Myelination dramatically increases the conduction velocity of a nerve axon because myelin increases membrane resistance and lowers membrane capacitance. Myelination allows an action potential to be conducted very rapidly from one node of Ranvier to the next.

The functions of sinuses are to lessen the weight of the skull, which makes upright posture easier; to offer resonance to the voice; and to protect the brain from frontal trauma.

Neurosurgical procedures and cerebrovascular accidents often result in the accumulation of interstitial fluid in the brain and swelling of the neurons. Because brain is enclosed within the skull, edema can raise intracranial pressure and thereby disrupt neuronal function which leads to death and coma.

The basic structure of an immunoglobulin: Two light chains and two heavy chains form an antibody molecule. The chains are linked by disulfide bonds. The variable portions near the amino end of the light and heavy chains bind the antigen.The Fc region of the molecule may bind to surface receptors of several cell types.

Keloid is a local swelling caused by abnormal amounts of collagen that form in scars of the skin. Keloids, which occur most often in individuals of black African descent, can be troublesome clinical problem to manage; not only can they be disfiguring, but excision is almost always followed by recurrence.

Large vessels usually have vasa vasorum, which consist of arterioles, capillaries, and venules in the tunica adventitia and the outer part of the media. The vasa vasorum provide metabolites to cells of those layers.

Cervical carcinoma is derived from stratified squamous epithelium. Although it is observed fairly frequently, the mortality rate is decreasing rapidly worldwide because this carcinoma is now usually detected in its early stages by routine screening programs. For such tests cervical cells are studied by exfoliative cytology.

The citric acid cycle is a key metabolic pathway that connects carbohydrate, fat, and protein metabolism. The reactions of the cycle are carried out by eight enzymes that completely oxidize acetate (a two carbon molecule), in the form of acetyl-CoA, into two molecules each of carbon dioxide and water. Through catabolism of sugars, fats, and proteins, the two-carbon organic product acetyl-CoA is produced which enters the citric acid cycle.

Alzheimer's disease is thought to be caused by the abnormal build-up of proteins in and around brain cells. One of the proteins involved is called amyloid, deposits of which form plaques around brain cells. The other protein is called tau, deposits of which form tangles within brain cells. Memantine is used for moderate Alzheimer's disease.

The skeletal system is your body’s central framework. Bones contain bone marrow. Red and white blood cells are produced in the bone marrow. The periosteum is a tough membrane that covers and protects the outside of the bone. Below the periosteum, compact bone is white, hard, and smooth. It provides structural support and protection. The core, inner layer of the bone is softer than compact bone. It has small holes called pores to store marrow.

Hepatitis D, also known as “delta hepatitis,” is a liver infection caused by the hepatitis D virus (HDV). Hepatitis D only occurs in people who are also infected with the hepatitis B virus. Hepatitis D is spread when blood or other body fluids from a person infected with the virus enters the body of someone who is not infected. Hepatitis D can be an acute, short-term infection or become a long-term, chronic infection. Hepatitis D can cause severe symptoms and serious illness that can lead to life-long liver damage and even death.

Vitamin B6 is a water-soluble vitamin. Water-soluble vitamins dissolve in water so the body cannot store them. Leftover amounts of the vitamin leave the body through the urine. Although the body maintains a small pool of water-soluble vitamins, they have to be taken regularly.

Lack of Vitamin B6 in the body is uncommon. It can occur in people with kidney failure, liver disease, or alcohol dependence.

Ivermectin is a medication used to treat parasite infestations. In humans, these include head lice, scabies, river blindness, strongyloidiasis, trichuriasis, ascariasis, and lymphatic filariasis. Ivermectin and its related drugs act by interfering with nerve and muscle function of helminths and insects. The drug binds to glutamate-gated chloride channels that are common to invertebrate nerve and muscle cells.

The Delta variant is more contagious: The Delta variant is highly contagious, more than 2x as contagious as previous variants. Some data suggest the Delta variant might cause more severe illness than previous variants in unvaccinated people. In two different studies from Canada and Scotland, patients infected with the Delta variant were more likely to be hospitalized than patients infected with Alpha or the original virus that causes COVID-19.