CNS 4b Flashcards
Neurons
communicative cell generates and transmits electrical/ chemical signals
-amitotic (don’t divide). extreme longevity, high metabolic rate (brain needs glucose)
astrocytes
attach to neurons and capillaries, monitor chemical environment of brain
microglia
immune cells of the brain, similar to mo (engulf and destroy pathogens)
oligodendrocytes
produce myelin sheath (called schwann cells in PNS)
Ependymal cells
produce CSF and line cavities (ventricles) of brain
Parts of neuron-dendrite
- receiving part filled with receptors
Cell body
-soma
nucleus: collection of cell bodies CNS
ganglion: collection of cell bodies in PNS
Axon
one long, from soma
Myelin
-insulates/protects axon
-speeds nerve conduction
-white matter____, gray matter____
myelinated, non-myelinated
sensory neurons
transmit impulses from peripheral sensory receptors to the CNS
sensory neurons transmitted
via afferent pathway
interneurons
transmit impulses from neuron to neuron
motor neurons
transmit pulses from CNS to an effector organ
via effernt pathway
sensory neuron types
-nociceptors (pain)
-mechanoreceptors (touch, pressure)
-thermoreceptors (temp)
-proprioceptors (location of bosy parts)
Neuronal communication- electrical
AP traveling down nerve axon
Action Potential generated by depolarization of cell membrane
Neuronal communication- chemical
neaurotransmitter release across synapse
in chemical communication, ___synaptic cell releases and ____synaptic cell receives (contains receptor for NT)
Pre, Post
Neurotransmitters
produced in neuron, held in vesicle until signaled to release
Effect of neurotransmitter determined by ____
action on postsynaptic neuron (excitary or inhibitory)
Excitatory
depolarizes cell; EPSPs (excitatory postsynaptic potentials)
Inhibitory
hyperpolarizes cell; inhibitory postsynaptic potentials (IPSPs)
Common neurotransmitters
NE, ACh, dopamine, histamine, endorphins,
major two:
gamma-aminobutyric acid (GABA): inhibitory
glutamate: excitatory
____can interfere with neurotransmitter production, storage, release, reception or metabolism
drugs
AGO drugs=
agonist (stimulating)
ANT drugs=
antagonist blocking
brain regions
-cerebrum
-dienchephalon: hypothalamus, thalamus, epithalamus
-brainstem: midbrain, pons, mnedulla oblongata
-cerebellum
Cerebral cortex
superficial 2-4mm layer of gray matter
Three functional areas of cerebral cortex
motor, sensory, association
each hemisphere concerned with ___side of body
contralateral (opposite)
lateralization
specialization of cortical function can occur in only one hemisphere
conscious behavior
involves entire cortex in one way or another
primary motor cortex
-allows conscious control of skeletal muscle movement
-all muscles can be mapped to area on primary motor cortex by a homunculus
-damage to this area (from stroke) paralyzes muscles
premotor cortex
-plans skille dmovement
-staging area for repetitious, patterned motor skills
Broca’s area
-present in onlt one hemisphere (usually left)
-motor speech area: directs muscles of speech production
Frontal eye field
controls volunatary eye movements
primary somatosensory cortex
-receives sensory info from skin, skeletal m,uscle, joints, tendons
-spatial discrimination: can identify body region being stimulated
-just like motor cortex, has representative homunculus showing contralateral sensory input from body
somatosensory association cortex
-integrates sensory input from primary somatosensory cortex for unerstanding objects
-determines size, texture of sensed objects
visual areas
-primary visual cortex receives visual stimuli- damage results in blindness
-visual association area interprets; damage allows individual to see but not comprehend what they see
auditory area
primary auditory cortex interprets info from inner ear (loudness, pitch, locatioon)
-auditory associate area: stores memories of sounds
Vestibular cortex
conscious awareness of balance
olfactory cortex
conscious awareness of odors
Gustatory cortex
perception of taste
Visceral sensory area
perception of visceral sensations
-ex: empty stomach, full bladder
anterior association area (prefrontal cortex)
most complicated cortical region
-involved in intellect, cognition, recall, personality
-allows us to plan, decide, make judgments, use reason
posterior association area
recognizing patterns, faces, localizing us in space
-damage here affects perception of own body
-individual fails to recognize limbs on side contralteral to damage (opposite)
-involved in understanding written and spoken lanuage (Wernicles area)
Limbic association area
part of limbic system
-provides emotional impact that makes a scens important to us and helps establish memories
cerebral white matter
association fibers, commissural fibers, projection fibers
basal nuclei
recives input from cerebral cortex
basal nuclei functions
regulate intensity of slow or sterotypes movements (swinging arms while walking)
-filter out incorrect/inappropiate respones
-inhibit antagonistic/unneccessary movements
_____and______are disorders of the basal nuclei
Parkinson’s disease and Huntingtons disease
regions of gray matter embedded deep in cerebrum
caudate nucleus, putamen, globus pallidus
thalamus
relays sensory impluses to cerebral cortex for interpretation
-involved in memory processing
-relays impulses btwn cerebral motor cortex and lower (subcortical) motor centers, inclugin cerbellum
Hypothalamus
cheif integration center of autonomic (involuntary) nervous syestem
regulates body temp, food intake, water balance, thirst, biological rythms
-regulates hormonal output of pituatry gland
-acts as an endocrine organ. producing ADH, oxytocin
limbic system
includes cerebral and diencephalon structures
-mediates emotional response
-memory processing
midbrain
contains visual and auditory reflex centers
contains nuclie for CN III and CN IV
subcortical motor centers
pons
relays info from cerebrum to cerebellum
-cooperates w/ medullary respiratory centers to control breathe rate and depth
contains nuclei of crainial nerve V-VII
projection fibers
Medulla oblongata
relays ascending sensory pathways impulses from skin and proprioceptors though nuclei cuneatus and gracilis
-relays sensory info to cerebellum
projection fibers
reticular formation
maintains cerbeal cortical alertness
-filters out repetitive stimuli
-helps regulate skeletal and virceral muscle activity
protective features of CNS
-bone: skull and vertebre
-meninges: protective membranes: pia mater, arachnoid mater, dura mater
-cerebrospinal fluid: bathes the brain, spinal cord
-blood-brain barrier: cells lining blood vessels in the brain
BBB
-lipid soluble substances pass through easily: O2, CO2, ethanol
-glucose redialy taken up
BBB protects brain from ______in the blood
pathogens, toxins, antibodies, pharmaceutical drugs
effect of constrained space
other tissues increase blood flow by vasodilation
brain has to _____blood flow bc it sits inside rigid, closed cranium
autoregulate
when capillaries in one area dilate_____
capillaries elsewhere must constrict
anything that increases blood flow will increase intracranial pressure (ICP):
bleeding
tumot
inflammation
increased ICP leads to
collapse of veins
decrease in effective CPP
reduces blood flow
nausea/ vomitting
changes in viosn
loss of consciousness
behavriol changes
Cushings triad
Cushings triad
irregular slow respiration, bradycardia, systolic htn
due to edeam and compression of brainstem
spinal cord
-long tract of nerves connecting the brain and body
-gray matter wrapped in white matter
-conducts somatic and autonomic reflexes
-transmits and modulates sensory and motor signals
Physcial trauma to CNS
localized (focal)- contusion, hematoma
spread out (diffuse)- concussion, diffuse axonal injury
-most likely causes are car accident, sports injuries , falls, blows to the head
direct force= primairy injury
brain in skill= secondary injury
Focal injuries
lacerations (scalp)
fractures (skull)
hematoma- pooling of blood outside of vessels: a contusion- is a type of hematoma. bleeding, edema, increased ICP. Hypoxia and necrosis are common, severty depends on impact energy
diffuse injuries: concussions
-widespread damage to brain tissue
-usually result of mechanical effects:
rapid acceleration/deceleration (whiplash), rotational (twisting or strasraining of neck)
-casues axonal injury and small vessel tears
-cognitive and behavriol impairment (severity depends on extent of damage)
molecular mechanism of neuronal injury
membrane depolarization from force of injury:
-Na and Ca channels open
-glutamate released –> excitotoxicity
mitochondrial dysfxn
-oxidative stress, ROS -> lipid peroxidation
inflammation
-BBB becomes leaky, WBC infiltration, microglia activation
-can occlude tiny cerebral vessels
-incr ICP decr CPP, ischemia–> promotes more damage
axonal injury
-mech forces stretch and tear axons-> distruption of signaling, confusion, disorientation, headache
energy mismatch
-ischemia–> decr glucose supply
-excess glucose useage to fuel Na/K/ATP pump to correct imbalances
changes in conciousnesness
-incr inhibitory signals in structures governeing sleep-wake
-disruption of reticular activating system that regulates arousal
tx for diffuse energy
-rest and restricted activity
-symptoms shoudl resolve once damage repaired
microglia engulf cell debris
microvessesl repaired
synaptic connection rearranged to regain fxn-Neuroplasticity
chronic traumatic encephalopathy (CTE)
-evidence that repeated head trauma causes perm changes: football players, hockey players, boxers
-diffuse neuronal death, atrophy: histologically disticnt from otgher types of neuodegen
personality and behavriol changes
infections of CNS
inflammation:
-leaky capillaries BB
-incr blood flow to area–> incr ICP
compression of structures-> changes in fxn
death of CNS tissue may be nevrotic
ex: meningitis, encephalitis, prion dx
Meningitis
inflammation of meninges covering brain or spinal cord: usually arachnoid layer: bacterial, fungal, viral
-systemic inflamm response: fever, trachycardia
-brain inflamm response: altered cognition (confusion, lethargy)
-dural nociceptors activated: headache, pain in the neck, back
-crainial nerves inflamm: impaired CN respones: light sensitivty
meningitis complications
vascular
-ischemic stroke: damages endothelium prone to thrombosis
-hemorrhagic stroke: weakened vessel walls rupture
fluid-based
-cerebral edema: incr perm of BBB from inflamm
-hydrocephalus: CSF accumulates due to blocked drainage
Encepalitis
inflammation of the brain (tissue)
-most common cause is herpes simplex, west niole, rabies, enteroviruses
-bacterial, fungal, parasitic, autoimmune
-immunocomprospised at higher risk
pathogen invasion: inflamm response
-wbc infiltration, complement activation, cytokine release
-edema, ince ICP, compressin damages brain tissue
Prion =
Prp= normal structural protein in the brain
diseased prions (PrPSC)=
Structurally abnormal and can make normal proteins abnormal through contact
Creutzfedlt-Jacob dx (CJD)
Prion dx
-sparodic: random structural change of protein(90%)
0hereditary: mutated gene produces unstable protein (autosom dom)
-acquired: introduced to body from external source (eat something with diseased prion)
prion disease effects
PrPSC aggregates in neurons
vacuoles from within cells
neurons overwhlemed and die
atrophy of brain regions responsible for s&S
-frontal lobe: subtle changes in memory, behavior-> rapid progression to dementia
-cerebellum: ataxia, startle myoclonus- jerks
-brainstem: coma, respiratory failure
dementia=
loss of cognitive fxn, memory, laungauge, problem solving, intereferes with independence
