Nervous System

Fundamental Purpose of the Nervous System

Receive, process information, issue commands to cells that carry out the response 

nerve cell

aka neuron

neurons have 3 fundamental properties

excitability or irritability, conductivity, secretion

examples of stimuli that excites nervous cells

sound, light, stretching, heat, touch, etc.

afferent cells

bring information INTO the CNS

efferent cells

Brings information OUT of the CNS

Role of CNS

information processing

Role of PNS

serves for input/output of CNS

Central nervous system (CNS)

brain and spinal cord

Peripheral Nervous System (PNS)

cranial nerves, spinal nerves, ganglia

sensory division includes

visceral sensory division and somatic sensory division

motor division includes

visceral motor division, and somatic motor division

visceral motor division includes

sympathetic division and parasympathetic

what does the somatic sensory division do

carries signals from receptors in the skin, muscles, bones, and joints.

what does the visceral sensory division do

carries signals mainly from the viscera of the thoracic and abdominal cavities.

Motor (efferent) division

carries motor signals by way of efferent nerve fibers from the CNS to effectors

Effectors

cells and organs that carry out the body’s responses; mainly gland and muscle cells

somatic motor division

carries signals to the skeletal muscles; involved in voluntarily control and involuntarily controlled muscles. contractions called the somatic reflexes.

visceral motor division

carries signals to glands/ cardiac muscle/ smooth muscle. 

autonomic nervous system controls the __ movements

involuntary

two divisions of the visceral motor divisions

sympathetic and parasympathetic divisions

sympathetic division of the visceral motor division

prepares the body for action

parasympathetic division of the nervous system

adapts the body to a state of rest.

a neuron consists of

soma

dendrites

axon

Soma

contains nucleus and protein-synthesizing organelles of cell

Dendrites

receive signals from other neurons

signals sent = graded potentials

Axon

generate/ conduct nerve impulse

axon hillock

terminal arborization

synaptic knob

trigger zone

axon hillock

axon terminal

CNS tracts

bundle of neuron fibers in the CNS

CNS nuclei

cluster of cell bodies of cell bodies in the CNS

PNS nerves

bundle of nerve fibers wrapped in connective tissue

PNS ganglia

a knot like swelling in a nerve where cell bodies of neurons are concentrated

neurons are outnumbered __:1 by supportive cells

50

supportive cells

neuroglia or glial cells

glial cells

protect neurons

aid neuron function

bind neurons together

Kinds of Neuroglia in the CNS

Oligodendrocytes

Astrocytes

Ependymal Cells

Microglia

Kinds of glial cells in the PNS

Schwann Cells

Satellite Cells

Oligodendrocytes function

produce myelin sheaths

oligodendrocytes have __ processes than astrocytes

fewer

oligodendrocytes wrap processes around __

neuron fibers

Myelin Sheaths are produces by

oligodendrocytes

myelin sheaths may coil around _ axons

60

Nodes of Ranvier (myelin sheath gaps)

points in the axon not covered by myelin sheath

white matter

has myelin

gray matter

no myelin

Astrocytes are the ___ abundant cells in the CNS

most

Astrocytes have radiating processes that cling to the

neurons

their synapses

capillaries

functions of astrocytes

form blood-brain barrier

regulate blood flow between neuron and its capillaries

recapture neurotransmitters

structural support

Tanycyte

Cuboidal epithelium

CSF production

Ependymal cells have 

microvilli and cilia

Ependymal cells line the central cavities of the

CNS

ependymal cells produce

cerebral spinal fluid (CSF)

what circulates CSF

beating of the cilia

microglia are ovoid and have

long thorny processes

microglia processes touch nearby

neurons

microglia play a ___ role

phagocytic

microglia increase in response to

infection or trauma to neurons

Satellite cells are found in the

PNS

satellite cells surround

neuron cell bodies

satellite cells provide

insulation around the soma

schwann cells surround ___ nerve fibers

larger

schwann cells form the

myelin sheaths

myelin is made from the 

plasma membrane of glial cells

schwann cells are found in the

PNS

schwann cell components

myelin sheath

neurilemma

nodes of ranvier

myelin sheaths protects and

electrically insulates

myelinated fibers conduct nerve impulses

rapidly

unmyelinated fibers conduct nerve impulses

slowly

dendrites are ___ insulated

always

myelin sheaths wrap around axons in a ___ fashion

paper towel roll

schwann cells external membrane makes up the

neurilemma

nodes of ranvier

points on axon where schwann cells do not touch

nodes of ranvier allows for

axon collaterals

classifications of neurons

structural and functional

structural neurons classifications

multipolar

bipolar

unipolar

multipolar

an axon and two or more dendrites

most common in body

bipolar neurons

an axon and one dendrites

bipolar neurons are rare and only found in

retina of eye

olfactory mucosa

unipolar neurons

only a single process arising from soma

most sensory neurons

unipolar neurons are chiefly in the

ganglia of PNS

functional classes of neurons

sensory neurons

interneurons 

motor neurons

sensory neurons

transmit information TO the CNS

interneurons lie between

motor and sensory nerves

Sensory neurons have cell bodies that are located in

sensory ganglia outside CNS

sensory nerves are mostly __polar

uni

interneurons are mostly within the

CNS

about 90% of human nerves are

interneurons

interneurons are mostly __polar

multi

motor neurons signal conduction ___ from CNS

away

Cell bodies of motor neurons are ___ CNS

inside

motor neurons are mostly __polar except for autonomic nerves

multi

cells produce signals called

graded (local) potentials and action potentials

electrical signals

transfer information from one part of the body to another

electrical properties result from

ionic concentration differences across plasma membrane

permeability of membrane