Recetores sensoriais

Question 1

Que tipo de recetores existem?

Answer 1

Os recetores sensoriais estão espalhados pelo corpo e e ativam-se perante inputs exterocetivos, interocetivos e propriocetivos. cada recetor está especializado em detetar estímulo mecânico, químico, nocicetivo e térmico. É importante referir que, em geral, os recetores não transmitem apenas uma sensação específica.

Question 2

Como são classificadas as vias sensoriais ascendentes?

Answer 2

São classificadas de acordo com os seus componentes funcionais e sua localização.
As duas categorias funcionais são o sistema geral de aferentes somáticos (GSA) e o sistema geral de aferentes viscerais (GVA).
Anatomicamente, classificam-se em sistema anterolateral (ALS); coluna dorso-medial lemniscal (DCML); e vias somatossensoriais para o cerebelo.

Question 3

O que é o sistema geral de aferentes somáticos (GSA)?

Answer 3

É uma das categorias funcionais das vias que transmite informação sensorial - como o toque, pressão, vibração, dor, temperatura, alongamento, e o senso de posição das estruturas somáticas.

Question 4

O que é o sistema geral de aferentes viscerais (GVA)?

Answer 4

É uma das categorias funcionais das vias que transmite informação sensorial - como pressão, dor, e outras sensações viscerais destas estruturas.

Question 5

Por que tratos é composto o sistema anterolateral (ALS) e quais os principais componentes funcionais?

Answer 5

Inclui os tratos espinotalâmico, espinoreticular, espinomesencefálico, espinotectal e espinohipotalâmico. Transmite predominantemente dor; temperatura; tacto e pressão não discriminativos (fracamente localizado); e alguma proprioceção.

Question 6

Por que tratos é composta a coluna dorso-medial lemniscal (DCML) e quais os principais componentes funcionais?

Answer 6

Inclui os fascículo gracilis, fascículo cuneatus e o lemnisco medial. Trasmite senso de tacto descriminativo (fino), senso vibratório e senso de posição.

Question 7

Por que tratos são compostas as vias somatossensoriais para o cerebelo e quais os principais componentes funcionais?

Answer 7

Inclui o trato espinocerebelar anterior, posterior e rostral; e os tratos cuneocerebelares. Transmite informação propriocetiva primária (mas também alguma dor e pressão).

Question 8

O que é a transdução sensorial?

Answer 8

The stimulus to which a specific receptor responds causes an alteration in the ionic permeability of the nerve endings, generating a receptor potential that results in the formation of action potentials. This transformation of the stimulus into an electrical signal is referred to as sensory transduction.

Question 9

O que são exterocetores?

Answer 9

Exteroceptors are close to the body surface and are specialized to detect sensory information from the external environment (such as visual, olfactory, gustatory, auditory, and tactile stimuli). Receptors in this class are sensitive to touch (light stimulation of the skin surface), pressure (stimulation of receptors in the deep layers of the skin, or deeper parts of the body), temperature, pain, and vibration. Exteroceptors are further classified as teloreceptors (distant stimuli, as light or sound) or contact receptors (contact stimulus),

Question 10

O que são propriocetores?

Answer 10

Proprioceptors transmit sensory information from
muscles, tendons, and joints about the position of a body part, such as a limb in space. There is a static position sense relating to a stationary position and a kinesthetic sense (G. kinesis, “movement”), relating to the movement of a body part. The receptors of the vestibular system located in the inner ear, relaying sensory information about the movement and orientation of the head, are also classified as proprioceptors.

Question 11

O que são interocetores?

Answer 11

Interoceptors detect sensory information concerning the status of the body’s internal environment, such as stretch, blood pressure, pH, oxygen or carbon dioxide concentration, and osmolarity.

Question 12

O que são nocicetores, quais os tipos e função?

Answer 12

Nociceptors are rapidly adapting receptors that are sensitive to noxious or painful stimuli. They are located at the peripheral terminations of lightly myelinated free nerve endings of type Aδ fibers, or unmyelinated type C fibers, transmitting pain. Nociceptors are further classified into:
1) Mechanosensitive nociceptors - (of Aδ fibers), which are sensitive to intense mechanical stimulation (such as
pinching with pliers) or injury to tissues;
2) Temperature-sensitive (thermosensitive) nociceptors - (of Aδ fibers), which are sensitive to intense heat and cold;
3) Polymodal nociceptors - (of C fibers), which are sensitive to noxious stimuli that are mechanical, thermal, or chemical in nature. Although most nociceptors are sensitive to one particular type of painful stimulus, some may respond to two or more types.

Question 13

O que são termorrecetores, quais os tipos e função?

Answer 13

Thermoreceptors are sensitive to warmth or cold. These slowly adapting receptors are further classified into three types:

1) Cold receptors, which consist of free nerve endings of lightly myelinated Aδ fibers.
2) Warmth receptors, which consist of the free nerve endings of unmyelinated C fibers that respond to increases in temperature.
3) Temperature-sensitive nociceptors that are sensitive to excessive heat or cold.

Question 14

O que são mecanorrecetores, quais os tipos e função?

Answer 14

Mechanoreceptors, which comprise both exteroceptors and proprioceptors, are activated following physical deformation due to touch, pressure, stretch, or vibration of the skin, muscles, tendons, ligaments, and joint capsules, in which they reside. A mechanoreceptor may be classified as:

1) Nonencapsulated - are slowly adapting and include free nerve endings and tactile receptors; include free nerve endings, peritrichial nerve endings, Merkel’s corpuscles.
2) Encapsulated - include Meissner’s corpuscles, Pacinian corpuscles, Ruffini’s end organs.

Question 15

Onde estão presentes as terminações nervosas livres? E são estímuladas pelo quê?

Answer 15

Free nerve endings are present in the epidermis, dermis, cornea, dental pulp, mucous membranes of the oral and nasal cavities and of the respiratory, gastrointestinal, and urinary tracts, muscles, tendons, ligaments, joint capsules, and bones. The peripheral nerve terminals of the free nerve endings lack Schwann cells and myelin sheaths. They are stimulated by touch, pressure, thermal, or painful stimuli.

Question 16

Onde e quando são estímuladas as terminações nervosas peritriciais?

Answer 16

Peritrichial nerve endings are large-diameter, myelinated, Aβ fibers that coil around a hair follicle below its associated sebaceous gland. This type of receptor is stimulated only when a hair is being bent.

Question 17

Em que consistem os recetores tácteis (corpusculos de Merkel)?

Answer 17

Tactile receptors consist of disc-shaped, peripheral nerve endings of large-diameter, myelinated, Aβ fibers.
Each disc-shaped terminal is associated with a specialized epithelial cell, the Merkel cell, located in the stratum basale of the epidermis. These receptors, frequently referred to as Merkel’s discs, are present mostly in glabrous (hairless), and occasionally in hairy skin. Merkel’s discs respond to discriminative touch stimuli that facilitate the distinguishing of texture, shape, and edges of objects.

Question 18

Onde estão localizados os corpúsculos de Meissner e em que consistem?

Answer 18

Meissner’s corpuscles are present in the dermal papillae of glabrous skin of the lips, forearm, palm, and sole, as well as in the connective tissue papillae of the tongue. These corpuscles consist of the peripheral terminals of Aβ fibers, which are encapsulated by a peanut-shaped structural device consisting of a stack of concentric Schwann cells surrounded by a connective tissue capsule. They are rapidly adapting and are sensitive to two-point tactile (fine) discrimination, and are thus of great importance to the visually impaired by permitting them to be able to read Braille.

Question 19

Em que consistem os corpúsculos de Pacinian e onde se localizam?

Answer 19

Pacinian corpuscles, the largest of the mechanoreceptors, are rapidly adapting and resemble an onion in cross-section. Each Pacinian corpuscle consists of Aβ-fiber terminals encapsulated by layers of modified fibroblasts that are enclosed in a connective tissue capsule. Pacinian corpuscles are located in the dermis, hypodermis, interosseous membranes, ligaments, external genitalia, joint capsules, and peritoneum, as well as in the pancreas. They are more rapidly adapting than Meissner’s corpuscles and are believed to respond to pressure and vibratory stimuli, including tickling sensations.

Question 20

Onde estão localizados os órgãos terminais de Ruffini e em que consistem?

Answer 20

Ruffini’s end organs (corpuscles of Ruffini) are located in joint capsules, the dermis, and the underlying hypodermis of hairy skin. The unmyelinated peripheral terminals of Aβ myelinated fibers are slowly adapting. They intertwine around the core of collagen fibers, which is surrounded by a lamellated cellular capsule. Ruffini’s end organs respond to stretching of the collagen bundles in the skin or joint capsules and may provide proprioceptive information.