The Physiological Effects of Alcohol on the Human Body

The Physiological Effects of Alcohol on the Human Body
Introduction: In this essay I?m going to write about the effects in which alcohol has on various organs in the human body. I will also describe how alcohol affects humans psychologically. This will demonstrate clearly the impact that alcohol has towards human beings. What is Alcohol? The scientific name for alcohol is Ethanol; CH3CH2OH, a group of chemical compounds whose molecules contain a hydroxyl group, -OH, bonded to a carbon atom. Pure Ethanol is a colourless liquid. Alcohol and Your Brain: In order to understand how alcohol can effect the brain you need to be able to understand how the brain works. (See Figure 1) Figure 1 Lateral surface of left half of brain
1. Logitudinal cerebral fissure 2. Crebellar hemisphere 3. Cerebellar vermis 4. Olfactory trigone 5. Anterior perforated substance 6. Olfactory bulb 7. Olfactory 8. Optic nerve Base of brain [image] Figure 1 cont. 9. Optic chiasma 10. Hypophysis 11. Mamillary body 12. Pons 13. Medulla oblongata 14. Lateral sulcus 15. Central sulcus Median section of brain [image] 16. Precentral gyrus 17. postcentral gyrus 18. Anterior commissure 19. Corpus callosum 20. Septum pellucidum 21. Fornix 22. Interthalamic adhesion Cerebral hemispheres from above [image] 23. Third ventricle 24. Fourth ventricle 25. Cerebral aqueduct 26. Epiphysis or pineal body 27. Lamina tecti or section of midbrain Each section of the brain has a different role to play. (See Figure 2) Figure 2 1) is the frontal lobe, responsible for emotional control, cortical control of micturition (bladder function), thought, reasoning, behaviour, memory. In the frontal lobe (9) is Broca?s area for the motor part of speech, (8) is the premotor cortex ? this produces similar movements to the motor cortex when links to this cortex are intact. (2) is the motor cortex (controls movement). (4) is the parietal lobe, responsible for intellect, thought, reasoning, memory. In the parietal lobe is (12), Wernicke?s are for the sensory part of speech and (3) the main sensory cortex. (13) is the temporal lobe. (10) is the auditory cortex in this lobe. (11) is the taste area. (5) is the occipital lobe containing the visual cortex (eyesight). (6) is the cerebellum, controlling co-ordination and balance. (7) is the brainstem controlling vital functions, e.g., breathing, heart rate. [image] The Brain starts development in the embryo and foetus; (see Figure 3): Figure 3 Embryo : 3weeks[image] Embryo : 4 weeks[image] Embryo : 5 weeks[image] 1. Forebrain 2. Cranial nerves 3. cerebellum 4. Telencephalon 5. Diencephalon Embryo : 7 weeks[image] Embryo : 11 weeks[image] Foetus : 4 months[image] Foetus : 6 months[image] Foetus : 8 months[image] Newborn baby[image] Nerve impulses send information to and from your brain along your spinal cord. This allows your brain to monitor and regulate unconscious body processes, e.g. digestion and breathing. It is also the site of your consciousness, allowing you to think, learn and create. Brain: Your brain is made of many parts which are divided into four areas; the diencephalons, the brain stem, the cerebrum and the cerebellum. Each section has a specific function. Cerebrum The cerebrum is the largest part of your brain. The front section of your cerebrum, the frontal lobe, is involved in speech, thought, emotion, and skilled movements. Behind this is the parietal lobe which perceives and interprets sensations like touch, temperature and pain. Behind this, at the centre back of your cerebrum, is a region called the occipital lobe which detects and interprets visual images. Either side of the cerebrum is the temporal lobes which are involved in hearing and storing memory. The cerebrum is split down the middle into two halves called hemispheres that communicate with each other. Cerebellum Your cerebellum is the second largest part of your brain. It is involved in coordinating your muscles to allow accurate movements and control of balance and posture. Diencephalon Your diencephalon sits beneath the middle of your cerebrum and on top of your brain stem. It includes two important structures called the thalamus and the hypothalamus. Your thalamus receives incoming sensory nerve impulses, and then sends them on to appropriate areas of your brain for processing. It is responsible for informing your brain what?s occurring outside of your body. Your hypothalamus plays a vital role in keeping conditions inside your body constant e.g. regulating your body temperature; thirst and hunger. It also controls the release of hormones from the pituitary gland. Brain stem Your brain stem is responsible for regulating many life support mechanisms e.g. heart rate, blood pressure, digestion and breathing. It also regulates when you sleep and wake. Brain protection Your brain is certainly your most important organ, but it is made of soft tissues that would be injured by the slightest pressure. It is therefore well protected by three tough membranes called meninges which surround your brain. The space between your brain and the meninges is filled with a clear fluid; cerebrospinal fluid, which cushions your brain; it also provides it with energy and protects it against infection. Your skull encases your brain in a bony shell, cerebrospinal fluid and meninges. Long-term or excessive drinking can and does cause damage to the brain - Neurological damage and memory loss. Some damage can repair itself, but some can become permanent. Heavy drinking causes physical brain damage and even alcohol-induced dementia. This occurs when the impulses are not responding properly due to lack of oxygen and excess alcohol. Shrinkage of the brain is caused by excessive alcohol; this affects the cortex of the frontal lobe, which is believed to be the seat of higher intellectual functions. Spinal Cord: Your spinal cord can be divided into four sections shown in green, blue, pink and turquoise (see figure 4). Nerves emerging from these sections serve different parts of your body. Figure 4 [image][image] [image] [image][image] The effect of Alcohol: Alcohol is a depressant drug (Sedative-Hypnotics). Depressants are habit forming drugs which can lead to severe addiction problems. Among the most abused depressant drugs is Alcohol. Alcohol is used to relax the nervous system. One of the most rapid affects of alcohol is on the central nervous system (cns), which controls a range of vital body functions; the sense organs, muscles controlling speech as well as the sweat glands in the skin. The nerves which leave the spinal cord and brain comprise the peripheral nervous system. Your peripheral nervous system consists of 12 pairs of cranial nerves (see figure 5), which emerge from your brain and mainly serve your head and neck. It also contains 31 pairs of spinal nerves (see figure 6), which branch off from your spinal cord and supply the rest of your body. In normal circumstances the cns receives sensory information from organs such as the eyes and ears, it analyses the information and then initiates an appropriate response e.g. contracting a muscle. But when alcohol (toxins) interfere the CNS?s ability to analyse sensory information resulting in the typical symptoms of being drunk such as disturbed balance, slurred speech, blurred vision, heavy sweating and the dulling of our sensation of pain, and even loss of consciousness and possibly death. Figure 5 1. Cranial nerve i ? olfactory (sensory) 2. Cranial nerve ii ? optic (sensory) 3. cranial nerve iii ? Oculomotor (sensory and motor) 4. Cranial nerve iv ? trochlear (motor) 5. Cranial nerve v ? trigeminal (sensory and motor) 6. Cranial nerve vi ? abducent (motor) 7. Cranial nerve vii ? facial (sensory and motor) 8. Cranial nerve viii ? vestibule cochlear (sensory) 9. Cranial nerve ix ? glosspharyngeal (sensory and motor) 10. Cranial nerve x ? Vagus (sensory and motor) 11. Cranial nerve xi accessory (motor) 12. Cranial nerve xii ? hypoglossal (motor) [image] Peripheral nervous system Your spinal cord has 31 pairs of nerves, (see figure 5) Figure 6 The 31 pairs of nerves from the spinal cord [image] a. 8 Cervical pairs (c1-C8) b. 12 Thoracic pairs c. 5 Lumbar pairs (L1-L5) d. 5 Sacral pairs (S1-S5) Cervicobrachial plexus [image] 1. Lesser occipital nerve 2. Greater auricular nerve 3. Transverse cervical nerve 4. Ansa cervicalis 5. Supraclavicular nerves 6. Hypoglossal nerve 7. Superior trunk 8. Medial trunk 9. Inferior trunk 10. Supraclavicular prt 11. Infraclavicular part 11a. Lateral cord 11b. Medial cord 11c. Posterior cord 12. Musculocutaneous nerve 13. Median nerve 14. Medial antebrachial cutaneous nerve 15. Medial brachial cutaneous nerve 16. Ulnar nerve 17. Axillary nerve 18. Radial nerve 19. Long thoracic nerve 20. Medial pectoral nerve 21. Phrenic nerve 22. Clavicle 23. Sternum How it works: When you drink alcohol it is absorbed into the bloodstream from the stomach and small intestine. Once in the blood it is rapidly dispersed throughout the body and begins to have an effect on every cell. Alcohol is a cell poison but the body is efficient at protecting itself from most of its dangerous effects. It does so by chemical reactions which take place in the liver. As the blood passes through the liver the alcohol is gradually broken down to less harmful substances. Alcohol affects the brain, heart, muscles and other tissues of the body. (See Figure 7). In particular it reaches the brain quickly and therefore acts as a depressant. Alcohol causes low blood pressure. Blood vessels are open (vasodilation ? an increase reduction in the diameter of small arteries (arterioles) which is caused by relaxation of the smooth muscle fibres in the wall of the arteriole), it is therefore easier for blood to flow through your body ? low peripheral resistence (causing flushing) ? low blood pressure Blood is transported around the circulatory system, it reaches the vena cava where it builds up, because your heart is beating slowly the pressure to pump the blood through is low, this then causes the vena cava to stretch (stretch receptor), impulses are then sent to your brain (acceleratory centre which is located in Medulla Oblongata), which in turn sends a message back to S. A. Node (in your heart) to speed up, which enables the blood in the vena cava to start flowing again. Alcohol affects various different parts of the human body; as illustrated in the diagram. Figure 7 [image] Alcohol and Your Kidneys: The kidneys (see figure 8) direct fluids straight to the bladder, making you urinate excessively and speeding up the loss of fluid from the body causing dehydration. Most of the symptoms of a hangover include: headaches, dizziness, thirst, paleness and tremors, these are all caused by dehydration. [image] Text Box: Alcohol and Your Liver: The liver plays a vital role in the human body. It fights infection and filters poison. It also maintains our normal body chemistry It metabolises about 90% of the alcohol in our body while only about 10% is excreted through either our urine or our breath. The rate of alcohol metabolising varies between males and females. The alcohol metabolises at the rate of one ? two units per hour. A unit of alcohol is equivalent to half a pint of beer or lager, 25mls (a standard shot) of spirits in a pub or 125mls of red or white wine. When a person drinks, the body responds to large quantities of increased glucose in the system by producing more insulin which removes the glucose; this is known as Hypoglycaemia. Once the process has started, the insulin carries on working removing glucose from the blood. Hypoglycaemia is responsible for the shaky feeling, heavy sweating, dizziness and blurred vision. Low glucose levels also result in feeling tired. To overcome this feeling of lethargy and tiredness the body craves a carbohydrate boost; which is why many people feel hungry when they have been drinking. Long term alcohol exposure has a very serious effect on the liver. It starts producing more alcohol dehydrogenase, an alcohol + NAD+ = an aldehyde or ketone (see figure 9) + nadh + H+, the enzyme which is used to break ethanol down. This means, you need to consume more alcohol to be able to get the same effect. This worsens the addiction. The liver then becomes over active, cells die and the tissue hardens. The result is cirrhosis of the liver. Figure 9 [image] Cirrhosis (see figure 10) is a disease that destroys healthy tissue, leaving scar tissue, and blocking the flow of blood through an organ. It usually refers to the liver although it may be used to describe the same process in other organs in the body. When Cirrhosis occurs, the liver ceases to function properly, failing to control infection and blood clotting; (one of three key processes in haemostasis, the prevention of blood loss, and preventing bile from transferring to the small intestine.) Cirrhotic liver Figure 10 Conclusion: Ethyl alcohol (ethanol, CH3CH2OH,) is a low molecular weight aliphatic (open chain) compound, which is completely soluble with water. This is because of its hydroxyl (-OH) group, which forms intermolecular hydrogen bonds to water. The hydroxyl group is hydrophilic (water-attracting), whereas the ethyl (C2H5-) group is hydrophobic (water-repelling). Because alcohol is soluble with water, it is easily distributed throughout the body in the aqueous blood stream after consumption; and because it is water soluble, it can easily cross important biological membranes such as the blood brain barrier, which in turn affects a large number of organs and biological processes in the body. The passage of ethyl alcohol across biological membranes occurs by a process of simple passive diffusion along concentration gradients. This would therefore conclude, that alcohol can be a very harmful substance, which can affect various organs and also damage the blood stream, which also enables the organs to deterioate more rapidy.

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