PRINCIPLE SENSORY SYSTEM

GROUP 1AYESHA MEHBOOB

SUNDAS GILLMARYAM YAQUB

FIZZA RAJASUMERA MALIK

What is a Sensory System?

O Window to physical energies. Give rise to sensory perceptions.

O General plan of sensory pathways: receptor, thalamus (diencephalon), cortex (telencephalon).

Different sensory systems

O VisionO AuditionO SomatosensoryO TasteO Smell

Why do we have different SYSTEMSwhen the neural activity is the same :

action potential

O Theory of specific sensory energies by Johannes Muller, 1826. Labeled pathways. 

Vision Introduction and structure of an

eye by

Ayesha MehboobFunction of human eye

By Sundas Saba Gill

INTRODUCTION

THE EYEO The eye is a complex sensory organ

consisting of various muscles, tissues, and nerve sensors, which work together to create the phenomenon we know as vision:

The ability to seeO Complex eyes can distinguish shapes

and colors.

TYPES OF EYEEye types can be categorized into 1. Simple eyes: with one concave

photoreceptive surface, and 2. Compound eyes: which comprise

a number of individual lenses laid out on a convex surface

O Any eye type can be adapted for almost any behavior or environment.

O The only limitations specific to eye types are that of resolution e.g.

The  compound eyes achieving a resolution better than 1°. Also, superposition eyes can achieve greater sensitivity and apposition eyes are better suited to dark-dwelling creature

HUMAN EYES

O Human eye is an organ which reacts to light for several purposes.

O As a conscious sense organ, the  eye allows vision.

O Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth.

O The human eye can distinguish about 10 million colors.

O light signals affect adjustment of the size of the pupil.

STRUCTURE OF AN EYE

OUTER STRUCTURE

INNER STRUCTURE

Anatomy of eyeO Sclera: The white portion of the eye,

which is a dense tissue containing blood vessels and providing a surface for attaching the external muscles of the eye.

O Pupil: The round, black opening in the center of the iris that allows light to pass through the eye and onto the retina.

O Iris: The colored part of the outer eye. This thin muscle constricts or dilates to adjust the diameter of the pupil, thus controlling the amount of light that enters the eye.

O Cornea: The transparent tissue that covers the front of the eye including the pupil and iris.

O responsible for most of the eye’s focusing abilities.

 Aqueous humor : A liquid substance found in the eye chambers, made mostly of water.O  delivers vital nutrients to the eyes O maintain correct pressure balance in

the eye chamberO Help in maintain its shape

O  Ciliary muscle: is a muscle in an area of the eye which helps people focus.

O It assist the lens of the eye to be flattened or rounded to allow people to focus on distant and near objects and maintain the proper fluid pressure in the eye.

O Lens: After light enters through the pupil, it passes through the lens, which focuses the light and projects it onto the surface of the retina in the back of the eye.

O vitreous humor: helps keep the retina in place.

O transparent jelly-like mass located behind the lens.

O helps to maintain the shape of the posterior chamber of the eyeball.

O Retina: A light sensitive tissue that lines the inner surface of the back of the eye.

O It transforms light that enters through the pupil and passes through the lens into nerve signals that are converted into an image by the visual cortex of the brain

VISUAL FIELDO All of these components function

simultaneously to allow us to see our surroundings.

O The resulting picture, called the visual field:

Combination of two primary types of vision with distinct functions and characteristics

TYPES OF VISIONS

1. FOVEAL VISION (smallest portion of our visual field)

O Objects within the scope of foveal vision are clear and colorful.

2. PERIPHERAL VISION(The majority of the scene we see)O to detect movements and color and

shape contrasts.

TYPES OF LIGHT RECPTORS

O These two different types of vision are a result of the two kinds of light receptor cells found in the retina.

1. Cones: Foveal vision is created by cone cells.

O that are tightly packed in a small area in the center of the retina.

O only account for 6% of the total retinal light receptors.

O Cone cells require the most light for creating a clear, detailed image.

2. Rods: The rod cells account for the other 94% of light receptors in the retina.O They require less light.O create the blurry, less colorful

qualities of peripheral vision.

BINOCULAR & MONOCULAR VISION

O The visual fields of many organisms like human , involve large areas of binocular vision to improve depth perception.(3 dimension)

O vision using two eyes,O In other organisms, eyes are located

so as to maximize the field of view, such as in rabbits and horses, which have monocular vision.

PROCESS OF VISION

SUNDAS SABA GILL

ANATOMICAL PROCESS OF VISION

1. The eye is a complex optical system which collects light from the surrounding environment,

2. regulates its intensity through a diaphragm,

3. focuses it through an adjustable assembly of lenses to form an image,

4. converts this image into a set of electrical signals

5. and transmits these signals to the brain through complex neural pathways that connect the eye via the optic nerve to the visual cortex and other areas of the brain.

In simple words:O clear image of the visual world

produce on a sheet of photoreceptors called the retina, which is part of the central nervous system but located at the back of the eye.

O Photoreceptors gather visual information and sending electrical signals to other retinal neurons for initial processing

O The signals are then sent via the optic nerve to other parts of brain, which ultimately processes the image and allows us to see.

O The image on the retina is reversed:Objects to the right of center project images to the left part of the retina and vice versa.