Exam 2 (Chapter 8) Flashcards
what is apart of the central nervous system?
brain, spinal cord
what is apart of the peripheral nervous system?
nervous tissue other than brain and spinal cord
which NS are the sensory / afferent neurons and the motor /efferent neurons apart off?
PNS
what do sensory / afferent neurons do?
take info TO the CNS
what do motor / efferent neurons do?
take info from the CNS to targets
which type of neurons does the autonomic and somatic NS come from? (afferent or efferent)
motor / efferent neurons
what does the autonomic NS do?
sends signals to smooth muscle, cardiac muscle, and glands
-deals with the parasympathetic and sympathetic NS
-enteric NS
what does the somatic NS do?
sends signals to skeletal muscles
what do dendrites do?
receive incoming signals
what does the cell body do?
houses the nucleus and other organelles
-NT synthesis
what does the axon do?
carries signals away from cell body
what does the axon hillock do?
synthesize APs
what does the axon terminal do?
stores and releases NT in the somatic NS
what do varicosities do?
release NT in the autonomic NS
-NOT an axon terminal
what are collaterals?
axon branches
what is axonal transport?
how things are made that are stored in the vesicles of the axon terminal
which direction does slow axonal transport go?
anterograde direction only (unidirectional)
cell body -> axon terminal
what direction does fast axonal transport go?
anterograde and retrograde direction (bidirectional)
whats the differences between an electrical synapse and a chemical synapse?
electrical: FAST, uses gap junctions for a direct connection, displays synchronized activity
chemical: SLOW, release NT into synaptic cleft, converts AP to a neurocrine
what are multipolar neurons?
numerous dendrites, branched axon
-classified based on structure
what are pseudounipolar neurons?
only has an axon
-classified based on structure
what are bipolar neurons?
1 axon and 1 dendrite
-classified based on structure
what is an anaxonic neuron?
type of interneuron with no axon, but has dendrites
-classified based on structure
where are interneurons only found?
only found in the CNS!!
what are schwann cells?
myelinating cells of the PNS
-1:1 ratio to axons
-does synapse remodeling and repair
what are oligodendrocytes?
myelinating cell of the CNS
-1:many ratio to axons
what are satellite cells?
in the PNS
-support and protective layer around cell bodies
what are astrocytes?
in the CNS
-maintains CSF by NT uptake
-forms BBB
-releases neurotropic factors
what are microglia?
in the CNS
-phagocytic cell that removes damaged cells or foreign invaders
what are ependymal cells?
in the CNS
-epithelial cells found in the ventricles of brain
-source of neural stem cells
can a neuron be repaired if the cell body is unharmed?
yes!
-if the cell body is damaged, the cell dies
what does the Nernst equation do?
calculates an ionic equilibrium potential
-takes into account only one ion
-influenced by conc. gradient of ions & membrane permeability
what does the Goldman-Hodgkin-Katz (GHK) equation do?
predicts membrane potential
-takes into account multiple ions
-there is not a single ion that contributes to the RMP
what is conductance?
the ease by which an ion moves through a channel
-greater the electrochemical gradient = easier it flows
what are the three gated channels? what do they open due to?
mechanically gated: open due to pressure or stretch
chemically gated: open due to a ligand
voltage gated: open due to cell membrane potential change
what does Ohm’s Law say?
increase of potential gradient = faster flow
increase of resistance = slower flow
what type of potential (graded or action) is based on the strength of the input signal?
graded
what type of potential (graded or action) travels long distance?
action
what type of potential (graded or action) moves by conduction along the axon and maintains it’s uniform strength and magnitude?
action
what type of potential (graded or action) is only excitatory (depolarizing)?
action
what type of potential (graded or action) only moves Na+ and K+, instead of all four?
action
what type of potential (graded or action) uses all three types of gated channels?
graded
what type of gated channel does an action potential use?
voltage-gated ion channels
what is meant by subthreshold and suprathreshold?
refers to graded potentials reaching the trigger zone
-subthreshold: no AP
-suprathreshold: AP
what type of potential (graded or action) can summate? (multiple signals before the potential is done will sum together)
graded
what codes stimulus strength in action potentials since the strength of input signal doesn’t?
coded in frequency
-not magnitude
explain the action potential positive feedback loop?
depolarization opens more Na+ channels, the Na+ entry causes more depolarization
when is the Na+ activation gate open during an action potential?
open during depolarization
-closed during repolarization & RMP
when is the Na+ inactivation gate open during an action potential?
open during depolarization & RMP
-closed during depolarization
what is a factor of K+ channels that impacts the action potential?
they open and close very slowly
-causes the overshoot and hyperpolarization during an AP
what creates the refractory period in an AP?
inactivation and activation gates
-stops the signals from summing
what is a absolute refractory period? when does this occur?
threshold -> threshold (during depolarization and repolarization)
-no stimulus can trigger an AP until the current AP is finished
-Na+ channels need to reset
what is a relative refractory period? when does this occur?
during hyperpolarization
-some but not all Na+ channels have reset
-needs a larger than normal stimulus to generate an AP
what allows AP’s to have continuous conduction?
unmyelinated axons
-makes every region go through depolarizations & repolarizations
what factors increase the speed of an AP?
-larger diameter of an axon
-myelinated axons
-saltatory conduction (jumping b/w unmyelinated nodes)
what do neurotoxins do to APs?
block Na+ or K+ channels
what is hyperkalemia?
high K+ in the ECF
-RMP increases closer to threshold
-more excitable = needs a smaller stimulus
-more neurons firing then normal
what is hypokalemia?
low K+ in the ECF
-RMP decreases away from threshold
-less excitable = needs a larger stimulus
-less neurons firing than normal
what are the two types of neurocrine receptors? describe them
Ionotropic: receptor/ion channel, FAST
Metabotropic: GPCR (2nd mes.), SLOWER
what are the two receptor types of ACh?
Nicotinic
Muscarinic
what is a nicotinic receptor?
ionotropic
-uses Na+ to be excitatory (depolarizes)
-somatic NS
what is a muscarinic receptor?
metabotropic
-autonomic NS
what three AA’s are amines derived from?
tyrosine, tryptophan, or histdine
what are the four types of Amines?
serotonin, NE, E, and Dopamine
what AA is serotonin derived from?
tryptophan
what AA is NE & E derived from?
tyrosine
what type of receptor does NE & E use?
metabotropic receptors (alpha & beta)
-used in the autonomic NS
what AA is dopamine derived from?
tyrosine
what type of receptor do amino acids use?
ionotropic
what are the three NT are listed as amino acids?
glutamate, GABA, glycine
what subtype of receptor does glutamate use?
AMPA and NMDA receptors (ionotropic)
which amino acid NT is inhibitory?
GABA & Glycine
-uses Cl- channels (hyperpolarizes)
which amino acid NT is excitatory?
glutamate
-use Na+ to depolarizes
what type of receptor do purines use?
metabotropic
what are the three types of NT purines?
adenosine, ATP, cAMP
what type of receptor do Gases use? (NO, CO)
don’t use receptors!
-diffuse directly into the cell
what type of receptors do lipids use? what is the type of NT listed as a lipid?
metabotropic receptors
-eicosanoids
where are the two places NT synthesis occurs? what types of NT are made at each? (lg or sm)
in the cell body
-lg. NT (requires ribosomes, R. ER)
in the axon terminal
-sm. NT (ACh, amines, some purines)
what molecule is NT release dependent on?
Ca2+
explain the steps of exocytosis (NT release)
- AP depolarizes the axon terminal
- voltage gated Ca2+ channels open
- Ca2+ enters
- NT filled vesicles fuse to membrane and release NT into the synaptic cleft
- NT binds to postsynaptic receptors (vesicle becomes part of membrane)
explain the steps of the Kiss & Run pathway (NT release)
- vesicle doesn’t entirely fuse and forms a small pore
- NT is released into synaptic cleft and binds to receptor
- vesicle pulls back into the presynaptic axon terminal
- vesicle is reused
what are the three ways you can terminate NT activity?
-diffusion of NT out of synapse (due to unbound ligand)
-inactivation of NT by an enzyme (precursors are reused)
-uptake of NT by presynaptic cell or neighbor cells (glial cells, neurons)
what is divergence?
axon synapses to multiple targets (little to big)
what is convergence?
multiple axons synapses to one target (big to little)
what is synaptic plasticity?
ability of NS to change activity at synapses (more/less activity, faster/slower)
-Short Term & Long Term Facilitation/Depression
what is excitatory postsynaptic potential (EPSP)?
depolarization
-open Na+ or Ca2+ channels, close K+ channels
what is inhibitory postsynaptic potential (IPSP)?
hyperpolarization
-open K+ or Cl- channels
what types of NT can create an EPSP?
ACh (nicotinic) (Na+)
Glutamate (Na+)
what types of NT can create an IPSP?
GABA & Glycine (Cl-)
what is spatial summation?
several presynaptic axon terminals providing subthreshold signals simultaneously (multiple inputs)
-occurs at different ares on the membrane
what is temporal summation?
one input fires multiple gradient potentials in close succession
what is postsynaptic inhibition?
summed potential is below threshold = no AP
what is presynaptic inhibition?
decreases NT effect (less excited, less inhibited)
what are two ways you can do presynaptic inhibition? describe the difference between them
Global: shuts down all axon terminals
Selective: shuts down only one branch of axon terminal
what is long-term potentiation (LTP)?
enhancing what is happening at the synapse
-alters quality (speed) or quantity (NT release)
describe the steps of LTP
- glutamte binds AMPA & NMDA receptors
- Na+ enters through AMPA ion channels immediately
- depolarization of cell ejects Mg+ ion from NMDA channel and opens it
- Ca+ enters through NMDA channel
- Ca2+ activates 2nd mes. pathways in the cell
- postsynaptic cell releases a paracrine
- paracrine demonstrates retrograde feedback on presynaptic cell to increase glutamate release
during LTP, is the postsynaptic cell more or less sensitive to glutamate?
more sensitive
what is long-term depression (LTD)?
decrease in the number of receptors
-changes isoform of receptors, making it less likely to respond
what causes Parkinsons?
DA neurons are destoryed
what causes Myasthenia gravis?
antibodies are produced to destroy ACh receptors of skeletal muscles
