nerve cord

Examples of nerve cord in the following topics:

• 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.

• Phylum Chordata

  • A notochord, or a longitudinal, flexible rod between the digestive tube and the nerve cord .
  • A dorsal nerve cord which develops from a plate of ectoderm that rolls into a tube located dorsal to the notochord.
  • Other animal phyla have solid nerve cords ventrally located.
  • A chordate nerve cord splits into the central nervous system: the brain and spinal cord.
  • For example, tunicate larvae have both a notochord and a nerve cord which are lost in adulthood .

• Chordates and the Evolution of Vertebrates

  • Adults only maintain pharyngeal slits and lack a notochord, a dorsal hollow nerve cord, and a post-anal tail.
  • It then attaches via the head to the surface and undergoes metamorphosis into the adult form, at which point the notochord, nerve cord, and tail disappear.
  • Members of Cephalochordata possess a notochord, dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail in the adult stage.
  • (c) In the adult stage, the notochord, nerve cord, and tail disappear.
  • Adult lancelets retain the four key features of chordates: a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail.

• Neurons and Glial Cells

  • The CNS contains the brain and spinal cord.
  • Flatworms of the phylum Platyhelminthes have both a central nervous system, made up of a small "brain" and two nerve cords, and a peripheral nervous system containing a system of nerves that extend throughout the body.
  • It contains a brain, ventral nerve cord, and ganglia (clusters of connected neurons).
  • One interesting difference between the nervous systems of invertebrates and vertebrates is that the nerve cords of many invertebrates are located ventrally (near the abdomen), whereas the vertebrate spinal cords are located dorsally (near the back).
  • (d) In addition to a brain, arthropods have clusters of nerve cell bodies, called peripheral ganglia, located along the ventral nerve cord.

• Phylum Nematoda

  • Most nematodes possess four longitudinal nerve cords that run along the length of the body in dorsal, ventral, and lateral positions.
  • The ventral nerve cord is better developed than the dorsal or lateral cords.
  • All nerve cords fuse at the anterior end, around the pharynx, to form head ganglia, or the "brain" of the worm (taking the form of a ring around the pharynx), as well as at the posterior end to form the tail ganglia.

• Spinal Cord

  • The spinal cord is a bundle of nerves that is connected to the brain and relays information from the brain to the body and vice versa.
  • Connecting to the brainstem and extending down the body through the spinal column is the spinal cord: a thick bundle of nerve tissue that carries information about the body to the brain and from the brain to the body.
  • The spinal cord is contained within the bones of the vertebral column, but is able to communicate signals to and from the body through its connections with spinal nerves (part of the peripheral nervous system).
  • Spinal cord injuries are notoriously difficult to treat because spinal nerves do not regenerate, although ongoing research suggests that stem cell transplants may be able to act as a bridge to reconnect severed nerves.
  • Researchers are also looking at ways to prevent the inflammation that worsens nerve damage after injury.

• Sensory-Somatic Nervous System

  • Each cranial nerve has a name .
  • Spinal nerves transmit sensory and motor information between the spinal cord and the rest of the body.
  • Motor neurons have cell bodies in the ventral gray matter of the spinal cord that project to muscle through the ventral root.
  • These neurons are usually stimulated by interneurons within the spinal cord, but are sometimes directly stimulated by sensory neurons.
  • The cell bodies of motor neurons are found in the ventral portion of the gray matter of the spinal cord.

• The Nervous System

  • The nervous system is composed of the central nervous system (brain and spinal cord) and the peripheral nervous system (nerves).
  • The vertebrate central nervous system (CNS) contains the brain and the spinal cord .
  • 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).
  • The innermost layer is the pia mater, which directly covers the brain and spinal cord.

• Human Axial Skeleton

  • The function of the axial skeleton is to provide support and protection for the brain, spinal cord, and organs in the ventral body cavity.
  • The vertebral column, or spinal column, surrounds and protects the spinal cord, supports the head, and acts as an attachment point for the ribs and muscles of the back 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.

• Glia

  • Scientists have recently discovered that they also play a role in responding to nerve activity and modulating communication between nerve cells.
  • They have been shown, through calcium-imaging experiments, to become active in response to nerve activity, transmit calcium waves between astrocytes, and modulate the activity of surrounding synapses.
  • Ependymal cells line fluid-filled ventricles of the brain and the central canal of the spinal cord.
  • They are involved in the production of cerebrospinal fluid, which serves as a cushion for the brain, moves the fluid between the spinal cord and the brain, and is a component for the choroid plexus.