• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month
  1. 1
  2. 2
  3. 3
  4. 4
  5. 5
  6. 6
  7. 7
  8. 8
  9. 9
  10. 10
  11. 11
  12. 12
  13. 13
  14. 14

Revision questions on Communication, Homeostasis and Energy

Extracts from this document...


F214-Communication, Homeostasis and Energy Module 1-Communication and Homeostasis 4.1.1 Communication a. Outline the need for communication systems within multicellular organisms * External environmental changes o Changes in the external environment can cause stress. o It may change slowly so there will be a gradual response. o It may be a quick change so a rapid response is needed. * Internal environmental changes o The environment of internal cells is that they are protected by epithelial cells and they are bathed in tissue fluid. o The activities of cells alter their environment e.g. releasing toxic products that need to be removed. * Coordination of activities of organs o Groups of specialised cells form tissues and organs. o Cells monitor the blood and can release a substance into the blood to remove certain substances. b. State that cells need to communicate with each other by a process known as cell signalling * Cells need to communicate to ensure that the different parts of the body work together effectively. * Cell signalling-The process where one cell releases a chemical that is detected by another cell which will react and respond to the signal. c. State that neuronal and hormone systems are examples of cell signalling * Neuronal systems o Interconnected network of neurones that signal to each other across synapse junctions. * Hormonal systems o The blood is used to transport signals. o Cells in an endocrine organ release a hormone which is the signal into the blood which is then carried around the body and recognised by specific target cells. d. Define the terms negative feedback, positive feedback and homeostasis * Negative feedback o Process that brings about a reversal of any change in conditions. o Maintains and optimum steady state due to the return of the internal environment to its original set of conditions. * Positive feedback o Process that increases the change detected by the receptors. ...read more.


The membrane depolarises as it becomes less negative the outside and reaches the threshold of -50mV. Voltage-gated sodium ion channels open and sodium ions flood in making the inside of the cell positively charged compared to the outside. The potential difference reaches +40mV. 3. Sodium ion channels close and potassium channels open. Potassium ions diffuse out bringing the potential difference back to negative which is called repolarisation. 4. The cell becomes hyperpolarised. 5. The original potential difference is restored and the cell is back to its resting potential. g. Outline the significance of impulse transmission * A signal from a light receptor will only inform that there is light but not the intensity. * When a stimulus is at a higher intensity it will produce more generator potentials therefore there will be more frequent actions potentials so more vesicles are released at synapses. * The brain can determine the intensity of the stimulus due to the frequency of signal arriving. * More signals=a more intense stimulus. h. Compare and contrast the structure and function of myelinated and non-myelinated neurones Myelinated neurones Non-myelinated neurones * Fast speed of conduction- 100-200ms-1. * Has nodes of Ranvier. * Has a myelin sheath with each neurone wrapped in several Schwann cells. * In the peripheral nervous system carrying impulses from sensory receptors to the Central Nervous System or from the Central Nervous System to the effector. * Action potential moves via saltation. * Carry signals over a longer distance. * Slow speed of conduction- 0.5-10ms-1. * Does not have nodes of Ranvier. * Does not have a myelin sheath but several neurones may be surrounded by one Schwann cell. * In the Central Nervous System and in the nerves controlling the organs with no conscious control. * Action potential moves in a wave. * Carry signals over a short distance. i. Describe the structure of a cholinergic synapse Cholinergic synapse=A synapse that uses acetylcholine as the neurotransmitter. ...read more.


* Certain factors may make the onset earlier: obesity, a diet high in sugars, being of Asian or Afro-Caribbean origin and family history. h. Discuss the use of insulin produced by genetically modified bacteria and the potential use of stem cells to treat diabetes mellitus * Advantages of using genetically modified bacteria o Exact copy of human insulin so faster acting and more efficient than using animals. o Less chance of developing intolerance. o Less chance of rejection. o Lower risk of infection. o Cheaper to manufacture. o Less likely to cause medical objection. * Using stem cells. o They are not differentiated so can be any cell. o Most common sources are bone marrow and the placenta. o Similar precursor cells have been found in the pancreas of adult mice. It is thought that if similar ones are found in the human pancreas then it could be used to produce new � cells to treat type 1 diabetes. i. Outline the hormonal and nervous mechanisms involved in the control of heart rate in humans * Movement of the limbs are detected by stretch receptors which send impulses to the cardiovascular centre informing it that more oxygen may be needed increasing the heart rate. * During exercise more carbon dioxide tends to be produced some of which will react with water in the blood plasma reducing the pH. This change is detected by chemoreceptors in the cartoid arteries, the aorta and the brain. These send impulses to the cardiovascular centre increasing the heart rate. * When we stop exercise it leads to a decrease in carbon dioxide levels, decreasing the activity in the accelerating pathway leading to the heart rate decreasing. * When adrenaline is released in response to stress, shock, anticipation and excitement, the heart rate increases to prepare the body for activity. * Blood pressure is monitored by stretch receptors in the walls of the cartoid sinus. If it gets too high it send signals to the cardiovascular centre leading to the reduction in heart rate. ...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)

    Out of the millions of sperm cells present in ejaculation only one succeeds in fertilisation with a fertile ovum or egg present in the fallopian tube and results in the formation of a new embryo. Fertilistion is the union of sperm and egg that occurs in the ampulla of the fallopian tube.

  2. Marked by a teacher

    The Effect Of Temperature On The Permeability Of The Cell Membrane

    3 star(s)

    This is used to place the beetroots on in order to cut them in the accurate length .I will be using a while tile to place my beetroot onto, Why? The reason why I am using a white tile instead of black or any other is because using a white is easier to see.] * Colour Emitter- [What?

  1. Rate of Respiration

    hence the syringe is unable to show the amount of C02 gas that has entered the syringe. Thus I will change my method and apparatus by using the invested burette water displacement method, which inaccurate to 0.1 cm3 (which is more accurate that the gas syringe).

  2. The Skeletal and Muscular System

    When the arm is moved towards the body, the biceps contracts while the triceps relaxes, bending at the elbow. At this point the biceps muscle becomes thicker and shorter while the triceps muscle becomes thinner and longer. When the arm is straightened, the triceps muscle contracts, becoming thicker and shorter while the biceps muscle relaxes, becoming thinner and longer.

  1. The Endocrine System

    in target organs that respond in specialized ways to the minute quantities of the hormonal messengers. The amounts of hormones are maintained by feedback mechanisms that depend on interactions between the endocrine glands, the blood levels of the various hormones, and activities of the target organ.

  2. Control of homeostasis.

    sends nerve impulses to your skeletal muscles (effectors) that cause you to shiver. In order for a control system to function there must be receptors to monitor changes (stimuli) in the internal environment. These receptors send information to a control center which monitors the change and integrates the information.

  1. Fundamental human anatomy and physiology.

    Reference: http://www.infovisual.info/03/038_en.html Class notes handout 26 / 2 / 2008 Web sight viewed on 27 / 2 /2008 Endocrine System * Endocrine system is a gland that is scattered through out the body. * The function of the endocrine is to control and coordinate organs therefore maintains the blood glucose,

  2. Evolution and Biodiversity - Edexcel GCE Biology Revision Notes

    * Pits are regions of the cell wall where the wall is very thin (only primary cell wall is present) They?re arranged in pairs and they allow transport of substance ? due to shortened diffusion distance and cell communication. * Chloroplasts are small flattened structures surrounded by a double membrane

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