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The motor innervation of the femoral nerve is to the anterior muscles of the thigh cheap 20mg levitra super active with amex, including the iliopsoas and sarto- rius muscles and the quadriceps femoris group discount levitra super active 20 mg overnight delivery. It provides cutaneous innerva- tion to the medial thigh and motor innervation to the adductor sacral: L buy discount levitra super active 40 mg. Peripheral Nervous © The McGraw−Hill Anatomy order 20 mg levitra super active with visa, Sixth Edition Coordination System Companies order levitra super active 40mg overnight delivery, 2001 422 Unit 5 Integration and Coordination Femoral nerve Obturator nerve FIGURE 12. Peripheral Nervous © The McGraw−Hill Anatomy, Sixth Edition Coordination System Companies, 2001 Chapter 12 Peripheral Nervous System 423 Lumbosacral trunk L5 S1 Superior gluteal nerve Inferior gluteal S2 nerve Common fibular nerve S3 Tibial nerve S4 Sciatic nerve S5 Posterior cutaneous femoral nerve Co1 Pudendal nerve Roots Anterior divisions Posterior divisions FIGURE 12. Sciatica is characterized by sharp pain in the gluteal region that extends down and leg, and branches in the foot to form the medial and lateral the posterior side of the thigh. The cutaneous innervation of the into the buttock may injure the sciatic nerve itself. Even a temporary tibial nerve is to the calf of the leg and the plantar surface of the compression of the sciatic nerve as a person sits on a hard surface for foot. The motor innervation of the tibial nerve is to most of the a period of time may result in the perception of tingling throughout the limb as the person stands up. The common fibular nerve (peroneal nerve) arises from Knowledge Check the posterior division of the sacral plexus, extends through the 10. What are the four spinal nerve posterior region of the thigh, and branches in the upper portion plexuses and which spinal nerves contribute to each? Distinguish between a posterior ramus and an nerve and its branches is to the anterior and lateral leg and to anterior ramus. Construct a table that lists the plexus of origin and the The sciatic nerve in the buttock lies deep to the gluteus max- general region of innervation for the following nerves: imus muscle, midway between the greater trochanter and the (a) pudendal, (b) phrenic, (c) femoral, (d) ulnar, (e) me- ischial tuberosity. Because of its position, the sciatic nerve is of tremendous clinical importance. A posterior dislocation of the hip joint dian, (f) sciatic, (g) saphenous, (h) axillary, (i) radial, will generally injure the sciatic nerve. Peripheral Nervous © The McGraw−Hill Anatomy, Sixth Edition Coordination System Companies, 2001 424 Unit 5 Integration and Coordination Superior gluteal nerve Superior piriform foramen Posterior surface of sacrum Piriformis muscle Inferior gluteal nerve Common peroneal nerve Inferior piriform foramen Tibial nerve Posterior femoral Sciatic nerve cutaneous nerve Sacrotuberous ligament Gluteus maximus muscle (laterally reflected) FIGURE 12. Peripheral Nervous © The McGraw−Hill Anatomy, Sixth Edition Coordination System Companies, 2001 Chapter 12 Peripheral Nervous System 425 Tibial nerve Fibular nerve FIGURE 12. Peripheral Nervous © The McGraw−Hill Anatomy, Sixth Edition Coordination System Companies, 2001 Developmental Exposition nerve (C1), all of the spinal nerves are associated with specific The Peripheral dermatomes. In the appendages, however, adjacent dermatome inner- Nervous System vations overlap. The apparently uneven dermatome arrangement in the appendages is due to the uneven rate of nerve growth into the limb buds. Actually, the limbs are segmented, and der- EXPLANATION matomes overlap only slightly. Development of the peripheral nervous system produces the pat- tern of dermatomes within the body (exhibit I). Because adjacent dermatomes overlap in the neurons of a single spinal nerve or cranial nerve V. Most of the appendages, at least three spinal nerves must be blocked to pro- scalp and face is innervated by sensory neurons from the trigemi- duce complete anesthesia in these regions. With the exception of the first cervical ing dermatomes provide clues about injury to the spinal cord or specific spinal nerves. If a dermatome is stimulated but no sensa- tion is perceived, the physician can infer that the injury involves dermatone: Gk. C2 C2 C3 C3 C4 C4 C5 C5 C6 C7 C8 T1 T1 C6 T12 T1 L1 T12 L5 S1 S2 L1 S3 S2 S4 C8 L2 S5 C7 S3 L3 L1 L2 L4 L3 L5 S1 L4 L5 (a) (b) EXHIBIT I The pattern of dermatomes within the body and the peripheral distribution of spinal nerves. Peripheral Nervous © The McGraw−Hill Anatomy, Sixth Edition Coordination System Companies, 2001 Chapter 12 Peripheral Nervous System 427 Receptor (in skin) Center (association White neuron) Posterior matter (dorsal) Cell body of neuron Sensory neuron Motor neuron Gray Spinal cord matter Anterior (ventral) Effector (muscle) FIGURE 12. Im- pulses are conducted over a short route from sensory to motor The conduction pathway of a reflex arc consists of a receptor, a neurons, and only two or three neurons are involved. The five sensory neuron, a motor neuron and its innervation in the PNS, components of a reflex arc are the receptor, sensory neuron, cen- and one or more association neurons in the CNS. The receptor includes the den- provides the mechanism for a rapid, automatic response to a po- drite of a sensory neuron and the place where the nerve impulse tentially threatening stimulus. The sensory neuron relays the impulse through the Objective 8 Define reflex arc and list its five components. The center is located within the CNS and usually involves one or more association neurons (interneu- Objective 9 Distinguish between the various kinds of reflexes. It is here that the arc is made and other impulses are sent through synapses to other parts of the body.

In (b) 40mg levitra super active with amex, the transmembrane topology of the ionotropic glutamate receptors is shown cheap levitra super active 40 mg on-line. TM2 creates a pore-forming loop which penetrates into the cell membrane from the intracellular side cheap 40 mg levitra super active with amex. As illustrated below generic 20 mg levitra super active, the likely stoichiometry of the glutamate receptors is a tetramer generic levitra super active 20 mg on line. The exact contribution of TM1, TM3 or TM4 to forming the ion channel is uncertain. These subunits cross the cell membrane only twice and the ion channel is probably formed by a short polypeptide loop entering the membrane from the outside. The exact stoichiometry of the P2X receptors is uncertain but current evidence supports the suggestion that they are trimers agonist binding site is located in the amino terminal domain before the start of TM1 and the ion channel is formed by the TM2 domains of each subunit which come together to make up the complete receptor. Thus the amino acids in TM2 determine the ion conductance properties of the channel. For GABA and glycine receptors a Cl7 channel is formed while for the other ion channel receptors, the channel is largely cation non-selective for monovalent ions such as Na‡ and K‡ and is often also permeable to calcium. One of the key differences between different ion channel receptors for glutamate, ACh, 5-HT and ATP is in their relative permeability to calcium and this is controlled by the amino acids which line the ion channel. The ionotropic glutamate receptors (kainate, AMPA and NMDA) are formed by subunits which are predicted to cross the cell membrane three times (Fig. The ionotropic glutamate receptor subunits have a large extracellular amino terminal domain and a long intracellular carboxy terminal domain (Fig. The P2X receptor subunits are unusual in having only two transmembrane domains with both the amino terminal and carboxy terminal located intracellularly. The ion channel is proposed by analogy with the structure of some potassium channels to be formed by a short loop which enters the membrane from the extracellular side (North and Surprenant 2000). Subunit stoichiometry The ion channel receptors are multi-subunit proteins which may be either homomeric (made up of multiple copies of a single type of subunit) or heteromeric (composed of more than one subunit type). These subunits come together after synthesis in the endoplasmic reticulum to form the mature receptor. A receptor composed of two a and three b subunits is therefore denoted as having a stoichiometry of a2b3. This can cause confusion when related subunits are given sequential numbers: b1, b2, b3, etc. The convention is there- fore that subunits are numbered normally while stoichiometry is indicated by subscripts so that a pentamer of a4 and b3 subunits might have a stoichiometry of a42b33. NICOTINIC RECEPTORS All receptors in the 4-TM domain family are thought to form pentameric receptors in which five subunits (Fig. Their structure has been most extensively studied in the case of the nicotinic acetylcholine receptor (analogous to the muscle endplate receptor) from Torpedo electroplaque (Unwin 2000) where there is now a detailed knowledge of the receptor in both resting and active conformations. The muscle receptor has a subunit stoichiometry of two a subunits, providing the agonist binding sites, and three other subunits (b, g and d). In adult muscle an e subunit is present instead of the g subunit which is found in the foetal-type receptor. The five subunits are arranged like the staves of a barrel around the central channel. Binding of ACh to the a subunits initiates a conformational change in the protein which, by causing rotation of all five TM2 domains lining the pore, opens the ion channel. Diversity among neuronal nicotinic receptors is generated by having nine more different a subunits (a2±a10) and three further b subunits (b2±b4). These receptors are activated by nicotine and blocked by the antagonists hexamethonium, mecamylamine and trimetaphan, and the erythrina alkaloid dihydro-b-erythroidine. The neuronal nicotinic receptors are found in autonomic ganglia and in the brain may be either heteromeric (e. The a7 receptor is likely to be the source of the a-bungarotoxin binding sites in the brain observed in autoradiograms of 123I-a- bungarotoxin binding to brain sections (Clarke 1992) and a-bungarotoxin sensitive nicotinic receptors have been shown in a number of studies to stimulate transmitter release from nerve terminals such as dopaminergic terminals in the striatum and glutamatergic terminals in the cortex. Its main functional role may therefore be as a presynaptic receptor regulating transmitter release. It has a high affinity for nicotine and so may mediate some of the central effects of nicotine.

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Based on the clinical signs discount levitra super active 40mg free shipping, what basic physiological princi- ular menstrual cycles of 26 to 28 days in length buy levitra super active 20 mg. Serum LH should be measured band’s semen analysis reveals a semen volume of 4 mL; pH during the anticipated preovulatory period discount levitra super active 20 mg on line. Low levels of LH may lead to an un- 26 days versus 28 days) safe 20mg levitra super active, the wife’s plasma progesterone ruptured dominant follicle that fails to ovulate but luteinizes discount levitra super active 40 mg on-line, level during the midluteal phase is assessed and determined leading to progesterone levels in the normal range for the to be 10 ng/mL, which is considered normal (4 to 20 ng/mL, luteal phase. Therapies such as gonadotropins and clomiphene why the patient is not able to get pregnant? Based on the hormone measurements, what treatment development, estradiol secretion, and ovulation. Estradiol should be measured at the end of the anticipated ferred over LH and GnRH for ovulation induction because of follicular phase. APPENDIX A Answers to Review Questions the action of either adenylyl or guanylyl cyclase on ATP or GTP, respectively. For example, cAMP Chapter 1 can activate protein kinase A, which will phosphory- 1. In a steady state, the amount or con- late its substrates; cGMP activates protein kinase G, centration of a substance in a compartment does not which phosphorylates a different set of substrates. Although there may be though signal transduction in sensory tissues involves considerable movements into and out of the compart- both cAMP and cGMP, cGMP has a more important ment, there is no net gain or loss. Phospholipase body often do not represent an equilibrium condition, C activation is coupled to the activation of a G protein but they are displaced from equilibrium by the con- (Gq), not to cAMP or cGMP. The increase in plasma insulin lowers scriptional regulators found in the cytoplasm or in the the plasma glucose concentration back to normal and nucleus. These receptors are activated by the binding is an example of negative feedback. Negative feedback of steroid ligands that diffuse through lipid bilayers opposes change and results in stability. Activated steroid receptors me- back would produce a further increase in plasma glu- diate their effects by direct interaction with gene reg- cose concentration. Chemical equilibrium indicates a ulatory elements and do not activate G proteins or condition in which the rates of reactions in forward cause binding of IP3 to the IP3-gated calcium release and backward directions are equal. Steroid hor- bition occurs when the products of a chemical reaction mone receptors do not have tyrosine kinase activity slow the reaction (for example, by inhibiting an en- and do not cause the phosphorylation of tyrosine zyme) that produces them. Steroid hormone receptors volves a command signal and does not directly sense are not linked to activation of the MAP kinase path- the regulated variable (plasma glucose concentration). The EGF receptor is a tryosine kinase of cells; upon binding of estrogen, they move to the receptor; therefore, an inhibitor of tyrosine kinases nucleus to bind to estrogen response elements to acti- should have the desired effect. Cardiac muscle cells have many gap crease intracellular levels of cAMP, but this is not the junctions that allow the rapid transmission of electrical second messenger problem here. An EGF agonist activity and the coordination of heart muscle contrac- would increase signaling along the EGF pathway and tion. Gap junctions are pores composed of paired con- would increase the problem, causing an undesired ef- nexons that allow the passage of ions, nucleotides, and fect. Likewise, a phosphatase inhibitor would slow the other small molecules between cells. Inositol trisphosphate (IP3) and dia- tain the activated state of the EGF pathway. Second messengers are a class of sig- phospholipase C (PLC) on PIP2, phosphatidylinositol naling molecules generated inside cells in response to 4,5-bisphosphate. DAG is important for the ac- always available, signal transduction pathways could tivation of protein kinase C, not PLC. The response to a second messenger receptors are activated by the binding of ligands, such varies depending on the cell type because each cell as hormones or growth factors, not by IP3 or DAG. IP3 type differs with respect to the number and comple- can indirectly activate calcium-calmodulin-dependent ment of receptors, effectors, and downstream targets. The activation of tyrosine kinase re- only tyrosine kinase receptors, are coupled to second ceptors often results in a cellular response that is in- messenger generating systems. Cyclic nucleotides are generated by ceptors do not have constitutively active receptors; if 707 708 APPENDICES this were true, there could be no regulation of signal- 7. The activation of ras occurs indirectly by the acti- the ion channel in this example. Ion pumps and Na vation of adapter molecules (Grb2 and SOS) that asso- solute-coupled transporters are examples of active ciate with phosphorylated tyrosine residues in the transport systems, not Na channels.

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The (A) Left substantia nigra examination reveals that the boy has rigidity buy 40 mg levitra super active visa, athetoid movements (B) Left subthalamic nucleus (athetosis) buy discount levitra super active 40mg online, and difficulty speaking buy discount levitra super active 20mg line. His ophthalmologist reports (C) Right motor cortex that the boy has a greenish-brown ring at the corneoscleral margin generic levitra super active 20 mg. The examination reveals that (E) Wilson disease the man is not able to perform rapid alternating movements with his left upper extremity order 40 mg levitra super active with visa, and is not able to touch his left index finger to his 65. A 32-year-old woman complains to her gynecologist that her nose because of a tremor that worsens as the finger approaches the breasts are tender and a white fluid issues from her nipples. When he walks, examination reveals that the woman is not pregnant (she had her he is unsteady with a tendency to fall to the left. He has no sensory ovaries removed at age 28 resultant to a diagnosis of ovarian can- deficits. Which of the following terms specifically designates the inability the midline portion of the optic chiasm. Based on the position of of this man to perform rapid alternating movements? Which of the following terms specifically designates this man’s in- ability to touch his nose with his index finger? Which of the following portions of the cerebellum have a close (A) Dysmetria structural and functional relationship with the vestibular appara- (B) Intention tremor tus and the vestibular nuclei? A 39-year-old woman presents with sustained and oscillating mus- on the deficits this man is experiencing, which of the following cle contractions that have twisted her trunk and extremities into represents the most likely location of this lesion? This woman is most likely suffer- (A) Basal nuclei on the left side ing from which of the following? Assuming this lesion to be the result of the occlusion of an artery, which of the following is the most likely candidate? A 21-year-old man is brought to the emergency department from the scene of an automobile collision. He has a compound fracture (A) Left anterior inferior cerebellar artery of the humerus, a fractured tibia, various cuts and bruises, and sig- (B) Left superior cerebellar artery nificant facial trauma. Cranial CT shows fractures of the bones of (C) Lenticulostriate arteries on the left the face and orbit on the left, and a total collapse of the optic canal (D) Right anterior inferior cerebellar artery on that side with probable transection of the optic nerve. Follow- (E) Right superior cerebellar artery ing an initial recovery period, which of the following would most likely be seen during an ophthalmologic examination? A 61-year-old woman complains to her family physician that the (A) A loss of both the direct and consensual pupillary re- muscles of her face sometimes twitch. The examination reveals sponse when the light is shown in the right eye that the woman has irregular and intermittent contractions of fa- (B) A loss of only the consensual pupillary response when cial muscles; sometimes these are painful. MRI shows an aberrant the light is shown in the right eye loop of an artery that appears to be compressing the facial nerve (C) A loss of the direct but not the consensual pupillary re- root. Which of the following is most likely the offending vessel in sponse when a light is shown in the left eye this case? A 27-year-old man presents with athetosis (athetoid movements), rigidity, and dysarthria. An 81-year-old man presents with a loss of pain, thermal sensa- has an obvious greenish-brown ring at the corneoscleral margin. CT shows a comparatively small showing which of the following would provide further, if not con- infarct representing the territory of one vessel. A 77-year-old man complains to his family physician that he is hav- (E) Upper cervical spinal cord ing trouble picking up his coffee cup, shaving with a safety razor, and picking up the checkers when playing with his grandson. The MRI of a 70-year-old man shows an infarcted area in the me- examination reveals that the man is unable to control the distance, dial medulla at a mid-olivary level on the left. This correlates power, or accuracy of a movement as the movement is taking with a loss of position sense from the man’s upper right extrem- place. Which of the following represents the location of the cell lowing most specifically describes this condition? The examination reveals a hemiplegia involving the left upper and lower extremities, sensory losses (pain, thermal sensations, and proprioception) on the left side of the body and 286 Q & A’s: A Sampling of Study and Review Questions with Explained Answers face, and a visual deficit in both eyes. MRI shows an area of infarction Answers for Chapter 7 consistent with the territory served by the anterior choroidal artery. The (B) Left nasal hemianopsia motor loss is ipsilateral to the damage and the sensory loss is con- (C) Left superior quadrantanopia tralateral; second order fibers conveying pain information cross in (D) Right homonymous hemianopsia the anterior white commissure ascending one to two spinal seg- (E) Right superior quadrantanopia ments in the process.

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