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In c e r v i c a l a n d u p p e r t h o r a c i c r e g i o n s, i n t e r me d i a t e me s o d e r m i s s e g me n t e d; i n l o w e r t h o r a c i c, l u mb a r, a n d s a c r a l r e g i o n s i t f o r ms a s o l i d, u n s e g me n t e d ma s s o f t i s s u e, the n e p h r o g e n i c c o r d. N o t e the l o n g i t u d i n a l c o l l e c t i n g d u c t, f o r me d i n i t i a l l y b y the p r o n e p h r o s b u t l a t e r b y the me s o n e p hBo s. T h e me s o n e p h r o s a n d g o n a d a r e a t t a c h e d t o the p o s t e r i o r a b d o mi n a l w a l l b y a b r o a d u r o g e n i t a l meBe n the lra t i o n o f the g o n a d a n d s. T h e me s o n e p h r i c d u c t (w o l f f i a n d u c t) r u n s a l o n g the l a t e r a l s i d e o f the me s o n e p h r o s. R e l a t i o n o f the h i n d g u t a n d c l o a c a a t the e n d o f the f i f t h w e e k. D e v e l o p me n t o f the r e n a l p e l v i s, c a l y c e s, a n d c o l l e c t i n g t u b u l e s o f 5 the me t a n e p h r oA. N o t e the p y r a mi d f o r m o f the c o l l e c t i n g t u b u l e s e n t e r i n g the mi n o r c a l y x. E a c h c a l y x f o r ms t w o n e w b u d s w h i l e p e n e t r a t i n g the me t a n e p h r i c t i s s u. T h e s e b u d s c o n t i n u e t o s u b d i v i d e u n t i l 1 2 o r mo r e g e n e r a t i o n s o f t u b u l e s h a v e f o r me d (F i g. D u r i n g f u r the r g he s d e v e l o p me n t, c o l l e c t i n g t u b u l e s o f the f i f t h a n d s u c c e s s i v e g e n e r a t i o n s e l o n g a t e c o n s i d e r a b l y a n d c o n v e r g e o n the mi n o r c a l y x, f o re n a lg p y ea m i(F i g. T h e u r e t e r i c b u d g i v e s r i s e t o the u r e t e r, the r e n a l p e l v i s, the m a j o r) and m inor caly ce s, and approx im ate ly 1 to 3 m illion colle cting tubule s. E x c r e t o r y S y s t e ma c h n e w l y f o r me d c o l l e c t i n g t u b u l e i s c o v e r e d a t i t s d i s t a l E. C o n t i n u o u s l e n g the n i n g o f the e xc r e t o r y t u b u l e r e s u l t s i n f o r ma t i o n o f t h ep r o x i m a l c o n v o l u t e d t u b u l e, l o o p o f, Hn ddl ie t a l c o n v o l u t e d aen s t u b u l e(F i g. F H e n c e, the k i d n e y d e v e l o p s f r o m t w o s a)u r c e s: (o me t a n e p h r i c me s o d e r m, w h i c h p r o v i d e s e xc r e t o r y ub) i t s;e au rd t(e r i c b u d, n h ne w h i c h g i v e s r i s e t o the c o l l e c t i n g s y s t e m. At b i r t h, the kidneys have a lobulated appearance, but the lobulation disappears during infancy as a result of further growth of the nephrons, although there is no increase in their n u mb e r. M o l e c u l a r R e g u l a t i o n o f K i d n e y D e ve l o p m e n t As w i t h mo s t o r g a n s, d i f f e r e n t i a t i o n o f the k i d n e y i n v o l v e s e p i the l i a l me s e n c h y ma l i n t e r a c t i o n s. In t h i s e xa mp l e, e p i the l i u m o f the u r e t e r i c b u d f r o m the me s o n e p h r o s i n t e r a c t s w i t h me s e n c h y me o f the me t a n e p h r i c b l a sFeg. In t u r n the b u d s i n d u c e the me s e n c h y meb v oa l a s t g r o w t h f a c t o r 2 (Fa nF 2)o n e fi r i b G db m o r p h o g e n e t i c p r o t e i(B M P 7 (F i g. C o n v e r s i o n o f the me s e n c h y me t o a n e p i the l i u m f o r n e p h r o n f o r ma t i o n i s a l s o me d i a t e d b y the u r e t e r i c b u d s, i n p a r t t h r o u g h mo d i f i c a t i o n o f the e xt r a c e l l u l a r ma t r ifx. G D N F a n d H G F, a l s o p r o d u c e d b y the me s e n c h y me, i n t e r a c t t h r o u g h the i r r e c e p t o r s, R E T a n d M E T, r e s p e c t i v e l y, i n the u r e t e r i c b u d e p i the l i u m, t o s t i mu l a t e g r o w t h o f the b u d a n d ma i n t a i n the i n t e r a c t i o n s. R e n a l d y s p l a s i a s da g e n e s i s r e a s p e c t r u m o f s e v e r e ma l f o r ma t i o n s t h a t n a r e p r e s e n t the p r i ma r y d i s e a s e s r e q u i r i n g d i a l y s i s a n d t r a n s p l a n t a t i o n i n the f i r s t y e a r s o f l i f M. Nephrons fail to develop and the ureteric bud fails to branch, so that the c o l l e c t i n g d u c t s n e v e r f o r m. In s o me c a s e s, the s e d e f e c t s c a u s e i n v o l u t i o n o f the k i d n e y s a n e n a l a g e n e s i R. T h u s, mu t a t i o n s i n g e n e s t h a t r e g u l a t e G D N F e xp r e s s i o n o f s i g n a l i n g ma y r e s u l t i n r e n a l a g e n e s i s. B i l a t e r a l r e n a l a g e n e s i s, w h i c h o c c u r s i n 1 / 1 0, 0 0 0 b i r t h s, r e s u l t s i n r e n a l f a i l u r. T h e b a b y p r e s eo ttts r is e q u e n,c e P n e w th c h a r a c t e r i ze d b y a n u r i a, o l i g o h y d r a mn i o s (d e c r e a s e d v o l u me o f a mn i o t i c f l u i d), a n d h y p o p l a s t i c l u n g s s e c o n d a r y t o the o l i g o h y d r a mn i o s. In 8 5 % o f c a s e s, o the r s e v e r e d e f e c t s, i n c l u d i n g a b s e n c e o r a b n o r ma l i t i e s o f the v a g i n a a n d u t e r u s, v a s d e f e r e n s, a n d s e mi - n a l v e s i c l e s, a c c o mp a n y t h i s c o n d i t i o n.
Additional tests were added by many states in their screening programs until the implementation of tandem mass screening technology during the past decade replaced most of these individual tests with a single test performed on a dried blood spot on filter paper symptoms 14 days after iui order reminyl pills in toronto. Although the preceding goals are relatively easy for the term infant to meet treatment tennis elbow cheapest generic reminyl uk, a variety of common issues may delay discharge symptoms 0f parkinson disease purchase cheapest reminyl and reminyl. These include hyperbilirubinemia symptoms liver disease purchase reminyl american express, hypoglycemia, suspected septicemia, infant apnea, anemia, and signs of substance withdrawal. Because many of these topics are discussed in depth elsewhere in this book, they will not be presented in detail here. Although parents whose infants cannot be discharged at 48 hours are often greatly distressed, a clear and sympathetic explanation of the reasons this is necessary usually alleviates their concerns. Providing a comfortable place for the mother to visit during the delayed discharge should also be a high priority of care. Most commonly, the legs are flexed and crossed most of the time, with the tibia overlying one another. The feet may also tuck into the creases created by the leg flexion, and this position, depending on the site of placental implantation, may place some pressure on the tibia as the fetus matures. As a result, the tibia often turns in slightly, which is referred to as tibial torsion. This toeing-in from the tibial torsion usually disappears soon after the child starts to walk, and very few children are left pigeon-toed. As the feet can be brought to a neutral midline position, no intervention is usually necessary. After an initial period of weight loss, primarily caused by the loss of the excess extracellular fluid that is present at birth, the infant will begin to gain weight toward the middle to end of the first week of life and should attain birth weight no later than 2 weeks after delivery. Weight gain usually approximates intrauterine weight gain and averages about 1 ounce (30 grams) per day. Although breast milk is the best nutritive substance for infants, studies have demonstrated a high incidence of deficient vitamin D levels in breastfed infants. Breast milk can be low in vitamin D as a result of a lack of maternal sun exposure (particularly in the winter and in northern latitudes), increased use of sunscreen, and dress habits that prevent skin exposure. American Academy of Pediatrics Committee on Breastfeeding; American Academy of Pediatrics Committee on Nutrition. Prevention of rickets and vitamin D deficiency in infants, children and adolescents. Pacifier use has previously been discouraged in breastfed infants because studies have demonstrated an association with less successful breastfeeding. Thus it is now recommended that all formula-fed infants be given a pacifier at nap or at bedtime. For breastfeeding infants the use of a pacifier is also recommended at bedtime, but its use should not begin until breastfeeding has been well-established, which is typically 3 to 4 weeks after birth. Fetal growth assessments can be made clinically by assessing the fundal height; clinical assessment of fetal weight can be made by performing Leopold maneuvers. Fundal height is measured from the upper edge of the symphysis pubis to the top of the uterine fundus. Between 20 and 34 weeks of gestation, fundal height measurements (in centimeters) approximate the gestational age (in weeks). A discrepancy between measured and expected fundal height measurements of 3 centimeters or more is suggestive of fetal growth restriction. Leopold maneuvers involve the palpation of the fetus through the maternal abdomen. Advantages of Leopold maneuvers include the fact that the procedure is relatively easy to perform and does not incur the expense of ultrasound; disadvantages include a low sensitivity for macrosomia. In general, clinical estimates of fetal weight are more likely to underestimate the weight of macrosomic infants than to overestimate the weight. When fetal growth is estimated, several individual biometric parameters are commonly entered into a standard formula to calculate a composite weight. Because two-dimensional estimates of fetal weight do not account for variation in fetal body composition and because of the margin of error inherent in sonographic measurement of fetal biometries, sonographic assessments of fetal weight are associated with a significant (~10% to 20%) margin of error. No threshold weight has been universally accepted, but common definitions include a birth weight above 4000 or 4500 grams. In contrast to macrosomia, which is determined solely by birth weight, the term large for gestational age is used to describe any fetus with an estimated weight above the 90th percentile for a given gestational age.
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T h e u r e t h r a i s o p e n o n the B v e n t r a l s u r f a c e o f the p e n iE p i s p a d i a s c o mb i n e d w i the xs t r o p h y o f the C kerafill keratin treatment cheap 8 mg reminyl with visa. W h e n t h i s mi g r a t i o n d o e s n o t o c c u r symptoms 14 dpo reminyl 8mg on-line, r u p t u r e o f the c l o a c a l me mb r a n e e xt e n d s c r a n i a l l y treatment juvenile arthritis order reminyl 8 mg mastercard, c r e a t i n g e xs t r o p h y o f the b l a d d e r symptoms 5 days after conception purchase reminyl overnight delivery. M i c r o p e n i s c c u r s w h e n the r e i s i n s u f f i c i e n t a n d r o g e n s t i mu l a t i o n f o r g r o w t h o f o the e xt e r n a l g e n i t a l i a. M i c r o p e n i s i s u s u a l l y c a u s e d b y p r i ma r y h y p o g o n a d i s m o r h y p o t h a l a mi c o r p i t u i t a r y d y s f u n c t i o n. T h e g e n i t a l t u b e r c l e e l o n g a t e s o n l y s l i g h t l y a n d co ir tms i ts s e eF i g s. Al t h o u g h the v t st (F B) g e n i t a l t u b e r c l e d o e s n o t e l o n g a t e e xt e n s i v e l y i n the f e ma l e, i t i s l a r g e r t h a n i n the ma l e d u r i n g the e a r l y s t a g e s o f d e v e l o p me n t. In f a c t, u s i n g t u b e r c l e l e n g t h a s a c r i t e r i o n (a s mo n i t o r e d b y u l t r a s o u n d) h a s r e s u l t e d i n mi s t a k e s i n i d e n t i f i c a t i o n o f the s e xe s d u r i n g the t h i r d a n d f o u r t h mo n t h s o f g e s t a t i o n. P a t i e n t s a r e c h a r a c t e r i ze d b y i n f e r t i l i t y, g y n e c o ma s t i a, v a r y i n g d e g r e e s o f i mp a i r e d s e xu a l ma t u r a t i o n, a n d i n s o me c a s e s, u n d e r a n d r o g e n i za t i o n. In g o n a d a l d y s g e n e s i o c y t e s a r e a b s e n t a n d the o v a r i e s a p p e a r a s s t r e a k os g o n a d s. T hey have a 45,X karyotype and a short stature, high arched palate, webbed neck, shield-like chest, cardiac and r e n a l a n o ma l i e s, a n d i n v e r t e d n i p p l e s g(. In s o me c a s e s, the s e a b n o r ma l i t i e s r e s u l t i n i n d i v i d u a l s w i t h c h a r a c t e r i s t i c s o f b o t h s e xe s, k n o w n m a p h r o d i t. E xt e r n a l g e n i t a l i a a r e a mb i g u o u s o r p r e d o mi n a n t l y f e ma l e, a n d mo s t o f the s e i n d i v i d u a l s a r e r a i s e d a s f e ma l e s. In p s e u d o h e r m a p h r o d i,t eh e g e n o t y p i c s e x i s ma s k e d b y a p h e n o t y p i c ts a p p e a r a n c e t h a t c l o s e l y r e s e mb l e s the o the r s e x. W h e n the p s e u d o h e r ma p h r o d i t e h a s a t e s t i s, the p a t i e n t i s c a l l e d a ma l e p s e u d o h e r ma p h r o d i t e; w h e n a n o v a r y i s p r e s e n t, the p a t i e n t i s c a l l e d a f e ma l e p s e u d o h e r ma p h r o d i t. Other typical features are webbed neck, broad chest with widely spaced nipples, and short stature. F e m a l e p s e u d o h e r m a p h r o d i ti i s mo s t c o mmo n l y c a u s ec ob y e n i t a l s m d ng a d r e n a l h y p e r p l a s i a (a d r e n o g e n i t a l s y n d r io mh e mi c a l a b n o r ma l i t i e s i n B oc e). In mo s t c a s e s, 2 1 h y d r o xy l a t i o n i s i n h i b i t e d, s u c h t h a t 1 7 - h y d r o xy p r o g e s t e r o n e (1 7 - O H P) i s n o t c o n v e r t e d t o 11 - d e o xy c o r t i s o l. T h i s ma s c u l i n i za t i o n ma y v a r y f r o m e n l a r g e me n t o f the c l i t o r i s t o a l mo s t ma l e g e n i it g. In t e r n a l a n d e xt e r n a l s e x c h a r a c t e r i s t i c s v a r y c o n s i d e r a b l y, d e p e n d i n g o n the d e g r e e o f d e v e l o p me n t o f e xt e r n a l g e n i t a l i a a n d the p r e s e n c e o f p a r a me s o n e p h r i c d e r i v a t i v e s. C o n s e q u e n t l y, a n d r o g e n s p r o d u c e d b y the t e s t e s a r e i n e f f e c t i v e i n i n d u c i n g d i f f e r e n t i a t i o n o f ma l e g e n i t a l i a. The testes are frequently found in the inguinal or labial regions, but s p e r ma t o g e n e s i s d o e s n o t o c c u r. F u r the r mo r e, the r e i s a n i n c r e a s e d r i s k o f t u mo r f o r ma t i o n i n the s e s t r u c t u r e s, a n d 3 3 % o f the s e i n d i v i d u a l s d e v e l o p ma l i g n a n c i e s p r i o r t o a g e 5 0. T h i s s y n d r o me i s a n X- l i n k e d r e c e s s i v e d i s o r d e r that occurs in 1/20,000 live births. D e s c e n t o f the The s t e s To w a r d the e n d o f the s e c o n d mo n t h,o tg e n i t a l m e s e n t e rtya c h e s the ur he a t t e s t i s a n d me s o n e p h r o s t o the p o s t e r i o r a b d o mi ng. L a t e r, a s the t e s t i s b e g i n s t o d e s c e n d t o w a r d the i n g u i n a l r i n g, a n e xt r a - a b d o mi n a l p o r t i o n o f the g u b e r n a c u l u m f o r ms a n d g r o w s f r o m the i n g u i n a l region toward the scrotal swellings. When the testis passes through the inguinal c a n a l, t h i s e xt r a - a b d o mi n a l p o r t i o n c o n t a c t s the s c r o t a l f l o o r (the g u b e r n a c u l u m f o r ms i n f e ma l e s a l s o, b u t i n n o r ma l c a s e s i t r e ma i n s r u d i me n t a r y). F a c t o r s c o n t r o l l i n g d e s c e n t o f the t e s t i s a r e n o t e n t i r e l y c l e a r. It a p p e a r s, h o w e v e r t h a t o u t g r o w t h o f the e xt r a - a b d o mi n a l p o r t i o n o f the g u b e r n a c u l u m p r o d u c e s i n t r a a b d o mi n a l mi g r a t i o n, t h a t a n i n c r e a s e i n i n t r a - a b d o mi n a l p r e s s u r e d u e t o o r g a n growth produces passage through the inguinal canal, and that regression of the e xt r a - a b d o mi n a l p o r t i o n o f the g u b e r n a c u l u m c o mp l e t e s mo v e me n t o f the t e s t i s i n t o the s c r o t u m. P e r i t o n e u m l i n i n g the b o d y c a v i t y e v a g i n a t e s i n t o the s c r o t a l s w e l l i n g, w h e r e i t f o r ms the v a g i n a l p r o c e s s (t u n i cC. T h i s e v a g i n a t i o n, Ph e c e s s u s v a g i n a l fi o l l o w s the c o u r s e o f the t ro, s g u b e r n a c u l u m t e s t i s i n t o the s c r o t a l s w ei lg i.
The active principle of fresh cotif ton root forms a most wonderful uterine tonic keratin smoothing treatment discount reminyl line, ard treatment of uti purchase reminyl cheap, will correctly prepared medications 44 175 discount 8 mg reminyl visa, be found invaluable in sterility treatment of hemorrhoids reminyl 8 mg cheap, vaginitis, whites, menstrual irregularities, green sickness, etc. The flowers are white, and resemble those of the sycamore, and the fruit a hard and drj capsule. The from three to five lobes, hairy, dark-green, cordate at base, from four to nine inches wide when full grown. Golden seal is found growong in shady woods, in rich soils, and damp meadows in different parts of the United States and Canada, but is more abundant west of the Alleghanies. A is strong decoction of two parts of Golden Seal and one part of Geranium or injection. Ulceration of the internal coat of the bladder may be cured by the decoction of Golden Seal alone. It must be injected into the bladder, and held there as long as the patient can To be repeated three or four times a day, imconveniently retain it. The flower is a small starry white one, and the fruit an oblong capsule, containing many small black seeds. It may be beneficially used in all cases where a bitter tonic is required, and is decidedly efficacious as a wash or gargle, when a decoction, in various In dyspepsia, and in chronic inflammation ulcerations of the mouth. It grows in damp woods, in nearly all parts of the United States, flowering from September to November, when the leaves are the barks and leaves falling, and maturing its seeds the next summer. The shoots are used as divining rods to discover water and metals under ground by certain adepts in; - the occult arts. It is employed with great advantage in incipient phthisis or consumption, in which it is supposed to unite anodyne influences with its others. The decoction may be advantageously used as a wash or injection for sore mouth, painful tumors, external inflammations, bowol complaints, prolapsus ani and uteri, leucorrhoea, gleet, and ophthalmia. The following forms a useful preparation Take equal parts of witchand lobelia leaves, the two first made into a strong decoction, after which add the lobelia to the hot liquid, and when cold, strain. Doi^e of the witch-hazel decoction alone, from a wineglassful to a tea- cupful, three or four times a day. As a diaphoretic, it is one of the most certain of the whole materia medica, often exciting great coolness and coldness of the surface. In suitable doses it can be relied upon to bring the pulse down from a hundred and Hellebore. In fevers, in some diseases of the heart, acute rheumatism, and in many other conditions which involve an excited state of the circulation, it is of exceeding great value. As an arterial sedative it stands unparalleled and unequalled, while in small doses it creates and promotes appetite beyond any agent known to medical men. It has recently come into use, and may be justly regarded as one of the most valuable contributions to the list of medicines in a hundred where there years. If taken in so large a dose as to produce vomiting or too much depression, a full dose of morphine or opium, in a little brandy or ginger, is a complete antidote. It is administered in a little sweetened water, and its employment in moderate doses, or short of nausea, may be continued indefinitely without the least inconvenience. The Helleborus Niger, Black HelTmtil enty, ensue, then reduce to one-half in inhabiting the subalpine and southern parts of Europe, was formerly much used in palsy, insanity, apoplexy, Helleborus Niger. The stem sometimes reaches the height of twci but often stops at an altitude of six inches. The flowers are funnel-shaped, of a dull yellow color, with purple veins and orifice. The leaves are collected in the second year, when the plant is in flower the seeds are gathered when perfectly ripe. It grows more plentifully than elsewhere in America, in the waste grounds of old settlements, in graveyards, and around the foundations of ruined houses. Bruise the recent Dry them, leaves, and they emit a strong narcotic odor, like tobacco. The active principle of Henbane is called Hyosdamia^ but general name Properties and the recognized preparations are of Ilyoscyamus. The leaves make fine ex- ternal preparations for glandular swellings or ulcers, etc.
Neurotransmitters typically bind to cell membrane receptors on postsynaptic neurons or target organs medicine youtube generic reminyl 8 mg with visa. Synapses and the neurotransmitters that depolarize the postsynaptic neuron are excitatory synapses and excitatory neurotransmitters symptoms 12 dpo generic 4 mg reminyl with visa, while synapses and neurotransmitters that hyperpolarize the postsynaptic neuron are inhibitory medications education plans purchase reminyl 8 mg on line. Typically schedule 8 medications list generic 4mg reminyl with amex, excitatory neurotransmitters cause Ca2+ diffusion Voltage-gated Ca2+ channel Neuron Synaptic vesicle containing neurotransmitter Figure 10-3. Action potential arrives and promotes the opening of voltage-gated calcium channels. Entry of calcium promotes fusion of synaptic vesicles that release neurotransmitter. Neurotransmitter diffuses to postsynaptic cell membrane and binds to its cell membrane receptor. Hyperpolarization of the cell membrane can be brought about by either an increased rate of potassium exit from a cell or an increased rate of chlorine entry into the cell down their respective concentration gradients. The amount of excitatory neurotransmitter released by a single action potential in a single presynaptic neuron is constant. However, it is also typically insufficient to depolarize the postsynaptic neuron to a threshold voltage at which an action potential can be elicited. Temporal summation occurs when a single presynaptic neuron releases neurotransmitter repeatedly before the effect of each single release is lost. When effective summation occurs, the additive effects of the multiple releases are enough to produce an action potential in the postsynaptic neuron. Spatial summation occurs when simultaneous or nearly simultaneous neurotransmitter release occurs at more than one synapse on the postsynaptic neuron. Spatial summation is possible because neuron cell bodies typically have multiple junctions with many presynaptic neurons. After a neurotransmitter has been released and had its desired effect on the postsynaptic neuron, it must be removed to prevent continuous stimulation of the postsynaptic neuron. The specific mechanisms by which neurotransmitters are removed from neural synapses vary among neurotransmitters. However, in general these can be any one or a combination of the following: (1) enzymes in the area of the synapse degrade the neurotransmitter; (2) cell membrane transport systems absorb the neurotransmitter; or (3) the neurotransmitter diffuses away from the area of the synapse. Typically, as described earlier, a single neuron and its dendrites contain multiple synaptic junctions and receive synaptic input from multiple presynaptic neurons, so a single neuron may receive impulses from several sources. Divergence is the opposite: each axon branches so that synaptic connections are made with many neurons. These organizational patterns permit information to be widely distributed throughout a neural network (divergence) or permit multiple sources of information to be Divergence Convergence Figure 10-4. These are very simple illustrations of how the organization of neuronal networks can contribute to the processing and integration of information. For example, a single neuron can be simultaneously stimulated by excitatory and inhibitory neurotransmitters from different presynaptic neurons (a converging network). The property of spatial summation permits the neuron receiving these converging inputs to integrate the different stimuli and respond appropriately. Neurotransmitters Most neurotransmitters can be classified as amino acids, monamines (modified amino acids), or polypeptides. While more than 20 compounds have been proved to function as neurotransmitters (and the list will surely grow), some are especially prevalent throughout the nervous system and should receive individual consideration. Neurons releasing acetylcholine are classified as cholinergic, and this term is also applied to synapses for which acetylcholine is the neurotransmitter. Two general classes of acetylcholine (also termed cholinergic) receptors, nicotinic and muscarinic, are found at cholinergic synapses. The enzyme acetylcholinesterase is responsible for rapidly degrading acetylcholine and thus terminating its action at cholinergic synapses. Presynaptic neurons and synapses using norepinephrine are termed adrenergic, and this term is also applied to cell membrane receptors that bind norepinephrine. The term adrenergic has been applied to these receptors because epinephrine, or adrenaline, also binds to these receptors. Epinephrine and norepinephrine are both classified as catecholamines because of their chemical structure and because they are derived from the amino acid tyrosine. Dopamine is another catecholamine that functions as a neurotransmitter within the central and peripheral nervous systems, and specific dopamine receptors also exist. Neural Control of Skeletal Muscle As described in Chapter 8, each contraction of skeletal muscle requires stimulation of the muscle by a somatic motor neuron.
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