tissue everything beyond the CNS

pairs of cranial nerves

12 pairs

pairs of spinal nerves

31 pairs

cutaneous

sensory nerve (fat wallet syndrome)

Sensory

afferent receptors: what you feel; affective sensation

input

sensation

external stimulus

Motor

Efferent: did something visible; effective

output

reaction

movement

Motor Divisions

Somatic Nervous System (body)

Autonomic nervous System

Somatic Nervous System (body)

CNS to skeletal muscles

voluntary

Autonomic nervous System

CNS to smooth, cardiac muscles, and glands

involuntary

sympathetic nervous system

parasympathetic nervous system

enteric nervous system

sympathetic nervous system

fight or flight (sweating a lot, adrenaline - too much work done)

parasympathetic nervous system

eat and sleep; opposite of sympathetic

enteric nervous system

stomach, intestines, GI system: intestinal movement, sumpay ni sympa and para

sensation

detect internal and external stimuli (you notice; no adjectives added); balance, hear, sight, smell, taste

sensations: olfaction - smell, ocular - eyes, gustatory - taste, vestibular - balance, auditory - hear

integrative fucntion

processing the information you get; and making decisions (integration)

motor function

after integration, appropriate motor response

Neuron

respond to stimulus, like muscles

stimulus - change in the environment, produces an action potential (causes an action)

action potential - electrical signal that travels the nerve membrane; energy for change

three primary parts of neuron

cell body/one soma

two nerve fibers:

axon - long projection from the cell body; trunk

dendrites - branch

cell body

also known as perikaryon/soma

group of cell bodies is called a GANGLION

contains the nucleus, cytoplasm, and organelles

Special parts of neuron

nissl bodies, lipofuscin

Nissl bodies

rough ER of the neuron; responsible for the proteins- ribosomes

Lipofuscin

the yellow pigment in aging neurons; the older you get the more lipofuscin you get in your skin (aging process)

Nerve fiber

general term for extensions from soma

axon

output

long, thin, cylindrical

trunk

dendrite

input

short, multiple, tapering

branches

axon hillock

connection between soma and axon

initial segment

area immediately after hillock

axoplasm and axolemma

cytoplasm and membrane of axon

trigger zone

where nerve impulses arise, covered by the myelin sheath

axon terminals

axonal endings

myelin sheath

covers the axons (?) more insulation = faster the impulse

synapse

site of communication between neurons/effector cell

synaptic end bulbs

bulb-shaped structures at axon terminals

varicosities

swollen bumps at axon terminals

synaptic vesicles

membrane sacs containing neurotransmitters (ACH)

structural classification

according to number of processes/fibers

multipolar neurons

several dendrites, 1 axon

most CNS and motor neurons are this type

bipolar neurons

1 axon, 1 dendrite

eye, inner ear, olfactory areas (smell)

unipolar neurons

fused dendrite and axon

sensory receptors

functional classification

direction of nerve impulse, away or towards CNS

sensory neurons

afferent neurons; unipolar

contain or located after sensory receptors

sends impulses towards CNS

motor neurons

efferent neurons; multipolar

away from CNS

interneurons

association neurons; multipolar

between sensory and motor neurons

receive impulse and elicits response

Neuroglia

make up half of total volume of CNS

smaller than neurons, but more numerous

DO NOT PRODUCE

supports neural activities

Neuroglial Cells in CNS

astrocyte, oligiodendrocytes, microglia, ependymal cells

Neuroglial Cells in PNS

shwann Cells, satellite cells

Astrocyte

star-shaped cells; maintains blood barrier

Oligodendrocytes

produces myelin sheath; insulination (black covering)

Microglia

phagocytes; removes cellular debris and damaged tissue

Ependymal cells

assists in CSF circulation - floats in the water

Shwann cells

produces myelin sheath

satellite cells

structural support and material exchange; going in and out of waste products; responsible for cleaning out the neurons

myelination

nerve cells are myelinated

nodes of ranvier

gaps between myelin sheath; saltatory (?) induction

destruction of myelin sheath

spasticity

muscles always contracted; happens on people with stroke in the brain (brain can’t tell the muscles to relax)

bundle of soma in CNS

nucleus

bundle of soma in PNS

ganglion

bundle of axons CNS

tract

bundle of axons PNS

nerve

white matter

myelinated axons (myelin sheath caused the white coloration of the brain)

gray matter

neurons and neuroglia (no myelination)

graded potential

short distance communication (if duol lang)

action potential

long distance communication (further away); body constantly produces action potential except sleeping

muscle action potential

nerve action potential

when sleeping, brain loses connection with the body

resting membrane potential

normal charge of a cell membrane

to produce an impulse, it must be positively charge

normal microvoltage charge

typically, -40 to -90 mV, average of -70mV (microvoltage)

graded potentials (negative to positive)

any change from resting membrane potential

action potentials

rapidly occurring event that reverse polarization

continuous conduction

occurs in unmyelinated cells

conduction of impulse through the whole axon

slow conduction

saltatory conduction

due to myelination

impulse jumps between nodes of ranvier

speeds up travel of impulse

spinal nerves

31

vertebrae

26

vertebral discs

23

vertebral column

composed of vertebral vertebrae

vertebral foramen - encases spinal cord (foramen - opening)

contains ligaments to maintain integrity

anterior ligament (1)

ALL - anterior longitudinal ligament

posterior ligaments (4)

posterior longitudinal ligament

supraspinous ligament

interspinous ligament

ligamentum flavum

vertebrae parts

cervical vertebrae (7 cervical)

thoracic vertebrae (12)

lumbar vertebrae (5)

sacrum

coccyx

meninges

three protective layers that encircle the spinal cord and brain

made up of connective tissue

epidural space

space between vertebral canal and dura mater

dura mater

most superficial

thickest and strongest layer

dense irregular tissue

arachnoid mater

thin and avascular

spider web like arrange of collagen and elastic fibers

contains the CSF; fed by the CSF

flexible elastic layer

pia mater

adheres to the surface of SC (spinal cord) or brain

squamous to cuboidal cells with collagen and elastic fibers

denticulate ligaments - suspend the spinal cord in its dural sheath; act like anchors; keeping the brain and spinal cord into place

filum terminale

anchors spinal cord to arachnoid mater

ascending tracts

sensory tracts

descending tracts

motor tracts

posterior gray horns

sensory neurons and interneurons; posterior - sensory (refers spinal cord)

anterior gray horns

somatic motor nuclei, skeletal muscle control (motor)

lateral gray horns

autonomic nuclei (smooth, cardiac)

blood supply

contains 3 arteries:

1 anterior spinal artery

2 posterior spinal arteries

posterior (Dorsal) root

sensory neurons, contains dorsal root ganglions

anterior (ventral) root

motor neurons

cauda equina

horse-tail, extensions of spinal nerves from filum terminale (cauda equina injury - loose sensation of legs, hard time coordinating)

endoneurium

innermost layer, collagen fibers, fibroblasts, and macrophages