Concept explainers
To discuss:
The distinction between leak channels and gated channels, and between ligand-gated, voltage-gated and mechanically gated channels.
Introduction:
Cells are regarded as the simplest unit (structural and functional) of life. Cellular membrane, nucleus, and cytoplasm are the three major components of a cell. Cellular membrane, which surrounds the entire cell, is composed of phospholipids and proteins. Membrane proteins that traverse the entire cell membrane alone can serve as a membrane channel. A channel protein aids in the transfer of solutes (water and hydrophilic solutes) from one side of the selectively permeable membrane to the other side of the membrane. Such integral proteins are called as transmembrane proteins.
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A&P UNITY AND FUNCTION ACCESS
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- Which of the following are TRUE, when describing the Action Potential of a Non- Contractile Cardiac Pacemaker cell? Select ALL that are true. O Resting membrane potential is more polarized than in neurons, because of more Leakage channels for K+. Progressive Na+ channel (the "funny current", iNa) opening, activates a Transient Voltage Sensitive (T-type) Ca++ channel. Together these channels depolarize the membrane and activate Voltage-Sensitive Long-acting (L-Type) Ca++ channel. The resulting depolarization, closes the "funny" current and T-type Ca++ channels. O Action Potential depolarization, resulting from the Voltage-Activated Na+ channel, triggers Voltage-Sensitive Long-acting (L-Type) Ca++ channel. OMembrane depolarization triggers Voltage-Activated K+ channels (Delayed Rectifier) to open. Increasing K+ permeability and repolarizing the membrane. When the membrane polarizes to -60 mv, the Delayed Rectifier closes and a progressive Na+ channel (the "funny current", iNa) opens. The…arrow_forwardElectrophysiology of the Neuron Phase State of lon Channels Movement of lons Voltage Across Membrane RMP Resting Membrane Potential Hyperpolarizing Graded Potential IPSP Depolarizing Graded Potential EPSP Depolarization Phase of Action Potential Peak of Action Potential Repolarization Phase of Action Potential Hyperpolarization Phase of Action Potential Return to RMP All voltage gated channels - CLOSED All chemically gated channels -CLOSED Voltage gated Na* CLOSED Voltage gated Na' OPEN Na+ and K+ leak channels - OPEN Na+ K+ pump working K+ Voltage gates close slowly Voltage gated K* CLOSED Voltage gated K* OPEN Cl- chemically gated channels- OPEN Na+ chemically gated channels-OPEN K+ chemically gated channels -OPEN 2 K+ pumped IN 3 Na+ pumped OUT K+ diffuses OUT Na* diffuses IN K+ diffuses out or Ch -70 mV to -56 mV -55mV to +30 mv -70 mV +30mv More negative than -70 mV +30mV to -70 mVarrow_forwardAn influx of positive sodium ions eventually causes closing of the inactivation gates of voltage regulated sodium channels, stopping the influx of positive sodium ions, and thus the final stages of an action potential are regulated by _____ feedback.arrow_forward
- Which of the following statements best describes the features of voltage-gated K+ channels? They consist of 4 subunits, are activated at the same time as voltage-gated Na+ channels, but do not inactivate. They consist of 4 subunits, are activated by depolarisation and close slowly during the refractory period. They have 24 membrane spanning alpha helices, 4 of which have positively charged amino acids which promote a conformational change in the channel following depolarisation. They consist of 4 subunits and are open at rest which causes the resting membrane potential to be close to the K+ equilibrium potential.arrow_forwardVoltage-gated K+ channel senses voltage across the plasma membrane and permits selective passage of K+ ions. True Falsearrow_forwardMembrane permeability at the rising phase of an action potential is dominated by: O Co-transporters Nongated Channels O K+ Voltage-gated Channels O Na+ voltage-gated Channels O Chemically-gated Channelsarrow_forward
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