[Headache associated with the use of personal protective equipment during the COVID-19 pandemic: a practical way to improve this condition]. / Cefalea asociada con el uso de equipo de protección personal durante la pandemia de la COVID-19: una forma práctica de mejorar esta condición.

TITLE: Cefalea asociada con el uso de equipo de protección personal durante la pandemia de la COVID-19: una forma práctica de mejorar esta condición.

Un encéfalo funcional integrado, no un encéfalo parcelado / An integrated functional brain, not a partitioned brain

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¿Nódulos axonales?. Réplica / Axonal nodes? Reply

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[The metabolic regulation of cerebral microcirculation]. / Regulación metabólica de la microcirculación cerebral.

AIM: To analyse the mechanisms involved in the microvascular metabolic regulation of cerebral blood flow. The article outlines the neuronal metabolism and mechanisms involved in functional hyperaemia and examines the contractile properties of brain microvasculature. It also discusses the role played by ion channels in pericytes and vascular smooth muscle and describes the signalling pathways involved in arteriolar and capillary vasodilatation or vasoconstriction. DEVELOPMENT: The blood-brain barrier and the close functional relations between neurons and astrocytes give rise to nerve tissue properties such as functional hyperaemia. In this mechanism the astrocytes act as a structural and functional 'bridge' between neurons and brain capillaries, and respond to synaptic activity by releasing vasoactive compounds, above all vasodilators. The metabolites derived from arachidonic acid, such as prostaglandins and epoxyeicosatrienoic acids, as well as the compounds that have traditionally been involved, such as nitric oxide and prostacyclin, are especially important. These substances are capable of extending to the capillaries and arterioles, where they alter the membrane potential and the contractibility of the pericytes and the smooth muscle of vessels. CONCLUSIONS: The functional interaction among neurons, astrocytes and capillaries in the central nervous system (called the 'neurovascular unit') is essential for the regulation of cerebral blood flow, since it links neuron-glial cell metabolic activity to the supply of energetic substrates from the microcirculation. Within this functional unit, astrocytes play a vital role by releasing vasoactive substances that are derived from or produced by neuronal activity.

Regulación metabólica de la microcirculación cerebral / The metabolic regulation of cerebral microcirculation

Objetivo. Analizar los mecanismos implicados en la regulación metabólica microvascular del flujo sanguíneo cerebral. Se describe el metabolismo neuronal y los mecanismos implicados en la hiperemia funcional, se examinan las propiedades contráctiles de la microvasculatura cerebral, se plantea el papel de los canales iónicos en los pericitos y el músculo liso vascular y se describen las vías de señalización implicadas en la vasodilatación o vasoconstricción arteriolar y capilar. Desarrollo. La barrera hematoencefálica y las estrechas relaciones funcionales entre neuronas y astrocitos generan propiedades al tejido nervioso, como la hiperemia funcional. En este mecanismo, los astrocitos actúan de ‘puente’ estructural y funcional entre neuronas y capilares cerebrales, respondiendo a la actividad sináptica mediante la liberación de compuestos vasoactivos, principalmente vasodilatadores. Son de especial importancia los metabolitos derivados del ácido araquidónico, como prostaglandinas y ácidos epoxieicosatrienoicos, además de los compuestos tradicionalmente implicados, como óxido nítrico y prostaciclina. Estas sustancias tienen la capacidad de difundir hasta los capilares y las arteriolas, donde alteran el potencial de membrana y la contractilidad de los pericitos y el músculo liso vascular. Conclusiones. La interacción funcional entre neuronas, astrocitos y capilares del sistema nervioso central (denominada ‘unidad neurovascular’) resulta esencial en la regulación del flujo sanguíneo cerebral, ya que asocia la actividad metabólica neurona-glía al suministro de sustratos energéticos desde la microcirculación. En esta unidad funcional, los astrocitos desempeñan un papel vital liberando sustancias vasoactivas derivadas o producidas a consecuencia de la actividad neuronal

Aim. To analyse the mechanisms involved in the microvascular metabolic regulation of cerebral blood flow. The article outlines the neuronal metabolism and mechanisms involved in functional hyperaemia and examines the contractile properties of brain microvasculature. It also discusses the role played by ion channels in pericytes and vascular smooth muscle and describes the signalling pathways involved in arteriolar and capillary vasodilatation or vasoconstriction. Development. The blood-brain barrier and the close functional relations between neurons and astrocytes give rise to nerve tissue properties such as functional hyperaemia. In this mechanism the astrocytes act as a structural and functional ‘bridge’ between neurons and brain capillaries, and respond to synaptic activity by releasing vasoactive compounds, above all vasodilators. The metabolites derived from arachidonic acid, such as prostaglandins and epoxyeicosatrienoic acids, as well as the compounds that have traditionally been involved, such as nitric oxide and prostacyclin, are especially important. These substances are capable of extending to the capillaries and arterioles, where they alter the membrane potential and the contractibility of the pericytes and the smooth muscle of vessels. Conclusions. The functional interaction among neurons, astrocytes and capillaries in the central nervous system (called the ‘neurovascular unit’) is essential for the regulation of cerebral blood flow, since it links neuron-glial cell metabolic activity to the supply of energetic substrates from the microcirculation. Within this functional unit, astrocytes play a vital role by releasing vasoactive substances that are derived from or produced by neuronal activity

[Vestibular nerves and nuclei throughout history]. / Los nervios y núcleos vestibulares en la historia.

Throughout the evolution of the concepts concerning the peripheral nerves, different ideas have dominated at different moments in history. The studies and demonstrations conducted in an attempt to further our knowledge of our own constitution and working at the same time enabled us to gain a better understanding of the make-up and specific functioning of the vestibular nerves, together with their central connecting elements in the brainstem: the vestibular nuclei. It may be that the first references to vestibular nerves are now lost in time, yet the Ancient Greeks already attempted to understand their functional nature by carrying out studies essentially focused on neuroanatomical aspects, but heavily influenced by philosophical concepts. It was not until the 18th century that researchers came to understand that there were differences between the vestibular nerve and the cochlear nerve --until then they were believed to be one single nerve. Another century went by before attempts were made to clarify the role it plays in balance and not in hearing. The differences between the distinct vestibular nuclei situated between the medulla oblongata and the pons were established in the 19th and 20th centuries when a number of authors, backed by previous microscopic studies, contributed to clarifying the fuzzy limits of cells separating the four classic nuclear groups and four others taken as being accessory.

[The vestibular organ throughout history]. / El organo vestibular en la historia.

AIMS AND DEVELOPMENT: Our aim is to attempt to create a chronologically ordered and coherent corpus of the apparently scarce information that exists about the history of the vestibular organ, a component of the inner ear situated on both sides of the head in the petrous temporal bone. Its job, at least in humans, is to transmit sensory information about movements of the head to components of the central nervous system. Some of its more common disorders lead to syndromes that implicitly entail balance disorders, such as the case of the syndrome described by Prosper Meni re in the 19th century. Without ruling out the possible ancestral knowledge of the vertiginous processes associated with the inner ear, our objective is to review some of the aspects that anatomists, physiologists and prominent physicists have been involved in throughout history, i.e. elements that appeared between the 18th and mid 20th century and which have led to a fuller understanding of the morphological and functional aspects of the fundamental apparatus involved in the detection of gravity and inertia, shared by vertebrates: the vestibular organ.

[Neurobiological relations and aging]. / Relaciones neurobiológicas y envejecimiento.

Of the different aspects of a series of neurobiological changes that take place throughout the life cycle of an individual, in this paper we examine those involved in the aging process. These changes have been associated on different scales, including on a macroscopic level, that take into account variations in the shape, weight and volume of the brain and other encephalic structures. A part of the information about the weight seems to be incompatible and hence its incompatibility has been questioned and argued from a quantitative perspective. The functional option has been proposed as an alternative in the maintenance of normal brain functioning, as have changes on the microscopic scale in neuronal processes, the reduction in number of neurons in certain parts of the brain, which has also been questioned for the case of olfactory nerve fibres, and finally changes that take place on the molecular scale in the alteration of some neurotransmitters in certain parts, modifications suffered by mitochondrial enzymes and others that depend on the genome. These aspects have all been taken into consideration along with a resulting physiological relation in an attempt to gain a slightly more holistic, although still fragmented, view of the process, and to consider neoteny as an evolutionary strategy in the human species that serves to maintain brain functioning.

Proceso odontoideo (apófisisis odontoides) / Odontoid process (dens axis)

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