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1.1 Describe the structure of the central nervous system, sensory, connector and motor neurones. 

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1.1 Describe the structure of the central nervous system, sensory, connector and motor neurones. 

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The nervous system consists of two parts, the central nervous system and the peripheral nervous system. The one that I will be discussing today is the central nervous system. What the (CNS) does is it controls how mind and body works. The central nervous system consists the brain and the spinal cord. The spine is held together by the verbal cavity and the brain is held by the cranial cavity.

The central nervous system (CNS) ade up by two types of cells, the glial cells and neurones. The gial cells provides framework for the neurones in the CNS. The nerines is the one that is more important of the two, when it comes its function. It transmits information through the CNS by electrical and chemical signals.

Connector Neuron

Connector neuron is defined as an interneuron which is also known as internuncial neuron, relay neuron, association neuron, connector neuron, intermediate neuron or local circuit neuron. The interneuron is known to be a broad class of neurons which is found in our body. The basic structure of the neuron is where the neurons (nerve cells) has three parts which carries out the functions of communication and integration such as dendrites, axons and axon terminals. It also has a fourth part where the cell body or soma carries out the basic life processes of neurons. This is also where the figure at the right demonstrates a ‘typical’ neuron.

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1.3 Explain the mechanism of transmission of an impulse along a neurone. 

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1.3 Explain the mechanism of transmission of an impulse along a neurone. 

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along the neurone there are nerve impulses that are transmitted because there are electrical charges along the neurone membrane. Due to the difference in charges between the extracellular and the intracellular neurone membrane, the membrane becomes polarised. The idea behind polarisation is done by an excess of na+ on the outside, and an excess of k+ ions on the inside.

Na+ ions are at a HIGH CONCENTRATION outside the membrane. They should be attracted to the – membrane and diffuse inwards, but this is prevented by:

The na+ pump that Is using ATP so that it maintains a the resting potential at around. 70mV

The membrane is impermeable to sodium

The na+ ions move slowly and go through the sodium channels.

In the membrane K+ ions are at a HIGH CONCENTRATION. The k+ ions typically should be attracted to the + extracellular environment and diffuse out, but this ks stopped by

There's a cancelling of potassium ions by the – charge of organic molecules which is on the inside of the axon.

Transmission of a signal can only happen if there is a resting potential of around 70mV. A neurone membrane isn’t permeable to na+ ions, however….

1. When the stimulation of the neurone occurs, the membrane is more permeable to na+ ions, this leads to and opening of “sodium gates/channels”. When this happens more na+ ions enter then can be realised, so the charge that is inside the membrane changes from around 70mV to about 40mV. This is what is called ‘action potential’ where DEPOLARISATION has no charge on the membrane.

2. When the sodium gates/ channels close, the ‘potassium channels’ are opened, making the K+ ions to move outside of the membrane and then inside the extracellular environment. Due to this the membranes charge decreases from + to – of K+ ions. This is the state of ‘resting potential’ where HYPERPOLARISATION causes the resting potential to be lower than the normal value.

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ACTION POTENTIAL

What an action potential is able to do is travel along long distances. When depolarisation happens the outside if the membrane becomes depolarised. In addition a stimulus will allow the sodium channels to open because it is above the threshold level and this will cause the sodium ions from the extracellular membrane to go into the membrane. This results in an action potential which stimulates another sodium ion along the axon to open. What this action potential does is it creates a ‘all or none’ response: there will be no action potential that will take place if the stimulus doesn’t produce depolarisation that is higher than the threshold stimulus. Action potential causes the membrane to become polarised. But the potassium ions and the sodium ions are on the incorrect region of the membrane. The stage of the process is called the refractory period what the axon is non-reactive to the stimulus. So, both the ions are then sent back to the resting potential location by the channels. When they go back to their resting potential, the neurone membrane is ready to respond to another stimulus.

REPOLARSATION

Potassium ions move out if the membrane as sodium ions move in to the membrane and this results in repolarisation where. The membrane is put back to it original polarisation. The potassium ion channels open up that the sodium ion channels close up. Which results in the potassium ions to be out the is the membrane the sodium ions to be inside the membrane

The synapse

When the information goes through one neuron, there is a gap in between the two neurons this is called the synapse.  So when the nerve impulse reaches the synapse at the end of a neuron it can’t pass straight to the other neurons. So what it does it triggers the neuron to release chemical neurotransmitter. What this does is it moves across the gap of the two neurons, and when it reaches the other side. It fits into a receptor that its tailor made for it, similar to a key and lock mechanism. What this does is it changes the chemical signal back to the electrical signal.

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Before the impulse is able to be transmitted there has to an ‘action potential’. The action potential is generated when responding to the stimulus; this involves changes in membrane permeability.

1. The stimulus has to be higher than the minimum value that is called ‘threshold stimulus’ that creates an ‘all or none’ response. The stimulus comes from the external environment such

as changing light/pressure, or from the internal environment like changing blood temperature/pH

2. What causes the membrane to become permeable is the stimulus which lets ions come into the neurone along the gradient which causes DEPOLARISATION

3. The potassium ions exit the neurone to even out the negative charge

4. This is why the ionic movements causes the neurones to become REPOLARISED back to its resting potential.

5. This process can happen again

6. During the opening and closing of the sodium and potassium channels, where there are no exchange of ions, it is called the REFRACTORY PERIOD.

7. As myelinated axons have Nodes of Ranvier, when an action potential (impulse) is transmitted along the axon, the signal goes from node-to-node in order to help the signal travel faster compared to a non-myelinated axon. This is known as SALTATORY CONDUCTION

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1.2 Explain the role of sensory and motor neurones in a reflect arc.

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1.2 Explain the role of sensory and motor neurones in a reflect arc.

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Sensory neurons
What the sensory neurones does is that it conducts impulses from the sense organs and the receptors to the CNS, the sensory neurones are normally myelinated which is known as being fast conducting. Sensory neuron is found in the receptors, they are found in your eyes, tongue, ears and skin. Receptors carries nerve impulses all the way to the brain and spinal cord. As soon as the nerve impulses reach the brain then it’s transformed into ‘sensations’ which are the vision, hearing, touch and taste. However, not every sensory neurons reach the brain because certain neurons stop at the spinal cord which allows quick reflex actions. The sensory neurons is where it carries signal from the outer parts of your body all the way into the central nervous system.

Inter neurons is known to be found between sensory input and motor output/response. Also, the relay neurons are found in the spinal cord and brain where it allows both sensory and motor neurons to communicate.

Motor (Effector)
What the motor neurone does is it conducts impulses from, the CNS to the muscles, glands or the effector organs, it control muscle movements. When the motor neurons are motivated they discharge neurotransmitters that bind to the receptors in the muscles which trigger a response. This is where it leads to a movement. Within the enteric plexus, it controls the gastrointestinal motility, secretion and perhaps absorption.  Performing these functions, the motor neurons is where it acts directly on a huge number of effector cells which includes secretory cells (chief, parietal, mucous, enterocytes, pancreatic exocrine cells), smooth muscle and gastrointestinal endocrine cells. When it comes to the voluntary nervous system the motor neurone is fast conducting which means it is myelinated. When it comes to the automatic nervous system there is no myelin sheath present which means the actions are slow conducting. What they do is they apply smooth muscle in the organs, cardiac muscle in the heart and glands.

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The spine

The spine also known as the backbone or the medulla controls the movement of the body from the bottom of the skull to the pelvis. When you look at the spinal cord it, it is white and firm and it has nerves that extend out of it. These nerves extend to the bones, skin and muscles and aid us to move. The spine has 31 pairs of spinal nerves that split into the following: 12 thoracic, 8 cervical, 5 lumbar, 5 sacral and 1 coccygeal.  The spine is the centre where the body process information that it receives from the brain and t sends this information to the nerves around the body which allows us to move. It also sends signals from the body to the bran which allows us to react correctly. The brain and the body work closely.

The brain

The main part of the encephalon is the brain and it has in it the brain stem and the cerebellum. The brain has hemisphere which is it made up by and an area that is called diencephalon, it is also protected by the cranium. The brain makes up two percent of the bodyweight, however it has hundreds of billions that make it. The brain the largest and complex in the body. I will now be discussing in depth two parts of the brain.

The brain stem

The brain stem is the part of the brain that is connected to the spine and its role is to control the messages being sent from the rain to the rest of the body. Basic body function such as: swallowing, heart rate, breathing, blood pressure and consciousness is all controlled by the brain stem. What the brain stem consists of is the: pons, midbrain and the medulla oblongata.

Frontal lobe

The frontal lobe of the body controls the cognitive skills within the brain. So it’s in charge of problem solving, language, judgement, memory and sexual behaviours. In other words the frontal lobe is the centre of personality and it is what enables us communicate with others.

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

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

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Voluntary actions
Involuntary actions are how our body works. Things like breathing and metalblic system all goes through this action. The involuntary reacts means the body cannot quickly react to quickly to changes, the body will adapt its self to the situation. However, another type action is a reflex and this happens really quickly and unconsciously. The neurons in the body work together in what’s called a reflex arc, and try and work against the impulse before it reaches the brain as that would take too long and for example if a hand id in fire the person would move it straight away, they would not stop and think about it

Autonomic nerves
Three parts make up the autonomic nervous system: the sympathetic system which is in charge of the bodies ‘flight and fight’ mode, the parasympathetic system which looks after the body when it is resting and recuperating and lastly enteric system, which is in charge of the gut.

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To create this assignment, I used a channel called crash course. That broke down the nervous system in a way I would understand and would be able to take it. I also was able to watch the videos on the go so that even if I was doing something that required me to move around, I could play the video in the back ground. It helped me understand what I was writing about.
https://www.youtube.com/watch?v=qPix_X-9t7E
I also used a website which gave me a good understanding of the topic i am writing about.
https://www.cliffsnotes.com/study-guides/anatomy-and-physiology/nervous-tissue/transmission-of-nerve-impulses
the picture that i used to explain and help me with 1.3 was also from that website.