week 2 Flashcards
diff between CNS and PNS?
CNS: brain + spinal cord. receives/processes info from organs and returns info to organs w instructions on what to do.
PNS: all other neurons in body. provides communication between CNS and organs.
afferent vs efferent neurons?
- afferent: input– transmit info from organs to CNS, i.e., sensory info.
- efferent: output– transmit info from CNS to effector organs.
somatic vs autonomic
- somatic: skin and muscles, voluntary activities.
- autonomic: nerves connected to organs, involuntary activities.
key diff between neurons and glial cells
- neurons are excitable
- glial cells are support cells
define: a) soma, b) dendrites, c) axon, d) axon hillock, e) axon terminal
a) soma: body, contains nucleus/organelles
b) dendrites: receive info
c) axon: transmit APs
d) axon hillock: where axon originates and where APs are initiated
e) axon terminal: release neurotransmitters
anterograde vs retrograde transport
anterograde: moving products from soma to axon terminal.
retrograde: moving products from axon terminal to soma.
4 types of glial cells and their functions
- astrocytes: clean transmitter.
- microglia: protect CNS from foreign matter.
- oligodendrocytes (myelinate)
- schwann cells (myelinate)
why is myelin important?
- allows signal to be transmitted without much signal loss over distance.
- in other words, increases membrane resistance.
key diff between oligodendrocytes and schwann cells?
- one oligodendrocyte forms several myelin sheaths and myelinates sections of several axons (CNS).
- one schwann cell forms one myelin sheath and myelinates one section of an axon (PNS).
node of ranvier
- gaps between myelinated sections of axon
what happens when many myelin sheaths are damaged? symptoms? one solution?
- multiple sclerosis: the slowing down/blockage of signal between neurons
- symptoms: visual disturbances, muscle weakness, numbness/”pins and needles”, thinking/memory problems
- one solution: reduce leakiness by blocking potassium channels
define: a) leak channels
b) ligand-gated channels
c) voltage-gated channels
a) always open, throughout entire neuron, determine resting potential
b) open/close in response to ligand binding, at dendrites and soma, cause synaptic potentials
c) open/close in response to membrane potential changes, sodium and potassium channels are mainly in axon hillock, calcium channels mainly in axon terminal
T or F: all cells in the body generate a membrane potential, even non-excitable ones.
true
typical resting MP of neuron?
-70 mV
what 2 things do we need for a resting MP?
- concentration gradients (ion pumps)
- semi-permeable membrane (ion channels)
__% of the resting membrane potential is directly due to Na+/K+-ATPase.
this consumes ___ of the body’s energy
20%
1/3
__% of resting membrane potential is indirectly due to Na+/K+-ATPase
80%
the chemical driving force drives potassium (in or out) of the cell?
out (bc lots of K+ inside, moves from high to low)
the electrical driving force drives potassium (in or out) of the cell?
in (bc as K+ leaves, cell becomes negative and opposites attract)
when a cell reaches equilibrium, chemical and driving forces are… (2)
- opposite in direction
- equal in magnitude
in equilibrium, electrochemical force = __
0
when membrane potential = ___ mV, potassium is at equilibrium. which equation do we use to calculate this?
-94
Nernst equation
what kind of ions are inside vs outside a cell?
outside: sodium and chloride
inside: potassium and organic anions
net force = ___ force
electrochemical
the electrical driving force drives sodium (in or out) of the cell?
in
when membrane potential = ___ mV, sodium is at equilibrium. which equation do we use to calculate this?
+60mV
Nernst equation
T or F: permeability at rest is much greater for potassium than sodium
true (25-35x more)
___ maintains resting potential
sodium pump
the resting MP is closer to the potassium equilibrium potential, because ________.
at rest, the membrane is more permeable to potassium
if the membrane potential is NOT at equilibrium for an ion: (3)
- electrochemical force is NOT 0.
- net force acts to move ion across membrane in direction that favors its being at equilibrium.
- strength of net force increases the farther away membrane potential is from the equilibrium potential.
why is potassium not greatly driven to leave the cell when the cell is at rest?
-70 is somewhat close to -94… so potassium is happy
why is sodium more strongly driven to enter the cell at rest?
-70 is far from +60… further away from equilibrium = stronger forces
sodium has a small leak at rest bc __ force, __ permeability.
potassium has a small leak at rest bc __ force, __ permeability.
high, low
low, high
types of gated channels (3)
- voltage-gated
- ligand-gated
- mechanically gated (responds to pressure)
what is repolarization?
bringing closer to resting potential
describe graded potentials (3)
- short distances/decremental
- graded (varying strengths)
- spread by electronic conduction
graded potentials determine whether…
an AP will occur
define threshold, excitatory, and inhibitory
- threshold: level of depolarization necessary to elicit AP.
- excitatory: depolaroization
- inhibitory: hyperpolarization
temporal vs spatial summation
- temporal: one stimulus at different (close together) times.
- spatial: different stimuli overlapping in time.
T or F: only one summation can work at a time.
false – IRL its always a mixture of spatial and temporal summation working together.
T or F: temporal/spatial summations can add onto each other or cancel out
true
