Cardozo, David. Series B, Physical and Biological Sciences 84, no. To learn more about our GDPR policies click here. If you want more info regarding data storage, please contact gdpr jove. Your access has now expired. Provide feedback to your librarian. If you have any questions, please do not hesitate to reach out to our customer success team.
Login processing Chapter Nervous System. Chapter 1: Scientific Inquiry. Chapter 2: Chemistry of Life. Chapter 3: Macromolecules. Chapter 4: Cell Structure and Function. Chapter 5: Membranes and Cellular Transport. Chapter 6: Cell Signaling. Chapter 7: Metabolism. Chapter 8: Cellular Respiration.
Chapter 9: Photosynthesis. Chapter Cell Cycle and Division. Chapter Meiosis. Chapter Classical and Modern Genetics. Chapter Gene Expression. Chapter Biotechnology. Chapter Viruses. Chapter Nutrition and Digestion. Chapter Sensory Systems. Chapter Musculoskeletal System.
Chapter Endocrine System. Chapter Circulatory and Pulmonary Systems. Chapter Osmoregulation and Excretion. Chapter Immune System. Chapter Reproduction and Development. Chapter Behavior. Chapter Ecosystems. In this section, we wish to better understand the physiological significance of the membrane potential.
Indeed, the normal value of the membrane potential is essential for many physiological processes. In particular, we will use two examples to highlight why it is important to maintain the resting membrane potential at a sufficiently negative value.
Role of the membrane potential in allowing for normal action potential generation. In a later lecture on the neuronal action potential , we will see that the action potential i. A similar situation is also at play in muscle cells skeletal, cardiac, and smooth. Thus, the normal generation of action potentials depends on a normal physiological value of the resting membrane potential.
Recovery from inactivation is a voltage-dependent process that takes place at membrane potential values more negative than the threshold voltage. Thus, the return of the membrane potential to the resting value is critical for allowing these channels to continue to function properly. The consequence of this will be devastating for the organism in that neurons can no longer fire and cardiac myocytes can no longer contract to pump blood through the circulatory system.
It should be clear that this situation will result in the death of the organism! Contribution of the membrane potential to the concentrative capacity of secondary active transporters. Another example that highlights the importance of the resting membrane potential is the influence of the value of the membrane potential on the activity of electrogenic transport proteins.
In the small intestine, this process is essential for the absorption of glucose contained in ingested food across the wall of the small intestine. Once inside the cell, glucose leaves the cell down a concentration gradient via the activity of a facilitative glucose transporter GLUT present in the basolateral membrane.
After transport across the wall of the small intestine, glucose enters the circulation via mucosal capillaries. In the kidneys, glucose is filtered out of the glomerular capillaries to enter the Bowman's space and later the lumen of the proximal tubule. In healthy individuals, all of the glucose present within the lumen of the proximal tubule is reabsorbed across the wall of the proximal tubule. Reabsorbed glucose then enters the peritubular capillaries to reenter the circulation.
For the nervous system to function, neurons must be able to send and receive signals. These signals are possible because each neuron has a charged cellular membrane a voltage difference between the inside and the outside , and the charge of this membrane can change in response to neurotransmitter molecules released from other neurons and environmental stimuli. The lipid bilayer membrane that surrounds a neuron is impermeable to charged molecules or ions.
To enter or exit the neuron, ions must pass through special proteins called ion channels that span the membrane. Ion channels have different configurations: open, closed, and inactive, as illustrated in Figure 1.
Some ion channels need to be activated in order to open and allow ions to pass into or out of the cell. These ion channels are sensitive to the environment and can change their shape accordingly. Ion channels that change their structure in response to voltage changes are called voltage-gated ion channels. Voltage-gated ion channels regulate the relative concentrations of different ions inside and outside the cell.
The difference in total charge between the inside and outside of the cell is called the membrane potential. Figure 1. Voltage-gated ion channels open in response to changes in membrane voltage.
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