31.1
The Function of the Nervous System:
Send and receive messages within the body
Respond to stimuli
Neuron- basic unit of structure and function of
the nervous system
31.1
peripheral nervous system: network of nerves and supporting cells that
carries signals into and out of the central nervous system
central nervous system: includes the brain and spinal cord; processes
information and creates a response that is delivered to the body
cell body: largest part of a typical neuron, contains the nucleus and much
of the cytoplasm
Dendrite: extension of the cell body of a neuron that carries impulses
from the environment or from other neurons toward the cell body
Axon: long fiber that carries impulses away from the cell body of a
neuron
myelin sheath: insulating membrane surrounding the axon in some
neurons
31.1
action potential: reversal of charges across the cell
membrane of a neuron; also called a nerve impulse
Threshold: minimum level of a stimulus that is required to
cause an impulse
Synapse: point at which a neuron can transfer an impulse
to another cell
Neurotransmitter: chemical used by a neuron to transmit
an impulse across a synapse to another cell
31.1
Types of Neurons:
Sensory Neurons: Impulse from sense organ to
spinal cord/brain
Motor Neurons: Impulse from brain/spinal cord to
muscles and glands
Interneurons: Connect sensory and motor neurons
31.1
Nerve Transmission:
Messages are electrical and chemical signals
An electric charge is conducted down a neuron
(Dendrite to axon)
Axon is covered in an insulating layer called a myelin
sheath to speed up impulses
As it reaches the end of the axon, chemicals
(neurotransmitters) are released across the
synapse (gap between neurons) to the next neuron
The message continues neuron to neuron
31.2 Vocab
Reflex: quick, automatic response to a stimulus
Cerebrum: part of the brain responsible for
voluntary activities of the body; the “thinking”
region of the brain
cerebral cortex: outer layer of the cerebrum of a
mammal’s brain; center of thinking and other
complex behaviors
31.2 Vocab
Thalamus: brain structure that receives messages from the sense organs
and relays the information to the proper region of the cerebrum for
further processing
Hypothalamus: structure of the brain that acts as a control center for
recognition and analysis of hunger, thirst, fatigue, anger, and body
temperature
Cerebellum: part of the brain that coordinates movement and controls
balance
brain stem: structure that connects the brain and spinal cord; includes
the medulla oblongata and the pons
Dopamine: neurotransmitter that is associated with the brain’s pleasure
and reward centers
31.2 Central Nervous System
Brain- control center; transmits and receives
messages
Cerebrum
Cerebellum
Brain Stem (midbrain, pons, medulla oblongata.)
Spinal Cord- connects brain with rest of the
nervous system
31.2
Addiction and the Brain:
Dopamine – neurotransmitter released with
pleasurable activities
Addictive drugs cause large release of
dopamine (resulting in “high”)
Brain reacts by reducing number of receptors
for dopamine  normal activities no longer
produce the pleasure they once did
31.3 Vocab
somatic nervous system: part of the peripheral
nervous system that carries signals to and from skeletal
muscles
reflex arc: the sensory receptor, sensory neuron, motor
neuron, and affecter that are involved in a quick response
to a stimulus
autonomic nervous system: part of the peripheral
nervous system that regulates activities that are
involuntary, or not under conscious control; made up of
the sympathetic and parasympathetic subdivisions
31.3
Peripheral Nervous System:
Link between the central nervous system
and the rest of the body
Network of nerves throughout the body
*Made of many neurons
31.3
Sensory Division:
Transmits impulses from sense organs to central nervous system
Uses sensory receptors
Chemoreceptors
Photoreceptors
Mechanoreceptors
Thermoreceptors
Pain receptors
31.3
Motor Division:
Transmits impulses from central nervous system
to muscles or glands
Somatic nervous system: regulates activities under
conscious controlAutonomic nervous system:
regulates activities that are automatic or involuntary
Autonomic nervous system: regulates activities that
are automatic or involuntary
31.4 Vocab
taste bud: sense organs that detect taste
Cochlea: fluid-filled part of inner ear; contains nerve cells
that detect sound
semicircular canal: one of three structures in the inner ear
that monitor the position of the body in relation to gravity
Cornea: tough transparent layer of the eye through which
light enters
Iris: colored part of the eye
31.4 Vocab
Pupil: small opening in the iris that admits light into the eye
Lens: structure in the eye that focuses light rays on the retina
Retina: innermost layer of the eye; contains photoreceptors
Rod: photoreceptor in the eyes that is sensitive to light but can’t
distinguish color
Cone: in the eye, a photoreceptor that responds to light of
different colors producing color vision
31.4
Senses:
Vision- eyes
Hearing and Balance- ears
Smell and taste- nose and mouth
Touch- skin
31.4
Hearing/balance
Smell
Mechanoreceptor
Chemoreceptor
Taste
Touch
Mechanoreceptor
Pain receptor
Thermoreceptor
Vision
Photoreceptor