Related Concept Videos

Factors Affecting Drug Distribution: Tissue Permeability01:30

Factors Affecting Drug Distribution: Tissue Permeability

The drug distribution process within the human body is a complex interplay of various physicochemical properties inherent to the drugs. These properties, including molecular size, ionization degree, partition coefficient, and stereochemical nature, significantly impact how drugs permeate biological membranes to reach their target tissues.
Small molecules with a molecular weight below 500 to 600 Daltons can easily pass through the capillary membrane, gaining access to different tissues. Larger...
Factors Affecting Drug Distribution: Organ Perfusion Rate01:15

Factors Affecting Drug Distribution: Organ Perfusion Rate

Drug distribution within the body is a complex process influenced by several factors, including perfusion rate, the rate at which the bloodstream transports drugs to tissue. This limitation becomes particularly significant when dealing with highly lipophilic drugs. In such cases, the rate at which the drug can move across membranes is crucial, and if the membrane is highly permeable to the drug, distribution becomes rate-limited by perfusion.
Perfusion rate-limited distribution relies on the...
Factors Affecting Drug Distribution: Physiological Barriers01:23

Factors Affecting Drug Distribution: Physiological Barriers

Drug distribution in the body is intricately regulated by various physiological barriers that control the passage of substances. These include the capillary endothelial barrier, the blood-brain, blood-cerebrospinal fluid, blood-placental, and blood-testis barriers.
The capillary endothelial barrier allows only smaller molecules below 600 Da (Daltons) to pass through. It also restricts drugs like heparin that are bound to blood components, limiting their movement within the bloodstream.
The...
Excitatory and Inhibitory Effects of Neurotransmitters01:29

Excitatory and Inhibitory Effects of Neurotransmitters

When an action potential reaches the presynaptic axon terminal, it releases neurotransmitters from the neuron into the synaptic cleft at a chemical synapse. The released neurotransmitter can be excitatory or inhibitory. The critical criteria commonly used to determine whether a molecule is a neurotransmitter at a chemical synapse are the molecule's presence in the presynaptic neuron. Second, its release is in response to strong presynaptic depolarization. And lastly, the presence of specific...
Ligand-Gated Ion Channel Receptor: Gating Mechanism01:30

Ligand-Gated Ion Channel Receptor: Gating Mechanism

Ligand-gated ion channels are transmembrane proteins that play a vital role in intercellular communication and functions of the nervous system. They allow the influx of ions across the membrane once the neurotransmitter binds, allowing the subsequent transmission of electrical excitation across the neurons. Other ligand-gated ion channels, like the γ-aminobutyric acid (GABA) receptor, permit anions like chloride into the cells on the binding of the GABA molecule. Their entry into the cell...
Postsynaptic Potential (PSP)01:32

Postsynaptic Potential (PSP)

Postsynaptic potential (PSP) refers to a change in the electrical potential of a neuron when neurotransmitters released by presynaptic neurons bind to postsynaptic receptors. This potential can either be excitatory, leading to depolarization and ultimately action potential generation, or inhibitory, leading to hyperpolarization and suppression of the postsynaptic neuron.
There are two types of receptors: ionotropic and metabotropic.
The ionotropic receptor is the membrane protein that has an...