anatomy Flashcards
tldr components of brain
1) forebrain
2) midbrain
3) hind brain
4) brain stem
components of forebrain
1) cerebrum
2) diencephalon
cerebrum
- largest part
- 2 cerebral hemisphere
** separated by longitudinal fissure
** covered by cerebral cortex (Grey matter)
** gryus: top fold (N shape)
** sulcus (fissure): bottom fold (U shape) - divided into 4 main lobes
1) frontal lobe: anterior to central sulcus, superior to lateral fissure
2) parietal lobe: posterior to central sulcus, superior to lateral fissure
3) temporal lobe: inferior to lateral fissures, regulate memories, compute time & distance & convos & memory
4) occipital lobe: posterior to parietal & temporal lobes, separated by parieto-occipital sulcus
diencephalon
hypothalamus
- lower part of lateral wall and floor of third ventricles
midbrain
- connect forebrain to hindbrain
- cranial nerves: III, IV
- nuclei associated with: III, IV, V, visual & auditory pathway
- fibre tract: ascending & descending pathway
hindbrain
- medulla oblongata
- pons
** inferior to midbrain, superior to medulla oblongata
** cranial nerves: V, VI, VII, VIII
** nuclei associated with: V, VI, VII, VIII
** fibre tracts: ascending & descending fibres - cerebellum
** located posterior to pons and medulla oblongata
** midline portion (Vermis) And 2 hemisphere
** connected to brain stem
brain stem
- midbrain, pons
- medulla oblongata
** most inferior portion of brain
** cranial nerves: IX, X, XI, XII
** nuclei associated with: V, IX, X, XI, XII, cardiovascular and respiratory function
** fibre tracts: Ascending and descending tracts
neuronal general
- structural and functional unit of nervous system
- generate/conduct impulses
- excitable
tldr structure of neurons
1) cell body - soma
2) axon
3) dendrite
4) synapse
cell body - soma
- nucleus, various cytoplasmic organelles, cytoskeletal elements, inclusions
- golgi apparatus (near nucleus) , mitochondria throughout cytoplasm
axons
- nerve fibres that conduct impulses away from cell body
- long slender processes that arise from axon hillock in cell body
- branch at distal (terminal end)
- cytoplasm lack ribosome, RER, golgi apparatus
- transport components
** fast: cytoplasmic protein & macromolecules required for metabolic and synaptic activity
** slow: cytoskeletal component down axon
dendrite
- conduct impulses towards cell body
- short and highly branched
- cytoplasmic component except golgi apparatus
- covered w dendritic synpases
general non-neuronal cells (glial cells)
- non conducting
- support and protect neurons
- 10x number of neurons
tldr types of non-neuronal cells (Glial cells)
1) oligodendrocytes
2) astrocytes
3) microglia
oligodendrocytes
1) white matter: myelin sheath formation
2) gray matter: function as satellite cells
3) cell markers - CNPase
4) express Nogo-A: myeline associated neurite-outgrowth inhibitor, inhibit axonal regeneration following injury & ischemia in CNS
5) CNS vs PNS
- CNS: oligodendrocytes myelinate portions of several axons
- PNS: 1 Schwann cell myelinate portions of 1 axon
types of astrocytes
1) fibrous
- in white matter
- long, spindly processes with few branches
2) protoplasmic
- in grey matter
- thick, lightly branched processes
- closely apposed to neuron cell bodies
astrocytes function
1) end feet
- regulate blood flow into brain
- expand and contract blood vessels
2) regulate homeostasis of neurotransmitters (glutamate) at synapses
3) regulate composition of intracellular environment and entry of substances into it
- express lot of K channel
- astrocytes clear excess K accumulation
- activate neurons -> release K -> increase local extracellular composition
4) metabolise neurotransmitter
- glutamate glutamine shuttle
- prevent activating neighbouring synapses
5) mediate exchange of nutrients and metabolites between blood and neurons
- contain glycogen, can carry out gluconeogenesis
- astrocytic processes can wrap around this synapse -> glutamate transports/uptakers -> eliminate excess glutamate from synaptic cleft
6) tripartite synapase
- astrocyte processes wrap around synapse -> glutamate transports/uptakers -> eliminate excess glutamate from synaptic cleft
microglia
- brain macrophages, phagocytosis
- secretion of pro-inflammatory cytokines, chemokines
- antigen presentation function (MHCII)
- CNS immunocompetent cells
- small phagocytic cells that enlarge and become mobile after injury to CNS
- originate from peripheral monocytic precursor cells
spinal cord
- located in vertebral column
- protected by meninges
- surrounded by CSF
- continuous w brain at foramen magnum of skull
- taper off into conus medullaris
categories of nerves in PNS
1) Cranial (12 pairs): come out from brain
2) spinal (31 pairs): come out from spine
composition of PNS
1) neuron processes and cell bodies outside CNS
2) neurological cells (Schwann cells, satellite cells)
structure of PNS
1) bundles (Fascicles) of nerve fibres (axons) surrounded by myelin sheath
2) Schwann cells invested within 3 connective tissues
- epineurium: connective tissue surrounding entire nerve
- perineurium: layer of dense connective tissue around each fascicle of nerve fibre
- endoneurium: thin, reticular layer that surround each individual nerve fibre, contain Schwann cells
3) myeline sheath
- Schwann cells around myelinated axon
4) peripheral ganglion
- encapsulated, outside CNS
- contain satellite cells, connective tissue elements, neurons
5) satellite cells
- amphicytes
- form capsule of cells around neuron cell bodies
carotid arterial system
through internal carotid artery
- originate from common carotid artery in neck
- enter skull through carotid canals
- situated within cavernous sinus end by dividing into
1) anterior cerebral artery
** pass forward into medial longitudinal fissure
** sweep back to parieto-occipital sulcus
** supplies most of medial surface of hemisphere except medial aspect of occipital lobe
2) middle cerebral artery
** pass laterally between temporal and frontal lobes
** emerge at lateral fissure
** fans out to supply most of lateral surface of hemisphere (frontal, parietal, temporal, occipital)
vertebral artery
1) originate from subclavian artery in neck
2) enter skull through foramen magnum (hole at base of skull)
3) branch out -> supply spinal cord, medulla oblongata, cerebellum
- anterior spinal artery, posterior spinal artery, posterior inferior cerebellar artery
4) 2 vertebral arteries -> basilar arteries (midline)
- basilar branch to supply pons, cerebellum, inner ear
** anterior inferior cerebellar artery
** pontine branches
** labryinthine artery
** superior cerebellar artery: supply midbrain, medial aspect of occipital lobe, base of temporal and occipital lobes - basilar divide into 2 posterior cerebral arteries
circle of willis
- arterial ring at base of brain
- anastomosis (Connection) between left and right arteries supplying brain
** anterior communicating artery: anterior cerebral arteries of both sides
** posterior communicating artery: middle cerebral artery -> posterior cerebral artery - benefits
** collateral circulation: supply blood to both side in case of slow occlusion in the other, not effective if sudden occlusion
** communicating arteries have time to enlarge -> accommodate increase blood flow
venous drainage
1) superficial cerebral veins & venous sinuses
- brain -> venous sinuses -> internal jugular vein
- superficial part of superior aspect -> superior sagittal sinus
- inferior part of brain -> transverse sinus and superficial middle cerebral vein
- superficial middle cerebral vein -> cavernous sinus
2) cavernous sinus
- closely related to cranial nerves (III, IV, V, VI) and part of internal carotid artery
3) deep cerebral veins
- centre of brain -> deep cerebral veins -> venous sinus (straight sinus)
4) internal jugular vein
- superficial and deep part of brain -> venous sinuses -> internal jugular vein and heart
- superior saggital and straight sinus -> transverse sinus -> sigmoid sinus -> internal jugular vein of neck
capillaries
- tight junctions between endothelial cells -> blood brain barrier
cerebrospinal fluid (CSF)
- protective cushion around brain and spinal cord
- help remove metabolites from brain
- produced by choroid plexus in cerebral ventricles
- flow from lateral ventricle to 3rd ventricle -. 4th ventricle via cerebral aqueduct -> bathe whole brain and spinal cord
- absorbed into superior sagittal sinus by arachnoid granulations
