QUESTIONS AND ANSWERS 133 



State the function of the phrenic nerve. 



It is the motor nerve to the diaphragm. 



Describe the effect of electric stimulation on a motor nerve. 

 Muscular contraction follows. 



Name and describe the membranes of the brain. Give the function of 

 each. 



The outer membrane, the dura mater, is dense and fibrous and 

 serves a very valuable protective function. The arachnoid is a 

 serous membrane applied against the inner face of the dura. It 

 contains the subarachnoid fluid which equalizes pressure on the 

 brain and saves it from jar and concussion. The pia mater, the 

 most internal, is a thin but very vascular structure. It passes 

 into all the convolutions of the surface of the brain and supplies 

 it with blood. 



State the function of the cerebellum and describe the effect of its 

 removal. 

 The cerebellum presides over the coordination of body move- 

 ments and equilibrium. If removed, the power of coordination is 

 lost, muscular weakness ensues and disturbances in equilibrium 

 follow. 



Locate the medulla oblongata. Mention four centres located in it. 



The medulla is located at the upper end of the spinal cord, be- 

 tween it and the cerebrum, and rests on the basilar process. 



Centres located in the medulla are: the respiratory, vaso- 

 motor, deglutition and vomiting. 



Discuss the functions of the medulla oblongata. 



Serves as a medium of transmission of motor and sensory im- 

 pulses and contains centres for mastication and suckling, secretion 

 of saliva, deglutition, vomiting, dilatation of the pupil, coughing, 

 sneezing, closure of eyelids, contraction and relaxation of the blood- 

 vessel walls, cardiac inhibition and respiration. There is also a 

 centre which controls the glycogenic function of the liver. 



State the function of the cerebrum. 



The cerebrum is the seat of sensation, reasoning and will. It 

 contains motor and sensory areas and the centres for sight, hearing 

 and taste are located in it. 

 Define (a) coordination, (b) augmentation, (c) inhibition, (d) autom- 

 atism. 



(a) Harmony and rhythm in muscular movements. 



(b) The increasing of the action of nerve centres by afferent 

 impulses. 



