Signaling Flashcards
What are cations vs anions?
positive vs negative ions
What are the two types of diffusion gradients?
concentration gradient (move based on concentration), voltage gradient (move based on charge)
What is equilibrium potential?
when the concentration gradients equals the voltage gradient
What is the resting potential of a neuron?
the electrical charge across the cell membrane in the absence of stimulation (about -70mV on inside)
What particles help produce the resting potential? Where do they have a higher concentration?
Na+ and Cl- have a higher concentration outside the axon
K+ and A- (large proteins) have a higher concentration inside the axon
What three features contribute to the resting potential?
- membrane is mostly impermeable to large molecules the A- proteins will remain inside the cell
- ungated K+ and Cl- channels allow them to pass freely but gated Na+ channels keep them out
- Na+ - K+ pumps remove Na+ and take in K+
How much potassium is taken into cell through pump versus how much sodium is taken out?
2 K+ taken in and 3 Na+ sent out
What is an action potential?
a large, brief reversal in polarity of an axon
What is the threshold potential?
the level that the membrane potential must reach in order for an action potential to happen (-50-55mV)
How does an action potential happen?
Na+ enters the cell and K+ leaves the cell, this results in an action potential from the summed voltage changes
How can the voltage activated Na+ and K+ channels be blocked?
tea blocks K+ channels and ttx blocks sodium channels
Which voltage activated channel open faster? Which stay open longer?
sodium opens faster but potassium stays open longer
How many gates do sodium channels have?
2, one closes once the membrane depolarizes to +30mV
What does epsp vs ipsp stand for?
excitatory postsynaptic potential vs inhibitory postsynaptic potential
What channels are excitatory/inhibitory postsynaptic potentials usually associated with?
excitatory is w/sodium
inhibitory is w/potassium and chloride
How can EPSP and IPSP be summed?
temporal (rapid weak pulses from same place), spatial (signals from multiple presynaptic neurons being received by one postsynaptic neuron)
What do EPSP do?
brief depolarization of neuron membrane in response to stimulation, makes it more likely to produce an action potential
What do IPSP do?
brief hyperpolarization of neuron membrane in response to stimulation, less likely to produce action potential
What is saltatory conduction?
where nerve impulses move down a myelinated axon and excitement occurs only at the nodes of ranvier
What channels are responsible for the frequency of action potential?
sodium and potassium
What is the absolute refractory period?
the state an axon is in in the repolarizing period, new action potential cannot be made, sodium gate 2 is closed (not voltage activated)
What is the relative refractory period?
state of axon in the later phase of an action potential, a stronger electrical current is required to produce another action potential, potassium channels are still open
Do synapses use electrical or chemical signalling?
Usually chemical
What is storage granules?
stores synaptic vesicles in the presynaptic neuron
What are the 5 steps in anterograde synaptic transmission?
- synthesis of neurotransmitter
- packaging and storing at axon terminal
- transportation to presynaptic membrane and releasing into cleft
- bidning/activating receptors on postsynaptic membrane
- degradation/removal
What does anterograde synaptic transmission mean?
sending message forward using neurotransmitters
How are neurotransmitters made?
in axon terminal (building blocks from food are used)
in cell body (instructions from DNA, transported by microtubules)
What triggers neurotransmitters to be released?
at terminal, action potential opens the voltage gated calcium channels, Ca2+ enters the terminal and binds to calmodulin, the complex this makes causes some vesicles to empty into the synapse and others get ready to
What are the types of receptors that can be found on the post synaptic terminal?
transmitter-activated receptors, ionotropic receptors, metabotropic receptors, autoreceptor, quantum
What are the ways neurotransmitters are inactivated?
diffusion(drifts away from cleft), degradation(changes shape), reuptake(taken back into terminal that released), astrocyte uptake (astrocytes take up them)
What form of inactivation do SSRIs use?
reuptake (prevents it so there is more serotonin available)
What are some characteristics of excitatory synapses?
usually on dendrites, round vesicles, dense membrane material, wide cleft, and large active zone
What are some characteristics of inhibitory synapses?
usually on cell body, flat vesicles, sparse membrane material, narrow cleft, and small active zone
What makes up electrical synapses? (aka gap junction)
connexin proteins on adjacent cell membranes connect the two membranes to from hemichannels, this allows ions to pass between the neurons
What allows ions to pass through an electrical synapse?
hemichannels which are regulated gates
What are some advantages of electrical synapses?
can eliminate brief info flow delay, allow glial and neurons to exchange functions and selectivity for specific size molecules, allow for dual transmission (mixed synapse)
What is more common, chemical or electrical synapses? Which is faster?
chemical, electrical
What does acetylcholine do?
ACh is an inhibitory neurotransmitter that can slow the heart rate
What do epinephrine and norepinephrine do?
excitatory neurotransmitter, increases heart rate and is responsible for flight/fight
How can you tell if something is a neurotransmitter?
must be produced in neuron or be present in precursor molecule, when neuron is activated it must be released and illicit a response, applying chemical directly to cell should cause same response as it being naturally released, needs to be a way for cell to get rid of it
What can neurotransmitters do?
carry a message from one neuron to another by influencing voltage of the postsynaptic neuron, change structure of synapse, can send messages the opposite direction
What are the classes of neurotransmitters?
small molecule, peptide, lipid, gaseous, ion
What are some traits of small molecule transmitters? Examples?
quick acting, made in axon from nutrients, packaged and ready for use in axon terminal
acetylcholine, dopamine, serotonin, amine
How is acetylcholine made?
acetyl coa brings acetate to the synthesis site, ChAT transfers the acetate to choline, this makes ACh
How is acetylcholine broken down?
acetylcholinesterase (AChE) removes acetate from choline
What is the biochemical sequence of amine neurotransmitters?
precursor is tyrosine (tyrosine hydroxylase), which turns into L-dopa, then dopamine, then norepinephrine, then epinephrine
How is serotonin synthesized?
amino acid L-tyrptophan (found in pork, turkey, milk etc)
What are some amino acid transmitters and their function?
glutamate (open sodium and calcium channels and therefore excites neurons)
GABA (opens chloride channels and inhibits neurons)
How are peptide neurotransmitters made? (neuropeptide)
through the translation of mRNA, most are assembled on ribosomes, packaged by golgi, and transported by microtubules
What are some traits of neuropeptides?
act slowly and they are not replaced quickly
What are some examples of neuropeptides?
opiods, oxytocin, insulins, somatostatin, gastrins
What is an example of lipid transmitters?
endocannabinoids
What are phytocannabinoids vs endocannabinoids?
phyto is found in hemp plant (weed), endo is in the human body naturally
What are some traits of gaseous transmitters?
not stored in synaptic vesicles or released from them, made in cell as needed and easily cross the cell membrane
What are some examples of gaseous transmitters?
nitric oxide (NO), carbon monoxide (CO), hydrogen sulfide (H2S)
What are some traits of ion transmitters? Example?
actively transported, packaged into vesicles, and released (usually w/another transmitter ie glutamate)
Zinc (Zn2+)
What are the two main types of receptors?
ionotropic and metabotropic
What are ionotropic receptors?
has a binding site for a neurotransmitter and a pore that regulates ion flow, can directly and rpidly change the voltage of membrane
What are metabotropic receptors?
have a binding site for neurotransmitter but no pore, indirectly causes change in nearby ion channels or in metabolic activity
linked with a G protein that can affect other receptors or act with second messengers
What are second messengers?
bind to membrane bound channels, causing it to change its structure and altering ion flow through the membrane, can lead to forming new ion channels, can bind to sites on DNA to stop/start production of protein
What are cholinergic neurons?
neuron that uses ACh as its main neurotransmitter, excites skeletal muscles to start contractions (motor neurons)
What is the nicotinic Ach receptor?
when ACh or nicotine binds its pore opens and it depolarizes muscle fibers
What does the nicotinic receptor pore allow for?
simultaneous entry of na+ and exit of k+
What controls the sympathetic and parasympathetic divisions of the ANS?
acetylcholine neurons that spread out from the spinal cord
What are the four systems of the CNS?
cholinergic, dopaminergic, noradrenergic, sertonergic
What is the cholinergic system responsible for?
normal waking behaviour, attention and memory
What are the two pathways in the dopaminergic system? What do they do?
nigrostriatal (maintains normal motor behaviour, loss of dopamine is related to muslce tense and dyskinesia in parkinson)
mesolimbic (DA release causes repitition of behaviours, increase in DA means schizo, decrease is ADHD)
What is the noradrenergic system responsible for?
learning (sitmualtes neuron to change structure), may facilitate normal development of brain and organize movements, imbalences assocated with mania/depression
What does the sertonergic system do?
wakefulness and learning, imbalances are assocated with depression, schizo and OCD
How is hormone release controlled?
in response to sensory stimuli and cognitive activity the hypothalamus produces hormones that enter the pituitary gland, pituitary sends hormones to glands, glands then release their own hormones
How can hormones be used to treat or prevent diseases?
replacement therapy, synthetic hormones, counter aging effects, increase physical strength and endurance
Give examples of steroid, peptide, amino acid, and lipid hormones?
testosterone, cortisol
insulin, growth hormone, endorphin
melotonin, thyroxine
prostaglandin, thromboxones
What do homeostatic hormones do?
maintain internal metabolic balance and regulate phsyiolgoical systems
What do gonadal hormones do?
control reproductive functions are strongly influence sexual appearence as male/female
What do glucocorticoids do?
steroid hormones that are secreted in times of stress, important for carb/protein metabolism
What are anabolic-androgenic steroids?
synthetic hormone related to testosterone that have muscle building and masculizing effects
What are some approved uses of anabolic steroids? What are some risks?
testosterone replacement, muscle loss replacement, treat endometriosis and fibrocystic breast disease
can cause aggresion, male infertility, increased heart attack/stroke, damage kidney/liver
