It contains myelinated axons or nerve fibers. Cell bodies of some neurons are also present in the whiter matter. The collection of cell bodies inside the white matter of the cerebral cortex is called a nucleus. Examples of nuclei are the red nucleus, nuclei of the cranial nerves, etc.
Neurons present in the brain and other parts of the nervous system communicate via synapses. A synapse is a site where the nerve impulse is transmitted from one neuron to another neuron or a non-neuronal cell. Based on the mechanisms by which they transmit a nerve impulse, synapses can be divide into two types; electrical synapses and chemical synapses. There are three components of a neuronal synapse; a pre-synaptic terminal, synaptic cleft, and a post-synaptic neuron.
Based on the structural components participating in the formation of a chemical synapse, they can be classified as follows;. Neuroglial cells are the supporting cells present in the brain. They are ten times more abundant than the neuronal cells in the human brain. The glial cells provide support and nutrition to the neuronal cells. They also play a role in the survival or protection of the neurons present in the brain.
They can be considered as a substitute for connective tissue in the brain. Different types of glial cells are present in the brain. The most important glial cells are mentioned below. The human brain consists of billions of neurons that are interconnected via neuronal synapses. Cells other than neurons called the glial cells are also present to proivide support to the neurons. A neuron consists of a cell body and cellular process. The cell body contains the nucleus in the center and other organelles for the synthetic needs of the cell.
The complex system of rough endoplasmic reticulum and polyribosomes is also present called the Nissl granules. They are exclusive to the cell body of neurons. Dendrites are the slender processes that show abundant branching and carry nerve impulses to the cell body of neurons.
Dendritic spines are the sites for synapse formation on dendrites. Axons are the cylindrical processes that carry nerve impulses away from the cell body of neurons. They do not show branching and have a constant diameter throughout their length. They are the myelinated nerve fibers. Neurons can be divided into sensory, motor, and interneurons. The neurons in the brain are arranged into gray matter and white matter. In a chemical synapse, neurotransmitters are released by the pre-synaptic cells that diffuse through the synaptic cleft and excite the post-synaptic neuron.
The synapses present in the brain might be axoaxonic, axosomatic, or axodendritic. Glial cells replace the connective tissue in the brain. They provide support, nutrition, and protection to the neurons. They are involved in myelin sheath synthesis, providing metabolic support, regulating the flow of CSF providing protection from pathogens. Home About. Table of Contents. Introduction Brain is the central control system of the body.
Structure of Neuron Although different types of neurons are present in the brain, the basic structure of all the neurons is always the same. Cell Body The cell body of a neuron serves as the synthetic or trophic center for the entire cell. Nucleus The nucleus occupies is present in the central portion of the cell body of neurons. Rough Endoplasmic Reticulum The cell body of the neurons is responsible for protein synthesis. Golgi Apparatus Recall that the Golgi apparatus is responsible for the packaging of the proteins.
Mitochondria Mitochondria serve as the powerhouse of neurons. Cytoskeleton The cytoskeletal framework provides structural support to the cell body as well as cellular processes of neurons. Inclusion Bodies Inclusion bodies are the residual bodies left in the cell body after lysosomal degradation. Dendrites These are the cellular processes that carry nerve impulses towards the cell body of neurons. Axons These are the cellular processes that carry nerve impulses away from the cell body of neurons.
Types of Neurons Based on the functions performed by neurons, they are divided into three basic types; sensory neurons, motor neurons, and interneurons. Sensory Neurons These neurons are responsible for identifying an environmental stimulus or a stimulus arising within the body. Motor Neurons Motor neurons are responsible for exciting the skeletal muscles to perform the desired action.
Interneurons These neurons receive information and process it. Arrangemet of Neurons The neurons have different arrangements in different parts of the brain. Grey Matter The grey matter is present in the outer portion of the cerebral cortex. White Matter It is the inner portion of the cerebral cortex.
Synapse Neurons present in the brain and other parts of the nervous system communicate via synapses. Functional Classification Based on the mechanisms by which they transmit a nerve impulse, synapses can be divide into two types; electrical synapses and chemical synapses.
In an electrical synapse, the cytoplasm of two or more cells is interconnected via gap junctions. Thus, the ions can freely move from one cell to the other. In this way, depolarization in any one cell causes depolarization of all the connected cells. These synapses are seen in cardiac myocytes. In a chemical synapse, the nerve impulse is transmitted from one cell to the other via chemical substances called neurotransmitters.
Most of the neuronal synapses re chemical synapse. The structure of such a synapse is mentioned below. Structure There are three components of a neuronal synapse; a pre-synaptic terminal, synaptic cleft, and a post-synaptic neuron. An axonal terminal forms the pre-synaptic terminal of a synapse. When a nerve impulse arrives at a presynaptic terminal, it causes synaptic vesicles to fuse with the plasma membrane.
In this way, the neurotransmitters present in the vesicle are dumped into the synaptic cleft. The synaptic cleft is a space between the pre-synaptic and post-synaptic neurons. The neurotransmitters released into the cleft diffuse through it to reach the post-synaptic neuron. Neurotransmitters remain in cleft for only some time. An action potential travels the length of the axon and causes release of neurotransmitter into the synapse.
The action potential and consequent transmitter release allow the neuron to communicate with other neurons. Neurotransmitter — A chemical released from a neuron following an action potential.
The neurotransmitter travels across the synapse to excite or inhibit the target neuron. Different types of neurons use different neurotransmitters and therefore have different effects on their targets.
Synapse — The junction between the axon of one neuron and the dendrite of another, through which the two neurons communicate. QBI newsletters Subscribe. Help QBI research Give now. Skip to menu Skip to content Skip to footer. Site search Search. Site search Search Menu.
Action potentials and synapses. Home The Brain Brain functions. At the junction between two neurons synapse , an action potential causes neuron A to release a chemical neurotransmitter. Neurons have specialized projections called dendrites and axons.
Dendrites bring information to the cell body and axons take information away from the cell body. Information from one neuron flows to another neuron across a synapse. The synapse contains a small gap separating neurons. The synapse consists of:. Hear IT! For communication between neurons to occur, an electrical impulse must travel down an axon to the synaptic terminal.
At the synaptic terminal the presynaptic ending , an electrical impulse will trigger the migration of vesicles the red dots in the figure to the left containing neurotransmitters toward the presynaptic membrane.
The vesicle membrane will fuse with the presynaptic membrane releasing the neurotransmitters into the synaptic cleft. Until recently, it was thought that a neuron produced and released only one type of neurotransmitter.
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