Download Nervous System Function

Nervous System Function
Neurons and Neurotransmitters
Nervous System - Pathways
Sensory
Receptors
Somatic Nerves
(muscles)
Autonomic Nerves
(glands/organs)
Sensory
Nerves
Brain and
Spinal Cord
Motor
Nerves
Nervous System - Pathways
Sensory
Nerve
Interneuron
Motor
Nerve
Supporting Cells (not neurons)
Microglial – phagocytize
bacterial cells + debris
Oligodendrocytes –
produce myelin sheath
Astrocytes – link blood
and neurons helping in
metabolism
Ependymal cells – cover
inside of the ventricles
Neurons – Basic Structure
Nervous cells that conduct
nerve/electrical impulses
Neuron Structures
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Dendrite = receptive region
conducts impulse to cell body
Axon = conducts impulse
away from cell body
Myelin sheath = cells that
insulate nerve impulse
increasing its velocity
Node of Ranvier = narrow
gap between cells of myelin
sheath
Synapse = empty
space/junction between
neurons
Types of Neurons
Multipolar = many
dendrites + one axon;
found in CNS and
motor neurons
Bipolar = one dendrite
and one axon; found
in eye and nose
Unipolar = single
process extending from
cell body; found in
sensory neurons
Resting Membrane Potential
Neuron is polarized at rest
Interior is negative/Exterior is positive
Na+/K+ pump maintains polarity by
moving Na+ out and K+ in
K+ can leave but Na+ can’t enter
Action Potential
Neuron depolarizes to send
an electrical nerve impulse
Neuron becomes positive
inside and negative outside
as a result of ions moving
The momentary
depolarization is quickly
reversed and the neuron
becomes re-polarized
The depolarization is called
an action potential
Action Potential
Action Potential is
caused by movement
of ions
Depolarization =
Steps 1 + 2
Action Potential =
Step 3
Repolarization =
Steps 4, 5, 6
Action Potential
The resting membrane
potential is negative and cell
is polarized.
Stimulus causes Na+ and
then K+ gates to open, inside
of cell becomes positive and
is depolarized.
Na+ gates close and K+ gates
open, inside becomes
repolarized as K+ leaves cell.
Action Potential to Nerve Impulse
Action potential produces a
local current
This causes depolarization on
adjacent membrane
The wave of action potentials
travels down the neuron
producing a nerve impulse
Action Potentials and Myelinated Neurons
Myelinated neurons allow action potentials to ‘jump’ between
unmyelinated gaps (Node of Ranvier) along the neuron
Action potential and nerve impulse are faster
Myelin sheath acts as insulation prevents depolarization
Nodes of Ranvier are not insulated and can depolarize as a result
Neurotransmitters
Neurotransmitters are
chemicals produced by
the neuron and stored in
sacs at axon terminal
Action potential
stimulates release of
neurotransmitters into
the synapse (gap between
neurons)
Neurotransmitters bind
to receptor sites on
adjacent neuron
Neurotransmitters
Neurotransmitters change
the shape of receptors
allowing movement of ions
into neuron
Movement of positive ions
(Na+) causes depolarization
and an action potential
Neurotransmitters that
allow this are called
stimulatory
Neurotransmitters
Neurotransmitters can
change the shape of
receptors preventing
movement of ions into
neuron
Causes the interior of
neuron to become more
negative, preventing an
action potential
Neurotransmitters that do
this are called inhibitory
Neurotransmitters