Term
| The 2 main cell types of the Peripheral Nervous System are... |
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Definition
| Neurons & Neuroglial cells (support cells): |
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Term
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Definition
| transmit electrical signals, found in grey matter of CNS and ganglia. |
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Term
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Definition
| nonexcitable, surround and wrap neurons |
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Term
| 6 Main Characteristics of Neurons |
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Definition
1. Conduct electrical impulses along the plasma membrane
2. Produce nerve impulse
3. Produce action potential
4. Longevity: can live and function for a lifetime
5. Do not divide: fetal neurons lose their ability to undergo mitosis
6. High metabolic rate: require abundant oxygen and glucose |
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Term
Cell Body is also known as..
Give Characteristics also |
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Definition
Perikaryon
Size varies from 5–140µm
Has the normal cell organelles
*Nissl bodies (rER),
Neurofibrils and Lipofuscin |
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Term
Axon-
Give 3 Characteristics |
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Definition
1. LONG
2. Transmits impulses away from
Neuron. |
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Term
Initital Segment of Axon
Give 5 Characteristics |
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Definition
1. after Axon hillock
2. most excitable site
3. origination
site of action potential
4. Neurofilaments, microtubules and
actin microfilaments are present.
5. Is smooth, without many synapses |
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Term
Dendrite
Give Characteristics |
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Definition
1. Increases neuron’s receptive area.
2. Transmits impulses towards the
Neuron.
3. Nissl bodies in its basal parts |
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Term
| List the 2 roles of Supporting Cells |
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Definition
1.Provide supportive functions for neurons.
2. Cover nonsynaptic regions of the neurons. |
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Term
| The 2 types of Supporting Cells are |
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Definition
1. Schwann cells
2. Satellite Cells (aka ganglionic gliocytes) |
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Term
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Definition
| which form myelin sheaths around peripheral axons |
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Term
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Definition
| which support and surround neuron cells bodies within the ganglia of the PNS. |
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Term
| The 4 main cell types of the Central Nervous System are... |
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Definition
1. Oligodendrocytes
2. Microglia
3. astrocytes
4.Ependymal cells |
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Term
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Definition
| which form myelin sheaths around axons of the CNS |
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Term
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Definition
| which migrate through the CNS and phagocytose foreign and degenerated material. |
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Term
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Definition
| which help to regulate external environment of neurons in the CNS |
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Term
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Definition
| which line the ventricles of the brain and the central canal of the spinal cord. |
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Term
Oligodendrocytes
Give 4 Characteristics |
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Definition
1. small cell bodies
2. no filaments in their
cytoplasm
3. one oligodendrocyte can
myelinate many fibers.
4. not surrounded
by a basement membrane |
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Term
| List the two functions of Oligodendrocytes |
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Definition
1. Myelination in the CNS
2. Satellite Oligodendrocytes may influence
the biochemical environment of neurons. |
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Term
| 3 Characteristics of Microglia |
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Definition
1. Smallest among neuroglial cells.
2. Migrate into the nervous system in fetal life.
3. They are scattered in the CNS. |
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Term
| Functions of the Microglia |
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Definition
-In the normal CNS, they are inactive
(resting microglia)
-in inflammation or degeneration of CNS, they proliferate and become active and phagocytic |
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Term
| Describe the Structure of Ependyma |
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Definition
-form a single layer of cuboidal cells lining the central cavities of the brain and spinal cord.
- They have microvilli also |
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Term
Describe the Structure of Astrocytes
(2) |
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Definition
1. small cell body
2. numerous branching processes |
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Term
| Describe the structure of the astrocytic processes |
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Definition
| THey are interwoven at innner and outer surfaces of CNS, forming outer and inner glial limiting membranes |
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Term
| List 4 Functions of An Astrocyte |
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Definition
1. They form a supportive framework for neurons, and in embryo they serve as ascaffolding for migration of immature neurons.
2. they cover the synaptic contacts between neurons and thus insulate axon terminals from influencing neighboring unrelated neurons.
3. They absorb glutamate (transformed into glutamine) and GABA secreted by the nerve terminals, thus limiting the influence of these neurotransmitters.
4. They absorb excess K+ of extracellular fluid. Since K+ diffuses out of neurons during the production of nerve impulses, for maintaining the proper ionic environment for neurons. |
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Term
| List 5 more Functions of an Astrocyte |
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Definition
1.By feet surrounding blood capillaries take up glucose from the blood, the glucose metabolized into lactic acid, is then released and use as an energy source by neurons.
2. Phagocytosis of degenerated axon terminals.
3. replacement gliosis: when neurons die due to disease or injury, they proliferate and fill the spaces previously occupied by neurons
4. 8-Astrocytes induce the formation of the blood-brain barrier
5. produce trophic substances for neurons |
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Term
| What is Gliosis and Glial Scar? |
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Definition
| -hyperplasia and hypertrophy of astrocytes that occur in reaction to CNS injury |
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Term
| How do Oligodendrocytes respond to Gliosis and Glial Scar? |
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Definition
| -they expand and vacuolate their cytoplasm |
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Term
| Name 2 Tumors of Astrocytes |
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Definition
| Astrocytomas and Glioblastomas |
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Term
| What is the difference between Gliomas and Ependymomas |
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Definition
| - Gliomas are very invasive and grow large with miimal effect on neighboring neurons |
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Term
| What is Multiple Sclerosis? |
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Definition
| An unknown disease, occurs between ages of 20-40 years old, demylenation in CNS, usually starts with optic nerve, spinal cord, and cerebellum. Axonal degeneration as a result of demyelination is part of the disability. |
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Term
1. The Myelin Sheath of the CNS are formed by___
2. This process occurs mostly___ |
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Definition
1. oligodendrocytes
2. postnatally |
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Term
| 1. The Myelin Sheath of the PNS are formed by___ |
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Definition
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Term
| What is one major difference between Schwann Cells and oligodendrocytes? |
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Definition
| Unlike a Schwann cell, which forms a myelin sheath around only one axon, each oligodendrocyte has extensions, form myelin sheaths around several axons. |
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Term
| 1. The myelin sheaths around axons of the CNS give this tissue a ____ Color. |
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Definition
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Term
| The gray matter of the CNS is composed of high concentrations of |
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Definition
| cell bodies and dendrites, which lack myelin sheaths. |
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Term
| When an axon in peripheral nerve is cut, the distal portion of the axon that was severed from the cell body degenerates and is phagocytosed by____ |
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Definition
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Term
| After a Cut portion of an axon (in PNS)is cut and phagocytosed by a Schwann Cell, the Schwann cell then forms a _____ |
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Definition
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Term
| What are two Factors that contribute to guidance of the Regenerated Axon to its proper destination? (In PNS) |
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Definition
| The SC secrete chemicals that attract the growing axon tip, and the regeneration tube |
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Term
| Why is Regeneration in the CNS very limited? |
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Definition
| due in part to the absence of a continuous neurilemma which inhibit molecules produced by oligodendrocytes and astrocytes in the injured CNS. |
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Term
| What are the 4 Neurotrophins in a developing fetal brain that promote neuron growth? |
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Definition
1. Nerve growth factor (NGF) 2.
Brain-derived neurotrophic factor (BDNF)
3. Glial-derived neurotrophic factor (GDNF)
4. Neurotrophin-3(it is important in the embryonic development of sensory neurons and sympathetic ganglia.) |
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Term
| What is the Blood Brain Barrier? |
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Definition
| The barrier between cerebral capillary blood and the CSF |
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Term
|
Definition
| the ventricles and the subarachnoid space. |
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Term
| What does the BBB Consist of? |
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Definition
| of the endothelial cells of the cerebral capillaries and the choroid plexus epithelium |
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Term
| What Lipid-soluble substances freely cross the blood-brain barrier (along with water) and equilibrate between blood and CSF. |
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Definition
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Term
| ____ and ____ are excluded from the CSF because of their large molecular size. |
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Definition
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Term
| The composition of CSF is approximately the same as that of ______ of the brain, but differs significantly from ____. |
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Definition
1. interstitial fluid
2. blood |
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Term
| List 3 Function of the BBB |
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Definition
1. maintains a constant environment for neurons in the CNS and protects the brain from endogenous or exogenous toxins.
2. prevents the escape of neurotransmitters from their functional sites in the CNS into the general circulation.
3. Drugs penetrate the blood-brain barrier to varying degrees. For example, nonionized (lipid-soluble) drugs cross more readily than ionized (water-soluble) drugs |
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Term
| Name three instances that destroy the blood-brain barrier and permit entry into the brain of substances that are usually excluded |
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Definition
| inflammation, irradiation, and tumors |
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Term
1. What is the precursor to dopamine that can cross the BBB
2. What is a disease in which dopamine does not cross the BBB |
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Definition
1. L-DOPA
2. Parkinson's Disease |
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Term
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Definition
| NA+, CL-, HCo3-, Osmolarity |
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Term
|
Definition
K+
Ca2+
Glucose
Cholestrol*
Protein* |
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Term
|
Definition
|
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Term
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Definition
-the sites where two neurons come into close proximity.
-The term also implies to the nerve-muscle contact as well. |
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Term
| What are the three forms of synapses? |
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Definition
Axodendritic, axosomatic and axoaxonic
(Most common are the first two) |
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Term
| Axons can have a terminal expansion or a series of expansions called ______ which make several contacts as they pass through a ______. |
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Definition
1. bouton de passage
2. dendritic tree |
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Term
| The 2 types of Synapses are |
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Definition
1. Chemical (Most Common)
2. Electrical |
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Term
| Chemical Synapses involve |
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Definition
|
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Term
|
Definition
| are released from a pre-synaptic neuron that becomes attached to a protein (receptor) at post-synaptic membrane. |
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Term
| Are Chemical Synapses unidirectional? |
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Definition
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Term
| Presynaptic cytoplasm contains |
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Definition
| vesicles, mitochondria and lysosomes among others. |
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Term
On postsynaptic side, the cytoplasm
contains |
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Definition
|
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Term
|
Definition
|
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Term
| What are the 9 neurotransmitters? |
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Definition
Acetylcholine (Ach), norepinephrine, epinephrine, dopamine,
glycine, serotonin, gamma-aminobutyric acid (GABA), enkephalines, substance P
and glutamic acid. |
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Term
Where is Ach Found? (Acetylcholine)
(3 locations) |
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Definition
1. neuromuscular junction,
2. autonomic ganglia
3. parasympathetic nerve |
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Term
Where is Norepinephrine found?
(2 locations) |
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Definition
1. sympathetic nerve endings
2. in CNS: hypothalamus |
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Term
Where is Dopamine found?
(2 locations) |
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Definition
1. found in high concentrations in basal ganglia
2. hypothalamus |
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Term
Where is Glycine found?
(1) |
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Definition
| principally in synapses in the spinal cord |
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Term
Where is Glutamatic acid found?
(1) |
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Definition
| in many central nervous neurons |
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Term
Neurotransmitters are released from the _____ after the nerve being
stimulated (arrival of action potential). This results in an influx of _______ into the presynaptic part which causes the synaptic vesicles to fuse with the ______. |
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Definition
1. nerve endings
2. Ca+ ions
3. presynaptic membrane |
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Term
| When neurotransmitters are released into the synaptic cleft, what happens to the postsynaptic membrane? |
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Definition
| the resting potential is either increased or decreased |
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Term
| When a receptor on postsynaptic membrane binds to the neurotransmitter and opens the ion channels, what else is generated? |
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Definition
| an excitatory postsynaptic potential (EPSP) (ex: Ach in nicotinic receptors) or inhibitory postsynaptic potential (IPSP) (ex: GABA) |
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Term
| What is the fate of a neurotransmitter? |
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Definition
| Neurotransmitters effect for a short time since they are either destructed in the cleft or reabsorbed by the presynaptic part |
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Term
| What are the 5 Characteristics of a Neurotransmitters? |
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Definition
1- presence of the substance within neuron terminals
2- release of the substance with neuronal stimulation
3- application of the exogenous substance to the postsynaptic membrane produces the effects of stimulation of the presynaptic neuron.
4- the concentration –response curve of the substance applied to the postsynaptic membrane is affected by drugs in a similar way as normal postsynaptic response.
5- a local mechanism exists for inactivation of the substance (e.g.: enzymatic degradation, uptake into nerve terminal or glia). |
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Term
| What type of junctions are electrical synapses? |
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Definition
|
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Term
| Gap Junctions are formed by specialized channels called ____. Each one consists of 6 parts called ____. |
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Definition
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