First Aid Anatomy and Physiology

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FIRST AID ANATOMY AND PHYSIOLOGY To be an effective first aider, it’s important to have a good understanding of anatomy and physiology and how this can be affected by certain injuries and illnesses. This eBook revises a lot of what you may have already learnt or be about to learn in your Fitness or Massage program. The body is made up of the following 11 organ systems (remember the acronym SLINC MURDER): S - skeletal L - lymphatic I - integumentary N - nervous C - cardiovascular M - muscular U - urinary R - respiratory D - digestive E - endocrine R - reproductive

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THE CENTRAL NERVOUS SYSTEM (CNS) The CNS consists of 2 main axes – the central (brain and spinal cord) and the peripheral (the 12 cranial nerves and 31 pairs of spinal nerves). In simple terms, the CNS is the command centre that controls everything that happens in the body, and is also the main storage compartment for everything we know or have experienced. The peripheral nervous system (PNS) uses all of your senses (touch, taste, smell, hearing, sight, proprioception, nociception etc.) to feed information to the CNS about what you are feeling and experiencing. The CNS is the boss, and the (PNS) is the worker. The CNS has two main autonomic states; the sympathetic (fight and flight) and the parasympathetic (rest and digest). These are hangovers from evolution – they are what ensured our survival.

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Sympathetic Nervous System (SNS) The SNS is our fight and flight system. This can also be described as our stress response. Imagine, you have just woken up and you need to go to the loo. With bleary eyes you get out of bed and waddle to the bathroom. As you enter the hallway you see a lion standing there with a hungry look in his eye. He roars at you!! What happens? This is what people generally call an “adrenaline rush”; you feel your heart start pounding in your chest, your respiratory rate speeds up, your muscles tense ready to run and your pupils dilate to let lots of light in. You could hear a pin drop and you can smell the lion’s coarse mane. All of your senses become finely tuned to the situation and your brain starts processing really quickly to get you out of there. This is a much exaggerated example of SNS activation. When your brain recognises that you need a boost, the CNS sends impulses to glands and smooth muscles and tells the adrenal medulla to release hormones such as adrenaline and noradrenaline. This causes effects such as an increase peripheral vascular resistance (so more blood gets back to the heart for increased cardiac output), and increase in RR to increase oxygen supply to heart and lungs and an increase in HR to pump the blood back out to the working muscles. In a regular setting (let’s say a footy game) this SNS activation is a great thing. But in a first aid emergency (let’s say, someone has had their leg chopped off!!) it can be really bad as it can make the condition worsen (leg chopped off, means a lot of bleeding, SNS activation makes HR go up, so without direct pressure the casualty may bleed even more).

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Parasympathetic Nervous System (PaNS) The PaNS is the opposite of the SNS, it is responsible for resting, relaxation and digestion. Imagine you have had a long day in the gym; you are wired and over excited from all the great lifts you have been helping your clients do and buzzing about their great results. You need to go to bed because you have an early start tomorrow. You go through your usual night time ritual, brush your teeth, put your favourite PJs on, get a glass of water and climb under the covers. You read a book for a few minutes, but gradually feel your eyes blinking more, your breathing has slowed down, your body feels heavy and you drift off to sleep. This is the PaNS at work. As you rest, your PaNS works (through the release of hormones such as dopamine) to slow down your body processes, HR , RR, BP lowers and your level of awareness falls. The PaNS also comes into play when you have eaten a meal. Chewing stimulates the vagus nerve (the main PaNS cranial nerve), which kick-starts all of the digestive processes – peristalsis in the stomach, bile release into the duodenum, motility through the small intestine. You can also stimulate the vagus nerve manually; performing the valsalva manoeuvre (holding your breath and bearing down, like bodybuilders do when performing a really heavy bench press) will kick the PaNS into gear.

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Nervous System in the Primary and Secondary Survey As a first aider, understanding the PaNS and SNS is vital to providing a good level of care. We want to keep our casualty as relaxed and calm as possible, but we need them to stay awake and alert so they can communicate with us. Reassuring a casualty that help is on the way, they are safe, and good people are helping them goes a long way to managing an emergency. The most important thing a first aider can do, in the absence of all other options is to reassure the casualty, make them as comfortable and safe as possible. This avoids any unfavourable SNS/PaNS activation that may make a condition worsen. 1 Nervous system primary survey R - response: we are looking at a casualty’s level of consciousness. Use AVPU or COWS to help you: 2 Nervous system secondary survey Pupils – are they equal and reactive to light? Dizzy/lightheaded Headache Limb strength (unilateral or bilateral weakness) Numbness or tingling anywhere Speech disturbances – slurred Facial or limb paralysis

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THE CARDIOVASCULAR SYSTEM (CVS) The CVS consists of the heart, blood vessels and the blood. Its primary role is the delivery of oxygen to and removal of carbon dioxide from the tissues in the body. The blood begins its journey in the left ventricle of the heart, where it is expelled into the aorta. From the aorta it travels through the lesser arteries, arterioles into the capillaries where perfusion occurs into and out of the tissues. This is all an active process – the force of the heart’s contraction drives the flow of blood through this system. As the blood leaves the capillary beds it returns to the heart via the venous network. By now the force of the heart’s contraction has gone and the veins rely on their system of valves and movement of the body to work the blood back up toward the right atria of the heart. Blood moves into the right ventricle and leaves the heart on its journey through the lungs, where carbon dioxide is exchanged for oxygen. Re-oxygenated blood then heads back to the left side of the heart to enter the left atria and flow into the left ventricle to start the loop all over again! So, what’s in the blood? Firstly we have red blood cells – they are what give blood its colour. The red blood cells (RBC) carry around 250 million haemoglobin molecules, who each bind to 4 oxygen molecules. This means that each RBC is capable of carrying 1 billion oxygen molecules to the tissues! The RBC’s also have an affinity for carbon dioxide, and will carry these molecules to the lungs for expiration. There are also white blood cells (WBC) who are involved with immune responses. Then there are platelets – these are like mini band-aids that can clot together to create patches where an injury has been sustained. All of these cells float in plasma, which is a fluid with a low viscosity made mostly of water. The heart is a remarkable organ. It sits in the middle of the chest (mediastinum), with 1/3 on the right of the sternum, and the remaining 2/3 on the left of the sternum. The heart cells (myocytes) have the ability to create their own electric signals which follow a set pathway, causing contraction of the healthy heart (heart beats!). In an unhealthy heart this flow of electricity becomes disrupted or disorganised. Often this is a result of a heart attack (myocardial infarction). The heart has its own network of coronary arteries to feed the heart tissue, this can be altered in a person who has a poor diet, sedentary lifestyle, diabetes, high blood pressure or a family history of heart disease. Fatty deposits sit in the coronary arteries reducing the diameter of the vessel and decreasing the amount of blood that can get through. This can lead to the myocytes being starved of oxygen and eventually dying.

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Cardiovascular System in the Primary and Secondary Survey 1 CVS primary survey C - compressions – good quality compressions in the middle of the chest pump the blood from the left ventricle out to the body when the heart is no longer able to contract in a coordinated fashion. 2 CVS secondary survey HR – how many beats per minute? BP – what is the pressure in the casualty’s vessels when the heart is contracted (diastole) and at rest (systole) Capillary refill – an indication of the casualty’s perfusion (