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Undeleted > A&P Chapter 16 Special Senses > Flashcards

A&P Chapter 16 Special Senses Flashcards

1
Q

What are the three layers of the eye?

A

Fibrous layer (Sclera/Cornea), Vascular layer (Choroid), Inner Layer (Retina)

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2
Q

Describe the Fibrous layer of the Eye

A

Made of the Sclera and the Cornea where light passes through the outer eye.

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3
Q

Describe the Vascular layer of the Eye

A

Made of the Choroid, Ciliary body and Iris.

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4
Q

Describe the Choroid

A

The pigmented vascular layer of the eye.

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5
Q

Describe the Ciliary Body

A

The thickened portion of the choroid that supports the lens and iris as well as produces fluid known as aqueous humor.

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6
Q

Describe the Iris

A

The pigmented tissues that controls the amount of light entering the eye. Smooth muscle attached to the iris controls the diameter of the opening (pupil).

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7
Q

Describe the Inner Layer of the Eye

A

The inner layer is the retina which is the neural portion of the eye and part of the optic nerve.

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8
Q

What are the optical components of the eye? What do they do (generally speaking)?

A

The Cornea, Aqueous Humor, Lens and Vitreous body

They transmit, refract and focus light as it passes through the eye.

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9
Q

Describe the Cornea

A

The clear portion of the Sclera (most anterior)

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10
Q

Describe the Aqueous Humor

A

The fluid in the anterior and posterior chambers that is secreted by the ciliary body and reabsorbed into the blood stream.

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11
Q

How does GLAUCOMA occur?

A

When the fluid secreted by the ciliary body isn’t reabsorbed fast enough the fluid pressure increases causing Glaucoma.

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12
Q

Describe the Lens

A

It is composed of connective tissue and epithelial cells, it helps focus light onto the retina.

It is suspended by Suspensory ligaments attached to the ciliary body. Smooth muscle in the ciliary body pulls on the lens and changes it’s shape allowing light to focus from near or distant objects on the retina.

Age, diabetes, UV damage, smoking can cause the lens to become cloudy leading to CATARACTS.

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13
Q

Explain how CATARACTS are formed

A

They are formed when age, diabetes, UV damage or smoking causes the lens to become cloudy.

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14
Q

Describe the Vitreous body

A

The large body behind the lens that is filled with a transparent jelly.

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15
Q

How many muscles attach the sclera of the eye to the orbit wall?

A

6 total. 4 rectus muscles and 2 oblique.

Rectus muscles allow the eye to move in straight lines up down and left/right.

Oblique muscles allow the eye to look out and up or down and in.

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16
Q

What is the “chemical formula” for the eye muscles?

A

(LR6 SO4)3

CN IV (trochlear nerve)=Superior Oblique
CN VI (Abducens nerve)=Lateral Rectus, abducts the eye.
CN III (Oculomotor nerve)= The other 4 muscles.
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17
Q

To see an image what has to happen to the image?

A

It has to be focused directly on the retina.

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18
Q

Explain what happens to light as it passes through the eye

A

It is REFRACTED (bent) by the cornea, aqueous humor, lens and vitreous humor, it is then focused on the retina.

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19
Q

What is ACCOMODATION?

A

It is the term describing the lens ability to adjust shape to focus light on the retina. All the other components of the eye, the cornea, aqueous humor, ect… are constant but the lens can change shape.

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20
Q

What is PRESBYOPIA?

A

The loss of the ability to change the shape of the lens that comes with old age.

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21
Q

What is MYOPIA?

A

Nearsightedness, light is refracted TOO much by the cornea or the eyeball is too long cause light to focus INFRONT of the retina.

It is corrected by CONCAVE Lenses, causing the light to spread out slightly before entering the eye.

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22
Q

What is HYPEROPIA?

A

Farsightedness, light is NOT refracted enough by the cornea or the eyeball is too short causing light to focus BEHIND the retina.

Corrected by CONVEX lenses that focus the light slightly before it enters the eye.

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23
Q

How do we “see” an image?

A

Light stimulates neurons in the retina which transmits those signals through the optic nerve to the visual processing centers of the brain (Occipital lobe).

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24
Q

What are the components of the Retina? Start with deepest.

A
  1. Pigmented Epithelium
  2. Photoreceptors
  3. Bipolar Cells
  4. Ganglion Cells
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25
Q

Describe the Pigmented Epithelium in the Retina

A

They are dark cells that aborb excess light not absorbed by photoreceptors, they prevent excess light from scattering throughout the eye.

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26
Q

Describe the Photoreceptors in the Retina

A

They are specialized cells that absorb light and generate a chemical/electrical signal.

Two types: Rods/Cones

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27
Q

What are RODS?

A

One of the two types of Photoreceptors.

They are responsible for “night vision” which allows you to see black, white and shades of gray. Rods are able to be stimulated by very low light intensity.

28
Q

What are CONES?

A

One of the two types of Photoreceptors

They are responsible for “day vision” and color vision. Must be exposed by fairly bright light to be stimulated.

There are 3 types of Cones, BLUE, GREEN, and RED cones. They are stimulated by light of different wavelengths.

29
Q

What are BIPOLAR CELLS in the Retina?

A

They receive signals from rods and cones and pass them to the ganglion cells.

30
Q

What are the GANGLION Cells in the Retina?

A

They receive signals from the bipolar cells, the axons of the ganglion cells combine to form the optic nerves.

31
Q

The RODS and 3 Types of CONES absorb all light, what determines which wavelengths of light each will absorb?

A

Pigment proteins in each cell.

32
Q

What is the pigment protein in Rod Cells called?

A

RHODOPSIN

33
Q

What is the pigment protein in the Cone cells called?

A

PHOTOPSIN, there are 3 types, one for each type of CONE.

34
Q

What are Rhodopsin and Photopsin composed of?

A

A molecule called cis-RETINAL (which is a form of vit. A.) and a protein called an OPSIN

35
Q

Describe the Generation of VISUAL SIGNALS

A

In order to see an image, rods and cones must be stimulated by light, then pass that signal onto bipolar cells who then pass that onto ganglion cells whos axons form the optic nerve.

36
Q

Explain what happens to an unstimulated photoreceptor.

A

In an unstimulated photoreceptor LIGAND gated Na+ channels remain open due to the presence of cAMP (the ligand which binds to the Na+ channel allowing it to constantly flow into the cell.)

Na+ constantly flows into the cell and then is pumped back out by the Na+/K+ ATPase pump.

As long as Na+ is flowing into and then out of the cell the photoreceptor will release GLUTAMATE (an inhibitory amino acid neurotransmitter) that INHIBITS the bipolar cell preventing it from generating an action potential.

37
Q

What is GLUTAMATE?

A

An INHIBITORY amino acid neurotransmitter that photoreceptors release when they are UNSTIMULATED which prevents the BIPOLAR cells from generating an action potential passing the signal along to the Ganglion cells.

38
Q

Explains what happens to a stimulated photoreceptor.

A

When a photoreceptor is stimulated by light the cis-RETINAL in the pigment is converted into TRANS-RETINAL which then disassociated from OPSIN.

The OPSIN protein then degrades the cGMP which allows the Na+ ion channels to CLOSE.

The closing of the Na+ channels prevents the photoreceptor from releasing GLUTAMATE.

When glutamate is prevented from being released the bipolar is no longer inhibited and it passes the signal to the ganglion cell.

39
Q

What part of the optic nerve fibers cross the optic chiasm and travel on the opposite side of the brain?

A

The medial 1/2.

40
Q

What are the optic fibers called AFTER they cross the optic chiasm?

A

Optic tracts

41
Q

Where do the optic tracts travel?

A

To the thalamus where the fibers synapse with another neuron that then travels to the visual association areas in the occipital lobe of the cerebral cortex.

42
Q

Where is the LEFT field of vision processed?

A

The images in the left field of view are reflected onto the LATERAL part of your right retina and the medial part of your left retina. The medial fibers of the left retina cross over to the right side and travel with the other fibers to the RIGHT SIDE OF THE BRAIN.

43
Q

Where is the RIGHT field of vision processed?

A

The LEFT SIDE OF THE BRAIN.

44
Q

What is hearing in it’s simplest terms?

A

The disruption or vibration of air molecules detected by the human auditory system.

45
Q

What are the three anatomical zones of the ear?

A

Outer, Middle and Inner ears

46
Q

Describe the Outer Ear

A

The Pinna or Auricle and the auditory canal.

47
Q

Describe the Middle Ear

A

It is located within the TEMPORAL BONE.

The Tympanic membrane marks the beginning of the middle ear.

The auditory tube connects the middle ear with the back of the throat. This allows equalization of pressure on both sides of the tympanic membrane.

The ossicles consisting of the Malleus, Incus and Stapes exist in the middle ear, they transmit the vibrations of the tympanic membrane to the inner ear.

48
Q

Describe the Tympanic Membrane

A

It marks the beginning of the Middle ear. It vibrates freely in response to sound waves and sensory innervation from the Vagus and Trigeminal nerves make it very sensitive to pain.

49
Q

What are the auditory ossicles?

A

The three tiny bones that transmit vibrations from the tympanic membrane to the inner ear.

The bones are the Malleus, Incus and Stapes.

50
Q

Describe the Inner ear

A

It is comprised of 2 main components, the Vestibule and the Cochlea.

The inner ear is housed within a maze of bone located in the temporal bone called the BONY LABYRINTH. The bony labyrinth is lined with MEMBRANOUS LABYRINTH.

51
Q

Describe the Vestibule

A

The organ responsible for sensing equilibrium.

52
Q

Describe the Cochlea

A

The organ of hearing

53
Q

What is PERILYMPH?

A

The cushioning fluid located between the bony and membranous labyrinth.

54
Q

What is ENDOLYMPH?

A

The fluid found within the membranous labyrinth.

55
Q

Describe the Cochlea

A

It is the spiral shaped organ of hearing.

It has three chambers. The Scala Vestibuli (upper chamber), the Cochlear duct (middle chamber) and the Scala tympani (lower chamber)

56
Q

Describe the Vestibule

A

The organ responsible for sensing equilibrium.

57
Q

Describe the Cochlea

A

The organ of hearing

58
Q

What is PERILYMPH?

A

The cushioning fluid located between the bony and membranous labyrinth.

59
Q

What is ENDOLYMPH?

A

The fluid found within the membranous labyrinth.

60
Q

Describe the Cochlea

A

It is the spiral shaped organ of hearing.

It has three chambers. The Scala Vestibuli (upper chamber), the Cochlear duct (middle chamber) and the Scala tympani (lower chamber)

61
Q

What is the SPIRAL ORGAN of CORTI?

A

A collection of sensory cells (HAIR CELLS) covered by a gelatinous TECTORIAL MEMBRANE that translates mechanical vibrations into nerve impulses.

62
Q

What are HAIR CELLS?

A

The sensory cells in the SPIRAL ORGAN of CORTI that translates mechanical vibrations into nerve impulses.

63
Q

Describe the physiology of how we hear a sound

A
  1. Air movement causes vibration of the tympanic membrane which causes the ossicles of the middle ear to move.
  2. The stapes vibrates and causes a wave in the PERILYMPH of the scala vestibule which causes a wave in the ENDOLYMPH which causes movement of the basilar membrane.
  3. As the basilar membrane moves, the hair cells are pushed up against the stationary tectorial membrane, causing them to bend.
  4. Bending of the hair cells triggers a nerve impulse that travels through the CHOCHLEAR NERVE.
64
Q

Movement of the HAIR CELLS causes what to open?

A

K+ Ion Channels, this triggers an action potential that is transmitted through the cochlear nerve to the primary auditory cortex of the brain.

65
Q

Where do the nerve fibers of the VESTIBULOCOCHLEAR nerve travel?

A

To the PONS

66
Q

Describe the transmission of a nerve signal from the VESTIBULOCOCHLEAR nerve to the primary auditory cortex.

A

The nerve fibers from the Vestibulocochlear nerve travel to the PONS then synapse with a 2nd order neuron.

the 2nd order neuron travels to the MIDBRAIN where it synapses with a 3rd order neuron.

the 3rd order neuron travels to the THALAMUS where it finally synapses with a 4th order neuron that travels to the primary auditory cortex.

67
Q

How many neurons does the auditory system use to transmit signals from the hair cells to the brain?

A

4, From the hair cells to the pons, the pons to the midbrain, the midbrain to the thalamus, the thalamus to the primary auditory cortex.

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