Neuro 3 Flashcards
“excitable” cells
ability to propagate electrical signals over long distances in response to a stimulus
two factors that influence the membrane potential
- conc gradient (uneven distribution) of different ions across the membrane
- permeability of membrane to those ions
nernts equation
describes membrane potential if membrane were completely permeable to only one ion (equilibrium potential)
Goldman-Hodgkin-Katz equation
predicts membrane potential that results from contribution of all ions that can cross the membrane
resting membrane potential in most neurons is….
~-70mV
resting membrane potential mainly due to…
K+
- slightly from Na+
- minimally Cl-
ion movement creates….
electrical signals
what can alter membrane potential?
- change in K+ conc. gradient
- change in permeability to ions
_______________ need to move to alter the membrane potential
very few ions
_________ control ion permeability in neurons
gated channels
5 major types of ion channels
- Na+
- K+
- Ca2+
- Cl-
- monovalent cation
conductance
ease with which ions flow through a channel
mechanically gated channels
open in response to physical forces; found in sensory neurons
chemically gated ion channels
respond to ligands, including extracellular neurotransmitters and neuromodulators or intracellular signalling molecules
voltage-gated channels
respond to changes in the cells membrane potential
what are some variations in gated channels
- voltage for channel opening
- speed at which channel opens/close
- open to depolarization close during repolarization
- some spontaneously inactivate
- major channels have subtypes
channelopathies
disrupt flow, alter channel activation/inactivation, cytic fibrosis
current
flow of electrical charge carried by an ion
ohm’slaw
current flow is directly proportional to electrical potential difference between two points and inversely proportional to the resistance
two sources of resistance in a cell
- resistance of phospholipid bilayer
- internal cytoplasmic composition and size of cell
Volatage changes across membrane can be classified in what two types of electrical signals?
- graded potentials
- action potentials
graded potentials
variable strength signals that travel over short distances and lose strength as they travel and can be depolarizing or hyper polarizing
large enough depolarization (excitatory) can induce an….
action potential
action potential
very brief, large depolarizations that travel for long distances through a neuron without losing strength
