1. Anat Flashcards
sections of the brain
Forebrain, Midbrain, Hindbrain
forebrain includes
Cerebrum, Diencephalon (thalamus and hypothalamus)
hindbrain includes
pons, medulla oblongata, cerebellum
brainstem includes
midbrain, pons, medulla oblongata
where is spinal cord located and protected by
located in vertebral column, protected by meninges surrounded by CSF
2 hemispheres of cerebrum separated by
longitudinal fissure
cerebral cortex is made up of
grey matter (cell body/soma), gyri and sulci
list the different lobes in the brain
frontal, parietal, temporal, occipital
what divides frontal lobe from parietal lobe
central sulcus
what divides temporal lobe from frontal/parietal lobe
lateral sulcus/fissure
what divides parietal lobe from occipital lobe
parieto-occipital sulcus
describe location of frontal lobe
anterior to central sulcus and superior to lateral sulcus/fissure
describe location of parietal lobe
posterior to central sulcus and superior to lateral sulcus/fissure
describe location of temporal lobe
inferior to lateral sulcus/fissure
describe location of occipital lobe
posterior to parietal-occipital sulcus and temporal lobe
what does the diencephalon contains
thalamus and hypothalamus
what does hypothalamus forms? (position)
lower part of the lateral wall and floor of third ventricle
what connects forebrain to hindbrain
midbrain
the neurons (clusters of nuclei) in the midbrain is a/w
visual and auditory pathways
does the midbrain contains fiber tracts?
yes (ascending and descending)
location of pons
inferior to midbrain, superior to medulla oblongata
does hindbrain contains fiber tracts
yes (ascending and descending) from the midbrain
most inferior part of the brain is the
medulla oblongata
nuclei in the medulla oblongata is a/w
cardiovascular and respiratory function (determine speed of HR and breathing rate)
where is the cerebellum located
posterior to pons and medulla oblongata
what divides the cerebellum?
vermis (midline portion) which is connected to the brainstem
the spinal cord is continuous with the brain at…
foramen magnum
(hindbrain -> foramen magnum -> spinal cord)
spinal cord tapers off at
conus medullaris
characteristics of neuronal cells
excitable (receive and generate signal) and conductive (transmit impulses)
types of cells in the brain
neurons and glial cells
function of neurons
structural and functional unit of nervous system, can generate/conduct impulses that are excitable
what are non-neuronal cells called
glial cells
function of glial cells
non conducting, support and protect neurons (eg repair, supply O2), 10x more glial then neurons
structure of a neuron
dendrite, cell body/soma, axon hillock, axon terminal
which part of the neuron contains nucleus, organelles, Golgi apparatus, mitochondria
soma
what does the dendrite not contain
short and highly branched, contain all cytoplasmic components except Golgi apparatus
function of dendrite spines
increase SA to increase innervations from other neurons (increase info received)
what does the axon cytoplasm/axoplasm contain?
lacks ribosomes, RER and Golgi apparatus → unable to synthesise new proteins or degrade old ones
where is AP generated?
axon hillock
how are materials transported in an axon?
materials must be transported back and forth btw cell body and axon terminal
fast vs slow component of transport
- fast component: transport cytoplasmic proteins and macromolecules (required for metabolic and synaptic activity)
- slow component: transport cytoskeletal components/ building blocks
anterograde transport
cell body to axon terminal
Retrograde transport
axon terminal to cell body
function of presynaptic neuron in signal transmission
- contains voltage-gated Ca2+ channels
- arrival of action potential at axon terminal → open voltage gated Ca2+ channels → influx of Ca2+ ions → triggers exocytosis of chemical NT into synaptic cleft
excitatory synapse (eg glutamate receptors) function
binding of NT (glutamate) to receptor → opening of Na+ channels in postsynaptic membrane → depolarisation of postsynaptic neuron → generate action potential
inhibitory synapse (eg GABA receptors) fucntion
binding of NT (GABA) to receptor → opening of K+ and Cl- channels in postsynaptic membrane → hyperpolarisation of postsynaptic neuron → no action potential generated
types of glial cells in CNS
astrocytes, oligodendrocytes, microglia
how is oligodendrocyte identified?
CNPase cell marker
function of oligodendrocyte
in white matter/axon: myelin sheath formation
in grey matter/soma: function as satellite cells (similar function to astrocytes)
how does oligodendrocyte form myelin sheath (different from Schwann cells)
1 oligodendrocyte form myelin sheath around portions of several axons
function of myelinated axons
myelinated axon helps to increase speed of transduction (signals jump between Node of Ranvier)
which glial cells is the largest in size
Astrocytes
characteristic of astrocyte
has pedicles (expanded end-feet) that terminate on capillaries or pia mater
types of astrocytes (and where are they found)
- fibrous astrocytes: located in white matter/ axons, long, few branches
- Protoplasmic astrocytes: located in grey matter/ soma, thick, lightly branched, close to neuron cell bodies
function of astrocytes (4)
- regulate composition of intercellular environment and entry of substances
- provide structural support to neurons and synapses
- Tripartite synapse (astrocytic process)
- mediate exchange of nutrients and metabolites (BBB)
describe process of tripartite synapse (astrocytic process)
astrocytes take up excess NT (glutamate) → metabolise glutamate → transport back to presynaptic neuron to be reused
(regulate homeostasis of glutamate)
function of microglia
- small phagocytic cells that enlarge and become mobile after injury to CNS
- monocyte origin (immune cells)
- are brain macrophages, immunocompetent cells, phagocytosis, APC (to MHCII)
- secrete pro-inflammatory mediators: TNF-a, IL-1ß
dysfunction of microglia can cause
diseases (Alzheimer’s disease, Parkinson disease, cerebral ischemia stroke)
what cells does PNS contains
neuron cells
glial cells (Schwann cells and satellite cells)
nerve endings
what are fascicles in PNS
contains nerve fibers (axons) → fascicles (bundles of nerve fibers) → nerve
what are the 3 connective tissues covering the fiber
- Endoneurium: connective tissue surrounding each individual nerve fiber
- Perineurium: connective tissue surrounding each fascicle
- Epineurium: connective tissue surrounding the entire nerve
what are the function of glial cells in PNS
Schwann cells - form myelin sheath around axons
Satellite cells/ amphicytes - support cells
how do Schwann cells form myelin sheath around axons
1 Schwann cell myelinate portions of a SINGLE axon (different from oligodendrocytes)
ganglia
collections of soma/ neuron cell bodies located outside of CNS
importance of circle of Willis
may help to supply blood to the opposite side in cases of SLOW OCCLUSION
- not effective if the occlusion is sudden
function of brain capillaries
have tight junctions → form BBB (prevent random entry of water soluble substances)
functions of CSF
- clear fluid that act as a liquid cushion to absorb shock waves from blows and falls
- helps to remove metabolites from brain (brain has no lymphatic vessels)
where is CSF produced
CSF produced by choroid plexus
flow of CSF
chloroid plexus in lateral ventricle → 3rd ventricle → via cerebral aqueduct to 4th ventricle → out of 4th ventricle to bathe whole brain & spinal cord
where is CSF absorbed
Absorbed/ removed by arachnoid granulations -> superior sagittal sinus
where is aneurysms usually formed?
circle of Willis -> cause hemorrhagic stroke
