cranial nerve

Examples of cranial nerve in the following topics:

• Sensory-Somatic Nervous System

  • Humans have 12 cranial nerves, nerves that emerge from or enter the skull (cranium), as opposed to the spinal nerves, which emerge from the vertebral column.
  • Each cranial nerve has a name .
  • Some cranial nerves transmit only sensory information.
  • Other cranial nerves transmit almost solely motor information.
  • Other cranial nerves contain a mix of sensory and motor fibers.

• The Nervous System

  • The nervous system is composed of the central nervous system (brain and spinal cord) and the peripheral nervous system (nerves).
  • The spinal cord is the information superhighway, connecting the brain with the rest of the body through the peripheral nerves.
  • The peripheral nervous system consists of nerves that are connected to the brain (cranial nerves) and nerves that are connected to the spinal cord (spinal nerves).

• Thermoreception

  • End-bulbs are found in the conjunctiva of the eye, in the mucous membrane of the lips and tongue, and in the epineurium of nerve trunks.
  • In addition to Krause end bulbs that detect cold and Ruffini endings that detect warmth, there are different types of cold receptors on free nerve endings.
  • These thermoreceptors, which have free nerve endings, include only two types of thermoreceptors that signal innocuous warmth and cooling respectively in our skin.
  • Warmth and cold information from the face travels through one of the cranial nerves to the brain.
  • Describe the various types of receptors used for thermoreception:  Krause end bulbs, Ruffini endings, free nerve endings

• The Vestibular System

  • It is the vestibular branch of the vestibulocochlear cranial nerve that deals with balance.

• Transduction of Sound

  • When sound waves reach the ear, the ear transduces this mechanical stimulus (pressure) into a nerve impulse (electrical signal) that the brain perceives as sound.
  • When these pressure waves reach the ear, the ear transduces this mechanical stimulus (pressure wave) into a nerve impulse (electrical signal) that the brain perceives as sound.
  • As a result, the hair cell membrane is depolarized, and a signal is transmitted to the chochlear nerve.
  • The cochlear branch of the vestibulocochlear cranial nerve sends information on hearing.
  • Movement of stereocilia on hair cells results in an action potential that travels along the auditory nerve.

• Human Axial Skeleton

  • The skull consists of 22 bones, which are divided into two categories: cranial bones and facial bones.
  • The cranial bones are eight bones that form the cranial cavity, which encloses the brain and serves as an attachment site for the muscles of the head and neck.
  • Each vertebral body has a large hole in the center through which the nerves of the spinal cord pass.
  • There is also a notch on each side through which the spinal nerves, which serve the body at that level, can exit from the spinal cord.
  • The cranial bones, including the frontal, parietal, temporal, occipital, ethmoid, and sphenoid bones.

• Early Homo

  • The Homo genus, to which humans belong, evolved from our close primate relatives, Australopithecus, and is distinguished by cranial size.
  • The most salient physiological development between the earlier hominin species and Homo is the increase in cranial capacity, although body size also increased in Homo erectus.
  • This increase in cranial capacity ranged from about 450 cm3 (27 cubic inches) to 600 cm3 (37 cubic inches).
  • With the arrival of Homo erectus in the fossil record, cranial capacity doubled to 850 cm3.

• Neurons and Glial Cells

  • Instead, they have a system of separate-but-connected nerve cells (neurons) called a "nerve net."
  • Echinoderms, such as sea stars, have nerve cells that are bundled into fibers called nerves.
  • (a) In cnidarians, nerve cells form a decentralized nerve net.
  • (b) In echinoderms, nerve cells are bundled into fibers called nerves.
  • (d) In addition to a brain, arthropods have clusters of nerve cell bodies, called peripheral ganglia, located along the ventral nerve cord.

• Characteristics of Chordata

  • Animals in the phylum Chordata share four key features: a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail.
  • It is located between the digestive tube and the nerve cord, providing skeletal support through the length of the body.
  • The dorsal hollow nerve cord derives from ectoderm that rolls into a hollow tube during development.
  • In contrast to the chordates, other animal phyla are characterized by solid nerve cords that are located either ventrally or laterally.
  • The nerve cord found in most chordate embryos develops into the brain and spinal cord, which comprise the central nervous system.

• Animal Body Planes and Cavities

  • In the posterior cavity, the cranial cavity houses the brain and the spinal cavity (or vertebral cavity) encloses the spinal cord.
  • Just as the brain and spinal cord make up a continuous, uninterrupted structure, the cranial and spinal cavities that house them are also continuous.
  • The dorsal cavity, indicated in green, contains the cranial and the spinal cavity.