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What does the CNS consist of?
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What does the PNS consist of?
- Everything but the brain and spinal cord
- All nerves going throughout the body
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What are the 2 divisions of the PNS?
- Autonomic nervous system
- Somatic nervous system
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Which PNS divison does the adrenaline response come from?
Autonomic NS
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Which cells make up the CNS?
- 10% Neurons
- 90% Glia cells
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What are neurons?
Communication cells in nervous system
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What are glia?
Support cells for nerve cells
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What are the different kinds of glia cells in the CNS?
- Astrocytes
- Oligodendrocytes
- Microglia
- Ependymal cells
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What do ependymal cells do?
- Create barriers between compartments
- Source of neural stem cells
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What do astrocytes do?
- Glia support cells
- Source of neural stem cells
- Take up K+, water, nt's
- Secrete neurotrophic factors
- Help form blood-brain barrier
- Provide substrates for ATP production
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What do oligodendrocytes do?
- Wrap around neuron
- Produce myeline sheaths
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What do microglia do?
- Brain's immune system
- Act as scavengers
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What's a synapse?
The region where an axon terminal communicates with its post synaptic target cell
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What purpose do dendrites, cell body, and presynaptic axon terminals fulfill?
- Dendrites = input signal
- Cell body = integration
- Axon terminal = output signal
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Glial cells are found in which system(s)?
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Glial cells are found in the PNS as what?
- Schwann cells
- Satellite cells
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What do schwann cells do?
- Form myelin sheaths
- Secrete neurotrophic factors
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What do satellite cells do?
Support cell bodies
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Astrocytes play a role in neurological __________, like __________.
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What was Marian Diamond's study with Albert Einstein's brain?
Studied neuron:glia ratios of his brain compared to other males
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What were Prof. Diamond's findings in the Einstein experiment?
- Einstein's neuron:glia ratio was lower than the others in left area 39 but didn't really differ in other areas
- So he had more glial cells in the left inferior parietal area
- This area is part of the association cortex
- Rats with enriched environments developed more glial cells for each neuron
- Rats in impoverished environments had fewer glial cells relative for each neuron
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What is the assocation cortex?
Region of the brain responsible or incorporating and synthesizing info from multiple other brain regions
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What kind of signal flows down the axon of a neuron?
Electrical signal
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How does info flow through dendrites?
Collects electrical signals
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How does info flow through the cell body?
Integrates incoming signals and generates outgoing signal to axon
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How does info flow through axon?
Passes electrical signals to dendrites of another cell or to an effector cell
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Neurons have specialized connections called __________, for ___________.
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What is neuron communication based on?
Changes in the membrane's permeability to ions
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What are the 2 types of membrane potentials?
- Graded potentials
- Action potentials
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How is current formed?
Mvmt of ions across the plasma membrane (PM)
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What is resting membrane potential?
- Potential difference across PM at rest
- Passive ion movement down the electrochemical gradient
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What is extracellular defined as?
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How are ion gradients maintained?
Establishment of resting membrane potential
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How is the resting membrane potential established?
Na+/K+ pump establishes concentration gradient generating a small negative potential
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How much ATP does the Na+/K+ pump use?
Up to 40% of ATP produced by the cell
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How do you calculate an ion's equilibrium potential?
Using Nernst Equation
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What is Nernst Equation?
- Describes the membrane potential that a single ion would produce if the membrane were permeable to only that ion
- E ion = (61/z)log([ion out]/[ion in]) in mV, at 37 degrees
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What do the variables stand for in the Nernst Equation?
- z = the valence of the ion
- 61 is from R = gas constant, T = temp, F = Faraday constant
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What are the equilibrium potentials of K+, Na+, and Cl-?
- K+ = -90 mV
- Na+ = 60 mV
- Cl- = -63 mV
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How is information transmitted?
Through transient changes in membrane potential
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What happens when something depolarizes?
- Occurs when ion mvmt reduces the charge imbalance
- Membrane potential increases
- Peak in graph
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What does overshoot refer to?
The development of a charge reversal
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What is repolarization?
Mvmt back toward the resting potential
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What happens when something hyperpolarizes?
- Development of even more negative charge inside the cell
- Membrane potential decreases
- Dip in graph
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Why would a cell be "polarized"?
B/c its interior is more negative than its exterior
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What is electrical potential difference?
Potential to do work by separated opposite charges (mV)
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What is the resting membrane potential in neurons?
~-70 mV
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What are the 2 forms that electrical signals occur in?
- Graded potentials
- Action potentials
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What are graded potentials?
Local decremental change in the membrane potential
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What are action potentials?
Large global alteration in membrane potential
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The size of a graded potential is proportionate to what?
The intensity of the stimulus
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What happens to graded potentials as they move over distance?
They decay
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What are the two kinds of graded potentials?
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What does an excitatory graded potential mean?
Action potential is more likely
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What does an inhibitory graded potential mean?
Action potential is less likely
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The size of a graded potential is proportional to what?
The size of the stimulus
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What are the two ways neurons convey information with potentials?
- Graded potential changes- neural encoding of sensory stimuli
- Excitable membranes use graded potential summation to ecode a binary spike system
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What is the binary spike system encoded by graded potential summation called?
Action potentials
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