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123 Cards in this Set
- Front
- Back
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Sensory (_________) neurons
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detect changes in environment called stimuli
afferent transmit information to brain or spinal cord |
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Interneurons (_________ _________)
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association neurons
lie between sensory & motor pathways in CNS outgoing motor pathways of the CNS |
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__% of our neurons are interneurons
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90
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Motor (___________) neurons
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efferent
send signals predominantly to muscle and gland cells organs that carry out responses called effectors |
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Three Fundamental Properties of Neurons
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Excitability (irritability)
Conductivity Secretion |
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Excitability (irritability)
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highly responsive to stimuli
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Conductivity
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producing traveling electrical signals
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Secretion
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when electrical signal reaches end of nerve fiber, a neurotransmitter is secreted
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Central Nervous System (CNS)
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brain and spinal cord enclosed in bony coverings
gray matter forms surface layer & deeper masses in brain & H-shaped core of spinal cord cells & synapses white matter lies deep to gray in brain & surrounding gray in spinal cord axons covered with lipid sheaths |
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Peripheral Nervous System (PNS)
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nerve = bundle of nerve fibers in connective tissue
ganglion = swelling of cell bodies in a nerve |
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nerve
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nerve = bundle of nerve fibers in connective tissue
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ganglion
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ganglion = swelling of cell bodies in a nerve
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soma = _______________ = ____________
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soma = neurosoma = perikaryon
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soma
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single, central nucleus with large nucleolus
cytoskeleton of neurofibrils & microtubules ER compartmentalized into nissl bodies lipofuscin product of breakdown of worn-out organelles -- more with age |
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Dendrites have Vast number of short _____________
For receiving signals from neurons |
Vast number of short dendrites
For receiving signals from neurons |
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Neurons have singe ___________ __________ arising from _______ _________ for rapid conduction of nerve signals
axoplasm & axolemma & synaptic vesicles |
Singe axon collaterals arising from axon hillock for rapid conduction of nerve signals
axoplasm & axolemma & synaptic vesicles |
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Multipolar neuron
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most common
many dendrite/one axon |
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Bipolar neuron
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one dendrite/one axon
olfactory, retina, ear |
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Unipolar neuron
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sensory from skin & organs to spinal cord
long myleninated fiber bypassing soma |
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Oligodendrocytes
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Oligodendrocytes form myelin sheaths in CNS
each wraps processes around many nerve fibers |
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Astrocytes
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Astrocytes
protoplasmic astrocytes contribute to blood-brain barrier, secrete nerve growth factors & regulate composition of tissue fluid fibrous astrocytes form framework of CNS |
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Ependymal cells
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Ependymal cells line cavities & form CSF
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Microglia (macrophages)
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Microglia (macrophages) formed from monocytes
concentrate in areas of infection, trauma or stroke |
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Schwann cells
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Schwann cells myelinate fibers of PNS
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Satellite Cells
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Satellite cells with uncertain function
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Name the six neuroglial cells
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oligodendrocytes
astrocytes ependymal cells microglia (macrophages) schwann cells satelilite cells |
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Myelin Sheath
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oligodendrocytes in CNS & schwann cells in PNS
formed from wrappings of plasma membrane 20% protein & |
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In PNS, hundreds of layers wrap axon
the outermost coil is _______ cell covered by basement membrane & ______________ |
In PNS, hundreds of layers wrap axon
the outermost coil is schwann cell covered by basement membrane & endoneurium |
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In CNS, no ____________ or _____________
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In CNS, no neurilemma or endoneurium
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Gaps between myelin segments =
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Gaps between myelin segments = nodes of Ranvier
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________________________________ & ________ form trigger zone where signals begin
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Initial segment (area before 1st schwann cell) & axon hillock form trigger zone where signals begin
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Unmyelinated Axons
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Schwann cells hold small nerve fibers in grooves on their surface with only one membrane wrapping
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Disease in which:
Oligodendrocytes and myelin sheaths of the CNS degenerate Replaced by hardened scar tissue Nerve conduction is disrupted Double vision, blindness, speech defects, neurosis, tremors or numbness Death in ____-______ years after onset |
Multiple Sclerosis
7-32 |
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In this disease:
Hereditary disorder seen mainly in infants of Eastern European Jewish ancestry Abnormal accumulation of a glycolipid in the myelin sheath Blindness, loss of coordination, and dementia Death by age ___-____ |
Tay-Sachs
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Speed of signal transmission along nerve fibers
depends on |
diameter of fiber & presence of myelin
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small, unmyelinated fibers last ____________ m/sec
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small, unmyelinated fibers = 0.5 to 2.0 m/sec
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small, myelinated fibers = ___________-_____ m/sec
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small, myelinated fibers = 3 to 15 m/sec
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large, myelinated fibers = up to ____ m/sec
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large, myelinated fibers = up to 120 m/sec
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Functions
of a nerve signal slow signals _______________________________________ fast signal _____________________________________ |
slow signals for secreting stomach acid or dilating the pupil
fast signals supply motor commands to skeletal muscles & transport sensory signals for vision and balance |
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Regeneration of Peripheral Nerve Fibers
Can occur if soma and neurilemmal tube is intact Stranded end of axon & myelin sheath degenerate Healthy axon stub puts out several sprouts Tube guides lucky sprout back to its original destination No neurilemma tube in |
Nerve fiber is _____ and _______ end of axon cannot survive
Stranded end of axon & myelin sheath _________ Healthy axon stub puts out several sprouts Tube guides lucky sprout back to its original destination No ___________ tube in |
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HIV can enter the brain and cause infection. Which type of cell would you expect to see in areas under attack by the virus? Oligodendrocytes
Ependymal Cells Astrocytes Schwann cells Microglio |
Microglio
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Which organelle is not functioning properly in order to allow for accumulation of a glycolipid in those with Tay-sachs
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Lysosome
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Neuron doctrine
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nerve pathway is not a continuous “wire” but a series of separate cells
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Neuronal communication is based on mechanisms for producing
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Neuronal communication is based on mechanisms for producing electrical potentials and currents
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Electrical potential
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Electrical potential is difference in concentration of charged particles between different parts of the cell
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Electrical current
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Electrical current is flow of charged particles from one point to another within the cell
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_________ cells are polarized
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living
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Explanation for -70 mV resting potential
membrane very permeable to ___ cytoplasmic anions that can not escape due to ____ or _____ ( phosphates, sulfates, organic acids, proteins) membrane much____ permeable to Na+ Na+/K+ pumps out ___ Na+ for every __ K+ it brings in works continuously & requires great deal of ATP necessitates glucose & oxygen be supplied to nerve tissue |
Explanation for -70 mV resting potential
membrane very permeable to K+ cytoplasmic anions that can not escape due to size or charge ( phosphates, sulfates, organic acids, proteins) membrane much less permeable to Na+ Na+/K+ pumps out 3 Na+ for every 2 K+ it brings in works continuously & requires great deal of ATP necessitates glucose & oxygen be supplied to nerve tissue |
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Na+ is more concentrated ________ of cell (____) and K+ more concentrated _____ the cell (____)
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Na+ is more concentrated outside of cell (ECF) and K+ more concentrated inside the cell (ICF)
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Local disturbances in membrane potential
occur when neuron is stimulated by _____,______, ______ or __________ disturbance depolarization is (positive or negative?) shift in potential due to opening of gated _______ channels ________ diffuses for short distance inside membrane producing a change in voltage called |
Local disturbances in membrane potential
occur when neuron is stimulated by chemicals, light, heat or mechanical disturbance depolarization is positive shift in potential due to opening of gated sodium channels sodium diffuses for short distance inside membrane producing a change in voltage called |
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Differences from action potential
are _______ (vary in magnitude with stimulus strength) are ________ (get weaker the farther they spread) are __________ as K+ diffuses out of cell can be either __________ or _________ (hyperpolarize) |
Differences from action potential
are graded (vary in magnitude with stimulus strength) are decremental (get weaker the farther they spread) are reversible as K+ diffuses out of cell can be either excitatory or inhibitory (hyperpolarize) |
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Explain the following,
Differences from action potential are graded |
vary in magnitude with stimulus strength
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Explain the following,
Differences from action potential are decremental |
get weaker the farther they spread
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Explain the following,
Differences from action potential are reversible |
are reversible as K+ diffuses out of cell
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trigger zone has ____ channels/um2 (normal is _____)
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500
normal is 75 |
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Reach threshold potential(________mV)
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Reach threshold potential(-55mV)
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Voltage-gated Na+ channels _____ (Na+ ______for depolarization)
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Voltage-gated Na+ channels open (Na+ enters for depolarization)
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During action potential
Voltage-gated Na+ channels ______ (Na+ ______ for depolarization) Passes 0 mV & Na+ channels _______ (peaks at +35) K+ gates fully ______ (K+ ______) produces repolarization Negative overshoot produces hyperpolarization |
Voltage-gated Na+ channels open (Na+ enters for depolarization)
Passes 0 mV & Na+ channels close (peaks at +35) K+ gates fully open (K+ leaves) produces repolarization Negative overshoot produces hyperpolarization |
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Characteristics of action potential
follows an ____ or _____ law and thus are not graded are _______ (do not get weaker with distance) are ___________ (once started goes to completion and can not be stopped) |
Characteristics of action potential
follows an all-or-none law and thus are not graded are nondecremtal (do not get weaker with distance) are irreversible (once started goes to completion and can not be stopped) |
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refractory period
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resistance to restimuation
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absolute refractory period
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as long as Na+ gates are open
no stimulus will trigger AP |
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relative refractory period
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as long as K+ gates are open
only especially strong stimulus will trigger new AP |
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Impulse Conduction in Unmyelinated Fibers
Has voltage-gated Na+ channels along its _____ _______ Action potential in __________ zone begins chain reaction that travels to end of axon Action potential occurs in one spot Nerve signal is a _____________________ can only travel ______ _______ soma because of _________ ____________ Nerve signal travels at 2m/sec in unmyelinated fiber but is nondecremental |
Has voltage-gated Na+ channels along its entire length
Action potential in trigger zone begins chain reaction that travels to end of axon Action potential occurs in one spot Nerve signal is a chain reaction of action potentials can only travel away from soma because of refractory period Nerve signal travels at 2m/sec in unmyelinated fiber but is nondecremental |
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Nerve signal travels at _m/sec in unmyelinated fiber but is ________________
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Nerve signal travels at 2m/sec in unmyelinated fiber but is nondecremental
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describe the membrane situation in the resting state in the neuron
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At resting membrane potential, all of the voltage gated channels are closed
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IN Saltatory Conduction in Myelinated Fibers
________-_________ channels needed for action potentials |
Voltage-gated channels needed for action potentials
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IN Saltatory Conduction in Myelinated Fibers
Na+ inflow at node generates action potential, this is _____ but non_______ Na+ diffuses along inside of _____________ to next node, this is _______ but __________ Excitation of __________-_______ gates with generate next action potential here |
slow but nondecremental;
axolemma; fast but decremental Excitation of voltage-regulated gates with generate next action potential here |
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IN Saltatory Conduction in Myelinated Fibers
action potentials jump from __________ to ____________ |
Notice how the action potentials jump from node of Ranvier to node of Ranvier
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First neuron in path releases neurotransmitter onto second neuron that responds to it
1st neuron is ____________ neuron 2nd neuron is __________ neuron |
First neuron in path releases neurotransmitter onto second neuron that responds to it
1st neuron is presynaptic neuron 2nd neuron is postsynaptic neuron |
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Synapse may be axodendritic, axosomatic or axoaxonic
Number of synapses on postsynaptic cell variable ______ on spinal motor neuron ________ on neuron in cerebellum |
8000
100000 |
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Histological observations revealed a ___ to ____ nm gap between neurons (synaptic cleft)
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20-40
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What makes up acetylcholine
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Acetylcholine is formed from acetic acid & choline
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Monoamines synthesized by _______________
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Monoamines synthesized by replacing -COOH in amino acids with another functional group
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Examples of catecholamines
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epinephrine, norepinephrine & dopamine
epinephrin=adrenaline |
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Examples of indolamines
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seratonin and histamine
Seratonin enhances mood Histamine |
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A neuropeptide is a chain of _ to __ amino acids that ________________
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Chains of 2 to 40 amino acids that modify actions of neurotransmitters
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Neuropeptides are stored in
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axon terminal as larger secretory granules (called dense-core vesicles)
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Neuropeptides may be released with _________ or only under ____________ _____________
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May be released with neurotransmitter or only under stronger stimulation
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Example of a neuropeptide released from nonneural tissue
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gut-brain peptides cause food cravings
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Cholinergic synapse produces ________ effect
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inotropic
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Describe the inotropic effect that occurs
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nerve signal opens voltage- gated calcium channels
triggers release of ACh which crosses synapse ACh receptors trigger opening of Na+ channels producing local potential (postsynaptic potential) when reaches -55mV, triggers action potential to begin synaptic delay (.5 msec) is time from arrival of nerve signal at synapse to start of AP in postsynaptic cell |
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During Metabotrophic Synapse Transmission
Neurotransmitter uses _____ messenger such as ______ ______ to alter metabolism of ___________ cell |
Metabotrophic Synapse Transmission
Neurotransmitter uses 2nd messenger such as cyclic AMP to alter metabolism of postsynaptic cell |
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Mechanisms to turn off stimulation
_____________of neurotransmitter away from synapse into ECF where astrocytes return it to the neurons synaptic knob reabsorbs amino acids and monoamines by endocytosis & breaks them down with _________________________ acetylcholinesterase degrades _____ in the synaptic cleft _________ reabsorbed & recycled |
Mechanisms to turn off stimulation
Diffusion of neurotransmitter away from synapse into ECF where astrocytes return it to the neurons synaptic knob reabsorbs amino acids and monoamines by endocytosis & breaks them down with monoamine oxidase acetylcholinesterase degrades AChin the synaptic cleft choline reabsorbed & recycled |
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______________ modify synaptic transmission
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Neuromodulators modify synaptic transmission
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How do neuromodulators modify synaptic transmission
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raise or lower number of receptors
alter neurotransmitter nitric oxide stimulates neurotransmitter release |
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Local anesthetics like novocaine prevent conduction of pain signals in a sensory nerve. Which of the following would NOT be a way in which an anesthetic could prevent pain signals from being sent to the CNS?
Block the opening of voltage-gated Na+ channels in the post-synaptic neuron Prevent Ca 2+ from entering the presynaptic neuron Block neurotransmitter receptors on postsynaptic neuron Increase secretion of neurotransmitter from the presynaptic neuron |
Increase secretion of neurotransmitter from the presynaptic neuron
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The more synapses a neuron has, the greater its _________________________ capability
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The more synapses a neuron has, the greater its information-processing capability
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Pyramidal cells
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cells in cerebral cortex with 40,000 synapses
cerebral cortex estimated to contain 100 trillion synapses |
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____________ _______________
are decision-making components of the nervous system |
chemical synapses
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Chemical synapses have the ability to
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process, store & recall information is due to neural integration
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Neural integration is based on types of ________ ______________ produced by neurotransmitters
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Neural integration is based on types of postsynaptic potentials produced by neurotransmitters
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excitatory postsynaptic potentials (EPSP)
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a positive voltage change causing postsynaptic cell to be more likely to fire
result from Na+ flowing into the cell glutamate & aspartate are excitatory neurotransmitters |
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name two excitatory neurotransmitters
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glutamte and aspartate
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inhibitory postsynaptic potentials (IPSP)
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a negative voltage change causing postsynaptic cell to be less likely to fire (hyperpolarize)
result of Cl- flowing into the cell or K+ leaving the cell glycine & GABA are inhibitory neurotransmitters |
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Name two inhibitory neurotransmitters
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glycine and GABA
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typical EPSP has a voltage of ___ mV & lasts ____ msec
a typical neuron would need ____ EPSPs to reach threshold |
.5; 20; 30
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This occurs when single synapse receives many EPSPs in a short period of time
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temporal summation
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This occurs when single synapse receives many EPSPs from many presynaptic cells
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Spatial summation
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One presynaptic neuron suppresses another by releasing inhibitory neurotransmitter ______
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GABA
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Inhibitory neurotransmitter GABA prevents
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voltage-gated calcium channels from opening in neuron S so it releases less or no neurotransmitter onto neuron R and fails to stimulate it
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Qualitative information
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salty vs sweet; high pitched vs low pitched noise
depends upon which neurons are fired |
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Quantitative information
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mild vs strong flavor; loud vs soft noise
strong stimuli excite different neurons strong stimuli causes a more rapid firing rate |
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____ judges stimulus strength from firing frequency of sensory neurons
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CNS
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Physical basis of memory is a pathway of cells
called a _______ _______ or ______ new synapses or existing synapses have been modified to make transmission easier (synaptic plasticity) |
memory trace or engram
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process of making transmission easier
correlates with different forms of memory Immediate memory Short-term memory Long-term memory |
Synaptic potentiation
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synaptic plasticity
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new synapses or existing synapses have been modified to make transmission easier
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Ability to hold something in your thoughts for a few seconds
Indispensable to the ability to read Feel for the flow of events Our memory of what just happened “echoes” in our minds for a few seconds |
Immediate Memory
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Lasts from a few seconds to a few hours
quickly forgotten if distracted with something new |
Short-Term Memory
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with this memory
Working memory allows us to keep something in mind long enough search for keys, dial the phone reverberating circuits |
short-term memory
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________ causes memory to longer lasting
Tetanic stimulation (rapid,repetitive signals) causes Ca+2 accumulates & cell becomes more likely to fire |
Facilitation
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Posttetanic potentiation
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(to jog a memory)
Ca+2 level in synaptic knob has stayed elevated long after tetanic stimulation, so little stimulation will be needed to recover that memory |
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Physical remodeling of synapses with new branching of axons or dendrites
Molecular changes called long-term potentiation tetanic stimulation causes ionic changes (Ca+2 entry) neuron produces more neurotransmitter receptors synthesizes more protein used for synapse remodeling releases nitric oxide signals presynaptic neuron to release more neurotransmitter |
Long-Term Memory
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Two types of long term memory
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Declarative
Procedural |
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This type of long term memory
is retention of facts as text or words |
Declarative
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This type of long term memory
is retention of motor skills -- keyboard |
Procedural
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This disease affects
__% of population over 65; __% by age 85 |
11;47
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Symptoms of alzheimer disease
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memory loss for recent events, moody, combative, lose ability to talk, walk, and eat
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This disease is characterized by
atrophy of some gyri (folds) in cerebral cortex neurofibrillary tangles & senile plaques |
alzheimers disease
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Degeneration of cholinergic neurons & deficiency of ACh and nerve growth factors
Genetic connection confirmed for some forms |
alzheimers disease
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Progressive loss of motor function beginning in 50’s or 60’s -- no recovery
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Parkinsons Disease
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Dopamine
prevents |
excessive activity in motor centers (basal ganglia)
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Tremor
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pill-rolling motion, facial rigidity, slurred speech, illegible handwriting, slow gait
Parkinsons disease |
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Treatment for parkinsons disease
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drugs and physical therapy
dopamine precursor can cross blood-brain barrier deprenyl (MAO inhibitor) slows neuronal degeneration surgical technique to relieve tremors |
