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Neuroscience > Week 3: Supporting the brain > Flashcards

Week 3: Supporting the brain Flashcards

1
Q

The structure and function of cells that support the nervous system:

A

▪ Meninges
▪ Glia
▪ Ventricular system
▪ Cerebrospinal fluid
▪ Blood brain barrier

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2
Q

Meninges

A

Tough connective tissue covering the entire nervous system (supports & transfers CFS)

Dura mater
Arachnoid membrane
Pia mater
Subarachnoid space

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3
Q

Dura matter

A

Outer layer

thick, tough and flexible (but not stretchable)

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4
Q

Arachnoid membrane

A

middle layer, located between dura mater & pia mater – soft & spongy (stops CFS fluid leakage)

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5
Q

Pia matter

A

clings to surface of brain & spinal cord; thin & delicate, smaller surface blood vessels found here (also stops CFS leakage)

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6
Q

Subarachnoid space

A

Fluid-filled space between arachnoid membrane & pia mater - cushions brain - CFS flows

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7
Q

Meninges: CNS & PNS

A

CNS covered by 3 layers of meninges:
- Dura mater
- Arachnoid membrane
- Pia mater

PNS – two layers fuse:
- Dura and pia mater fuse
- Sheath protects spinal and cranial nerves and the autonomic ganglia
- (Arachnoid membrane (CSF) NOT present)

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7
Q

Ventricular system: Ventricles & CFS

A

Ventricles: hollow spaces within brain, filled with cerebrospinal fluid
(from the middle of the brain, to the spine)

▪ Interconnected

Filled with Cerebrospinal fluid (CSF): clear fluid (similar to blood plasma)

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8
Q

Four ventricles (names)

A
  • lateral ventricles
  • 3rd ventricle
  • cerebral aqueduct
  • 4th ventricle
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9
Q
  1. Lateral ventricles: where?
A

sited in centre of telencephalon – largest

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10
Q
  1. 3rd ventricle
A

sited at midline in centre of diencephalon

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11
Q
  1. Cerebral aqueduct
A

is a long tube in mesencephalon connects 3rd & 4th ventricles

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12
Q
  1. 4th ventricle
A

found between cerebellum & pons

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13
Q

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
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13
Q

Cerebrospinal Fluid

A

Produced constantly from choroid plexus (in lateral ventricles)

Consists of ions, water, protein, glucose

Total volume of CSF is ~125 ml

Takes 3 hrs for half CSF to be replaced (half-life - so half replaced in 3 hours).

(55% plasma, 45% RBCs, <1% WBCs and platelets)

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14
Q

The CSF has four vital functions:

A
  1. Protection
    1. Buoyancy (floats, support)
    2. Waste reduction/ removal
    3. Transport (of nutrients & hormones)
15
Q

Hydrocephalus (2 types)

A

▪ Accumulation of CSF within the cerebral ventricles (specifically cerebral aqueduct)

▪ Leads to ventricular dilatation (pressure)

▪ Classified into two types 
	* Obstructive hydrocephalus  * Communicating hydrocephalus
16
Q

Glia (4 types)

A

Support cells of the nervous system:

  • astrocytes
  • microglia
  • oligodenrocytes
  • schwann cells
17
Q

Astrocytes

A

Physical support – “neuron glue”
▪ Nourish neurons: wrap blood vessels to receive, store & release nutrients to neurons
▪ Help control chemical composition (homeostasis) of extracellular fluid
▪ Surround & ISOLATE synapse (limit NT dispersion)

Astrocytes & phagocytosis:
▪ Clean up debris (e.g., dead cells) in the brain
▪ special astrocytes move around CNS engulfing & digesting debris (phagocytosis)
▪ Form scar tissue in place of dead tissue

18
Q

Amyotrophic lateral sclerosis (ALS): Lou Gehrig’s disease

A

▪ Most common form of motor neuron disease (e.g. Stephen Hawkings)
▪ Rapidly progressive, leading to fatality
▪ Attacks nerve cells
▪ Lose all voluntary muscle control
* respiration
5,000 people affected at one time

19
Q

Astrocytes and memory

A
  • Recent discovery
    • Know important for homeostasis
    • May also be important for cognitive functions - like memory
    • Studied Einstein’s brain - only difference found was the number of astrocytes, he had more
    • EEG looks at oscillations - found astrocytes influenced the frequency of gamma oscillations with cognitive functions
      = Highlights importance of astrocytes
19
Q

Microglia

A

▪ Smallest glial cells
▪ Phagocytes function (engulf pathogens/ debris)
▪ Representative of immune system in brain
▪ Primarily responsible for inflammatory reaction in response to brain damage

▪ Thought to have role in:
	* Neurodegenerative disorders (Alzheimers & Parkinsons Disease) * Viral infections (HIV) (attack microglia = immune system affected)
20
Q

Oligodendrocytes and Schwann cells

A

▪ Schwann Cells (peripheral NS)
▪ Oligodendrocytes (central NS)

▪ Contain fatty tissue called myelin that wraps around neuron axons 
▪ Forms insulating coating: myelin sheath 

▪ Schwann cells - wrap individual axons (PNS)

▪ Oligodendrocyte - wrap several axons (CNS)

20
Q

What does new research suggest about glial cells?

A
  • Many types of glial cells
    HIV doesn’t affect neurones, it affects glial cells
21
Q

Why wasn’t glial cell communication discovered sooner?

A

Glial cells don’t use electrical communication so their function was missed by EEGs

22
Q

What kind of diseases could glial research help with?

A
  • Viral diseases
    Motor neural diseases
23
Q

Blood supply to the brain

A

Brain blood supply
▪ Brain receives 15-20% of body’s blood supply

▪ Nutrients & oxygen carried to brain by blood vessels

24
Q

Blood function

A
  1. Blood brings materials necessary for brain function
    • Oxygen
    • Nutrients (carbohydrate, amino acids, fats, vitamins)
    • Hormones (endocrine system - hormone effects last longer than nervous system)
  2. Blood removes materials from the brain (via ventricles)
    • Carbon dioxide
    • Lactate
    • Hormones (e.g. if too much adrenaline)
      * Ammonia
25
Q

Blood-brain barrier

A

Semi-permeable barrier between blood & Brain
* Some substances cross barrier & others can’t
(Maintain homeostasis for action potentials)
(Only CFS wanted around the brain, blood needs a barrier)

In brain, no spaces exist between endothelial cells & unwanted substances cannot pass over capillary wall - less permeable

26
Q

The BBB 3 vital functions:

A
  1. Protects brain from “foreign substances” in blood that may injure brain
    1. Protects brain from hormones & neurotransmitters in the rest of body
  2. Maintains a constant environment for the brain (homeostasis)
27
Q

Substances & BBB

A

▪ Lipid soluble molecules are able to penetrate through BBB relatively easily via lipid membranes of cells

▪ Water soluble molecules can only use specialised carrier-mediated transport mechanisms (Needs ATP)

▪ Active transport allows some substances to move across capillary walls (e.g., glucose transporters)

▪ Barrier is weaker in some areas (to detect toxins)

28
Q

What layer of the meninges is not present in the PNS?

A

Arachnoid membrane

28
Q

What type of cell is not located in CNS?

A

Schwann cell

29
Q

Reading: where does the CSF leave the brain?

A

Leaves through the 4th ventricle via small openings which connect with the subarachnoid space surrounding the brain

where it is then reabsorbed into the blood via arachnoid granulations

- The brain floats in the CFS contained within the subarachnoid space (reduces weight)

Neuroscience (22 decks)

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