Lecture 3 Flashcards
sensory stimulus
activation of cutaneous mechanoreceptors by skin deformation
neural code
action potential, post-synaptic potential
interpretation/action
flexor withdrawal reflec
extracellular and cytosolic fluid
-neurons are in an extracellular milieu that is water-based
-ions: atoms or molecules with a net electrical charge
the concentration gradient is the product of:
- the imermeability of the plasma membrane to the movement of ions
- the presence of proteins that maintain actively the gradient of concentration
- the presence of proteins that allow ions to passively cross the membrane (into or out of the cell)
ion channels
control of resting and action potentials
receptors-channels
neurotransmitters and post-synaptic potentials
metabotropic receptors
neurotransmitters and neuromodulators
ion pumps
-producers of electrochemical gradients
-formed by transmembrane proteins
-catalyze ATP for energy (active transport)
-push ions against the concentration gradient (from more diluted to concentrated)
-produces the ion concentration gradients (neuronal signaling)
proteins-channels
-voltage dependent
-polar R groups
-non polar R groups
-transmembrane domains
-ion selectivity
-mechanism of activation (gating)
Na/K ATPase ion exchange pump
-catalyze ATP into ADP
-drives 3 Na+ out, brings 2 K+ in
-forms a concentration gradient of more Na outside and more K inside
K+ equilibrium potential
-80mV
Na+ equilibrium potential
62mV
Ca2+ equilibrium potential
123mV
Cl- equilibrium potential
-65mV
diffusion
-dissolved ions redistribute in a homogenous manner
-ions diffuse along their concentration gradient when the channels are permeables to ions and there is a concentration gradient across the membrane
electrical potential (V)
-pressure exerted on ions
-influences the movement of ions
electric current (I)
movement of ions according to Ohm’s law:
V=R x I or I=V x G
electric conductance (G)
= ease by which I can flow through
resistance (R)
capacity to block I
R=1/G
equilibrium potential
-each ion has a potential at which the net ionic flow is 0
-I.e. membrane potential at which the movement of the inside (i) to the outside (o) is the same as in the other direction
-difference in electrical potential that counters the diffusive force due to the concentration gradient
is the membrane potential determined solely by the concentrations of K+?
No
structure of K+ channels
-4 transmembrane subunits
-hairpin pore endows selectivity and permeability to K+ ions
-mutations of K+ channels (hereditary neurological disorders –> epilepsy)
