SENSORY RECEPTORS:
RECEPTORS:
Living organisms use receptors to detect changes in the external environment.
Impulses are conducted along the sensory neurons from the receptors in the
central nervous system.
Motor neurons react to changes and send impulses to the effectors to make a
reaction.
General receptors
- Modified dendrites of sensory neurons.
- And distributed throughout the body.
Special sensory receptors
- Receptor cells found in the head region.
- Complex organs like eyes and ears
- Epithelial structures like taste buds and olfactory epithelium.
Stimulus Location of receptors Receptors Sensations
Light Eye Rods and cones Sight
Sound Cochlear in ear Organ of Corti Hearing
Head movements Vestibular apparatus in Maculae and cristae Maintain balance
ear
- Meisner’s - Touch
corpuscles - Pressure
- Pacinian - Pain
Mechanical Skin corpuscles
- Free nerve
endings
Temperature Skin - Krause’s - Cold
corpuscles - Heat
- Ruffini’s
corpuscles
Chemicals Nose Olfactory cells Smell
Chemicals Tongue Taste cells in papillae Taste
, THE HUMAN EYE:
WHERE IS THE EYE SITUATED:
Eyeballs fit into a body socket situated anteriorly in the cranium.
Held in position by six external muscles. They also control movement of the eyes
Cushioned by posterior fatty tissue
EXTERNAL FEATURES OF THE EYE:
Lachrymal gland:
- Produces salty tears
- Washes away dust
- Keeps conjunctiva moist
Tear duct:
- Drains excess fluid into nasal cavity
Eye lashes and eyelids:
- Protect eye from dust, light and foreign bodies
Glands of Meiboom:
- Secrete oily fluid to lubricate the eyeball.
, INTERNAL STRUCTURE OF THE EYE:
LAYERS OF THE WALL OF THE EYE:
1. Outer fibrous coat.
Parts Structure Functions
Delicate mucous membrane Has pain receptors that cause the
Covers the front of the eye eyes to close to prevent foreign
Conjunctiva and lines the eyelids. bodies from entering.
Produces lubricating mucus to stop
the eyes from drying out
Tough inelastic white layer. Protects internal part of eye.
Made up of connective tissue. Provides point of attachment for 6
Sclera Covers the posterior 5/6 of the extrinsic eye muscles.
eyeball. Inelastic nature helps to maintain
the shape of the eye.
Covers the other 1/6 of the Allows light rays to pass through to
eyeball. the light-sensitive cells.
It is more convex. The conjunctiva has pain receptors
Cornea Transparent and has no blood which enable the eyelids to close
vessels. reflexively when foreign matter
Covered by conjunctiva. touches the surface of the eye.
RECEPTORS:
Living organisms use receptors to detect changes in the external environment.
Impulses are conducted along the sensory neurons from the receptors in the
central nervous system.
Motor neurons react to changes and send impulses to the effectors to make a
reaction.
General receptors
- Modified dendrites of sensory neurons.
- And distributed throughout the body.
Special sensory receptors
- Receptor cells found in the head region.
- Complex organs like eyes and ears
- Epithelial structures like taste buds and olfactory epithelium.
Stimulus Location of receptors Receptors Sensations
Light Eye Rods and cones Sight
Sound Cochlear in ear Organ of Corti Hearing
Head movements Vestibular apparatus in Maculae and cristae Maintain balance
ear
- Meisner’s - Touch
corpuscles - Pressure
- Pacinian - Pain
Mechanical Skin corpuscles
- Free nerve
endings
Temperature Skin - Krause’s - Cold
corpuscles - Heat
- Ruffini’s
corpuscles
Chemicals Nose Olfactory cells Smell
Chemicals Tongue Taste cells in papillae Taste
, THE HUMAN EYE:
WHERE IS THE EYE SITUATED:
Eyeballs fit into a body socket situated anteriorly in the cranium.
Held in position by six external muscles. They also control movement of the eyes
Cushioned by posterior fatty tissue
EXTERNAL FEATURES OF THE EYE:
Lachrymal gland:
- Produces salty tears
- Washes away dust
- Keeps conjunctiva moist
Tear duct:
- Drains excess fluid into nasal cavity
Eye lashes and eyelids:
- Protect eye from dust, light and foreign bodies
Glands of Meiboom:
- Secrete oily fluid to lubricate the eyeball.
, INTERNAL STRUCTURE OF THE EYE:
LAYERS OF THE WALL OF THE EYE:
1. Outer fibrous coat.
Parts Structure Functions
Delicate mucous membrane Has pain receptors that cause the
Covers the front of the eye eyes to close to prevent foreign
Conjunctiva and lines the eyelids. bodies from entering.
Produces lubricating mucus to stop
the eyes from drying out
Tough inelastic white layer. Protects internal part of eye.
Made up of connective tissue. Provides point of attachment for 6
Sclera Covers the posterior 5/6 of the extrinsic eye muscles.
eyeball. Inelastic nature helps to maintain
the shape of the eye.
Covers the other 1/6 of the Allows light rays to pass through to
eyeball. the light-sensitive cells.
It is more convex. The conjunctiva has pain receptors
Cornea Transparent and has no blood which enable the eyelids to close
vessels. reflexively when foreign matter
Covered by conjunctiva. touches the surface of the eye.
