supporting the brain Flashcards
week 3
1
Q
what are meninges?
A
- Tough connective tissue covering the entire nervous system
- Transports all the central spinal fluid- crucial to the functioning of the brain, spinal cord and periphery nervous system.
- Dura mater: outer layer; thick, tough & flexible but not stretchable
○ Inflexible- around the brain. - Arachnoid membrane: middle layer, located between dura mater & pia mater – soft & spongy
○ Similar to spiders web
○ Impermeable to CSF- cerebrospinal fluid. - Pia mater: clings to surface of brain & spinal cord; thin & delicate, smaller surface blood vessels found here
○ Impermeable to CSF
○ Very thin layer - Subarachnoid space: Fluid-filled space between arachnoid membrane & pia mater - cushions brain
Hollow space that holds the fluid.
2
Q
what layers of the meninges is the CNS covered by?
A
- dura matter
- arachnoid membrane
- pia matter
3
Q
what are the two layers of the meninges that fuse in the PNS?
A
- dura and pia matter fuse
- sheath protects spinal and cranial nerves and the autonomic ganglia
- arachnoid membrane is not present.
4
Q
what does the forebrain split into?
A
the telencephelon
diencephelon
* both form together to make the prosencephelon
5
Q
what does the midbrain splin into?
A
the mesencephalon
6
Q
what does the hindbrain splint into?
A
myencephalon (medulla)
metencephalon= pons and cerebellum
7
Q
what is the ventricular system?
A
- Ventricles: hollow spaces within brain, filled with cerebrospinal fluid
- Interconnected
- Cerebrospinal fluid (CSF): clear fluid (similar to blood plasma)
8
Q
what arethe 4 ventruicles of the ventricular system?
A
- Lateral ventricles sited in centre of telencephalon – largest
- 3rd ventricle sited at midline in centre of diencephalon
- Cerebral aqueduct is a long tube in mesencephalon connects 3rd & 4th ventricles - Due to it being so thin, there can be obstructions to it that occur.
- 4th ventricle found between cerebellum & pons
- Neurons need to be kept at very specific levels of plasma concertation
9
Q
what is the cerevrospinal fluid?
A
- CSF
- Extracted from blood
- Made in lateral ventricle and 3rd ventricle, lot of blood from the brain is used.
- Filtered by the blood- specific.
- Extract all the CSF from the blood
- Large consistency of blood
- Clearer than blood
- Fine filtering system
- Takes out the bigger proteins
- Removes pathogens that aren’t relevant to the functioning of the brain. - Consists of ions, water, protein, glucose
- Produced constantly from choroid plexus
- Total volume of CSF is ~125 ml
- Takes 3 hrs for half CSF to be replaced (half-life)
- Across 1 day, turnover of about half a litre.
- Absorbed into the subarachnoid spaces.
- Largely plasma
10
Q
what is the CSF Flow?
A
- Produced by the choroid plexus of lateral ventricles
- Flows to 3rd ventricle where more is produced
- Flows through cerebral aqueduct to 4th ventricle
- Leaves ventricles to flow into subarachnoid space around CNS – where it is reabsorbed into blood stream through arachnoid granulations
- Cells that absorb the CSF and dispose of it.
11
Q
what are the vital functions of the CSF?
A
- Protection
- Buoyancy: supports the brain
- Waste reduction: lots of metabolites that build up in the brain that need removing
- Transport: nutrients and hormones
12
Q
what is they hydrocephalus?
A
- Accumulation of CSF within the cerebral ventricles
○ Blockages of structure or function due to communication leading to more CSF than needed - Leads to ventricular dilatation (bigger)
- Classified into two types
○ Obstructive hydrocephalus
○ Communicating hydrocephalus
13
Q
what is the glia?
A
- “glue”
- Provide nutrient
- Supporting cells of the nervous system
- Several types, each with a special role:
○ Astrocytes: star cells, star functions
○ Microglia: umbrella term for lots of little cells that perform immune functioning around the brain
- Phagocytosis around the brain.
○ Oligodendrocytes: support cells for making of the myelin sheath CNS, spide like form
○ Schwann cells : PNS support the myelin sheath - Can be split off into two types:
○ Micro glia/ Macro glia
14
Q
what are astrocytes?
A
- Physical support – “neuron glue”
○ Hold neurons in place in the extracellular fluid.
○ Extracellular concentration of ions - Nourish neurons: wrap blood vessels to receive, store & release nutrients to neurons
○ Thought that from the blood the astrocytes transport the blood and passes it to the neurons. - Help control chemical composition of extracellular fluid
○ Maintains the resting potential of the cell -70mV - Surround & isolate synapse (limit NT dispersion)
○ Recent finding
Key to the neurotransmitter dispersion= degradation thorough astrocytes, performs phagocytosis.
15
Q
how does phagocytosis affect astrocytes?
A
- Clean up debris (e.g., dead cells) in the brain
- special astrocytes move around CNS engulfing & digesting debris (phagocytosis)
○ Move around the CNS and perform phagocytotic role of taking in debris that needs taking back before the next excitatory impulse of the neurotransmitter for it to have the same effect- if not it will not occur. - Form scar tissue in place of dead tissue
- Released in non-harmful way.
16
Q
what is amyotrophic lateral sclerosis (ALS): lou gehrig’s disease?
A
- Most common form of motor neuron disease
○ Attacks the nerve cells through malfunctioning of astrocytes - Rapidly progressive, leading to fatality
○ 2-3 years
○ Affects all of nerve system - Attacks nerve cells
- Lose all voluntary muscle control
○ respiration - If it affects vital organs and respiratory system will shut down the body and prevent breathing- ultimately kills person.
- Affects nerves connected to muscles that allow us to live.
- 5000 people live with the disease at any one time in UK
- 1 in 400 get MS
17
Q
how do astrocytes influence memory?
A
- Astrocytes can influence gamma oscillations such as memory
- Astrocytes are integral to memory functioning’s.
- May be other cognitive functions they are key to
- Einstein had more astrocytes than the average person
- Brain is never at rest- EEG reveal oscillations occurring at many frequencies- very low frequencies.
18
Q
what are microglia?
A
- Smallest glial cells
- Phagocytes- break it down
- Representative of immune system in brain
○ protect brain from invading microorganisms
○ Don’t get in the way of synaptic transmission of CSF. - Primarily responsible for inflammatory reaction in response to brain damage
- Thought to have role in:
○ Neurodegenerative disorders (Alzheimer’s & Parkinson’s Disease)
○ Viral infections (HIV)
19
Q
what is the significance of oligodentrites and shwann cells?
A
- Schwann Cells (peripheral NS)
- Oligodendrocytes (central NS)
- Contain fatty tissue called myelin that wraps around neuron axons
○ Help the speed of action potential
○ Protects and supports the neural system. - Forms insulating coating: myelin sheath
- Schwann cells - wrap individual axons
- Oligodendrocyte - wrap several axons
20
Q
what was the historic view of glia?
A
support cell for the nurons
21
Q
what does new research suggest about glial cells?
A
Can communicate among themselves, sense neural activity and control it
22
Q
how do glial cells produce evidence against the neuron doctrine?
A
they dont have synapses
23
Q
why wasnt glial cells communication discovered sooner?
A
○ Only 15% of neurons seen, glia was not even seen
§ Known they gave structural support- not interesting
§ Preconceptions
○ Using wring tools such as electrodes to see electrical activity- glia don’t communicate electronically
§ Need laser and video microscopes to see communication of ions flowing into a cell
* Glial cells respond to neural activity in the brain.
24
Q
what kind of dieases could glial research help with?
A
- Psychiatric conditions
- Neurological conditions: migraines to Alzheimer’s
- HIV
25
what is the brain's blood supply?
* Brain receives 15- 20% of body's blood supply
○ Uses a lot of energy in comparison to other organs so needs a lot of blood.
○ No nucleus/mitochondria can make energy through ATP.
* Nutrients & oxygen carried to brain by blood vessels
26
what is the basic functioning of the blood?
1. Blood brings materials necessary for brain function
○ Oxygen
○ Nutrients (carbohydrate, amino acids, fats, vitamins) perform a number of different roles
○ Hormones: in endocrine system- chemical actions, have advantage over action potential as they last longer and can target regions better. Benefits for the whole body.
2. Blood removes materials from the brain from the ventricles.
○ Carbon dioxide
○ Lactate- acid used in muscular functioning of the brain
○ Hormones- may release acetylcholine
Ammonia
27
what is the blood-brain barrier (BBB)?
* Is key to preventing pathogens and extracellular fluids that aren't good for maintain homeostatic conditions for action potential.
* Refined version of the blood: CSF.
○ Sensitive to extracellular fluid.
* Semi-permeable barrier between blood & brain
○ Some substances cross barrier & others can’t
* In most parts of body the smallest blood vessels (capillaries) are lined with endothelial cells
* Small spaces exist between each endothelial cell so substances can move across capillary walls
* Between capillaries and muscles.
* In brain= endothelia cells more choosing on what they left in and out of the brain.
○ Allow for transport of oxygen
○ Wire mesh to make the BBB tighten
○ Mesh= lengths of protein pushing the endothelia cells together.
Disadvantages for medicine as its hard to get drugs into the brain because of its highly selective nature.
* In brain, no spaces exist between endothelial cells & substances cannot pass over capillary wall – BBB
○ Due to the mesh that holds them together
○ Water soluble/ lipid dissolvable can pass through
Active transport can help respective molecules pass in and out.
28
what are the 3 vital functions of the BBB?
1. Protects brain from "foreign substances" in blood that may injure brain
2. Protects brain from hormones & neurotransmitters in the rest of body
3. Maintains a constant environment for brain
29
what are the substances in the BBB?
* Lipid soluble molecules are able to penetrate through BBB relatively easily via lipid membranes of cells
○ E.g.: pathogens
* Water soluble molecules can only use specialised carrier-mediated transport mechanisms
* Active transport allows some substances to move across capillary walls (e.g., glucose transporters)
* Barrier is weaker in some areas
Can be caused by infections.
30
what type of cell is not located in the CNS?
Schwann cells
31
what layer of the meninges is not present in the PNS?
Arachnoid membrane
32
which ventricle is located in the telencephalon?
lateral ventricle
33
CSF is first produced in which part of the ventricular system?
Choroid plexus
34
which type of hydrocephalus is caused by a blockage?
obstructive hydrocephalus
35
describe the location and function of cerebrospinal fluid (CSF) within the ventricular system
* CSF is produced in the choroid plexus which has rich blood supply and up to the 4th ventricle.
* Once CSF is produced by the choroid plexus in the lateral ventricle, it travels to the third ventricle where more CSF is produced which then flows into the 4th ventricle (along the cerebral adequate).
* The 4th ventricle produces more CSF, when it leaves the ventricle through a small opening connected to the subarachnoid space, CSF travels round the CNS where it is reabsorbed into the blood supply by the arachnoid granulations.
36
compare the 3 layers of meningies:
1. Dura matter= the outer layer of a meninge that is thick, durable but stretchable. It is found in both the PNS and CNS.
2. Arachnoid membrane= web like, soft and spongy, lies beneath the dura matter. It is found in the CNS.
3. Pia Matter= closely attached to the brain and spinal cord and every surface around it. Smaller blood vessels are surrounded by it. It is found in both the PNS and CNS.
* Between the arachnoid membrane and the Pia matter is a space called the subarachnoid space which is filled with CFS (cerebrospinal fluid).
