By R. Temmy. San Francisco State University.
Sensory Organs © The McGraw−Hill Anatomy discount 35 mg actonel, Sixth Edition Coordination Companies purchase 35 mg actonel otc, 2001 490 Unit 5 Integration and Coordination • taste receptors on the tongue—chemoreceptors; and • skin receptors within the dermis—tactile receptors for touch, Knowledge Check mechanoreceptors for pressure, thermoreceptors for tempera- 4. Pain receptors are located throughout SOMATIC SENSES the body,but only those located within the skin are classified as The somatic senses arise in cutaneous receptors and propriocep- exteroceptors. The perception of somatic sensations is determined by the density of the receptors in the stimulated receptive field and the Visceroceptors intensity of the sensation. Special- ized visceroceptors located within the circulatory system are sen- Objective 6 Explain the purpose of pain and describe the sitive to changes in blood pressure; these are called baroreceptors. Objective 7 Explain what is meant by referred pain and phantom pain and give examples of each. Proprioceptors Proprioceptors are sensory nerve cells that relay information The somatic senses, or somesthetic senses, arise in cutaneous about body position, equilibrium, and movement. Cutaneous sensations include cated in the inner ear, in and around joints, and between ten- touch, tickle, pressure, cold, heat, and pain. Proprioceptors are especially abundant in postural muscles such as the trapezius, which maintains the vertical position of your head on the atlas vertebra. When your head starts to nod for- ward, such as when you are falling asleep during a boring lecture, Tactile and Pressure Receptors proprioceptors are activated in the stretched muscles, and impulses are immediately sent to the cerebellum where motor units involving Both tactile receptors and pressure receptors are sensitive to me- the trapezius muscles are activated. This homeostatic feedback chanical forces that distort or displace the tissue in which they mechanism causes your head to suddenly jerk back before your are located. Tactile receptors respond to fine, or light, touch and nodding head hits the desk. It also awakens you so that you are con- are located primarily in the dermis and hypodermis of the skin. Pressure receptors respond to pressure, vibration, and stretch Receptors may also be classified on the basis of sensory and are commonly found in the hypodermis of the skin and in adaptation (accommodation).
Androgens and estrogens are known gens under the influence of LH generic 35mg actonel with visa, whereas granulosa to stimulate the closure of the epiphyses at puberty buy cheap actonel 35mg line. Theca interna cells do Because eunuchs are castrated, they have no testicular contain cholesterol side-chain cleavage enzyme, source of androgen and estrogen, and the closure of which converts cholesterol to pregnenolone. In eunuchs, long bones con- theca cells do not express aromatase, they cannot con- tinue to grow, resulting in a tall stature. The theca interna has a have a positive effect in maintaining bone; however, rich blood supply. Choice B is incorrect, although eunuchs itary portal system leads to a lack of dopamine and may have elevated circulating LH (as a result of the GnRH reaching the pituitary. The absence of testes delays the closure of tion, the lack of GnRH will lead to reduced secretion the epiphyses, and androgen levels are low in eunuchs of LH and FSH, reduced ovarian function, and even- because of the lack of testes. PRL will have no effect on the ovary or inhibit ovarian follicle development. Disrup- Chapter 38 tion of the hypothalamic-pituitary axis will lead to re- duced follicular development, lack of ovulation, and 1. Although crease, but FSH will not increase because there is no LH may stimulate aromatase in granulosa cells, granu- GnRH reaching the pituitary from the disrupted axis. Estradiol synthe- Excessive ovarian androgen usually occurs in the pres- sis in the graafian follicle is unrelated to progesterone ence of excessive LH secretion or an androgen tumor synthesis in the corpus luteum and does not increase in the ovary. Inhibin is produced by granulosa cells between FSH and progesterone in regulating estradiol and inhibits the secretion of FSH. Granulosa cells do not have the en- can have local ovarian effects, it has profound in- APPENDIX A Answers to Review Questions 735 hibitory effects on FSH secretion. Inhibin has two reaction and pronuclei formation occur after the sperm forms, A and B; the subunits are the same, whereas has entered the ovum.