The nervous system Flashcards by Adam Brass

What is the neuronal microenvironment composed of

Glia
Capillaries - blood supply
Other neurons
EXC space –> EXM (Collagen scaffold) and BECF (Interstitial fluid)

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What maintains the neuronal microenvioroment

Blood brain barrier

Cerebrospinal fluid

Neurons

Glial cells

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How was the blood brain barrier discovered

Intravenous injection of dyes which pass across leaky capillaries and stain soft tissues, no staining in the brain

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What is the function of the blood brain barrier

Protect neurons from fluctuation in concentrations of substances in the blood

(AA concentration, hormones, toxins ect)

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How is the BBB maintained

Tight junctions between endothelial cells (formed by astrocytes)

Thick basement membrane

Astrocytic endfeet

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What do astrocytes do

They have a regulatory role of brain functions that are implicated in neurogenesis and synaptogenesis, controlling blood–brain barrier permeability and maintaining extracellular homeostasis.

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How do important molecules get through the BBB

Facilitated transport (GLUT1)

Exchangers (Na-H)

Co transporters (Cl- transporters)

Increased numbers of mitochondria for active transport

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

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What are the leaky regions of the BBB

Choroid plexuses - ventricular system

Circumventricular organs

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What does the ventricular system do

Provides physical protection

Maintains appropriate levels of ions

Removes waste products

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How does CSF move?

Secreted by the choroid plexus

Circulates around the ventricles and central canal

Absorbed from the subarachnoid space to the venous blood system at the superior sagittal sinus

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How much CSF is secreted a day?

around 500mls

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What are ependymal cells

Specialised glial cells that line ventricles

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What is in the CSF

low AA and K

High Na

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What are the 3 types of meniges

Leptomeninges: Pia mater, Arachnoid mater

Dura matter

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What does the pia matter do

Covers surface of brain and blood vessels allowing for diffusion between CSF and BECF

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What does the arachnoid matter do

Cells linked by tight junctions preventing diffusion between CSF and plasma

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What does the dura matter do

Thick protective layer of the brain

Split into two layers to form intracranial sinuses

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How is the CSF absorbed

Evaginations of arachnoid membrane

Increased absorption with increased intracranial pressure

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What is exchanged between CSF and BECF

CSF to BECF
Macronutrients - glucose
Micronutrients - vitamins
Ions

BECF to CSF
Metabolic waste
Neurotransmitter

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Where does the exchange between CSF and BECF occur

From ventricles across ependymal cells

From subarachnoid space across pia mater

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What is hydrocephalus

When the CSF doesnt circulate properly, creating extra fluid The excess fluid puts pressure on the brain, which can damage it

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What happens during hydrocephalus

Dilation of ventricular system

Obstruction in ventricular system

Increased intracranial pressure

Loss of brain cells and brainstem reflexes

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What is the function of the CSF

Protects the sytem by acting like a cushion to protect the brain

Also removes waste products to help CNS work properly

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What is in the ventricular system

2 lateral ventricles
3rd ventricle
The cerebral aqueduct and the fourth ventricle

Structure that separates the lateral ventricles called the interventricular septum

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What does EAAT1 and EAAT2 do

Takes up glutamate into the astrocyte

What does EAAT3 do

Takes up glutamate into the presynaptic terminal of neurons

What do neurons and astrocytes do

Remove K+ and neurotransmitter from extracellular space

What does an increase in extracellular K+ do to astrocytes

Increases glucose metabolism Increased K+ uptake

Why do neurons have a more positive resting potential than glia

Neuronal membrane is more permeable to Na+ than astrocytic membranes Astrocytes have a higher K+ selectivity than neurons Astrocytes are more sensitive to extracellular K+ changes

What is a syncytium

a single cell or cytoplasmic mass containing several nuclei, formed by fusion of cells or by division of nuclei.

Why do astrocytes need the extra potassium

Spatial Buffering - Gap junctions for a syncytium of astrocytes, redistribute K+ to areas of decreased activity Also transports sugars, AA, cAMP and Ca2+

How does neurovascular coupling cause an increase in blood vessel diamete

Increased neuron firing rate --> increased Astrocyte Ca2+ --> increased release of vasoactive substances from astrocyte --> increased BV diameter (vasodilation) --> more glucose and AA to astrocytes

What does MRI create

3D images of the brain by using electromagnetic wave to disrupt hydrogen atom state

What does PET use

Glucose concentration in the brain

What does fMRI use

Oxygen use in the brain to identify active areas

What do neurons and astroyctes regulate

The BECF

What is the role of astroyctes

To act as a syncytium to buffer extracellular K+ Enabling neurovascular coupling

What are the components of the adult CNS

``` Forebrain Midbrain Hindbrain Brainstem - Midbrain, pons and medulla Spinal cord ```

What is the: endoderm, mesoderm and ectoderm

Endoderm - Lining of viscera Mesoderm - Bones and muscles Ectoderm - Skin and nervous system

What age does the neural plate form

17 days

What is neuralation

at 22 days the neural plate forms neural groove and folds --> CNS and ventricular system formed and the Neural crest (PNS)

What neurons could form from the neural crest

Any cells in the PNS

Why do women take folic acid when pregnant

``` Failure to close the neural tube which can cause Anencephaly (fatal) Spina bifida (Spinal chord doesnt form properly because meninges dont coordinate together ``` Folic acid lowers this defect by 90%

What are the 3 primary brain vesicles

Prosencephalon (forebrain) Mesencephalon (midbrain) Rhombencephalon (Hindbrain)

What are the 3 secondary brain vesicles of the forebrain

Telencephalic vesicles Diencephalon Optic vesicles

What are the optic vesicles

Optic stalk | Optic cup

What does the optic stalk and optic cup differentiate into

Optic stalk --> optic nerve | Optic cup --> retina

What does the diencephalon differentiate into

Thalamus and hypothalamus

What is the olfactory bulbs for

Smell

What is the white matter

Information transfer centre

Where is the cerebral aqueduct

Between tectum and tegmentum

What does the periaqueductal grey do

Controls pain

What is the substantia nigra and red nucleus used for

Motor control

What has more neurons the hindbrain or forebrain

Equal

What is ventral to the cerebellum

The pons

What do medullary pyramids do

Allow white matter to the spinal cord

How many hemispheres in the cerebellum

Why are there lots of folds in the cerebellum

To increase surface area | Folds called folia

What are grey matter areas in cerebellum known as

Deep cerebellum nuclei

What is the derivatives of the telencephalon (Forebrain)

Cerebral cortex and cerebral nuclei (amygdala, basal forebrain, basal ganglia) associated with the lateral ventricles

What is the derivatives of the diencephalon (Forebrain)

Thalamus, Hypothalamus and Retina Associated with the third ventricle

What is the derivatives of the mesencephalon (Midbrain)

Superior and inferior colliculi, red nucleus, substantia nigra Associated with the cerebral aqueduct

What is the derivative of the myelencephalon (Hindbrain)

Medulla oblongata Associated with the fourth ventricle

What are the derivatives of the metencephalon (Hindbrain)

Cerebellum and Pons Associated with fourth ventricle

What is the relationship between pons and cerebellum

The pons relays sensory information between the cerebrum and cerebellum

What does the mid brain do

motor movement, particularly movements of the eye, and in auditory and visual processing.

What is the cerebellum for

The cerebellum is important for making postural adjustments in order to maintain balance

What are the 3 types of cerebral cortex

Olfactory Neo cortex Hippocampus

Where is the hippocampus and what does it do

Found in each temporal lobe Involved in memory Only 3 layers

How many layers are in the neocortex

6 | Molecular, granular, pyramidal, internal granular, internal pyramidal and fusiform

Where in the brain is the only place neurons are formed in adult hood

Hippocampus

What are the four lobes of the neocortex

Frontal Parietal Occipital Temporal

What creates boundaries in the brain between lobes

Sulci and the gyri

What does the golgi stain stain

Single neurons

What doe stoluidine blue stain

Cell bodies (nissl stain)

What does Wiegert-PAL stain

Stains for myelin

What did Brodmann do

Stained the whole brain and mapped the function on a cytoarchitecture map

How did Brodmann work out which area correlated to which system

Use PET, fMRI and EEG scans and then stimulate and area and high glucose levels will light up

What is i the limbic lobe

The cortex of cingulate gyrus The cortex of medial aspect of temporal lobe Hippocampus

What can you see in the neocortex from a lateral view

Primary sensory Secondary sensory Motor areas Association areas

What does the insula do

Sensorimotor processing | Emotional regulation

What is found in the basal forebrain

Basal ganglia Amygdala

What is in the white matter

Commissural fibres which connect between hemispheres Projection fibres which link to non-cortical areas Association firbres which link areas within a hemisphere

What connects the two hemispheres, thus has large amounts of commissural fibres

Corpus callosum

What is the diencephalon

epithalamus, thalamus, subthalamus, and hypothalamus

What does the thalamus do

Connects to neocortex via projection fibres and acts as a relay station for the cerebral cortex

What does the hypothalamus do

Master regulator of homeostasis 11 major nuclei Links body to mind via ANS and pituitary

What is the name of the anterior pituitary

adenohypophysis

What is the name of the posterior pituitary

Neurohypothesis

What is the organisation of the ANS

Receptor --> preganglionic --> postganglionic --> effector cell

What input is in the dorsal horn

Sensory input

What is found in the lateral horn

Preganglionic sympathetic neurons

Where is the sympathetic chain ganglia located

From T1 - L3

What does the oculomotor nerve do

helps to adjust and coordinate eye position during movement.

Where does the vagus nerve originate

Medulla

What is the order of subdivisions in the spine

Cervical, Thoracic, Lumbar and sacral