PHYS20008 Lecture Notes - Lecture 3: Reversal Potential, Active Transport, Chemical Equilibrium
12 Jun 2018
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Lecture 3
PHYS20008 - HUMAN PHYSIOLOGY
LECTURE 3
MEMBRANE POTENTIAL
NERVE CELL ANATOMY
•Arborisations - tree like.
Neuron looks like a tree.
•Dendrites receive signals from
the environment. The electrical
signal travels through the axon
to the axon terminals. Axons
can be less than 1mm and up
to 1m (spinal cord).
•The human brain has a 100
billion neurons and 10
quadrillion synapses.
OSMOTIC EQUILIBRIUM
•Outside the neuron we have
heaps of Na+ and inside the
neuron we have heaps of K+.
•Ion concentration numbers
vary from cell to cell.
•Cl- is high outside and low inside and
Ca2+ has more on the outside than inside
too.
•These ions have a huge concentration
gradient, and the bigger the concentration
gradient, the stronger the drive for the ion
to push across the membrane. Ions cannot
move freely around; we need to let them.
•Eg. Na+ wants to move from the ECF
to the ICF to even out the
concentration gradient.
•E(ion) becomes E(K+) or E(Na+) etc.
ICONIC CONSTITUENTS
(TEXTBOOK VALUES)
•The force holding K+ inside the cell and
Na+ outside the cell is charge.
•A negative charge is needed to hold the K+
inside the cell; + charged ions plus - charged
environment = happy. If we have the perfect negative
charge inside the cell, that equally opposes the drive of
the ion to move out of the cell, then
we have a perfect balance between !
Document Summary
Neuron looks like a tree: dendrites receive signals from the environment. The electrical signal travels through the axon to the axon terminals. Axons can be less than 1mm and up to 1m (spinal cord): the human brain has a 100 billion neurons and 10 quadrillion synapses. Osmotic equilibrium: outside the neuron we have heaps of na+ and inside the neuron we have heaps of k+, ion concentration numbers vary from cell to cell, cl- is high outside and low inside and. Ca2+ has more on the outside than inside too: these ions have a huge concentration gradient, and the bigger the concentration gradient, the stronger the drive for the ion to push across the membrane. Ions cannot move freely around; we need to let them: eg. Na+ wants to move from the ecf to the icf to even out the concentration gradient: e(ion) becomes e(k+) or e(na+) etc. Iconic constituents (textbook values: the force holding k+ inside the cell and.
