Receptors

Receptors

Receptor is a specialized modified sensory nerve ending which undergoes depolarization in response to a specific stimulus and in turn sends information to the CNS.

It’s function is to act as a transducer to convert various forms of energy into electric energy in Neuron.

Each type of sensation (pain, touch, vibration etc) is called modality of sensation and the specificity of nerve fibre for transmitting only one modality of sensation is called labeled line principle and the impression of stimulus anywhere to brain is called law of projection.

Each receptor is differently sensitive to each sensory stimulus and thus insensitive to other

eg: rods and cones are sensitive to light but not to touch, temperature etc.

CLASSIFICATION OF SENSORY RECEPTORS:

A) Skin Tactile Sensibilities (epidermis & dermis)

I) free nerve ending

II) expanded tip endings – Merkel discs

III) spray endings

IV) ruffini endings

V) encapsulated endings – Meissner & Krause Corpuscle

VI) hair end organs

B) Deep Tissue Sensibilities

I) Free Nerve Endings

II) Expanded Tip Endings

III) Spray Endings : Ruffini Endings

IV) Encapsulated Ending: Pacinian Corpuscle

V) Muscle Endings : Muscle Spindle & Golgi Tendon

C) Hearing : Sound Receptors of Choclea

D) Equilibrium : Vestibular receptors

E) Arterial Pressure : Baroreceptors of Carotid Sinus & Aorta

Pain: Free Nerve Ending

Cold & Warm Receptors

Vision : Rods & Cones

A) Taste : Taste bud receptors

B) Smell : Receptors of Olfactory Epithelium

C) Arterial Oxygen : Receptors of Aortic & Carotid Bodies

D) Osmolality : Neuron in & around supraoptic nuclei

E) Blood CO2 : Receptors of medulla and in aortic and carotid bodies

F) Blood Glucose, amino acids, fatty acids : Hypothalamic receptors

TRANSMISSION OF SIGNALS OF DIFFERENT INTENSITIES

Spatial Summation

Increasing signal strength is transmitted by using greater number of fibres.

Temporal Summation

Increasing signal strength is transmitted by increasing the frequency of nerve impulse per fibre

*Merkel’s Dics & Meissner’s Corpuscle : perception of touch. Rapidly adapting thus clothes not felt.

*Pacinian Corpuscle : sustained touch & perception of pressure. Rapidly adapting thus we do not feel seat pressure when sitting.

*Ruffini’s Ending : sustained pressure.

*Krause’s Ending : Conjunctiva, papillae of lip and tongue, skin of genitalia.

*Naked Nerve Ending : Nociceptors

PROPERTIES OF RECEPTORS   (SLIDE TO VIEW MORE›)

 

—Contributed  by Dharmin Doshi (MIMER Medical College)

 

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