Physiology Flashcards
Where is CSF produced?
What is the rate of production?
How much is produced in a day?
- Produced by secretory epithelium of the choroid plexus
- 0.4ml/min
- 500-600ml/day
CSF is formed ? and then circulates around ? before being absorbed ?
- In the ventricles
- The subarachnoid space
- Into the venous circulation
What does CSF supply?
What does CSF remove?
Supplies water, amino acids and ions; removes metabolites
What are the 3 major functions of CSF?
- Mechanical protection
- Homeostatic function
- Circulation
What aspect of the CSF is important in homeostasis and affects pulmonary ventilation and cerebral blood flow?
pH
At 3 weeks, what does the developing nervous system consist of?
What does this structure’s cavity give rise to?
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.
What is the choroid plexus?
Where is it developed from?
Which ventricles is the choroid plexus found in?
- A network of capillaries in the walls of ventricles
- Cells in the walls of the ventricles
- 3rd, 4th and lateral
CSF secretion involves the transport of what ions across the epithelium from blood to CSF?
Na+, Cl- and HCO3-
Which ions and molecules does CSF have lower concentrations of than blood plasma?
K+, glucose and proteins
Which ions and molecules does CSF have higher concentrations of than blood plasma?
Na+ and Cl-
Is the production of CSF in the choroid plexus active or passive?
Active
What are ventricles?
Appertures which the CSF passes through to get to the subarachnoid space
Which ventricles is CSF produced in? (from first to last)
What makes up the final portion of CSF?
Lateral, 3rd, 4th. The final portion is from the brain interstitial fluid.
Where is the BBB?
Endothelial cells in brain capillaries
Give 3 roles of the BBB?
- Prevents infections
- Determinant for CSF analysis via lumbar puncture
- Is an obstacle for drug delivery to the CNS
Which areas of the brain do not have a BBB?
Circumventricular organs, pineal glands
What are some pathologies which can occur at the ventricles, choroid plexus and CSF?
- Tumours
- Haemorrhage
- Hydrocephalus
- Idiopathic Intra-Cranial Hypertension
- Papilloedema
What is an epidural haematoma?
Arterial bleed between skull and dura
What is a subdural haematoma?
Venous bleed between the dura and arachnoid
What is hydrocephalus?
Accumulation of CSF in the ventricular system or around the brain which can increase pressure
What is a papilloedema?
Optic disc swelling due to increased ICP
Where and how is aqueous humour produced?
An energy dependent process in the epithelial layer of the ciliary body
The energy from waves of photons must be transducer into what?
Electrical signals
There is a direct (vertical) pathway for signal transduction. What way is the signal passed? What way is light passed?
Signal: photoreceptors to ganglion cells
Light: ganglion cells to photoreceptors
What are the two types of photoreceptor known as?
Rods and cones
What state is the normal membrane potential of photoreceptors?
What happens to this upon light exposure?
Normal depolarised, hyper polarises with light exposure
What are the relative concentrations of Na+ and K+:
a) in the dark
b) in response to light
a) roughly equal
b) Na+ is reduced so K+ is greater
The basis of phototransduction involves a visual pigment known as what?
What is this made up of?
Rhodopsin- this is composed of retinal (via A derivative) and opsin (GPCR)
What is the activated form of retinal?
All-trans-Retinal
What happens when All-trans-retinal activates transducin?
A molecular cascade decreases cGMP. This closes Na+ channels and leads to hyperpolarisation.
What happens to the dark current channel in the dark?
It is more depolarised and hence open
What is visual acuity?
The ability to distinguish two nearby points
What type of light do both rods and cones allow vision in?
Rods: dim light
Cones: normal daylight
Which of rods and cones are largely spaced (i.e. low density)?
Rods
More convergence in the rod system does what to sensitivity and acuity?
Increased sensitivity and decreased acuity
Which photoreceptor is more abundant?
Rods
What wavelengths of the EM spectrum can activate photoreceptors?
350-750nm
The following sub-types of cones, correspond to what colour:
a) short wave?
b) middle wave?
c) long wave?
a) blue
b) green
c) red
People with congenital cataracts often have difficulty perceiving what?
Shape and form
What is amblyopia? What is the effect on vision?
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.
Where does the intraventricular foramina of Monroe pass to and from?
Lateral - 3rd ventricles
Where does the cerebral aqueduct pass to and from?
3rd-4th ventricles
Where do the foramina of Megendie and the foramina of Luschka pass to and from?
4th ventricle to subarachnoid space
