Chapter 3 Flashcards
What is silver nitrate? What does it do?
It causes 2% of brain cells to darken in color as silver chromate crystallizes inside of them, in ever nook and cranny.
What is the soma?
The cell body - where the nucleus is located
What are dendrites? What are they responsible for?
Branched, treelike extensions from the soma. They are responsible for sensing the external environment (for collecting info relevant to the cell)
What are axons? What are they responsible for?
The one and only protrusion from a neuron’s soma. It is responsible for transmitting information to downstream cells.
What are axon terminals/terminal boutons responsible for?
They are responsible for releasing neurotransmitter when there is an action potential. They release neurotransmitter onto the downstream cells that they are in contact with.
How to measure the resting membrane potential?
With glass micro pipets - filled with solutions the conduct charge. The micro pipet is inserted through the membrane into the cell.
What does the voltmeter do?
Measures the difference in electrical change between two points, the potential difference.
How is the membrane potential measured?
On a relative scale
What is the resting membrane potential in nerve and muscle?
Between -40 and -90 mV
What is an ion? What is a cation vs an anion?
Ion: charged atom/molecule
Cation: positively charged
Anion: negatively charged
What’s electrostatic pressure?
Attractive force between molecules that are oppositely charged or repulsive force between molecules that are similar charged
What are ion channels?
Specialized protein molecules that sit in the cell membrane. They have a pore (hole) in them which specific ions can enter or leave cells.
What is a leak channel?
An ion channel protein that is in the membrane and has a pore that is always open.
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What are :
Monovalent cations? Give examples.
Divalent cations? Give examples.
Negatively charged ions? Give examples.
Monovalent cations: 1 charge. Sodium (Na+) & Potassium (K+)
Divalent cations : 2 charges. Calcium (Ca^2+) & Magnesium (Mg2^+)
Monovalent anions : Chloride (Cl-)
What is intracellular fluid?
Fluid contained within cells
What is extracellular fluid?
Fluid located outside of cells
What is the charge if there is an equal amount of positively and negatively charged ions on either side of the membrane?
Outside of cell = 0mv
Inside of cell = 0 mv
What are the two proteins responsible for setting up and maintaining the resting membrane potential of neurons?
Sodium potassium transporter and leak potassium channels
What does the sodium potassium transporter need? What does it do?
- Requires ATP
- Concentrates sodium and potassium outside and inside the cell
What does the amount of leak potassium channels determine? How?
The amount of channels determine the resting membrane potential because they are always open
What is the sodium potassium pumps function?
The function of this protein is to pump Na+ atoms out of the cell and K+ atoms in.
What is the concentration gradient created by sodium-potassium pump? Do these gradients change ?
K+ : 30x more concentrated inside the cell than out
Na+: 15x more concentrated outside the cell than in
These concentration gradients don’t change, unless the cell dies
What is the consequence of there being K+ ions being crowded inside the cell?
Potential energy because they will leave if they can
What is diffusion?
The concept that molecules will move from regions of high concentration to regions of low concentration
What is the resting membrane potential of different neurons?
-40 to -90
What happens where there is more K+ leak channels?
The more permeable it will be to K+ and the closer its membrane potential will be to the true electrochemical equilibrium of K+ (-90 mv)
What is the membrane potential?
Electrical charge across a cell membrane: difference in electrical potential inside and outside the cell
What is the resting potential?
The membrane potential of a neuron at rest
What are receptors?
Proteins that act as sensors - which are sensitive to specific features of the extracellular environment
What happens when the receptors on neuronal membranes of ion channels are activated?
They open a pore/hole/gate that ions can pass through
What can ions do?
They can either depolarize or hyper polarize the neurons membrane potential
What is depolarization?
When the membrane potential of a cell becomes less negative than it normally is at rest
(Example depolarize from -60 to -30)
What does the abundance of leak channels ensure?
That the membrane potential never deviates from its resting state for very long
What happens to K+ ions when Na+ ions enter a neuron through an ion channel?
The Na+ ions entering causes membrane depolarization, which causes K+ ions to leave the cell which restores membrane potential
What are the five proteins of an action potential?
Setting up proteins:
1. Sodium potassium transporter
2. Leak potassium channels
The voltage gated ion channels:
3. Voltage gated sodium channel
4. Voltage gated potassium channel
5. Voltage gated calcium channel
What happens when the membrane potential becomes less negative than -40 mv
The voltage gated sodium channel opens
What are voltage gated sodium channels permeable to?
Only Na+
What happens when one Na+ channel opens?
It causes Na+ ions to rush in (this is propelled by diffusion and electrostatic forces) The influx of Na+ depolarizes the membrane more, which causes more Na+ channels to open which creates an avalanche effect until all voltage-gated Na+ channels open, causing the membrane potential tp shoot up to +40mv
What is the action potential? What causes it?
A brief electrical impulse that provides the basis of conduction of information along the axon. It is a rapid change in the membrane potential caused by the opening and closing of voltage gated ion channels.
What is the threshold of excitation?
The value of membrane potential that must be reached to produce and action potential
What drives the initial depolarization that starts an action potential?
The activation of a receptor that lets Na+ ions enter
What is a leak channel that helps restore the resting membrane potential?
The potassium leak channel
What does the voltage gated potassium channel do?
Restores the resting membrane potential back down to -60mV
When do voltage gated potassium ion channels open?
When the membrane potential rises above 0Mv
What do the outflow of K+ through channels do?
Drive the membrane potential back down within a milisecond
What is the refractory period?
The post action potential hyperpolarization - impossible to trigger an action potential during this time
When do voltage gated calcium channels open?
When the axon terminal becomes depolarized
How concentrated is calcium in versus outside the cell?
it is 1000x more concentrated outside the cell than in
What is the primary means of communication between neurons?
Synaptic transmission
What is synaptic transmission?
Transmission of messages from one neuron to another via the presynaptic release of a chemical (a neurotransmitter) that cross the synapse and bonds to receptors located on the post synaptic membrane
What happens when action potentials are conducted down an axon?
It causes voltage gated calcium channels to open
What happens when there’s an influx of calcium?
It causes several synaptic vesicles to simultaneously fuse with the presynaptic membrane … when they fuse these vesicles break open and spill their contents into the synaptic cleft
What is the movement of information along the axon referred to?
Conduction of the action potential
What is the all or none law?
Action potential occurs or does not occur. Once triggered, will propagate down the axon without growing or diminishing in size, to the end of the axon.
What is the rate law?
The strength of the stimulus is represented by the rate of the firing axon
