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Chapter 11
con't
48
Anatomy
Undergraduate 2
11/08/2011

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Term
CONDUCTION VELOCITY depends on
Definition
1. Axon diameter- the larger the axon’s diameter, the faster is conducts impulse
2. Degree of myelination- action potentials propagate because they are regenerated by voltage-gated channels in the membrane
Term
continuos conduction
Definition
AP jumps from each voltage gated ion channel: SLOW
Term
salutatory conduction
Definition
AP’s are triggered only at the nodes of ranvier
Term
group a fibers
Definition
CLASSIFICATION
Group A fibers- are mostly somatic sensory and motor fibers serving the skin, skeletal muscles, and joints. They have the largest diameter and thick myelin sheathes; conduct impulses at speeds ranging up to 150 m/s
Term
group b fibers
Definition
are autonomic nervous system motor fibers serving the visceral organs; visceral sensory fibers and the smaller somatic sensory fibers transmitting afferent impulses from the skin (such as pain);lightly myelinated fiber of intermediate diameter, transmit impulses at a rate of 15 m/s
Term
group c fibers
Definition
are autonomic nervous system motor fibers serving the visceral organs; visceral sensory fibers and the smaller somatic sensory fibers transmitting afferent impulses from the skin (such as pain); have the smallest diameter and are unmyelinated; incapable of salutatory conduction; conduct impulses at 1 m/s
Term
synapse
Definition
a junction that mediates information transfer from one neuron to the next or from a neuron to and effector cell; it’s where the action is
Term
axodendritic synapses
Definition
synapses between the axon endings of one neuron and those of other neurons
Term
axosomatic synapses
Definition
synapses between axon endings of one neuron and cell bodies of other neurons
Term
presynaptic neuron
Definition
the neuron conducting impulses toward the synapse
Term
postsynaptic neuron
Definition
the neuron transmitting the electrical signal away from the synapse
Term
electrical synapses
Definition
less common variety; Consist of gap junctions
Contain protein channels (connexons)
;Connexons- allow ions and small molecules to flow directly from one neuron to the next (electrically coupled)
;Provide a simple means of synchronizing the activity of all interconnected neurons
Term
chemical synapses
Definition
are specialized for release and reception of chemical neurotransmitters; made of two parts
Term
two parts of a chemical synapse
Definition
1. A knoblike axon terminal of the presynaptic neuron, contains synaptic vesicles that contains thousand of neurotransmitter molecules
2. A neurotransmitter receptor region on the membrane of a dendrite or the cell body of the postsynaptic neuron
Term
synaptic cleft
Definition
seperates presynaptic and post synaptic membranes
Term
summation
Definition
the integration of input from thousands of synapses in CNS
Term
spatial summation
Definition
Postsynaptic neuron is stimulated by a large number of terminals at the same time
Term
temporal summation
Definition
One or more presynaptic neurons transmit impulses in rapid-fire order
Term
Acetylcholine (Ach)
Definition
Released at neuromuscular junctions and some ANS neurons; Synthesized by enzyme choline acetyltransferase; Degraded by the enzyme acetylcholinesterase (AChE)
Term
Biogenic amines include:
Definition
Catecholamines
Dopamine, norepinephrine (NE), and epinephrine ; Indolamines; Serotonin and histamine; Broadly distributed in the brain; Play roles in emotional behaviors and help regulate the biological clock Imbalances are associated with mental disease
Term
Amino acids include
Definition
GABA—Gamma (γ)-aminobutyric acid; Glycine; Aspartate
Glutamate
Term
Peptides (neuropeptides) include
Definition
Substance P; Mediator of pain signals; Endorphins; Act as natural opiates; reduce pain perception; “runner’s high”; Gut-brain peptides produced by non-neural tissues
;Somatostatin and cholecystokinin
Term
Purines such as ATP:
Definition
Act in both the CNS and PNS; Produce fast or slow (2nd messenger) responses; Induce Ca2+ influx in astrocytes; Provoke pain sensations; e.g. caffeine blocks adenosine receptors
Term
Gases and lipids
Definition
Nitric oxide (NO); Synthesized “on demand” ; Activates the intracellular receptor guanylyl cyclase to make cyclic GMP; Involved in learning and memory; Causes intestinal smooth muscle to relax; Carbon monoxide (CO) is also a regulator of cGMP in the brain
Term
Gases and lipids
Definition
Endocannabinoids:Lipid soluble; synthesized on demand from membrane lipids; Bind with G protein–coupled receptors in the brain; Cannabinoid receptors are the most common G protein-coupled receptors in the brain; Involved in learning and memory
Term
Functional Classification of Neurotransmitters
Definition
Neurotransmitter effects may be excitatory (depolarizing) and/or inhibitory (hyperpolarizing
Term
Direct action
Definition
Neurotransmitter binds to channel-linked receptor and opens ion channels; Promotes rapid responses
Examples: ACh and amino acids
Term
Indirect action
Definition
Neurotransmitter binds to a G protein-linked receptor and acts through an intracellular second messenger; Promotes long-lasting effects; Examples: biogenic amines, neuropeptides, and dissolved gases
Term
Channel-Linked (Ionotropic) Receptors
Definition
Ligand-gated ion channels
Action is immediate and brief
Excitatory receptors are channels for small cations
Na+ influx contributes most to depolarization
Inhibitory receptors allow Cl– influx or K+ efflux that causes hyperpolarization
Term
Neuronal Pools
Definition
Functional groups of neurons that:Integrate incoming information; Forward the processed information to other destinations
Term
Simple neuronal pool
Definition
Single presynaptic fiber branches and synapses with several neurons in the pool
Term
Discharge zone
Definition
neurons most closely associated with the incoming fiber
Term
Facilitated zone
Definition
neurons farther away from incoming fiber
Term
Diverging circuit
Definition
o One incoming fiber stimulates an ever-increasing number of fibers, often amplifying circuits; May affect a single pathway or several; Common in both sensory and motor systems
Term
Converging circuit
Definition
Opposite of diverging circuits, resulting in either strong stimulation or inhibition; Also common in sensory and motor systems
Term
Reverberating (oscillating) circuit
Definition
Chain of neurons containing collateral synapses with previous neurons in the chain
Term
Parallel after-discharge circuit
Definition
Incoming fiber stimulates several neurons in parallel arrays to stimulate a common output cell
Term
Serial processing
Definition
Input travels along one pathway to a specific destination; Works in an all-or-none manner to produce a specific response; Example: reflexes—rapid, automatic responses to stimuli that always cause the same response
Term
Parallel processing
Definition
Input travels along several pathways; One stimulus promotes numerous responses Important for higher-level mental functioning; Example: a smell may remind one of the odor and associated
Term
Central nervous system
Definition
brain and spinal cord; integration and control centers
Term
peripheral nervous system
Definition
cranial nerves and spinal nerves; communication lines between the CNS and rest of body
Term
Sensory afferent division
Definition
PNS subdivision: somatic and visceral sensory nerve fibers; conducts impulses from the receptors to CNS
Term
motor efferent division
Definition
PNS subdivision: nerve fibers; conducts impulses from the CNS to effectors (muscles and glands)
Term
somatic nervous system
Definition
PNS subdivision of the motor division; somatic motor (voluntary) conducts impulses from the CNS to the skeletal muscles
Term
autonomic nervous system
Definition
subdivison of the motor part of the PNS; visceral motor (involuntary) conducts impulses from the CNS to cardiac muscles, smooth muscles and glands
Term
sympathetic
Definition
PNS: subdivision of ANS: mobilizes body system during activity; arouses
Term
parasympathetic
Definition
PNS subdivision of ANS; conserves energy; promotes house keeping functions during rest; calms
Term
neuroglia
Definition
glial cells; provide a supportive scaffolding for neurons
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