By F. Sancho. Lincoln Memorial University. 2018.
Learning and re- brain for memory formation implicates acetylcholine as a membering new motor skills and habits requires the stria- major transmitter in cognitive function and learning and tum cheap 0.25mg lanoxin fast delivery, motor areas of the cortex order 0.25mg lanoxin with visa, and the cerebellum discount lanoxin 0.25 mg overnight delivery. The basal forebrain region contains prominent tional associations require the amygdala lanoxin 0.25 mg on line. Conditioned populations of cholinergic neurons that project to the reflexes require the cerebellum. Loss of cholinergic function is associated with dementia, an impairment of memory, abstract think- ing, and judgment (see Clinical Focus Box 7. Other cholinergic neurons include motor neurons and autonomic preganglionic neurons, as well as a major interneuronal pool in the striatum. Basal forebrain nuclei Hypothalamus Language and Speech Are Coordinated in Midbrain Specific Areas of Association Cortex Pedunculopontine Pons nucleus The ability to communicate by language, verbally and in Medulla writing, is one of the most difficult cognitive functions to FIGURE 7. Cholinergic neurons in Thus, our knowledge of language processing in the brain the basal forebrain nuclei innervate all regions of the cerebral cor- has been inferred from clinical data by studying patients tex. Cholinergic neurons in the brainstem’s pedunculopontine nu- with aphasias—disturbances in producing or understand- cleus provide a major input to the thalamus and also innervate the brainstem and spinal cord. Cholinergic interneurons are found in ing the meaning of words—following brain injury, surgery, the basal ganglia. Not shown are peripherally projecting neurons, or other damage to the cerebral cortex. Both of these areas are located in association cortex, adjacent to cortical areas that are essential in language communica- (Fig. Wernicke’s area is in the parietal-temporal-occipital ically as basal forebrain nuclei and include the septal nu- association cortex, a major association area for processing clei, the nucleus basalis, and the nucleus accumbens. An- sensory information from the somatic sensory, visual, and other major cholinergic projection derives from a region auditory cortices. Broca’s area is in the prefrontal associ- of the brainstem reticular formation known as the pe- ation cortex, adjacent to the portion of the motor cortex dunculopontine nucleus, which projects to the thala- that regulates movement of the muscles of the mouth, mus, spinal cord, and other regions of the brainstem. A definitive diagnosis of AD is not possible un- unknown and there is no cure. In 1999, an estimated 4 mil- til autopsy, but the constellation of symptoms and disease lion people in the United States suffered from AD. The aging of the baby boom population has Microscopic pathology indicates two classic signs of the made AD one of the fastest growing diseases; estimates disease even at the earliest stages: the presence of senile indicate that by the year 2040, some 14 million people in plaques (SPs) and neurofibrillary tangles (NFTs). Early on, there is mild memory impairment; as the disease While many neurotransmitter systems are implicated progresses, memory problems increase and difficulties in AD, the most consistent pathology is the loss or atro- with language are generally observed, including word- phy of cholinergic neurons in the basal forebrain. Many pa- ications that ameliorate the cognitive symptoms of AD tients also exhibit difficulty with visuospatial tasks. These observations sonality changes are common, and patients become emphasize the importance of cholinergic systems in cog- disoriented as the memory problems worsen. CHAPTER 7 Integrative Functions of the Nervous System 133 Primary Primary somatic coordinate aspects of understanding and executing speech motor cortex sensory cortex and language skills. Patients with a defect in Broca’s area show evidence of comprehending a spoken or written word but they are not able to say the word. In contrast, patients with damage in Wernicke’s area can produce speech, but the words they put together have Primary little meaning. This dominance is observed in left-handed as well as auditory cortex right-handed individuals. Moreover, it is language that is lateralized, not the reception or production of speech. Wernicke’s and Broca’s areas and the pri- Thus native signers (individuals who use sign language) FIGURE 7. REVIEW QUESTIONS DIRECTIONS: Each of the numbered (A) Adrenaline removal of a tumor and concomitant items or incomplete statements in this (B) Leptin destruction of surrounding tissue, a section is followed by answers or by (C) Melanocyte-stimulating hormone patient’s hypothalamus no longer completions of the statement.
Atresia is a continuous process and can occur at short prophase to become arrested in metaphase buy lanoxin 0.25 mg on-line. During a woman’s life- stage lanoxin 0.25mg lowest price, the secondary oocyte is expelled from the graafian time approximately 400 to 500 follicles will ovulate; those follicle 0.25mg lanoxin otc. In re- are the only follicles that escape atresia generic lanoxin 0.25 mg on line, and they represent sponse to penetration by a spermatozoon during fertiliza- a small percentage of the 1 to 2 million follicles present at tion, meiosis 2 resumes and is rapidly completed. The cause of follicular atresia is likely due to lack of unequal cell division soon follows, producing a small sec- gonadotropin support of the growing follicle. For example, ond polar body (1n DNA) and a large fertilized egg, the at the beginning of the menstrual cycle, several follicles are zygote (2n DNA, 1n from the mother and 1n from the fa- selected for growth but only one follicle, the dominant fol- ther). The first and second polar bodies either degenerate licle, will go on to ovulate. Because the dominant follicle or divide, yielding small nonfunctional cells. If fertilization has a preferential blood supply, it gets the most FSH (and does not occur, the secondary oocyte begins to degenerate LH). Other reasons for the lack of gonadotropin support of within 24 to 48 hours. FOLLICLE SELECTION AND OVULATION During atresia, granulosa cell nuclei become pyknotic (referring to an apoptotic process characterized by DNA The number of ovulating eggs is species-specific and is in- laddering), and/or the oocyte undergoes pseudomatura- fluenced by genetic, nutritional, and environmental factors. During the early stages of In humans, normally only one follicle will ovulate, but mul- oocyte death, the nuclear membrane disintegrates, the tiple ovulations in a single cycle (superovulation) can be chromatin condenses, and the chromosomes form a induced by the timed administration of gonadotropins or metaphase plate with a spindle; the term pseudomaturation is antiestrogens. The mechanism by which one follicle is se- appropriate because these oocytes are not capable of suc- lected from a cohort of growing follicles is poorly under- cessful fertilization. It occurs during the first few days of the cycle, im- theca cells, the theca layer may undergo hyperplasia and mediately after the onset of menstruation. Once selected, CHAPTER 38 The Female Reproductive System 675 the follicle begins to grow and differentiate at an exponen- is also an increased production of follicular fluid, disaggrega- tial rate and becomes the dominant follicle. The basement membrane separating tors contribute to atresia in the nonselected follicles. One is theca cells from granulosa cells begins to disintegrate, gran- the suppression of plasma FSH in response to increased estra- ulosa cells begin to undergo luteinization, and blood vessels diol secretion by the dominant follicle. The dominant follicle is protected from a stigma, the point on the follicle that actually ruptures. As fall in circulating FSH levels because it has a healthy blood ovulation approaches, the follicle enlarges and protrudes supply, FSH accumulated in the follicular fluid, and an in- from the surface of the ovary at the stigma. In response to the creased density of FSH receptors on its granulosa cells. An- LH surge, plasminogen activator is produced by theca and other factor in selection is the accumulation of atretogenic granulosa cells of the dominant follicle and converts plas- androgens, such as DHT, in the nonselected follicles. Plasmin is a proteolytic enzyme that increase in DHT changes the intrafollicular ratio of estrogen acts directly on the follicular wall and stimulates the produc- to androgen and antagonizes the actions of FSH. On day 9 or 10 of the cycle, the vascu- wall facilitates the rupture of the follicle. The extrusion of the larity of the dominant follicle is twice that of the other antral oocyte-cumulus complex is aided by smooth muscle con- follicles, permitting a more efficient delivery of cholesterol traction. At the time of rupture, the oocyte-cumulus complex to theca cells and better exposure to circulating go- and follicular fluid are ejected from the follicle. At this time, the main source of circulating The LH surge triggers the resumption of the first meiosis. Since estradiol is the pri- Up to this point, the primary oocyte has been protected by mary regulator of LH and FSH secretion by positive and neg- unknown factors within the follicle from premature cell divi- ative feedback, the dominant follicle ultimately determines sion. Within a couple of hours after the initiation of circulating estradiol, and it causes multiple changes in the of the LH surge, the production of progesterone, androgens, dominant follicle, which occur within a relatively short time.
Cells in ties generic lanoxin 0.25 mg online, or intractable pain and/or paresthesias (as in the thalamic syndrome) discount lanoxin 0.25mg fast delivery, these latter centers that contain serotonin and enkephalin send may result from vascular lesions in the posterolateral thalamus cheap lanoxin 0.25 mg online. Serotonergic raphespinal called thalamic pain may also be experienced by patients who have or enkephalinergic reticulospinal ﬁbers may inhibit primary sensory brainstem lesions lanoxin 0.25mg visa. Abbreviations A Input from upper extremity regions PRG Posterior (dorsal) root ganglion ALS Anterolateral system Py Pyramid AWCom Anterior (ventral) white commissure RaSp Raphespinal ﬁbers CC Crus cerebri RB Restiform body IC Internal capsule RetF Reticular formation (of midbrain) L Input from lower extremity regions RetTh Reticulothalamic ﬁbers MCP Middle cerebellar peduncle RNu Red nucleus ML Medial lemniscus S Input from sacral regions MLF Medial longitudinal fasciculus SC Superior colliculus Nu Nuclei SpRet Spinoreticular ﬁbers NuDark Nucleus of Darkschewitsch SpTec Spinotectal ﬁbers NuRa,d Nucleus raphe, dorsalis SpTh Spinothalamic ﬁbers NuRa,m Nucleus raphe, magnus T Input from thoracic regions PAG Periaqueductal gray VPL Ventral posterolateral nucleus of thalamus PoCGy Postcentral gyrus I-VIII Laminae I-VIII of Rexed PPGy Posterior paracentral gyrus Review of Blood Supply to ALS STRUCTURES ARTERIES ALS in Spinal Cord penetrating branches of arterial vasocorona and branches of central (see Figures 5–6 and 5–14) ALS in Medulla caudal third, vertebral; rostral two-thirds, posterior inferior cerebellar (see Figure 5–14) ALS in Pons long circumferential branches of basilar (see Figure 5–21) ALS in Midbrain short circumferential branches of posterior cerebral, superior cerebellar (see Figure 5–27) VPL thalamogeniculate branches of posterior cerebral (see Figure 5–38) Posterior Limb of IC lateral striate branches of middle cerebral (see Figure 5–38) Sensory Pathways 181 Anterolateral System Trunk Thigh Leg Somatosensory cortex PPGy Foot Post. Postsynaptic-posterior column ﬁbers Clinical Correlations: The postsynaptic-posterior column and originate primarily from cells in lamina IV (some cells in laminae III and spinocervicothalamic pathways are not known to be major circuits in V-II also contribute), ascend in the ipsilateral dorsal fasciculi, and end the human nervous system. However, the occurrence of these ﬁbers in their respective nuclei in the caudal medulla. Patients that have re- collaterals project to a few other medullary targets. The axons partial relief, or there may be a recurrence of pain perception within of these cells ascend in the posterior part of the lateral funiculus (this is days or weeks. Although the cordotomy transects ﬁbers of the antero- sometimes called the dorsolateral funiculus) and end in a topographic lateral system (the main pain pathway), this lesion spares the posterior fashion in the lateral cervical nucleus: lumbosacral projections termi- horn, posterior columns, and spinocervical ﬁbers. Consequently, the nate posterolaterally and cervical projections anteromedially. Cells of recurrence of pain perception (or even the partial relief of pain) in the posterior column nuclei and the lateral cervical nucleus convey in- these patients may be explained by these postsynaptic-dorsal column formation to the contralateral thalamus via the medial lemniscus. Through these connections, Neurotransmitters: Glutamate ( ) and possibly substance P some nociceptive (pain) information may be transmitted to the ventral ( ) are present in some spinocervical projections. Because some cells posterolateral nucleus and on to the sensory cortex, via circuits that by- in laminae III-V have axons that collateralize to both the lateral cervi- pass the anterolateral system and are spared in a cordotomy. Abbreviations ALS Anterolateral system AWCom Anterior (ventral) white commissure FCu Cuneate fasciculus FGr Gracile fasciculus IAF Internal arcuate ﬁbers LCerNu Lateral cervical nucleus ML Medial lemniscus NuCu Cuneate nucleus NuGr Gracile nucleus PRG Posterior (dorsal) root ganglion Review of Blood Supply to Dorsal Horn, FGr, FCu, LCerNu STRUCTURES ARTERIES FGr, FCu in Spinal Cord penetrating branches of arterial vasocorona and some branches from central (sulcal) (see Figure 5–6) LCerNu penetrating branches of arterial vasocorona and branches from central (see Figure 5–6) NuGr NuCu posterior spinal (see Figure 5–14) Sensory Pathways 183 Postsynaptic-Posterior (Dorsal) Column System and the Spinocervicothalamic Pathway FGr ML Other FCu brainstem targets IAF NuCu PRG NuGr FGr FCu Laminae IV (III-VII) PRG ALS FGr FGr Laminae IV (III-VII) ALS ML LCerNu AWCom FGr FCu Laminae IV (III-VII) PRG PRG Dorsolateral region of lateral funiculus ALS 184 Synopsis of Functional Components, Tracts, Pathways, and Systems Trigeminal Pathways 7–7 The distribution of general sensory (GSA) information origi- tile sensation from the ipsilateral face, oral cavity, and teeth; 2) ipsilat- nating on cranial nerves V (trigeminal), VII (facial), IX (glossopharyn- eral paralysis of masticatory muscles; and 3) ipsilateral loss of the geal), and X (vagus). Damage to peripheral portions of the trigeminal nerve chief sensory nucleus, but most form the spinal trigeminal tract and may be traumatic (skull fracture, especially of supraorbital and infraor- end in the spinal trigeminal nucleus. The deﬁcit would reﬂect the peripheral portion of the trigem- chief sensory nucleus give rise to crossed anterior (ventral) trigeminothal- inal nerve damaged. Collaterals of these ascending ﬁbers inﬂuence the hy- Trigeminal neuralgia (tic douloureux) is a severe burning pain restricted poglossal, facial (corneal reﬂex, supraorbital, or trigeminofacial reﬂex), and to the peripheral distribution of the trigeminal nerve, usually its V2 trigeminal motor nuclei; mesencephalic collaterals are involved in the (maxillary) division. This pain may be initiated by any contact to areas jaw reﬂex, also called the jaw-jerk reﬂex. Collaterals also enter the dorsal of the face such as the corner of the mouth, nose, lips, or cheek (e. The attacks (tearing/lacrimal reﬂex), and the nucleus ambiguus and adjacent reticular frequently occur without warning, may happen only a few times a formation (sneezing reﬂex). Uncrossed posterior (dorsal) trigeminothal- month to many times in a single day, and are usually seen in patients amic ﬁbers arise from posterior regions of the chief sensory nucleus. One probable cause of trigeminal neuralgia is Neurotransmitters: Substance P ( )-containing and cholecys- compression of the trigeminal root by aberrant vessels, most com- tokinin ( )-containing trigeminal ganglion cells project to the spinal monly a loop of the superior cerebellar artery (see page 41). Glutamate causes may include tumor, multiple sclerosis, and ephaptic transmission ( ) is found in many trigeminothalamic ﬁbers arising from the chief sen- (ephapse) in the trigeminal ganglion. This is the most common type of sory nucleus and the pars interpolaris of the spinal nucleus. The locus ceruleus (noradrenergic ﬁbers) and served by the posterior inferior cerebellar artery (PICA). Conse- the raphe nuclei (serotonergic ﬁbers) also project to the spinal nucleus. This is a loss of pain and thermal sensations on one side spinal nucleus, and enkephalinergic ﬁbers are found in the nucleus am- of the body and the opposite side of the face. Pontine gliomas may pro- biguus and in the hypoglossal, facial, and trigeminal motor nuclei. Abbreviations ALS Anterolateral system MesNu Mesencephalic nucleus VPM Ventral posteromedial nucleus CC Crus cerebri ML Medial lemniscus of thalamus CSNu Chief (principal) sensory OpthV Ophthalmic division of VTTr Ventral trigeminothalamic nucleus trigeminal nerve tract DTTr Dorsal trigeminothalamic tract RB Restiform body FacNu Facial nucleus RetF Reticular formation Ganglia GSA General somatic afferent RNu Red nucleus 1 Trigeminal ganglion HyNu Hypoglossal nucleus SpTNu Spinal trigeminal nucleus 2 Geniculate ganglion IC Internal capsule SpTTr Spinal trigeminal tract 3 Superior of glossopharyngeal ManV Mandibular division of TriMoNu Trigeminal motor nucleus 4 Superior of vagus trigeminal nerve TMJ Temporomandibular joint MaxV Maxillary division of trigeminal VPL Ventral posterolateral nucleus nerve of thalamus Review of Blood Supply to SpTT, SpTNu, and Trigeminothalamic Tracts STRUCTURES ARTERIES SpTTr and SpTNu caudal third, vertebral; rostral two-thirds, posterior in Medulla inferior cerebellar (see Figure 5–14) SpTTr and SpTNu in Pons long circumferential branches of basilar (see Figure 5–21) Trigeminothalamic Fibers short circumferential branches of posterior cerebral and in Midbrain superior cerebellar (see Figure 5–27) VPM thalamogeniculate branches of posterior cerebral (see Figure 5–38) Posterior Limb of IC lateral striate branches of middle cerebral (see Figure 5–38) Sensory Pathways 185 Trigeminal Pathways Thigh Somatosensory Leg cortex Foot Posterior limb, IC VPM DTTr VTTr MesNu Origin of SA Data Position of Trigeminal tracts CSNu 1 GSA, skin of face, forehead and part of scalp; mem- branes of nose and of MesNu nasal, maxillary and frontal sinuses; oral cavity, teeth; ALS ant. Input from 7,9,10 wall and floor of external SpTTr auditory meatus; tympanic RB membrane; dura of post.