• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Whats involved in Homeostasis.

Extracts from this document...

Introduction

Homeostasis Homeostasis is involved in keeping the body's internal environment constant (like the thermostat of a central heating system). Homeostasis keeps the body's temperature at a certain level (36.5oC) and it keeps the pH of the body at a certain level so that enzymes don't denature. Blood glucose is kept constant, CO2 levels and O2 levels are monitored to ensure that enough oxygen and not too much carbon dioxide are in the blood. The overall concentration and volume of blood is also monitored homeostatically. Cannon first used the term Homeostasis in the late 1920s. Homeostasis is very important to animals because it allows them to rely on the external environment. A constant internal environment allows a considerable degree of independence and allows animals to live in areas from the arctic to the tropics. Many of the mechanisms involved rely on negative feedback. A movement from the set level (e.g. a rise or fall in body temperature) is detected by receptors. These receptors then send information to the control centre in the brain which reacts by returning to the original value. For example, the temperature control mechanism. Humans maintain body temperature within 1oC of 36.5. ...read more.

Middle

The ventromedial hypothalamus has been found to function as an 'off' switch to tell us when to stop eating. Animals with damage to this area have been found to overeat and become obese, sometimes tripling their body weight (Hetherington and Ranson, 1940). Olds (1958) stimulated the ventromedial hypothalamus with electrodes and found that this decreased eating. When the animal is full then the VMH sends impulses to say that it is time to stop eating, if the VMH is destroyed then the signal is not sent and the animal does not stop eating therefore becoming obese. The lateral hypothalamus is seen as the opposite, an 'on' switch. Animals who have damage to that area do not receive the signal to start eating and so they don't and consequently starve to death (Anand and Brobeck, 1951). Hess 91954) found that stimulating this area caused the animal to eat compulsively. The Glucostatic hypothesis says that the levels of glucose in the bloodstream determine how hungry we are. Neurons detect the level of glucose in the body, they are situated in the hypothalamus, the blood vessels and other organs. If the glucose level in the body drops and no more food is available then the liver releases more (this is stored in the liver in the form of glycogen). ...read more.

Conclusion

put two groups in two rooms, an obese group and a control group. They both had equal numbers of shelled and unshelled nuts. The control group ate equal amounts of shelled and unshelled nuts, the obese group ignored the unshelled and ate only the shelled nuts. Rats with LH damage have been able to be coaxed into eating and although they do not show any interest in food, they do not show interest in anything (Teitelbaum and Epstein, 1962). Therefore the idea of the LH being the 'on' switch is a little too simple and is a much more complex interaction of several systems together. The nervous system's involvement in the regulation of hunger is a little doubtful. The theories above have supporting and contradictory evidence. The 'on/off' model of the control of the hypothalamus is said to be too simple to control such a complicated and important mechanism in the body. There is evidently more to hunger than Canon and Washburn's empty and full stomach hypothesis. The glucostatic theory leaves some questions unanswered and there are definite problems. The theories alone don't seem to explain the complex mechanism of hunger control and regulation but an interaction of all of the theories may be a little closer to what really happens. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Exchange, Transport & Reproduction section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Exchange, Transport & Reproduction essays

  1. Marked by a teacher

    Human Reproductive System

    4 star(s)

    The average cycle takes about 28 days and occurs in 3 phases: the follicular phase, the ovulatory phase and the luteal phase. Fertility varies over the 28 days and day 11-14 is the most fertile. There are four major hormones that stimulate or regulate the activity of cells or organs

  2. The Endocrine System

    can be used to reduce growth hormone levels, and growth hormone receptor blockers can be used to reduce its effect on the liver. Treatment of symptoms and prevention measures against heart disease are also important. Follicle Stimulating Hormone (FSH) is produced and secreted by the anterior pituitary gland before being.

  1. Control of homeostasis.

    Effector - is a body structure which receives output from the control center and produces a response that changes the controlled condition. For example, when the temperature of the body drops your brain (control center) sends nerve impulses to your skeletal muscles (effectors)

  2. The Skeletal and Muscular System

    They are also present in the walls of arteries and veins. Smooth muscles have slow and sustained contractions. These contractions are weak and involuntary in nature. Cardiac Muscle Cardiac Muscle Cardiac muscle is found exclusively in the heart. It is striated in nature with both dark and light band.

  1. the role of the microbiology department

    If these contaminate the water supply, or infected people handle food or cooking utensils without washing their hands, then bacteria are transmitted to uninfected people. Almost all people with cholera who are treated make a quick recovery. A death from cholera is an avoidable death.

  2. Blood System Assignemnt

    Table 1: Structure and Functions of Blood Vessels (www.ivy-rose.co.uk) Structure Functions Arteries The walls (outer structure) of arteries contain smooth muscle fibre that contract and relax under the instructions of the sympathetic nervous system. Transport blood away from the heart; Transport oxygenated blood only (except in the case of the pulmonary artery).

  1. Regulation and Control Homeostasis.

    alcohol, nicotine) are made safe by chemical conversions within hepatocytes. Deamination of Amino Acids: * The liver breaks down any surplus amino acids because the body is unable to store them as such. * The amino group (-NH2) is removed from the amino acid and converted to ammonia (NH3).

  2. Urinary system

    Water, glucose, urea, proteins, uric acid, sodium, potassium, chloride ions and other substances are filtered from the blood into proximal convoluted tubules by a net filtration pressure (Solomon, E. et al 1990). The amount of filtrate that is produced by the kidneys is known as the glomerular filtration rate (GFR).

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work