Neurons Flashcards
Where is the negative and positive charge in a cell membranes resting potential?
Outside the cell is positive
Inside the cell is negative
What is the term for an electrically charged cell, it is said to be….
Polarized
If positive charges flow into a cell, the potential inside the cell becomes? Which is called?
Less negative
Depolarization
If positive charges flow out of a cell, the potential becomes? What is this called?
More negative
Repolarization
If positive charges flow out of a resting cell or negative charges flow in, what happens to the cells potential? What is this called?
Becomes more negative
Hyperpolarization
Movement of what to the inside of a cell causes depolarization?
Na+ ions
Movement of what to the outside of a cell causes repolarization?
K+
What establishes the resting membrane potential?
The asymmetric distribution on Na+ and K+ ions.
The membrane is selectively permeable to K+ (it’s allowed to leave), but impermeable to Na+
SHE SAYS IT’S K+ LEAKINESS
After a cell repolarizes by K+ ions leaving through the channels, what activates to establish the RMP?
The Na/K pump
How much of each ion does the Na/K pump move?
3 Na+ out for every 2 K+ in
What allows the small amount of K+ to leave the cell and create the RMP?
Non-gated channels are always open and allow “leaking”
What is the difference between the ion movement that occurs with depolarization/repolarization vs the Na/K pump?
During depolarization and repolarization (even RMP) ions are moving down their concentration gradient. The Na/K pump moves ions against their concentration gradient which requires energy (active transport).
Name the 3 states of the gated Na+ channels
Resting state (she also calls this potentially active or closed)
Active state
Inactive state
Describe the resting state of the gated Na+ channel
She also calls this potentially active and closed
The Na channel is closed, and can be stimulated
Describe the active state of the Na+ gated channel
Threshold potential has been reached, the Na+ channel opens and allows Na+ to flow into the cell (depolarization)
Describe the inactive state of the gated Na+ channel
The inactivation plug closes and remains that way until RMP is reached. This state can not be stimulated no matter the stimulus.
Where is the inactivation gate in the gated Na+ channel?
It is the intracellular gate
What is an absolute refractory period and when does it occur?
Period of time when no matter the stimulus, a second action potential can not occur. It occurs during the time when Na+ channels are inactivated.
What is a relative refractory period and when does it occur?
Represents a time period in which a second action potential can occur, but only with a Supra threshold stimulus. This occurs immediately following absolute refractory period (RMP -> hyperpolarization).
On an action potential graph, at what point does the inactivation gate close?
At the peak
When is the Na/K pump activated?
At the completion of repolarization
What conducts the impulse away from the cell body of a neuron?
The axon
How many axons does each cell have?
Only one
Where are sodium channels principally located on the neuron?
On the axon
What is myelin?
A lipid substance insulator that may cover an axon
What is the purpose of myelin?
It prevents ions from flowing, so conduction down the axon is faster
What type of conduction occurs on myelinated fibers?
Saltatory conduction
What are the interruptions in the myelin sheath called?
Nodes of Ranvier
How does saltatory conduction work?
The conduction jumps from one node of Ranvier to the next, this increases the speed of conduction down the axon compared to a non-myelinated fiber
What is a synapse?
The junction of 2 neurons
-small space
What end of a neuron is presynaptic and what end is postsynaptic?
Presynaptic: axon
Postsynaptic: dendrite
How is an electrical impulse conducted across the synapse?
It is converted into a chemical signal (neurotransmitter)
Transmission of an impulse flows in what way?
One direction
Axon to dendrite
What is an EPSP?
Excitatory post synaptic potential: it increases the cells charge to less negative
What is threshold potential?
The point at which a change in polarity must reach to cause an action potential
What is the all or none principle?
An EPSP must reach threshold potential, and when it does the action potential propagates across the entire cell membrane
What causes postsynaptic potentials?
Neurotransmitters
EPSP increases permeability of what ion?
Sodium
What is an IPSP?
Inhibitory post synaptic potential
What ions permeability is increased by an IPSP?
Potassium (out)
Chloride (in)
What state does an IPSP create?
Hyperpolarization
Where is acetylcholine used as a neurotransmitter?
CNS
ANS
Neuromuscular junction
Where is dopamine a neurotransmitter?
Brain
Kidneys
Where is Norepinephrine a neurotransmitter?
CNS
ANS
Where is Serotonin a neurotransmitter?
CNS
Where is GABA a neurotransmitter?
CNS
Where is Glycine a neurotransmitter?
Spinal cord
Where is Substance P a neurotransmitter?
CNS
Where are opioid peptides a neurotransmitter?
CNS
What is presynaptic inhibition?
Reduced levels of calcium can inhibit release of neurotransmitters from vesicles because calcium causes their release
How can serum potassium levels affect RMP?
If serum K+ is low, more K+ will leak out of cell due to concentration gradient making the cell more negative (hyper polarized).
If serum K+ is high, less K+ will leak out of the cell due to concentration gradient this makes RMP less negative (accommodation)
What are the 3 classes of neurons?
Sensory (afferent)
Interneurons (association neurons)
Motor (efferent)
What is the function of sensory neurons?
Afferent - send information to CNS
What is the function of an interneuron (integrative)? Where are they found
Association neuron that connects neurons
They are confined to the CNS
What is the function of motor neurons?
Conduct signals from the CNS to effectors
What is a neuron?
An excitable function unit of the nervous system
What is a neuroglial?
A supportive non-excitable cell in the nervous system
What are there more of in the nervous system neurons or neuroglial cells?
Neuroglial cells
Name the 4 parts of a neuron
Cell body (AKA soma)
Axon
Dendrites
Myelin (not all neurons have)
What is a cluster of neuron cell bodies called when it is in the CNS?
Nuclei
What is a cluster of neuron cell bodies called when it is in the peripheral nervous system?
Ganglia
What direction does the axon carry the signal?
Away from the cell body
In the CNS what neuroglial cell makes myelin?
Oligodendrocyte
In the peripheral nervous system what type of neuroglial cell makes the myelin?
Schwann cell
What makes up Grey matter?
Cell bodies and unmyelinated axons
What makes up White matter?
Myelinated axons
What are bipolar neurons and where are they found?
They have one axon and one dendrite
They are interneurons which are limited to the CNS
What are Unipolar (peudounipolar) neurons are where are they found?
They have one process that divides into axon and dendrite
They are sensory neurons
What are multipolar neurons and where are they found?
They have one axon and many dendrites.
They are Motor neurons
Which neuroglial cell can create myelin around several axons?
Oligodendrocytes in the CNS
What is a microglial cell and where is it found?
A neuroglial cell in the CNS that is a phagocyte
What is a Ependymal cell and where is it found?
A neuroglial cell in the CNS that lines the ventricles and secretes CSF
What is an Astrocyte and where is it found?
A neuroglial cell in the CNS that provides structural support and responds to injury. It also lines the BBB.
What is the most numerous neuroglial cell in the CNS?
Astrocytes
What is a Schwann cell and where is it found?
A neuroglial cell in the PNS that forms myelin around axons in the PNS. Forms the sheath of Schwann/neurilemma
What is a capsular cell and where is it found?
A neuroglial cell of the PNS that supports ganglia
What is the chief non-excitable cell of the PNS?
Schwann cells
Name the layers of a nerve fiber starting with the axon
Axon Myelin (if it has it) Neurilemma Endoneurium Perineurium Epineurium
What are the 3 classifications of nerves?
Sensory
Motor
Mixed
What size nerves conduct faster larger or smaller?
Larger
What are CNS bundles of nerves called?
Tracts
