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134 Cards in this Set
- Front
- Back
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Nervous System |
master controlling center and communicating center of the body |
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Nervous system cells communicate by
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ELECTRICAL signals that are RAPID and cause immediate response
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3 Functions of the Nervous System |
1. Sensory input 2. Integration 3. Motor output |
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Sensory Input |
monitoring stimuli occurring inside of the body |
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Integration |
interpretation of sensory input |
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Motor output |
response to stimuli by activating effector organs |
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Overall organization of the Nervous System |
2 Cells types CNS PNS |
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2 principle cell types of the nervous system |
1. Neuroglial 2. Neuron
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Neuroglial Cells |
cells surrounding and supporting neurons |
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Oligodendrites |
Found in CNS Form Myelin Sheath |
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Astrocytes |
Found In CNS Star shaped cell (Processes Anchors neuron to capillaries recaptures released neurotransmitters, Maintains blood brain barrier, structural support)
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Ependymal cells |
Ciliated cells that line chamber filled with cerebral spinal fluid (choroid Plexus)
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Microglial Cells |
oval cell, long thorny processes, pathogens |
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CNS |
Brain Spinal cord |
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Brain |
Master Control Center |
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Spinal Cord |
connects brain to body |
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Peripheral Nervous System |
PNS- nerves extending from brain and spinal cord |
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2 Divisions of PNS |
Afferent Efferent |
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Afferent |
Sensory neurons carry info to CNS (Somatic, Visceral, Special sense) |
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Efferent |
Motor Division; carry commands away from CNS to effectors (somatic and Autonomic) |
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Somatic Nervous system |
controls voluntary muscle contractions |
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Autonomic Nervous System |
involuntary smooth muscle, cardiac muscle, and glands (Sympathetic and parasympathetic) |
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Schwann Cells |
Found in PNS Forms Myelin Sheath |
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Satellite cells |
surround cell bodies in PNS and function similar to astrocytes |
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Neurons |
excitable cells that transmit electrical signals |
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Anatomy of Neuron |
Cell body Dendrites Axon hillock Axon Nodes of Ranvier Telodendrites Axon Terminals
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Cell Body |
contains nucleus and organelles |
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Dendrites |
branching extensions; receive neurotransmitters from presynaptic neuron and transmit GRADED potential TOWARDS cell body |
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Axon Hillock |
where cell body tapers into axon, site where action potential originates |
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Myelin Sheath |
formed by schwann cells wrapping around axon in concentric layers of plasma membrane |
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Nodes of Ranvier |
gaps in myelin sheath |
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Telodendrites |
distant branches of axon |
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Axon |
single process extending from cell body, transmits ACTION potential AWAY |
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Axon Terminals |
Enlarged distal ends containing secretory vesicles filled with neurotransmitters |
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Synapses |
junctions between neurons |
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Why do synapse function as a decision point? |
it can be excitatory or inhibitory |
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Where do synapses occur? |
between axon terminals and .... Cell body Dendrite Axon Hillock Muscle Gland |
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Presynaptic Neuron |
transmits impulses TOWARDS the Synapse, Axon vesicles with neurotransmitters |
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Synaptic Cleft |
fluid filled space between pre and post synaptic neuron |
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Postsynaptic Neuron |
transmits impulses AWAY from synapse, has receptors for neurotransmitters |
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Principles of Electricity |
Electricity Voltage |
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Electricity |
when opposite charges are separated they contain potential energy ; coming together energy is released |
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What is the separation of electrical charges in a cell by the plasma membrane called? |
Membrane Potential |
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Voltage |
measurement of potential energy created by charge of separation |
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Neurons Voltage in measured in what? |
Millivolt |
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What is a millivolt? |
1mV= 1/1000V |
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What 2 things does the measurement Voltage depend on? |
1. quantity of charges 2. Distance between the charges |
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4 Types of Ion Channels found in Neurons |
1. Ligand-Gated Channels 2. Mechanically Gated 3. Voltage Gated 4. Leaky Channel |
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Ligand Gated Channel |
Chemically Gated, opens when neurotransmitters bind; found on Dendrites, Cell Body, Axon Hillocks |
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Mechanically Gated Channel |
opens in response to physical force |
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Voltage Gated Channel |
open or close in response to changes in membrane Potential; Found along axon |
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Leaky Channels |
ALWAYS OPEN; non gated, found everywhere |
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Membrane Potential |
Resting Potential Graded Potential |
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Resting Membrane Potential |
potential difference across the membrane in a resting state ( -70mV) |
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What is a normal resting potential? |
-70mV |
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Resting Potential |
Chemical Gradient Electrical Gradient |
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Chemical Gradient in resting cell |
Higher concentrations of Na+ outside cell Higher concentration of K+ inside cell |
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Electrical Gradient |
inside of membrane is negatively charged and outside is + charged |
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Factors Contributing to the Resting Membrane Potential |
1. membrane is 50-75x more permeable to K+ so K+ ions leak out faster than Na+ in 2. Intracellular Proteins -fixed anions in cell 3. Sodium potassium pump maintains gradient - 3 Na+ out for 2 K+ in |
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What does a stimulus do to the Resting Membrane Potential (RMP)? |
it disrupts it |
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Graded Potential |
Localized change in membrane potential |
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Describe Graded Potential |
1. Local 2. Short lived, dissipating 3. if excitatory then depolarization of membrane 4. Magnitude of stimulus depends on how many Na+ channels open |
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Neurotransmitters binding to what can stimulate Graded potentials? |
1. Ligand gated channels 2. Mechanical stress, 3. Temperature change |
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Examples of Graded Potentials |
1. Receptor potentials 2. Post synaptic potentials 3. Motor end plate potentials |
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Why does the magnitude of stimuli depends on how many Na+ channels open? |
determines the distance the graded potential travels
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Magnitude of graded potentials and duration depends on what? |
1. Frequency of stimuli (Summation) 2. Amplitude of Stimulus (Strength)`
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Depolarization |
membrane potential becomes less negative; when neurons are stimulated Na+ channels open and Na+ rushes into cell down its electrochemical Gradient |
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Threshold potential |
-55mV; critical level the membrane potential must reach to open voltage gated channels on axon to produce an action potential uce act |
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Can a graded potential initiate a action potential? |
Yes, if the threshold potential is reached at the axon hillock |
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What does the mV number tell us? |
the mV of the inside of the cell |
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Summation of stimulus |
quick firing or release of a stimulus, one right after another |
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Trigger zone for action potential |
Axon HIllock |
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Action Potential |
brief reversal of the membrane potential; moves away from cell down axon WITHOUT diminishing |
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Action potential is a wave of depolarization (lowering of voltage) followed by what? |
repolarization |
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Frequency of Action Potential increases to reflect what? |
Stronger stimuli |
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Repolarization |
membrane returns to its resting membrane potential |
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What 3 things occurs during repolarization? |
1. Voltage gated NA+ channels close 2. Voltage Gated K+ channels open and K+ efflux restores resting membrane potential 3. Membrane Potential becomes more negative as K+ rushes out |
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Hyperpolarization |
inside of membrane becomes more negative than the resting state |
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What is occurring in Hyperpolarization? |
1. Voltage gated K+ channels are sluggish to close 2. K+ permeability lasts longer and membrane potential dips below resting potential |
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Restoring Resting Membrane Potential |
1. Repolarization restores the electrical gradient 2. N/K pump restores ionic concentrations |
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Refractory Period |
amount of time required for a neuron to generate another action potential |
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Absolute Refractory period |
when another AP cannot be generated
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Describe the Absolute refractory Period |
1. occurs from opening of NA+ gates until the resetting of the activation gates 2. Ensures each action potential is separate 3. Enforces the one way transmission of nerve impulses |
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Relative Refractory Period |
interval following the absolute value refractory period; threshold is raised so only extremely strong stimulus can trigger another AP |
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Describe Relative Refractory Period |
1. Sodium gates are reset 2. K+ are still open 3. Hyperpolarization is still occurring |
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Inhibitory Postsynaptic Potential (IPSP) |
binding of neurotransmitters cause a hyperpolarization of membrane therefore moving away from threshold and reducing the ability to initiate action potential |
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What does an IPIPS cause? |
1. K+ or Cl- channels to open 2. K+ rushes out or Cl- rushes in, both causing the inside to become more negative |
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Summation EPSP |
A single ESPS cannot induce an action potential but they can be summed, Axon hillock keeps score of all graded potential received |
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Temporal Summation |
a presynaptic neuron increases the frequency of impulse and more neurotransmitters are quickly released in quick succession |
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Spatial Summation |
Postsynaptic neuron is stimulated by multiple presynaptic neurons at the same time
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IPSP and EPSP can also be summed and do what to each other? |
Cancel each other out |
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Modulator Neuron
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the effectiveness of the PRESYNAPTIC neuron can be affected by another neuron
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What does the Modulator neuron allow for? |
selective inhibiting/ enhancing of a specific presynaptic neuron without affecting the input from other neurons or effecting all targets |
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Presynaptic inhibition |
the amount of neurotransmitter released from neuron A is decreased by neuron B |
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Presynaptic facilitation
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amount of neurotransmitter released form Neuron A is enhanced by Neuron B
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Neurotransmitter Receptors mediate change in potential according to what ? |
1. amount of neurotransmitter released 2. Amount of time neurotransmitter is bound to receptor, until it is deactivated
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4 Factors influencing Conduction Velocity |
1. Myelination of Axon 2. Diameter of Axon 3. Alcohol, Sedatives and anesthetics 4. Insufficient blood flow |
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Myelination of axon |
increase impulse rate by acting as an insulator preventing charge leaking |
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Saltatory Conduction |
voltage gated channels are concentrated at the nodes so electrical impulses jump form node to node instead of having to travel down entire axon |
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Diameter of Axon |
the larger the diameter the quicker the impulse travels, less resistance to current flow so adjacent membranes depolarize quicker |
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Alcohol, Sedatives, and anesthetics |
slow or block nerve impulses by reducing permeability to Na+ |
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Insufficient Blood Flow |
slows impulses, caused by cold or pressure |
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Transmission Across Synapse |
1. Action potential reaches axon terminals 2. Voltage gated Ca2+ channels open, Ca2+ floods terminal 3. Synaptic Vessels fuse with plasma membrane and release neurotransmitters into cleft 4. Neurotransmitters diffuse across cleft and bind to receptors on chemical gated channels initiating a postsynaptic potential |
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Types of postsynaptic Potentials (Graded Potentials) |
1. Excitatory Postsynaptic Potential 2. Inhibitory Postsynaptic Potentials |
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Excitatory Postsynaptic Potentials |
EPSP; binding of neurotransmitter opens Na+ channels and causes depolarization (Membrane potential less negative and closer to threshold and firing action potential)
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Neurotransmitter effects on Postsynaptic Potentials |
Binding can cause graded potential
(depending on how neurotransmitters affect the membrane determines if excitatory or inhibitory)
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Mechanisms for Deactivating Neurotransmitters |
1. Inactivated by enzymes 2. Reuptake by presynaptic terminal 3. Diffuse away from synapse |
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Acetylcholine Inactivated by Enzyme |
degraded by enzyme acetylcholinesterase found in synaptic cleft
ACH-->Acetate + Choline
Choline is actively transported back into the presynaptic terminal and recycled
Choline + Acetyl CoA--> Ach |
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Norepinephrine, Dopamine, Serotonin -Reuptake by presynaptic axon terminals or astrocytes
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1. Catechol-O methytransferase (COMT) is used by liver and kidney cells to break down the NE and E in circulation
2. Some diffuses into blood; rest taken back up into presynaptic neuron 3. Repackaged or broken down by monoamine oxidase (MAO) in terminal |
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Classification of Neurotransmitters by
CHEMICAL STRUCTURE (5) |
1. Acetylcholine (ACH)
2. Biogenesis amines 3. Amino Acids 4. Peptides 5. Messenger |
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Classification of Neurotransmitters by Function (3) |
1. Excitatory Transmitters 2. Inhibitory Transmitters 3. combination of both |
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Examples of Acetylcholine Neurotransmitters |
ACh |
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Examples of Biogenesis amines |
catecholamine's Serotonin
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Example of Excitatory Neurotransmitters |
Glutamate |
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Example of Inhibitory Neurotransmitters |
GABA Glycine
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Combination of Excitatory and Inhibitory Neurotransmitters |
Acetylcholine |
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What determines whether a combination Neurotransmitter excites or inhibits? |
receptor type that it binds to on postsynaptic neuron |
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Acetylcholine Mechanism of action |
Excitatory at Neuromuscular Junction with skeletal muscle (Nicotinic Receptor)
Inhibitory at Cardiac Muscle Muscarinic Receptor)
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Classification of Neurotransmitters by RECEPTOR MECHANISM |
Direct Indirect |
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Direct Receptor |
Neurotransmitter that opens ion channels; Promotes rapid responses "fast Synapses"
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Examples of Direct Neurotransmitters |
ACh Amino Acid |
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Indirect Receptors |
Neurotransmitters that act through second messengers; promotes long- lasting effects through "slow synapses" |
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Examples of Indirect Neurotransmitters |
Biogenic amines Peptides Dissolved gases
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4 Types of Circuits in Neuronal Pool |
1. Divergent 2. Convergent 3. Reverberating 4. Parallel after discharge |
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Divergent Circuit
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one incoming fiber stimulates ever increasing number of fibers, often amplifying circuits (balance and posture)
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Convergent Circuit
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opposite of divergent resulting in strong stimulation or inhibition (process sensory information)
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Reverberating Circuit
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Chain of neurons containing collateral synapses with previous neuron in the chain (short term memory)
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Parallel after discharge Circuit
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incoming neurons stimulate several neurons in parallel arrays (plexus)
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Postsynaptic inhibition
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inhibitory neuron modulates the signal, ALL TARGETS will be inhibited equally
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PRESYNAPTIC INHIBITION
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modulator neuron synapses on 1 neuron, SELECTIVELY Inhibits 1 Target
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MAO inhibitors
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inhibit breakdown of NE and E to keep them in synaptic cleft longer, used as antidepressants; specific neurotransmitters MAOIs with less side effect
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Voltage Gated Sodium Gates
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Activation gate closed at resting
Inactivation Gate Open at resting 1. action potential 2. Na+ Activation gate open- depolarization occurs, K+activation gate closed 3. Inactive gate closes at repolarization, K+ gate opens 4. Both reset |
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Depolarization K+ gate open or closed?
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closed
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Repolarization K+ gate opened or closed?
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Open
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