FINAL Flashcards
(35 cards)
What are 2 types of passive transport?
- Channel-mediated
- Transporter-mediated
What are 3 molecules that can cross the membrane, and 1 that can’t? (in order of most to least permeable)
Can cross the membrane: Hydrophobic molecules, Small Uncharged Polar Molecules, Large Uncharged Polar Molecules
Can’t cross the membrane: Ions
What is membrane potential?
The difference in charge across the membrane
What are the 3 electrical signals a neuron can generate?
- Receptor potentials: occurs when sensory neurons are activated by external stimuli like light, sound, or heat, altering their resting membrane potential
- Synaptic potentials: arise during neuron-to-neuron communication at synaptic junctions, facilitating the transfer of information between them
- Action potentials: Specialized signals that travel along the neuron’s axon, playing a crucial role in rapid signal transmission
Describe the 2 amplifiers used in the voltage-clamp experiment
- amplifier measuring membrane potential of axon
- feedback amplifier that compares the desired potential (command voltage) with the actual membrane potential, and injects necessary current to maintain desired potential
What is passive and active conduction?
- Passive conduction: decays over distance
- Active conduction: constant over distance
What happens when you inject an external depolarizing current into an axon?
Can result in the initiation and propagation of an action potential in both directions
How is the unidirectional propagation of action potentials ensured?
By the inactivation of voltage-gated Na+ channels during the refractory period.
Describe the 4 phases of the action potential
- Resting Phase: Neuron is at resting potential
- Depolarization Phase: Membrane potential becomes less negative, moves towards a positive charge
- Repolarization Phase: Membrane potential returns back towards the negative
- Hyperpolarization Phase: Membrane potential temporarily becomes more negative than the resting level
What 2 things contribute to speed up conduction velocity?
- Myelin sheath
- Axon diameter
What is Electric Charge (Q)?
The physical property of matter that causes it to experience a force when placed in an electromagnetic field. The unit is coulomb (C).
What is Voltage (V)?
The potential difference in electrical charge between two points. The unit is volt (V).
What is Current (I)?
Flow rate of electric charge. The unit is ampere (A). 1A = 1C/sec
What is Resistance (R)?
A force that counteracts the flow of electrical charge (current). The unit is ohm (ohms).
What is Conductance (g) and what is membrane conductance?
Conductance is inverse of resistance. The unit is siemens (S). Membrane conductance is a property of membrane that determines how much charge can go through the membrane.
What is Capcitance (C)?
Ability of a substance to hold an electric charge. The uni is farad (F). Depends on the surface areas, distance between two surfaces, and permeability of the insulator.
What tools are needed for cellular electrical signal measurement? (3)
Requires sophisticated and specific equipment:
- Microelectrodes
- Amplifiers
- Units for data acquistion and analysis
How do you place the microelectrode into the microelectrode holder?
- Ensure to turn the screw cap counterclockwise before you insert (or remove) the electrode
- After placing the electrode, rotate the screw cap clockwise to create a secure seal, but be careful not to tighten it excessively.
What should you make sure to do before starting to use the micromanipulators (after setting up the equipment)?
Ensure that all the control knobs are positioned at the midpoint of their range.
What are 4 features of a stereomicroscope?
- Uses low magnification
- Used for vieweing opaque specimens
- Has a high working distance
- Ideal for viewing dissections/3D objects
What are 4 features of a compound microscope
- Uses high magnification
- Used for viewing transparent specimens
- Has a small working distance (0.14 - 4mm)
- Ideal for ultra-thin samples that you can pass light through (can’t see 3D)
What is signal conditioning?
The process of amplification and then filtering an analog voltage signal that fluctuates over time.
What are the 5 steps to follow for stereo microscope adjustment?
- Ensure that both diopter rings are set in the middle of their range
- Look through the right eyepiece with your right eye and adjust the focus using the “FOCUS CONTROL” knob
- Look through left eyepiece with left eye, and adjust focus using the “DIOPTER ADJUSTMENT RING”
- Finally adjust the distance between the eyepieces until you observe the SAME FIELD with both eyes.
- Whenever, you change the magnification, adjust the focus using the focus control knob, NOT THE DIOPTER ADJUSTMENT RING.
How does increasing K+ concentration (hyperkalemia) in external fluids affect the cell’s potential?
The cell will depolarize initially and increase in excitability of neurons and muslces, but after a while, they may become inexcitable due to the inactivation of Ca2+ and Na+ channels. They then produce small or no action potentials.
