Physiology Flashcards
What is CSF?
A clear colourless liquid composed mostly of water
What are the 3 major functions of CSF?
mechanical protection homeostatic function circulation
How does CSF contribute to mechanical protection?
It is a shock absorbing medium that protects brain tissue (brain floats inside the cranial cavity)
How does CSF have a homeostatic function?
PH of CSF affects pulmonary ventilation and cerebral blood flow. It also transports hormones
How does CSF help with circulation?
it is a medium for minor exchange of nutrients and waste products between blood and brain tissue
How can CSF for clinical analysis be obtained?
lumbar puncture
Does CSF contain lots or a little bit of protein?
very little protein
At 3 weeks of embryological development what does the developing nervous system consists of? What does this structure give rise to in adults?
neural canal- that adult’s brain ventricles and the spinal cords central canal
what does the chord plexus develop from?
cells in the walls of the ventricles
in the adult brain where are choroid plexuses found?
in the 3rd, 4th and lateral ventricles
How are the lateral ventricles connected to the the third ventricle?
intraventricular foramena
how are the 3rd and 4th ventricles connected?
cerebral aquaduct
how is the 4th ventricle connected to the subarachnoid space?
median aperture and lateral apertures
What does the blood brain barrier consist of?
capillary endothelium, its basal membrane and perivascular astrocytes
what do tight junctions between brain endothelial cells prevent?
paracellular movement of molecules
which parts of the brain do not have a blood brain barrier?
circumventricular organs or pineal glands
what is the function of the blood brain barrier?
protects brain from common bacterial infections and toxins
what is hydrocephalus?
accumulation of CSF in the ventricular system or around the brain
What is papilloedema?
optic disc swelling due to raised ICP
what are the visual symptoms of papilloedema?
enlarged blind spot blurring of vision visual obscuration loss of vision
what is aqueous humour?
a specialised fluid that bathes the structures of the eye
what does aqueous humour provide?
oxygen and metabolites
what cells are responsible for th production of aqueous humour?
the epithelial layer of the ciliary body
Outline the cellular structure of the retina (from anterior to posterior)
- 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
What do the photoreceptors do?
convert electromagnetic radiation to neural signals - tranduction
what are the 2 types of photoreceptor?
rods and cones
What are the 4 main regions of photoreceptors?
outer segment
inner segment
cell body
synaptic terminal
what is the resting membrane potential of photoreceptors?
- 20 mV
upon light exposure what happens to the membrane potential of photoreceptors?
it hyperpolarises
what is the name of the current that causes the membrane potential of photoreceptors to change?
the dark current
what is the signal that enables the brain to percieve objects in the visual field?
The change in Na+ with light
what are the visual pigment molecules called and where are they found?
Rhodospin present in the membrane folds in the outer segment of photoreceptor cells
What effect does light have on the sodium channels in the photoreceptor membrane - briefly outline how this happens.
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
What is the basis of phototransduction?
modulation of the dark current
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.
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.
what helps to distinguish between two nearby points?
photoreceptor spacing and refracrive power
What is visual acuity
the clarity of vision - distinguishing two nearby objects
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
Rods- dim light
cones - normal daylight
more convergence in rod syste, increasing sensitivity while decreasing acuity
how many photoreceptor types are there in the human retina and what are they?
4 types:
- short wave cone - blue light
- middle wave cone - green light
- long wave cone - red light
- rods - black and white
where are rods and cones distributed over the retina?
rods - peripheral retina
cones - central retina (fovea)
fill in the blanks:
Each eye sees part of the visual space -
but their visual fields to create a
Each eye sees part of the visual space - monocular visial field
but their visual fields overlap** to create a **binocular visual field
How is the retina divided and where is it divided?
into a nasal and hemiretina relative to the fovea
fill in the blanks
nerve fibres from the the half of each retina cross over at the
nerve fibres from the the nasal half of each retina cross over at the optic chiasm
