Chapter 48-49: Neurons, Synapses, and Nervous Systems Flashcards
What are the two important parts of the neuron structure? What are their functions?
Dendrites - receiving antennas (receives messages)
Axon - transmitting antenna (transmits messages to next cell)
What is the synaptic terminal?
Where neurotransmitters go to the other cell
What is the resting potential?
The negative and positive difference between the inside and the outside of the cell
What is the membrane potential?
Has values
The membrane potential is negative under resting conditions and becomes positive during an action potential.
What is the action potential?
When the potential switches from increasing to decreasing
What pumps are responsible for the resting potential?
Na+ and K+ pumps and ion channels
What do the Na+ and K+ pumps do for the resting potential?
Create electrochemical gradients
They have gates
Is the inside of the cell positive or negative at rest?
Negative
What is the threshold?
When there is a change
When the membrane depolarizers and creates an action potential
When will an action potential be fired?
- direct stimulation
- receives neurotransmitters from another neuron
Action potentials _______ ATP.
Require
At the resting potential, there is a _____ [Na+] outside of the cell, and a _____ [K+] inside of the cell.
High, high
What are gated ion channels?
An ion channel protein with a gate. If there’s a voltage change the gate will open.
What is hyperpolarization?
When the membrane potential inside the cell becomes negative
What is depolarization?
When the cell becomes more positive
Explain the 5 stages of the action potential
Depolarization
1) Resting State:
- membrane potential is neg
- gates closed
2) Depolarization:
- a stimulus opens the Na+ channel
- mem. pot. becomes positive
3) Wave of Opening:
- open Na+ channel causes other Na+ channels to open
- more positive
Hyperpolarization
4) Na+ channels close
- threshold is met
- K+ channels open
- more negative
5) Undershoot
- K+ is still open
- refractory period (getting back to step 1)
- can be too hyperpolarized, too neg
______ insulates Axons.
Prevents charges from flowing in and out
Myelin
What is triggered when a signal comes down the Axon?
The Ca2+ channel opens and ca goes into the cell
How does the Ca2+ help the communication at the synapse?
It allows neurotransmitters to diffuse and attach to the ligand-gated channels
What happens when the neurotransmitter touches the channel protein across the synapse?
Gate opens
Are neurotransmitters hydrophobic or hydrophilic?
Hydrophilic
What are the two ways that a ligand-gates ion channel receives neurotransmitter signals?
1) Excitatory postsynaptic potentials (EPSP)
2) Inhibitory postsynaptic potentials (IPSP)
What does the Excitatory postsynaptic potential (EPSP) do?
Depolarize the membrane
(bringing it closer to the threshold)
- increase the voltage
Why does EPSP happen?
There was an influx of positively charged ions (Na+) into the cell.
What does the Inhibitory postsynaptic potential (IPSP) do?
Hyperpolarize the membrane
(bringing it further from the threshold)
- decrease the voltage
Why does IPSP happen?
K+ ions went out of the cell.
What happens when the gate of an ion channel opens?
The ions move in and the cell becomes more positive.
What are some properties of neurotransmitter?
- small
- diffuse fast
- polar/hydrophilic
Explain the two ways that neurotransmitter signaling can be terminated.
1) Enzymatic breakdown
- inactivating enzymes cut up the neurotransmitter and destroy them
2) Reuptake
- there is a neurotransmitter transport channel at the bottom of the Axon that transports neurotransmitters back into a vesicle within the Axon in order to be reused
What happens when two synapses are active at the same time?
The strength of the postsynaptic response increases
What is long-term potentiation?
Continuous increase of synapse signaling
How does long-term potentiation work?
What are the effects of it?
- When one gated receptor has been opened ions flow into the cell
- Other receptors are notified that a signal is happening and they move to the membrane
- They open their channels and allow more ions in
- —> increase in synaptic signaling
- —> depolarization
- —> action potential
How can the cell increase synapse signaling?
- Increase concentration of receptors
- Increase concentration of neurotransmitters
- Decrease (slow down) reuptake
- Decrease the activity of neurotransmitter inhibitors^(these inhibitors bind to the receptors and open them up, letting neg. into the cell and pos. out of the cell, reducing the chances of an action potential –> this is why it needs to be decreased in order to increase synapse signaling)
In terms of receptors, how can someone have schizophrenia?
- Their dopamine receptors are overactive (receptor opens even if no dopamine is binded)
- They have too little glutamate/glutamate receptors (glutamate is needed for signaling)
How can someone have depression?
Decreased dopamine
How can someone have drug addiction?
They have an enhanced dopamine effect, which leads to a reward system response.
How can someone have Alzheimer’s disease?
Their neurons die
How can someone have Parkinson’s disease?
Decrease in dopamine
