a) What is a reflex action? b) Outline the activities that occur in the body when one touches a hot object.

-
a)  What  is  a  reflex  action?
 Rapid  and  automatic;  response  to  a  particular  stimulus;  2  mks

 b)  Outline  the  activities  that  occur  in  the  body  when  one  touches  a  hot  object.
 When  the  hot  object  is  touched,  the  pain  receptors;  in  the  skin  of  the  finger  are  stimulated; nerve  impulses  are  initiated  and  transmitted  through  the  sensory  neurone;  to  the  grey  matter; of  the  spinal  cord  to  the  brain;  for  interpretation;  the  impulses  are  then  transmitted  through the  relay  neurone;  via  a  synapse;  the  impulses  from  the  relay  neurone  are  transmitted  via  the motor  neurone;  through  another  synapse;  to  the  effector;  which  are  the  biceps  muscles  of  the upper  arm;  making  the  muscles  to  contract;  straightening  the  arm;  and  the  arm  is  withdrawn from  the  hot  object;  Max.  18  mks 

Comments

Post a Comment

Popular posts from this blog

Explain how structures of the human ear are adapted to their functions. (20 marks)

-
Image
The pinna;- is funnel shaped to trap sound waves; cartilaginous to maintain the funnel shape; collects and directs sound waves into the external auditory meatus ear; The external auditory canal; - a tube connected to the pinna that directs sound waves from the pinna to the eardrum lining the auditory canal; has hair that trap foreign particles; The canal contains wax-secreting cells; and hair which traps dust particles; and pathogenic bacteria hence prevent them from getting into the ear; The eardrum; - has a thin tough membrane; that easily vibrates when hit by sound waves; transferring them into vibrations. The ear ossiscles; - they act like a layer and they easily move forward and backward to amplify sound vibrations that hit them; The suspensory ligaments; - suspends the ear ossicles and prevents excessive vibration that would otherwise damage the inner parts of the ear; The eustachian tube - it connects the middle ear with the pharynx; and it equalises air pressure between
Read more

DESCRIBE THE ADAPTATIONS OF THE ILEUM TO ITS FUNCTION (20 MARKS)

-
Has secretory glands/crypts of lieberkuhn which secretes enzymes (maltase/sucrase/lactase/peptidase/lipase to complete digestion of sugars/proteins/lipids. Goblet cells secrete mucus which allows for smooth movement of food and protect wall of ileum from action of digestive enzymes Very long to provide large surface area for absorption. Highly folded/coiled to slow movement of food to allow more time for digestion/absorption/ and to increase surface area for absorption. Has numerous villi which increase surface area for absorption/microvilli which further increase surface area for absorption. Ileum wall/villi have thin epithelium which is only one cell thick to reduce distance over which digested food has to diffuse. Villi are highly vascularised/have a rich network of blood capillaries for rapid transport from small intestines and maintain a steep concentration gradient for rapid absorption. Villi have lacteals for absorption of fatty acids and glycerol Cells of ileum wall h
Read more

(a) Define digestion. [2 m] (b) Describe the digestion of a piece of ugali in a human digestive system from the mouth until its assimilation. [18mks]

-
(a) Define digestion It is break down of complex insoluble; v food substance into simple soluble food substances; v 2max (b) Describe the digestion of ugali; Digestion of ugali begins in the mouth;v ugali is chewed by the teeth to increase large surface areav for action of salivary amylase / ptyalin; vThe food mixes with saliva produced by salivary glands;v Saliva contains mucus and enzyme ptyalin. Mucus moistens, softens and lubricates the food;v ptyalin speeds up the conversion of starch to maltose;v ugali is made into bolus in the mouth;v The bolus moves along the oesophagus and prestalsis / by contraction and relaxation of circular and longitudinal muscles into the stomach;v The digestion continues until ugali become acidic since the stomach does not contain carbohydrase / carbohydrate digesting enzymes no digestion of ugali takes place here.v Ugali now
Read more