Nervous System - Sense Organs Flashcards by Sankara Benson Gyuse Atsilut

What is a receptor?

Specialised cells that detect stimuli and and convert them into nerve impulses

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What is a sense organ?

A concentration of receptors with the same function

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Functions of the ear

Hearing and balance

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Location of the ear

Pinnae positioned outside the skull on opposite sides of the head, rest of the ear embedded in the temporal bone

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Three parts of the ear

Outer ear
Middle ear
Inner ear

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Parts which make up the outer ear

Pina

External auditory canal

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Structures making up the middle ear

Tympanic membrane (eardrum)
Ossicles
Oval window
Round window
Opening to the Eustachian tube

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Parts which make up the inner ear

Bony labyrinth (perilymph filled)
Membranous labyrinth
Vestibular apparatus
Cochlea

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The vestibular apparatus consists of…

The utriculus and the sacculus

Three semicircular canals

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What are maculae?

Special receptors found in the sacculae and utriculae

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The function of the maculae

Generate impulses when stimulated by gravity during a change in position of the head

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The impulses from the maculae go to…

The cerebellum (which coordinates muscles to restore balance)

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What are cristae?

Sensory organs of rotation found in the ampullae of the semi-circular canals

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Cristae are stimulated by…

Movement of the endolymph of the semi-circular canals due to movement of the head

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Impulses from the cristae go to…

The cerebellum (which coordinates muscles to restore balance)

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The type and location of receptors which detect light stimuli

Photoreceptors in the eye

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The shape of the eye

Pretty spherical

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Purpose of the eyelids and eyelashes

Protect the eye from foreign objects

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Describe the conjunctiva

Thin mucous membrane containing pain receptors that are stimulated by dust/other particles and trigger blink reflex

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Location of the conjunctiva

Covers the front of the eye and the inner surface of the eyelid

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Position and function of the tear gland

Above the eyeball secretes antiseptic tears that protect the conjunctiva from bacteria and dehydration

The eye has how many muscles for movement

Three layers of the internal structure of the eye

Outer fibrous layer
Middle vascular layer
Inner light-sensitive retina

The outer fibrous layer consists of the…

Sclera

Cornea

Structure of the sclera

Strong, white, inelastic layer of connective tissue forming the outer layer of the eyeball and extending to the cornea at the front

Function of the sclera

Protects internal parts of the eye Helps maintain spherical shape Serves for muscle attachment

Structure of the cornea

Transparent front part of the sclera, which is more convex than the rest of the eyeball

Function of the cornea

Allows light rays through to the inner layers of the eye | Causes refraction of incoming light

The middle vascular layer consists of the...

Choroid Ciliary body Iris Lens

Structure of the choroid

Thin, darkly pigmented vascular layer

Function of the choroid

Pigment absorbs excess light which prevents internal reflection and blurred images Blood vessels supply oxygen and nutrients to cells

Structure of he ciliary body

Thickening of the front part of the choroid, consisting of ciliary muscles Connected to the lens by suspensory ligaments

Function of the ciliary body

Contracts and relaxes to control the curvature of the lens during accommodation

Structure of the iris

Round, coloured continuation of the choroid situated in front of the lens Has an opening in the middle, the pupil

Function of the iris

Regulates the amount of light that enters the eye by controlling the size of the pupil with radial and circular muscles

Structure of the lens

Rubbery, elastic, transparent, biconvex structure that can change shape Kept in position by suspensory ligaments attached to the ciliary body

Function of the lens

Changes shape to refract light rays from near and far objects to form a clear image on the retina

The inner light-sensitive retina consists of the...

Pigment layer | Nervous tissue layer

Structure and function of the pigment layer

Outer layer that is in contact with the choroid | Absorbs light rays and prevents internal reflection

Two types of photoreceptors that make up the nervous tissue layer

Rods and cones

Function of rods and cones

``` Detect and convert light stimuli into nerve impulses Rods: Stimulated in low light intensity Black and white vision Cones: Stimulated in high light intensity Colour vision ```

Name the area of the retina that contains mostly cones and very few rods

The yellow spot

Function of the yellow spot

Clearest, most accurate image is formed here

Function of the optic nerve

Conducts nerve impulses to the cerebral cortex where they are interpreted

The two internal cavities of the eye divided by the lens

Anterior cavity in front of the lens | Posterior cavity behind the lens

Contents and parts of the anterior cavity

Filled with a fluid - aqueous humour | Divided into anterior chamber (between cornea and iris) and posterior chamber (between iris and lens)

What fills the posterior cavity?

The vitreous humour

Function of the vitreous humour

Maintains shape of the eyeball Holds retina in place against choroid Refracts light rays to form a sharp image

The automatic reflex action to the amount of light that enters the eye

Pupillary mechanism | Or pupil reflex

Which parts of the eye refract light entering the eye?

The cornea, aqueous humour, lens and vitreous humour

What is accommodation?

Process during which the eye adapts for the observation of objects at different distances

The ability to see in 3D (depth of field)

Stereoscopic vision