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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
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