Chapter 3 - The neuronal membrane at rest Flashcards
What is the resting membrane potential?
The negative charge in the cytosol of an excitable membrane.
What are cations?
Ions with a net positive charge.
In the brain the most importants ones are Na+ (sodium) K+ (potassium), Ca2+ (calcium)
What are anions?
Ions with a net negative charge,
Most important in brain Cl- (chloride)
What is the phosholipid bilayer?
The neuronal membrane consists of two layers two molecules thick. The molecules outward and inward facing sides are hydrophilic (water loving) and the inner layer hydrophobic. This isolates the neuron from the extracellular fluid.
What are proteins assembled of?
A combination of 20 different amino acids.
What is an amino acid?
A molecule with a central carbon atom which covalently bonds to four molecular groups: a hydrogen atom, an amino group (NH3+), a carboxyl group (COO-) and a variable group called the R group. (R stands for residue)
The differences between different amino acids result from differences in the structure of the R group.
What are ion channels?
Channels on the neuronal membrane which can open up and close. This enables the neuronal membrane to let in and out ions from the extracellular fluid allowing potential difference.
What are ion pumps?
Ion pumps are enzymes which can utilize energy released by the breakdown of ATP to transport certain ions across the membrane.
What are the two factors influencing ionic movement through ion channels?
Diffusion and electricity.
What is diffusion?
The evening out of fluids with different concentrations.
What is a typical resting potential of a neuron?
About -65mV
What is depolarization of the membrane?
The increase of electric charge of the neuron from it’s normal resting value.
Why is water important for the resting potential?
It has an uneven distribution of electrical charge. The covalent bonds mean they share electrons. However, the oxygen atom has a greater affinity for electrons, and they spend more time with oxygen, making the hydrogen net positively charged and the electron net negatively charged. Thus, H2O is a polar molecule, held together by polar covalent bonds.
This makes water an effective solvent of other charged or polar molecules: other polar molecules tend to dissolve in water.
