Fourth cranial nerve
Fourth cranial nerve: The fourth cranial nerve, the trochlear nerve, is the nerve supply to the superior oblique muscle of the eye, one of the muscles that moves the eye. Paralysis of the trochlear nerve results in rotation of the eyeball upward and outward (and, therefore, double vision).
The twelve cranial nerves, the trochlear nerve included, emerge from or enter the skull (the cranium), as opposed to the spinal nerves which emerge from the vertebral column.
The trochlear nerve is the only cranial nerve that arises from the back of the brain stem and it follows the longest course within the skull of any of the cranial nerves.
Read Also:
- Fournier's gangrene
Fournier’s gangrene: A horrendous infection of the genitalia that causes severe pain in the genital area (in the penis and scrotum or perineum) and progresses from erythema (redness) to necrosis (death) of tissue. Gangrene can occur within hours. The mortality (death) rates are up to 50%. In this major medical emergency, a bacterial infection spreads […]
- Founder effect
Founder effect: The positive effect on gene frequency when a population (colony) has only a small number of original settlers, one or more of whom had that gene. For example, the gene for Huntington’s disease was introduced into the Lake Maracaibo region in Venezuela early in the nineteenth century. This is now the largest known […]
- G6PD deficiency
Deficiency of the enzyme glucose-6-phosphate dehydrogenase (G6PD), the most common enzyme defect of medical importance. About 10 percent of American black males have G6PD deficiency, as do a lesser percent of black females. G6PD deficiency is also increased in frequency in people of Mediterranean origin (including Italians, Greeks, Arabs, and Jews). The gene encoding G6PD […]
- Gage, Phineas
Gage, Phineas: The most famous patient to have survived severe damage to the brain and the first from whom something was learned about the relation between personality and the function of the front parts (the frontal lobes) of the brain. During work on a railroad in 1848, an unplanned explosion propelled a rod through Gage’s […]
- Gain-of-function mutation
Gain-of-function mutation: A mutation that confers new or enhanced activity on a protein. Loss-of-function mutations, which are more common, result in reduced or abolished protein function.