a) What is homeostasis? b) Name any three factors that must be maintained constant in mammalian bodies.

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a)  What  is  homeostasis? (Mechanisms  of)  control  and  maintenance  of  a  constant  internal  environment  regardless  of the  external  conditions;  2  mks.

 b) Name  any  three  factors  that  must  be  maintained  constant  in  mammalian  bodies.
 Temperature;  Water;  Salt  or  ion  content;  Carbon  (IV)  oxide;  Glucose;  amino  acids;  Max.  3 mks

 c) Explain how  endotherms  respond  to  heat  and  cold  conditions  in  their  environment.
 Heat/hot  conditions:  Increased  sweating;  to  lose  heat  through  latent  heat  of  vaporization; dilation  of  arterioles  under  the  skin;  to  bring  more  blood  to  the  skin  surface  to  lose  heat  to  the atmosphere;  decreased  body  metabolism;  to  reduce  heat  generation;  erector  pili  muscles relax;  making  hair  follicles  to  relax  hence  hair  lies  flat  on  skin,  no  air  is  trapped;  to  lose  heat; slow/reduced  muscular  activity  due  to  slow  metabolism;  to  reduce  heat  production;  panting to  expose  tongue  and  mouth;  to  release  heat;  moving  to  shades  to  avoid  direct  heat; aestivation;  to  escape  the  extreme  heat;  flapping  of  ears  to  create  currents  to  carry  away  heat;

Cold  conditions:  stamping  of  feet;  to  generate  heat;  basking  in  the  sun  to  gain  heat  directly; less  production  of  sweat;  to  reduce  water  loss  through  latent  heat  of  vaporization; vasoconstriction  of  arterioles;  hence  less  blood  flow  to  the  skin  surface  to  reduce  heat  loss; increased  metabolism  through  release  of  more  thyroxine  hormone;  to  generate  heat;  erector pili  muscles  contract;  pulling  hair  follicles  hence  hair  is  raised;  to  trap  a  layer  of  moist  air;  to prevent  heat  loss;  shivering/rapid  contraction  of  muscles;  to  yield  heat  to  warm  body;  Max. 15  mks 

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