The nervous system

• The nervous system consists of information from the external environment and from the bodys internal environment.
• Neurons have three main parts: dendrites (receive input), cell body (processes information), axon (transmits output).
• Information is transmitted through neurons, which are specialized cells that transmit electrical signals.
• The central nervous system is the control centre for the body; consists of the brain and the spinal cord. The spinal cord connects to the brain, this is done through long lines of individual nerve cells, to every area inside of the body.
• Spinal cord is protected by bones called vertebrae. Bones have a hollow centre in which the spinal cord runs. Transmits information to and from the brain through structures called nerves.
• Automatic system, controls and regulates processes such as heart rate and gut movements. These movements are automatic and are controlled. These are not controlled by us.
• Sensory and motor neurons transmit information from the senses, the eyes ears etc to the brain. Motor nerves help transmit information to the muscles from the brain. Motor neurons transmit information to the muscles from the brain.
• The sensory and motor nerve pathways work together, for example, when picking up something like a pen.
• Perhiperal nervous system is all of the nerves outside of the nervous system. Relays information from the brain and spinal cord to the rest of the body, and then the reverse information from the body to the brain and the spinal cord. Peripheral nerves include autonomic, sensory and motor nerves.
• The cerebral cortex is the wrinkly part of the brain, responsible for thinking and processing sensory information from the body. Their are four lobes, each responsible for processing different types of information. It is made of tightly packed neurons.
• Cerebellum is positioned back of the skull, the cerebellum co-ordinates and regulates muscle activity, for example, gross and fine motor skills such as walking and writing. It can also be involved in the control of muscles to maintain balance.
• Frontal lobes carry out higher level mental processes such as thinking, decision making and also planning.
• Neurons are specialised nerve cells that transmit electrical signals impulses information from one part of the body to another.
• Axons are a long-thread like part of the nerve cell, along which nerve impulses are connected away from the cell body to other cells. There is only one per neuron.
• Dendron (Dendrites) are short, branched structures on the neuron that recieve electrical impulses and carry them towards the body . There are as many as 100 per neuron.
• Synapse is where two neurones meet. A chemical messenger called neurotransmitter passes across the synaptic gap between the axon terminal of one neurone and dendrite of another.
• Reflex arc is an automatic response to stimulus without conscious thought or awareness. For example, when we touch something hot our hand automatically moves away. This happens because there is no time delay between the stimulus and the response.
• Reflex arc is an automatic response to stimuli without conscious thought or awareness.
• The reflex arc consists of sensory receptors, afferent nerves, relay nuclei, efferent nerves and effector organs.
• The myelin sheath is a fatty white substance surrounds the axon. It forms a protective insulating layer and enables electrical signals to transmit quickly efficiently along the nerve cells.
• Information flows from one neuron to another across a synapse. The synapse has a small gap separating neurons. The synapse consists of three elements

  The pre-synaptic membrane


  The post-synaptic membrane

  The gap between two membranes, which is called the synaptic cleft.
• The function of a synapse is to transfer electrical activity from the cell to another.
• Process of a synapse

  1. An electrical impulse travels along an axon. 

  2. This triggers the nerve ending of a neuron to release chemical messengers called neurotransmitters.
  3. These chemicals diffuse across a synapse and transmit signals.
  4. They bind with receptor molecules on the membrane of the next neuron.
• A component of the autonomic nervous system is that it regulates bodily functions that are not consciously controlled such as breathing and also heart rate.
• Central nervous system consists of the brain and the spinal cord. It takes a main role in control and coordination of most body functions.
• Perhiperal nervous system consists of sensory and motor neurons that transmit nerve impulses to and from the brain and the spinal cord.
• The spinal cord is connected to the brain by nerves. Allows communication between the brain and also the body.
• A component that has a role in the regulation of body temperature and thirst is the hypothalamus.
• Their are two components that help with decision making and processing information. Those are the cerebal cortex and also the frontal lobes.
• A component that has a role in automatic functions such as breathing and swallowing is the medulla.
• The structure of a healthy myelin sheath is that it has a layer around the schwann cells, it is lined with fatty substance, and is wrapped around an axon. And also, has nodes of ranvier.
• The symptoms of MS are fatigue, muscle spasms, numbness and tingling, problems with mobility, tremors, pain, depression and anxiety, problems with thinking, loss of balance, bladder issues, blurred vision, memory loss/cognitive issues, and also coordination issues.
• The damage to the myelin sheath can cause autoimmune diseases. White blood cells attacking the myelin sheath. Inflammation of the area. Lesions that occur. Scar tissue that forms. Axon, no longer being protected. A breakdown of the insulating layer. A disruption of nerve impulses. A slowing down of messages and also impulses. A stopping of transmission of impulses completely. This can lead to permanent nerve damage.
• The pancreas is where insulin is produced. Insulin is then released into the blood. This insulin can then lower blood glucose levels. This can then allow blood glucose to move into cells, this causes the liver to convert blood glucose and glycogen and stores it. It can also stop and reduce the release of insulin if glucose levels are low. Glucagon can be produced. Glucagon can raise blood glucose levels. Glucagon can cause the liver to convert stored glycogen into glucose and release blood.
• The CNS is made up of the spinal cord. The brain is the centre of all conscious awareness, the brain also has an outer layer, the cerebal cortex, this is very developed inside of humans. Brain has two hemispheres: The spinal cord is the extension of the brain. It is responsible for reflex actions. 
• The PNS transmits messages via millions of neurons to and from the nervous system. The PNS is further subdivided into:


  The somatic nervous system

  The autonomic nervous system
• This is the part of the PNS that is responsible for carrying sensory as well as motor information to and from the spinal cord.

  It is made up of 12 pairs of cranial nerves from the brain, 31 pairs of spinal nerves and all of their branches.
• The autonomic nervous system has vital functions such as breathing, heart rate, digestion, sexual arousal and also stress responses.
• Autonomic Nervous System (ANS) - controls involuntary functions such as heart rate, breathing, digestion, pupil dilation etc. There are two divisions within ANS; sympathetic division and parasympathetic division.
• Somatic Nervous System (SNS) - controls voluntary movements such as walking or writing. Sensations like touch, temperature, pressure, pain and vibration.