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196 Cards in this Set
- Front
- Back
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A neuron completely within the CNS that is capable of modulating the input/output linkage for a reflex. It is an efferent neuron
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interneuron
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What is the role of the myotactic reflex in the neural control of limb movement?
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assists in maintaining an upright posture in the face of unexpected changes; protective mechanism; allows for separation of upper/lower motor neuron injuries in neurological exams
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What are the two types of slow/passive signals?
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Receptor potential and synaptic potential (both travel short distances)
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What type of signal is an action potential?
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conductive/propagated
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Why would you use the Nernst equation?
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to describe forces that create mb potentials in neurons
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What equation would you use to describe the electrochemical equilibrium with more than one permeant ion?
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Goldman Equation
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Describe hyperkalemia.
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abnormally high levels of K+ ions in the blood that cause a reduction in electrical potential. This brings the nerve and heart muscle closer to depolarization threshold value and initiates the AP. The cell is less likely to fire an action potential because the depolarization closes the inactivation gates of the Na channels. Resulting in tetany, parethesias and weakness with paralysis eventually occurring.
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The resting mb potential is close to the equilibrium potentials of what 2 ions?
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K+ & Cl- because the permeability of these ions at rest is high
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What two things is the selectivity of ion channels based upon?
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charge and size
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What is the voltage clamp method used for?
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to define the ionic permeability of the mb and indicate how the mb potential influences ionic current flow across the mb
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What is command voltage?
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the voltage to be maintained during the voltage clamp method
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Conductance is the reciprocal of what?
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mb resistance
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If conductance increases, what else increases?
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current increases
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A voltage dependent mb conductance that occurs during depolarization, in which there is a decrease in charge on the mb, but no net ion mvmt occurs.
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capacitative current
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A voltage-dependent mb conductance that occurs during depolarization, in which ions move across the mb
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ionic current
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An alkaloid neurotoxin found in certain puffer fish, tropical frogs, and salamanders; blocks the Na+ current w/o affecting K+ current
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tetrodotoxin
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An ion that blocks potassium current w/o affecting Na current
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tetraethyl ammonium ions
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A brief period in which the action potential leaves the Na channels inactivated and the K channels activated, and these transitory changes make it harder for the axon to produce subsequent action potentials during this interval; limits the number of AP that a given nerve cell can produce per unit time
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refractory period
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A lipid insulator that increases the mb resistance and reduces the passive currents ability to leak out of the axon, and speeds up the AP from .5 m/sec to 150 m/sec
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Myelin
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A disease in which multiple regions of demyelination and inflammation along an axonal pathway; Leads to monocular blindness, motor weakness, paralysis, abnormal somatic sensations, double vision, and dizziness
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multiple sclerosis
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An ion channel that allows 1 ion to pass; selectively permaeable to Na+, Ca ++, K+, and Cl-
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voltage-gated ion channel
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An ion channel that allows 2+ ions to pass, less selective, and binds to an extracellular NT to open the ion channel or can use a second messenger method to open the ion channel (these are more selective)
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ligand gated ion channel
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What is a cardiac glycoside that inhibits the Na/K pump by preventing the dephosphorylation of the ATPase. Leads to increases in intracellular Na, and intracellular K decreases.
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ouabain
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obstructs Na channels paralyzing animals until the predator can ingest them
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tetrodotoxin
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a chemical homologue of tetrodotoxin that obstructs Na channels; comes from shellfish that have ingest "red tide" dinoflagellates
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saxitoxin
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A toxin that slows the inactivation of Na channels, prolonging the AP, thereby scrambling the info flow
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alpha toxin of scorpion toxin
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A toxin that shift the voltage dependence of Na+ channel activation, causing Na channels to open at potentials much more negative potentials than normal disrupting AP
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beta toxin of scorpion toxin
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a peptide toxin that blocks K+ channels
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dendrotoxin
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What is stiffness due to excessive electrical excitability
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myotonia
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A Ca++ channel mutation disease that causes migraines for 1-3 days
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Familial hemiplegic migraine (FHM)
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A disease caused by a mutation causes Ca++ channels to be truncated and prevents normal assembly; Symptoms are recurrent attacks of abnormal limb mvmt, severe ataxia, vertigo, nausea, & headache; attacks are usually caused by emotional stress, alcohol, & exercise
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Episodic Ataxia Type 2 (EA2)
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A recessive retinol disorder that causes night blindness, decreased visual acuity, myopia, nystagmus (rhythmic mvmt of the eyes), strabismus (visual axis of eyes are not directed to the same point)
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X-linked congenital stationary night blindness (CSNB)
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What happens with complete CSNB?
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rod photoreceptors are nonfunctional
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What happens with incomplete CSNB?
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subnormal fxning of both rods and cones and Ca++ channels are truncated; decreased Ca++ current and NT release from photoreceptors
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An Na+ channel defect which slows the Na+ channel inactivation; 1 mutation on the chromosome 2/alpha subunit and 1 on 19/beta; begins in infancy and continues through early puberty and leads to neuronal hyperexcitability
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Generalized epilepsy w/ febrile seizures (GEFS)
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A disease that causes brief frequent seizures that disappear spontaneously; K+ channel mutations in at least 2 genes; there is a reduction of K+ current through the channels that accounts for the hyperexcitability associated with this defect
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Benign Familial Neonatal Convulsion (BFNC)
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A disease characterized by brief episodes of ataxia due to mutations in the K+ channels; the mutant channels inhibit the nonmutant channels causing impairment of AP repolarization
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Episodic Ataxia Type 1 (EA1)
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A disease that leads to irregular heartbeat due to a problem with the K+ channels in cardiac muscle
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Long QT Syndrome
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Where are small molecule NTs stored and how do they get to the synapse?
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small clear core vesicles that are made in the nerve terminal and enzymes make them travel via slow axonal transport (.5-5 mm/day)
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Where are peptide NTs stored and how do they get to the synapse?
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dense core vesicles that are made in the cell body and are moved to terminal via fast axonal transport which uses microtubule tracks powered by ATP motor proteins (400 mm/day)
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What is a passive potential?
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many EPP are released simultaneously
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What is an MEPP?
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miniature end plate potential; small, spontaneous depolarization of the mb potential of skeletal muscle cells, caused by the release of a single quantum of Ach
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What is cadmium?
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a calcium channel blocker
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What are the vesicle mb proteins?
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synaptobrevin and synaptotagmin (binds Ca)
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What are the presynaptic plasma mb proteins?
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syntaxin, SNAP 25, SNARE proteins (form macromolecule complex and fxn to bring the vesicle & presynaptic mb in close apposition to promote fusion and exocytosis)
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Describe Lambert-Eaton myasthenic syndrome.
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complication of pts w/ certain types of cancer (small cell cancer); # of quanta in EPP greatly reduced and amplitude of spontaneous MEPP greatly reduced; impairs evoked EPP release; decrease in Ca channel currents b/c of reduced # channels due to Ab attack; removing Ab by plasma exchange reduces muscle weakness, increases Ca++, and providing immunosuppressive drugs assists them
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What toxins are responsible for botulism and tetanus?
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clostridial toxins- proteases that cleave SNARE proteins; B, D, F, & G cleave synaptobrevin, C- syntaxin, A&E- SNAP-25
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What toxin is found in female black widows venom?
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alphalatrotoxin- causes a massive discharge of the synaptic vesicles even when Ca is absent; binds to neurexins, which binds to synaptotagmin and binds to C1 to activate and intracellular signalling cascade
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Lowering external Na+ shift the reverse potential to the
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L
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Polarity and magnitude of the mb EPC depend on the
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electrochemical driving force
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What are NTs called if there is more than 1 present w/in a nerve terminal?
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co-transmitters; packaged in different vesicles so that they don't need to be released simultaneously (differently released according to the pattern of synaptic activity and low frequency often releases small molecule NTs)
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What are the types of small molecule NTs?
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ACh, aa's, purines, catecholamines, indoleamines (serontonin- 5-HT), and imidazoleamines (histamine)
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What are the different types of aa's NTs?
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glutamate, aspartate, GABA, and glycine
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What is a purine NT?
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ATP
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What are the 3 types of catecholamine NTs?
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epinephrine, norepinephrine, and dopamine
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What are the 5 biogenic amine NTs?
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dopamine, NE, E, 5-HT, and histamine
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What are the peptide neurotransmitters?
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enkephalins, endorphins, and somatostatins-14
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Where are small molecule NTs synthesized?
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In the synaptic bulb; enzymes are transported by slow transport to the bulb
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Excitotoxity is often caused by
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ischemia, hypoglycemia, trauma, and repeated intense seizures
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What do all the biogenic amines have in common?
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They are excitatory
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What neuronal area is NE limited to and why is it important?
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locus coeruleus (brainstem nucleus that projects diffusely to the midbrain and telencephelan); modifying sleep & wakefulness, attention, and feeding behavior
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What neuronal area is E limited to and why is it important?
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rostral medulla and lateral tegmental system- project to hypothalamus and thalamus; no know fxn
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What neuronal area is dopamine limited to and why is it important?
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substantia nigra & ventral tegmental area; coordination of body mvmts
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What neuronal area is histamine limited to and why is it important?
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tuberomammillary nucleus of the hypothalamus; released from mast cells and platelets in response to an allergic rxn and tissue damage; mediates arousal and attention
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What neuronal area is serotonin limited to and why is it important?
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raphe region of the pons and cerbellum; regulation of sleep and wakefulness
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What type of drug inhibits the monoamine oxidase pathway (MAO inhibitors or MAOI's) required to catabolism of the amine NTs and blockers of serotonin Rs? Give exs
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Antianxiety; Librium and Valium (aminergic transmission blockers); also increase the efficacy of transmission at GABA synapses rather than acting at aminergic synapses
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aminergic transmission by blocking the breakdown of amines (MAOI), blocking the reuptake of NE and other amines (tricyclics), or blocking the reuptake of serotonin (Prozac-doesn't effect NE reuptake)
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Antidepressants
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What drugs stimulate NE release from nerve terminals, resulting in a transient "high"?
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stimulants (amphetamines)
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What are the 3 types of smooth m AP?
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wave, spike, plateau
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How does the rate of rise of AP in a spike of sm differ from cardiac and skeletal m?
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lower because the Ca++ channels open more slowly than Na+ channels
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How is a plateau AP created in sm?
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mb repolarization is delayed; this method accounts for the prolonged contraction that occurs in the uterus; Ca++ channels remain open much longer than Na+ channels
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What is a slow wave AP in sm?
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regular repetitive oscillations in mb potential resulting in spontaneous electrical activity; self-excitatory sm; if strong enough can initiate AP or multiple APs; illicits a series of rhythmical contractions; this is not a AP or self regenerative but a local property of the sm fibers
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Are SR Ca++ pumps affected by high Ca++?
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yes, inhibited by high SR Ca++ levels; thats why calsequestrin and calreticulin are important
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What types of muscle is calsequestrin found in?
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cardiac and skeletal
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What types of muscle is calreticulin found in?
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smooth m
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In cardiac m, what regulatory protein inhibits the SR Ca++ pump activity?
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Phospholamban; when it is phosphorylated then it cannot inhibit the pump- phosphorylated by PKA
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What additional step is required to terminate contraction in smooth muscle that is not required in skeletal or cardiac?
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dephosphorylation of the MLCK by myosin light chain phosphatase; the other muscles just require the sequestering of Ca++
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How does muscle length influence tension developement?
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It determines the degree of overlap between actin and myosin. At higher loads, the velocity of shortening is lower because more cross bridges are simultaneously active (isotonic)
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What increases the force in skeletal muscle contraction?
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frequency summation and multiple fiber summation (CNS can activate individual motor units asynchronously so that some units are developing tension while others are relaxing
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What increases the force in cardiac m?
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increasing entry of Ca++; therefore it regulates by modulating the magnitude of the rise in Ca++ or by altering the Ca++ sensitivity of the regulatory proteins
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What increases the contractile force of smooth m?
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relative balance btwn phosphorylation and dephosphorylation of MLCs and the Ca++ sensitivity of proteins that regulate contraction
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Describe Slow Twitch/ Type 1
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fatigue resistant, high myoglobin, low glycogen content, lots of mitochondria, and oxidative metabolism
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Describe Fast Twitch type IIa
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fatigue resistant, red due to highest myoglobin content, oxidative phosphorylation, highest amount of mitochondria, and abundant stores of glycogen
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Describe fast twitch type IIb
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fatiguable, white due to low myoglobin content, glycolytic, few mitochondria, and high glycogen content
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A mechanoreceptor that is located between dermal papillae and the epidermis of the fingers, palms, and soles; accounts for 40%of sensory innervation of the human hand; rapid adapting, sense dynamic touch and pressure
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Meissner's
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Mechanoreceptors whose core consists of liquid; in subcutaneous tissue, viscera, and interosseous mbs; rapidly adapting, low response threshold, sense dynamic deep pressure & vibration; 10-15% of cutaneous R
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Pacinian
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A mechanoreceptor which is peptide releasing; located on all skin and hair follicles; slow adapting, sense tactic discrimination of shape, texture, and rough edges; in epidermis beneath dermal ridges; accounts for 25% of hand mechanoreceptors
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Merkel's
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oriented along stretch lines; slow adapting; sense stretching; deep in skin as well as located in ligaments and tendons; involved in proprioception and 25% of R in the hand
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ruffini's
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What are the 4 types of mechanoreceptors that are low threshold and are all encapsulated (A beta fibers)
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Meissner's, Pacinian, Ruffini's, and Merkel's
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Where are A delta and C fibers found?
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free nerve endings (high threshold of activation)
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What types of fibers do MSOs have?
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Ia and II
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What types of fibers do golgi tendon organs have?
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Ib
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What type of receptor adaptation responds maximally but briefly to onset of the stimuli; response decreases if the stimulus is maintained; provide the dynamic qualities of the stimulus
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rapidly adapting or phasic
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What type of receptor adaptation receptor keeps firing as long as the stimulus is present; conveys info about the persistence of a stimulus or the static qualities?
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slow adapting or tonic
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Describe a region of most sensitive tactile discrimination.
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smallest receptive fields, most abundant # of encapsulated mechanoreceptors (fingers, palm, face, toes)
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What are the 3 low threshold mechanoreceptors?
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MSOs, golgi tendon organs, and joint receptors
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What mechanoreceptor provides information about muscle length/stretch using 4-8 intrafusal fiber in a CT capsule with 1 nuclear bag fiber and multiple nuclei chain fibers. These richly supply extraoccular mm and intrinsic mm of the hand & neck.
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MSO
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What type of mechanoreceptor is innervated by Ib afferents, distributed among collagen fibers that form the tendons, and provides info about muscle tension
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golgi tendon organs
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What type of mechanoreceptor is a rapidly adapting receptor in and around the joint capsule tha provides dynamic info about limb position and joint mvmt. These are not well understood
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joint R
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The process of electrogenesis contributes what amount of potential to the resting mb potential in the neuron?
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10 mV
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During the skeletal muscle contraction, the total isometric stress is
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greater than the passive stress at any length
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The latent period of a muscle twitch is representative of the time when Ca++ is diffusing from
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lateral cisternae to A band
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The muscuranic action of ACh on sympathetic neurons is due to
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opening of Na+ channels
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The plastic, adaptive capability of the chemical synapse is due to mechanisms which control what ion channels?
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Ca++
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The pretensioning of skeletal m fibers which prevents the spindle from becoming silent during contraction is controlled by what nerve?
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Ib
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How is NE converted in the adrenal medulla to E?
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hydroxylation
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Name 2 neuroactive peptides in the CNS.
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LH releasing factor and dopamine
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What type of R adaptation provides predictive info?
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slow adapting
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What types of stimulus do A gamma nerves respond to?
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dangerously intense mechanical or mechanothermal stimuli; R fields consist of clusters of sensitive spots; small R fields, localized, and flexor reflexes
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What types of stimulus do C nerves respond to?
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thermal, mechanical, and chemical stimuli; polymodal; large field, diffuse, tonic reflexes; dull, aching pain
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Why are the receptive fields of all pain sensitive neurons large?
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detection of pain is more important than its precise location; axons only discharge when stimulus is strong enough to cause tissue damage
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What is enhanced sensitivity and responsitivity to stimulatin of the area around the damaged tissue (like increased sensitivity to T that occurs after a sunburn)?
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hyperalgesia
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What types of sensitization is the result of an interaction of nociceptors with the "inflammatory soup" of various substances released when tissue is damaged? enhances repsonsiveness of nociceptive endings
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peripheral sensitization
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What type of pain is caused by cross talks between visceral and somatic systems
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referred pain
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Where is visceral pain felt?
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cutaneously
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When and why does phantom pain occur?
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amputation of a limb; neurons that have lost their inputs, respond to tactile stimulation of other body parts in close proximity
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Electrical and pharmacological stimulation of certain regions of what organ produces relief of pain?
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midbrain
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What type of meds is a powerful analgesic that targets a variety of brain regions, especially periaqueductal grey matter and the rostral ventral medulla
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endogenous opioids
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Are thermoreceptor slow or fast adapting?
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slow
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What temperature should the brain always be kept at?
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37
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What T range do cold receptors range over? What happens when they drop below a certain T? And is the curve steep?
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10-40 with steady discharge from 24-28; below release cold, local anesthetic due to the ceasing of firing of R; shallow curve
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What T range do hot R range? What happens if they go above this? And describe the curve?
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30-46 increasing the frequency of fires until the curve falls steeply and nociceptive pain begins
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What are the 2 parts of the outer layer of the eye?
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sclera and cornea
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What is the tough white fibrous tissue on the outer layer of the eye?
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sclera
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What is the very front layer of the eye that is a specialized transparent layer that permits light rays to enter the eye?
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cornea
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What is the middle layer of the eye made of?
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iris & ciliary body
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What is the colored middle layer of the eye that contains 2 sets of opposing muscles that control the size of the eye. This is the most ant component of the uveal tract.
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iris
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What is the ring of tissue that extends from the choroids of the front of the eye to the lens? And what does each component do?
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Ciliary body
Muscular- adjusting the refractive power of the lens Vascular (ciliary process)- produces the fluid that fills the front of the eye |
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What are the inner layers of the eye?
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retina, lens, anterior chamber, posterior chamber, and vitreous humor
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What part of the inner eye contains the light sensitive neurons and transmits the visual signals to central targets? It is part of the CNS
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retina
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What part of the inner layer of the eye contains the refractive power of the eye?
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lens
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What part of the inner layer of the eye is located btwn the lens and cornea, it is filled with aqueous humor that supplies nutrients to these structures?
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anterior chamber
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What part of the inner layer of the eye is located between the lens and the iris and contains the ciliary processes that make the aqueous humor?
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posterior chamber
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What part of the inner layer of the eye is made of a gelatinous substance that contains phagocytic cells that clear the debris from the eye? It also accounts for 80% if the volume of the eye.
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vitreous humor
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What must the lens look like to view distant objects?
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thin and flat and has the least refractive power
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To view close objects how does the lens change?
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It becomes thick and round with a strong refractive power
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What are the radially arrange CT bands that hold the lens in place and are attached to the ciliary m?
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zonule fibers
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Name an inhibitory NT
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glycine
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Name a protein that is involved in endocytotic budding of vesicles in the presynaptic terminal of neurons?
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clathrin
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Describe ionotropic GABA R.
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inhibitory, associated w/ Cl- ion channels, and have binding site of barbituates and steriods
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Describe NMDA glutamate R.
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allow entry of Ca++ as wells as Na+ and K+, requires presence of coagonist (glycine), and is blocked by Mg++ at hyperpolarized voltages
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By what mechanism does muscle length influence muscle tension?
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degree of actin to myosin filament overlap
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What affect does contraction of the ciliary muscles have on lens thickness?
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increases; leads to decreased tension on the zonules fibers, increases the refractive power to focus on close objects
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What leads to closure of the Na channels in the outer segment mb of the rod during light stimulation?
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decrease in cGMP conc
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in the retina, off-center bipolar cells have Rs for what NT?
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glutamate
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What are the 2 vibration sensing mechanoreceptors and which detects low frequency vibrations?
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Meissner's
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Stimulation of what 2 brain regions can produce analgesia?
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periaqueductal gray matter and rostral medulla
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How do aa move into most cells?
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Na co-transport
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Narrowing the pupil reduces both
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spherical and chromatic aberration
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Reducing the size of the pupil also ____ the depth of the field
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increases
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An adjustable pupil therefore provides an effective means of
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reducing optical aberrations while maximizing depth of the field to the extent that different levels of illumination permit
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What controls the innervation of the pupil?
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sympathetic and parasympathetic divisions of the visceral motor system
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normal eye where images are focused precisely on the retina and vision is perfect
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emmetropia
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corneal surface is too curved or eyeball is too long. When lens is as flat as possible, the image of distant objects focuses in front of the retina. nearsighted
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myopia
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eyeball being too short or the refracting system is too weak; focuses at some point behind it
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hyperopia
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What are the layers of the retina?
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nerve fiber layer, ganglion cell layer, inner plexiform layer, inner nuclear layer, outer plexiform layer, outer nuclear layer, photoreceptor layer, and pigment epithelium
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What are the 5 types of neurons in the eye?
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photoreceptors, bipolar cells, ganglion cells, horizontal cells, amacrine cells
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Where are the cell bodies of the eye neurons located?
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inner nuclear, outer nuclear, and ganglion cell layers
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Where are the processes and synaptic contacts?
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inner and outer plexiform layers
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What is the 3 neuron chain?
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photoreceptor to bipolar cell to ganglion cell
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photoreceptor contact what 2 cells?
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bipolar and horizontal
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Where are the cell bodies of the rods and cones?
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outer nuclear layer
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Where are the cell bodies of the bipolar cells?
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inner nuclear layer
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Where is the synapses between the bipolar cells and the photoreceptors
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outer plexiform layer
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Where do the bipolar cells synapse with the ganglion cells?
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inner plexiform layer
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Where are the horizontal and amacrine cells located?
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inner nuclear layer; responsible for lateral interactions
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What regulates the opening/closing of channels?
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cGMP
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Darkness causes
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high levels of cGMP to keep channels open
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Light causes
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reduced levels of cGMP, closes channels which leads to hyperpolarization and then the reduction of NT release at the photoreceptor synapse
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What is the photopigment in rods
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rhodopsin
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Describe rods.
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low spatial resolution (b/c of conversion), sensitive to light, produce a reliable response to a single photon of light, multiple rods contact a rod bipolar cell; mutltiple rod bipolar cells contact an amacrine cell
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What is vision where only rods are activated?
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scotopic vision (below -4)
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Describe cone system.
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high spatial resolution, see color, illumination increases, cone activity increases, more than 100 photons of light are required to produce a reliable response in a cone, better at adapting to operate over a range of luminance values; one to one relationship to maximize acuity
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What is it called when cones are the only activated photoreceptors?
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photopic vision (above 0)
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What happens when cone fxn is lost?
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legally blind
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What is the cone threshold?
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-4
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When does rod saturation begin?
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0
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Range of mesopic vision
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(-4 to 0)
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Are there more rods or cones in the retina?
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rods
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what is a highly specialized region of the central retina that contains the greatest density of cones?
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fovea
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What happens to the diameter of the foveal cones?
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becomes more like rods
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What is the foveola?
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center part of the fovea; totally rod free
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How is the threshold for detecting a light stimulus affected outside of the region of central vision?
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it is lower
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What is the trichromatic theory?
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The 3 different types of cones each have a sensitivity for a specific wavelength of light (blue- short, green-medium, and red-long)
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What is the form of color blindness called in which an individual can only perceive 2 colors? It is recessive sex linked characterisitc.
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dichromacy
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What are the two forms of dichromacy and describe them?
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protanopia- green and blue cones
deuteranopia- blue and red |
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What are the two types of color deficiencies?
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anomalous trichromats
protanomalous trichromats (require more red) and deuteranomalous trichromats (more green) |
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What is the ratio of oncenter to offcenter ganglion cells?
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equal
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What effect does turning on light in the center of an on center ganglion receptive field cause
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burst of AP
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What effect does light have on an offcenter ganglion cell receptive field?
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reduces the rate of discharge until the light is turned off at which time the cell responds with a burst of AP
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Changes in light intensity (both increase and deacrease) cause
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increased # of APs
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What types of potentials do bipolar cells have?
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graded
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What types of R do off-center bipolar cell have?
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AMPA and kainite ionotropic that depolarize in response to glutamate
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What type of R do on center bipolar cells have?
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G protein coupled metabotropic glutamate R (mGluR6) which close cGMP channels, reducing inward current and hyperpolarizing the cell
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What is sign conserving and what cells elicit this?
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change in mb potential of the bipolar cells is the same as the photoR; off-center bipolar cells
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What is sign inverting and what cells elicit this?
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change in mb potential of the bipolar cell is opposite of the photoR; on-center bipolar cells
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