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Unformatted text preview: Chapters 4&5: Neural Communication I
Neurons of nervous system (NS)
Electrical activity of neurons
III. Synaptic transmission between neurons
I. I. Neurons of nervous system (NS)
I. Two divisions of the nervous system:
CNS: the brain and the spinal cord.
PNS: the rest of the NS.
Two types of cells of the nervous system:
Nerve cells: neurons.
Supporting cells. According to the functions, 3 types of neurons.
According Sensory neurons (Afferent):
gather Motor neurons (Efferent):
control the muscles
connect sensory and motor neurons
connect Four basic structures of neurons. Cell body (Soma): the metabolic center. Dendrites: receive synaptic messages. Axon: carries the nerve impulse from the
cell body to the terminal buttons. Axons are
often coated with myelin sheath with a
small portion of uncoated axon between the
segments of myelin sheath—node of
Ranvier. Terminal buttons: release neurotransmitters
(transmitter Internal structures of neurons Membrane: consists of a double layer of
lipid molecules and contains proteins that
perform the following functions:
• detect chemicals outside the cell
• control access to the cell
• transport molecules into or out of the cell Cytoplasm: a jelly like substance. Mitochondria: break down nutrients, and
provide the cells with energy.
provide Enzymes: cause molecules to join together
or to be split apart.
or Nucleus: contains chromosomes
genes II. Electrical activity of neurons
A. Basic concepts Membrane potential: an electrical charge. Resting potential: -70mV with the inside of
the neuron being negative.
the Action potential: rapid reversal of the
membrane potential from -70mV to +50mV
to -70mV to overshooting the resting
potential and back to -70mV.
potential Depolarization: a reduction of the membrane
Depolarization: potential of a neuron from its resting potential.
potential Hyperpolarization: an increase in the
Hyperpolarization: membrane potential of a neuron from its
resting Threshold of excitation: the voltage level that
Threshold triggers an action potential.
triggers B. Reasons for membrane potential
B. Force of diffusion: the tendency for molecules
or ions to distribute themselves evenly.
or Electrostatic pressure: the force exerted by
ions to repel or attract each other.
ions Intracellular fluid: the fluid within cells
K+,AK+,A Extracellular fluid: the fluid surrounding cells
Na+,ClNa The sodium-potassium pump: pushing 3 Na+
out of the cell for every 2 K+ pushed in.
pushed C. Movements of ions during the action potential
C. Ion channel: protein molecules containing
Ion passages that can open or close.
passages Voltage-dependent ion channels: ion channels
Voltage-dependent that are opened by changes in the membrane
Action Potential D. Conduction of the action potential
D. All-or-non law: an action potential either
All-or-non occurs or does not occur.
occurs Rate law: the rate of firing provides variable
information. Saltatory conduction: conduction of an action
Saltatory potential from node of Ranvier to node of
Ranvier down a myelinated axon.
Ranvier Saltatory conduction III. Synaptic transmission between neurons
A. Structures of synapses: Synapse: the junction between the terminal
button and the membrane of another neuron.
button Synaptic cleft: a small gap between neurons. Presynaptic membrane: the membrane of
terminal Postsynaptic membrane: the membrane of
Postsynaptic receiving neurons.
receiving Synaptic vesicles: small containers with
neurotransmitter. Release zone: the region of the presynaptic
Release membrane from which the neurotransmitter is
released. B. Postsynaptic potentials
B. Postsynaptic receptors: protein molecules that
Postsynaptic are form-fitted to the molecular shape of the
matching Postsynaptic potential: a brief change in the
Postsynaptic membrane potential of the postsynaptic cell.
membrane EPSPs (excitatory): depolarization produced
EPSPs by the opening of neurotransmitter-dependent
Na+ or Ca2+ channel.
Na IPSPs (Inhibitory): hyperpolarization produced
IPSPs by the opening of neurotransmitter-dependent
K+ or Cl- channel. Neural integration: the interaction of the
Neural effects of excitatory and inhibitory synapses
on a particular neuron.
on C. Termination of the postsynaptic potential
C. Reuptake: removal of neurotransmitter from
Reuptake: the synaptic cleft by the terminal buttons.
the Enzymatic deactivation: destruction of a
Enzymatic neurotransmitter by an enzyme
(Acetylcholine). D. Autoreceptors:
D. Receptors on the terminal button that regulate
Receptors the release of neurotransmitter.
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- Fall '10