# data[].attributes.headline
1.1 The structure of sensory, motor, connector neurons

# data[].attributes.subject
1.1 The structure of sensory, motor, connector neurons

# data[].attributes.body
Neurons are the basic building block of the nervous system.
human body is made up of three main types of neurons.
All three types are made up of similar parts, however each one of these neurons has different function and structure in the body. the location of the neuron and the role that it has in the body are the main two factors that can identify the type of the neuron.
the three main types are: The sensory neuron, the motor neuron, and the relay or the connector neuron.
The simple structure of a neuron is sectioned into three main compartments: the cell body or the soma, the dendrites, and the axon.
1.The cell body is found in each three neurons and is consists of cytoplasm and the nucleus, however the size of the cell body can differ from type to type.
2. The dendrites are short projections that extend from the cell body and they can be found in both connector and motor neurons only. The dendrites in the connector neuron are more slender, short, and numerous, compared to the dendrites in the connector neuron.
3.The axon is  a long narrowed, thread-like projection of the neuron. It carries nerve impulses away from the cell body towards the axon terminals where the neuron ends. There are nodes on the axon called nodes of Ranvier and can be found in both sensory and motor neurons only. A myelin sheet covers the whole axon which insulate the axon and it helps the electrical impulse to travel faster along the axon, yet it is not existed in the sensory neurones.
The axon terminal connects the neuron with other neuron or directly to organs.

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# data[].attributes.body
Reflex action is un unconscious response from the body toward an unexpected, external stimulus.

# data[].attributes.headline
1.1 The structure of sensory, motor, connector neurons

# data[].attributes.subject
1.1 The structure of sensory, motor, connector neurons

# data[].attributes.body
Neurons are the basic building block of the nervous system.
human body is made up of three main types of neurons.
All three types are made up of similar parts, however each one of these neurons has different function and structure in the body. the location of the neuron and the role that it has in the body are the main two factors that can identify the type of the neuron.
the three main types are: The sensory neuron, the motor neuron, and the relay or the connector neuron.
The simple structure of a neuron is sectioned into three main compartments: the cell body or the soma, the dendrites, and the axon.
1.The cell body is found in each three neurons and is consists of cytoplasm and the nucleus, however the size of the cell body can differ from type to type.
2. The dendrites are short projections that extend from the cell body and they can be found in both connector and motor neurons only. The dendrites in the connector neuron are more slender, short, and numerous, compared to the dendrites in the connector neuron.
3.The axon is  a long narrowed, thread-like projection of the neuron. It carries nerve impulses away from the cell body towards the axon terminals where the neuron ends. There are nodes on the axon called nodes of Ranvier and can be found in both sensory and motor neurons only. A myelin sheet covers the whole axon which insulate the axon and it helps the electrical impulse to travel faster along the axon, yet it is not existed in the sensory neurones.
The axon terminal connects the neuron with other neuron or directly to organs.

# data[].attributes.headline
1.1 The structure of the central nervous system 

# data[].attributes.subject
1.1 The structure of the central nervous system 

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the central nervous system is the controller of the body's voluntary and involuntary functions. it is responsible for sending, receiving, and interrupting information from all part of the body.
it consists of two major
structures:
1. the brain
2. the spinal cord
the brain is responsible for coordinating consciously and unconsciously body functions
the spinal cord works as a conduit for signals between the brain and the rest of the body. it also controls simple reflexes without an input from the brain

both brain and spinal cord are consisted of nervous tissue, which it has a consistency of jelly. Therefore, a special protection is required to prevent any physical damage.
The whole central nervous system is sheathed with bones. the spinal cord runs within a canal  through the vertebrae and it called the vertebral column. in the other hand, the brain is within unmovable bones called the cranium.
A colourless liquid is found within the bony case and it is called The Cerebrospinal fluid. it is produced by special structures of the brain and provides extra protection to the CNS as it is bathed in that fluid. it also provides a special chemical environment for nervous tissues.
The central nervous system is made up of two general types of tissues.
1.The white matter: is mostly consists of axons, which is the reason for the whiteness, because of the myelin sheathing of the axons.
2. The grey matter: consists of axons, nerve cell bodies, and dendrites. It is rich in cell bodies, therefore it earned that grey colour, which is fairly pink-grey in a clear vision.

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A clear picture that demonstrate the different structure of the three types of neurons.

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1.3 The mechanism of transmission of an impulse along a neuron

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1.3 The mechanism of transmission of an impulse along a neuron

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Neurons are the passage network for impulse to travel along the organism to reach its destination. When a stimulus triggers the neuron's cell membrane, an action potential process start to occur within the neuron. At this stage, the cell membrane is  polarized and become penetrable to sodium ions. The sodium ion electrochemical gradient start to open and allow more sodium ions to diffuse into the neuron, and that makes the interior of the neuron les negative, but not completely positive either. If the different charge is enough, then the potential difference will reach the threshold, where the neuron reach is
--55mV. that will trigger the voltage gated channels of sodium ions to open and allow more sodium ions to diffuse. This stage is called depolarization and at this stage the neuron is positive in the inside. Sodium ion voltage gated channels close and the cell membrane start to be more permeable to potassium, that leads the potassium ion voltage gated channels to open and allow potassium ions to diffuse out of the neurone down the potassium ion concentration gradient. That happens through the repolarization. Potassium channels take more time to close, that cause to have slightly more potassium ions on the outside than it has sodium on the inside This causes the membrane potential to drop slightly lower than the resting potential, that effects the membrane to be hyperpolarization. This period does not last for a long time. At this stage, the impulse has arrived to its destination and the action potential process is finished and the cell membrane returns to the rest potential.

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1.2 The role of sensory and motor neurons in a reflex arc

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1.2 The role of sensory and motor neurons in a reflex arc

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a reflex is an unconscious, quick response from the body toward any unexpected harm.
There are two types of reflex. A simple reflex is when the brain is not aware of the initial response, however a signal will be sent to the brain after the initial response to prosses if there is any action needed after. Conditioned reflex involve prior thought or learning, but the body still respond subconsciously.
A simple reflex arc happens for example when a person touches a hot surface. The fingers are stimulated by the heat causing a pain sensor to create a nerve impulse. The nerve impulse travels along the dendrite of the sensory neuron to reach a physical gap called synapse. The nerve impulse then is transmitted through the synapse by chemical transmitter and reach the relay neuron. Here, the relay neuron takes the nerve impulse through the grey matter of the back of the spinal cord. then, the impulse reaches the ventral surface of the spinal cord, which is the front pat of it. The last step has been reached, when the impulse arrived at the cell body of a motor neuron, then to the axon of the motor neuron where the pathway of the axon is covered with Schwann cells and myelin sheaths which what makes the impulse travel faster. The last stop is the muscle where the motor neuron is terminated. the motor end bulbs release acetylcholine and diffuse across into the surface of the muscle, causing the muscle to depolarize and contract.
During this whole procedure, another component from the sensory neuron synapses with an ascending neurons, which take the information to the brain in order to alert the brain about the surrounding actions that have been taken, however, it reaches the brain after the reflex is happened so the brain can prosses all the information and work out if there is any further action is needed