Download The Nervous System

The Nervous System
Introduction
• In all animals, except the sponges, responses to
stimuli depend on the activities of networks of
nerve cell, or neurons.
• Neurons are specialized cells for transmitting
neural signals, which are electrical signals and
chemical messages.
Parts of the Neuron
• Dendrites: projections used to conduct electrical
messages received from other neural cells to the
cell body.
• Cell Body: Contains lots of ribosomes and RERs
to make proteins needed for the neuron; also
passes received messages out through the axon.
Parts of the Neuron
• Axon: long projection that conducts electrical
messages away from the cell body; connect with
other neurons/cells at synapses.
• Schwann Cells: a form of glial cells that make up
the myelin sheath; support and protect the axon.
Parts of the Neuron
• Myelin Sheath: an electrical insulating cover of the
axon that speeds up the transmission of electrical
signals. Majority of neurons are myelinated.
• Node of Ranvier: gaps in the myelin sheath that
allow for saltatory conduction of an action potential
(i.e. the signal jumps from gap to gap)
Nervous System
• In most animals,
neurons and the
supporting tissue are
organized into a
nervous system.
• The nervous system
works in conjunction
with many of the
body’s other systems
in order to maintain
homeostasis.
Nervous System
•
The nervous system
contains 2 distinct parts:
1) Central Nervous System
(CNS)
• Contains the nerves in
your brain and spinal
cord.
• Has control over the
majority of body
processes as it controls
the peripheral nerves.
Nervous System
2) Peripheral Nervous
System (PNS):
• Contains all the nerve
cells that are not
associated with the CNS.
• Autonomic division
controls all involuntary
processes in our bodies.
• Somatic division controls
all voluntary processes in
our bodies.
Neural Signalling
• An animal is constantly
being bombarded with
stimuli.
• Appropriate response
to stimuli depends on
neural signalling, which
is communication
between neurons.
Neural Signalling
•
Neural signalling
involves four
processes:
1)
2)
3)
4)
Reception
Transmission
Integration
Action
Neural Signalling
•
•
Reception is the
process of detecting
stimuli.
It is the job of
special neurons
called sensory
neurons (unipolar
neurons) or organs
like the eyes and
ears.
Neural Signalling
•
•
•
Transmission is the
process of sending
messages along the
nervous system usually
to or from the brain.
Sensory neurons carry
messages to the central
nervous system.
Afferent neurons are
any neurons that carry
messages to the CNS.
Therefore sensory
neurons are afferent
neurons.
Neural Signalling
•
•
Integration involves
sorting and interpreting
messages and
determining the
appropriate response.
Interneurons (bipolar
neurons) do this job.
Their cell body and
axon are located within
the CNS.
Neural Signalling
•
•
•
Action involves the
actual response to
stimuli by the body’s
effectors.
Motor neurons
(multipolar neurons) do
this job. They carry
messages away from
the CNS to effectors like
muscles.
Efferent Neurons are
any neurons that take
messages away from
the CNS, therefore
motor neurons are
efferent neurons.