Ejaculation regulating

Figure 19.18 The role of cyclic GMP and vasodilation in provision and preparation of spermatozoa for fertilisation. Vasodilation is regulated by the concentration of cyclic GMP by relaxation of smooth muscle. The resultant increase in blood flow to the corpora cavernosa results in erection of the penis for the ejaculation of spermatozoa into the vagina. The increase in blood flow to the vaginal smooth muscle provides more oxygen for diffusion into the lumen. Here it provides for oxidative phosphorylation in the mitochondria of the-mid section of the spermatozoa, which provides the ATP for the beating of the flagellum and hence for swimming to the oviduct for fertilisation.

The effect of catecholamines on the human uterus, which can be mediated by a- and /3-adrenoceptors, depends on its functional state. During pregnancy /32-adrenoceptor stimulation decrease the uteral tonus, an effect that can be used therapeutically. /32-Adrenoceptor agonists are in use as tocolytics. In the bladder base and the urethral sphincter a-adrenoceptors are present, mediating a contraction, whereas the /32-adrenoceptors of the bladder wall induce a relaxation of the particular smooth muscles present at these structures. Ejaculation is regulated by a-adrenoceptors. 

Effect on hypothalamus They produce hypothermia by acting on temperature regulating centre. They also produce central sympathoplegia resulting in miosis and failure in ejaculation. 

The other side effects include epileptic seizures, disturbances in body temperature regulation. ANS side effects include tachycardia, difficulty in micturition, inhibition of ejaculation, postural hypotension, blurring of vision (with thioridazine), constipation, nasal stuffiness etc. 

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