**Question:**"Membrane permeability at the falling phase of an action potential is dominated by:"- Co-transporters- Nongated Channels- \( \text{K}^+ \) Voltage-gated Channels- \( \text{Na}^+ \) Voltage-gated Channels- Chemically-gated Channels**Explanation:**This question asks about the physiological processes during the action potential of neurons, specifically the ion channels that influence membrane permeability during the falling phase. The correct answer would involve identifying the type of ion channel that becomes most active or predominant during this phase. Membrane permeability at the rising phase of an action potential is dominated by:- Co-transporters- Nongated Channels- \( \text{K}^+ \) Voltage-gated Channels- \( \text{Na}^+ \) Voltage-gated Channels- Chemically-gated Channels

The neurons send signals over long distances by generating and propagating action potentials over excitable axonal membranes. It is a brief change in membrane potential in which the potential changes from -70 mV to +30 mV. The potential value may vary between species to species. It has three important stages that are depolarization, repolarization and hyperpolarization. When a membrane potential of the axon reaches threshold, a rapid change in the membrane potential is observed in the form of action potential. The falling phase is also known as the repolarization phase that is caused by the slow closing of sodium channels and the opening of the voltage gated potassium channels. In this way the membrane permeability returns to the resting stage turning or reversing the potential to the resting potential. The entry of the sodium ions declines and the slow gated potassium starts opening and the potassium ions rush out of the cell, hence acting to restore the negative membrane potential of the cell. Therefore the membrane permeability at the falling phase of an action potential is dominated by voltage gated potassium channels. The rising phase is also known as depolarization phase is caused when the positively charged sodium ions move via the voltage gated sodium channels into a neuron. When the additional sodium rushes in the potential may rise beyond +30 mV, the membrane potential reverses the polarity. This results in less negative potential inside the cell. It is vital for function of many cells, communication between cells and for overall physiology of organisms. Therefore the membrane permeability at the rising phase of an action potential is dominated by voltage gated sodium channels. A non gated ion channel simply allows ions and water to flow freely from one side of a membrane to another ; these types of channels are more often found within the organelles and places where ion gradients are not maintained. Cotransporters are the membrane proteins that favors the movement of one molecule with its concentration gradient and the unfavorable movement of another molecule against its concentration gradient. Chemically gated channels opens and close in response to chemicals like neurotransmitters, hormones and due to ions such as hydrogen and calcium ions that are involved in generating graded potential.

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Membrane permeability at the falling phase of an action potential is dominated by: O Co-transporters O Nongated Channels O K* Voltage-gated Channels O Na* Voltage-gated Channels O Chemically-gated Channels

Membrane permeability at the falling phase of an action potential is dominated by: O Co-transporters O Nongated Channels O K* Voltage-gated Channels O Na* Voltage-gated Channels O Chemically-gated Channels

Human Anatomy & Physiology (11th Edition)

11th Edition

ISBN:9780134580999

Author:Elaine N. Marieb, Katja N. Hoehn

Publisher:Elaine N. Marieb, Katja N. Hoehn

Chapter1: The Human Body: An Orientation

Section: Chapter Questions

Problem 1RQ: The correct sequence of levels forming the structural hierarchy is A. (a) organ, organ system,...

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