Exam 3: Chapter 12 Nervous Tissue Flashcards
(180 cards)
1
Q
The nervous system detects _______ changes.
A
environmental changes
2
Q
These environmental chanegs impact the body and works in tandem with what other system?
A
endocrine
3
Q
What is hte nervous system responsible for?
A
-responsible for all our behaviors, memories, and movement
4
Q
How does the nervous system accomplish everything it is responsible for?
A
able to accomplish this because of the excitable characteristics of nervous tissue which allow for the generation of nerve impulses
5
Q
What are the two divisions of the nervous system?
A
central nervous system and the peripheral nervous system
6
Q
What are the three fundamnetal steps of the nervous tissue?
A
sensory, interpretation, motor response occurs
7
Q
what is happening in the sensory step?
A
detecting internal and external stimuli
8
Q
What are the two functional divisions of the nervous system?
A
sensory (afferent) divisions and motor (efferent) division
9
Q
Which fibers are used in the afferent division?
A
somativ afferent fibers and visceral afferent fibers
10
Q
What does the somatic afferent fibers function to do?
A
convey impulses from skin, skeletal musces, and joints
11
Q
What do the visceral afferent fibers to do?
A
convey impulses from visceral organs
12
Q
What does the motor (efferent) division function do?
A
transmits impulses from the CNS to the effector organs
13
Q
What are the two motor systems within the peripheral nervous system?
A
somatic (voluntary) motor system and the autonomic (involuntary) motor system (ANS)
14
Q
What is the function of the voluntary motor system?
A
conscious control of skeletal muscles
15
Q
What is the function of the autonomic (involuntary) motor system>
A
control visceral motor nerve fibers regulate smooth muscle, cardiac muscle, and glands
16
Q
What are the two functional subdivisions of the autonomic motor system?
A
sympathetic and parasympathetic
17
Q
What are neurons?
A
functional units of the nervous system, fomring complex processing networks within the brain and spinal cord that bring all regions of the body under the CNS control
18
Q
Neuroglia are?
A
smaller than neurons, however, they greatly outnumber nuerons. They act to support and maintains the neuronal networks
19
Q
What are the special characteristics of neurons?
A
long-lived cells
amitotic
high metabolic rate
plasma membrane functions in electrical signaling and cell to cell interactions during development
20
Q
What does amitotic mean?
A
cannot divide
21
Q
What does the high metabolic rate depend on?
A
depends on continuus supply of oxygen and glucose
22
Q
What does the plamsa membrane function in doing for neurons?
A
electrical signaling and cell to cell interactions during developments
23
Q
Most neurons contain…
A
dnedrites
cell body
axon
axon terminals
24
Q
there are several types of neurons, what are some of the differences?
A
some lack dendrites
some lack axons
synapses that connect an axon to another axon or a dendrite to another dendrite
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What do dendrites look like?
short, tapering, and diffused branches
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Dendrites are what part of the of the neruon/
receptive, input region of the nueruon
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What do the dendrites do?
convey electrical signals toward the cell body as graded potentials
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The cell body is the ________ center of a neuron
biosynthetic
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What does the cell body look like?
- a spherical nucleus with nucleolus
- well-developed Golgi -apparatus
- Rough ER
- contains the axon hillock
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What is the Rough ER of a neuron called?
Nissil bodies
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What is the axon hillock?
cone-shaped area from whcih axon arises
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Axons conduct impulses _____ from the cell body toward another _____ or _____ _____?
away, toward, neuron or effectory cell
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What is the initial segment?
beginning of the axon
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What is the trigger zone?
junction between the axon hillock and the initial segment
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Axons contain numerous _____ ______.
terminal branches
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What are the terminal branches known as?
telodendria
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axons contain knoblike ___ ________
axon terminals
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axon terminals are the?
secretory region of the neuron that releases neurotransmitters to excite or inhibit other cells
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what are the spaces in between Schwann cells?
nodes of Ranvier
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What are the types of axon movement?
slow axon transport, and fast axon transport
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Slow axonal transport functions in
- supplying new axoplasm to developing or regenerating axons
| - replenishes axoplasm in growing and mature axons
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Fast axonal transport has two types of axonal transport, what are they?
anterograde (forward) and retrograde (backward)
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Anterograde (forward) transport is what
the direction that moves organelles and synaptic vesicles from the cell body to the axon terminal
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Retrograde (backward) transport is
the direction that moves membrane vesicsles and other cellular materials from the axon terminals to the cell body to be degraded or recycled
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What are the 3 types of fucntional classifications of neurons
sensory (afferent)
- interneurons (association neruons)
- motor neurons (efferent)
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What are sensory (afferent) neurons function?
transmits impulses from sensroy receptors Toward the CNS
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What are the functions of internuerons (association neurons)?
shuttle signals through CNS pathways
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Internuerons are most entirely within what division of the nervous system?
CNS
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Moro neurons (efferent) carry...
impulses from CNS to efferent cells and organs
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What are neuroglia?
support cells that dont generate or conduct nerve impulses
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how do neuroglia support neurons?
forming the blood brain barrier (BBB)
- forms myelin sheaths (nerve insulation) around neuronal axons
- making cerebral spinal fluid that circulates around the brain and spinal cord
- participates in phagocytosis
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What are teh different types of neuroglia cells?
astrocytes, microglia, satellite, Schwann cells,
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what are astrocytes?
most abundant and maintian chemical environement
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microglia function to
migrate to injured tissue and phagocytize
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satellite cells function to
maintian the chemical envirnement in the CNS
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Schwann cells are
vital to regeneration of damaged PNS nerve fibers
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What is myelination?
process of forming myelin sheath which insulates and increases nerve impulse speed
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Myelin sheaths are a ______-_____ sheath
protein-lipid
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Myelin sheaths are large in ______
diameter
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In the CNS, what are the myelin sheaths made by?
oligodendrocytes
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in the PNS, what cells form the myelin sheaths?
Schwann cells
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Myelin sheaths in the PNS are made by...
schwann cells wraping many times around the axon
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the myelin sheath is _____ layers of the schwann cell _______
concentric, membrane
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Neruolemma is the
peripheral bulge of schwann cell cytoplasm
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What is the process for Schwann cells forming the myelin sheath
1. schwann cell envelops an axon
2. schwann cell rotate aroudn axon wrapping its plasma membrane loosely around in its successive layers
3. schwann cell cytoplasm is forced from between membranes. The tiht memrbane wrappings surrounding the axon from the myelin sheath
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What are the nodes of ranvier?
Gaps in the myelin sheath
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For every schwann cell that wraps around a portion of the axon, there are _____ nodes of ranvier formed
Two
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When does myelin increase?
Increases from birth to maturity
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What is multiple sclerosis?
Destruction of myelin sheaths
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Why is an infnats response to stimuli niether rapid or as corrdinated as an adult?
Because mylein sheaths are still forming
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Thin nerve fibers are_____
Unmyelinated
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One ______ ______ may ___________ enclose ____ or more unmyelinated axons
Schwann cell, incompletely, 15
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How are the myelin sheaths formed in the CNS?
Fomred by processes of oligodendroytes, not the whole cells
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In the myelin sheaths of the CNS what are still present?
Nodes of ranvier
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What is not present in the myelin sheaths of the CNS?
Neurolemma
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The thinnest fibers are __________.
unmyelinated
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What is gray matter?
Mostly neruon cell bodies with unmyeoinated fibers and houses the densdrite portions of neurons
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What is white matter?
Dense collections of myelinated axons from many neuorns
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Cell body clusters are called what in the CNS and what in the PNS?
CNS-> nuclie
PNS -> ganglia
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Axons and dendrite bundles are called what in the CNS and what in the PNS?
Tracts in the CNS an
Nerves in the PNS
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The cell bodies lose their mitotic function at?
Birth
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The cell bodies can only be repaired through ________ after injury
Regneration
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The regeneration of neurons depends largely upon …?
The Schwann cells in the PNS
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Regeneration essentially doesn’t happen at all in the?
| Why does this occur?
CNS;
| Becuaes the astrocytes form scar tissue when they neurons are injured
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When an axon is injured, the _________ aids in the regeneration
Neuronlemma
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How does the neurolemma assist in the regneration of the axon?
By formaing a regeneration tube that guides and stimulates regrowth of the axon
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What is demyelination?
Loss/destrution of sheaths
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What causes demyelination?
May result from disease, radiation, chemotherapy
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What can be a result of demyelination?
May cause nerve deteriation
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What is the neruolemma?
Outermost layer of nerve fibers in the PNS
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How is the neurolemma different from the axon or myelin sheath?
It doesn’t degenerate after a nerve has been cut or crushed.
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The neurolemma forms what in the nerve regeneration process?
The regenration tube
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In the CNS, axons are myleinated by __________ which is why they lack _________.
Oligodendrocytes, neurolemma
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Wrapping of Schwann cells allows for …?
More readily conducting impulses
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Like muscle fibers, nerve fibers are ________ _________.
Electrically excitable
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What are the two types of electrical signals used for communication?
Graded potentials and action potentials
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Graded potentials are?
Used for short distance communication ONLY
Has varying degrees of impusle
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Action potentials allows for?
Communication over long distances within the body
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The impulse of action potentials are always...?
The same regardless of impulse
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In the neurons, the RMP is about _____
-70mV
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How is the resting membrane potential generated?
Differences in ionic makeup of intercellular fluid and extracellular fluid
Differential permeability of the plasma membrane
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The differences in the ionic make up of ICE and ECF is referring to..?
ICF having a lower concentration of Na+ and Cl- than ECF
ICF having higher concentation of K+
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The differential in permeability of the plasma membrane refers to?
Membrane Freely permeable to Cl-
Large negatively charged proteins (A-) that always remain in the cytosol
Leakage channels favor a gradient where more K+ leaks out than Na+ leaks in
The memrbane is 75x more permeable to K+
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What are the types of membrane channels?
Passive (leak) channels
Active (gated) channels
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Passive channels are always_____
Open
106
Active channels may be...
Closed but are capable of opening
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For active channels, open means ________ and closed means _______ and is incapable of ______.
Activated, inactive, opening
108
What are some examples of membrane channels?
Chemical gated,
Voltage gated
Mechanical gated
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When do graded potentials occur?
When a stimulus causes gated ion channels to open
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What is this graded potential also known as?
Receptor potentials, generator potential, postsynaptic potential
111
The magnitude of graded potentials are...?
Variable with stimulus strength
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When does the magnitude decrease?
Magnitude will decrease with distance as ions flow and diffuse through leakage channels
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Graded potentials travel only
Short distances
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When the cell is having a depolarizing graded potential occur the
Cell becomes more positive
115
Hyperpolarized graded potentials are when the cell becomes
More negative
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Graded potentials can ______ or ______ each other out
Summate or cancel
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Wehre do graded potentials occur?
In dendrites and cell bodies
Don’t travel to axons
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What are action potentials (AP)?
t
Signal which travels the length of the neuron
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The action potential is where the membrane potential...?
Reverses and then eventually is restored to its resting state
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What is the amplitude of the action potential?
About –100 mV
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If a neuron receives a threshold stimuuls, this means?
A full strength nerve impulse is produced
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When the neruon recevies a threshold stimulus and the full strength nerve impulse is produced it will...?
Spread down the axon of the neuron to the axon terminals
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If a stimulus is not strong enough (subthreshold), no nerve impulse will resul
duh
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WHAT HAPPENS DURING AN ACTION POTENTIAL?
1. Sodium ions arrive at the axon hillock
2. Threshold voltage is reached
3. Voltage-regulated Na+ (fast) gates open and slow voltage gated K+ gates open
4. Propogation of signal (sending down neuron)
5. Na+ gated close (inactive) above 0mV
6. K+ gates are finally fully open
7. K+ gates close more slowly than Na+ gates
125
What is causing the action potential?
Permiablility changes in the plasma membrane
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All action potentials are _____ and are _______ of stimulus ________.
Alike, independent, intensity
127
What is a strong stimuli?
Generate AP more often than weaker stimuli but it will not cause a larger impulse
128
CNS determines stimulus intensity by...
The frequency of impulses
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What is the absolute refractory period?
STUDY THE IMAGE ON NOTES
- The time when a cell cnt generate an AP no matter the stimulus. This is the time where opening of Na+ channels to resetting.
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What does the relative refractory period ensure?
That an AP is all or nothing and enforces one-way transmission or nerve impulses
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The relative refractory period follows the?
Absolute refactory period
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What may generate another AP after the refractory period?
An exceptionally strong stimulus
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What is happening in the relative refractory period?
The membrane can respond only to a larger-than-normal stimulus
134
At the relative refractory period, what is happeining to the cell?
Na+ channels have returned to their resting state
SOme K+ channels are still open
Repolarization is occuring
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Threshold for AP generation is _________.
Elevated because of hyperpolarization
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Conduction velocities of neurons vary _____.
Widely
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What are the things that affect conduction velocity?
Axon diameter, effect of myelin
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What is the effect of axon diameter?
Larger diameter fibers have less resistance to local current flow and have faster impulse
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What is the effect of myelin on conduction velocity
Continous conduction in unmyelinated axons is slower than saltatory conduction in myelinated axons
Myelin sheath prevents leakage ions
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What is the differece of conduction velocity with myelination?
Saltatory conduction
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What happens in saltatory conduction?
About 30x faster
Voltage gated Na+ channels are located at nodes
APs appear to "jump" from node to node
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What are the classification of fibers?
Group A, B, and C
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What are group A fibers?
Large diameter fibers
Fast fibers (120m/s or 268mph)
Myelinated somatic sensory and motor fibers
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What are group B fibers?
Intermediate diameter
Medium speed (18m/sec; 40 mph)
Lightly myelinated visceral sensory and ANS fibers
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What are group C fibers?
Smallest diameter
Slowest (1m/sec, 2mph)
Unmyelinated sensroy ANS motor fibers
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The presynaptic neuron converts ______ ______ into ______ ________.
Electrical signal (nerve impulse), chemical signal (released neurotransmitter)
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Post syaptic neuron reeives the _________ _______ and generates an _______ _________.
Chemical signal, electrical signal
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The time needed for these processes at a chemical synpase produces a _________ _______ of about ______.
Synaptic delay; 0.5msec
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The synaptic delay is known as the?
Rate limiting step of neural transmission
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Within a few msec, the neurotransmitter is ______.
Terminated
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What are the types of termination done to a neurotransmitters?
Degradation, reuptake, diffusion
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Degradation is done by?
Enzymes
153
Reuptake is done by?
Astrocytes or axon terminal
154
Diffusion is done at?
Away from the synaptic cleft
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Postsynaptic potential Strength is determined by...?
Amount of neurotransmitter released
Time the neurotransmitter is released in the area
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What are the types of postsynaptic potentials?
EPSPs and IPSPs
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What are EPSPs?
Excitatory postsynaptic potentials
Local depolarization of postsynaptic membrane that brings the neuron closer to AP threshold
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What do EPSPs allow for?
Neurotransmitter binding opens ligand channels allowing outflow of K+ and influx of Na+
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What are IPSP?
Inhibitory postsynaptic potentials
This is local hyperpolarization of postsynaptic membrane and arises the neruon away from AP threshold
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What does IPSPs do?
Neurotransmitter binding opens K+ and Cl- channels which allows for K+ outflow and Cl- inlux
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A single EPSP cannot...?
Induce an action potential
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Howeer, EPSPs can ________ to reach ________.
Summate, threshold
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IPSPs can also _______ with EPSPs _______ ____ each other
Summate, cancel out
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What are the types of summation?
Temporal summation and spatial summation
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What is temporal summation?
One or more presynaptic neruons transmit impulses in rapid fire order
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What is spatial summation?
Postsynaptic neuron is stimulated by a large number of terminals at the same time
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Most neurons make _____ or more neurotransmitters.
Two
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Neurotransmitters are released at different ________ ______.
Stimulation frequencies
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____ or _____ neurotransmitters have been identified.
50 or more
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Neurotransmitters are classified by ______ ________ and by _______.
Chemical structure and by function
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Neurotransmitters may be ________ or ________ depending on ________ on the postsynaptic neuron.
Excitatory or inhibitory, receptor
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Neurotransmitter effects can be modified many ways by?
Synthesis can be stimulated or inhibited
Release can be blocked or enhaned
Removal can be stimulated or blocked
Receptor site can be blocked or activated
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What is the agonist?
Chemical that enhances or stimulates the effects at. A given receptor
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What is the antagonist?
Chemical that blocks or dimisnihes the effects at a given receptor
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What are the two types of actions of neurotransmitters?
Direct and indirect
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What does direct action of neurotransmitters do?
The neurotransmitter binds to channel linked receptor and opens channels
Promotes rapid responses
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What does indirect action neurotransmitters do?
Neurotransmitters binds to a G-protein linked receptor
Promotes long lasting effects
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Neurons porcess information when changes occur at the _______ _____ through _______ and ______ _______ of _____ and _____.
Trigger zone through spatial and temporal summation IPSPs and EPSPs
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Integration is the...?
Process accomplished by the post-synaptic neuron when it combines all excitiatory and inhibitory inputs and responds accoridingly
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These integration processes occurs over and over as interneurons are activated..?
In higher parts of the brain
