NEURONAL COMMUNICATION Flashcards
what is a sensory receptor and where are they found?
detect changes in the surrounding and are energy TRANSDUCERS
found on our senses (skin, eyes, tongue, ears)
what is meant by the term “TRANSDUCERS”
conversion of energy from one form to another
define nerve impulses
electrical response created by sensory receptors
what type of sensor is PACINIAN CORPUSCLE?
pressure sensor, detect changes in pressure
list types of sensory receptors:
light sensor
temperature sensor
pressure sensor
vibration sensor
olfactory sensor
what type of channel do nervous cells have?
sodium and potassium channels
how is an inactive cell at resting state defined?
polarised since negatively charged inside
what is meant by resting potential
when voltage inside is -70 mV meaning that more K+ and Na+ are outside than inside
the potential difference across the membrane when the neuron is at rest.
how is resting potential maintained?
by the active sodium-potassium pump that ACTIVELY PUMPS OUT 3 NA+ AND 2 K+ IN
POLARISED
when cell is inactive and is negatively charged inside compared to outside
DEPOLARISATION
the proces through which the inside of the cell becomes less negative compared to the outside
what is an action potential?
the increase in voltage beyond the resting potential
what is required for the creation of an active potential?
a big enough stimulus –> enough opening of Na+ –> enough entrance of Na+. –> change in potential difference –> depolarization
needs to reach a threshold
why does the increase in voltage occur?
due to the membrane becoming more permeable to Na+
describe process of active potential
- stimulus which causes an increase of voltage beyond -60 (-55 mV)
- Depolarization begins (more Na+ gate opens and more Na ions enter)
- when enough Na+ entered –> action potential is reached
- Action potential is when the voltage reaches 40 mV , is the peak so Na+ gate shut.
5.Repolarization begins –> K+ gate opens and fload out
6.repolarization continues until going below the resting potential —> REFRACTORY PERIOD (overshoot of K ions)
- goes back to resting potential
what is the refractory period and why is it important?
just after the action potential.
it occurs for a short period of time it allows the cell to recover after an action potential
it ensures that an action potential is transmitted in one direction
allows the axon to remain unresponsive during hyperpolarisation
how does the refractory period prevent the action potential from flowing backward?
refractory period will cause the part of the axon that just generated an action potential to become UNRESPONSIVE, the traveling action potential cannot generate another action potential in the retrograde direction, because the only excitable region available is in the anterograde direction to the terminal
how is the resting potential maintained?
3 Na+ leaving for every 2 K+ moving in since the membrane is more permeable to K+
through voltage-gated channels sodium-potassium pump
what does the leaving and entering of Na+ and K+ create?
an electrochemical gradient
does the electrochemical gradient balance out?explain your answer
no, because the membrane is more permeable to K+
what happens when Na+ enter the neuron?
creates LOCAL CURRENTS
what does local currents cause?
depolarization and more Na+ channels to open
how do local currents form?
- A.P causes Na+ channels to open
- Na+ moves in and diffuse down concentration gradient
- Na+ diffuse SIDEWAYS ALONG NEURON
- channels open even more –> RAPID INFLUX –> full depolarization
in myelinated neurons there are ELONGATED LOCAL CURRENTS WHICH SPEEDS UP THE CONDUCTION
why doesnt the local current reverse?
because the concentration of Na+ is high behind, and Na+ moves from high to low.
what is saltatory conduction?
transmission of action potential by jumping from one node of ranvier to another
what is an advantage of saltatory conduction?
A.P travels faster, and doesnt have to generate an A.P along the whole axon but only in the nodes
what is a synapse/synaptic cleft?
is the gap/junction between 2 neurons
allows convergent to one singe neurone
divergence to multiple neurons
amplification lower level stimuli
how is it called when synapse use acetylcholine as neurotransmitter?
CHOLINERGIC SYNAPSES
what do pre-synaptic bulb have?
mitochondria
SER
synaptic vesicles
Calcium ions channels
what do post-synaptic membrane have?
LINGAND-GATED Na+ channels with complementary receptor to acetylcholine
describe transmission process:
- AP arrives at pre-synaptic bulb
2.Calcium channels open
3.Calcium ions fload INTO synaptic bulb
4.calcium ions causes synaptic vesicles to MOVE and FUSE with pre-synaptic membrane
- acetylcholine released by exocytosis –> bind to receptors on Na+ channels –> open
what happens to acetylcholine afterwards?
hydrolised by ACETYLCHOLINESTERASE into ETHANOIC ACID and CHOLINE which are recycled
what is meant by summation?
the effect of many neurotransmitters (EPSPs) combined to generate a action potential
how many types of summation?
temporal and spatial summation
define temporal summation
when several action potential move into 1 post synaptic neuron
Define spatial summation
When many pre synaptic neurons converge and release their action potential in 1 post synaptic neuron
Can EPSPs be affected by something?
yes, IPSPs can prevent EPSPs to cause an action potential
how can an action potential be trasnmitted to several places?
by having a pre-synaptic neuron diverge to multiple post-synaptic neurons
how can low levels of action potential cause a big action potential?
by the process of summation low levels AP can be AMPLIFIED
describe what happens when a synapse is over stimulated by same stimulus
the neuron runs out of vesicles = fatigue , no response produces AND it become HABITUATED which prevent damage from overstimulation
Na+ channels remain open
resting potential is not established
What is the importance of the junction between neurons?
-Ensures movement of the action potential in one direction
-Integration
-Summation
What are 3 structural differences between motor and sensory neurons?
Motor:
Cell body in the CNS
Cell body in at the end
Long axon
Sensory :
Cell body outside che CNS
Cell body in the middle
Short axon
What do all action potentials have the same?
Magnitude
What is the process by which acetylcholine is released in the synaptic cleft
Process by which they diffuse
Exocytosis
Diffusion
What is the feature of SYNAPSE that allows transmission in one direction?
Only pre synaptic neurons have acetylcholine vesicles
Only post synaptic neurons have receptors
Why does damage to myelination result in loss of sensation
Damage to myelin sheath results in less insulation so it interferes with sensation conduction
what can increase the speed oc f=conduction?
myelination
large axon - greater surface available for diffusion of ions, increasing speed of conduction
all-or-nothing law
if stimulus is not strong enough ,threshold is not reached ,depolarisation is insufficient ,action potential. is not generated
