neuroscience Exam 1 Flashcards
what is the fundamental neuronal process that underlies all aspects to brain function?
electrical signaling
what are dendrites?
branchlike extensions
receive info from other neurons
which way do afferent neurons travel?
away from body, toward CNS
which way do efferent neurons travel?
to body, away from CNS
what is an axon?
output unit of the cell
arises from axon hillock
has nodes of ranvier
what is a synapse?
sites of communication
presynaptic: finger like projections
synaptic cleft: space between neurons
postsynaptic:
what is axoplasmic transport?
mechanism that transports substances along an axon
anterograde: down first
retrograde: back up second
what does axonal transport appear slow?
aging
neurodegenerative diseases
how is information transmitted through a neuron?
synapse > dendrite > cell body > axon > synapse
what are bipolar neurons?
something on each end of cell body - dendritic root and axon
what are pseudounipolar cells?
peripheral and central axons
cell body is over on the side
what are multipolar cells?
have multiple dendrites arising from cell body
most common in body
what substances are higher in ECF?
sodium
chlorine
what substance is higher in ICF?
potassium
what are modality gated channels?
open in response to mechanical forces
what are ligand gated channels?
open in response to neurotransmitter binding
what are voltage gated channels?
open in response to changes in electrical potential
what are leak channels?
small number of ions leak at slow continuous rate
what is resting membrane potential?
value of electrical potential when at steady state
leak channels and Na+/K+ pump
what is the value on the inside of the neuron?
-70 to -90
what does the Na/K pump move?
2K in and 3Na out with each cycle
define depolarized
less negative than RMP
excitatory
define hyperpolarized
more neg than RMP
inhibitory
what is local potential?
at receiving sites
1-2mm - very small area
if stimulus is larger and longer, potential will be larger and longer lasting
temporal summation
changes occur within milliseconds
spatial summation
generated in different regions and added together
when is an action potential generated?
depolarizes beyond voltage threshold
all or nothing
longer distances
step to an action potential
RMP
depolarizing stim
voltage gated Na channels open
rapid Na entry depolarizes
Na close and K open
K moves from cell to ECF
K leaves cell and hyperpolarizes the cell
voltage gated K close
return to RMP
what is the refractory period?
channels become inactivated after opening AP
absolute: cannot be stimmed
relative: if greater depol current, can be stimmed
propagation of AP
increased diameter of axon increases speed
faster when thicker sheath
what are the functions of myelination?
insulation
prevents leakages
increases the speed
what are nodes of ranvier?
lack of myelin
high densities of Na and K channels
what is saltatory conduction?
quick node to node jumping
what are glia?
form a support network for neurons
describe astrocytes
star shaped
grey matter
role in cell signaling
maintain nutrition and blood supply of cell bodies
clean up debris
form scars
what are oligodendrites and schwann cells?
form myelin sheath
white matter
what is the difference between oligodendrites and schwann cells?
olig - CNS
schwann - PNS
what are microglial cells?
immune system of CNS
clean up and remove debris
what are glial stem cells?
immature and undifferentiated cells
can do whatever you need
what is neuroinflam mediated by?
reactive microglia and astrocytes
what are the beneficial effects of neuroinflam?
when reactive microglia clean up and remove debris
what are the harmful effects of neuroinflam?
excessive activation
death of neurons
correlation between abnormal glial activity and neurla damage in stroke
what does damaged myelination do?
slow and impede conduction of AP
what is multiple sclerosis?
damage to myelin sheath in brain and SC
autoimmune disorder
diagnosis is difficult
what are the S&S of MS?
lack of coordination and balance
impaired vision
double vision
impaired sensation
paresis/paralysis
speech difficulties
spasticity
increased reflexes
gait difficulties
what is the first symptom for 20% of MS pts?
visual symptoms
what is the symptom that 80% of MS pts have?
visual
double vision is most common
what is relapsing/remitting MS?
most common type
alternate between relapses/remissions
without treatment, most transition to secondary progressive
what is secondary progressive MS?
continuous decline with few or no relapses
what is primary progressive MS?
steady functional decline from time of onset
10%
what is progressive relapsing MS?
steady functional decline with relapse/partial remissions
function never fully recovers in remissions
5%
what is a synapse?
where a neuron and a post synaptic terminal meet
majority are chemical
where can synaptic communications between neurons ocur?
cell body - axosomatic
dendrites - axodendritic
axon - axoaxonic
sequence of events in synaptic transmission
transmitter synthesized and stored in vesicles
AP invades presyn terminal
depol of presyn terminal causes opening of Ca channels
influx of Ca through channels
Ca causes vesicles to fuse with presyn membrane
transmitter released into syn cleft via exocytosis
transmitter binds to recepter molecules in postsyn membrane
opening or closing of postsyn channels
postsyn current causes excitatory or inhibitory postsyn potential that changes the excitability of postsyn cell
removal of neurotransmitter by glial uptake or enzymatic degradation
retrieval of vesicular membrane from plasma membrane
transmitter is synthesized and then stored in vesicles
what opens the voltage gated ca channels?
depol of presyn membrane
what is needed for vesicle fusion and transmitter release?
influx of Ca
what are the different messages that depend on amount of neurotransmitter released?
reuptake of neurotransmitters
degradation of NT by enzymes
diffusion of NT
change in structure of membrane receptors
what happens if NT is not cleaned out?
overflow
stop binding
leads to MG
what potential happens from local depol?
excitatory postsynaptic potential
what potential happens form a local hyperpol?
inhibitory postsynaptic potential
when is AP triggered?
only if overall summation is sufficient to depol the cell to thresholdd
where is NT released?
synaptic cleft
where are neuromodulators released?
ECF
which NT/NM are excitatory?
ACh
glutamate
dopamine
norepi
substance P
nitric oxide
which NT/NM are inhibitory?
GABA
glycine
dopamine
histamine
norepi
endorphins
enkephalins
what is an agonist?
mimic effects naturally occuring NTs
what is an antogonist?
prevent the release of NT or bind to impede the effects
describe ACh
excitatory at all NMJ
initiation of skeletal muscle contraction
myasthenia gravis
botox inhibits ACh
parasympathetic
slows heart rate
increased smooth mus contractions
constriction of pupil
describe norepi
sympathetic
increase HR
dilation of bronchioles
control of mood
agonists are amphetamines and cocaine
excessive: fearful, panic disorder, PTSD
describe dopamine
pleasure
behaviors reinforcement
decision making
planning
parkinson’s: inadequate levels in caudate and puta
drugs for park can induce involuntary mvmts
describe serotonin
throughout gray matter
reg of sleep, appetite, arousal, mood
low levels associated with depression and anxiety
SRIs allow sero to stay in receptor longer
high levels asso with OCD and schizo
describe GABA
sedation
antianxiety
antiseizure
sleep inducing
benzos enhance GABA
epilepsy meds can decrease excessive neural activity
describe glutamate
learning and memory
excessive can cause seizures
too much destroys neurons
describe endorphins
inhibition of pain signaling
describe substance P
sensation of pain
released by nerve endings
res and CV control
mood reg
signals interpreted as pain
describe lambert-eaton syndrome
autoimmune
antibodies destroy voltage gate Ca channels
ACh cannot be released
decreased release of NT
describe myasthenia gravis
attack and destroy ACh receptors on muscle cells
there is still normal release of ACh
affect NMJ
males 60-70, females 20-30
what are the clinical features of MG?
repetitive use of muscles leads to increased weakness
usually affects eye movements (drooping)
facial expressions
proximal limb weakness
swallowing
difficulty speaking
weakness of breathing muscles
relieved with rest
WEAKNESS in regards to MG
weakness of neck, face, eyes, arms, legs
eyelid drooping (ptosis)
appearance (not a lot of expressions)
keep chocking and gagging while eating
no energy
extraocular muscle weakness, diplopia
slurred speech, hoarse voice
shortness of breath
treatment of MG
drugs that inhibit breakdown of ACh
removal of thymus gland
immunosuppressants
plasmapheresis
what is channelopathy?
dysfunction of ion channels
genetic mutation
can happen at any channel that affects AP
how is MS diagnosed?
it is difficult
usually manifests with one sign that can completely resolve
what gait disturbances are common in MS?
asymmetric step lengths
reduced speed
scissoring gait
ataxic gait
increased fall risk
fear of falling
decreased ability to dual-task
how is MS managed?
medication to modify the process or slow attacks
plasmapheresis
PT and OT
avoid high temps and stress
describe the somatic nervous system
voluntary, under conscious control
innervates skeletal muscle
consist of single motor neuron
describe autonomic nervous system
involuntary
controls and modulates functions primarily of visceral organs
consist of 2 neurons pathway: preganglionic and post
what does ans regulate?
homeostasis
circulation
respiration
digestion
metabolism
secretions
body temp
what are the efferents of the ANS?
sympathetic - fight or flight - thoracolumbar
parasympathetic - rest or digest - brainstem and sacrum
what do adrenergic neurons do?
release norepi
receptors for norepi are called adrenoreceptors
what do cholinergic neurons do?
release ACh
receptors for ACh are called cholinoreceptros
which neurons are cholinergic?
all preganglionic
some postganglionic
which neurons are adrenergic?
some postgang
what is the function and role of sympathetic nervous system?
mobilize body for activity
maintain blood supply to organs
fight or flight extremes of symp
increased arterial pressure
incr blood flow to active muscles
incr metabolic rate
incr blood glucose concentration
incr HR and contractility
incr mental activity and alertness
incr ventilation
decr GI motility: decr blood flow, peristalsis and secretions
what is the function of parasympathetic nervous system?
restorative, to conserve energy
where do pregang neurons arise?
CN 3, 7, 9, 10 or from S2-4
pupillary constriction and dilation
parasym stim of circular mus - contraction
sym stim of radial mus - dilation
para/sym in relation to near/far sight
para - focus near, round lens
sym - focus far, flat lens
what are mechanoreceptors?
respond to mechanical deformation
chemoreceptors
respond to chemicals released by cells
thermoreceptors
respond to heat/cold
nociceptors
sensitive to stimuli that damage to threaten damage
sensation of pain
describe receptive fields
area of skin innervation by single afferent neuron
small distally, larger proximally
test: two point touch, min distance that feel two points
1a and II axons
proprioception
muscle spindle
thickest mye
AB
touch
merkel, meissner, pacinian, ruffini cells
second thickest mye
Adelta
pain, temp
free nerve endings
thinnest mye
C axons
pain, temp, itch
free nerve endings
unmye
conscious relay pathways
location and type of stim
accurate details about stim and location
aware of it
divergent pathways
info from many locations in brainstem and cerebrum
both conscious and uncon
unconscious relay pathways
proprioceptive info
role in autonomic adjustments of mvmts and posture
first order neuron
has cell body in post root ganglion
conveys to medulla
second order neuron
fibers enter spinal cord to synapse with it
medulla to thalamus
third order neuron
synapses with it in thalamus
axons ascend to higher level
thalamus to cerebral cortex
DCML
touch
proprio
anterolateral/spinothalamic
pain
temp
crude touch
deep sensations
joint position sense
mvmt awareness
vibration
superficial sensations
pain
temp
light touch
pressure
combined cortical sensations
2 point discrimination
barognosis - weight discrimination
graphesthesia -
tactile localization
texture recognition
stereognosis
dorsal column sensations
discrim touch
proprio
vibration
2 point
bargonosis
graphesthesia
texture recog
sterognosis
fasciculus gracilis (medial)
axons from lower limb and lower trunk
cross in lower medulla
into lumbar spine
fasciculus cuneatus (lateral)
axons from upper limb and upper trunk
cross in lower medulla
into cervical spine
trigeminal lemniscus
from face directly to pons
cross in pons
anterolateral column axons transmit what?
pain (free nerve endings, nociceptors)
temp
crude touch
what are some different AL column pathways
spinothalamic - ant: crude touch, lat: pain and temp
spinolimbic - limbic lobe - emotions
spinoreticular - reticular formation
spinomesencephalic - midbrain
spinothalamic pathway: how many order neurons?
3 order neurons
primary: bring info to dorsal horn of SC
secondary: cross midline and project to thalamus
tertiary: from thalamus to cerebral cortex
what is crossed analgesia
once everything is crossed, contralateral effects
absence of pain in response to stimuli that normally would be painful
what is fast pain?
early perception of sharp pain
inital and immediate
A delta fibers
what is slow pain?
duller, bright quality
following sharp pain
dull throbbing, burning ache, not well localized
C fibers, unmye
describe the medial pain system
many responses to nociception
affective, motivation, arousal, withdrawl, autonomic
uses several pathways, not 3 order
cannot be accurately localized
spinomesencephalic tract
periaqueductal gray
superior colliculus
descending pain control system
turning eyes and head to source of noxious input
spinoreticular tract
ascending neurons
modulates arousal, attention, sleep-waking cycles
sever pain needs attention and interferes with sleep
spinolimbic tract
transmit slow pain into to medial and intralaminar nuclei in thalmus
axons project to anterior cingulate cortex, insula, amygdala
interferes with thinking, behavior, and social activities
unconscious relay tracts to cerebrum
info from proprio is transmitted to cerebrum via spinocerebellar tract
posterior spinocerebellar pathway - lower half of body
cuneocerebellar - upper half of body
anterior spinocerebellar - thorcolumbar SC
rostrospinocerebellar - cervical cord
info not consciously perceived
for uncon adjustments to mvmt and posture
considerations for sensory exam
“are there any areas of your skin where your feeling has changed or decreased?”
“does the skin on one side feel different than the other?”
explain the test you will do, show the pt what you will do, allow pt to feel the stimulation that will be applied
define the terms “sharp” and “dull”
vision should be eliminated
touch awareness and tactile localization
have pt tell you when and where they feel it
testing DCML
testing sharp/dull
tests lateral spinothalamic system
use paperclip
ask “is this sharp or dull”
temperature testing
warm water (40 C), cold water (10 C)
maintain contact with skin for 3 seconds before asking for a response
tactile threshold (pressure)
“say yes if you feel the touch”
apply filament at 90 deg with enough force to make it bend
WNL: 2.83 (5g force)
joint mvmt/position testing
“tell me whether i am moving/have positioned your joint up or down”
vibration testing
use tuning fork
“is it vibrating?”
can only be tested on bones
testing bilateral simultaneous touch
“tell me which side is being touched”
graphesthesia
“tell me what letter i draw on the palm of your hand”
testing DCML
sterognosis
“tell me what this is”
“you can move it around in your hand”
