Gliomedin

A voltage-gated sodium ion channel opens when there is a change in the voltage of the membrane and allows sodium ions to flow across its electrochemical gradient. These voltage-gated channels are made up of amino acids and they aid in generating and moving an action potential down a membrane or axon (Brooker, Robert, 106).

The structure of neuromuscular junction consists of a neuron and skeletal muscle cell. The motor neurons, which arise from the spinal cord, supply the skeletal muscle fibers. The neuromuscular junction is un-myelin nerve with a bulb shape at the endings that contract the muscle fiber. The schwann cells form a covering over the postsynaptic membrane and nerve membrane of the fiber that is located under the terminal and is categorized as a post-junction folds. The area between the folds and the bulbs create the synaptic cleft. This consists of proteins and proteoglycans. The enzyme acetylcholinesterase; exist only at high levels in the synaptic basal lamina (UMN,

As an action potential travels down the axon of the presynaptic neuron, the action potential reaches the axon terminal synaptic vesicles which migrate toward the synapse. They then release neurotransmitters into the synaptic cleft. The neurotransmitters travel through the synaptic cleft and bind to ligand-gated ion channels on the postsynaptic neuron membrane. The channels open and allow chemicals to enter the cell (i.e. sodium). Then positively charged sodium enters the cell and causes the cell to depolarize. The depolarization spreads down the axon and an action potential is generated. The process then starts over at the axon terminals.

* The axon ends in a cluster of terminal buttons, which are small knobs that secrete chemicals called neurotransmitters.

The central nervous system (CNS) comprises grey matter, which contains neuron cell bodies and white matter, which contains the nerve axons. Most of the nerve axons are concentrically wrapped around by lipid-rich biological membrane, known as the myelin sheath. In the CNS, myelin is produced by oligodendrocyte. a type of glial cell. (Pfeiffer et al., 1993). These electrical insulating, multilamellar membranes significantly increase the electrical resistance, in which to prevent leakage of electrical currents from the axons, as well as decrease electrical capacitance to reduce the ability of the axons to store electrical energy (Shivane &

The structure of a neuron consist of four main components dendrites, cell body also known as soma, synapse and axon. Dendrites collect signals coming in from other cells. The soma is responsible for assimilating signals coming in from the dendrites in order to create a signal traveling unidirectional through the axon. The axon stems from the soma, which

The cell body comprises of the nucleus and other organelles (Ward, 2010). The nucleus contains the genetic code, and this is involved with protein synthesis (He, 2013). The dendrites receive information from other neurons which are located in a close proximity (Kalat, 1995). The terminal of an axon compresses into a disc-shaped structure (Gross, 2010). This is where chemical signals also known as a neurotransmitter permit interaction amongst neurons, by means of a minute gap named a synapse (Martin, Carlson & Buskit, 2013). Both neurons which form the synapse are referred to as a presynaptic synapse (prior to the synapse) and postsynaptic (after the synapse), reflecting the direction of information flow (from axon to dendrite), (He, 2013).

* Interneurons or Pseudopolare (Spelling) cells form all the neural wiring within the CNS. These have two axons (instead of an axon and a dendrite). One axon communicates with the spinal cord; one with either the skin or muscle. These neurons have two processes. (Examples are dorsal root ganglia cells.)

This means that fewer ions are needed to charge and discharge the membrane of the axon. Myelin also clusters ions channels between myelin sheaths. These clusters are called nodes of Ranvier. Myelin allows the action potential of myelinated axons to travel further than unmyelinated axons with the same diameter.

As well as these there are also the axon of the cell which is covered in myelin sheaths which carried information away from the cell body and hands the action potentials, these are small short bursts of change in the electrical charge of the axon membrane through openings of ion channels, off to the following neurons dendrites through terminal buttons at the end of the axons. Whenever an action potential is passed through these terminal buttons it releases a chemicals that pass on the action potential on to the next neuron through the terminal button and dendrite connection. The chemicals that are

The extracellular Na+ did not alter the membrane potential in the resting neuron because the Na+ channels were mostly closed.

As soon as the electrical signal reaches the end of the axon, mechanism of chemical alteration initiates. First, calcium ion spurt into the axon terminal, leading to the release of neurotransmitters “molecules released neurons which carries information to the adjacent cell”. Next, inside the axon terminal, neurotransmitter molecules are stored inside a membrane sac called vesicle. Finally, the neurotransmitter molecule is then discharged in synapse space to be delivered to post synaptic neuron.

The axons are slender processes of uniform diameter arising from the hillock. There is usually only one unbranched axon per neuron.

Are the Nodes of Ranvier found in the CNS or PNS? What is their function? The Nodes of Ranvier is a gap in the insulating sheath (myelin) and the axon of certain neurons that serve to facilitate the conduction of nerve impulses (L. Ranvier, 1878). The action potential caused by one nodes of Ranvier jumps to and is generated at the next node along the axon. It is found in the peripheral nervous system.

In this essay, the role of Chordin in the Spemann’s organiser will be examined, as well as an outline of the Spemann Organiser’s discovery and formation in neural tissue. Chordin has a role in antagonising BMP, forming the dorsal-ventral axis, but it can be controlled if excess Chordin activation occurs. These aspects of Chordin will be examined throughout the following essay.