Transcript 9d. Know the functions of the nervous system and the role of

9d. Know the functions of the
nervous system and the role of
neurons in transmitting
electrochemical impulses.
9e. Know the roles of sensory
neurons, interneurons, and motor
neurons in sensation, thought
and response.
You are such a Neuron!
• Neurons: Basic Units of the Nervous System:
– __________________: conducts impulses
throughout the NS
• Made up of dendrites, a cell body, axon
• ____________________: branchlike cytoplasmic
extension of a neuron
– Transports impulses toward the cell
• ___________________: a single cytoplasmic extension
of a neuron
– Carries impulses away from a nerve cell
Neuron
Neurons
Neuron Background Info
• 3 types of neurons:
• __________________: carry impulses from
the body to the spinal cord and brain
• _______________________: found w/in
the brain and spinal cord.
– They process incoming impulses and pass
response impulses on to motor neurons
• ___________________: carry response
impulses away from the brain and spinal
cord to a muscle or gland.
The Spinal Cord
• The Spinal Cord
• The spinal cord is the main communications link
between the brain and the rest of the body.
• Certain information, including some kinds of
reflexes, are processed directly in the spinal cord.
• A __________________ is a quick, automatic
response to a stimulus.
The Peripheral Nervous System
• The Peripheral Nervous System
• The peripheral nervous system is all of the nerves
and associated cells that are not part of the brain and
the spinal cord.
• The peripheral nervous system includes cranial
nerves, spinal nerves, and ganglia.
• Ganglia are collections of nerve cell bodies.
Central Nervous System
Peripheral Nervous System
The Peripheral Nervous System
– What are the two divisions of the peripheral
nervous system?
• The sensory division of the peripheral nervous
system transmits ________________ from sense
organs to the central nervous system.
• The motor division transmits impulses from the
central nervous system to the ________________
or __________________.
The Peripheral Nervous System
• The motor division is divided into the somatic
nervous system and the autonomic nervous
system.
– The Somatic Nervous System
• The somatic nervous system regulates activities that are under
conscious control, such as the movement of skeletal muscles.
• Some somatic nerves
• A ______________ _________ includes a
sensory receptor, sensory neuron, motor neuron,
and effector that are involved in a quick response
to a stimulus.
Sensory neuron
Motor
neuron
Interneuron
Spinal cord
• Reflex Arc
The peripheral nervous system
transmits impulses from sense
organs to the central nervous
system and back to muscles or
glands. When you step on a tack,
sensory receptors stimulate a
sensory neuron, which relays the
signal to an interneuron within the
spinal cord. The signal is then sent
to a motor neuron, which in turn
stimulates a muscle in your leg to
lift your leg.
Effector (responding
muscle)
Sensory
receptors
The Peripheral Nervous System
– The Autonomic Nervous System
• The autonomic nervous system regulates
___________________ activities.
• The autonomic nervous system is subdivided into
two parts:
– _______________________ nervous system
– ______________________________ nervous system
The Peripheral Nervous System
• The sympathetic and parasympathetic
nervous systems have opposite effects on
the same organ system.
• These opposing effects help maintain
_________________________.
The Nerve Impulse
– The Resting Neuron
• When resting, the outside of the neuron has a net
_________________ charge.
• The inside of the neuron has a net
______________________ charge.
• The cell membrane is electrically charged because
there is a difference in electrical charge between its
outer and inner surfaces.
The Nerve Impulse
• The sodium-potassium pump in the nerve
cell membrane pumps sodium (_____) ions
out of the cell and potassium (____) ions
into the cell by means of active transport.
• As a result, the inside of the cell contains
more K+ ions and fewer Na+ ions than the
outside.
• Sodium-Potassium Pump
The Nerve Impulse
• More K+ ions leak across the membrane
than Na+ ions. This produces a negative
charge on the inside and a positive charge
on the outside.
• The electrical charge across the cell
membrane of a neuron at rest is known as
the __________________
________________.
The Nerve Impulse
• How is a nerve impulse transmitted?
– The Moving Impulse
• An impulse begins when a neuron is stimulated by
another neuron or by the
_______________________.
The Nerve Impulse
• At the leading edge of the impulse, gates in the
________________ channels open allowing
positively charged Na+ ions to flow inside the
cell membrane.
The Nerve Impulse
• The inside of the membrane temporarily
becomes more ________________ than the
outside, reversing the resting potential.
The Nerve Impulse
• This reversal of charges is called a nerve
impulse, or an _______________
______________.
The Nerve Impulse
• As the action potential passes, gates in the
__________________ channels open,
allowing K+ ions to flow out restoring the
negative potential inside the axon.
The Nerve Impulse
• The impulse continues to move along the
__________________.
• An impulse at any point of the membrane
causes an impulse at the next point along
the membrane.
The Nerve Impulse
– Threshold
• A stimulus must be of adequate strength to cause a
neuron to transmit an impulse.
• The minimum level of a stimulus that is required to
activate a neuron is called the
___________________.
• A stimulus that is stronger than the threshold
produces an impulse.
• A stimulus that is weaker than the threshold
produces no impulse.
The Synapse
• The Synapse
• At the end of the neuron, the impulse reaches an
axon terminal. Usually the neuron makes contact
with another cell at this site.
• The neuron may pass the impulse along to the
second cell.
• The location at which a neuron can transfer an
impulse to another cell is called a
_______________________.
The Synapse
• A Synapse
The Synapse
• The synaptic cleft
separates the
axon terminal
from the
____________ of
the adjacent cell.
Synaptic cleft
The Synapse
Vesicle
• Terminals contain
vesicles filled with
neurotransmitters.
• ________________
are chemicals used
by a neuron to
transmit an impulse
across a synapse to
another cell.
Neurotransmitter
The Synapse
• As an impulse
reaches a terminal,
vesicles send
neurotransmitters
into the synaptic
cleft.
• These
_____________
across the cleft and
attach to membrane
receptors on the next
cell.
Receptor
The Synapse
• Sodium ions then rush across the membrane,
stimulating the next cell.
• If the stimulation exceeds the cell’s threshold, a
new impulse begins.
• Moments after binding to receptors,
neurotransmitters are released from the cell
surface.
• The neurotransmitters may then be broken down
by enzymes, or taken up and recycled by the axon
terminal.
Summary
The __________________ ________________
controls and coordinates functions throughout the
body and responds to internal and external stimuli.
Neurons transmit electrochemical impulses
throughout the body. Sensory neurons carry
impulses from the sense organs to the spinal cord.
Motor neurons carry impulses from the brain and
spinal cord to muscles and glands.
___________________ connect sensory and
motor neurons and carry impulses between them.