2 - Cells and Signalling Flashcards
what are multi, bi, and unipolar neurons
m: one axon has many dendrites
b: one axon has one dendritic tree
u: one stalk from soma
define axoplasmic transport
active process (ATP) moving substances from one axon end to the other via microtubules
what directions are antereo and retrograde transport
antero: soma to terminal buttons
retro: vice versa
define glia
supporting cells of the CNS by surrounding neurons and holding them in place
functions of glia cell
destroy/remove dead neurons
insulate neurons from each other so signals don’t mix
nutrient control
what processes do astrocytes (macroglia) control
neuron structural support
produce chemicals needed by neurons
provide nutrients
what things do astrocytes regulate
oxygen, glucose sypply to neurons, phosphate ions
what cells are involved in phagocytosis
astrocytes as form scar tissue when dead tissue removed
roles of oligodendrocytes
support CNS axons by forming semi-rigid tissue between neurons, provide myelin sheath and nutrients
what do oligodendrocytes produce
processes: they wrap around axon segments to produce myelin
what cells act as macrophages
microglia to protect brain from debris and bacteria
what are the roles of microglia
primary inflammatory response
remodelling NS during development
secreting chemicals when glia and blood vessels form
roles of ependymal cells
form lining for ventricles and central canal of the spinal cord
secrete/circulate CSF
what are satellite glial cells sensitive to and associated with
injury-sensitive
assoc w neuropathological states like pain
how do satellite glial cells regulate extracellular chemical environments
protect, nourish, maintain neurons
where are satellite glia found
PNS’ sensory, sympathetic, and parasympathetic ganglia
how are Schwann cells different to oligodendrocytes when forming the myelin sheath
Schwann cell one axon each in PNS and whole cell surrounds axon
define blood-brain barrier
selectively permeable barrier between blood and brain produced by brain’s blood capillary wall cells
why can’t some substances pass through the brain-blood barrier
capillary fenestrations too small for some to pass through so food chemicals affecting composition can’t pass
what does the brain-blood barrier maintain
extracellular fluid composition to prevent message transmission in the brain from being disupted
what types of substances can pass through the barrier
small, lipid soluble, not highly charged
define action potential
electrical signal carrying message in axon from soma to axon terminals
when the brain is trying to initiate inhibition, to prevent reflexes for example, how does it work
IPSPs produced from inhibitory NTs released in synapse
resting potential
-70mV
threshold
-55mV
where is potassium normally
intracellular due to positive extracellular charge
where is chlorine usually
higher conc extracellular as intracellular is negatively charged
where is sodium usually
higher conc extraceullar so diffuses into the axon
what happens when the threshold is released and voltage-gated sodium ion channels open
influx of sodium ions inside the axon leading to depolarisation as +40mV reached
when do the VG K+ channels open
after Na+ diffuses in so K+ diffuses out
why do VGK+ ion channels let K+ leave the cell
electrostatic pressure is too positive intracellular and membrane potential has decreased
when do VGNa+ channels reset
when resting potential reached
why does hyperpolarisation occur
too much K+ diffused out so VGK close and NaK pump works
what does the NaK pump do
cause resting potential to be reached to remove 3 Na+ and allow in 2 K+
describe the rate law
strong stimulus means a high rate of firing and strong muscular contraction
define saltatory conduction
AP passes over nodes of Ranvier on myelinated axons and is faster as less diffusion
what two factors affect speed of action potential transmission
temperature and axon diameter (wider = less resistance)
define PSP
brief hyperpolarisations of depolarisations which increase or decrease a post-synaptic neuron’s rate of firing
how do axoaxonic alter the amount of neurotransmitters released by post-synaptic axons
presynaptic modulation, inhibition, and facilitation
what are ionotropic receptors
receptors allowing direct activation through a specific nt binding to the binding side of the nt-dependent ion channel to open it
what are metabotropic receptors’ role
using metabolic energy, a G protein is activated when the nt binds to the receptor, activating an enzyme producing a secondary messenger to open the ion channel by attaching to it
differences between ionotropic and metabotropic receptors
iono is fast, metabo is slow but amplifying
how do EPSPs cause depolarisation
open Na+ channels so Na enters increasing voltage
how do IPSPs work
K+ channels open so K+ leaves so intracellular is more negative
what happens if inhibitory neurotransmitters open Cl- ion channels
resting: nothing
depolarisation: Cl- goes in to return it to resting potential and counteract EPSPs
define neural integration
interaction of effects of exc/inhib neurons of a certain neuron
what happens when EPSPs are produced
transmit down dendrites across to axon hillock then axon fires if strong enough
what do autoreceptors on pre-synaptic neurons do
synthesising and releasing neurotransmitters, which can be inhibitory if over-producing or release more if not enough
define reuptake
axon terminal rapidly removing neurotransmitters from the synaptic cleft
3 forms of reuptake
enzymes, diffusion then taken up by other cells, pre-synaptic neuron reuptake channels to be reused
acetylcholine pathways and health links
pons, hippo, basal forebrain
AD, smoking, myasthenia
acetylcholine enzymes and receptors
ChAT (syn), AChE (bd)
iono (nicotinic)
metabo (muscarinic)
glutamate receptors
iono (NMDA, AMPA, kainate)
metabo (mGluR)
glutamate enzymes
glutaminase syn from glutamine
glutamine in astro brkdn to glutamine
glutamate health links
suicide
treats epilepsy, anxiety
anaesthetics
alcohol mediation
how can glutamate be blocked and what reduces it but increases GABA
ket blocks
lithium
what type of receptors are D1 like and D2 like
metabotropic
GABA enzymes
cyt glutamic acid decarboxylase syn from glutamine
brkdn same as glutamate
GABA receptors
iono (GABA A)
metabo (GABA B)
GABA health links
treats epilepsy, anxiety, mediates alcohol
suicide links
anaesthetic
dopamine synthesising enzymes
tyrosine hydroxase: L-DOPA from tyrosine
DOPA decarboxylase converts L-DOPA to dop
dopamine and noradrenaline breakdown enzymes
MAO
COMT
noradregergic pathways are where
locus coeruleus and project fibres around the cortex
noradrenaline synthesising enzymes do what after dopamine synthesis occurs
dopamine beta hydroxylase converts to it
noradrenaline and serotonin receptors
metabo
na has alpha and beta
5HT has many
serotonin pathways
raphe nuclei all over the brain
serotonin synthesis enzymes
typtophan converted to S-hydroxytryptophan by tryptophan hydroxylase to S-hydroxytryptomine by aromatic amino acid decarb
define drug effects
physiological changes observed in animals
define pharmokinetics
process of absorbing, distributing, metabolising, and excreting the drug
how can certain steps in the drug pathway be changed
give more chemicals needed to synthesise the nt
change enzyme effectiveness
alter metabolism
change amount released and removed
describe oral admin
tablets and pills absorbed by stomach before being broken down by enzymes and metabolised in the brain
describe intravenous
faster onset effect and gets to brain in a few seconds
describe tolerance
drugs no longer effective as body compensates disturbance to optimal levels
describe withdrawal symptoms
symptoms opposite to ones produced by drugs when taken repeatedly then suddenly stop
what may drugs inactivate and bind to
transporter molecules reuptaking
enzymes to change shape
describe phase I
small # of healthy volunteers use to work out tolerance, side effects, safety, determine range of doses for clinical effect and assess pharmacokinetics
describe phase II
small # with relevant condition to test tolerance, safety, and efficiency in double blind trial
describe phase III
same as phase II but w more patients to test against standard treatment and apply for human use licence if successful
describe phase IV
licence granted and large # of patients tested on for side effects, long term evaluation, and safety
define electrolyte
substance split into one positive and one negative end
how do anions and cations exert electrostatic pressure
a/c attracting each other
anions repelling
cations repelling
what is spina bifida
sac forming on the spine due to the neural tube doesn’t close
what types of spina bifida are there from least to most severe
occulta, meningocele, myelomeningocele
risk factors of spina bifida
obese mother, white, baby being female
where does the sac need to be to cause paralysis
top of the spine
if at bottom then incontinence and minor problems
