Question-   Assignment on Homeostasis


Question 3 : Using an example, describe possible changes in the body that might occur during homeostasis. (8 mark)

Homeostasis is maintained by control systems which detect and respond to changes in the internal environment. A control system has three basic component which is detector, control centre and effector.

  • For example control of body temperature:
  • When body fall below the preset level, its detected by by specialised temperature sensitive nerve ending (detector).
  • They transmit the informations as an input to group of cell in the hpothalamus of the brain which form the control centre
  • The output from the control centre activates mechanisms that raise body temperature (effectors). These include stimulation of skeletal muscle causing shivering, narrowing of blood vessels in the skin reducing the blood flow to and heat loss from the peripheries and behavioural change example put on more clothes or curl up.

Question 4 : Discuss the role of negative  feedback and positive feedback in maintaining homeostasis. (5m)

Negative feedback mechanism

Positive feedback mechanism

  • Negative feedback system act to stabilize the body in the face of changing external and internal condition. These system cause an opposite response to the initial change, and so are self limiting.
  • Example: when there is a low level of a hormone in the blood supplying, the hypothalamus it produces the appropriate releasing hormone which stimulates release of a trophic hormone by the anterior pituitary. This in turn stimulates the target gland to produce and release its hormone. As a result the blood level of that hormone rise and inhibits the secretion of releasing factor by the hypothalamus
  • Positive feedback systems are important in specific situations, when avry rapid or very strong effect is desired. The responce is the same as that caused by the initial change. An outside event must break the positive feedback cycle
  • Example : during labour, contractions of thr uterus are stimulated by hormone oxytocin. These force the baby’s head into the cervix of the uterus stimulating stretch receptors there. In response to this, more of hormone oxytocin are released, further strengthening the contractions and maintaining labour. After baby born the stimulus is no longer present and the release of oxytocin stops.


Question 5: How would a Respiratoy system disease affect the Cardiovasular system? (7m)

The blood circulatory system, also called the cardiovascular system, consists of the heart and the blood vessels that run throughout the body. It delivers nutrients and oxygen to all cells of the body.

The oxygen we breathe gets mixed into the blood in the lungs, and the heart pumps this blood to all parts of the body. Each heartbeat is a contraction of the heart as it pumps blood around the body.

The heart has four chambers: the left atrium, right atrium, right ventricle and left ventricle. They are all separated by one-way valves, meaning the blood can only flow in one direction. Blood is carried to the heart in the veins, and back out to the rest of the body in the arteries.

Disease in other organ systems, particularly in lungs can cause heart failure. Obstructive changes in the lungs result in increased pulmonary vascular resistance, which increase the Right Ventricle workload. In time, the right side of the heart has difficulty pumping blood forward to the lungs, becomes dilated, and hypertrophies. Then signs and symptoms of right side heart failure are seen. Cor Pulmonale is the term for Heart Failure resulting from obstructive lung disease such as cystic fibrosis or bronchopulmonary dypslasia


Question 6 : Define Sural, Pollex, Occipital, Manus, Popliteal, Sacral, pedal, metal, antecubital and Hallux. (6 m)


the calf of the leg


the innermost digit of the forelimb; thumb


situated near the occiput or the occipital bone


the distal segment of the forelimb of a vertebrate, including the carpus and the forefoot or hand


relating to the ham, or part of the leg back of the knee


relating to the sacrum


relating to a foot or the feet.


relating to the chin


In front of the elbow


the first or innermost digit of the foot of humans


Question 7: Differentiate between microfilament, intermediate filament and microtubule. (6m)


Intermediate filament


The smallest of the cytoskeletal elements.


The protein composition of intermediate filament varies among cell types

Insoluble and the most durable of cytoskeletal elements

Microtubules (hollow tube built from globular protein tubulin), the distribution in the cell change over the time.


Less the 6mm in diameter Composed of the protein ACTIN .

Range from 7-11mmin in diameter. Intermediate in size.

Diameter about 25nm, extens outward into the periphery of the cell from a region near the nucleus called the centrosome

3 major fuction:

  1. anchor the cytoskeletal to integral proteins of the cell membrane
  2. interact with other proteins and determine the consistency of the cytoplasm.
  3. Interact with the protein myosin to produce active movement and change the shape o entire cell

3 major fuctions:

  1. Strengthen te cell and help maintain its shape
  2. Stabilize the position of the organelles
  3. Stabilize the position of the cell with respect to surrounding cell through specialized attachment to the cell membrane

4 major fuctions:

  1. Form the primary components of the cytoskeletal (giving cell strength, rigidity and anchoring the position major organelles)
  2. Provide a mechanism, for changing the shape and movement of cells
  3. Serves as a kind of monorail system to move vesicles or other organelles within the cell
  4. Form structural components of organelle such as centrioles and cilia.


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