Podcast
Questions and Answers
What primarily drives the movement of potassium ions (K+) out of a neuron at rest, considering both electrical and concentration gradients?
What primarily drives the movement of potassium ions (K+) out of a neuron at rest, considering both electrical and concentration gradients?
- An equilibrium where the electrical and concentration gradients have no influence.
- The concentration gradient, since there is a higher concentration of K+ inside the cell than outside. (correct)
- The sodium-potassium pump actively transports K+ out of the cell against both gradients.
- The electrical gradient, as the positive charge of K+ is attracted to the negative extracellular space.
How does the sodium-potassium (Na+/K+) pump contribute to maintaining the resting membrane potential of a neuron?
How does the sodium-potassium (Na+/K+) pump contribute to maintaining the resting membrane potential of a neuron?
- It allows Na+ ions to passively diffuse into the cell, balancing the outflow of K+ ions.
- It primarily regulates the flow of chloride ions (Cl-) to stabilize the membrane potential.
- It pumps 3 Na+ ions out of the cell and 2 K+ ions into the cell, creating a net negative charge inside the cell. (correct)
- It pumps equal numbers of Na+ and K+ ions across the membrane, maintaining a neutral charge distribution.
Which of the following is the most accurate description of how an action potential is propagated down an axon?
Which of the following is the most accurate description of how an action potential is propagated down an axon?
- The action potential travels via the movement of large negative ions along the axon.
- The action potential passively diminishes as it travels down the axon, relying on the initial stimulus strength.
- The action potential is regenerated at each point along the axon, maintaining its strength as it travels. (correct)
- The action potential is an electrical current that flows unimpeded down the axon without any need for regeneration.
What is the role of myelin in neuronal transmission, and how does it affect the speed of action potentials?
What is the role of myelin in neuronal transmission, and how does it affect the speed of action potentials?
What determines whether a neurotransmitter will have an excitatory or inhibitory effect on the postsynaptic neuron?
What determines whether a neurotransmitter will have an excitatory or inhibitory effect on the postsynaptic neuron?
During the rising phase of an action potential, what ion is primarily responsible for the depolarization of the neuron?
During the rising phase of an action potential, what ion is primarily responsible for the depolarization of the neuron?
Why is the refractory period important for neuronal function?
Why is the refractory period important for neuronal function?
Which of the following best describes the equilibrium potential of an ion?
Which of the following best describes the equilibrium potential of an ion?
How do voltage-gated ion channels contribute to the generation of an action potential?
How do voltage-gated ion channels contribute to the generation of an action potential?
What is the role of glial cells such as oligodendrocytes and Schwann cells in the nervous system?
What is the role of glial cells such as oligodendrocytes and Schwann cells in the nervous system?
Flashcards
Intracellular Fluid
Intracellular Fluid
Fluid inside a cell. Separated from extracellular fluid by a membrane.
Extracellular Fluid
Extracellular Fluid
Fluid outside a cell, separated from intracellular fluid by a membrane.
Ion Pumps and Channels
Ion Pumps and Channels
Proteins in neuron membranes that control ion movement in/out of the cell.
Ion Movement
Ion Movement
Signup and view all the flashcards
Resting Membrane Potential
Resting Membrane Potential
Signup and view all the flashcards
Action Potential
Action Potential
Signup and view all the flashcards
Electrical Force (Potassium In)
Electrical Force (Potassium In)
Signup and view all the flashcards
Concentration Force (Potassium Out)
Concentration Force (Potassium Out)
Signup and view all the flashcards
Ion Imbalance at Rest
Ion Imbalance at Rest
Signup and view all the flashcards
Refractory Period
Refractory Period
Signup and view all the flashcards
Study Notes
- Every cell in the body is surrounded by a membrane which divides the intracellular fluid from the extracellular fluid
- Neurons contain ion pumps and ion channels in their membranes that control the movement of ions in and out of the cell
- Movement of ions across the neuronal membrane causes electrical signals
- Ion channels can be resting (open), voltage gated, ligand gated, or mechanically gated
Movement of Ions
- Intracellular and extracellular fluid contain different types of ions like Sodium (Na+), Potassium (K+), Chloride (Cl-), and Large negative ions (A-)
- Two forces determine the movement of ions into and out of the cell
- Concentration (high to low density)
- Electrical (negative positive)
- Ion channels only allow specific ions to move through the neuronal membrane
- Different ions have different ion channels
Ion Channels and Resting Membrane Potential
- Sodium ion channels are closed at rest, restricting sodium movement across the membrane
- Some potassium ion channels are open, allowing potassium to move in and out of the cell
- Potassium (K+) is attracted into the cell due to the higher negativity inside compared to outside
- Potassium is drawn out of the cell by lower potassium concentration on the outside
- The two forces are in equilibrium
- The equilibrium potential of K+ at -90mV
Sodium-Potassium Pump
- At rest, a neuron contains more positive ions outside the cell
- The Na/K pump maintains the imbalance by actively transporting 3 positive sodium ions out and 2 positive potassium ions into the cell
- This pump increases potassium concentration inside the cell and sodium concentration outside
Action Potential
- At rest, a neuron has a negative charge of -65 mV
- This is caused by more negative ions inside than outside, known as the Resting Membrane Potential
- Stimulation upsets the equilibrium, and if it passes the threshold, this becomes an action potential
- An action potential is generated at the axon hillock if the net change is above threshold (-50mV)
- An action potential is then propogated down the axon
Sodium and Rise of Action Potential
- Changes in electrical activity leading to an action potential is caused by movement of ions
- When stimulated above the threshold (-50mV), sodium ion channels open
- Sodium is drawn into the cell due to higher external concentration (concentration force), and the cell's negative charge (electrical force)
- Positive Na+ influx makes the cell more positive
Potassium and Fall of Action Potential
- Potassium (K+) loss causes the cell to become more negative
- The cell becomes positively charged when the action potential peaks
- Electrical force which kept potassium inside the cell changes
- Positive potassium ions are attracted to the negative outside, drawing them out
- Because there is more potassium inside the cell than out, concentration force also drives potassium out
Nerve Impulse
- Nerve impulse is quickly propagated down the axon to the presynaptic terminals when an action potential happens in a neuron
- Some axons are covered with myelin, made by glial cells
- Oligodendrocytes
- Schwann cells
- Myelinated axons conduct action potentials faster than unmyelinated axons because of saltatory conduction
Refractory Period
- An action potential is an all or nothing event
- Another action potential cannot be generated until the preceding potential has finished
- Increased firing rate denotes stimulus strength
- Neurons can fire many action potentials per second
Synapse
- When the action potential reaches presynaptic terminal, a neurotransmitter (chemical) is released between the neurons (synapse)
- The neurotransmitter can have an excitatory or inhibitory effect
Nervous System: Excitation and Inhibition
- Epilepsy results from imbalance between excitation and inhibition
- This causes neurons to become too active, resulting in seizures
- Seizures are uncontrollable electrical activity patterns
- The nervous system needs the correct balance of excitatory (EPSP) and inhibitory (IPSP) signals for proper function
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
