Nervous System:

An Introduction

HAP

Susan Chabot

Lemon Bay High School

Function of the Nervous System

3 overlapping functions

• SENSORY INPUT - Monitor changes

inside and outside of the body; these

changes are called STIMULI.

• INTEGRATION - Processes and

interprets changing stimuli to decide.

• MOTOR OUTPUT - Effects a response

via activating effectors (muscles or

glands).

Working Together

The Nervous System works with the

Endocrine System to provide

ELECTRICAL and CHEMICAL

control of ALL body processes.

Structural Organization

Nervous System

Central Nervous System

Brain and Spinal Cord

Responsible for Integration

Peripheral Nervous System

All neurons not in brain or spinal

cord

Responsible for sensory input

and motor output

Functional Organization

Peripheral Nervous System

Sensory/Afferent

Moves information TOWARD the CNS

Motor/Efferent

Moves information AWAY FROM the CNS

Somatic/Motor

Voluntary control of skeletal muscles

Autonomic

Involuntary control of smooth and cardiac

muscles and all glands

Sympathetic

Fight-or-Flight

Parasympathetic

Resting-or-Digesting

Autonomic Continuum

Rest

or

Digest

Fight

or

Flight

Cells of the Nervous System

• 2 categories

– Neurons transmit electrical impulses

• Sensory neurons = receptors

• Integration neurons = integrate/think

• Motor neurons = effect a change through

muscles and/or glands

– Neuroglia = Nerve glue

• Protect, insulate, and support delicate neurons

Cells of the Nervous System

• Neuroglia = Nerve Glue

– Astrocytes

• Star-shaped cell that provides a scaffold to

hold neurons in specific locations.

– Oligodendrocytes

• Insulates neurons for speedy transmission of

electrical impulses; similar to insulation for

electrical wires.

– Ependymal Cells

• Produces cerebrospinal fluid (CSF)

– Microglial cells

• Small white blood cells that destroy pathogens

and cell debris.

Cells of the Nervous System

Neurons/Nerves

3 main parts

• Dendrite: receives

info from

neighboring neurons.

• Cell body: living

portion of the neuron;

contains the nucleus

and organelles.

• Axon: sends info to

neighboring neurons.

Appearance Location Function

BiPolar

2 extensions on opposite

ends of cell body

Special senses in

skull

Collect sensory

info for sight,

hearing, smell,

taste

UniPolar

1 continuous extension,

cell body pushed to side

Special senses far

from brain

Collect sensory

info for pain,

pressure, touch

MultiPolar

Many dendrites, single

long axon

Brain Form networks

that span distance

Anaxonic

Cannot tell dendrites from

axon

Brain Form close-knit

networks

Bipolar Unipolar Multipolar Anaxonic

Neuronal Networks

• Connection of individual neurons

• Forms synapses Axon and

dendrite(s)

• The more dendrites

communicating with a single

neuron, the wider the network

Synapses

• Connection between 2

neurons

• Axon (neuron #1) and

Dendrite (neuron #2)

• Stimulation of neuron

causes release of

neurotransmitter into

the synapse

• Neurotransmitter must

“dock” onto membrane

of next neuron for

simulation to continue

Cells of the Nervous System

Synapse

– Space in between neighboring neurons.

– Contains neurotransmitters; chemicals

that are released to control info/activity

in brain. Types of Synapses

• Neuron-to-NeuronFound throughout Nervous

System

• Neuron-to-MuscleNeuromuscular

• Neuron-to-GlandNeuroglandular

Protection of the CNS

• Meninges

– What Are They? Connective tissue outer

protection covering of the brain.

– Layers

• Dura mater

• Arachnoid mater – Circulates CSF

• Pia mater

• CSF: Cerebrospinal fluid

– What is It? A watery substance

– How Does it Offer Protection? It bathes the

brain and cushions from trauma.

– How is it Formed? In a Dense capillary bed

by called the CHOROID PLEXUS

Meninges

Protection of the CNS

• Blood-brain barrier

– What is It? A tight network of capillary beds

that are both

SELECTIVE - Keeps some things out and

other allows other things in.

DIRECTIONAL - Moves INTO the brain not

OUT OF the brain

– How Does it Work? Acts as a successively

smaller filters to keep substances from

entering the circulation of the brain and

spinal cord.

Lobular Organization

Divisions of the Brain

• Cerebral Cortex: high order processes; speech, language, cognition.

• Cerebellum: responsible for the coordination of muscle activity.

• Pons: relays sensory info from the cerebellum to the cerebral cortex.

• Medulla oblongata: the “primitive” brain; controls heart rate, respirations, hunger, thirst.

• Diencephalon: important in the integration of the nervous and endocrine system/temperature control

The Brain

Structural Organization

Cerebrum• Processing

• Integration

• Memory storage

Structural Organization

Cerebellum• Adjusts

ongoing

movement

• Muscle

memory

Structural Organization

Thalamus• Relay center

Diencephalon

HypothalamusEmotions

Autonomic functions

Hormone production

Structural Organization

MesencephalonVisual and auditory

processing

Reflex control

Maintains

consciousness

Structural Organization

PonsConnects brainstem

to cerebellum

Somatic and

visceral motor

control.

Structural Organization

Medulla OblongataRegulates heart rate, blood

pressure, and digestion