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29 Cards in this Set
- Front
- Back
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Electrical vs. Chemical synapse
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Eletrical is uncommon
Composed of gap jxns Found in cardiac and visceral smooth muscle Few neurons in NS contain electrical synapses |
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Presynaptic membrane
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Message is unidirectional
Contains small vesicles of neurotransmitters Contains unusually large # of Ca+ voltage gated channels |
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Role of calcium in spreading action potential
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Once action potential is received, Ca+ channels are activated and Ca flows into the cell.
The sudden influx of Ca causes some vesicles of neurotransmitters to be released by exocytosis into the synaptic cleft |
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Movement of neurotransmitters in synaptic cleft
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Brownian motion- random motion of molecules
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Postsynaptic membrane receptorr...
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for neurotransmitters. Once attached to receptor, the postsynaptic membrane becomes more permeable to ions, which move across the membrane through proteins called ionophores. This completes the transfer of the neural impulse
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Cause of fatigue in neural cells
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If cells are fired too often and it is not able to replenish its supply of neurotransmitter vesicles
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How a cells detaches the neurotransmitter....
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has to be done the postsynaptic cell is not stimulated repeatably
1. neurotransmitter destroyed by enzyme in matrix of cleft, with its parts being recycled by presynaptic cell 2. absorbed by presynaptic cell via active transport 3. may diffuse out of the synaptic cleft |
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Important tid bits about neuortransmitters(nt)/ synapeses/ neurons
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1. Certain nt are found and used in different areas of the nervous system
2. A single synapse usually only releases one type of neurotransmitter 3. A single synapse cannot change from inhibitory to excitatory or vice versa 4. However, some nt can cause inhibition or exciting based on type o receptor in postsynaptic membrane (Ach) 5. normally 40-80 synapses must fire to simultaneously to create action potential within neuron 6. Synapses can be b/w dendrites, cell bodies, or other axons or synapses |
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Acetylcholine
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Common nt. that has inhibitory and excitatory effect
Inhibit-heart Excites- visceral smooth muscle in intestines |
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Receptors in neurotransmission....
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may be ion channels themselves once nt is attached, or may act via 2nd messenger system
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Second messenger system of nervous system
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Preferred for prolonged change, such as memory
G-protein typically initiates 2nd messenger system which is attached to the receptor protein along the postsynaptic membrane |
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G-protein Alpha-subunit
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breaks free from the G-protein on the receptor after nt binds to it on postsynaptic membrane. May activate:
1. separate ion channels 2. another 2nd messenger system (cAMP or cGMP) 3. intracellular enzymes 4. gene transcription |
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Nervous system support cells
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"glial cells/ neuroglia"
-microglia -ependymal cells -satellite cells -astrocytes -oligodendrocytes -schwann cells |
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Microglia
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arise from white blood cells; monocytes
phagocytize microbes and cellular debris |
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Ependymal cells
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epithelial cells that line the space containing cerebrospinal fluid
Use cilia to circulate the fluid |
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Satellite cells
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support ganglia which are groups of cell bodies in PNS
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Astrocytes
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star-shaped neuroglia in that give physical support in CNS by attaching to neurons and blood vessels, as well as mineral and nutrient balance
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Oligodendrocytes
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create insulating myelin around axons in CNS
only vertebrates have myelinated axons |
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Schwann cells
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Create myelin sheath in PNS
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Myelin
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Myelin increases the rate at which the axon can transmit the signal
creates what is called as "white matter" while non-sheathed cell bodies called "gray matter" creates nodes of Ranvier--> saltatory conduction |
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Nervous system support cells
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"glial cells/ neuroglia"
-microglia -ependymal cells -satellite cells -astrocytes -oligodendrocytes -schwann cells |
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Microglia
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arise from white blood cells; monocytes
phagocytize microbes and cellular debris |
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Ependymal cells
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epithelial cells that line the space containing cerebrospinal fluid
Use cilia to circulate the fluid |
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Satellite cells
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support ganglia which are groups of cell bodies in PNS
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Astrocytes
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star-shaped neuroglia in that give physical support in CNS by attaching to neurons and blood vessels, as well as mineral and nutrient balance
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Oligodendrocytes
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create insulating myelin around axons in CNS
only vertebrates have myelinated axons |
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Schwann cells
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Create myelin sheath in PNS
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Myelin
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Myelin increases the rate at which the axon can transmit the signal
creates what is called as "white matter" while non-sheathed cell bodies called "gray matter" creates nodes of Ranvier--> saltatory conduction |
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Acetylcholine
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nt of parasympathetic nervous system that opens the less sensitive potassium channels which inhibits depolarization. This ultimately lengths the time /w heartbeats
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