The special senses and integrative functions of the nervous system
The Anatomy of Sensory Organs
Ears
Skin
Nose
Eyes
Tongue
Macula
The area in the retina that contains special light-sensitive cells that allow us to see fine details clearly in the center of our visual field.
Optic Nerve
A bundle of more than a million nerve fibers carrying visual messages from the retina to the brain.
External nostrils: Two chambers divided by the septum.
Septum: Made up mainly of cartilage and bone and covered by mucous membranes. The cartilage also gives shape and support to the outer part of the nose
Nasal passages: Passages that are lined with mucous membranes and tiny hairs (cilia) that help to filter the air.
External meatus. Triangular-shaped projection in the center of the face.
Pupil
The dark center opening in the middle of the iris.
Fovea
The center of the macula which provides the sharp vision.
Retina
The nerve layer lining the back of the eye.
Cornea
The clear front window of the eye which transmits and focuses
Sclera
The white outer coat of the eye, surrounding the iris.
Ciliary Body:
Structure containing muscle and is located behind the iris, which focuses the lens
Choroid
Layer containing blood vessels that lines the back of the eye and is located between the retina
Vitreous Humor
The, clear, gelatinous substance filling the central cavity of the eye.
Iris
The colored part of the eye which helps regulate the amount of light entering the eye
Lens
Focuses light rays onto the retina.
Sinuses: Four pairs of air-filled cavities, also lined with mucous membranes.
Middle Part
Inner Part
Outer part
External auditory canal or tube. This is the tube that connects the outer ear to the inside or middle ear.
Pinna or auricle. This is the outside part of the ear.
Tympanic membrane (eardrum). The tympanic membrane divides the external ear from the middle ear.
Ossicles. Three small bones that are connected and transmit the sound waves to the inner ear.
Eustachian tube. A canal that links the middle ear with the back of the nose. Helps to equalize the pressure in the middle ear.
Cochlea. This contains the nerves for hearing.
Vestibule. This contains receptors for balance.
Semicircular canals. This contains receptors for balance.
Malleus
Incus
Stapes
Dermis
Hypodermis
Epidermis
The body
The root
The tip
The frenulum
Major function of Nervous System
Integration: Requires processing and interpreting sensory data and deciding what actions should be taken.
Response: Comprises learning to respond to stimuli in the external world.
Sensation: The perception and acceptance of information about the external world and events.
Type of Sensory Receptors
Mechanoreceptors
These sensors detect mechanical forces such as vibration, pressure, and contact.
Photoreceptors
Detect light and contribute to the sensation of vision.
Thermoreceptors
Contribute to the perception of temperature by detecting temperature variations.
The nociceptors
React to chemicals produced by damaged tissue to detect signals from damaged tissue or the threat of injury.
The chemosensors
Taste and detect chemicals and react with internal changes.
Proprioreceptors
Sensory receptors that can detect alterations in body movement and posture.
The Sequence of Events in a Simple Sensory Receptor-motor Response Pathway
Integration
The proper reaction is generated by the brain's integration of the sensory input with other sensory data and cognitive processes.
Physical Reaction
The brain sends a signal down the spinal cord to activate a skeletal muscle in order to begin a motor response. The motor pathway consists of two types of neurones: upper motor neurones and lower motor neurones. The cell body of a lower motor neurone is found in the spinal cord's grey matter, and it makes a synapse with a muscle fibre at the neuromuscular junction.
Sensation
When a stimulus, like a change in pressure or temperature, is detected by a sense receptor, the receptor generates an electrical signal that is carried by the sensory axon of a neurone to the spinal cord.
Contraction of Muscles
The motor neurone secretes acetylcholine, which binds to receptors on the muscle fibre and triggers the muscle to contract.
THE MAJOR MODALITIES OF SOMATOSENSORY INFORMATION, AND THE CORRESPONDING PATHWAYS
Proprioception
Temperature
Touch
Nociception
BODY REGIONS AND CATEGORIES (Processed by Somatosensory System)
Proprioception
Enteroceptive
The Exteroceptive Perception of Stimuli Beyond the Bodily World.
THE STRUCTURES RESPONSIBLE
FOR THE SPECIAL SENSES OF TASTE,
SMELL, HEARING, BALANCE, AND VISION
The cochlea, located within the inner ear, plays a crucial role in the conversion of sound waves into electrical impulses. These signals are then sent to the brain by the auditory nerve.
The concept of balance is a fundamental aspect that is often discussed and analysed in various academic disciplines
The perception of auditory stimuli in the form of a ringing sound. The ear is divided into three parts: the outer ear, the middle ear, and the inner ear.
The vestibular system, located inside the inner ear, is responsible for the detection and monitoring of alterations in head position and movement, hence playing a crucial role in the maintenance of balance.
The olfactory receptor neurones are situated in a limited area within the upper nasal cavity.
The concept of vision refers to the ability of an individual to perceive and interpret visual stimuli.
The tongue harbours, taste receptors, referred to as taste cells, which are organised into clusters and situated on papillae.
The eye is composed of three distinct layers: the outside fibrous layer, the middle blood vessel layer, and the inner nerve layer. The retina, situated as the innermost layer of the eye, contains photoreceptor cells responsible for the conversion of light into electrical impulses. These impulses are then sent to the brain by the optic nerve.
HOW DIFFERENT TASTES ARE TRANSDUCED
SWEET: Artificial sweeteners like saccharin, aspartame, and sucralose are used to mimic the taste of sugar.
SOUR
BITTER
A number of drugs, including quinine, morphine, and caffeine, have bitter aftertastes. Avoiding potentially dangerous chemicals by spitting out food when it tastes bad is a good idea.
SALT
Common dietary sources of Na+ include NaCl, or table salt. The H+ ions that are released by acids give food a sour taste.
SAVOURY
Amino acids, especially glutamate, in the diet are to blame. This is the rationale behind the widespread usage of monosodium glutamate (MSG) as a flavour enhancer in food.
The hydrogen ions (H+) released by acids give food a sour tast
As a result of their high citric acid content, lemons taste rather sour.
MECHANORECEPTION FOR HEARING AND BALANCE
The balancing and hearing receptors found in the inner ear.
The outer ear's job is to gather and channel sound waves into the inner ear.
The oval window receives sound vibrations from the middle ear.