Biology 1361: Neurons, Synapses and Signaling

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Neuron
Nerve cells that transfer information within the body
What two kinds of signals do neurons transfer?
Electrical (long-distance) Chemical (short-distance)
Where does the processing of information take place?
ganglia brain
Ganglia
Simple clusters of neurons
Brain
More complex cluster of neurons
What are the 3 stages of processing information?
Sensory input Integration Motor output
Sensory Neurons
Detect external stimuli (light, sound, touch, heat, smell, and taste) and internal conditions (blood pressure, muscle tension, and blood carbon dioxide levels) Part of sensory input stage.
Interneuron
- Integrate information sent to the brain or ganglia - Part of integration stage - Most neurons in the brain are interneurons
Motor Neuron
Motor output leaves from the brain or ganglia; triggers muscle or gland activity.
What are nervous systems consisted of? (2 things)
Central nervous system (CNS) Peripheral nervous system (PNS)
Central Nervous System (CNS)
Where integration takes place Includes brain and spinal cord
Peripheral Nervous System (PNS)
brings information in and out central nervous system (CNS)
What is the structure of a neuron?
cell body dendrites axon axon hillock
Cell body
Where most of a neuron's organelles (including nucleus) are
Dendrites
Highly branched extensions that RECEIVES signals from other neurons
Axon
Longer extension that TRANSMITS signals to other cells at synapses.
Axon Hillock
connection between axon and cell body signals that travel down the axon are generated here.
Synapse
junction between an axon and cell body
Synaptic Terminal
passes information across the synapse in the form of chemical messengers called neurotransmitters.
Neurotransmitters
pass information from the transmitting neuron to the receiving cell.
Presynaptic Cell
A neuron
Postsynaptic Cell
A neuron, muscle, or gland
Glia
supporting cells nourishes or insulates most neurons
membrane potential
charge difference, or voltage, across the plasma membrane
resting potential
a resting neuron that isn't sending a signal. typically between -60 and -80 mV (millivolts)
is K high inside or outside cell?
inside
is Na high inside or outside the cell?
outside
is anions high inside or outside the cell?
outside
gated ion channels
open and close in response to stimuli the opening and closing of these channels change the membrane potential
When gated K+ channels open, K+ diffuses out, making the inside of the cell more negative. What is this an example of?
hyperpolarization
What is hyperpolarization (-)?
the increase in the magnitude of the membrane potential makes the inside of the membrane more negative (-)
what is depolarization (+)?
the reduction in the magnitude of the membrane potential makes the inside of the membrane LESS negative
Na+ channels open and Na+ diffuses into the cell. What is this an example of?
depolarization
What are the 5 major classes of neurotransmitters?
acetylcholine biogenic amines amino acids neuropeptides gases
electrical synapses
the electrical current flows from one neuron to another
chemical synapses
chemical neurotransmitter carries information across the gap junction
Most synapses are chemical or electrical?
chemical
when most voltage-gated Na+ and K+ channels are close, but some K+ channels (not voltage-gated) are open. is that action potential or resting potential?
resting potential
When an action potential is generated
voltaged-gated Na+ channels open first and Na+ flows into the cell. rising phase. falling phase. undershoot
What happens during the rising phase?
the threshold is crossed and the membrane potential increases
what happens during the falling phase?
the voltage-gated Na+ channel is inactivated voltage-gated K+ channels open and K+ flows out of the cell.
what happens during the undershoot phase?
membrane permeability to K+ is higher than at rest, then voltage-gated K+ channels close, resting potential is restored

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