Download The Nervous System

The Nervous System
May 2015
Biology X
Neurons
•  Neurons are nerve cells & are the basic unit
of the nervous system
•  Divided into 3 regions
–  Cell body
–  Dendrites
***No centrioles
•  Receive impulses & carry them toward the cell body
–  Axon
•  Carries impulses away from the cell body & toward
other neurons
Types of Neurons
•  Three categories
–  Sensory neurons
•  Carry impulses from body to spinal cord & brain
–  Motor neurons
•  Carry response impulses away from the brain & spinal
cord
–  Interneurons
•  Found in brain & spinal cord
•  Process incoming impulses & pass response on to motor
neurons
Communication Between
Neurons
•  Neurons communicate with other neurons
and other cells at special junctions called
synapses.
•  Neurons don t actually touch other cells
•  Impulses are transmitted from cell to cell by
the release of chemicals called
neurotransmitters.
Nerve Impulses
•  Electrical impulses are
generated by changes in
sodium and potassium
concentrations in the
neuron
•  As the impulse travels
along the neuron, they
eventually cause the
release of
neurotransmitters, which
transmits the impulse to
the next cell.
Effects of Drugs on Neurotransmitters
•  Alcohol
–  Acts as a depressant; decreases activity of central nervous
system, impairs judgment, speech & coordination
•  Cocaine
–  Blocks normal removal of pleasure-inducing
neurotransmitters
–  Addiction may cause permanent chemical changes in the
brain
•  Methamphetamine ( Meth )
–  Causes brain to release large amounts of neurotransmitters
–  May cause permanent brain damage
Nervous System Organization
•  Central Nervous System
•  Peripheral Nervous System
–  Somatic (Voluntary)
•  Reflexes (Automatic response to a stimulus) can occur in
somatic nervous system
–  Autonomic (Involuntary)
•  Sympathetic NS (“Fight of Flight”)
•  Parasympathetic NS (resting)
Central Nervous System
•  Brain & spinal cord
make up the central
nervous system
•  Coordinates all of the
body s activities
Central Nervous System
•  Brain
•  Three main sections
–  Cerebrum
•  Intelligence, memory,
language, skeletal muscle
movements, senses
–  Cerebellum
•  Balance, posture, coordination
–  Brain Stem (Medulla
Oblongata, Pons, Midbrain)
•  Involuntary actions (breathing,
heart rate)
Four Lobes of Cerebral Cortex
•  Frontal Lobe
–  Speech, Smell,
Intellectual & motor
function
•  Occipital Lobe
–  Vision
•  Parietal Lobe
–  Sensory function
•  Temporal Lobe
–  Hearing
Central Nervous System
•  Spinal cord
•  Nerve that extends
from the base of the
brain to the lower back
•  Runs through the
spinal canal and is
protected by the bones
of the spine (vertebrae)
Peripheral Nervous System
•  Composed of sensory
& motor neurons
•  Carries nerve impulses
sent between the
central nervous system
and the rest of the
body
Peripheral Nervous System
•  Sensory Neurons
–  Carry nerve impulses from sense organs to
CNS
•  Motor Neurons
–  Carry nerve impulses from CNS to muscles and
glands
Divisions of Peripheral
Nervous System
•  Somatic (Voluntary)
–  Examples: running, walking, lifting
•  Autonomic (Involuntary)
–  Examples: heart beating, digestion
•  What about breathing?
•  It s part of both the somatic and autonomic
nervous systems
Somatic Nervous System
(Voluntary)
•  Although it s voluntary,
a stimulus can
sometimes result in an
involuntary response
•  Reflex: an automatic
response to a stimulus
–  Response travels to spinal
column instead of all the
way to the brain
Autonomic Nervous System
(Involuntary)
•  Sympathetic ( Fight or Flight )
–  Shocking or frightening stimulus causes the
release of epinephrine or norepinephrine
(hormones)
–  Increase in heart & breathing rates
•  Parasympathetic (At Rest)
–  Controls organs when the body is at rest
Organization of the Nervous System