Lecture 3- Where is the nervous system? COPY Flashcards
Why does the nervous system need so much protection?
-it is vital and relatively fragile, CNS= composition of a yoghurt
What is the protection of the CNS?
-skull (bony cavity) -meninges including CSF
What are the negatives about having the brain inside a skull?
-it is a cavity of a fixed volume,if the tissue increase in volume than damage! pressure increase, you push things around and that’s bad, blood flow into brain is compromised if pressure is increased -dangers brought about by eodema
What are the meninges and what do they look like?
-the meninges provide a space for things to circulate, it can communicate with the endocrine system, also it’s a way of things to leave the brain like if something bad in there -dura=thick connective tissue -arachnoid=there is fluid, the cerebrospinal fluid, like rarefired blood plasma without protein and any big molecules, lot of the major blood vessels that can be seen on the outside of the brain are there,arachnoid has the little extensions that join on to the pia -pia -protective coverings of the brain,meninges have own blood supply, tough structure, none of the detail of the brain is visible when the meninges on. -there is fluid all around the CNS, in a sense it is floating in this casing of fluid -all also in around the spinal cord
What is the superior saggital sinus?
-saggital plane= the midline the dura there splits in half leaving space in the middle= the space call vena sinus =vein but niot floppy, it is filled with blood -in between the hemispheres there is a large vein -you can see there is a communication between the arachnoid layer and the vena sinus so that CSF can leak to the venus sinus into the blood
How is the CSF removed from the subarachnoid space?
-CSF is made all the time and fixed volume and CSF is removed via the granulations in the vena sinus so it is taken away with the blood
What are the two types of matter in the brain and what composition are they?
-section through the frontal lobes and bit of brain stem -blue= ventricles, the black thingy is the connection to the third ventricle -white matter quite hard, grey matter quite soft
Why is white matter white?
-because of the insulating myelin sheaths, in the CNS this is produced by the oligodendrocytes and in the PNS by the Schwann cells –layers and layers of membranes that insulate the axons, = membranes are lipids and those are white -lot of fatty insulations, most axons the re myelinated
What are the little dots in the picture and what do they tell us?
-collagen bundles= thanks to that can tell it’s peripheral nervous system -PNS protects itself by the collagen wrapped around it
How do oligodendrocytes differ from the Schwann cells?
-this is in the CNS= oligodendrocytes -oligo= mini, denrocytes= branches -they branch out unlike schwann cells -the condensed cell membranes of the myelin sheath are mostly lipid and give the white matter its white fatty appearance
Which is more vascularised the grey or the white matter?
-grey matter more vascularised than white matter -brain extremely vascularised -white matter= the axons grey matter the neurons and synapses= need more energy so more vascularisation -every neuron is about 10-20 microns away from a capillary= that is how well they are supplied for (the picture:put in latex into the vessels and then dissolve all the tissues so you can see the vessels)
How much of the cardiac output goes to the brain?
-15-20%, high energy demand (to a structure that is about 1,5 kg of your body weight)
What sort of O2 metabolism does the brain have?
-obligate aerobic metabolism, O2 is essential -only adrenal gland needs more O2 -loss of O2 for a few minutes, glucose for 10-15min is fatal for neurons (and neurons are vital)
What sort of energy source does the brain use?
-glucose (only that) -totally dependent on glucose supply via blood -can only use glucose, when you’re fasting, gluceogenesis is really just for the benefit of the brain other tissues can use other things -brain has a dominant role over how the metabolism supports the body
What supplies the brain with energy?
-the mitochondria via glucose (aerobic respiration)
What are the three major arteries of the brain?
-anterior cerebral artery -middle cerebral artery -posterior cerebral artery -most of the oxygen (in the blood) goes from the outside of the brain to the inside -it has major arteries, they form 3 territories -all of those come from the middle corrotid artery, aortic arch into the head