Lecture 11 - Linking Neuronal Activity To Blood Flow Flashcards
What are some examples of metabolism in brain?
Neurons
Other cells: glia, microglia, fibroblasts, endothelial cells
What does metabolism in brain require?
15-20% of cardiac output
2% of body mass
What are the energy usage in the brain?
Restoration of ionic gradients
Maintaining the resting potential
Tissue maintenance
What are examples of tissue maintenance?
Cell division
Growth and repair I.e. protein synthesis, mRNA synthesis, protein and organelle transportation, neurotransmitter production and packaging
What are the primary and obligatory fuels for the brain?
Glucose
Oxygen
When does long-lasting ischaemia occur?
Following infarction
What does loss of blood supply to brain cause?
Loss of consciousness in seconds
What do muscles have the ability to do?
Function anaerobically
Muscles have a store of oxygen bound to what?
Myoglobin
What form do muscles have energy store in?
Glycogen
What do muscles produce when they are metabolising?
Vasoactive metabolites
What happens following the release of vasoactive metabolites?
Vasodilation
Increase in blood flow
What are the ways to make ATP?
Glycolysis
Cytoplasm ATP production
Generates pyruvate/lactate
What does kerbs cycle utilise?
Pyruvate/lactate
Where do most ATP come from!
Oxidation of 3 NADH via electron transport chain in mitochondria
What makes the largest portion of ATP?
Mitochondrial respiration
What is present inside axons?
Dyed stained mitochondria
What is an example of dye?
tetramethylrhodamine methyl ester (TMRM)
What happens When TMRM is placed inside axons?
Penetrates the membrane
Where can mitochondria be concentrated?
at or near node of Rancher
Synpases
What moves mitochondria on Dunedin and kinesin?
Molecular motors
Dynein and kinesin move mitochondria in 2 different directions by interacting with what?
Microtubules
What is mitochondria?
Major energy making structures within neuron/axon
Kinesin can generate movement toward what?
Ending of nerve fibre
Step along microtubule which is involved in retrograde movement of mitochondria and other organelles
What requires glucose and express glucose transporters?
Both glia and neurons
What are special feature of glucose?
Acts as energy substrate
Precursor for neurotransmitters
What is lactate shuttle?
Glia can provide lactate as a fuel for neurons and ensheathed axons
What is dependent upon perfusion pressure?
Flow of blood
Delivery of oxygen
When the perfusion pressure drops when does the flow drop also?
Flow is driven by pressure
What happens when flow falls?
Vascular bed in tissue reacts
Increase the flow to compensate for the drop in pressure
How is drop in pressure compensated
Change the resistance of capillary/vascular bed
What happens when resistance is decreased?
Increase auto regulation
define auto regulation
I stein six ability of organ to maintain constant blood flow despite changes in perfusion pressure
What does auto regulation attempt to keep?
Perfusion constant over a range of boood pressures
How is autoregulation achieved?
Changing vascular resistance across a tissue or organ
What are examples of blood flow regulation?
Myotonic
Neurogenic
Metabolic
What is myogenic regulation?
The diameters of arterioles are adjusted to keep blood flow constant
Through mechanical action of flow on the vessel walls and local hormonal effects
What does myogenic regulation not explain?
Functional increases in blood flow seen in the brain
What is neurogenic regulation?
Nerve fibres innervating the vasculature changing the tone of resistance vessels
What is metabolic regulation?
Seeks to balance cerebra blood flow to its demands
What is the hallmark of blood flow control in brain?
Localised nature of response
What was Eric Newman study?
Used retina as a model (neutrophil) to understand how nerve cells talk to the circulation and did it using microscope imagining techniques
what is retina?
Flat surface at the back of eye
What does retina have?
Substantial blood supply to provide glucose and nutrients and oxygen to metabolising nerve cells and photoreceptors
What is retinal surface composed of?
Nerve fibre layer
Where does the nerve fibre layer come from?
Retinal Ganglia that will form the optic nerve
What are present on the back of retina?
Ghostly grey size (moligolia)
Why are molioglia important?
Form structural scaffold for the formation of the structure of retina
What is active hyperaemia?
Increase in organ blood flow that is associated with an increased metabolic activity of an organ or tissue
What is a way to activate the neurons in the retina?
Shining a light - activate the photoreceptors and get information from the retina
What is an example of way of activating neurons in reruns
Flicker light stimulation
What does flicker light stimulation do?
Changes the BF
What are arterioles response measured in?
Confocal microscopy
What is the link you observed in flicker light stimulation?
Link between what neuron is doing and the blood flow
What are Muller Glia?
Large glial cells within the retina
What is one key player in the retina?
ATP
What is Apyrase?
An enzyme that gobble up any ATP that gets released within neurophil of retina
What happens when TTX is applied onto retina?
Reduces the response to light
Block sodium channels
Prevent any neuronal contribution that requires sodium channel
Why use Reina as a model system?
Study link between neuronal activity and blood flow
What does application of NMDA to brain tissue increase?
CBF by 20%
What is a NMDA receptor antagonist?
MK-801
What increases neuronal activity?
NMDA/kainite
More transmitters released
