Nervous System - Sense Organs Flashcards
What is a receptor?
Specialised cells that detect stimuli and and convert them into nerve impulses
What is a sense organ?
A concentration of receptors with the same function
Functions of the ear
Hearing and balance
Location of the ear
Pinnae positioned outside the skull on opposite sides of the head, rest of the ear embedded in the temporal bone
Three parts of the ear
Outer ear
Middle ear
Inner ear
Parts which make up the outer ear
Pina
External auditory canal
Structures making up the middle ear
Tympanic membrane (eardrum) Ossicles Oval window Round window Opening to the Eustachian tube
Parts which make up the inner ear
Bony labyrinth (perilymph filled)
Membranous labyrinth
Vestibular apparatus
Cochlea
The vestibular apparatus consists of…
The utriculus and the sacculus
Three semicircular canals
What are maculae?
Special receptors found in the sacculae and utriculae
The function of the maculae
Generate impulses when stimulated by gravity during a change in position of the head
The impulses from the maculae go to…
The cerebellum (which coordinates muscles to restore balance)
What are cristae?
Sensory organs of rotation found in the ampullae of the semi-circular canals
Cristae are stimulated by…
Movement of the endolymph of the semi-circular canals due to movement of the head
Impulses from the cristae go to…
The cerebellum (which coordinates muscles to restore balance)
The type and location of receptors which detect light stimuli
Photoreceptors in the eye
The shape of the eye
Pretty spherical
Purpose of the eyelids and eyelashes
Protect the eye from foreign objects
Describe the conjunctiva
Thin mucous membrane containing pain receptors that are stimulated by dust/other particles and trigger blink reflex
Location of the conjunctiva
Covers the front of the eye and the inner surface of the eyelid
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
6
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
