Physiology

Question 1

What is CSF?

Answer 1

A clear colourless liquid composed mostly of water

Question 2

What are the 3 major functions of CSF?

Answer 2

mechanical protection homeostatic function circulation

Question 3

How does CSF contribute to mechanical protection?

Answer 3

It is a shock absorbing medium that protects brain tissue (brain floats inside the cranial cavity)

Question 4

How does CSF have a homeostatic function?

Answer 4

PH of CSF affects pulmonary ventilation and cerebral blood flow. It also transports hormones

Question 5

How does CSF help with circulation?

Answer 5

it is a medium for minor exchange of nutrients and waste products between blood and brain tissue

Question 6

How can CSF for clinical analysis be obtained?

Answer 6

lumbar puncture

Question 7

Does CSF contain lots or a little bit of protein?

Answer 7

very little protein

Question 8

At 3 weeks of embryological development what does the developing nervous system consists of? What does this structure give rise to in adults?

Answer 8

neural canal- that adult’s brain ventricles and the spinal cords central canal

Question 9

what does the chord plexus develop from?

Answer 9

cells in the walls of the ventricles

Question 10

in the adult brain where are choroid plexuses found?

Answer 10

in the 3rd, 4th and lateral ventricles

Question 11

How are the lateral ventricles connected to the the third ventricle?

Answer 11

intraventricular foramena

Question 12

how are the 3rd and 4th ventricles connected?

Answer 12

cerebral aquaduct

Question 13

how is the 4th ventricle connected to the subarachnoid space?

Answer 13

median aperture and lateral apertures

Question 14

What does the blood brain barrier consist of?

Answer 14

capillary endothelium, its basal membrane and perivascular astrocytes

Question 15

what do tight junctions between brain endothelial cells prevent?

Answer 15

paracellular movement of molecules

Question 16

which parts of the brain do not have a blood brain barrier?

Answer 16

circumventricular organs or pineal glands

Question 17

what is the function of the blood brain barrier?

Answer 17

protects brain from common bacterial infections and toxins

Question 18

what is hydrocephalus?

Answer 18

accumulation of CSF in the ventricular system or around the brain

Question 19

What is papilloedema?

Answer 19

optic disc swelling due to raised ICP

Question 20

what are the visual symptoms of papilloedema?

Answer 20

enlarged blind spot blurring of vision visual obscuration loss of vision

Question 21

what is aqueous humour?

Answer 21

a specialised fluid that bathes the structures of the eye

Question 22

what does aqueous humour provide?

Answer 22

oxygen and metabolites

Question 23

what cells are responsible for th production of aqueous humour?

Answer 23

the epithelial layer of the ciliary body

Question 24

Outline the cellular structure of the retina (from anterior to posterior)

Answer 24

• photoreceptor - receive signal
• [horizontal cells (input from photoreceptors project to other photoreceptors and bipolar cells)] - lateral connection
• bipolar cells
• amacrine cells (input from thebipolar cells and project to ganglion cells, bipolar cells, and other amacrine cells)] -lateral connection
• ganglion cells

Question 25

What do the photoreceptors do?

Answer 25

convert electromagnetic radiation to neural signals - tranduction

Question 26

what are the 2 types of photoreceptor?

Answer 26

rods and cones

Question 27

What are the 4 main regions of photoreceptors?

Answer 27

outer segment inner segment cell body synaptic terminal

Question 28

what is the resting membrane potential of photoreceptors?

Answer 28

- 20 mV

Question 29

upon light exposure what happens to the membrane potential of photoreceptors?

Answer 29

it hyperpolarises

Question 30

what is the name of the current that causes the membrane potential of photoreceptors to change?

Answer 30

the dark current

Question 31

what is the signal that enables the brain to percieve objects in the visual field?

Answer 31

The change in Na⁺ with light

Question 32

what are the visual pigment molecules called and where are they found?

Answer 32

Rhodospin present in the membrane folds in the outer segment of photoreceptor cells

Question 33

What effect does light have on the sodium channels in the photoreceptor membrane - briefly outline how this happens.

Answer 33

causes the Na⁺ channels to close light causes change in the structure of the retinal in Rhodopsin This actiavates a molecular cascade --\> reduced cGMP closure of cGMP Na+ channels reduced Na+ entry results in hyperpolarisation

Question 34

What is the basis of phototransduction?

Answer 34

modulation of the dark current

Question 35

# Fill in the blanks dark- current channels are in the dark and in response to light They are gated channels that are permeable to The resting membrane potential is _._ This is more than most neurons and so results in the steady release of neurotransmitter.

Answer 35

dark- current channels are **_open**_ in the dark and _**closed_** in response to light They are **_cGMP_** gated channels that are permeable to **_Na+_** The resting membrane potential is **_-20mV_**_._ This is more **_positive_** than most neurons and so results in the steady release of neurotransmitter.

Question 36

what helps to distinguish between two nearby points?

Answer 36

photoreceptor spacing and refracrive power

Question 37

What is visual acuity

Answer 37

the clarity of vision - distinguishing two nearby objects

Question 38

in what type of light do rods help us to see in? In what type of light do cones help s to see in? breifly explain why

Answer 38

Rods- dim light cones - normal daylight more convergence in rod syste, increasing sensitivity while decreasing acuity

Question 39

how many photoreceptor types are there in the human retina and what are they?

Answer 39

4 types: 1. short wave cone - blue light 2. middle wave cone - green light 3. long wave cone - red light 4. rods - black and white

Question 40

where are rods and cones distributed over the retina? rods - peripheral retina cones - central retina (fovea)

Question 41

# fill in the blanks: Each eye sees part of the visual space - but their visual fields to create a

Answer 41

Each eye sees part of the visual space - **_monocular visial field_** but their visual fields **_overlap**_ to create a _**binocular visual field_**

Question 42

How is the retina divided and where is it divided?

Answer 42

into a nasal and hemiretina relative to the fovea

Question 43

# fill in the blanks nerve fibres from the the half of each retina cross over at the

Answer 43

nerve fibres from the the **_nasal_** half of each retina cross over at the **_optic chiasm_**