Somatosensory receptors Flashcards

Question

Merkel’s Receptors (Discs)

Answer 1

Nonencapsulated * Located in the basal cell layer of the epidermis, below glabrous skin of: ▫ Lips ▫ Extremities (distal part) ▫ Genitalia (external) * Low threshold * Slow adapting (SA) * Sensitive to pressure and low- frequency vibration ▫ Signal discrete indentation * Each ending consists of a Merkel cell in close apposition with an enlarged nerve terminal, up to 90, sometimes called as a Merkel cell-neurite complex. * Small receptive fields

Answer 2

A mesh-like arrangement of axons around a hair follicle * Provide information to the brain about discrete tactile stimulation * Rapid and Slow adapting * Sensitive to touch

Answer 3

Accuracy of stimulus depends on: 1. Density of receptors 2. Size of receptive fields SLIDE 30 ver tabla***

Answer 4

Meissner (Adaptive rate: rapid / receptive fiel: small) Pacinian (Adaptive rate: rapid / receptive fiel: large) important for sensing movement of an object across the skin Merkel (Adaptive rate: slow / receptive fiel: small) Ruffini (Adaptive rate: slow / receptive fiel: large Provides input related to displacement and velocity of the stimulus Signaling the pressure and shape of the object through the skin

Answer 5

Distributed throughout the musculoskeletal system * Respond to mechanical forces (position and movement of extremities), within the body itself. * Play an important role in posture and movement * The body’s ability to transmit position sense (from proprioceptors), interpret the information received and respond * Afferent nerves that receive and send information from skin, tendons, joints and muscles to the CNS

Answer 6

Types of Proprioception: ▫ Consciously ▫ Unconsciously Modalities: ▫ Limb position sense ▫ Kinesthesia joint position direction velocity of joint movements Proprioceptors provide sensory information to the cerebral cortex: Muscles and tendons have receptors that detect: Muscle length = muscle spindles Muscle strength = Golgi tendon organs Muscle pain is detected by free nerve endings Proprioceptors in the joints detect information regarding its position

Answer 7

Joint Receptors & Ligaments * Free nerve endings * Encapsulated receptors ▫ Low-threshold mechanoreceptors ▫ Rapid adapting Provide information regarding the dynamic aspect of kinesthesia Movement, direction and velocity of its movement ▫ Slowly adapting Provide information about static aspect of kinesthesia Position judgment

Answer 8

Muscle spindle Detect changes in muscle length * Present in skeletal muscles ▫ Extrafusal fibers Innervated by alpha motor neurons Each spindle consist of a connective tissue capsule containing 8 to 10 intrafusal fibers, which are parallel to extrafusal fibers. ▫ Innervated by spinal gamma motor neurons

Answer 9

Nuclear chain fiber § Single row of central nuclei § Smaller and shorter than the nuclear bag fiber Nuclear bag fiber § Cluster of nuclei located in a bag-like dilation at the center of the fiber § Larges intrafusal fiber

Answer 10

1. Annulospiral endings (primary afferents; type Ia sensory endings) § Innervate the middle portion of both nuclear chain and bag fibers 2. Flower-spray endings (secondary afferents) § Located at the end of the nuclear bag fiber Muscles spindles detect changes in muscle length. Efferent axons of gamma motor neurons (ventral horn of spinal cord) innervate the polar end.

Answer 11

Efferent axons of gamma (ɣ) motor neurons (ventral horn of spinal cord) innervate the polar end, causing intrafusal fibers to contract and remain responsive.

Answer 12

Varies among different muscles. Those muscles that requires precise movements, such as the extraocular muscles, have higher density of muscle spindles than muscles responsible for gross movements.

Answer 13

intrafusal fiber --> (a-Alpha) motor neuron --> reflex-induced contraction of extrafusal fiber

Answer 14

Located at the tendon-muscle junction * Slowly adapting mechanoreceptor that are stimulated by tension in thew tendon * High-threshold * Arranged in series with the extrafusal fibers, consisting of a mesh-like weave of collagenous bundles within a thin capsule * Sensory neuron conduct impulses to spinal cord * Innervated by type Ib afferent fibers * Senses changes in tendon tension/force

Answer 15

Within and around capsule joints-->Nerve endings-->Pain information Connective tissue external to the capsule-->Ruffini endings Pacinian--->Respond to start and stop of movement & Position of the joint

Answer 16

Found in cutaneous as well as in deep structures Mechanical-->Aδ afferents (thinly myelinated)-->Sharp, pricking-->fast and acute pain sensations Thermal and Mechano-thermal-->Aδ afferents (thinly myelinated)-->Slow burning, cold sharp, pricking-->Fast and acute pain sensations Polymodal-->Unmyelinated (C)-->Hot, burning sensation, cold, mechanical stimuli-->Tissue damage Slow, chronic pain sensation ptt foto

Somatosensory receptors Flashcards

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