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Questions and Answers
What is the primary function of acetylcholinesterase in the neuromuscular junction?
What is the primary function of acetylcholinesterase in the neuromuscular junction?
How does tropomyosin contribute to muscle contraction?
How does tropomyosin contribute to muscle contraction?
Which diagnostic technique is used to measure the electrical activity of the retina?
Which diagnostic technique is used to measure the electrical activity of the retina?
What do electrodes record during an electromyography (EMG) procedure?
What do electrodes record during an electromyography (EMG) procedure?
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What is a primary purpose of using an electrocardiogram (ECG)?
What is a primary purpose of using an electrocardiogram (ECG)?
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What distinguishes primary active transport from secondary active transport?
What distinguishes primary active transport from secondary active transport?
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What is the function of the sodium-potassium pump?
What is the function of the sodium-potassium pump?
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Which ion is co-transported with glucose during secondary active transport?
Which ion is co-transported with glucose during secondary active transport?
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What mechanism allows mechanically gated ion channels to open?
What mechanism allows mechanically gated ion channels to open?
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Which step is NOT involved in the sodium-potassium pump's function?
Which step is NOT involved in the sodium-potassium pump's function?
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What initiates the depolarization in light-gated ion channels?
What initiates the depolarization in light-gated ion channels?
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Which of the following correctly describes secondary active transport?
Which of the following correctly describes secondary active transport?
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How does the sodium-potassium pump reset itself after releasing potassium ions?
How does the sodium-potassium pump reset itself after releasing potassium ions?
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What two components make up the electrochemical driving force?
What two components make up the electrochemical driving force?
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What defines the threshold of an action potential?
What defines the threshold of an action potential?
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Which type of summation occurs when multiple synapses are activated at the same time?
Which type of summation occurs when multiple synapses are activated at the same time?
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Which characteristic is exclusive to skeletal muscle cells?
Which characteristic is exclusive to skeletal muscle cells?
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What triggers the release of calcium ions in skeletal muscle cells?
What triggers the release of calcium ions in skeletal muscle cells?
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Which of the following is NOT a feature of cardiac muscle cells?
Which of the following is NOT a feature of cardiac muscle cells?
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What effect do excitatory postsynaptic potentials (EPSPs) have on a neuron?
What effect do excitatory postsynaptic potentials (EPSPs) have on a neuron?
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How does cardiac muscle contraction differ from skeletal muscle contraction?
How does cardiac muscle contraction differ from skeletal muscle contraction?
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What occurs when sodium channels open during an action potential?
What occurs when sodium channels open during an action potential?
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Which of the following ions has a higher concentration inside the neuron at resting membrane potential?
Which of the following ions has a higher concentration inside the neuron at resting membrane potential?
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What is the primary purpose of the Nernst Equation?
What is the primary purpose of the Nernst Equation?
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Which statement is true about the Goldman Equation?
Which statement is true about the Goldman Equation?
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What driving force acts on cations when the inside of a cell is negatively charged?
What driving force acts on cations when the inside of a cell is negatively charged?
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Which condition would favor the movement of anions into the cell?
Which condition would favor the movement of anions into the cell?
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How does the opening of potassium channels affect the membrane potential?
How does the opening of potassium channels affect the membrane potential?
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What is the role of negatively charged protein ions within the neuron?
What is the role of negatively charged protein ions within the neuron?
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Study Notes
Membrane Transport
- Lateral Diffusion: Molecules move from side to side within a membrane layer.
- Rotation: Molecules rotate within the membrane layer.
- Swing: Molecules move from side to side within the membrane layer.
- Flexion: The contraction of molecules within the membrane layer.
- Transverse Diffusion (Flip-Flop): Molecules move from one half of a phospholipid monolayer to the other.
Membrane Transport Mechanisms
- Simple Diffusion: Fat-soluble molecules pass directly through the phospholipid bilayer.
- Carrier-mediated Facilitated Diffusion: The movement of a molecule is facilitated through a carrier protein that is specific to that molecule. The carrier protein changes shape to move the molecule across the membrane.
- Channel-mediated Facilitated Diffusion: Molecules move through a channel protein. The channel protein is often selective for size and charge, thus not all molecules can pass through.
- Osmosis: Water diffusion across a membrane, following the concentration gradient.
Fick's First Law
- Flux (J) is the number of atoms passing through a plane of unit area per unit time.
- Fick's first law describes the rate at which atoms, ions, particles, or other species diffuse in a material.
- The rate of diffusion is proportional to the concentration gradient.
Osmosis and Tonicity
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Water moves across a semipermeable membrane from an area of low solute concentration (hypo-osmotic) to an area of high solute concentration (hyper-osmotic) in an attempt to equalize solute concentrations.
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Isotonic: Solutions have the same solute concentration. Net water movement is zero.
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Hypertonic: Solution with higher solute concentration than the inside of the cell. Water moves out of the cell, causing shrinkage (crenation).
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Hypotonic: Solution with lower solute concentration than the inside of the cell. Water moves into the cell, causing swelling (lysis).
Active Transport
- Active processes use energy (ATP) to move substances against a concentration gradient.
- Primary active transport directly uses ATP to transport the substance.
- Examples of primary active transport include: the sodium-potassium pump (3Na+ out, 2K+ in).
- Secondary active transport uses an existing electrochemical gradient to move substances against their concentration gradient.
Ion Channels
- Mechanically gated (ion) channel: Integral membrane protein that opens and closes in response to a stimulus (e.g., touch, vibration, pressure, stretch).
- Voltage-gated (ion) channel: Opens or closes in response to changes in the membrane potential.
- Ligand-gated (ion) channel: Opens or closes in response to a specific signaling molecule (ligand).
- Signal-gated (ion) channel: Responds to intracellular signaling.
Action Potentials
- Changes in membrane potential that propagate along nerve and muscle cell membranes.
- Excitatory postsynaptic potentials (EPSPs): depolarizations leading to a greater likelihood that a neuron will fire.
- Inhibitory postsynaptic potentials (IPSPs): hyperpolarizations leading to a decrease in that likelihood.
Action Potentials in Skeletal Muscle
- Action potentials are electrochemical signals that spread across the sarcolemma of skeletal muscles, initiating muscle contraction.
- The action potential propagation depends on the movement/flow of Na+ ions into and K+ ions out of the muscle cell.
Nerst Equation and Goldman Equation (Simplified)
- The Nerst equation calculates the equilibrium potential for a single ion.
- The Goldman equation takes into consideration multiple ions to calculate the resting membrane potential of a cell.
Nerve-Muscle Transmission
- Acetylcholine is released from the axon terminal and binds to receptors on the sarcolemma.
- This initiates an action potential that travels down the T-tubules to trigger the release of Ca2+ from the sarcoplasmic reticulum.
- Calcium ions bind to troponin, leading to muscle contraction.
- Acetylcholinesterase removes acetylcholine from the synaptic cleft to stop contraction.
Types of Summation
- Spatial Summation: Simultaneous stimulation by several presynaptic neurons.
- Temporal Summation: High-frequency stimulation by a single presynaptic neuron.
Electrocardiography (ECG)
- ECG recording of electrical activity of the heart.
- Used to diagnose heart conditions.
EMG (Electromyography)
- Records electrical activity of skeletal muscles.
- Used to diagnose muscle and nerve disorders.
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Description
Test your understanding of various membrane transport mechanisms, including lateral diffusion, osmosis, and facilitated diffusion. This quiz covers key processes involved in how molecules move across cell membranes. Challenge yourself with questions that delve into these essential biological concepts.
