BIOL1008 Lecture Notes - Lecture 21: Myelin, Active Transport, Axon Hillock
Nerves and action potential
Details of Ca++ binding
TnC part of troponin binds
calcium
Troponin molecule then
rotates upwards, forcing
movement of
tropomyosin away from
binding site
Myosin head binds
Chemicals in solutions
Salts dissociate when
placed in water, so that
sodium chloride occurs
mostly as isolated sodium
and chloride
When dissociated, each
component is charged,
with sodium being
positively charged and
chloride being negatively charged
The charge is important, as water itself has partial positive and negative charges
because of the organisation of atoms
Accounts for ease of dissolving salts in water and as the conductivity of salt solutions
Charge creates potential to be a battery
Structure of water
Polar characteristic means that water molecule has partial charge
Charged because hydrogen atoms are organised on one side, so that they form
partial positive charge, while oxygen atom has partial negative charge
Composition of blood
Fluid compartments of body
Extracellular fluid
oBlood
oInterstitial fluid (bathes cells of tissues and organs)
oBladder
Intracellular fluid (fluid inside cells) (60-70-% of blood)
Red and white blood cells
Other proteins
Nutrients and non-protein nitrogenous components
Ions, especially sodium, chloride, bicarbonate, phosphate, calcium, potassium
Nervous excitation
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Synaptic transmission
Neurotransmitters- muscles, nerves, autonomic
systems
Sensory systems
Distribution of ions
Different concentrations between extracellular
and intracellular components
Potential for movement of materials from higher
to lower concentration regions
Chloride, potassium and sodium have the
possibility to move between fluids
Distribution of sodium and potassium across cell
High sodium outside and low inside
Low potassium outside and high inside
High chloride outside, low chloride inside
Inside of the cell is normally negatively charged relative to the outside (due to
proteins)
Cell membrane
Lipid bilayer
Contains proteins that allow ions or other compounds to move across membrane
Most ion movement must be through specific channels e.g. sodium only moves
through sodium channels or by sodium transporting proteins
Most cells have a lot of potassium channels, so they are the most permeable
Sodium and chloride can be pumped out through active transport
Membrane potential
Differential distribution of ions causes difference in electrical potential between
inside and outside of cell
Slightly more negative charge inside causes electrical potential across membrane to
be slightly negative compared to outside of cell
Non-excitable cells
Membrane potential= -90mV
Potassium very permeable (lots of potassium channels)
Concentration gradient causes initial net diffusion across membrane
As positive charges increase, starts repelling further potassium ion movement and
hence maintains membrane potential
No channels for sodium or chloride movement
Excitable cells (nerves, muscles and hormone producing cells)
Resting membrane potential typically -70mV
Potassium very permeable and sodium slightly permeable
Potassium diffuses outward and sodium diffuses inward
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Document Summary
Troponin molecule then rotates upwards, forcing movement of tropomyosin away from binding site. Salts dissociate when placed in water, so that sodium chloride occurs mostly as isolated sodium and chloride. When dissociated, each component is charged, with sodium being positively charged and chloride being negatively charged. The charge is important, as water itself has partial positive and negative charges because of the organisation of atoms. Accounts for ease of dissolving salts in water and as the conductivity of salt solutions. Polar characteristic means that water molecule has partial charge. Charged because hydrogen atoms are organised on one side, so that they form partial positive charge, while oxygen atom has partial negative charge. Extracellular fluid oblood ointerstitial fluid (bathes cells of tissues and organs) obladder. Intracellular fluid (fluid inside cells) (60-70-% of blood) Ions, especially sodium, chloride, bicarbonate, phosphate, calcium, potassium. Different concentrations between extracellular and intracellular components. Potential for movement of materials from higher to lower concentration regions.
