SENCESES

Question 1

SPECIAL SENCES

Answer 1

• taste
• sight
• smell
• hearing and balance
• touch

Question 2

SIGHT - THE EYE

Answer 2

• sits in the orbital cavity in the skull adipose tissue = protection
• functions as a coordinated pair
• vision in one eye = possible but could lead to a dimentional perception (speed & distance)

Question 3

ANATOMY OF THE EYE

Answer 3

almost spherical
- blood supply via the retinal artery & vein
- nerve supply - optic nerve
three chambers:
largest chamber - contains the fluid vitreous humour
> 99% water
> mineral salts
> mucoprotein
- keeps pressure to stop collapse and support internal structures

Question 4

ANATOMY OF THE EYE

Answer 4

posterior chamber - between the lens and the iris
anterior chamber - between the iris and the cornea
contains watery fluids - aqueous humour

• secreted by epithelial cells
• into the posterior chamber
• circulates through to the anterior chamber & drains into the venous system via the scleral venous sinus
• Aqueous Humour – nourished contents of the anterior chamber.
• Secretion and drainage are equal to maintain intraocular pressure – rising pressure causes glaucoma

Question 5

SCLEAR AND CORNEA - WHITE OF THE EYE

Answer 5

• fibrous membrane
• maintain shape
• eye muscles attached
• cornea - adapted sclera at anterior of eye
  > allowing light through
  > working with lenes to refract light into the retina

Question 6

CHOROID

Answer 6

• rich blood vessels
• supplies the retina
• absorbs light after retinal processing
• absorbs light once it stimulated receptors in retina (preventing scattering if light through the eye)

Question 7

CILLARY BODY

Answer 7

• Ciliary muscle
• secretory epithelial cells
• the lens is attached to the ciliary body by the suspensory ligament
• can change in size & thickness of lens (to help with close vision)
• under the influence of parasympathetic of oculomoter nerve

Question 8

THE IRIS

Answer 8

• viable coloured part of the eye (pigmented cells)
• lies posterior to cornea but in the ciliary lens
• 2 layers of smooth muscle
• centre: pupil
  parasympathetic nervous system - contracts the pupil constricts

sympathetic nervous system - pupil dilates

• eye pigment blocks excessive light in bright conditions (blue and green eyes have less protection) = higher risk of UV damage
• colour eye is genetic
• smooth muscles change the diamter of the pupil conditions

Question 9

LENS

Answer 9

• ciruclar biconvex
• highly elastic
• fibre enclosed in the capsule
• refractws light to focus on retina
• thickness controlled by cailiary muscles and suspensory ligaments

Question 10

RETINA

Answer 10

• inner lining of the eye
• several layers of nerve cells
• pigmented epiithelial
• light sensative rods & cone receptors = light rays into nerve impulses

RODS (sensative to light)
CONES (sensative to colour)

• all fibres of nerve cells go.at the back of retina to form the optic nerve
• transits impulse to brain

Question 11

CONE CELLS

Answer 11

NERVE CELLS: sensitive to light & colour
- needs bright light
- Sharpe’s clear vision
- concentrated in the macula lutea: Macula Lutea – area of the retina where light rays from the direct field of vision are focussed.
Objects being directly observed are seen in detail, brightly coloured and in sharp focus.

Question 12

ROD CELLS

Answer 12

• nerve cells more light sensitive
• stimulated in low light conditions
• monochromic (black and white)
• 16 times more rods than cones
  Located more in the periphery of the
  retina
• low lighting conditions see more black and white

Question 13

RHODIOPSINS

Answer 13

• light-sensitive pigment found in rods & cones
• Rhodopsin molecules = broken down (bleached) during absorbing light = generating action poteintal
• rods - 1 wavelength = monochromatic vision
  cones - 3 wavelengths (red, blue & green colour vision)
  rhodopsons need time to generate = affected visison

Question 14

DARK ADAPTION

Answer 14

BRIGHT LIGHT:
-Rhodopsin is totally degraded - cones take over and give clear vision

LOW LIGHT:
- Insufficent light = stmulate cone
- delay whilst the rhodospins are generated after being degraded by bright light
- camaera flash = immedite bleaching of rhodopsins in cones & rodes = temp blindness
colour blindness: caused by abnormal rhodospins in one/more cones

Question 15

OPTIC NERVE

Answer 15

• Transmits nerve impulses from the retina to the brain
• The optic nerve has several nerve fibres which cross at the optic chiasma to supply the opposite side of the brain
• Both hemispheres of the brain receive input from both eyes

Question 16

PHYSIOLOGY OF SIGHT

Answer 16

• Pupils control the amount of light entering the eye
• convergence - extrinsic muscles to converge on the object
  Changes to the shape of the lens
  near objects (thicker)
  Distant objects (thinner)

Convergence doesn’t happen when two separate images are sent to the brain, one through each eye - double vision

Question 17

PHYSIOLOGY OF SIGHT

Answer 17

light rays = bent (refracted to focus on the retina)
- The image on the retina is inverted
- The brain adapts to this in early life, so images are perceived in the correct way

Question 18

ACCESSORY ORGANS OF THE EYE

Answer 18

EYEBROWS: protect eyeballs from dust, sweat and other foreign bodies
EYELIDS: protect strucutres lined with conjuntiva
>protect the eye from injury - reflect closure when eyelashes or conjunctiva is touched
-blinking spreads tears and oily secretion across the cornea (stops drying)

LACRIMAL APPARATUS (tear glands and ducts)

Question 19

EFFECTS OF AGING ON SIGHT

Answer 19

PRESBYOPIA: lens = elastic & becomes fimer = blurred vision (close range) (reading glasses)

CATARACT: opacity to lens (cloudy) - stops weak light rays. need a brighter light for reading

MACULAR DEGENRATION:

Question 20

SMELL (OLFACTION)

Answer 20

• nasal cavity
• Olfactory nerve endings/cells act as chemoreceptors in the superior nasal cavity
• Nerve fibres passed through the bone (ethmoid bone) to the olfactory bulb, into the olfactory tract
• the temporal lobe of the brain
• air entering nose = filtered, heated & humidifed
• air moved to the top of the nasal passage by convection
• An odorous substance gives off volatile (gaseous) molecules
• Inhaled and in low concentration stimulates olfactory chemoreceptors
• linked closely with stimulation of appetite & taste
• sense of smell & memory
• air filtered by hairs
• curled shelf of bones that protrudes into the breathing passages of the nose
• Divides the nasal airways into four passages = responsible for forcing inhaled air to flow in a steady, regular pattern around the largest possible surface area of the nasal mucosa.
• mucous membrane shallow blood supply, nasal mucosa cleans & warms inhaled air to prep the lungs

Question 21

NERVE

Answer 21

• nerve impulses moved into the olfactory bulb - olfactory tract - the temporal lobe of the brain

Question 22

EFFECTS OF AGING ON SCENSE OF SMELL

Answer 22

olfactory reduce around 50
- diminishes the sense to taste
- complain food taste bland
- affects perceptions of weak odurs

Question 23

HEARING AND BALANCE

Answer 23

• responds to vibration from sound waves
• ear transforms these vibrations into nerves
• impulses transmitted into the brain

Question 24

THE EAR

Answer 24

• outer ear
• middle ear
• inner ear

Question 25

OUTER EAR

Answer 25

AURICLE OR PINNA: - Fibroelastic cartalige (grooved) - Collects and channels sounds into the external acoustic meatus LOBULE: fibrous & adiposed tissue (rich blood supply) - Function of lobule unclear – may play a role in keeping ear warm. Also some limited evidence may play a minor role in balance – but very limited.

Question 26

OUTER EAR

Answer 26

EXTERNAL ACOUSTIC MEATUS (AUDITORY CANAL) - slight curve - channels sounds to the tympanic membrane (eardrum) - ceruminous glands - secrete cerumen (wax) - antibacterial properties - hair follicles

Question 27

TYMPANIC MEMRBANE (EARDRUM)

Answer 27

- seperates outer and middle ear - oval shape - layers: > outer-hairless skins. > middle: fibrous tissue > inner: mucous membrane continues with lining of the inner ear

Question 28

MIDDLE EAR

Answer 28

- irregularly shaped air-filled bony cavity - the medial wall is a very thin bone - two membrane-covered openings to the inner ear - oval and round windows pharyngotympanic tube (eustachian) Middle ear formed inside part of the temporal bone of the skull. Oval and round window transmit vibrations to the middle ear. Eustachian tube keeps air in the middle ear at atmospheric pressure. 4cm long lined with ciliated epithelial cells. Auditory Ossicles – synovial joints – held in place by ligaments.

Question 29

INNER EAR (LABYRINTH)

Answer 29

The membranous labyrinth contains endolymph suspended while the bony labyrinth contains perilymph COCHLEA: - snail-shaped - hair cells in the membranous labyrinth (basilar membrane contains auditory receptors) - sounds vibrartions = movement of perilymph ENDOLYMPH: - initiates nerve impulses for hair cells - transmitted to the brain via the vestibulocochlear nerve

Question 30

PHYSIOLOGY OF HEARING

Answer 30

Question 31

BALANCE

Answer 31

Three semi-circular canals Lie in each plane of space Similar internal structure to the cochlea Ampulla, Utricle and Saccule Inner wall – fine epithelial cells with hair cells Act as receptors Movement of the head: Fluid movement in the semi-circular canals Stimulates receptors in Ampulla, Utricle and Saccule Impulses are transmitted to brain via the Vestibulocochlear nerve - Balance is complex and involves the brains interpreting and responding to sensory information from from the eyes and the musculoskeletal system as well as the ears.

Question 32

SENSATION OF TOUCH

Answer 32

- Sensory receptors (specialised nerve endings) sensitive to touch, temperature, pressure, and pain are throughout the dermis. - Merkel cell and Meissner’s corpuscle detects light pressure, Pacinian corpuscle detects deep pressure, Ruffini organ detects movement.