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Ophthalmology > Physiology > Flashcards

Physiology Flashcards

1
Q

Where is CSF produced?
What is the rate of production?
How much is produced in a day?

A
  • Produced by secretory epithelium of the choroid plexus
  • 0.4ml/min
  • 500-600ml/day
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2
Q

CSF is formed ? and then circulates around ? before being absorbed ?

A
  • In the ventricles
  • The subarachnoid space
  • Into the venous circulation
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3
Q

What does CSF supply?

What does CSF remove?

A

Supplies water, amino acids and ions; removes metabolites

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4
Q

What are the 3 major functions of CSF?

A
  • Mechanical protection
  • Homeostatic function
  • Circulation
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5
Q

What aspect of the CSF is important in homeostasis and affects pulmonary ventilation and cerebral blood flow?

A

pH

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6
Q

At 3 weeks, what does the developing nervous system consist of?
What does this structure’s cavity give rise to?

A

At 3 weeks, the nervous system consists of the neural canal. The cavity of the neural canal gives rise to the ventricles and central canal of the spinal cord.

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7
Q

What is the choroid plexus?
Where is it developed from?
Which ventricles is the choroid plexus found in?

A
  • A network of capillaries in the walls of ventricles
  • Cells in the walls of the ventricles
  • 3rd, 4th and lateral
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8
Q

CSF secretion involves the transport of what ions across the epithelium from blood to CSF?

A

Na+, Cl- and HCO3-

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9
Q

Which ions and molecules does CSF have lower concentrations of than blood plasma?

A

K+, glucose and proteins

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10
Q

Which ions and molecules does CSF have higher concentrations of than blood plasma?

A

Na+ and Cl-

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11
Q

Is the production of CSF in the choroid plexus active or passive?

A

Active

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12
Q

What are ventricles?

A

Appertures which the CSF passes through to get to the subarachnoid space

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13
Q

Which ventricles is CSF produced in? (from first to last)

What makes up the final portion of CSF?

A

Lateral, 3rd, 4th. The final portion is from the brain interstitial fluid.

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14
Q

Where is the BBB?

A

Endothelial cells in brain capillaries

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15
Q

Give 3 roles of the BBB?

A
  • Prevents infections
  • Determinant for CSF analysis via lumbar puncture
  • Is an obstacle for drug delivery to the CNS
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16
Q

Which areas of the brain do not have a BBB?

A

Circumventricular organs, pineal glands

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17
Q

What are some pathologies which can occur at the ventricles, choroid plexus and CSF?

A
  • Tumours
  • Haemorrhage
  • Hydrocephalus
  • Idiopathic Intra-Cranial Hypertension
  • Papilloedema
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18
Q

What is an epidural haematoma?

A

Arterial bleed between skull and dura

19
Q

What is a subdural haematoma?

A

Venous bleed between the dura and arachnoid

20
Q

What is hydrocephalus?

A

Accumulation of CSF in the ventricular system or around the brain which can increase pressure

21
Q

What is a papilloedema?

A

Optic disc swelling due to increased ICP

22
Q

Where and how is aqueous humour produced?

A

An energy dependent process in the epithelial layer of the ciliary body

23
Q

The energy from waves of photons must be transducer into what?

A

Electrical signals

24
Q

There is a direct (vertical) pathway for signal transduction. What way is the signal passed? What way is light passed?

A

Signal: photoreceptors to ganglion cells
Light: ganglion cells to photoreceptors

25
Q

What are the two types of photoreceptor known as?

A

Rods and cones

26
Q

What state is the normal membrane potential of photoreceptors?
What happens to this upon light exposure?

A

Normal depolarised, hyper polarises with light exposure

27
Q

What are the relative concentrations of Na+ and K+:

a) in the dark
b) in response to light

A

a) roughly equal

b) Na+ is reduced so K+ is greater

28
Q

The basis of phototransduction involves a visual pigment known as what?
What is this made up of?

A

Rhodopsin- this is composed of retinal (via A derivative) and opsin (GPCR)

29
Q

What is the activated form of retinal?

A

All-trans-Retinal

30
Q

What happens when All-trans-retinal activates transducin?

A

A molecular cascade decreases cGMP. This closes Na+ channels and leads to hyperpolarisation.

31
Q

What happens to the dark current channel in the dark?

A

It is more depolarised and hence open

32
Q

What is visual acuity?

A

The ability to distinguish two nearby points

33
Q

What type of light do both rods and cones allow vision in?

A

Rods: dim light
Cones: normal daylight

34
Q

Which of rods and cones are largely spaced (i.e. low density)?

A

Rods

35
Q

More convergence in the rod system does what to sensitivity and acuity?

A

Increased sensitivity and decreased acuity

36
Q

Which photoreceptor is more abundant?

A

Rods

37
Q

What wavelengths of the EM spectrum can activate photoreceptors?

A

350-750nm

38
Q

The following sub-types of cones, correspond to what colour:

a) short wave?
b) middle wave?
c) long wave?

A

a) blue
b) green
c) red

39
Q

People with congenital cataracts often have difficulty perceiving what?

A

Shape and form

40
Q

What is amblyopia? What is the effect on vision?

A

There is no problem with the eye, but one has better vision than the other. The eyes focus on different objects and don’t see the same things.

41
Q

Where does the intraventricular foramina of Monroe pass to and from?

A

Lateral - 3rd ventricles

42
Q

Where does the cerebral aqueduct pass to and from?

A

3rd-4th ventricles

43
Q

Where do the foramina of Megendie and the foramina of Luschka pass to and from?

A

4th ventricle to subarachnoid space

Ophthalmology (12 decks)

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