IC1 Flashcards
number of cranial nerves and spinal nerves
12 vs 31 nerves
midbrain make what
neuromodulators eg dopamine, serotonin
regulate physiology
white matter vs grey matter in the cerebral cortex
grey matter: receive info, regulate outgoing info. usually cell bodies of the neurons
white matter: transmit signals to other regions. usually axons.
gyri and sulcus
grooves (folds and bumps) used to separate brain regions
nuclei of the midbrain associated with
visual and auditory pathways
medulla oblongata nuclei associated with
CV and respiratory function
which region of brain consists the most number of neurons
cerebellum (80%)
foramen magnum, conus medullaris
foramen magnum: opening in the occipital bone of the skull
conus medullaris: tapered, lower end of the spinal cord.
types of cells in the brain and their qty and function
neurons vs glial cells
neurons = structural and functional unit of the nervous system; conduct and generate impulses
glial cells = are non-conducting, support (transport o2, nutrients, waste products) and protect the neurons. IT HAS 10X THE NUMBER VS NEURONS
cell body of neuron and the associated organelles and structures
cell body of neuron is called the soma
contains nucleus, various cytoplasmic organelles, cytoskeletal elements (eg actin) and inclusions
golgi complex
organelles and structures in an axon
axon arise from the axon hillock in the cell body
cytoplasm (axoplasm) lacks ribosomes, RER, and golgi apparatus
= unable to synthesise new proteins or degrade old ones
= materials must be transported back and forth
fast and slow components of the axon
fast (50-400mm/day) = transports cytoplasmic proteins and macromolecules required for metabolic and synaptic activity
slow (1-4mm/day) = transports cytoskeletal components
anterograde and retrograde transport in axon
forward (cell body to axon terminal)
vs
backwards (from axon terminal to cell body) = for movement of waste materials, carried to cell body for degradation.
what does the dendrite contain
all cytoplasmic components found in the cell body except the golgi apparatus
what does the plasmalemma contain?
voltage gated ca2+ channels
length of the synaptic cleft?
20-40nm wide space between the pre and post synaptic membrane.
difference between excitatory vs inhibitory synapse in movement of ions
EXCITATORY: binding of neurotransmitter leads to opening of Na+ channels = depolarisation
eg binding of glutamate to AMPAR and NMDAR receptors
INHIBITORY:
binding of neurotransmitter leads to opening of K+ and Cl- channels = hyperpolarisation
eg binding of GABA to GABA-A receptors
types of glial cells
astrocytes
oligodendrocytes
microglia
percentage, shape, function of astrocytes (and type)
25%
largest of neuroglial cells
have numerous processes with expanded end feet (pedicles) terminating on capillaries or on the pia mater. *(blood brain barrier)
fibrous: found in white matter. long, spindly processes with few branches
protoplasmic: found in grey matter. thick, lightly branched process. closely apposed to neuron cell bodies
FUNCTION:
- regulate the composition of the intercellular environment and the entry of substances into it (water transport, excess transport = cerebral edema)
- secretion of nerve growth factors.
- structural support to neurons and synapses
- metabolism of neurotransmitters (glutamate-glutamine shuttle) (tripartite system) (takes up excess neurotransmitter from NMJ, metabolism and recycles it for pre-synaptic transmitter > transported back)
- mediate the exchange of nutrients and metabolites between blood and neurons. pedicles can expand or narrow blood vessels.
- scar formation caused by astrocytes
percentage, shape, function of oligodendrocytes
60-80%
in white matter: predominant neuroglial cell type
- produce myelinated fibres (ONLY IN THE CNS)
gray matter: function as satellite cells for neuron cell bodies.
OTHERS:
express Nogo-A (myelin associated neurite-outgrowth inhibitor)
percentage, shape, function of microglia
5-10%
enlarge and become mobile after injury to the CNS.
- antigen presentation
- immunocompetent cells
- brain macrophages, phagocytosis
- secrete proinflammatory cytokines, chemokines,
what cell marker used to identify oligdendrocytes
CNPase
role of Nogo-A
inhibition of axonal regeneration following injury and ischemia in the CNS. = antibodies to nogo-A may help with neurodegenerative recovery
implication of microglia in disease
may be implicated in Alzeimers, parkinsons, cerebral ischemia
composition of PNS?
neuron processes
neuroglia cells (Schwann cells, satellite cells)
structure of PNS?
bundles (fascicles) of nerve fibres (axons) surrounded by myelin sheaths or schwann cells
around the nerve: endoneurium
(thin reticular layer, consist of Schwann cells)
around the fascicle: perineurium (dense connective tissue)
around the entire merve: epineurium (connective tissue)
difference between oligodendrocytes and schwann cells in formation of myelin sheath
oligodendrocyte form myelin sheath around portions of several axons
schwann cells form myelin sheath on ONLY ONE axon.
it also spins around the nerve axon
what is peripheral ganglion?
ganglia are encapsulated collection of neuron cell bodies located outside CNS
contain satellite cells (forms a capsule of cells around the neuron cell bodies) and connective tissue elements along with neurons
basilar artery (originate, supply)
two verterbal artery = join to form the basilar artery
branch and supply to pons, cerebellum, and inner ear.
vertebral artery (originate, supply)
from the subclavian artery in neck
enter skull through the foramen magnum
supply blood to spinal cord, medulla, and cerebellum.
posterior cerebral arteries
basilar artery divides into posterior cerebral arteries
supply to the midbrain, medial aspect of the occipital lobe, base of the temporal and occipital lobe.
internal carotid arteries (originate, supply, divides into…)
from the common carotid artery
enters skull through carotid canals
situated within the cavernous sinus
divides into anterior cerebral and middle cerebral
anterior cerebral passes through medial longitudinal fissue and sweeps back to the parieto-occipital sulcus
- supplies medial surface of hemisphere except medial aspect of the occipital lobe.
middle cerebral passes through the lateral fissue and supplies most of the lateral surface of the hemisphere (frontal, parietal, temporal, occipital)
circle of willis
May help to supply blood to the opposite side, in cases of slow occlusion of an artery on one side [the communicating arteries have time to enlarge, to accommodate the increased blood flow].
joined together by posterior and anterior communicating
brain cardiac output
uses 15-20% of the TOTAL cardiac output despite only being 2% of total body weight
subdural haemorrhage
rupture of cerebral vein as it drains into the superior sagittal sinus = slow seepage (venous pressure is low) = expanding hematoma presses on the brain = dizzy, headache, apathy, confusion, falling, drwosiness.
subdural hemorrhage
where does blood from the brain drain out of?
SUPERFICIAL ASPECT: superior sagittal sinus > transverse sinus > sigmoid sinus
INFERIOR part of brain: transverse sinus AND superficial middle cerebral vein
- superficial middle cerebral vein > cavernous sinus
CENTRE: deep cerebral veins > venous sinus > transverse sinus > sigmoid sinus
OVERALL: internal jugular vein
CSF properties
Cerebrospinal fluid (CSF) is a clear fluid that acts as a protective “liquid cushion” around the brain and spinal cord by absorbing shock waves from blows and falls.
- also helps to remove metabolites from the brain since there are no lymphatic channels.
CSF production and movement
- produced by choroid plexus in the cerebral ventricles
> 3rd ventricle (via cerebral aqueduct)
> 4th ventricle > bathe the entire brain and spinal cord.
absorbed into superior sagittal sinus by arachnoid granulations
