communication and homeostasis *5

• what term is used to describe communication between adjacent cells ?

  cell signalling
• what two systems are used in animals to coordinate responses to change in the environment ?

  The endocrine system and nervous system
• what are the speed, duration and distribution of responses produced by hormones ?

  hormones usually produce a response that is long lasting, slow and widespread
• what are the speed, duration and distribution of responses produced by nerve impulses ?

  nerve impulses produce responses that are usually quick, short-lived, and localised
• name of homeostatic control in which the response to a stimulus restores a factor to its original set point ?

  negative feedback
• what is the name given to the homeostatic control in which the response to a stimulus causes a factor to deviate further from its original set point ?

  positive feedback
• what is a receptor ?

  a cell or protein that detects one specific type of stimulus
• what is an effector ?

  a part of the body, often a gland or a muscle, that produces a response to a stimulus
• what responses are seen in trees in temperate regions to avoid water stress in winter when soil may be frozen ?

  leaf falling and dormancy
• what is the term used to describe the sensitivity of plants to the balance of hours of daylight and dark over the course of a day ?

  Photoperiodism
• what term is used for the seperation of part of a plant such as a leaf, fruit or flower causing it to fall ?

  Abscission
• what is the function of the production of solutes in winter to lower the melting point of plant cell cytoplasm ?

  to prevent cells from freezing
• how do stomata help prevent overheating in plants ?

  they open to increase transpiration which cools the plant by evapouration.
• what is meant by the term ectotherm ?

  an animal which depends on the external enviornment to regulate its internal body temperature
• sun basking and shade seeking are both examples of which type of response shown by ectotherms to help them control internal temperature ?

  behavioural response
• what is meant by the term endotherm ?

  an animal that maintains a constant internal body temperature regardless of the external temperature by generating heat through metabolic processes
• in endotherms, temperature receptors are located in which two parts of the body?

  Skin and hypothalamus.
• in endotherms which part of the brain is involved in thermoregulation ?

  Hypothalamus
• what is seen in endotherms in response to a rise in core body temperature ?

  vasodilation,sweating and lowering hair by relaxing hair erector muscles
• what is seen in endotherms in response to a fall in core body temperature ?

  vasoconstriction, shivering, raising hair erector muscles by contracting
• define the term excretion?

  the removal of waste products of cell metabolism from the body
• what are the three main waste products which need to be excreted in mammals ?

  carbon dioxide, bile pigments and urea
• how do hepatocytes respond to insulin ?

  they take up glucose and convert it into glycogen for storage
• which process in the liver removes the amine group from amino acids when breaking down excess proteins ?

  deamination
• which process in the liver combines ammonia with carbon dioxide to produce urea ?

  ornithine
• the breakdown of alcohol and drug molecules are both examples of which function of the liver ?

  detoxification
• name three main areas which can be seen when a whole kidney is cut open ?

  Cortex, medulla, and renal pelvis.
• name the microscopic functional units of the kidney responsible for producing urine ?

  Nephrons
• what are the four main mechanisms that must occur in the nephron to convert filterate into urine ?

  ultrafiltration,selective reabsorption, secretion and excretion
• what are the five main structures found in a nephron ?

  Bowman's capsule, proximal convoluted tubule, loop of Henle, distal convoluted tubule, collecting duct
• what is the name of the knot of capillaries found within the Bowman's Capsule ?

  glomerulus
• in relation to kidney function, what is meant by the term "diuresis" ?

  An increase in the production of urine by the kidney resulting in a large volume of diluted urine
• where is ADH made in the body ?

  in the hypothalamus
• where is ADH stored in the body ?

  posterior pituitary gland
• what is the role of the hypothalamus in osmoregulation ?

  osmoreceptors in the hypothalamus are sensitive to changes in the water potential of the blood. Nerves from the hypothalamus control the release of ADH by the posterior pituitary gland
• ADH exerts its effect by binding to the receptors on the surface of which cells ?

  Cells in the walls of the collecting duct
• where in the body are the islets of langerhans found ?

  Pancreas
• what is the function of the islets of langerhans ?

  to secrete and produce hormones
• which hormone do alpha cells in the islets of langerhans produce ?

  Glucagon
• which hormone do beta cells in the islets of langerhans produce ?

  insulin