Nervous System Flashcards
brain location, protection, and divisions
cranial cavity
skull and meninges
forebrain, midbrain, hindbrain
forebrain
hindbrain
brainstem
forebrain: cerebrum, diencephalon
hindbrain: medulla oblongata, pons, cerebellum
brainstem: midbrain, pons, medulla oblongata
how many pairs of cranial and spinal nerves
cranial: 12
spinal: 31
classifications of neurons by morphology
multipolar
bipolar
pseudounipolar
classifications of neurons by information flow
projection neurons: efferent and afferent
interneurons: local connections
classifications of neurons by effect
excitatory
inhibitory
why do materials have to be transported back and forth between the soma and terminus
axon lacks ribosomes, RER and Golgi
axon myelination in the CNS vs PNS
CNS: single oligodendrocyte creates many internodes on multiple axons
PNS: single Schwann cell creates one internode on an axon
internodes in both separated by Nodes of Ranvier
dendritic spines input and role
mostly glutamatergic
fundamental computational units of memory
effect of neurotransmitter binding at excitatory synapses
effect of neurotransmitter binding at inhibitory synapses
excitatory: opening of Na+ channels and depolarisation
inhibitory: opening of K+ or Cl- channels and hyperpolarisation
types of neuroglia and their functions
overview
oligodendrocytes: myelin sheath formation
astrocytes: BBB, structural support, secretion of growth factors, water transport
microglia: brain macrophages, secretion of proinflammatory cytokines, chemokines, APCs
fibrous vs protoplasmic astrocytes
fibrous: located primarily in white matter, long spindly processes with few branches
protoplasmic: located in grey matter, thick lightly branched processes, closely apposed to neuron somas
functions of astrocytes
regulate intercellular environment by potassium channels and entry of substances
structural support to neurons and synapses
metabolise neurotransmitters
mediate exchange of nutrients and metabolites between blood and neurons, glycogen and gluconeogenesis
forms a glial scar after CNS injury
tripartite synapse: wrap around synapse and eliminate excess glutamate
what happens if potassium is not cleared from intercellular environment
what happens neurotransmitters are not cleared after release
potassium: epileptic seizures
neurotransmitters: go into the extra synaptic spaces and activate neighbouring synapses
oligodendrocytes functions
in white matter: predominant glial cell, produce the myelin sheath
in grey matter: closely associated with neuron somas functioning as satellite cells
microglia functions
small phagocytic cells that enlarge and become mobile after injury
immunocompetent cells - APCs
secrete proinflammatory mediators
peripheral nerve structure
bundles (fascicles) of nerve fibres (axons) that are surrounded by myelin sheaths or Schwann cells
connective tissue elements in peripheral nerves
epineurium: connective tissue surrounding the entire nerve
perineurium: a layer of dense connective tissue around each fascicle of nerve
endoneurium: a thin reticular layer that surrounds each individual nerve fibre and contains Schwann cells
ganglia
encapsulated collections of neuron cell bodies located outside the CNS
contain satellite cells and connective tissue elements along with neurons
satellite cells
amphicytes
form a capsule of cells around neuron cell bodies located in the peripheral ganglia
cerebrum anatomy
largest part of the brain consisting of two cerebral hemispheres separated by the longitudinal fissure
cerebral cortex description
layer of grey matter on the surface of the hemispheres
gyri and sulci (raised and folds)
frontal lobe location
anterior to central sulcus and superior to lateral fissure
parietal lobe location
posterior to central sulcus and superior to lateral fissure
temporal lobe location
inferior to lateral fissure
occipital lobe location
posterior to parietal and temporal lobes (separated by parieto-occipital sulcus)
hippocampus anatomy
rolled in part of cerebral cortex
essential for the formation of new memories
particularly vulnerable to damage during global ischemia
affected early in Alzheimer’s
diencephalon anatomy
dorsal: thalamus
hypothalamus (separated by hypothalamic sulcus)
thalamus location
large mass of grey matter (nuclei) on either side of the third ventricle
hypothalamus location
forms the lower part of the lateral wall and floor of the third ventricle
midbrain location
connects forebrain to hindbrain
pons location
located inferior to midbrain
superior to medulla oblongata
medulla oblongata location
most inferior part of the brain
cerebellum location
located posterior to the pons and the medulla oblongata
consists of a midline portion (vermis) and two hemispheres
connected to brainstem
spinal cord
continuous with the brain at the foramen magnum of the skull
tapers off into the conus medullaris
consists of spinal nerves, grey matter and fibre tracts
role of hypothalamus
control and integrative centre for ANS
also receives input from other parts of the brain
influences the secretion of hormones from pit gland and discharges impulses down brainstem and spinal cord
types of tissue stimulated by ANS
cardiac muscle
smooth muscle
glands
vagus nerve
cranial nerve X
most of its fibres are parasympathetic
innervates all abdominal viscera up to colic flexure
also involved in swallowing breathing and larynx
full bladder nervous system response
parasympathetic reflex causes contraction for micturition
motor cortex of frontal lobe can supress bladder at S2 - 4 (voluntary and inhibitory)
deficiency at spinal cord or premotor cortex can result in loss of control
parasympathetic supply effect on external genitalia
increased blood flow into the cavernous spaces of penis and clitoris
erection / engorgement
two pairs of arteries that supply the brain
carotid arteries
vertebral arteries
vertebrobasilar arterial system
vertebral artery originates from subclavian artery
enters the skull the foramen magnum
branches supply the spinal cord, medulla and cerebellum
two vertebral arteries join to form midline basilar artery
branches supply pons, cerebellum and inner ear
ends by dividing into the two posterior cerebral arteries
branches supply midbrain, medial occipital lobe, base of temporal and occipital lobes
carotid arterial system
internal carotid artery originates from the common carotid artery in the neck
enter the skull through the carotid canals and is within the cavernous sinus
ends by diving into anterior and middle cerebral arteries
anterior cerebral artery passes into medial longitudinal fissure and back into parieto-occipital sulcus
supplies most of the medial surface except occipital lobe
middle cerebral artery passes laterally between temporal and frontal lobes
emerges at lateral fissure and supplies most of the lateral surface of the hemisphere
circle of Willis
anastomosis between left and right arteries supplying the brain
may help supply the opposite side in cases of slow occlusion on one side
superficial cerebral veins and venous sinuses
blood drains into sinuses which empty into internal jugular vein
superficial and superior brain drains into superior sagittal sinus
inferior brain drains into transverse sinus and superficial middle cerebral vein
deep cerebral veins
blood from the centre of the brain drains into deep cerebral veins
drains into the straight venous sinus
internal jugular vein
superficial and deep brain drain into venous sinuses and then into IJV
superior agittal and straight sinuses flow into transverse sinus
then sigmoid sinus which drains into IJV in the neck
drains to heart
