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Describe the structure of CNS, sensory, connector and motor neurons. 

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Describe the structure of CNS, sensory, connector and motor neurons. 

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CNS structure: The CNS consists of two organs the brain and the spinal cord which are vital for survival.

The spinal cord: The spinal cord is approximately 45cm long and has two different roots the dorsal root and the ventral root. These roots are made up of nerve fibres. The thin long structure goes from the bottom of the brain all the way down and through the backbone.

The brain: The brain is a complex structure with many different parts that control different areas of the body. It is surrounded by the skull for protection against damage and has many distinct lines known as the cortex to increase surface area. It has many nerve cells in order for it to receive and send impulses to other cells and organs around the body. The brain has four lobes: the frontal, parietal, occipital and temporal lobe. Each lobe has many sections and each part has a substantial amount of function throughout the body.

Stem: responsible for automatic and involuntary function such as heart beat, respiration and general homeostasis of the body.

Cerebellum: controls reflexes as well as movement and co-ordination in the body.

Parietal lobe: Helps information from sensory neurons into actual senses like sight, smell, touch.

The pituitary gland: Attached to the hypothalamus and secretes hormones directly into the blood stream.

There are many more important parts of the brain and its structure that have more important functions

https://www.macmillan.org.uk/cancerinformation/cancertypes/brain/aboutbraintumours/thebrain.aspx

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http://www.daviddarling.info/encyclopedia/S/spinal_cord.html
(accessed 24/11/18)

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Explain the role of sensory and motor neurons in a reflex arc.

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Explain the role of sensory and motor neurons in a reflex arc.

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The reflex arc is the simplest pathway to enable a response as quickly as possible. The sensory neuron receives the information at the beginning of the process and the motor neuron passes on the information to the effector at the end of the process.

From when the receptor receives it’s stimulus to the moment the effector offers its response. The first step of this reaction is when the receptor receives a stimulus, it then passes on the message to the sensory neuron. From the sensory neuron the information travels to the interneuron (spinal cord) in the CNS. The interneuron ensures the correct message is being transferred and from there it travels to the more neuron and finally reaches the effector. Sometimes the sensory neuron connects directly to the motor neurone in the spinal cord. An example of this is the knee jerk reflex, it’s known as a mono synaptic response.

The reflex hammer hits the knee and acts as a stimulus. The reaction is very quick as the effector receives the impulse and the leg kicks upwards reacting to the stimulus.
http://multiple-sclerosis-research.blogspot.com/2016/03/cannabis-inhibits-spasticity.html
(accessed 25/11/18)

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Explain the mechanism of transmission of an impulse along a neuron.

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Explain the mechanism of transmission of an impulse along a neuron.

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Neurons send messages to and from the CNS in the form of impulses. Neurons use senses such as sight, sound, taste, touch and smell to pick up information. This is then transferred into electrical signals passing through the CNS from one neuron to another as an impulse. The neuron cell has many features which are important in helping pass on this information throughout the system. Such as dendrites which pick up impulses and pass it on to the cell body, axons do the opposite and carry impulses out of the cell body. The myelin sheath is also usually part of the neutron although it’s not always present, this functions as an insulator coving the axon and increases the speed that impulses pass through the cell. The node of Ranvier are at the joint of the myelin sheath and speed up the passageway further so that impulses can reach their destination quicker. Fibrils at the end of axons help to pass on impulses onto dendrites of the next neuron. Finally between each neuron are synapses, when an impulse reaches a synapse a chemical called neurotransmitter is released. This enables the impulses to pass from one neuron to another.
https://www.dummies.com/education/science/understanding-the-transmission-of-nerve-impulses
(accessed 25/11/18)
T. Derrickson. (2009). principles of anatomy and physiology.

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Compare voluntary and reflex actions and explain the role of the autonomic nervous system.

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Compare voluntary and reflex actions and explain the role of the autonomic nervous system.

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Voluntary actions are slower in comparison to reflex actions. This is because the body is conscious of a voluntary action. The brain is an example of a voluntary action as we use our brain to think of how to react in a situation such as eating. This is considered voluntary as the body has control over whether or not to eat. whereas a reflex is more instant and a quick reaction rather than a conscious decision. Like putting your hand on something hot an instinctively moving it, the brain is not required to think about this response. Therefore the receptor doesn't signal the brain as it would take too long for the response to be sent back to remove the hand.

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Sensory: sensory neuron is found in sensory organs such as the eyes, ears, tongue and skin. The sensory neuron carries nerve impulses to the CNS, when the impulses reach the brain the information is converted into senses like vision, smell, and touch. Not all impulses are sent to the brain some are directly sent to the spinal cord for quick reflexes. The sensory neuron has receptors to get the information it needs also it has myelin sheath which makes the impulses travel more rapidly.

Relay neurons: Found in the CNS and is generally between the sensory and motor neurons and helps enable them to communicate efficiently. The relay neuron needs dendrites in order to receive information and pass it on to the cell body. It also has a pre synaptic terminal which enables action potential to reach the axon. From there the calcium channels open and calcium enters the cell. This enables the calcium to send signals to the vesicles which contains neurotransmitters. The vesicle then moves to the membrane where the neurotransmitters are released and defuses to the synaptic cleft which is bound to the receptors. This is important to make sure that the information passes on to the next neuron.
Motor neuron: motor neurons are found in the CNS and are responsible for the movement of muscles. When the motor neuron is activated they release neurotransmitters that are bound to the receptors on the muscle cell. This will spark a response which ultimately results in movement. The Motor neuron has dendrites which is important so that it can receive and send impulses. It also has the myelin sheath which speeds up the response as well as the node of Ranvier which helps the information reach it destination quicker.
https://www.tutor2u.net/psychology/reference/biopsychology-sensory-relay-and-motor-neurons
(accessed 24/11/18)
https://www.tutor2u.net/psychology/reference/biopsychology-sensory-relay-and-motor-neurons

(accessed 24/11/18)

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The ANS consists of the parasympathetic and the sympathetic systems. The sympathetic system deals with preparing the body for fight or flight. The hypothalamus and the endocrine system coordinate to release hormones such as adrenaline which is needed in this situation. The adrenaline stimulates the body to prepare for action by inducing an increase in heart rate. This increases the circulation of blood in the heart and blood flow to the skeletal muscle which is needed for movement. Other systems that are not important at that time such as digestive system have a reduction of blood flow as they are not useful in this situation and blood is being used by other organs and systems like the skeletal system.

The parasympathetic system works in contrast to the sympathetic system as it counter acts all the reactions caused by the sympathetic system and restores the homeostatic levels of the body such as heart rate, breathing, temperature. Also the hypothalamus stops the production of adrenaline so the body can be restored back to its original form. Blood flow is then returned to normal and all systems can function such as using the toilet.
https://www.sciencedaily.com/terms/sympathetic_nervous_system.htm

(accessed 25/11/18)
T. Derrickson. (2009). principles of anatomy and physiology.