By S. Silvio. Aquinas College.
Oxytocin stimulates the contraction of myoepithe- each consisting of nine amino acid residues cheap 25mg clomiphene amex. Two forms of lial cells cheap clomiphene 25mg with visa, which surround the milk-laden alveoli in the lac- vasopressin, one containing arginine and the other con- tating mammary gland, aiding in milk ejection. Arginine va- Oxytocin secretion is also stimulated by neural input sopressin is made in humans. Although AVP and oxytocin from the female reproductive tract during childbirth. Cer- differ by only two amino acid residues, the structural dif- vical dilation before the beginning of labor stimulates ferences are sufficient to give these two molecules very dif- stretch receptors in the cervix. They are similar enough, how- through the CNS to oxytocin-secreting neurons. Oxytocin ever, for AVP to have slight oxytocic activity and for release stimulates the contraction of smooth muscle cells in oxytocin to have slight antidiuretic activity. They code for much larger mary glands and the female reproductive tract are discussed prohormones that contain the amino acid sequences for further in Chapter 39. AVP or oxytocin and for a 93-amino acid peptide called neurophysin (Fig. The neurophysin coded by the AVP gene has a slightly different structure than that coded by the oxytocin gene. Neurophysin is important in the pro- HORMONES OF THE ANTERIOR PITUITARY cessing and secretion of AVP, and mutations in the neuro- The anterior pituitary secretes six protein hormones, all of physin portion of the AVP gene are associated with central which are small, ranging in molecular size from 4. During the passage of the glands; they are called tropic (Greek meaning “to turn to”) or granules from the Golgi apparatus to axon terminals, pro- trophic (“to nourish”) hormones. For example, ACTH main- hormones are cleaved by proteolytic enzymes to produce tains the size of certain cells in the adrenal cortex and stim- AVP or oxytocin and their associated neurophysins. Similarly, TSH AVP or oxytocin secretion, action potentials are gener- maintains the size of the cells of the thyroid follicles and ated in these cells, triggering the release of AVP or oxy- stimulates these cells to produce and secrete the thyroid tocin and neurophysin from the axon terminals. The 4 3 substances diffuse into nearby capillaries and then enter two other tropic hormones, FSH and LH, are called go- the systemic circulation.
Each neurotransmitter acts on its own family of receptors and these receptors show a high degree of specificity for their transmitter discount 100 mg clomiphene free shipping. Thus order 25mg clomiphene otc, the receptors on which acetylcholine (ACh) works do not respond to glutamate (or any other neurotransmitter) and vice versa. Diversity of neurotransmitter action is provided by the presence of multiple receptor subtypes for each neurotransmitter, all of which still remain specific to that neurotransmitter. This principle is illustrated by the simple observations outlined in Neurotransmitters, Drugs and Brain Function. Webster &2001 John Wiley & Sons Ltd 58 NEUROTRANSMITTERS, DRUGS AND BRAIN FUNCTION Chapter 1 which showed that since muscarine mimicked some of the actions of ACh (but not all) while nicotine mimicked the other actions of ACh, then ACh probably acted on two distinct types of receptors. The fact that atropine antagonised the muscarinic effects of ACh but not the nicotinic effects, while tubocurarine blocked the nicotinic effects provided firm evidence for this concept. These simple qualitative observations by Langley and others at the beginning of the twentieth century led to the development of more quantitative pharmacological methods that were subsequently used to identify and classify receptors. These methods were based on the use of both (1) agonist and (2) antagonist drugs: (1) If a series of related chemicals, say noradrenaline, adrenaline, methyladrenaline and isoprenaline, are studied on a range of test responses (e. On the other hand, if, as Ahlquist first found in the 1940s, these compounds give a distinct order of potency in some of the tests, but the reverse (or just a different) order in others, then there must be more than one type of receptor for these agonists. In fact, careful quantitative analysis of the order of activity of the agonists in each test, and of the precise potency of antagonists (see Chapter 5 for quantitative detail) has often successfully indicated, although rarely proved, the presence of subclasses of a receptor type (e. The affinity of receptors for selective antagonists determined using the Schild method was a mainstay of receptor classifica- tion throughout the second half of the twentieth century. Thus, a muscarinic receptor can be defined as a receptor with an affinity for atropine of around 1 nM and the M1 subtype of muscarinic receptor can be identified as having an affinity of around 10 nM for the selective antagonist, pirenzepine while muscarinic receptors in the heart (M2 subtype) are much less sensitive to pirenzepine block (K $ 10À7 M). B Classification of receptors according to agonist potency can be problematic because agonist potency depends partly on the density of receptors in the tissue and therefore use of selective antagonists has become a mainstay of receptor identification and classification. The development of radioligand binding techniques (see Chapter 5 for principles) provided for the first time a means to measure the density of receptors in a tissue in addition to providing a measure of the affinity of drugs for a receptor and allowed the relative proportion of different receptors in a tissue to be estimated.
Neuropsychological Tests Fuller discussion of psychosocial issues in conditions affecting the nervous system Neuropsychological tests are procedures can be found in Chapter 3 generic 100mg clomiphene visa. The driver Information gained from these tests may of the other car was only slightly injured; be used for diagnosis discount 100mg clomiphene otc, monitoring of however, Mr. When admitted to the trauma unit, tion to assessing cognitive processes, most his Glasgow Coma Scale was recorded as neuropsychological tests also assess per- 9. While at the rehabil- tial abilities, and emotional and personal- itation center, he worked on learning how ity consequences of brain damage or to walk, talk, and regain physical strength dysfunction. Residuals from his head Examples of commonly used neuropsy- injury include mild dysarthria. In addi- chological tests are the Wechsler Intelli- tion, he has developed a seizure disorder, gence Scales, the Wechsler Memory Scales, having experienced several grand mal the Halstead-Reitan Neuropsychological seizures for which he is currently receiv- Test Battery, and the Luria Nebraska ing medication, which appears to control Neuropsychological Battery. PSYCHOSOCIAL ISSUES IN NERVOUS Questions SYSTEM CONDITIONS INVOLVING THE BRAIN 1. What other potential residual effects might you expect resulting from Mr. What speciﬁc accommodations would tion and rehabilitation, he returned home, you expect Mr. What psychosocial issues might you at work, was taken to the emergency consider in Mr. Physical Medicine and Rehabilitation; A comparison of acute and postdischarge predic- State of the Art Reviews, 6, 1–19. Rehabilitation Counseling Bulletin, spective: Review of results of a community-based 47(2), 112–120, 122. New York: Demos mild traumatic brain injury: A review of current Publications. Mild traumatic brain injury traumatic brain injury: Coma, the vegetative state, in persons with multiple trauma: The problem of and the minimally responsive state.