Quiz 1 Flashcards
(64 cards)
0
Q
2 Types of Synapses:
A
- chemical synapse- NTs stimulate receptors that produce an electrical current flow
- electrical synapse- gap junctions, direct flow of current from one neuron to another
1
Q
Dendrite/Axon is presynaptic & Dendrite/Axon is postsynaptic?
A
Axon is presynaptic
Dendrite is postsynaptic
2
Q
Brainstem structures that connect forebrain to spinal cord & Brainstem controls what?
A
- midbrain
- pons
- medulla
- brainstem control respiration, HR, BP
3
Q
White Matter vs. Gray Matter
A
White Matter - inside (brain), outside (spinal cord), contains axons that carry signals to and from the cortex
Gray Matter - outside (brain), inside (spinal cord), cell bodies and glial cells
4
Q
Primary Motor Cortex vs. Primary Somatosensory Cortex
A
PMC- precentral gyrus, controls movement of opposite side of body
PSC- postcentral gyrus, controls sensation from opposite side of body
5
Q
Corticospinal Tract
A
- most important motor path from PMC to spinal cord
- pyramidal decussation- crossing of pyramidal tract at jxn of medulla and spinal cord
6
Q
Posterior Column Sensory Pathway & Spinothalamic Sensory Pathway
A
Posterior Column Sensory Pathway- senses vibration & joint position
Spinothalamic Sensory Pathway- sense pain & temperature
7
Q
Arteries & Veins supplying brain
A
- Internal Carotids: anterior blood supply
- Vertebral Arteries: form basilar artery, posterior blood supply
- Arteries combine to form Circle of Willis
- Veins: internal jugular veins
8
Q
Resting Membrane Potential
A
-40 to -90mV determined by K+
9
Q
3 Types of Potentials:
A
- receptor- change in RMP when triggered
- synaptic- NT’s change RMP
- action- electrical signals across individual neurons are propagated
10
Q
Amplitude and Intensity of AP
A
- amplitude independent of magnitude of AP
- intensity causes increased frequency of AP
11
Q
All or None Principle
A
once threshold is reached the AP is triggered and can propagated
12
Q
Ion Movements to Produce Electrical Signal- Na+, K+, Ca2+, Cl-
A
intracellular ion= K+ (wants to move outside causing - RMP)
extracellular ion = Na+
ion channels: ions diffuse via con’t gradient passively; transmembrane proteins provide selective permeability to specific ion
active transporters: require energy to move ions against con’t gradient; maintain ion gradients
13
Q
EQUATIONS*
A
Understand variables and purpose of equation
14
Q
Ionic Basic of AP/Environment
A
- AP occurs because the neuronal membrane becomes temporarily permeable to Na+
- increased depolarization with increased Na+ available in the environment
15
Q
When are K+ and Na+ involved in AP? Drugs that block the ions?
A
early involvement= Na+
delayed involvement= K+
tetradotoxin blocks Na+
tetraethylammonium blocks K+
16
Q
3 Conclusions from Voltage Clamp Studies:
A
- activation of Na+ conductance
- activation of K+ conductance
- inactivation of Na+ conductance
17
Q
Refractory Period
A
- due to hyperpolarization because slow to turn off K+ and persistence of Na+ inactivation; unable to produce AP
- allows for forward polarized propagation of AP
18
Q
Positive Feedback ion and Negative Feedback ion
A
Positive Feedback: Na+ because of passive leakage to surrounding areas further down membrane
Negative Feedback: K+
19
Q
To increase conduction velocity (time required for electrical signals to travel the neuron)…
A
- increase the diameter to decrease resistance
- insulate/myelinate to decrease leakage
20
Q
Formation of Electrical Impulses require:
A
- conc’t gradients to exist for ions
2. neuronal membranes can rapidly change permeability to selective ions
21
Q
Hodgkin & Huxley postulated that to form a AP, nerve cells have channels that:
A
- allow fast ion flow
- voltage sensitive
- use electrochemical gradient established for ions
- selective for specific ions
22
Q
Diversity of Ion Channels:
A
- over 100 ion channel genes have been discovered
- different splicing of coding regions
- modification of RNA
- post translational modification
- combination of different subunits
23
Q
4 Different Types of Ion Channels
A
- voltage gated
- chemical
- mechanical
- temperature
24
Voltage Gated Ion Channels
- selectively permeable to specific ions: K, Na, Ca, Cl
- 10 different Na channel genes
- 10 different Ca channel genes
- nearly 100 different K channel genes
25
Ligand Gated Ion Channel
- less selective, allow for 2 or more ion types through
- 2 types: NT stimulated OR detection of chemical signals w/in cytoplasm (main fxn is to convert chemical signals within cell into electrical info, ligand binding domain is intracellular, found often w/ sensory stimuli)
26
Stretch & Heat Activated Channels
Heat- detect pain & temp, mediate inflammation, detect specific temp ranges
Stretch- respond to changes in membrane shape, basis of stretch reflex, hearing
27
Membrane proteins with structures that allow:
1. selective ion conduction
2. sensing of transmembrane potential to activate or inactivate
3. binding sites for neurotoxins
28
General Transmembrane Architecture common to all major ion channel families:
1. membrane proteins cross membrane repeatedly
2. can have accessory proteins (called beta subunits) that help regulate channel function
3. most voltage gated channels have transmembrane helix with positively charge amino acids that sense voltage changes across the membrane
29
Properties of Active Transporters
- form complexes with specific ions
- move ions against their conc't gradient
- require energy
- work slower than ion channels
30
2 Classes of Active Transporters
1. ATPase Pump: energy via hydrolysis of ATP (ex:Na/K ATPase pump)
2. Gradient Users: form energy via use of electrochemical gradients, ion exchangers (Na/Ca or Na/H), cotransporters carry multiple ions in same direction (Na/K/Cl)
31
Na/K ATPase Pump
- large integral membrane protein with alpha and beta subunits
- binds Na and hydrolyzes ATP to transform shape --> release Na on other side of membrane and bind K --> release Pi and transform shape --> release K on other side of membrane
- binds ouabain = toxin
32
Electrical Synapses
- less transmissions occur this way
- passive flow of current from one neuron to another (bidirectional)
- FAST without delay
- Purpose: sync electrical activity among many neurons
33
Chemical Synapses
- SLOW transmission
- unidirectional
- involves NTs and a much more complicated system
34
3 Part Definition of NTs:
1. must be present w/in presynaptic neuron
2. must be released in response to presynaptic depolarization and must be Ca2+ dependent
3. must have postsynaptic cell receptors
35
2 Ways NTs get to Presynaptic Terminal:
1. Small molecular NTs are formed w/in presynaptic terminal
| 2. Neuropeptides are synthesized in cell body and then transported to presynaptic terminal
36
3 Ways NTs are removed:
1. reuptake
2. enzymatic breakdown
3. combo
37
Quantal Release of NTs: End Plates and End Plate Potentials
End Plate: site where presynaptic axons stimulate the muscle fiber
End Plate Potential: the change in membrane potential at the end plate
-if EPP is larger enough, an AP is produced and muscle contracts
38
Synaptic Vesicle Cycling: NT Release
1. synapsin binds to vesicle to hold vesicle in place
2. phosphorylation of synapsin by protein kinases allows synapsin to dissociate from vesicle freeing them to move
3. vesicles prepared for release by variety of proteins that work to align vesicle in presynaptic membrane for fusion
4. synaptotagmin binds Ca2+ and fuses vesicle with presynaptic membrane & release NTs
5. vesicle membrane retrieved from presynaptic membrane and recycled
39
Vesicle Membrane Retrieval
1. clathrin attaches to vesicle membrane
2. clathrin triskelia attachment causes membrane to curve
3. dynamin pinches off the membrane
4. clathrin coats are removed
40
NT Receptors
1. ligand gated ion channels (ionotropic)- rapid response
2. metabotropic receptors (G protein coupled)- slow response
- one transmitter can activate both types
41
Post Synaptic Current (PSC), Post Synaptic Potential (PSP), Excitatory Post Synaptic Potentials (EPSPs), Inhibitory Post Synaptic Potentials (IPSPs)
PSC- electrical current formed by opening or closing ion channels
PSP- change in membrane potential due to PSC
EPSP- increase chance of AP, depolarizes
IPSP- decrease chance of AP, hyperpolarizing or depolarizing but keep potential away from threshold
42
EPC will have ______ current at potentials more negative than Erev because the electrochemical driving force is negative
inward current = more negative Erev
43
EPC will have an ________ current at potentials more positive than Erev because the electrochemical driving force is reversed
positive current = more positive than Erev
44
2 Categories of NTs and name the main inhibitory and excitatory NT
2 NTs: neuropeptides (made of amino acids), small molecule (individual amino acids, biogenic amines)
main excitatory = glutamate
main inhibitory = GABA
45
Acetylcholine (NT): locations of function
- NMJ
- vagus nerve to cardiac fibers
- synapses of ganglia of visceral motor system
- CNS
46
Ach Synthesis: precursors, enzymes, receptors
Precursors: acetyl coenzymeA + choline
Enzymes: CAT, VAchT (packaging), AchE (breaks down Ach, insectisides and sarin block AchE causing paralysis)
Receptors: nicotinic, muscarinic
47
Nicotinic vs. Muscarinic Receptors
Nicotinic: nAchR
-nonselective ionotropic/ligand gated channel (FAST)
-huge protein complex that spans membrane: extracellular portion, large membrane spanning portion
Muscarinic: mAchR
-metabotropic receptor (SLOW)
-7 membrane helical spanning segments (G-protein coupling)
-antagonists- atropine, scopolamine, ipratropium
48
Glutamate (NT)
- important for normal processes, brain trauma increases glutamate and can cause excitotoxic brain damage
- nonessential AA
- can't cross BBB unless broken down into precursors glutamine & glucose
- packaged into vesicles by VGLuT
- removed from synapse by EAAT (Na+ dependent)
- glutamate glutamine cycle: maintains environment and adequate glutamate supplies, terminates glutamate action at postsynaptic area
49
Glutamate Receptors
1. AMPA- ionotropic, excitatory
2. NMDA- ionotropic, excitatory
3. kainate- not well defined
4. mGluR- metabotropic glutamate receptor (G-protein coupling, slow and longer lasting response)
50
NMDA glutamate receptor
- pores to allow Ca2+, K+, Na+ through
- increase Ca2+ concentration in postsynaptic neuron = increased excitation
- can be blocked my Mg2+, happens at hyperpolarized states
- glutamate binds to NMDA to force Mg2+ out to cause depolarization and open up channel
- subunits: Glu 2 (glutamate), Glu1/3 (glycine)
51
AMPA glutamate receptor
- clam shell shaped Y
| - glutamate binds to shut clam shell and open pore
52
Histamine (location, type R, fxn)
- found in neurons in hypothalamus
- metabotropic receptors
- controls reactivity of vestibular system, vasodilates, part of inflammatory response
53
NE/Epi (location, type R, fxn)
- formed in medulla, produced at ends of sympathetic nerve fibers
- metabotropic receptor
- fight or flight response
54
Dopamine (location, type R, fxn)
- found in corpus striatum
- metabotropic receptors
- motivation, addiction, love, emotion, reinforcement
55
Glycine (location, type R, fxn)
- found in spinal cord, brain stem, retina
- ionotropic receptors
- causes IPSP
56
GABA (location, type R, fxn)
- found in brain/spinal cord
- GABAa & GABAc are ionotropic, GABAb is metabotropic
- inhibitory, regulate muscle tone
57
Serotonin (location, type R, fxn)
- pons and upper brainstem
- ionotropic receptors
- excitatory, regulates sleep and wakefulness
58
ATP (location, type R, fxn)
- CNS, dorsal horns
- ionotropic receptors
- cotransmitter, elicit electrical response in neuron
59
Endorphins (location, type R, fxn)
- pituitary gland
- metabotropic receptors
- inhibit transmission of pain signals, euphoria
60
Endocannabiroids (location, type R, fxn)
- brain (hippocampus, cerebellum)
- metabotropic receptors
- inhibitory
61
Substance P (location, type R, fxn)
- hippocampus, neocortex, GI tract, spinal cord
- ionotropic receptors
- transmit pain info to CNS, involved in inflammatory response
62
Functional Recovery
- circuits w/in brain that retain some plasticity and able to make some changes (horizontal spreading/connections between a lot of neurons)
- regain function --> cortical areas/involvement decline
63
Repair in PNS vs CNS
PNS- growth and stimulation of axonal growth
CNS- no capability of CNS to fully regenerate, glial scarring causes support cells to regenerate/proliferate which inhibit axon growth
Exception: olfactory neurons can regenerate, olfactory neurons and hippocampus have neural stem cells
