Lecture 7 Flashcards
What is GABA considered to be?
An inhibitory neurotransmitter
What is Glycine considered to be?
An inhibitory neurotransmitter
What is Glutamate considered to be?
A excitatory neurotransmitter
Between an excitatory and inhibitory, which will win?
Whichever one has more inputs.
What does Interneuron control?
They carry sensory information and regulate motor activity. More interneurons are activated when a response to stimuli is required to be complex. When the impulse is excitatory, it will turn on motor neuron,
What does a sensory neuron control?
Regulates the final common pathway
What is the final common pathway?
Lower motor neurons, therefore, are the final common pathway for transmitting neural information from a variety of sources to the skeletal muscles
At any one time, what can the nervous system be considered?
“Hard Wired” - does not have inhibitory neurons free floating
- Has many circuits
What happens over time to the nervous system?
It is able to accommodate - not adapt.
- You can change physical/physiological characteristics (phenotype) but can not change actual structure.
What is the Action Potential?
The neurons or muscles cell membrane response to a graded potential
What does depolarizing current achieve?
A threshold
What is the current for a depolarizing current?
The flow of Na + ions into the cell
How does the depolarizing current happen?
The opening of Na+ channels due to an electrical or chemical stimulus
What happens during an action potential?
Large deflection in cell membrane (negative to positive)
What is the large deflection in the cell membrane?
Going from -60 to +30mV
If the resting membrane is at -80mV, what does this mean?
That you need a stronger input to activate it (further negative)
How fast do action potentials happen?
Every 1-2ms
How fast do cardiac muscle cells happen?
Every 400 - 500 ms
What happens at the depolarizing current?
At the depolarizing current, you have a stimulus’ that is working to get the cell into an action potential
What happens at the depolarizing phase?
At the depolarizing phase, the sodium channels are opening, and sodium is flooding into the cell.
What charge is the depolarizing state at?
+30mV
What happens at the depolarizing state?
Na+ channels are closed, and K+ channels open causing K + to leave the cell.
Absolute Refractory Period
When you cannot generate another action potential
Relative Refractory Period
Need a stronger stimulus
Hyperpolarization
A temporary state where the cell becomes slightly more negative.
What is the main purpose fo sodium channels?
They move sodium ions into the cell to flood the cell with positive charge, leading to a depolarization state.
What type of channel is a Sodium Channel?
Voltage Gated (required an electrical stimulus)
What does a Sodium Channel do?
The sodium ion moves down its concentration gradient from high to low, in this case for K+ from the inside (intracellular region) to the outside (extracellular region), working to cause a repolarization of the cell.
*A sodium potassium pump will never move ions into the cell.
Where was the K+ Channel First Discovered?
In Fruit Flies by the “shaker gene”
What is the Shaker K+ Channel
A Shaker Potassium Channel is a type of potassium channel that has been identified as a fundamental regulator of sleep behavior in organisms like fruit flies and mammals.
What is the Atomic Diameter of a K+ Channel?
3 A
What is the radius of a K+ Ion?
1.33A
What is the radius of a Na+ ion?
0.95 A
What happens when Na+ enters into the cell?
Cytoplasmic Dispersion.
What happens to Peak Amplitude (mV) when Axon Length increases?
Amplitude decreases
What is Conduction Velocity?
Nerve conduction velocity is the speed at which an electrochemical impulse propagates down a neural pathway
What are the factors that affect Conduction Velocity?
1.) Axon Diameter: The greater the diameter, faster conduction
2.) Thickness: the thicker the axon, the more propagation
3.) Channels per Unit Area: More channels, faster propogation
4.) The physiological state of the cell: Is it tired?
How many Na+ ions leave the cell for every K+ions coming into the cell in the Na+/K+ Pump?
3 Na+ leave for every 2 K+ that enter the cell.
What are the functions of the Sodium Potassium Pump?
1) Establishes and maintains electric potential (neg on inside, positive on outside)
2.) Reestablishes RMP after disturbances
What is the a unit of the Sodium Potassium Pump’s function?
The catalytic and transport unit of the enzyme
What is the b-unit of the Sodium Potassium Pump’s Function?
Na+ and K+ Affinity
What are the four conformational states of the ATPase?
E1, E1-P,E2-P, E2
What does the “P” indicate?
domain on the enzyme binding part for ATP (phosphate group)
What happens in the E1 state?
3 Na+ Binds and ATP
What happens in the E1-P state?
The ATP is hydrolyzed and the phosphate attaches to the cell and ADP is produced
What stimulates the E1-P phase?
Excess buildup of Na+ intracellular (key stimulant)
What happens in the E2-P state?
Ion binding sites “evert” (changes shape) to the extracellular side of the cell
The enzyme has a low affinity for Na+
What happens in the E2 State
Na+ release into the extracellular and the enzyme is de-phosphorlyated
2 Potassium ions bond and are released into intracellular
