Download The Nervous System

The Nervous System
Part I
“Not to be confused with Anxiety!”
Physiology Standards 9 a-e
“Coordinated structures and
systems within the body help it to
maintain homeostasis despite the
changes in the outside
environment (homeothermic)”
Physiology Standards 9 a-e
• a) Know how major body systems compliment
each other to provide the body with Oxygen and
nutrients while removing waste and Carbon
Dioxide
• b) Know how the nervous system allows different
parts of the body to communicate and receive
information from the outside environment
• c) Know how the nervous and endocrine
systems regulate conditions in the body using
feedback loops
Physiology Standards 9 a-e
• d) Know the functions of the nervous system
and the role of neurons in transmitting
impulses
• e) Know the role of sensory neurons,
interneurons, and motor neurons in
sensation, thought, and response
• The Nervous System controls
and coordinates functions
throughout the body and
“responds” to internal and
external stimuli
– “Your nervous system is how your body
communicates within itself and with the
outside world”
• Stimulus – (pl. stimuli ) is a change in
environment such as a smell or a noise
that is “detected” by an organism
Neurons
• The nervous system is made up of
millions of cells called neurons
• Messages carried by the nervous
system are chemical and electrical
signals called impulses
• The cell that transmits impulses is
called a neuron
Neurons
• There are three types of neurons:
– Sensory neurons carry impulses
from the sense organs to the spinal
cord and the brain
– Motor neurons carry impulses from
the brain and spinal cord to muscles
and glands
– Interneurons connect sensory and
motor neurons and carry impulses
between them
Neurons
• The largest part of a typical
neuron is called the cell body
– Contains the nucleus
– Where most metabolic activity takes
place
• Spreading out from the cell body
are short, branched extensions
called dendrites
– Detect impulses from the
environment to the cell body
Neuron Structure
Neurons
• The long fiber that carries
impulses away from the cell body
is the axon
– Ends in a series of small areas called
axon terminals
– Some axons have an insulating
membrane called the myelin sheath
• The sheath leaves exposed parts of the
axon called nodes where a nerve
impulse can “jump” from one node to
the next
Neuron Structure
Nucleus
Axon terminals
Cell body
Myelin sheath
Nodes
Axon
Dendrites
The Synapse
• At the end of an axon the
nerve impulse reaches the
axon terminal
• The space between two
neurons is called the
synapse
• A vesicle releases a
neurotransmitter that
communicates the
message to the next
neuron
Direction of
Impulse
Axon
Vesicle
Axon
terminal
Neurotransmitter
The Synapse
Nervous System Divisions
Brain
Spinal
cord
• Central Nervous
System: “CNS”
– Composed of the Brain
and the Spinal Cord
• Peripheral Nervous
System: “PNS”
Peripheral
Nerves
– Composed of all of the
nerves that run
throughout the body
– Responsible for
gathering stimuli to be
sent to the CNS