12/ homeostasis in the nervous tissue 2 Flashcards
1
Q
where are the ventricles in the brain
A
- 2 lateral ventricles, one in each hemisphere
- meet in 3rd ventricle which leads into 4th
- thin tube runs down to spine
2
Q
function of cerebrospinal fluid csf
A
- provides physical protection - buffer (inc spinal cord)
- maintains appropriate levels of ions
- removes waste products
3
Q
what components are lower in csf than plasma
A
- aa
- K
4
Q
What is exchanged from csf to becf
A
- macronutrients - glucose
- micronutrients - vitamins
- ions - bicarb
5
Q
what is exchanged from becf to csf (into the bin)
A
- metabolic waste products eg co2
- neurotransmitters that aren’t broken down/reuptaken
6
Q
secretion and flow route of csf and absorption
A
- secreted by choroid plexus
- circulates around ventricles and central canal
- absorbed from the subarachnoid space to the venous blood system at the superior sagittal sinus
7
Q
how is csf secreted, how much is secreted
A
- 500 ml/day
- ultrafiltration of plasma into ecf across normal leaky capillaries
- selective absorption of substances into csf across choroidal epithelial cells (tight junctions - protect csf from ecf)
- free movement of substances from csf to becf across ependymal cells
8
Q
3 types of meninges
A
- leptomeninges:
- pia mater. innermost. v thin like clingfilm. leaky memb - can move freely across
- arachnoid matter. not leaky
- other. thicker, tougher.
- dura matter. outermost. thickest, toughest. follows curves of layers and circles outside.
9
Q
absorption of csf
A
- evaginations of arachnoid memb: arachnoid granulations (like big villi), arachnoid villi
- memb forms around csf and engulfs into a vesicle for transport across the cell
- increased absorption w increased intracranial pressure
- drains into circulatory system
10
Q
what can astrocytes remove from synaptic cleft
A
neurotransmitters, to recycle
10
Q
what do neurons and astrocytes remove from the extracellular space
A
- K
- if not memb potential would keep increasing as ec k conc increases
11
Q
how does increased ec K affect astrocyte function
A
- increased glucose metabolism - suggests neuronal activity increased, need more energy
- glucose transported as lactate to neurons
- increased k uptake
12
Q
what feature of astrocytes allows spatial buffering
A
- gap junctions create a syncytium - astrocytes joined together, mega cell
- redistributes K to areas of decreased activity
- transport sugars, aa, camp, ca2+
13
Q
outline neurovascular coupling
A
- increased neuron firing rate increases astrocyte ca2+
- release of vasoactive substances from astrocyte
- blood vessel diameter changes
14
Q
functional imaging techniques
A
- magnetic resonance imaging MRI allows 3d structural images of the brain
- 2 techniques detect that active neurons need more gluc, ox and blood:
- positron emission tomography PET - radioactive glucose tracers
- functional MRI fMRI - oxygen
15
Q
hydrocephalus
A
- disease, csf stops circulating properly
- caused by dilation or obstruction of ventricular system or interrupted csf absorption
- increased intracranial pressure
- loss of cells in brain
- loss of brainstem reflexes
- survival depends on part of brain thats being put under pressure
