As would be expected of a part of the brain which integrates many different physiological functions, the various components of the hypothalamus have extensive, complex, and usually reciprocal connections with many regions of the forebrain, brainstem, and spinal cord. There are few large myelinated fibre tracts and only relatively recently have a variety of tracing techniques elucidated the more subtle connections.

Information about the light– dark cycle is passed to the hypothalamus via retino- hypothalamic fibres that originate from retinal ganglion cells and project to the suprachiasmatic nuclei. Olfactory inputs reach the hypothalamus from the pyriform cortex, amygdala, and orbitofrontal cortex; gustatory inputs from the brainstem and orbitofrontal cortex; both are involved in arousal and feeding be haviour. Visual and auditory inputs affect the hypothalamus after their significance has been assessed by the limbic system; nociceptive inputs influence hypothalamic function via brainstem connections and the medial forebrain bundle (MFB). The hypothalamus (especially the paraventricular nucleus) receives information from the viscera via ascending projections from the solitary nucleus of the medulla, which itself receives sensory input from the facial, glossopharyngeal, and vagus nerves. The MFB is actually a series of fibre bundles that run through the lateral part of the hypothalamus, interconnecting basal forebrain olfactory cortex, septum, and brainstem. The mesolimbic pathway of dopamine fibres from the ventral tegmental area to the nucleus accumbens is a component of the MFB and of the reward system. Together with mesocortical dopamine fibres it forms one of the ‘fountains’ that spread diffusely throughout the forebrain from the locus coeruleus (noradrenaline), raphe nuclei (serotonin), and basal nucleus of Meynert (acetyl choline). Brainstem reticular afferents from the central grey of the midbrain reach the hypothalamus via the dorsal longitudinal fasciculus.

T he fornix is a large bundle that connects the hippocampal formation with the septal cortex, anterior thalamus, hypothalamus, and mamillary bodies. Most of its fibres originate from pyramidal hippocampal neurons. Commissural fibres link the two hippocampi. Anteriorly, precommissural fibres pass rostral to the anterior commissure to the septal nuclei, the preoptic and dorsal hypothalamic areas; postcommissural fibres pass caudally through the lateral part of the hypothalamus to the medial mammillary nucleus. The fornix also carries cholinergic axons from the basal nucleus to the hippocampus; degeneration of these is a feature of Alzheimer dis ease. The nuclei of the amygdala are connected to many parts of the hypothalamus by two distinct pathways: the stria terminalis (which parallels the course of the fornix) ends in the bed nucleus of the stria terminalis and medial hypothalamus; the ventral amygdalofugal pathway links the basolateral amygdala to the lateral hypothalamus and MFB. These convey olfactory and visceral information to the hypothalamus and are important in mediating autonomic and endocrine responses particularly to aversive stimuli (‘fear reaction’).

Apart from its neuroendocrine efferents, most neural efferent connections of the hypothalamus are reciprocal to its afferents. Fibre tracts link hypothalamic autonomic centres to brainstem and spinal cord preganglionic autonomic neurons; descending fibres controlling sympathetic activity pass through the lateral medulla and lateral medullary (Wallenberg) lesions cause a Horner syn drome. Neurons of the posterior part of the PVN project oxytocin fibres to the sex dimorphic nuclei of the lumbosacral cord.

اخر الاخبار

اخبار العتبة العباسية المقدسة

تستمر طيلة شهر رمضان.. إقامة ختمة قرآنية تعليمية في مقام الإمام المهدي (عجل الله فرجه)

في مستشفى الكفيل.. جراحة دقيقة بين الأذن والدماغ تنقذ مريضة من التهاب حاد

المجمع العلمي يُطلق مسابقة (فرسان التنزيل الفرقية الأولى) ويقيم ختمات قرآنية في محافظة المثنى

ضمن أنشطته الإنسانية.. قسم الشؤون الفكرية يفتتح البئر الـ 72 في نيجيريا

المزيد

الآخبار الصحية

دراسة تحذر من الإفراط في ممارسة الرياضة.. كيف يضر دماءك؟

الطهي بزيت الزيتون.. مضر أم مفيد؟

دماغ الرضع في خطر.. دراسة تحذر من "العدو الخفي"

التمر بالحليب عند الإفطار.. "كنز صحي" في رمضان

المزيد

الآخبار التكنلوجية

أثر نفسي غير متوقع للرياضة.. مرتبط بالغضب

القمر يواصل الانكماش.. رصد تشققات حديثة على سطحه

إطلاق أول تطبيق مراسلة "مشفّر".. ثورة في عالم الدردشة

خلل تقني يؤجّل أول رحلة مأهولة إلى القمر منذ عقود

المزيد

مواضيع ذات صلة

Morphological and Functional Exploration Methodologies of the Central Nervous System

Parallels to brain control of thermoregulation

Glucose sensing and brain control of energy balance

Overview of brain control of glucose homeostasis in normal physiology

Neurally Mediated Syncope

Special Characteristics of Signal Transmission in Nerve Trunks

Peripheral nerves

خواص الإيعاز العصبي

العوامل التي تؤدي إلى تكون جهد الراحة

Astrocytes

المستقبلات الكولنيرجية والأدرينرجية

الجهاز العصبي الذاتي