sensation, ear, eye

Sensation

Activation of sensory receptor cells by a stimulus

Perception

Central processing and interpretation of sensory stimuli into meaningful patterns

Difference between sensation and perception

Sensation is receptor activation while perception is CNS interpretation of stimuli

General senses

Senses distributed throughout the body with receptors in many organs and tissues

Special senses

Senses associated with specialised organs such as eye, ear, tongue and nose

Examples of general senses

Touch, pressure, pain, temperature, proprioception and visceral sensation

Examples of special senses

Vision, hearing, balance, taste and smell

Somatosensation

Group of sensory modalities associated with touch, proprioception and interoception

Proprioception is:

the sense of the position and movement of your body parts.

eg where ur limb is

Interoception is:

sensing what is happening inside the body.

eg hunger

Somatosensory modalities

the different types of body sensations that the somatosensory system can detect.

Pressure, vibration, light touch, tickle, itch, temperature, pain, proprioception and kinesthesia

Location of somatosensory receptors

Skin, muscles, tendons, ligaments, joint capsules and walls of visceral organs

Proprioception

Sense of body position

Kinesthesia

Sense of body movement

Interoception

Sense of internal organ condition and movement

Sensory receptor

Cell or structure that detects stimuli and converts them into nervous system signals

Chemoreceptor

Receptor that detects chemical stimuli such as taste and smell

Thermoreceptor

Receptor sensitive to temperature changes

Photoreceptor

Receptor in the eye responding to light, colour and movement

Mechanoreceptor

Receptor responding to physical stimuli such as pressure, vibration and stretch

Baroreceptor

Receptor detecting pressure changes within vessels and organs

Nociceptor

Receptor stimulating pain responses from damaging stimuli

Nociception

Pain perception caused by potentially damaging mechanical, chemical or thermal stimuli

Cause of nociceptor activation

Stressed or damaged tissues release chemicals activating nociceptors

Temperature receptors

Receptors sensitive to heat or cold stimuli

Taste (gustation)

Special sense associated with chemical detection by the tongue

Smell (olfaction)

Special sense responsive to airborne chemical stimuli

Papillae

Raised bumps on tongue containing taste buds

Taste buds

Structures containing gustatory receptor cells

Gustatory receptor cells

Specialised chemoreceptors detecting chemicals in food

Function of gustatory receptor cells

Release neurotransmitters based on chemicals detected in food

Cranial nerves involved in taste

Facial nerve 7 and vagus nerve 10

Olfactory epithelium

Specialised sensory epithelium in superior nasal cavity containing olfactory neurons

Location of olfactory epithelium

Superior nasal cavity

Olfactory receptor neurons

Bipolar sensory neurons detecting smell stimuli

Pathway of olfactory neurons

Axons pass through cranial cavity floor to reach brain

Brain regions receiving olfactory input

Primary olfactory cortex (Located in the inferior temporal lobe), limbic system and hypothalamus

Unique feature of smell pathway

Only sensory modality that does not synapse in thalamus before cerebral cortex

Most sensory pathways follow this pattern:

Receptor→Thalamus→Cerebral cortex

The Olfaction pathway is unique because:

smell information reaches the cerebral cortex BEFORE going to the thalamus.

Smell pathway Olfactory receptors→Olfactory bulb→Olfactory cortex

Reason smells trigger memories

Olfactory system has close connections with limbic system and hypothalamus

Audition

Hearing; transduction of sound waves into neural signals

Equilibrium

Sense of balance and body position

Major divisions of ear

External ear, middle ear and inner ear

Function of external ear

Funnels sound waves toward tympanic membrane

Auricle/Pinna

Large elastic cartilage structure directing sound waves

External auditory canal (external acoustic meatus)

Approximately 2.5 cm canal directing sound to tympanic membrane

Tympanic membrane

a thin membrane that vibrates when struck by sound waves.

the eardrum

Middle ear

Air-filled cavity containing auditory ossicles

Auditory ossicles

Malleus, incus and stapes

Malleus

Ossicle attached to tympanic membrane

Incus

Ossicle between malleus and stapes

Stapes

Ossicle attached to oval window of inner ear

Function of auditory ossicles

Amplify and transmit sound vibrations to inner ear

Eustachian tube (pharyngotympanic tube)/auditory tube

Tube connecting middle ear to pharynx to equalise air pressure across tympanic membrane

Function of Eustachian tube

Equalises pressure across tympanic membrane

Inner ear

Contains cochlea and vestibule for hearing and balance

Cochlea

Spiral-shaped structure containing receptors for hearing

Vestibule

Inner ear chamber containing receptors for balance

Oval window

Location where stapes attaches to inner ear

Hair cells with stereocilia

Mechanoreceptors in vestibule detecting head movement and balance

Vestibulocochlear nerve

Cranial nerve transmitting hearing and balance information to brain

Structures responsible for hearing

Cochlea and auditory pathway

Structures responsible for balance

Vestibule and vestibular apparatus

Vision

Special sense of sight based on photoreceptors responding to light

Location of eyes

Within the bony orbits of skull

Function of bony orbit

Protects eyeball and anchors soft tissues

Eyelids

Protect eye from abrasions and foreign particles

Conjunctiva

Membrane connecting eyelids to sclera

Lacrimal gland

Gland producing tears

located above eye

Lacrimal ducts

Drain tears across eye surface

in corner of eye

Function of tears

Wash away foreign particles and lubricate eye

Extraocular muscles

Six skeletal muscles controlling eye movement

Anterior cavity of eye

Space between cornea and lens filled with aqueous humour

Posterior cavity of eye

Space posterior to lens filled with vitreous humour

Aqueous humour

Watery fluid filling anterior cavity of eye

Vitreous humour

Gel-like substance filling posterior cavity of eye

made by cells in retina

Three tunics of eye

Fibrous tunic, vascular tunic and neural tunic

Fibrous tunic

Outermost layer consisting of sclera and cornea

Sclera

White dense connective tissue forming most of eye surface

Cornea

Transparent fibrous coat allowing light into eye and helping focus light

Vascular tunic

Middle layer consisting of choroid, ciliary body and iris, pupil, lens

Choroid

Highly vascular connective tissue supplying blood to eye

deep to sclera

Ciliary body

Muscular structure attached to lens via suspensory ligaments

produces aquous humour. located anterior half of eye

Function of ciliary body

Changes lens shape for near and distant vision

Suspensory ligaments (zonule fibres)

Fibres attaching lens to ciliary body

Lens

Transparent elastic structure focusing light onto retina whcih are

posterior half of eye

Iris

Coloured smooth muscle regulating light entry

Pupil

Hole in centre of iris allowing light into eye

Response of iris to bright light

Constriction of pupil

Response of iris to dim light

Dilation of pupil

Neural tunic (retina)

Innermost layer containing photoreceptors and neurons

Function of retina

Receives and processes visual information

highly vascular

Optic disc

Point where optic nerve leaves eye

blind spot of eye

Blind spot

Area lacking photoreceptors at optic disc

Cause of blind spot

Optic nerve exits retina where no photoreceptors are present

Photoreceptors

Cells in retina responding to light stimuli

Optic nerve

Carries visual information from retina to brain

Fovea centralis

Region of retina associated with sharp vision

Structures responsible for vision

Eye, retina, optic nerve and visual pathways

Special sense organs

Eye, ear, tongue and nose

Main receptor type for vision

Photoreceptors

Main receptor type for hearing

Mechanoreceptors

Main receptor type for balance

Mechanoreceptors