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NERVOUS
SYSTEM
Science, Technology, & Society
MR. CANOVA
Period 11
Neurons and Nerve Impulses
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Neuron-Nerve cells that
transmit information
throughout the body
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Dendrites-”Antennae”
that receive information from
other cells
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Axon-Extension of cytoplasm
that conducts nerve impulses
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Myelin sheath-Layer of
insulation
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Nodes of RanvierGaps between myelin sheath
Neuron Function
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Membrane potential- The difference in electrical charge
across the cell membrane. Expressed in voltage.
Resting potential- The membrane potential of a neuron at
rest
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-70 millivolts (mV)
Inside of cell is negatively charged, outside of cell is
positively charged
K+ ions in the cell, Na+ out of the cell
Action potential- A nerve impulse
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Approaches +40 millivolts (mV)
Inside of cell is positively charged, outside of cell is
negatively charged
Na+ ions in the cell, K+ out of the cell
Communication between Neurons
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Synapse:
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Neurotransmitters:
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The junction where a neuron
meets another cell
• Pre/Post synaptic cell
Signal molecules that bind to
receptor proteins on the
postsynaptic cleft and interact wit
the postsynaptic cell
• Can excite or inhibit the
activity of a cell it binds to
Membrane potential:
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+ ions enter neuron, an
action potential is
produced (excitation)
- ions enter neuron, an
action potential is
suppressed (inhibition)
Central Nervous System
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Consists of the brain and the spinal
cord.
Interprets and responds to
information from the environment and
from within the body.
BRAIN- The body’s main processing center.
Contains about 100 billion neurons.
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Cerebrum- The largest part of the
brain

Cerebellum- At the base of the brain,
regulates balance, posture, and
movement.

Brain stem- At the base of the brain, a
collection of structures leading to the
spinal cord.
• Upper- Thalamus and
Hypothalamus
• Lower- Midbrain, Pons, and
Medulla oblongata
SPINAL CORD- A dense cable of nervous
tissue that runs through the vertebral
column.
THE BRAIN
SPINAL CORD
Peripheral Nervous System
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Consists of 31 spinal nerves and 12
cranial nerves.
Connects the brain and the spinal
cord to the rest of the body
2 Divisions: Sensory and Motor
Sensory-Directs sensory information to the CNS
Motor-Carries out responses to sensory information.
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2 Principal Divisions:
•
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Somatic and Autonomic Nervous
systems
Somatic-Reflexes, some are involuntary
Autonomic-Involuntary responses
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2 Divisions:
•
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Sympathetic- Under stress
•
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Sympathetic and Parasympathetic
(Fight or Flight responses)
Parasympathetic- Normal conditions
•
When body is at rest (ie-sleep)
SENSORY RECEPTORS
Receptor type
Stimuli
Locations
Thermoreceptors
Temperature change
Skin, Hypothalamus
Pain receptors
Tissue damage
Tissues and Organs
Mechanoreceptors
Movement, Pressure,
Tension
Skin, Ears, Muscles
Photoreceptors
Light
Eyes
Chemoreceptors
Chemical
Tongue, Nose
Processing of Sensory Information
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4 main lobes
Frontal
•
•
•
•
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Motor function
Intellectual function
Speech
Smell
Occipital
• Vision
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Parietal
• Sensory
• Taste
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Temporal
• Hearing
THE EYE
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Pupil-Allows light to enter the
eye
Lens-Disk that focuses light
onto retina
Retina-Lining on back of the
eye that converts light energy
into electrical signals
Cornea-Transparent covering
on eye
Iris-Controls amount of light
that enters the eye
Rods-Respond to dim light
Cones-Respond to bright light
and allow color vision
Optic nerve-Exits back of the
eye and runs along base of
the brain to the thalamus
THE EAR
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Eardrum-Vibrates when sound
waves enter
Middle ear-Consists of 3 small
bones; hammer, anvil, and
stirrup
Cochlea-Fluid-filled chamber
that contain hair cells that
generate nerve impulses.
Auditory nerve-Sends
impulses to the brain
Semicircular canals-Fluid-filled
chambers in the inner ear that
maintain equilibrium

Located above cochlea
CHEMICAL SENSES
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CHEMORECEPTORS
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LOCATED ON THE
TONGUE
• 4 CHEMICAL
SUBSTANCES
OLFACTORY RECEPTORS
LOCATED IN THE
NASAL PASSAGE
• Sense of smell
Drugs and the Nervous System
Drug
Examples
Psychoactive
effects
Depressants
Alcohol, Sedatives
Decreased CNS activity
Stimulants
Cocaine, Crack, Nicotine
Increased CNS activity
Inhalants
Paint thinner, Glue
Disorientation,
Confusion
Hallucinogens
LSD, PCP, MDMA
Anxiety,
Hallucinations
THC
Marijuana, hashish
Short-term
memory loss
Narcotics
Heroin, Morphine, Codeine,
Opium
Sedation
Drug Addiction and Neuron Function
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Addiction- Physiological response caused by use
of a drug that alters the normal functioning of
neurons and synapses.
Tolerance- Increasing amounts of the drug are
needed to achieve the desired sensation.
Withdrawal- Emotional and physical symptoms
caused by removal of the drug from the body.
Depressant- Drug that decreases the activity of
the CNS
Stimulant- Drug that increases the activity of the
CNS