nervous communication Flashcards
What is resting potential?
The resting potential is the electrical potential difference across the membrane of a neuron when it is not transmitting an impulse.
It is typically around -70mV.
This is maintained by the sodium-potassium pump, which actively transports:
3 sodium ions (Na⁺) out of the neuron.
2 potassium ions (K⁺) into the neuron.
The neuron is polarized, with the inside of the cell being negative relative to the outside.
What happens during an action potential?
When a stimulus reaches a threshold, sodium channels open.
Sodium ions (Na⁺) rush into the neuron, depolarizing the membrane.
Once the membrane potential reaches around +40mV, potassium channels open.
Potassium ions (K⁺) exit the neuron, repolarizing the membrane.
The neuron then enters a refractory period, where it cannot be excited again until it returns to resting potential.
What is saltatory conduction?
Saltatory conduction is the process by which action potentials jump from one node of Ranvier to the next along myelinated axons.
This speeds up the transmission of the action potential because it doesn’t have to travel along the entire length of the axon.
The myelin sheath acts as an insulator, preventing ion flow across the membrane, thus action potentials only occur at the nodes.
Describe synaptic transmission.
An action potential arrives at the presynaptic terminal.
Calcium ions enter the presynaptic neuron, causing synaptic vesicles to fuse with the membrane.
The vesicles release neurotransmitters (e.g., acetylcholine) into the synaptic cleft.
Neurotransmitters bind to receptors on the postsynaptic membrane, causing depolarization or hyperpolarization of the postsynaptic neuron.
The neurotransmitter is either broken down by enzymes (e.g., acetylcholinesterase) or taken back up by the presynaptic neuron.
exam question
Explain how the resting potential of a neuron is established and maintained.
The resting potential is the difference in charge across the membrane when the neuron is at rest, typically around -70mV.
It is maintained by the sodium-potassium pump, which actively transports:
3 sodium ions (Na⁺) out of the cell.
2 potassium ions (K⁺) into the cell.
This creates a higher concentration of sodium ions outside the neuron and a higher concentration of potassium ions inside, maintaining the negative charge inside the neuron.
Exam question
Describe the process of synaptic transmission from the arrival of an action potential at the presynaptic terminal to the response in the postsynaptic neuron.
Back:
An action potential arrives at the presynaptic terminal.
Calcium ions enter the presynaptic neuron, causing synaptic vesicles to fuse with the membrane.
The vesicles release neurotransmitters (e.g., acetylcholine) into the synaptic cleft.
The neurotransmitter binds to receptors on the postsynaptic membrane, opening ion channels and leading to depolarization of the postsynaptic neuron.
The neurotransmitter is either broken down by enzymes (e.g., acetylcholinesterase) or reabsorbed by the presynaptic neuron.
Exam Question:
Explain the role of the myelin sheath in the conduction of nerve impulses.
The myelin sheath is a fatty insulating layer around the axon that speeds up nerve impulse conduction.
It forces the action potential to jump between the nodes of Ranvier in a process called saltatory conduction.
This is much faster than continuous conduction, where the action potential would need to travel the entire length of the axon.
How is the resting potential maintained?
he sodium-potassium pump (Na+/K+ pump) actively transports ions across the membrane to establish and maintain the resting potential.
3 sodium ions (Na⁺) are pumped out of the neuron.
2 potassium ions (K⁺) are pumped into the neuron.
This creates a higher concentration of sodium ions outside the neuron and a higher concentration of potassium ions inside the neuron, contributing to the negative charge inside.
Additionally, potassium leak channels allow some potassium ions to diffuse out of the cell, contributing to the negative charge on the inside.
What triggers the depolarization of the neuron?
A stimulus (e.g., light, pressure, or chemical signal) causes a small local change in the membrane potential, which triggers the depolarization if the stimulus is strong enough.
How does depolarization occur?
The stimulus causes sodium channels to open at the point of stimulation.
Sodium ions (Na⁺), which are at a high concentration outside the neuron, rush into the cell.
The influx of positively charged sodium ions makes the inside of the neuron less negative, resulting in depolarization.
If the membrane potential reaches a threshold value (typically around -55mV), this triggers a full action potential.
What is the threshold potential and how does it lead to an action potential?
https://chatgpt.com/#:~:text=The%20threshold%20potential%20is,of%20sodium%20ions.
