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Crash course is an educational youtube channel that includes animation and well-researched information. I believe it is reliable. It was able to provide an in-depth description of the structure of the brain which is a part of the criteria for the sturcture of the central nervous system.

Green, H. (2015) Central Nervous System [Online] Available from: https://www.youtube.com/watch?v=q8NtmDrb_qo [Accessed 13/12/2017]

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The website BIotopics is self created. There weren't any references provided which makes it an unreliable source. It provided a table highlighting the differences between voluntary action and reflex action. However it was lacking in detail.

Steane, R. (n.d.) Voluntary and reflex actions [Online] Available from: http://www.biotopics.co.uk/newgcse/voluntaryReflex.html [Accessed 13/12/2017]

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Reflex action is initiated by stimulation of receptor, e.g. skin.
Impulse passes up dendrite and axon of a sensory neuron and on (via synapse) to relay neuron in grey matter near the centre of the spinal cord which passes impulse directly and on (via synapse) to a motor neuron.
Stimulus, neurones, action all on the same side of the body.
Only 3 cells, 2 synapses - therefore quicker. Secondary information passes up the spinal cord to the brain, so the subject is aware of the event.

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Knowwhatuknow41 is a youtube channel that covers educational topics. The information given is reliable enough but can be insufficient in terms of detail. It managed to cover a basic description of the sensory neuron, interneuron, and motor neuron. it also managed to give a brief description of the role of each neuron in the reflex arc but lacking in detail.

Knowwhatuknow41 (2014) Types of Neurons and the Reflex Arc [Online] Available from

https://www.youtube.com/watch?v=M1E9Lm16cUs [Accessed 13/12/2017]

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Crash course creates high quality educational videos by transforming textbook information into fast-paced, animated video. Their content is supported by many other sources and is quite reliable.

The video described the transmision of an impulse in great detail which meets the criteria.

Green, H. (2015) The Nervous System, Part 3 - Synapses [Online] Available from: https://www.youtube.com/watch?v=VitFvNvRIIY Accessed:13/12/2017

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Crash course creates high quality educational videos by transforming textbook information into fast-paced, animated video. Their content is supported by many other sources and is quite reliable.

The video described the autonomic nervous system with enough detail to meet the criteria.

Green, H. (2015) Autonomic Nervous System [online]. Available at: https://www.youtube.com/watch?v=71pCilo8k4M Accessed: 13/12/2017

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Interneurons are found in the CNS. They are stimulated by impulses from sensory neurons and other interneurons. they have short dendrites and short or long axons. More than one inter neuron can interact with the sensory neuron. Interneurons form an immediate link in areas where there are many cross connections and a tremendous number of connections possible and that would be in places like the spinal cord and the brain (2.14)

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There are many sensory receptors that has specific stimuli that they respond to.
A stimulus such as a pinprick causes sensory receptors to generate nerve impulses that travel to the spinal cord a (3.11)

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The parasympathetic "talks you down and effectively undoes what its foil did" @2.03. it is "for resting and digesting and responsible for maintaining your body and conserving energy for later" @2.54. Parasympathetic nerve fibres " both above and below where the sympathetic ones do" They are craniosacral. (@3.50).
Most parasympathetic ganglia are found " way out of the spine, near and even inside of their effector organs. it uses more strategic and specific signals" (@5.00).
Parasympathetic "preganglionic fibres are a lot longer. they extend from the cranium and sacrum where they start, out to the effector, where they reach their ganglion. from there their postganglionic fibres are really short, just long enough to communicate with their effector." (@6.27)
"The parasympathetic doesn't require urgent, all hands on deck communication" (@7.06).

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The sympathetic amp you up and prepare you for activity (@1.57). It is what sounds your internal alarm bells. it is the hardware behind the famous fight or flight response (@2.45). It is synonymous with stress (@2.50). Sympathetic fibres are thoracolumbar - meaning that they originate from between your thoracic vertebrae and lumbar vertebrae. The network of nerves coming from the middle of the spine allow quick coordination of the function of many major organs at once (@3.27).
Sympathetic ganglia "are found closer to the spinal, because in those fight or flight moments of high excitement or activity, they need to be able to send a single message far and wide. this allows excitatory signals travelling in the ganglion near the spine can trigger action potentials in a whole bunch of other neurons that lead to many different effectors" (@4.37).
In the sympathetic nervous system, the preganglionic fibres are much shorter than postganglionic ones. (@6.00).
"It is set up in such a way that one stress signal can be sent down one path and could trigger a response in many effectors at once" (@6.53).

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This video from crash course describes the Autonomic system as "the branch of your peripheral nervous system that regulates the internal functions of your internal organs, like heart and stomach, and also control smooth and cardiac muscles, and your glands" @0.50
"its effects on your organs and muscles and glands are not consistent" @1.12
"The autonomic system is constantly making involuntary, fine-tune adjustments to your body, based on what signals your central nervous system is picking  up" @1.20 Examples include "changing body temperature, sending extra blood to a particular area, slowing heartbeat, or tweaking your stomach secretion" @1.28.
In the autonomic nervous system has "two divisions that serve the same organs, but create opposite effect in them" @1.50.

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Through a range of sensory receptors, stimuli is detected and relayed back to the brain or spine.

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Autonomic Nervous System: Crash Course Anatomy & Physiology #13

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Central Nervous System: Crash Course Anatomy & Physiology #11

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The Nervous System, Part 3 - Synapses!: Crash Course Anatomy & Physiology #10

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It made out of jelly-like nervous tissue that is extremely susceptible to injury.

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The brain sorts out all sensory information and gives orders. it also carries out most complex functions like thinking and feeling and remembering. (2.25)
It made out of jelly-like nervous tissue that is extremely susceptible to injury. The brain is divided in specialise regions that may or may not interact with each other to produce a given action(3.15). The cerebellum coordinates muscular activity. The brainstem plays a vital role in relaying information between body and high regions of the brain. It has three parts: the midbrain, the pons, and the medulla oblongata which maintains the most basic functions of the body. However, the midbrain carries out higher level functions. it is the one that receives and processes sensory information and send out reflexive motor signals. The midbrain also passes the message along to the cerebral cortex which does the processing of information.
The diencephalon containing the hypothalamus, thalamus, epithalamus, and mammary body, regulate homeostasis, alertness, and reproductive activity. Part of the limbic system can also be found here.
The cerebrum is the largest region of the brain and performs the highest function. it is made up of the wrinkled, outer layer of grey matter called cerebral cortex and the inner squishy layer of white matter beneath it.
The brain has creases called gyri, and larger grooves called sulci. The two hemispheres communicate through the corpus callosum.
the frontal lobe governs muscle control and cognitive functions. it is also important in language comprehension and speech. The occipital lobe processes bright visual cues. parietal lobes processes sensations of touch, pain and pressure. The temporal lobe sorts out auditory information including language.

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The Central nervous system consists of the brain and the spinal cord.

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In the voluntary section, we have the skeletal muscle. (0.20)
Voluntary action is initiated in (cerebral cortex of) brain - due to thought?
Impulse passes to motor area (on side of cerebral cortex) and thence down spinal cord to motor neuron.
Impulse passes over to opposite side of body. i.e left side of brain controld right side.
Many cells and synapses, and longer pathway - therefore slow.

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A reflex allows the body to make a quick response to harmful stimulus before we're even consciously aware of the problem (3.45)

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Comparison of vuluntary and reflex actions

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Comparison of vuluntary and reflex actions

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The role of the peripheral nervous system is to relay information from and to the Central Nervous system.

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The cell that's sending the signal is the presynaptic neuron, and it transmits through a knob-like structure called the presynaptic terminal, usually the axon terminal. This terminal holds a whole bunch of tiny synaptic vesicle sacs, each loaded with thousands of molecules of a given neurotransmitter. the receiving cell meanwhile, is, yes, thankfully, the postsynaptic neuron, and it accepts the neurotransmitters in its receptor region, which is usually on the dendrite or just on the cell body itself. And these two neurons communicate even though they never actually touch. Instead, there's a tiny gap called a synaptic cleft between them - less than five-millionths of a centimetre apart. Messages that travel via chemical synapses are technically not transmitted directly between neurons like they are in electrical synapses. Instead, there's a whole chemical event that involves the release, diffusion, and reception of neurotransmitters in order to transmit signals.(4.38)
When an action potential races along the axon of a neuron, activating sodium and potassium channels in a wave, it eventually comes down to the presynaptic terminal and activates the voltage-gated calcium channels there to open and release the calcium into the neuron's cytoplasm. This flow of positively charged calcium ions causes all those tiny synaptic vesicles to fuse with the cell membrane and purge their chemical messengers. And it is these neurotransmitters that act like couriers diffusing across the synaptic gap, and binding to the receptor sites on the postsynaptic neuron. When the neurotransmitter binds to the receptor, the chemical signal is converted into an electric signal again. depending on which neurotransmitter binds to which receptor, the neurons might either get excited or inibited. Excitatory neurotransmitters depolarise the postsynaptic neuron by making the inside of it more positive and bringing it closer to its action potential threshold, making it more likely to fire that message on to the next neuron. But an inhibitory neuron hyperpolarises the postsynaptic neuron by making the inside more negative, driving its charge down - away from its threshold. so not only does the message not get passed along, its now even harder to excite that portion of the neuron. The likelihood of that postsynaptic neuron developing an action potential depends on the sum of all the excitations and inhibitions in that area. (5.35)
After neurotransmitters deliver their message, they just sort of pop back out, and then either degrade or get recycled. Some kinds diffuse back across the synapse and are immediately re-absorbed by the sending neuron, in a process called reuptake. Others are broken down by enzymes in the synaptic cleft, or sent away from the synapse by diffusion.(7.27)

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Motor neurons have bodies inside the CNS (0.33).
Motor neurons transmit impulses away from the CNS to muscles and glands. they are stimulated by inter neurons. Motor neurons have short dendrites and long axons (2.53)

Role of motor neuron in reflex arc:
Motor neurons convey nerve impulses from the spinal cord to a skeletal muscle which contracts the hand and pulls away. (3.23)

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Sensory neurons have cell bodies outside the CNS (0.27)
Sensory neurones receive information and relay impulses toward the CNS. The sensory neuron has many dendrites that are sensitive to different stimuli. For example, those in the skin are sensitive to touch, pressure, heat, cold, and pain. When such stimuli reach a threshold level, a nerve impulse is generated in the sensory neuron that relays this information to the CNS. The sensory neuron has long dendrites and short axons which puts the body very close to the CNS. When sensory neurons form nerves, cell bodies cluster to form a ganglion near the CNS.   (0.37)

Role of sensory neuron in the reflex arc:
When we prick our finger, the impulse travels along the sensory neuron to the interneuron. (3.53)
But at the same time, a much greater distance is covered with another interneuron transmitting the information from the sensory neuron up to the brain. (4.02)

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A reflex arc is a neural pathway caused by a stimulus detected in sensory receptors and relayed unto the grey area of the spine to trigger a reflex action.