Flashcards in CNS Deck (63):
how does the vertebrate CNS develop?
NEURULATION: folding of neural plate, allowing for formation of neural tube which will run down back and create spinal cord (dorsal nerve cord)
describe the evolutionary pattern in formation of spinal cord
consolidation of PNS (only possible with cephalization) --> nerves
ventral nerve cord --> dorsal nerve cord --> spinal cord --> increasing role of forebrain
three regions of brain neural tube
forebrain (procephalon), midbrain (mesencephalon), hindbrain (rhombocephalon)
what does the forebrain develop into?
cerebrum and diencephalon
what does the midbrain develop into?
midbrain remains as midbrain
what does hindbrain develop into?
medulla oblongata, cerebellum and pons
what are the methods of protection for CNS?
bony cage (skull, vertebrae), meninges, fluid between layers (CSF)
what are the meninges layers?
dura mater, arachnoid mater, pia mater in that order
how does arachnoid mater get its name?
cob-web like arrangement
where is fluid stored in the brain?
4 ventricles. 1&2 = lateral ventricles; 3 & 4 carries into a hollow central canal inside spinal cord
where does CSF originate?
3rd and 4th choroid plexus (inside the respective ventricles); they secrete 500mL CSF per day
what is the composition of CSF?
water, ions, vitamins, nutrients
what role does the choroid plexus play?
controls CSF composition
what are the extracellular fluids of the CNS?
interstitial fluid (surrounds neurons and glial cells), plasma (within cerebral blood vessels), CSF (within ventricular system, bathes external surfaces of the brain, between meninges)
compare CSF and plasma
lower [ion], [glucose], and pH; similar Na+; VERY LOW PROTEIN, NO BLOOD CELLS
why would one perform a lumbar puncture?
to check protein and blood levels inside of CSF; suggests meningitis
what cells make up the CSF? what are their function?
ependymal cells; creates barrier between compartments
what is the role of CSF?
clean out metabolite and toxins; does this by being removed and replaced often (4x/day)
what are the layers of brain involved in draining CSF?
subarachnoid space and dural sinus; CSF is absorbed into the venus dural sinus via arachnoid villi
what is the circulatory path of CSF?
lateral ventricles --> 3rd ventricles --> 4th ventricle --> central canal of spinal cord OR FLUSHED --> subarchnoid space -- (via arachnoid villi) --> superior sagittal sinus -- venus return to the heart
what are the special features of cerebral vasculature?
astrocyte foot processes - secrete paracrine factors that promote tight junctions, which allow for thin capillaries & prevent solute movement between cells
what crosses the blood-brain barrier easily? what does not?
lipid-soluble molecules (ethanol) cross easily; hydrophilic substances (ions, AAs, peptides, proteins) need transport mechanisms to cross the blood-brain barrier
how do drug-developers handle the blood-brain barrier?
make the drug the shape of their goal - ie if they want something to cross the blood barrier (like a drug to treat Parkinson's disease), make it the shape of an amino acid. if they don't want something to cross (like antihistamines), making it lipid-soluble
what are the metabolic properties of neural tissue?
oxygen-dependent (cannot fall back on fermentation the way muscles can) - therefore O2 readily cosses blood brain barrier; glucose-dependent (brain uses 50% of body's glucose requirement lmao); highly vascular bc it's dependent on O2 and glucose
what is hypoglycemia? what is the result of it?
low blood sugar; coma death
what is the role of spinal cord?
path of info flow from brain to muscles/joints/glands/skin
what are the divisions of the spinal cord? (from dorsal to ventral)
cervical, thoracic, lumbar, sacral
what's the major/most important nerve coming from the spinal cord?
where do parasympathetic nerves arise?
cranial + sacral
where do sympathetic nerves arise?
thoracic + lumbar
what nerves are associated with the dorsal root ganglion?
incoming = afferent
what nerves are associated with the ventral root ganglion?
outgoing = efferent
what's happening in the white matter?
mostly travel - this is travel of information to the brain AFTER integration of information; all about speed, so highly myelinated
what's happening in the grey matter? what types of nuclei are found in the grey matter?
synapses and integration of information; no myelin obviously; sensory and motor nuclei
what is happening in dorsal horn?
incoming somatic sensory nuclei (touch, pressure, pain); visceral sensory nuclei
what is happening in ventral horn?
somatic motor nuclei synapses
what is the brain stem? what nerves originate from it?
structures from mid and hindbrain; organised like spinal cord; most cranial nerves originate from brain stem - sensory and motor information for head and neck; vagus nerve(?);
what is the reticular formation? where would you find its nuclei?
diffuse network of neurons involving processes such as arousal/sleep, muscle tone, coordination of breathing, blood pressure, etc; find nuclei of it in the brain stem
what is happening in the lateral horn?
autonomic efferent nuclei
what are the ascending tracts?
dorsal columns (sacral/lumbar + thoracic/cervical) which respond to touch/pressure/pain; spinocerebellar tracts
which responds to proprioception = posture + coordination; spinothalmic which respond to pain+temp
what are the descending tracts?
lateral+ventromedial corticospinal tracts = voluntary movement
what is the path of a reflex?
stimulus --> sensory neurons --> interneurons --> command to muscles or gland --> response; spinal reflex initiates response without input from brain
where do cranial nerves originate from? what do they do?
brainstem; carry sensory and motor info for head/neck; cranial nerve X = vagus
what are the different brain stem structures? what are their functions?
midbrain = coordination of eye movement, visual and auditory senses; pons = relay station between cerebrum and cerebellum incl. regulating breathing; medulla = control of involuntary functions = BP, breathing, swallowing, vomiting + ascending somatosensory tracts + descending corticospinal tracts + site of crossing over for more neurons
what are the different functions of the medulla?
grey matter: control of involuntary functions (breathing, swallowing, vomiting)
white matter: asecnding somatosensory tracts + descending corticospinal tracts + site of crossing over (decussation) for most neurons in the corticospinal tract
2nd largest structure of brain (after cerebrum), coordinates movement
location of diencephalon? what are the different parts of it?
between brain stem and cerebrum; includes thamalamus, pineal gland, hypothalamus, and "pituitary gland"
relays and integrates information from the lower parts of the CNS, ears, eyes, motor info from cerebellum
tiny region of the brain but major centre for homeostasis; hunger, satiety, thirst, influences autonomic response, endocrine systems, regulates pituitary gland
secretes melatonin; involved in regulation of circadian rhythms
largest region of brain; site of higher brain function
four regions of cerebrum?
frontal, temporal, parietal, occipital
what are the grooves called in cerebrum? what are the "raised" areas called?
sulcus = grooves, gyrus = raised
what are the different regions of grey matter in cerebrum?
basal ganglia, limbic system, ceberal cortex
role of basal ganglia?
role of limbic system?
coordinates fear/emotion with higher cognitive functoins
what are the different functional areas of the cerebral cortex?
sensory areas (sensory input translation into perception), motor areas (control skeletal muscles), association areas (integrate information of sensory and motor areas)
where is primary motor area?
right next to central sulcus (aka precentral gyrus), it contains cell bodies of primary ascending motor neurons
where is the primary somatosensory cortex?
on ridges posterior to central sulcus = postcentral gyrus; terminals of ascending sensory pathways from skin, muscoskeletal system, viscera, info about touch/pressure/pain/temp/body postition
where are the special senses located?
each have their own devoted area + assocation area eg primary vision cortex and visual association area are in occipital lobe
what would a lot of fibres in the motor cortex mean?
fine movements, eg by hands/lips/tongue