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169 Cards in this Set

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  • Back
Which muscles are stretched by what in the knee jerk reflex?
Tapping tendon stretches quadriceps, which sends signal to spinal cord, which causes quadriceps to contract
What are intrafusal muscle fibers?
Fibers that are parts of muscle spindles
Is the trigger zone part of the muscle spindle?
No, it is after the spindle, but before the myelinated axon
How many muscle fibers are innervated by a motor neuron?
What do local potentials trigger?
Propagated potentials
What are muscles called that perform similar functions?
Heteronymous or synergistic
Describe the different local and propagated potentials in the knee jerk reflex.
Graded receptor potential on sensory neuron in muscle spindle leads to action potential (receptor potential) to graded synaptic potential on motor neuron then action potential/receptor potential, then graded synaptic potential on the muscle then action potential/receptor potential
How do local potential convey information?
In their amplitude and duration
How do action potential convey information?
In their number and timing
How are action potential recorded?
Glass capillary microelectrode; tip is so thin that it can penetrate a neuron's membrane, allowing measurement o f the electrical potential across the membrane
What is the receptor potential?
The synaptic potential that determines whether or not the signal is propagated; technically, receptor potential is the first one, (such as on the muscle fiber) and synaptic potential is on every neuron from there on out
How is the antagonistic muscle keep from flexing during the stretch reflex?
Sensory neuron also synapses on inhibitory neuron, preventing flexor motor neuron from firing
What are the flexor muscles that are inhibited during the stretch reflex?
What is an abnormally weak reflex called and what is it a problem with?
Hyporeflexia ; problem with muscle, spond, motor or senssory axon
What is an abnormally strong reflex called and what is it a problem with?
Hyperflexia; problem with uppe rmotor neuorn
What is the difference between the dorsal and the ventral horn?
Dorsal is where afferet sensory comes in; ventral is where motor efferent neuron goes out
What is in gray matter and what is in white matter?
Gray: cell bodies and dendrites
White matter: myelinated axons
What are dorsal root ganglia?
BUndles of sensory axons that joing together before entering the dorsal horn
What are ventral roots?
Bundles of motor axons that join together to exit the ventral horny
WHat are lumbar and sacral?
Towards the head and bottom respectively
Describe the segmental arrangement of the spinal cord.
Cervical: neck and arms (8 segments)
Thoracic: trunk (12 segments)
Lumbar: legs (5 segments)
Sacral: lower back , genitals (5 segments)
Describe the difference between somatic versus autonomic relays in the nervous system.
- Somatic are direct relays from central nervous system to skeletal muscle
- Central nervous system sendmessage along preganglionic fiber to autonomic ganglion, which relay messages along postganlionic fiber to glands, organs, and smooth muscle
What are 3 differences between sympathetic and parasympathetic divisions?
1. Location of ganglia: In sympathetic, ganglia are far from target and postganglionic fiber is long; in parasympathetic, ganglia is close to target and postganglionic fiber is short
2. Segmental origin of preganglionics: Sympathetic are in thoraci and lumbar; parasympathetic are in cranial and sacral
3. Nuerotransmitter: Sympathetic release norempinephrine and parasymapthetic release acetylcholine
What are 7 evolutionary origns of hte CNS?
1. Sensory/respond
2. Sepcailized cells
3. Neurons (such as hydra, jellyfish, & starfish)
4. Centralization: bringing neurons together in middle of animal to interactin, such as flatworm and planaria
5. Segmentation: assembling rest of neurosn into groups to control corresponding poarts of obyd, such as roundworms
6. Cephalization: putting a lot of neurons at the front of animal, such as roundworms, insects
7. Brain
What gives rise to the peripheral nervous system (autonomic and sensory)?
Neural crest
What are altneraitve names for forebrain, midebrain, and hindbrain?
Forebrain: prosencephalon
Midbrain: mesencephalon
Hindbrain: Rhombencephalon
What end of hte neural tub eexpands disproportinately during cephalization?
Teh rostarl portion
What are the medulla and pons responsible for?
Respiration, circulation, posture, and other "maintenance" functions
What is the cerebellum responsible for?
Muscle and reflex coordination
What isht emidbrain responsible for?
Auditory and visual centers, especially "unconscious" vision, such as oculomotor reflexes, motion sensitivie, and startle responses
What is the hypothalamus responsible for?
Unconscious drives
What are the medulla, pons, cerebellu,m midbrain, hypothalamus, and pituitary gland connected by?
Cranial nerves
Which cranial nerves go to extraocular muscles?
Oculomotor and Trochlear
Which cranial nerves go o the heart?
What does hte basal gangalia?
Initiate and execute movement
What did K.Brodmann do?
German neurologist whose anatomical study revelaed differences in neuron shape, size, and arrangement among different areas of the brain; some sharp boundaries and differences among layers within areas
What did Karl Lashley do?
Trained rats to perform tasks then surgically removed or damaged particular portions for their cerebral cortex then tested their memory; that behavior declined gradually with amount removed, but it didn't matter much which parts were removed; led him to propose the Laws of Equipotentiality and Mass Action
What did Charels Brown-Sequard do?
French neurologist who took note of ability of people to recover considerable function after brian lesions, suggested specific mental abilities broadly disturbed in the brain
Which two people did experiments that countered the theory of localization?
Karl Lashley and Cahrels Brown-Sequard
WHat did Wilder Penfield odo/
Proposed "homunculus" based on local stimulation during surgery for intractable epilepsy; led to distinct sensations, movements and even memories
What are 5 ways to detemrine function f specific brain areas?
1. Lesions studies
2. Direct stimulation
3. fMRI or PET scanning
4. Recording form neurons with a microelectrode
5. Multi-unit recording: recording hundreds/thousands of neurons at a time
What did Luigi Galvani do?
Formed field of "electrophysiology"
How thick is the lipid bilayer?
6-8 nm
What is another name for passive diffusion?
Brownan influex
WHat are 3 differences between electricity in nervosu ssytem vs. electricity in wires?
1. Ions in nervous system rather than electrons
2. Current flows mainly across membranes rather than down wires
4. Electrical signaling in nervous system is related to changes in the membrane potential
Why can K+ enter the cell but not Na+ even though K+ is larger?
K+ has fewer bound water molecules due to its less localized charge field
What is the diffference between the concentrations inside and outside of the cell?
Same constituents, but the outside is 20 times more diluted than the inside
Describe the balancing of K+.
K+ selective chanels are impermeable to anions, so K+ leaves the cell to flow down its concentraton gradient; the inside gets a net negative charge which increase dramaticlaly as K+ ions flow out until concentration gradient is ocounterbalanced by K+ attracted to teh isnide by the electrical gradient
When is equilibrium for an ion reached?
when its concentration gradient and the electrical gradient are equal and opposite
What would be eht efect of the translocation of about 60,000 K+ out of a 50 um diameter cel?
Drop the membrane potential 100mV
What is the total number of K+ ions inside a typical cell?
About 36 billion
Write the Nerst Equation?
Eion = TF/zF ln[Cout]/[Cin] = 60 mV log [Cout]/[Cin]
What are the outside/inside and equilibrium potentials for K+, Cl-, Na+, and Ca2+?
Out/In/Eq. Pot.
K+ = 5 mM/100 mM/-80mV
Cl- = 150 mM/13 mM/-65 mV
Na+ = 150 mM/15 mM/62 mV
Ca2+ = 2 mM/0.0002 mM/123 mV
What is the slope of the graph plotting membrane potential against log scale?
60 mV/10fold change in Ko
Describe the GHK Equation for gliagl cells.
The permeability to Na+ and Cl- is negligible, so the equation reduces to Nerst
What is the GHK equation?
Used to determine the resting potential in a neuron

RT/F ln (PK[Kout] + PNa[Naout] + PCl[Clout])/(PK[Kin] + PNa[Nain] + PCl[Clin])
What is the Nerst Equation for the membrane potential of a specific ion?
Eion = RT/zF ln[Cout]/[Cin]

z = valence of ion
F = Faraday constant
Describe the GHK Equation.
In glial cells, the permeabilities of Na+ and Cl- are negligible, so the equation reduces to Nerst
what are the permeabilities for Pk :PNa:PCl
What happens to the permeability to Na+ if the permeability to K+ suddenly decreases.
The permeability to Na suddenly increases
What would happen if the pearmeability to Cl- increased?
Cell would be clamped at a negative membrane potential ~ lead to an inhibitory response
What is the difference between the Nerst poetnial and the GHK potential?
Nerst reaches eqilibrium; GHK reaches steady state, but not an eqilibrium condition
What is 70% of all energy consumption in the brain used for?
Used to pump Na+ out and K+ back into neurons
What does it mean for hte sodium potassium pump to be electrogenic?
Sends 3 Na+ out for 2K+ in ~ maintains the negative c oncentration gradient
What is the formula for the ionic current?
Ik = gK (Vmemb - Ek)

Electrical "driving force" is hte difference between the membrane potential (Vmemb) and the ion's equilibrium potential (Eion)
Is the Na+ channel voltage-gated?
Describe the voltage-gated Na+ channel?
Single long polypeptide, 12 times more permeable to Na than K; domains, each with 6 transmembrane alpha-helixes (S1-S6)
Which domain is voltage-sensntive in the Na+ channeL?
Describe the process from Na+ opening to de-inactivation
Depolarization opens channel and then inactivates it with a certain delay; repolarization to Vrest de-inactivates the channel & it is closed
What is tetrodotoxin?
Na+ channel blocker
What are 4 Na+ channel blockers?
Tetrodotoxin, lidocaine, saxitoxin, scorpion toxin
What is Saxitoxin?
Red tide, like TTX
How does tetrodotoxin block Na+ channel?
Blocks entry into pore from outside
How does lidocaine block Na channel?
Blocks pore from inside
How does scroption toxin block Na channel?
Blocks inactivation step
How many genes code for voltage-gated sodium, calcium, and potassium channels respectively?
9, 21, and 78
What are "channelopathies?"
New congenital diseases associated with mutant ion selective channel genes, including certain neurological conditions with seizures and migraines
What is the difference between the relative and the absolute refractory periods?
Absolute is when falls down to lowest; relative is rises from lowest to resting
How long is an action potential duration?
2 milliseconds
What is the conduction velocity?
0.2 meters/sec ~ 120 m/s
WHat happens to axon caliber when axial resistance is decreased?
Axon caliber increases, so velocity increases
Why is it important to modify cable properties?
Changes conduction velocity & opening voltage-gated channels is the most time-consuming part of conduction, so the more distance that can be covered without channel opening, the better
What are 3 cable properties and how would they have to be altered to increase velocity?
1. Capacitance (ability to hold a charge) - decreasing capacitance would increase speed of conduction
2. Membrane resistance - increasing membrane resistance would increase speed of conduction
3. Internal resistance - decreasing internal resistance would increase conduction
What two cable properties does myelin effect?
Decreases capacitance and increases membrane resistance
Where along the axon does the action potential "recharge?"
Along the nodes of ranvier, which are not covered by myelin; that is where Na+ channels are concentrated
Where are K+ channels concentrated?
Along internodes
What are 3 types of synapses?
1. Chemical synapses
2. Syncytial synapses
3. Electrical synapses
Give an example of syncytial synapses.
Muscle fibers are formed by the syncitial fusion of many myoblasts
Were are electrical synapses found?
A minority of neurons; in epithelia for "metabolic cooperation"
Describe electrical synapses
Gap junction bridged by connexons
What are the protein subunits of connexons called?
Can molecules enter gap junction?
Yes; permeable to molecules with a MW <1000
How wide is the synaptic cleft in chemical synapse?
About 20 nanometers wide
Why did the proof that transmission across chemical synapses is chemical await electron microscopy?
Light microscopes cannot distinguish objects closer than about 200 nanometer apart
What are Schwann cells?
Cap nerve terminal & provide myelin in PNS
What are oligodendrocytes
Provide myelin in the CNS
What are astrocytes?
Space filler
What is the difference between the active zone of excitatory vs. inhibitory synapses?
Excitatory: large active zone
Inhibitory: small active zone
What are Type 1 and Type II cells?
Type 1: Excitatory
Type II: Inhibitory
What is the difference between presynaptic dense projections on Type I vs. Type II cells?
Type I: Prominent presynaptic dense projections
Type II: Less obvious presynaptic dense projections
What are the 4 hypothesis of neurotransmitter release?
1. QUantal hypothesis: released in "packets" of fixed size
2. Vesicle hypothesis: synaptic vesicels rare structural basis of quanta
3. Calcium hypothesis: voltag-edependent calcium entry couples stimulation to secretoin
4. SNARE hypothesis: interaction between SNARE proteins on vesicle and on presynaptic membrane, modulated by calcium, lead to vesicle fusion
What did Bernard Katz do?
Set stage for SNARE hypothesis, which is the molecular basis of other three hypothesises
What is the end plate potential?
Excitatoyr postsynaptic potential (EPSP) at neuromuscular junctions
How mnany molecules of acetylcholine need to transfer to create end-plate potential?
What is the EPP made up of?
Many mepps (quanta) released simultaneously
What is the formula for quantal content (m)?
m = n * p
n = number of quanta available for release
p = probability that any quantum will be released upon stimulation
If a perturbation affects quantal number, is the effect likely to be presynaptic or postsynaptic?
What does bungarotoxin do?
Decreases quantal size and therefore response to transmitter
What are 3 points of evidence for the vesicel hypotehsis/
1. Numerosu vesicles in nerve terminals
2. Omega figures seen if the nerve is fixed very shortly after it is stimulated
3. Prolonged, intense stimulation leads to depletion of vesicles
How is horseradish peroxidase use?
Used as a vesicle recycling tracer
What is the main v-SNARE?
What is the main t-SNARE?
SNAP-25 and Syntaxin
What do botulinum and tetanus toxins do?
Botulin cleaves synaptobrevin (v-snare), SNAP-25, and Syntaxin
Tetanus toxins cleave Synaptobrevin
What is teh m (quantal content) proportional to?
[Ca2+]^4, so a 2 fold calcium increase leads to a 16 fold release of quantal content
What does synaptotagmin do?
Speeds vesicle release when it binds calcium
How long does it take for a transmitter to diffuse across a cleft and out of the cleft?
Across the cleft: less than 1 microseconds; out of the cleft: 1 milliseconds
How do slow synapses function?
Second messengers
How do fast synapses function?
Ligand gated, such as AChR
What is alpha bungarotoxin?
Venom component that blocks the AChR
How many ACh molecules can bind per AChR?
Describe the structure of hte AChR
5 subunits, each with 4 membrane-spanning domains; M2 domains line the pore
What are AChRs cation selective?
Due to negatively charged amino acids lining hte pore
What does the patch clamp do?
Enables an investigator to hold constant the membrane potential of a patch of membrane while current through a small number of membrane channels is measured
What does the sum of current through many AChRs comprise?
The postsynaptic response
What do TTX and alpha-BTX inhibit?
TTX inhibit AP channels; alpha-BTX inhibit AChR channels
What are defects in AChRs called?
Myasthenia gravis
What is succinyl choline?
Muscle relaxant in surgery; not cleaved easily by AChE ~ causes desensitization (keeps AChRs open)
List 4 types of glutamate receptors.
1. AMPA Receptor
2. Kainate Receptor
3. NMDA Receptor
1. G-protein coupled
What is special about NMDa Receptor?
Voltage and Ligated Gated; lets Ca++ enter during large depolarization
What are the main inhibitory neurotransmitters?
GABA "A" in the brain and Glycine in the spinal cord
What is the difference between AChR receptors and iGABA/Glycine receptors?
M2 is neutral or positively charged in GABA/Glycine receptors
What do inhibitory neurotransmitters do?
Cause gCl- to increase, drivign the cel to ECl, whichi s close to the resting potential ("shunting" - Cl- influex counterbalances Na+ influex of excitatory synapses)
What blocks glycine receptors?
What blocks GABA A receptors?
What does the blocking of inhibitory neurotransmitters cause?
Rigidity, convulsions, seizures
What are 3 agonists of inhibitory neurotransmitter receptors?
Benzodiazepines, barbiturates, alcohol
What is "hyperekplexia?"
STartle disease in which there is an exaggerated response to sitmuli, such as noise, due to small single amino acid mutationsin glycine receptor
What cations are non-NMDA receptors (AMPA & kainate) porous for?
Na & K
What cations are NMDA receptors porous for?
Na, K, and Ca
What is facilitation?
The increased size of the second of two closely-spaced synaptic potentials
What is the "residual calcium" hypothesis?
Calcium enters to trigger transmitter released, then it is quickly removed. When the second stimulus is soon after the fist, "new" calcium enters before the initial pulse is fully removed; a little can make a big difference, because quantal content is proportional to [Ca2+]^4
What is synaptic depression?
The decreased size of synaptic potential with repetitive stimulation (often at high frequency) as a result from depletion of readily released vesicles (n)
What percent of genes are for GPCRs?
10% (2000 GPCRs)
What does the binding of a ligand to the outside of a GPCR do?
Affects one of the 3 intracelluar domains (alpha, beta, and gamma). For example, alpha can split from beta and gamma, move along the membrane, interact with other proteins, and active or inactive them
What is cycli AmP?
A secon dmessenger that activates protein kinase A, which activates many proteins, including channels
What are 2 components of the versatility of GPCR signaling?
1. Amplification
2. Multiple effects: different GPCRs exert different effects ont he same enzyme
3. Subtle effects; second messengers can open or close channels, or change their voltage sensitivity or open time
4. Multiple messengers: GPCR can affect production of multiple second messegners
5. Multiple target
Who are 6 people that won nobel prizes for second messengers?
1. Sutherland
2. Fisher
3. Krebs
4. Rodbell
5. Gilman
6. reengard
Describe heterosynaptic facilitation.
Serotonin is the neurotransmitter at this axo-axonic synapse. It activates its receptor, a GPCR, leading to cyclic AMP, activating protein kinase A, inactivating potassium channel that terminates the action potential, so nerve terminal stays depolarized longer, calcium channels remain open longer, more calcium enters, and more neurotransmitter is released
What is long term pottentiation.
A burst of high frequency stimulation (sometimes called a tetanus) can lead to a long-lasting increase in the size of the EPSP, which can sometimes last last for hours and/or occur heterosynatpically; involvedi n memory
Describe the receptors involved in LTP.
2 diffrent types of glutamate receptors: activaiton of NMDA recetors leads to influx of enough calcium to activate enzymes that in turn lead to insertion of more AMPaA receptors, thereby increasing the EPSP size
What is habituation due to?
Synaptic depression
What is sensitizioant due to?
Heterosynaptic facilitation
Describe acetylcholine metabolism
Synthesized from choline and acetyl CoA by cholin acetyltransferase (ChAT), packaged into vesicles by a transporter, released, interacts with receptors, brokwn down to choline and acetate by acetylcholinesterase (AChE), loaded by into cell by cholin transporter
What does tensilon doe?
Serves as acetylcholinesterase inhibitor to treat myasthenia gravis
What inhibits acetylcholinesterase?
Tensilon, organophosphate insecticides, nerve gas
What amino acid isGABA made from?
What amino acid are norepinephrine and dopamine made of?
What amino acid is serotnin made of?
Waht does L-DOPA do?
Increases synthesis of DA
What does do amphetamine and tyramide do?
Stimulation of release of DA at nerve terminal
What does parglyine do?
Inhibit breakdown of dopamine
What does ritaline do?
Inhibits reuptake of DA
What do cocaine, amphetamine, and benztropine do?
Inhibit reuptake of DA
What does SSRI Antidepressants (Paxil, prozac, Zoloft, and celexa) do?
Inhibit reuptake of seratonin
What are SSRI Antidepressants that inbit the reuptake of 5HT?
Paxil, prozac, Zoloft, celeza
What do hallucinogens do?
Stimulate serotonin receptors ars partial agonist
Describe opiate receptors.
GCRs in the brain
What are 4 opiates.
Heroin, morphine, codeine, enkephalins
What is hypocretin involved in?