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Nursing Year 2 OSCA > The Special Senses > Flashcards

The Special Senses Flashcards

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1
Q

What are the requirements for sensation?

A

Stimulus
Sensory receptor
Sensory pathway
Brain region for integration

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2
Q

What are the general senses + their characteristics?

A

Somatic
Visceral

They are widely distributed and simple

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3
Q

What are the special senses + their characteristics?

A 
Smell
Taste
Sight
Hearing
Balance

They are localised and complex

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4
Q

What are the sensory receptors + their stimulus?

A 
Mechanoreceptor- stretch/compression
Thermoreceptor- heat/cold
Photoreceptor- light
Chemoreceptors- chemical
Osmoreceptor- osmotic pressure
Nociceptor- pain
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5
Q

What are somatic receptors + what do they respond to?

A

Receptors in muscles, joints, mucous membranes, tendons, skin.

Tactile (touch, pressure, vibration, itch, tickle).
Thermal
Pain
Proprioception (sense of body position)

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6
Q

What are visceral receptors and what do they respond to?

A

Free nerve endings in smooth + cardiac muscle.

Monitor internal organ conditions such as:
BP
pH
Distension
Pain
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7
Q

What are the different proprioceptors + their functions?

A

Somatic - detect muscle contraction
joint position

Inner Ear - detect head position

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8
Q

Where is sensory information for proprioception sent?

A

Somatic sensory area of the cerebral cortex
- cerebellum

brain constantly monitors + adjusts posture

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9
Q

What are the different sensory organs and their receptors?

A

Tongue (taste) - taste cells
Nose (smell) - olfactory cells
Eyes (vision) - rods & cones
Ears (balance + hearing) - hair cells

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10
Q

What are the accessory structures of the eyes + their functions?

A

Eyebrows/lashes - protective
Eyelids - protective (objects, strong light)
Lacrimal glands - tears to wash out dirt etc
Conjunctivae - lubricates cornea and eyelid

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11
Q

What are the three main layers of the eye and their functions?

A

Sclera (forms cornea at front)- fibrous outer layer, protects and gives shape to eyeball
Choroid (forms ciliary body + iris at front) - rich in blood vessels, nourishes retina, absorbs light rays
Retina - rich in photoreceptors + nerves (image formation)

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12
Q

What is the function of the cornea?

A

To bend and refract light

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13
Q

What is the function of the ciliary process?

A

To secret aqueous humour

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14
Q

What is the function of the ciliary muscle?

A

Changes lens shape

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15
Q

What is the function of the iris?

A

To control light entry

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16
Q

What is the function of the lens?

A

To focus light rays

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17
Q

What is the function of the aqueous humour?

A

To bend light, circulates + nourishes front of eye

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18
Q

What is the function of the vitreous humour?

A

To bend light and maintain eye shape

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19
Q

What is the 3 steps in physiology of vision?

A

Formation of image on retina

Stimulation of photoreceptors

Visual pathway

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20
Q

What are the 4 steps in the formation of image on retina + their function?

A

Refraction of light rays - to focus them on retina

Accommodation - for close vision

Constriction of pupil- to control/channel amount of light entering

Convergence (inner movement) - for binocular vision of close objects

21
Q

What is refraction + where does it occur in the eye?

A

Refraction is the change in direction of light rays as they transition between different mediums.

In the eye the bioconvex lens bends + focuses light rays.

22
Q

Why is refraction used in the eye and how does light pass through the eye?

A

Refraction is used to focus light on the retina.

Light passes through: 
Conjunctiva 
Cornea
Aqueous fluid
Lens
Vitreous body
Retina
23
Q

What are the steps involved in accommodation for close vision?

A

Constriction of pupils
Convergence
Changing refractory power of lens

24
Q

What is the function of constriction in accommodation?

A

Assists accommodation by reducing the width of the beam of light entering the eye so if passed through the central curved part of the lens.

25
Q

What is convergence + it’s function in accommodation?

A

Convergence is the coordinated movement of both eyes in an inward direction.
- extrinsic muscles move the eyes + rotate them (nearer the object, greater the rotation)

If convergence does not occur the eyes will be focused on different objects or different parts of the same object - causing the brain to receive 2 different images which can result in double vision.

26
Q

How does changing the refractory power of the lens occur + what is its function in accommodation?

A

Changing the refractory power of the lens occurs by changes in the thickness of the lens of the eye to focus light on the retina.
- thicket for near vision, thinner for objects more than 6 metres away.

A more rounded, bulging lens required for more refraction.
-The ciliary muscles contract which causes the ligaments to slacken + the lens to bulge.

27
Q

What are common eye problems?

A

Astigmatism - abnormal curvature of the lens or cornea
Nearsightedness- eye too long, rays focus in front of retina
Farsightedness- eye too short, rays focus behind retina
Presbyopia- lens loses elasticity + stiffens with age

28
Q

What are the characteristics of the photoreceptors - rods?

A

Long and thin cells

Very sensitive to light (night vision)

Distributed toward the periphery(edge) of the retina

29
Q

What are the characteristics of the photoreceptors- cones?

A

Short and cone like

Activated in bright light (day vision)

3 types- absorb red, green or blue light (combined = colour vision) absence of photopigment causes colourblindness

Found in central portion of retina (macula lutea)

30
Q

What is the forea centralis?

A

Very centre of macula

In direct line with pupil

Tiny and responsible for visual acuity

Essential for reading and driving

31
Q

What is the visual pathway?

A

Optic nerve carries millions of neurones

Half of these cross over at optic chiasma

Optic tracts travel backward to thalamus to synapse with nerve cells

Continue backwards to both sides of brain to cerebral cortex

  • this gives slightly different perspectives of the same object (binocular vision)
    • binocular vision gives better perception of depth and relative position of objects
32
Q

What are the sensory function of the ear + where are the receptors located?

A

Hearing and balance

Receptors located deep in the inner ear and are similar in structure and work in a similar way

33
Q

What are the 3 main areas of the ear?

A

Outer ear - auditory canal to tympanic membrane, auricle

Middle ear - cavity between eardrum + inner ear containing ossicles

Inner ear - a complex of bony tunnels lined with a membrane, contains cochlea, vestibule and semi-circular canals + endolymph/perilymph fluid is found here

34
Q

How is balance detected by receptors?

1

A

Rotational movement of head causes endolymph fluid to move in semi circular canals

This is detected by hair cells located on membrane at the base of each of the 3 canals

It is the bending of the microscopic hair cells that triggers the cell to fire a nerve impulse

35
Q

How is balance detected by receptors?

2

A

Cells send information via vestibular nerve to cerebellum.

The brain integrated information from other senses (sight, proprioception) to determine position of the body and any required adjustments

36
Q

What is the balance pathway?

A

Nerve axons from ampullae + maculae form vestibular branch of vestibulocochlear nerve.

This goes to medulla oblongata and then to:

  • cerebral cortex (conscious sensation of movement)
  • cerebellum (coordinates response to balance)
  • cranial nerves (eye control)
  • spinal cord (motor control)
37
Q

Where are the receptors for hearing located?

A

Located in cochlea of inner ear

Situated along length of basilar membrane which lines the cochlear duct

Hairs are embedded in tectorial membrane that runs above

This whole structure forms the organ of corti

38
Q

What is the mechanism of hearing?

1-5

A
  1. Vibration of tympanic membrane
  2. Amplified by ossicles
  3. Vibration of oval window
  4. Movement of perilymph
  5. Movement of endolymph
39
Q

What is the mechanism of hearing?

6-10

A
  1. Hair cells on organ of corti move relative to membrane above
  2. Hairs bend
  3. Electrical activity in hair cells
  4. Nerve impulse (cochlear nerve)
  5. Translated in temporal lobe of brain + perceived as sound.
40
Q

What are the types of hearing loss?

A

Conduction deafness - poor transition of sound/vibration by external ear (ear wax) or middle ear (middle ear infection/ostosclerosis)

Sensorineural deafness - problem in cochlea (damaged hair cells) or nerve pathway (presbycussis) age related hearing loss

41
Q

How does age affect balance?

A

As we age we become less able to carry out responses to keep our balance (e.g taking a step to broaden base of support + increase stability)

42
Q

What are the reasons for reduced balance with age?

A

Slow postural reflexes (nerve impulses)

Keeping balance takes more brain power with age

Less strength in ankles, legs + trunk to produce corrective movement

Reduced range of motion

Less accurate sensory input (poor sight)

43
Q

Vision + Age

What is cataract?

A

Lens becomes cloudy due to changes in structure of lens proteins, passage of light through lens to retina is impaired, vision becomes blurred.

44
Q

Vision + age

What is macular degeneration?

A

Build up yellow material beneath retina disturbs vision.

Later proliferation of blood vessels + bleeding damages photoreceptors l.

Causes poor central vision as the macula lutea is the affect part of the retina

45
Q

Vision + age

What are floaters?

A

Small specks/shadows that move in field of views.

Strands that form in vitreous humour with age.

Brain gets used to it and ignores them.

46
Q

Vision + age

What is glaucoma?

A

Build of aqueous humour causes raised intra-occular pressure and retinal compression.

Mild visual impairment progresses to irreversible destruction of retina, damage to optic nerve and blindness.

47
Q

Vision + age

What is diabetic retinopathy?

A

Small blood vessels of retina are damaged by prolonged exposure to high blood glucose.

This reduced delivery of oxygen and nutrients to the photoreceptors causing blindness.

48
Q

Vision + age

What is presbyopia?

A

Farsightedness- lens becomes elastic and able to bulge which reduces accommodation.

Doesn’t increase risk of falls.

Nursing Year 2 OSCA (7 decks)

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