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Conscious and subconscious awareness of changes in the external or internal environment.

Components of sensation: Stimulation of the sensory receptor → transduction of the stimulus → generation of nerve impulses → integration of sensory input.

General senses: somatic and visceral. Somatic- tactile, thermal, pain and

proprioceptive sensations. Visceral- provide information about

conditions within internal organs. Special senses- smell, taste, vision, hearing

and equilibrium or balance.

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Free nerve endings: pain and thermoreceptors.

Encapsulated nerve endings: pacinian corpuscles.

Separate cells: hair cells, photoreceptors and gustatory receptor cells.

Generator potential is produced by free nerve endings, encapsulated nerve endings, and olfactory receptors. When it reaches a threshold, it triggers one or more nerve impulses in the axon of a first-order sensory neuron.

Receptor potential triggers the release of neurotransmitter → postsynaptic potential → action potential.

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Exteroceptors Interoceptors Proprioceptors

Mechanoreceptors Thermoreceptors Nociceptors Photoreceptors Chemoreceptors Osmoreceptors

Rapidly adapting receptors: receptors that detect pressure, touch and smell.

Slowly adapting receptors: receptors that detect pain, body position, and chemical composition of the blood.

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Sensory receptors in the skin (cutaneous sensations), muscles, tendons and joints and in the inner ear.

Uneven distribution of receptors. Four modalities: tactile, thermal, pain and

proprioceptive.

Include touch, pressure, vibration, itch and tickle.

Tactile receptors in the skin are Meissner corpuscles, hair root plexuses, Merkel discs, Ruffini corpuscles, pacinian corpuscles, and free nerve endings.

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Egg-shaped mass of dendrites enclosed by a capsule of connective tissue.

Rapidly adapting receptors. Found in the dermal papillae of hairless skin

such as in the fingertips, hands, eyelids, tip of the tongue, lips, nipples, soles, clitoris, and tip of the penis.

Rapidly adapting touch receptors found in the hairy skin.

Free nerve endings wrapped around hair follicles.

Detect movements on the skin surface that disturb hairs.

Also known as type I cutaneous mechanoreceptors.

Slowly adapting touch receptors. Saucer-shaped, flattened free nerve endings. Found in the fingertips, hands, lips, and

external genitalia.

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Also called as type II cutaneous mechanoreceptors.

Elongated, encapsulated receptors. Located deep in the dermis and in ligaments

and tendons. Found in the hands, and soles.

Large oval structure composed of a multilayered connective tissue capsule that encloses a dendrite.

Fast adapting receptors. Found around joints, tendons, and muscles;

in the periosteum, mammary glands, external genitalia, pancreas and urinary bladder.

Thermoreceptors are free nerve endings. Two distinct thermal sensations: cold receptors- warm receptors-

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Protective. Sensory receptors are nociceptors. Free nerve endings. Two types of pain: fast and slow. Fast pain: acute, sharp or pricking pain. Slow pain: chronic, burning, aching or

throbbing pain.

Pain is felt in or just deep to the skin that overlies the stimulated organ or in a surface area far from the stimulated organ.

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Receptors are called proprioceptors. Slow adaptation. Weight discrimination. Three types: muscle spindles, tendon organs

and joint kinesthetic receptors.

Interspersed among most skeletal muscle fibers and aligned parallel to them.

Measure muscle stretching. Consists of intrafusal muscle fibers-

specialized muscle fibers with sensory nerve endings and motor neurons called gamma motor neurons.

Extrafusal muscle fibers- surrounding muscle fibers supplied by alpha motor neurons.

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Located at the junction of a tendon and a muscle.

Protect tendons and their associated muscles from damage due to excessive tension.

Consists of a thin capsule of connective tissue that encloses a few tendon fascicles.

Found within or around the articular capsules of synovial joints.

Free nerve endings and Ruffini corpuscles in the capsules of joints respond to pressure.

Pacinian corpuscles respond to acceleration and deceleration of joints during movement.