[Calcium release from the rat liver mitochondria during collapse of the membrane potential]

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Feedback Regulation of Calcium Concentration01:27

Feedback Regulation of Calcium Concentration

Calcium is an essential signaling molecule required for various cellular functions. Calcium pumps and ion channels on cell and organellar membranes, such as those on the endoplasmic reticulum (ER), regulate calcium concentrations inside the cell. They remain closed, keeping the cytosolic calcium levels low at a resting state.
Various transmembrane receptors, such as G protein-coupled receptors (GPCRs), elicit a response to extracellular signals by increasing cytosolic calcium. Activated GPCRs...
Cellular Injury IV: Necrosis01:16

Cellular Injury IV: Necrosis

Necrosis is a form of irreversible cell death caused by severe injury such as ischemia, toxins, or trauma. Unlike programmed cell death, it is an uncontrolled, pathological process that typically provokes inflammation in surrounding tissues.Pathophysiologic ChangesNecrosis begins when cells sustain critical damage, leading to swelling of organelles, particularly mitochondria, and rapid ATP depletion. As energy levels decline, membrane ion pumps fail, leading to calcium influx and eventually,...
Relaxation of Skeletal Muscles01:29

Relaxation of Skeletal Muscles

The period of muscle contraction primarily influences the duration of stimulation at the neuromuscular junction (NMJ), the presence of free calcium ions in the sarcoplasm, and the availability of energy or ATP to support contractions.
When an action potential reaches the axon terminal, it depolarizes the membrane and opens voltage-gated sodium channels. Sodium ions enter the cell, further depolarizing the presynaptic membrane. This depolarization causes voltage-gated calcium channels to open.
Resting Potential Decay01:15

Resting Potential Decay

The resting membrane potential of a neuron (-70mV) is sustained due to the selective ion permeability of the membrane. At the resting potential, the membrane is slightly permeable to ions like sodium (Na+) and chloride (Cl−) and highly permeable to potassium ions (K+). Differences in the ions' concentration inside the cell compared to the outside are maintained by membrane transport proteins like channels and pumps.
At rest, the K+ is the main ion that moves across the membrane through...