L11 Homeostasis - Pt 2 Flashcards
What is the ventricular system?
Ventricular system is a series of hollow cavities filled with cerebrospinal fluid which run throughout the brain to the spinal cord.
What is the role of the ventricular system (3)?
- Provides physical protection - Buffer.
- Maintains appropriate levels of ions.
- Removes waste products.
What is exchanged from CSF to BECF?
- Macronutrients - Glucose
- Micronutirents - Vitamins
- Ions - HCO3-
What is exchanged from BECF TO CSF?
- Metabolic waste products - CO2
- Neurotransmitters.
What is secreted by the choroid plexus?
The cerebrospinal fluid (CSF)
Describe the flow of the cerebrospinal fluid (CSF) (5)
1) Produced by choroid plexus
2) Circulates through ventricular system
3) Enters the subarachnoid space
4) Flows within the subarachnoid space
5) CSF within this space is absorbed into venous blood at the superior sagittal sinus via the arachnoid granulations
Where does the flow of cerebrospinal fluid (CSF) circulate around?
It circulates around the ventricles and central canal
How much CSF is produced each day?
Approx - 500 mls each day.
How is CSF produced? (3)
- Ultrafiltration of plasma into ECF across normal ‘leaky’ capillaries
- Selective absorption of substances into CSF across choroidal epithelial cells
- Free movement of substances from CSF to BECF across ependymal cells
BECF - Brain extracellular fluid
What are meninges?
The meninges are a vital set of membranes that protect the central nervous system (CNS), which includes the brain and spinal cord
What are the layers of meninges ?
Dura mater: The outermost, toughest layer.
Arachnoid mater: The middle, web-like layer.
Pia mater: The innermost, delicate layer that adheres directly to the CNS tissue.
What is a leptomeninge and can you give any example(s)?
Lepto means thin in greek so it means thin meninge. The pia meter and Arachnoid mater are the leptomeninges since they are the thinner (also innermost) membranes
What absorbs the CSF?
Arachnoid Granulations. They act as one-way valves, allowing CSF to flow from the subarachnoid space into the venous bloodstream.
What are the adaptations of arachnoid granulations? (3)
- Arachnoid granulations are 1cm
- Has Arachnoid villi
- Increased absorption with increased intracranial pressure
What is hydrocephalus?
Hydrocephalus is a medical condition characterized by an abnormal buildup of cerebrospinal fluid (CSF) within the ventricles (cavities) of the brain.
What are the consequences of hydrocephalus?
- Increased intracranial pressure
- Loss of cells within the brain.
- Loss of brainstem reflexes.
- Obstruction/ interrupted CSF absorption
- Dilation of ventricular system
What is the name of the thing between the Pia mater and the Arachnoid mater?
Subarachnoid space
What do neurons and astrocytes do to maintain homeostasis?
They terminate neurotransmission at the tripartite synapse to presynaptic terminal to postsynaptic terminal- recycling of neurotransmitters
What does neurons and astrocytes do in context to K+ composition?
Neurons and astrocytes remove K+ from the extracellular space to maintain a conc gradient for neuronal resting membrane potential
3 Na+ in out and 2K+ in
What can affect astrocyte function?
Increased glucose metabolism and increased K+ uptake
What is astrocytes syncytium?
The term “astrocyte syncytium” refers to the network of astrocytes in the brain that are extensively interconnected via gap junctions.
What does astrocytic syncytium allow?
It allows spatial buffering
What can gap junctions create?
They can create a syncytium
What is the role of astrocytic synctium?
It redistributes K+ to areas of decreased activity
Can also transport sugars, amino acids, cAMP, Ca2+
This is spatial buffering
