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Chapter 8: Synaptic Transmission and Neural Integration
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42
Physiology
Undergraduate 2
10/16/2013

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Term
What are the two types of synapses?
Definition
Electrical
Chemical
Term
Electrical Synapse
Definition
Operate by allowing electric signals to be transmitted from one neuron to another through gap junctions
Term
Chemical Synapse
Definition
Operate through the release of a neurotransmitter that activate signal mechanisms in the target cell
Term
What is the most common type of synapse?
Definition
Chemical
Term
Synaptic Cleft
Definition
The space between the presynaptic and postsynaptic neurons
Term
Synaptic Vesicles
Definition
Located on the axon terminal

Store neurotransmitter molecules
Term
What is the process by which two neurons communicate via a chemical synapse?
Definition
1. Action potential causes calcium channels to open.
2. Calcium flows down its electrochemical gradient into the axon terminal
3. Calcium causes membranes of synaptic vesicles to fuse with vesicle attachment sites on the inner surface of the axon terminal and undergo exocytosis which releases the neurotransmitters into the synaptic cleft.
4. Neurotransmitters diffuse across the synaptic cleft and bind to receptor cites.
5. A response is initiated in the postsynaptic neuron
Term
Synaptic delay
Definition
The time it takes for calcium to trigger exocytosis
Term
Channel-linked receptor
(Ionotropic receptor)
Definition
Ligand-gated channels that induce a fast response in the postsynaptic neuron when neurotransmitters bind to them.
Term
Postsynaptic Potential (PSP)
Definition
A change in membrane potential as a response to a neurotransmitter binding to a site on a postsynaptic neuron
Term
Metabotropic receptors
Definition
G Protein-regulated ion channels that induce a slow response when neurotransmitters bind to them
Term
Excitatory Postsynpatic Potential (EPSP)
Definition
A depolarization of the postsynpatic neuron through an excitatory synapse

Graded Potential
Term
Inhibitory Postsynaptic Potential (IPSP)
Definition
A hyperpolarization of the postsynaptic neuron through an inhibitory synapse

Graded Potential
Term
Neural Integration
Definition
Summation process in which the axon hillock adds up all the graded potentials and determines whether or not to release and action potential
Term
Frequency Coding
Definition
An effect in which the increase in strength of suprathreshold stimuli cause the frequency of action potentials to increase
Term
Modulatory Synapses
Definition
Regulate communication across another synapse
Term
Presynaptic Facilitation
Definition
The release of a neurotransmitter is enhanced
Term
Presynptic Inhibition
Definition
The release of a neurotransmitter is decreased
Term
Acetylcholine (ACh)
Definition
Most common neurotransmitter in the nervous system

Released from neurons in both the CNS and the PNS

Found in efferent neurons of both somatic and autonomic branches
Term
Choline Acetyl Transferase
Definition
Enzyme that synthesizes acetylcholine from acetyl CoA and choline
Term
What are the four major classes of neurotransmitters?
Definition
Acetlcholine
Biogenic Amines
Amino Acid Neurotransmitters
Neuropeptides
Term
Acetylcholinesterase
Definition
An enzyme that degrades acetylcholine into acetate and choline
Term
Cholinergic Receptor
Definition
Receptors for acetylcholine
Term
What are the two types of cholinergic receptors?
Definition
Nicotinic

Muscarinic
Term
Nicotinic Cholinergic Receptors
Definition
Ionotropic receptors that have two binding sites for acetylcholine

Located in the PNS (autonomic neurons and skeletal muscle cells)
Term
Muscarinic Cholinergic Receptors
Definition
Metabotropic receptors that operate through the action of a G protein

Located in CNS
Also can be found on some effector organs for the autonomic nervous system
Term
Biogenic Amine
Definition
Class of neurotransmitter derived from amino acid
Term
What are the three subclasses of biogenic amines?
Definition
Catecholamines
Serotonin
Histamine
Term
What are the three sub-subclasses of catecholamines?
Definition
Dopamine
Norepinephrine
Epinephrine
Term
Dopamine and Norepinephrine are released where?
Definition
By neurons in the CNS
(Norepinephrine can also be found in the PNS)
Term
Epinephrine is released where?
Definition
By neurons in the CNS but more commonly in the adrenal medulla
Term
Adrenergic receptors
Definition
Receptors for epinephrine and norepinephrine

Alpha 1, Alpha 2, Beta 1, Beta 2, Beta 3
Term
Epinephrine has the highest affinity for which receptor?
Definition
Beta 2
Term
Norepinephrine has the highest affinity for which receptors?
Definition
Alpha 1 and Beta 1
Term
Which two enzymes degrade catecholamines?
Definition
Monoamine Oxidase (MAO)
Catechol-O-methyltransferase (COMT)
Term
What are two functions of seratonin?
Definition
Sleep

Emotions
Term
What are the four subclasses of amino acid neurotransmitters?
Definition
Asparate

Glutamte

Glycine

GABA
Term
Which two subclasses of amino acid neurotransmitters are released at excitatory synapses?
Definition
Aspartate

Glutamate (Most common)
Term
Which two subclasses of amino acid neurotransmitters are released at inhibitory synapses?
Definition
Glycine

GABA (Most common)
Term
TRH
Definition
A neuropeptide that regulates release of another hormone called vasopressin which regulates urine output by the kidney
Term
Oxytocin
Definition
A neuropeptide that regulates contractions of the uterus and flow of milk from the breasts
Term
Substance P
Definition
A neuropeptide that decreases gastrointestinal motility
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