Physio Ch. 8, Neurons

hrdcorhrvivor's version from 2017-03-07 08:11

Section 1

Question Answer
The CNS containsbrain and spinal cord
The PNS containssomatic ns, enteric ns, autonomic ns > sympathetic ns, and parasympathetic ns
SNS functionskeletal muscles
ENS functionGI tract
ANS functioncardiac and smooth muscle not associated with the ENS
SympNSfight or flight
PSNSrest and digest
dendrites functionreceive impulse
soma (cell body) functionintegrates info from dendrites
axon hillock funtionsummation of membrane potentials
axon funtioncarry away info
axon terminals functionconnect to another dendrite to synapse info
what are the three ways we can classify a neruon based on structure?multipolar, cell body connected to its dendrites. bibolar, cell body in the middle. unipolar, cell body branched off to the side of the axon
what are the three ways we can classify a neuron based on function?afferent sensory, interneuron, efferent motor
microgliaimmune cells
schwann cellproduce myelin sheath in PNS
oligodendrocyteproduce myelin sheath in CNS
ependymal cellcreate and circulate CSF
astrocytesupporting cells with multiple functions
myelin sheath differs from CNS and PNS how?CNS: produced by oligodendrocytes, appendages wrap around muliple neurons. PNS: produced by schwann cells, entire cell wraps around neuron
what is the RMP membrane potential for all living cells, roughly -70mV
equilibrium potentialthe membrane potential that exactly opposes the concentration gradient
equilibrium potential for k+concen. gradient pushes k+ out of cell, elec. gradient pulls k+ back in, -90mV
equilibrium potential for na+concen. gradient pulls na+ into cell, elec. gradient pushed na+ out of cell, 61mV

Section 2

Question Answer
depolarizationcell becomes more positive
repolarizationcell returns to RMP
hyperpolarizationcell becomes more polarized, more negative than RMP
graded potentials v action potentialsGP: brief, localized changes in membrane potential, can be depol or repol, strength has factor, summation. AP: rapid and uniform elec. signal conducted down cell membrane, all or none, do not decrease in strength
EPSPexcitatory post synaptic potential, opens non specific ion channels, greater tendency for na+ to enter cell, brings cell closer to threshold
IPSPinhibitory post synaptic potential, opens k+/cl- channel, increases k+ leaving and cl- entering, brings cell further from threshold
temporal summationgraded potential from ONE neuron occurs close together in time
spatial summationmultiple graded potentials from different neurons arrive simultaneously
action potential steps 41. reach threshold at -55 mv 2. depolarization, influx of na+ 3. repolarization, efflux of k+ 4. hyperpolarization, too much k+ left, cell too negative
how do na+ channels show a positive feedback?depol leads to opening of na+ gated channels, increase in number of na+ gated channels increased na+ cells, increase na+ further depol the cell opening more channels, p
hypokalemialess k+ than cell should have, hyperpolarizes cell, neuron is less excitable, muscle weakness
hyperkalemiamore k+ than cell should have, brings cell closer to threshold, neuron is more excitable, muscle cramps
refractory periodsnew action potential usually cannot be initiated. absolute refrac period: cannot. relative: possibly, but weak
unmyelinated fibers conduction 5 steps1. previously active area returned to RMP 2. new active area at peak of AP 3. new adjacent inactive area where depol is spreading 4. backward current doesnt reexcite area since its in refrac period 5. forward current excites new inactive area
myelinated fibers conductionsaltatory conduction, impulse jumps over sections of fiber covered w myelin, lands on nodes of ranvier
3 factors that affect conduction velocity1. axon diameter: increased diameter, decrease in resistance 2. myelination: increased myel. decreases amount of elect current (faster) 3. temperature: low temp, slow conduction
how does demyelination affect the body?slows nervous impulses, mult. sclerosis is a common dz
describe a synapseconnection between two neurons or neuron and its effector. presynaptic: neurotransmitters released from. postsynaptic: neurotrasmitters recieved. synaptic cleft: gap between them where it diffuses across
electrical v chemical synapseselectrical: passes elec. signals directly to cytoplasm via gap junctions. chemical: NT molecules carry signals, synaptic cleft present

Section 3

Question Answer
acetylcholine | effects, receptorsmuscle contractions. binds to cholinergic receptors -> nicotinic: cation channels (na+/K+) skeletal muscle and ANS. muscarinic: GPCRs linked to 2nd mess. system, smooth muscle, cardiac, & endocrine glands
norepinephrine and epinephrine | effects, receptorsamine NT activate the CNS for fight or flight. adrenergic receptors
dopamine | effects, receptorsamine NT reward motivated behavior in CNS, motor control, increase appetite
serotonin | effects, receptorsamine NT feelings of well being, happiness, blood clotting, decreased appetite
gluatmate | effects, receptorsamino acid NT primary excitatory NT in CNS, influx of cations in cell, learning and memory, synaptic plasticity
GABA | effects, receptorsamino acid NT primary inhibitory NT in CNS, influx of cl- into cell IPSP
how is a NT released? 5 steps1. AP depol axon terminal 2. depol leads to ca channels opening, ca enters cell 3. ca triggers exocytosis of synaptic vesicle contents 4. NT diffuses across synaptic cleft and binds to receptors on postsynaptic neuron 5. NT binding initiates a response in the postsynaptic cell
what are 3 ways we can terminate a NT?1. Nt can be returned to axon terminal for resuse 2. enzymes initiate NT 3. NT diffuse out of synaptic cleft
how does strength of stimulus correlate with NT release?weak stimulus releases little NT. strong stimulus causes more AP, releases more NT