The nervous system Flashcards
What is the neuronal microenvironment composed of
Glia
Capillaries - blood supply
Other neurons
EXC space –> EXM (Collagen scaffold) and BECF (Interstitial fluid)
What maintains the neuronal microenvioroment
Blood brain barrier
Cerebrospinal fluid
Neurons
Glial cells
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
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)
How is the BBB maintained
Tight junctions between endothelial cells (formed by astrocytes)
Thick basement membrane
Astrocytic endfeet
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.
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
What are the leaky regions of the BBB
Choroid plexuses - ventricular system
Circumventricular organs
What does the ventricular system do
Provides physical protection
Maintains appropriate levels of ions
Removes waste products
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
How much CSF is secreted a day?
around 500mls
What are ependymal cells
Specialised glial cells that line ventricles
What is in the CSF
low AA and K
High Na
What are the 3 types of meniges
Leptomeninges: Pia mater, Arachnoid mater
Dura matter
What does the pia matter do
Covers surface of brain and blood vessels allowing for diffusion between CSF and BECF
What does the arachnoid matter do
Cells linked by tight junctions preventing diffusion between CSF and plasma
What does the dura matter do
Thick protective layer of the brain
Split into two layers to form intracranial sinuses
How is the CSF absorbed
Evaginations of arachnoid membrane
Increased absorption with increased intracranial pressure
What is exchanged between CSF and BECF
CSF to BECF
Macronutrients - glucose
Micronutrients - vitamins
Ions
BECF to CSF
Metabolic waste
Neurotransmitter
Where does the exchange between CSF and BECF occur
From ventricles across ependymal cells
From subarachnoid space across pia mater
What is hydrocephalus
When the CSF doesnt circulate properly, creating extra fluid The excess fluid puts pressure on the brain, which can damage it
What happens during hydrocephalus
Dilation of ventricular system
Obstruction in ventricular system
Increased intracranial pressure
Loss of brain cells and brainstem reflexes
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
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
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
2
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
