lect. 3, sensory receptors by dr sadia zafar

7/30/2019 LECT. 3, Sensory Receptors by dr sadia zafar

1/27

SensorySensory

ReceptorsReceptors


2/27

Definition of SensoryDefinition of Sensory

ReceptorsReceptors:: ReceptorsReceptors are specialized cells / nerveare specialized cells / nerve

endings which respond to stimuli.endings which respond to stimuli. These generate impulses which informThese generate impulses which inform

CNS about changes in internal & externalCNS about changes in internal & external

environment.environment. ReceptorsReceptors are transducers, which convertare transducers, which convert

various forms of energy into actionvarious forms of energy into actionpotential or electrical energy.potential or electrical energy.

STIMULUSSTIMULUS: A change in environment.: A change in environment. TYPES OF STIMULUSTYPES OF STIMULUS: Electrical,: Electrical,

Mechanical, Thermal, Chemical &Mechanical, Thermal, Chemical &Electromagnetic.Electromagnetic.

Sensation:Sensation: Becoming aware of a particularBecoming aware of a particulart e of stimulus, e. .,t e of stimulus, e. ., tactiletactile,, thermalthermal &&


3/27

Non-encapsulated &Non-encapsulated &

encapsulated receptors:encapsulated receptors:

Non-encapsulated:Non-encapsulated: free nervefree nerve

endings /endings /

nociceptors, Merkels discs, hairnociceptors, Merkels discs, hairfolliclefollicle

receptors.receptors.

Encapsulated:Encapsulated: Meissners corpuscles,Meissners corpuscles,Pacinian corpuscles, Ruffinis endPacinian corpuscles, Ruffinis end

organs, Krauses corpuscles.organs, Krauses corpuscles.


4/27

Non-encapsulated:Non-encapsulated:

FREE NERVE ENDINGSFREE NERVE ENDINGS::

Widely distributed.Widely distributed.

In epidermis, mucus membranes,In epidermis, mucus membranes,joint ligaments, tendons, connectivejoint ligaments, tendons, connective

tissue, periosteum, peritoneum,tissue, periosteum, peritoneum,

pleural membrane, meninges, dentalpleural membrane, meninges, dental

pulp.pulp.

Involved in crude touch, pressure,Involved in crude touch, pressure,

tickle & itch, pain & temperaturetickle & itch, pain & temperature

sensation.sensation.


5/27


MERKELS DISCSMERKELS DISCS::

Present in clusters / groups inPresent in clusters / groups in

epidermisepidermis

(deeper part).(deeper part).

Stimulated when there is continuousStimulated when there is continuous

touch or pressure.touch or pressure. ExampleExample: holding: holdinga pen while writing.a pen while writing.


6/27


HAIR FOLLICLE RECEPTORS:HAIR FOLLICLE RECEPTORS:

Wrapped around hair follicles.Wrapped around hair follicles.

Stimulated by bending of hair (ifStimulated by bending of hair (ifsomething is crawling on skin).something is crawling on skin).


7/27

HAIR FOLLICLE


8/27

Adaptation in non-Adaptation in non-

encapsulated receptors:encapsulated receptors:

Free nerve endings & merkels discsFree nerve endings & merkels discs

slow adaptation.slow adaptation.

We feel the pen as long as we hold it.We feel the pen as long as we hold it.

Hair follicle receptors undergoHair follicle receptors undergo rapidrapid

adaptationadaptation..

Insect starts crawlingInsect starts crawling

we feel itwe feel it

if it does not biteif it does not bite we forget itswe forget its

presence.presence.


9/27

Encapsulated:Encapsulated:

MEISSNERS CORPUSCLES:MEISSNERS CORPUSCLES: Meissner's corpuscles were discovered byMeissner's corpuscles were discovered by

thethe anatomistanatomistGeorg MeissnerGeorg Meissner (1829-(1829-1905).1905).

Rapid adaptation.Rapid adaptation. In dermal capillaries in skin of soul & palmIn dermal capillaries in skin of soul & palm Nipple & external genitalia.Nipple & external genitalia.

Under the capsule are flat modifiedUnder the capsule are flat modifiedschwann cells arranged concenticallyschwann cells arranged concenticallyalong long axis of corpuscles & end inalong long axis of corpuscles & end inexpanded nerve endings.expanded nerve endings.

Involved in: fine touch, 2 point tactileInvolved in: fine touch, 2 point tactile

discrimination & vibration.discrimination & vibration.
http://en.wikipedia.org/wiki/Anatomyhttp://en.wikipedia.org/wiki/Anatomyhttp://en.wikipedia.org/wiki/Georg_Meissnerhttp://en.wikipedia.org/wiki/Georg_Meissnerhttp://en.wikipedia.org/wiki/Georg_Meissnerhttp://en.wikipedia.org/wiki/Anatomy


10/27

MEISSNERS CORPUSCLE IN SKIN
http://upload.wikimedia.org/wikipedia/commons/d/d3/WVSOM_Meissner%27s_corpuslce.JPG


11/27


PACINIAN CORPUSCLE:PACINIAN CORPUSCLE:

Rapid adaptation.Rapid adaptation.

In dermis of skin, C.T, ligaments,In dermis of skin, C.T, ligaments,joint corpuscles, peritoneum etc.joint corpuscles, peritoneum etc.

Thick corpuscles, on sectionThick corpuscles, on section oniononion

like appearance.like appearance. Flattened cells arrangedFlattened cells arranged

concentrically (in layers)concentrically (in layers)

Involved in vibration & movement.Involved in vibration & movement.


12/27

PACINIAN CORPUSCLE


13/27


RUFFINIS END ORGANS:RUFFINIS END ORGANS:

In dermis of skin.In dermis of skin.

Respond when skin is stretched /Respond when skin is stretched /heavy pressure applied on skin.heavy pressure applied on skin.

Slow adaptation.Slow adaptation.


14/27

RUFFINIS END ORGANS


15/27


KRAUSES CORPUSCLES:KRAUSES CORPUSCLES:

In the skin of external genitalia.In the skin of external genitalia.

Respond to 2 point tactileRespond to 2 point tactilediscrimination.discrimination.

Rapid adaptation.Rapid adaptation.

Structure resemblesStructure resembles MeissnersMeissnerscorpuscles.corpuscles.


16/27

KRAUSES END-BULBS / KRAUSES CORPUSCLES


17/27

OTHER CLASSIFICATION OFOTHER CLASSIFICATION OF

RECEPTORS:RECEPTORS:

4 TYPES:4 TYPES:

EXTEROCEPTORS:EXTEROCEPTORS:

INTEROCEPTORSINTEROCEPTORSTELOCEPTORSTELOCEPTORS

PROPRIOCEPTORSPROPRIOCEPTORS


18/27

EXTEROCEPTORS:EXTEROCEPTORS:

In skinIn skin

Respond to external stimuli.Respond to external stimuli.


19/27

INTEROCEPTORS:INTEROCEPTORS:

In body tissues.In body tissues.

Respond to internal stimuli.Respond to internal stimuli.


20/27

TELOCEPTORS:TELOCEPTORS:

Respond to stimuli at a distance.Respond to stimuli at a distance.

EXAMPLE: Receptors in retina: rods &EXAMPLE: Receptors in retina: rods &

cones. Hearing receptors in ears.cones. Hearing receptors in ears.


21/27

PROPRIOCEPTORS:PROPRIOCEPTORS:

Receptors involved in sensation ofReceptors involved in sensation of

position & movement.position & movement.

When a part of body is moved, theyWhen a part of body is moved, they

are stimulated.are stimulated.

Cl ifi ti th b iClassification on the basis


22/27

Classification on the basisClassification on the basis

ofof

nature of stimulus:nature of stimulus: 5 types:5 types: MECHANORECEPTORS.MECHANORECEPTORS.

THERMORECEPTORS.THERMORECEPTORS. NOCICEPTORS.NOCICEPTORS.

CHEMORECEPTORS.CHEMORECEPTORS.

ELECTRO-MAGNETIC RECEPTORS.ELECTRO-MAGNETIC RECEPTORS.


23/27

MECHANORECEPTORS:MECHANORECEPTORS:

Respond to mechanical deformation ofRespond to mechanical deformation of

receptor membrane & of tissue, adjacentreceptor membrane & of tissue, adjacent

to receptor.to receptor.

Large number of receptors are included.Large number of receptors are included. EXAMPLES: Free nerve endings, MerkelsEXAMPLES: Free nerve endings, Merkels

disks, hair follicles, Meissners, Ruffinis,disks, hair follicles, Meissners, Ruffinis,

Krauses corpuscles, muscle spindle, golgiKrauses corpuscles, muscle spindle, golgi

tendon organs, receptors in internal ear: intendon organs, receptors in internal ear: in

organ of corti, in semi-circular canals, inorgan of corti, in semi-circular canals, in

macula & vestibular apparatus.macula & vestibular apparatus.

Baroreceptors are also included.Baroreceptors are also included.


24/27

THERMORECEPTORS:THERMORECEPTORS:

Respond to temperature changes.Respond to temperature changes.

Include cold & warmth receptors.Include cold & warmth receptors.


25/27


26/27

CHEMORECEPTORSCHEMORECEPTORS::

Respond to chemical changes.Respond to chemical changes.

Include chemoreceptors in carotid &Include chemoreceptors in carotid &

aortic bodies, chemosensitive area inaortic bodies, chemosensitive area in

medulla oblongata, olfactorymedulla oblongata, olfactory

receptors, taste receptors,receptors, taste receptors,

osmoreceptors in hypothalamus &osmoreceptors in hypothalamus &

glucostat cells in satiety centre inglucostat cells in satiety centre inhypothalamus.hypothalamus.


27/27

ELECTROMAGNETICELECTROMAGNETIC

RECEPTORSRECEPTORS::

Respond to electromagnetic rays.Respond to electromagnetic rays.

EXAMPLE: Rods & Cones in Retina.EXAMPLE: Rods & Cones in Retina.

lect. 3, sensory receptors by dr sadia zafar

Documents