L10 Homeostasis - Pt 1

Question 1

What is the neuronal microenvironment?

Answer 1

The Neuronal microenvironment is composed of:
1. Glia
2. Capillaries
3. Other neurons
4. Extracellular space - ECM and Brain extracellular fluid (BECF).

Question 2

What does the neuronal microenvironment consist of?

Answer 2

Composed of:
- Glia
- Capillaries
- Other neurons
- Extracellular Space

Question 3

What does the extracellular space contain?

Answer 3

Extracellular matrix
Brain extracellular fluid (BECF)

Question 4

What is the relationship between BECF and neurons?

Answer 4

BECF can both influence neurons and be influenced by neurons

Question 5

What is the consequence of uncontrolled activity in a neuron?

Answer 5

Change in BECF composition causing neuronal dysfunction and neuronal death.

Question 6

Why must BECF composition be tightly regulated?

Question 7

How can neuronal activity change the composition of the BECF?

Answer 7

• Increased K+ concentration
• Changes in O2, glucose and CO2 concentrations
• Increased H+, thus acidification
• Neurotransmitter concentrations

Question 8

How can a change in BECF composition change neuronal activity?

Answer 8

Increased K+ concentration in the BECF could elevate resting potential bringing the cell closer to threshold for firing an action potential.

Increase in neurotransmitter release.

Question 9

How do we regulate the neuronal microenvironment, including BECF?

Answer 9

Through:
1. Blood brain barrier (BBB).
2. Cerebrospinal fluid in ventricular system.
3. Neurons
4. Glial cells - focus on astrocytes.

Question 10

Explain the purpose and strucuture of the blood brain barrier

Answer 10

The blood brain barrier is a very tightly controlled system. Rather than being a simple wall, it is a very active, and selective system. It allows the brain to have the correct chemical enviroment to function correctly.

Understanding the BBB is crucial in developing treatments for neurological disorders, as many drugs struggle to cross this barrier.

Question 11

How was the blood brain barrier first discovered?

Answer 11

The blood brain barrier was first discovered by intravenous injection of dyes in which the dyes pass across leaky capillaries staining soft tissues, but no staining in the brain.

Question 12

What is the function of the blood brain barrier?

Answer 12

Function - to protect neurons from fluctuations in concentrations of substances in the blood

Question 13

Give me examples on how the blood brain barrier protect neurons from fluctuations in concencentration of substances

Answer 13

Buffer the brain against fluctuations in blood composition.
Maintain a stable internal environment that is essential for optimal neuronal function.
By maintaining homeostasis, the BBB is a crucial factor in the health of the nervous system.

Question 14

How is BBB maintained?

Answer 14

• Tight junctions between endothelial cells prevents the paracellular route
• Thick basement membrane
• Astrocytic endfeet

Question 15

What important molecules move via the transcellular route?

Question 16

Why does the BBB have increased numbers of mitochondria?

Answer 16

Increased number of mitochondria needed for active transport

Question 17

What kind of molecules can pass through the BBB easily?

Answer 17

Small, uncharged and/or lipid soluble can pass the BBB more easily

Question 18

What are the leaky regions of the blood brain barrier?

Answer 18

• Choroid plexuses – ventricular system
• Circumventricular organs

Question 19

Why have leaky areas of the BBB?

Answer 19

• Hormone release from the hpothalamus and pituitary gland.
• Osmoreceptors like OVLT and SFO.
• Temperature control centres and fever - cytokines.