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CNS Physio > Lecture 5 > Flashcards

Lecture 5 Flashcards

1
Q

Where do pain fibers end?

A

In periaqueductal grey matter or periventricular nuclei

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2
Q

Periaqueductal grey matter or periventricular nuclei stimulate neurons that secrete __.

A

Enkephalins

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3
Q

Pain fibers synapse with:

A

Raphe magnus or paragigantocellularis nucleus

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4
Q

What are the causes of visceral pain?

A

1) Ischemia: Decrease or low blood flow to the tissue = tissue damage =
releases chemicals that excite the free nerve endings of pain receptors
2) Chemical irritation from perforated peptic ulcer, or acids from the biliary system
= irritates the viscera and peritoneum
3) Spasm of a hollow viscus = constriction or contraction of SI (intestinal
colic) = mechanical stimulation of the free nerve endings as they press on the
free nerve endings
4. Overdistension of a hollow viscus = increase the pressure on the walls of
the organs.

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5
Q

Cold receptors respond from -°C with a peak response at _°C.

A

7-44; 25

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6
Q

Warm receptors respond from -°C with a peak response at _°C, which can cause pain.

A

30-49; 44

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7
Q

What determines temperature sensation?

A

The relative degree of stimulation of the receptors

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8
Q

What are the 4 different receptors?

A

1) Warm
2) Cold
3) Burning hot
4) Freezing cold.

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9
Q

Can thermal receptors adapt to the stimulus?

A

Yes, but not completely

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10
Q

What does cold or warm temperature do?

A

Change the metabolic rate of the receptor = changes the rate of intracellular reaction (how?) By changing the permeability of
ions in the receptors, and the receptor potential = Change the action potential formed in the afferent neuron connected to these receptors.

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11
Q

If you increase the temperature from 15 to 20 °C:

A

The number of impulses

increases to around the level of 25°C (person feels too hot)

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12
Q

If a person stays under an increased temperature for a while, what happens?

A

There is a slight decrease in the number of impulses and the heat doesn’t feel as
intense or hot.

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13
Q

What is thermal adaptation?

A

It starts as fast adaptation then slow adaptation, but there is no complete adaptation to temperature

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14
Q

What are the 3 layers of the eye?

A

1) Sclera
2) Choroid
3) Retina

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15
Q

What surrounds 4/5 of

the eyeball? What about the last 1/5?

A

The sclera; The cornea (anteriorly)

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16
Q

What is the sclera made up of?

A

Very dense connective tissue

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17
Q

What determines whether one can undergo laser surgery or not?

A

The cornea

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18
Q

What is the choroid?

A

A vascular component of the eye which continues anteriorly with the ciliary body

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19
Q

Which muscle is part of the choroid? What does it continue as?

A

Ciliary muscle; continues anteriorly as the iris

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20
Q

What connects the ciliary body and the lens’ capsule? What is its function?

A

Suspensory ligaments, which (through the work of the ciliary muscle) change the shape of the lens.

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21
Q

What is the lens made up of?

A

Multiple layers of protein

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22
Q

What allows the lens to change shape? What are its shapes?

A

its flexibility; flatter (less convex) and fatter (more convex)

23
Q

The __ divides the eyeball into 2 cavities:

A

Lens;

1) Anterior cavity: Between the lens and cornea
2) Posterior cavity: Extends behind to the retina

24
Q

The 2 cavities of the eyeball are connected by the:

A

Pupil

25
Q

The anterior cavity is divided into 2 chambers:

A

1) Anterior to the iris

2) Posterior to the iris (between the lens and the iris)

26
Q

The anterior cavity contains a fluid called __, which the posterior cavity contains a fluid called __.

A

Aqueous humor; vitreous humor

27
Q

What does the aqueous humor do?

A

Provides nutrition to the avascular cornea.

28
Q

Where is the vitreous humor derived from?

A

The embryonic mesenchyme

29
Q

What keeps the eyeball round and distended?

A

The intraocular fluid

30
Q

Which fluid is dynamic and gets renewed?

A

Aqueous humor

31
Q

What produces the aqueous humor?

A

The ciliary processes of

the ciliary body

32
Q

What is the path of the aqueous humor?

A

Ciliary body => between the ligaments of the lens => through the pupil into the anterior chamber => goes between the cornea and the iris => through a meshwork of trabeculae => canal of schlemm => empties into aqueous veins => extraocular veins.

33
Q

Aqueous humor lies __(behind/infront of) the lens, while the vitreous humor lies __(behind/infront of) the lens.

A

Infront of; behind

34
Q

What is the normal intraocular pressure?

A

It is 15 mmHg with a range of 12-20 mmHg.

35
Q

What is the level of intraocular pressure is determined by?

A

1) The resistance to outflow of aqueous humor through the canal of Schlemm
2) The amount of aqueous humor production

36
Q

An increase in intraocular pressure can result in:

A

Damage to the optic nerve resulting in Glaucoma = blindness due to compression of the axons of the optic nerve.

37
Q

Where does the retina develop from?

A

The ectoderm

38
Q

What does the retina contain?

A

The visual receptors (Rods & cones)

39
Q

What is the central part of the retina called?

A

Macula lutea

40
Q

What’s the slight depression in the central part of the retina called?

A

Fovea

41
Q

What is the fovea important for?

A

It has the highest concentration of cones receptors

42
Q

What are cones receptors important for?

A

1) Sharp color vision

2) Highest acuity of vision

43
Q

What is the optic disc?

A

Where optic nerve fibers pass through along with retinal artery & veins. It is a blind spot (no
rods and cones).

44
Q

What are the most superficial vessels in our body?

A

Retinal vessels

45
Q

What is the pressing force that keeps the retina and choroid adherent
together?

A

The vitreous humor

46
Q

If the vitreous humor leaks, what happens?

A

Causes retinal detachment.

47
Q

What does retinal detachment cause?

A

Causes the receptors on the retina to separate from the choroid = neural death = blindness.

48
Q

Retinal detachment is a medical emergency, It has to be reattached within __ hours or else the patient will become permanently blind

A

48 hours

49
Q

When light travels between two different media it __, due to:

A

refracts (bends); the change in speed

50
Q

What is the refractive index?

A

The ratio of the speed of light in air to the speed of light in the substance.
(𝒔𝒑𝒆𝒆𝒅 𝒐𝒇 𝒍𝒊𝒈𝒉𝒕 𝒊𝒏 𝒂𝒊𝒓 (𝟑𝟎𝟎,𝟎𝟎𝟎𝑲𝒎/𝒔))/
(𝒔𝒑𝒆𝒆𝒅 𝒐𝒇 𝒍𝒊𝒈𝒉𝒕 𝒊𝒏 𝒕𝒉𝒆 𝒔𝒖𝒃𝒔𝒕𝒂𝒏𝒄e)

51
Q

Since the speed is fastest in air, the refractive index would always be:

A

1 or more.

52
Q

What is refraction?

A

Bending of light rays through an angulated interface between two media with different refractive indices.

53
Q

The degree of refraction and the resulting degree of angulation of light increases as:

A

The difference in their R.I. increases.

54
Q

The features of the eye (like cornea, lens, humor) have

different R.I. and thus they:

A

Cause light rays to bend = light rays become focused on the retina.

CNS Physio (8 decks)

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