Module 5.3 Flashcards
what are sensory receptors
sensory receptor are specialised cells that can detect changes in our surroundings . Most are energy tranducers that convert one form of energy to another .
what do tranducers detect
each type of trandsducer is adapted to detect changes in a particulr form of energy . This may be a change in ligh levels , a change in pressure on the the skin or one of many othe renergy changes . Other receptors detect the presence of chemicals .
what is a change in environemnt known as
whether it is a change in the energy level or the presence of a new chemical , is called a stimulus . Whatever , the stimulus , the sensory receptors respond by creating a signal in the form of electrical energy . This is called a nerve impulse .
stimulus - change in light intenisty
sensory receptor
energy change involved
light sensitive clels in the retina
light to electrical
stimulus - change in temperature
sensory receptor
energy change involved
-temperature receptors in the skin and hypothalamus
-heat to electrical
stimulus -changes in pressure on the skin
sensory receptor
energy change involved
pacinian corpuscles in the skin .
-movement to electrical
stimulus -changes in sound
sensory receptor
energy change involved stimulus -
-vibration receptors in the cochlea of the ear .
-movement to electricl
stimulus -movement
sensory receptor
energy change involved
-hair cells in inner ear
-movement to electrical
stimulus -changes in length of muscle
sensory receptor
energy change involved
-muscle spindles in skeletal muscles
-moememnt to electrical
stimulus -chemicals in hte air
sensory receptor
energy change involved
-olfactor cells in the epitheliu lining the nose .
-the receptors detect the presence of a chemical and create an electrical nerve impulse .
stimulus -chemicals in food
sensory receptor
energy change involved
-chemical receptors in the taste buds of the tonghue .
-these receptors detect the presence of a chemical and creae an electricl nevre impulse.
what is a pacininan corpuscle
a pressure sensor found in the skin
what is the mechanism of the pacinian corpuscle
the corpuscle is an oval shaped strucutre that consists of a series of concentric rings of connective tissue wrapped around the end of a nerve cell .
-When pressure ont he skin changes , this deforms he rings of connective tissue , which push against th nerve ending .
what is the corpuscle sensitve to
changes in presssure that deform the rins of connective itssue .. therefore when pressure is constant , they stop responding .
channel proteins facts (1)
if the channel poteins are premanently open , then ions can diffuse across the membrane and willd o so until their cocnentrations on either side of the membrane re in
channel proteins facts (1)
cells are associated with the nervous ssytem have specialised channel proteins . Some of these ae called sodium chaneels are specific to sodium ions . oThers are called potassium channels are specific to possium ions . these channels also possess a gate that can open or close the chnanle .
what are the sodium channels sensitive to
sodium channels are senstive to small movements of the membrane ,s ow hen the membrane is deformed by the chanign pressure , the sodium channels opn . This allows sodium ions to diffuse into the cell , producing a generaotr potentio ( also called a receptor potenital ) .
what are sodium potassium pumps (1)
membranes also contain sodium / potassium pumps that actively pump sodim ions out of the cell and potassim ions inot the cell . Three sodium ios are pumped out for every two potassium ions pumped into the cell . Whe the channl proteins are all closed , the sodium / potassium pumps work to creae a concentration gradient .
what are sodium potassium pumps (2)
The concentraiton of sodiu ions ions outisde the cell increases while the concentration of potoassium ions inside the cell increases . The memrbane is more permeable to potassium ions so some of these will leak out of the cell .. The membrane is less permable to sodium ions os few of these are able to leak into the cell .
What is the result of this ionic movmemtn
it is the potential gradient acros the cell membrane / The cell is negatively charged inside compared with outside . Tthisnegtive potential is enhanced by the presence of negativly charged anions inside the cell .
what happens when a cell is inactive
the cell membrane is said to polarised , that is negatively chagred inside comapred with outside .
how is a nerve impulse created ?
a nerve impulse is created by altering the permeabilit of the nerve cell membrane ot sodium ions . This is achieved by opening the ssodium io channels . As the sodium ion chnnels open , the membrnae permebilit is icnreased and sodium ions can move across the membrane odwn heir cocnentration gradient into the cell .
how is a nerve impulse creared (2)
the movemen of ions across the memrbane creaes a change in the potentail difference charge across the membrane . The isnide of the cell becomes less negative comapred wirh the outside thn usual . this is known as DEPOLARISATION , the change in potential acorss a receptor membrane is often called a GENERAORT POTENITAL .
what will happen if only a small sitmulus is detected in terms of chnnrels
only a few sodium channels will open . The larger the stimulus (the change in energy levels in the enviornemnt ) the more gated channels willo pen . If enough gates are opened and enough sodium ions neter the cell , the potenital difference acorss hte cell memebrane changes singigncanlty and will generat ena impusle or ACITON POTENTIAL .
What are motor neurones
neurones that carry n action potenital from the CNS ro the effector
What is a myelinated neurone
it has an individual layer of myelin around it
what is a non-myelianted neurone
it has an inidvidual layer of myeiln around it
wha is a relay neurone
joins snenosryneurones to motor neurones
what are sensory neurones
neurones that carry an action poential from the sneosry receptor to the CNS .
What happens when a stimulus has been detected
-iTS ENERG HAS BEEN converted to a depolarisation of the receptor cell membrane , the impulse msut be transmitted to other prts of the body . THe impsulse is transmitted along neurones as ana ction potential .
How is an action potential carried
as a rapid depolarisation of the membrane caused by the influx of sodium ions .
adaptation of neurones (1)
many are very long so that they can trasnmit the action potential over a long distance .
adaptation of neurones (2)
the cell surface (plasma ) membrane has many gated ion channels , tht control , the netry or exit of sodium , potassium nd calcium ions .
adaptation of neurones (3)
sodium / potassium pumps use TP ot ctively transport sodium ions out of the cell and potassium ions into the cell .
adaptation of neurones (4)
neurones maintain a potenital difference across their cell surface (plasma ) membrane .
adaptation of neurones (5)
a cell body contains the nucelus , many mitochhondira and ribosomes
adaptation of neurones (6)
numeorus dendirtes connect to other neuorne . The dendrites carry impulses towards he cel bdoy
adaptation of neurones (7)
an axon carries impusles away from he cell body
adaptation of neurones (8)
neurones are surroudned by a fatty layer that isnualtes cell from eelctrical actiity in other nerve cells neabry . This fatty layer is compsoed of schwann cells , clsoely associated with neurone .
what makes a motor neurone unique
motor neuornes have their cell body in the CNS HAVE A LONG AXON THAT CARRIES THE ACTION POTENTIAL OUT to te effector
what makes a sensory neurone unique
sensory neurones have a long dendron carrying the actionn potential from a sensory receptor to the cell body ,which is positied just outside of the CNS , they have a short axon ,c arrying hte action potetinal inot ht CNS .
what makes a relayn eurone unique
rela neurones connect the sensory and motor neurones together . They have many short dendirtes and a shor axon ,. THE NUMEBR OF DENDIRTES ARE THE DIVISIONS OF AXON IS VARIABLE , RELA NEURONES RE N ESSENTIAL PART OF THE NERVOS SYSTEM WHICH DONUC IMPUSLES IN COODINTED PTHYS .
MOre on myelinated neurones
most senosry and motor neurones are associated with many schwann cells , which make up fatty sheath called the myelin sheth . These schwann cells are wrapped tightly around the neurone so the sheath actually cocnsits of several layers of memebrane and thin cytoplasm from the schwann cell .
where are the nodes of ranvier
at intervls of 1-3 mm laong he nerone , rhwew EW Gpa in rhw mwlin ahwRH Wh node is about 2-3 micrometer .
what does it mean becaue the myelin sheath is tightly wrapped arround he neuorne
it prevents the movmeent of ions across the neurone memrbane , therefore he momn of ions across the memebrance can only occur at the nodes of ranvier . THIS MEANS THT THE IMPSULE OR ACTION POTENTIAL jumps from one node ot the next making CONDUCTION MUXH MOre raPID .
HOW ARE non-myelinaed neurones also assoiated with schwann cells
non -myeliantd neurones are also associated with schwannc ells , but several neruoens may be enshrouded in one loosely wrapped schwannc ell . This means hat the action potential moves alogn the nuone in a wave rather than jumping from node o node as seen in myelianted nuerones .
advantages of mylenaed neurone
myelianed neuornes can transmit an action potenital much mroe quickly than non myeliantd neurones . Can the typcial needs of tranmission , 100-120]
non myelinated 2-20
avdnatges of mylenated neuornes (2)
-Myelinatednueonres carry action potenital from sensory receptors to he CNS AND FROM THE CNS O THE EFFECTORS .
-They crry ction potentials over long distances - the lonegst neurones , ina human about 1m in lenh . THE INCREASE IN SPEED OF TRANSMISSION MEANS , tht the ction potenitl reaches he ned of he neurone MUCHMROE QUICKLY his enables a more rapid resposne to a stimulus .
strucutre of a non myelianted neurone
-non myelianted uerone tehnd ot be shorted nd carry out action potentials only over a shor disnance . They are often use din cooridning body funcitons such s brehing and the ction of the digestive sytem . THEREFORE THE INCREASED SPEED OF TRANMISSION IS NOT SO IMPROTANT .
What is ana citon potentil
it is a biref reversal of the potenital acorss the memrbane of a neuone causing a peak of +400mV comapred to the resitong potenitial pf -60mV .
What is positive feedback
a mechanisms that increases a change takign the system further way fromt he optimum .
what s a restin gpotental
the potenitl idfferenc acros the memrbane hwile the neurone is at rest .
ALTHOUGH SOME OF THE SODIUM IONS ARE KEPT CLSOED
Some of he potassium ions tht to are open , and therefore pasma membn eis more premable to potassium ions than to sodium ions .
-POTASSIUM IONS TEND TO DIFFUSE OUT OF THE CELL .
The cell cytoplasms also contains a large organic anions . Hence , the interiror , of the cell is maintained at a negative potential compred with the outside .
ALTHOUGH SOME OF THE SODIUM IONS ARE KEPT CLSOED (2)
THE CELL MEMBRANE IS SIAD TO BE POLARISED , the potential differene across the memebrn eis about -60mV , THIS IS CALLED A RESTING POTETNIAL NOE THAT MELIANTED NUERONES , IOSN EXHANGES DECRIBBE OOLY AT NODES OF RANVIER .
how to generate an action potential
while the nruone is at a rest it maintains a higher concentration gradient of sodium iosn across it plasma memrbane - the cocnenration is higher n inside than outside .
geenraitn an action otential (2)
if some of the sodium ions channels are opened ,t he sodium ions will wuicly diffus edown their cocnentration gradn into th cell , from surrodunin tissue fluid THIS CUASES DEPOLARISATION OF THE MEMRBANE .
Generation of an action potentil (3)
-In the generator region of a neurone the gated channels are opened by the aciton of the synapse ( a nerve junciton ) .
-When a few gated channels open , they allow a few sodiu ions inot the cell and porduce a small depolariation . THIS IS KNOWNA S A GEENRATOR POTENTIAL .
-it my go no furher .
generating an action potential (4)
however , when more agted channels are opened the generator , potenitals are combined to rpoduce a large depolarisation . If the , depolarisation reaches a aprticual rmgnitude i psses a threshold and will cuas en aciton potenitl .
generating an action potential (5)
msot of the sodium ion channels in a neurone are opened by changes int he potential difference across he memrbane - theya re called voltage agted cannels . When there are sufficent generaor potenitals to reach he threshold , potenitl hty cause the oltage gated channels o open . THIS IS AN EXAMPLE OF OPSITIVE FEEDABCK - a small depolrisation of the membrance causing a change that increase the depolarisaiton further .
what does the opening of voltage gated sodium ion channels allow
a large influx of sodioum ions and the depolaristion reaches +30 mV on the inside of the cell . Once this value is reached the neurone will transmit the ACTION POTENTIAL .
what does it mean that the action potenitl is self perpetuationg
once it starts at one point in the nuroent it will ocntiniue alogn tot he endo f he nruoens . ACTION PTOENTIL ARE THE SAME MAGNIEUD THEREFORE HTEY ARE REFERRED TO AS AN ALL OR NOTHIGN REPOSNE .
SEE graph on pge 2 stges of an action potential (1)
- membranes stas in its resing state - polarise witht he isnide of the cell being - 60mV compared ot the ouside . HIGHER CONC Of sodium ions ooutside hn INSIDE nd a higher conc of potassium ion sinside than otuside .
stages of action potential - 1
the membrane starts ub uts restubg srare - polrised with the inside of the cell being - 60mV compared , to the ouside . There is a higher conc , of sodium ions , than inisde than outside .
stages of action potential -2
sodium ions channels open diffuse into the cell .
stages of action potential - 3
the membrane depolarises it becomes less negative with respect to the outside nd reaches the threshold value of -50mV /
stages of action potential - 4
positive feedback causes nerby voltage gated sodium ion , channels to open and many sodium ion flood in . As more sodium ions enter , the cell become positively compare with the outside .
stages of action potenital - 5
the potential difference across the plasma membrane reaches +40mV . The inside , inside of the cell is positive compared with the otuside .
stages of action - 6
the sodium ion channels close and potassium channels open ..
stages of action - 7
potassium ions diffuse out of the cell bringing the potential difference back to negative inside comapred with the outside this is called depolarisation .
stages of action - 8
the potential difference overshoots slightly making the cell hperpolarised
stages of action 9
the original potential difference is restored so that the cell returns to its resting stae .
what is the refractory period
after an action potential , the sodium and potassium ions are in the wrong places .
-The cocnenrations of hese ions isnide and outside , the cells must be restored by the action of the sodium / potssium ion pumps .
refactiry peruid (2)
for a short time , after each action potential it is impossible to stimualte the cell membrane to reach nother action potenital .
-This is known as the refractory period , and alows the cell to recover , fter an ction potential , It lso ensures that action potentil are transmite in onde direction .
What happens when a sodium channel opens
At a particular point of th neurone upsets the balance of sodium and potassium ions set up the action of the sodium / potassium pumps .
-when sodium ions are slllsed to flood onto the neurone causing depolarisation , this created local currents in thr cytoplasm of the neurone .
Sodium ions begins to move along to what
Move along the neurone towards eefuobs where the concentrations is still lower .
-These local currents , cause a slight depolarisation , of the membrane and cause sodium ion channels , further along the membrane to open ( positive feedback ),
Formation of local currents snd the transmission of a nerve impulse (1)
When an Adrian potential occurs , the sodium ion channels open at the point in the neurone ,
Formation of local currents snd the transmission of a nerve impulse (2)
The open sodium ion channels allow sodium ions to diffuse across the membrane frim the region of higher concentrations outside the neurone into the neurone . The concentration of sodium ions inside the neurone rises at the point where rhe sodium ion channels are open .
Formation of local currents snd the transmission of a nerve impulse (3)
Sodium ions continue to diffuse sideways along the neurone away from rhe region , of increased concentrations . This movement of charged particles is a current called fhe local current .
Formation of local currents snd the transmission of a nerve impulse (4)
The local current causes a slight depolarisation further along the neurone knwhihci affects the voltage gated sodium ion channels causing them to open m . The open channels allow rapid influx , of sodium iPods cusses a full depolarisation ( action potential ) further along the neurone . Athena action potential has therefore moved along the neurone .
Formation of local currents snd the transmission of a nerve impulse (4)
The local current causes a slight depolarisation further along the neurone knwhihci affects the voltage gated sodium ion channels causing them to open m . The open channels allow rapid influx , of sodium iPods cusses a full depolarisation ( action potential ) further along the neurone . Athena action potential has therefore moved along the neurone .
The action poptential will continue to movie in the same direction until what
Until it reaches the end of the neurone x it will not reverse direction , bevayse the concentration of sodium ions behind yhe action potential is stipll high .
Salutary conduction (1)
As described in topic 5.3.2 the myelin sh Formation of local currents snd the transmission of a nerve impulse (1)ADH is an insulating layer of fatty materia , composed of Schwann cells cekks wrapped tightly around the neurone into. Sodium , and potassium ions cannot diffuse through this fatty Mayer ,
Salutary condcurij (3)
In between rhe schwann cells aee small gas - the node of Rancier , therefore the ionic movements thst create an scrioh potential cannot occur over much f the length of the neurone , they occur only at the nodes of the Rabcier . In myelinated neurones , the local currents and therefore elongated snd sodium ions diffuse , along the neurone from me jremtomRanvuer to the end .
THIS NEANS THAT the action potential appears to jump from one node to the next . This is called salutary conduction ln
Advantages of saltory conduction (2:
The myelin sheath that action potential , can only occur at the gals between the Schwann cells that make you the myelin sheath .
Effectively , the action potential jumps from one node of Rangier to the next .
THIS SPEEDS UP THE TRANSMISSIONA OF THE SCFION potential ,along the nuroheml myelinated neurones conduct scfion potenitwle more quickly thst non myelinated neurones . A myelinated neurone can conduct an action potential .n
Frequency of transmission
Nthemitneisty The impulse carried by a neurone by action p9tneital . All action potentials are the same intensity each one produces a depolarisation.
ALTHOUGH the size of the action potential is unrelated to the inefneidty of thr stimulus thst caused the action potnritwl , we can still detect stimuli of different intensities . Such as loud or quiet sounds , our sensory region
ALTHIUGH the size of or the action potential is unrelated to thr itneisty of the stimulus , that caused the action potential , we can still detect stimuli of different intensities such as loud or quiet sounds . Our brains determine the intensity of thr stimulus from thr frequency of sction potentials arriving in thr snd Peru region of thr Brian m. A HUGHER FREQUENCY A OF SCRION POTENITWL SMEANS A MORE INTENSE STIMULUS A.
What happens when a stimulus is at hugher intensity mriensodihm channels
Are opened in thr sensory receptor . This produces lore generator , potentials . As a result there are more frequent acrion potentials in the sensory neurone . Therefore rhere aee more frequency scrion potrnitsle entering , thr Center nervous systems l
Cholinergic synapse
A synapse that uses acetylcholine as its neurotrwnkietter .
Neurotransmitters
A chemical used as a signalling molecyled between two neurones in a synapse
Sreucure of a chollionegnic synapse
A synapse is a junction betweeen two or more neurones m where one neurones m can communicate with or signal to another neurone .
-baBetweeb the two neurones is a small gap , called the synaptic m cleft whigich ieprdimwtelu 20 nm wide .
The structure or choliniergic synapse
As described in 5.3?3 an action potential travels along a neurone as a series of ionic mom emrnrs across the neurone as a series of, of ionic movements across the neurone membrane .
THIS ACRION PORENIRAL , cannot bridge the gap between two neurones , instead , the acrion poreniral in the presynapric neurones causes yhe release of a chemical yhe neurotransmitter , that diffuses across the post synaptic neurone .
Synapses that she’s acetylcholine as the neurotransmitters , aee cholinehric synapses l
What is the presynapric neurone ends in swelling , called the presynapric bulb . This bulb contains a number of specialised features
…
What is the presynapric neurone ends in swelling , called the presynapric bulb . This bulb contains a number of specialised features
…
Presynaptic bulb (1)
Many mitochondria - Indicating that an active process needing atp is involved ,
Presynapric bulb (2)
A large amount of smooth endomplasmic reticulum such packages the neurotranmijtters , into vesicles ,
Presynapric bulb (3)
Large hungers of vesicles containing molecules od a chemical called acetylcholine thr transmitter , that will diffuse across the synaptic cleft ,
Presynapric buijlb
A number kf voltage fated calcium ion channels on rhe cell surface membrane
Presynapric byob
A bynevr if voltage gatyes coaixuj ion channels on rhe cell surface membrane ,
The post synaptic membrane
The post synaptic membrane contains specialised sodium ion channels thst can respond to this neurotransmitters . These channels consist of five polypeptid molecules . Two of these polupefoied have a special receptor site that is specific to axtetylcholien ,
Post synaptic membrane (2;
The receptor dieted have a shape that is commentary ro rhe shape of the acetylcholine neoclue . When acetylcholine choose is pressed om. In fhe synaptic cleff is bind m of fhe row dexeofie sides and causes the. Rhe sodium dhabeek Sri Olen ,
Transmission across the synapse part one
An action potential arrives at the synaptic bulb.
Transmission across the synapse part two
the voltage gated calcium ion channelsopen.
Transmission across the synapse part three
calcium ions diffuse into the synaptic bulb.
Transmission across the synapse part four
the calcium ions cause the synaptic vesicles to move to and fuse with the pre-synaptic membrane.
Transmission across the synapse part five
acetylcholine is released by exocytosis
Transmission across the synapse part six
acetylcholine molecules diffuse across the cleft.
Transmission across the synapse part seven
acetylcholine molecules binds to the receptor sites on the sodium ion channels in the post synaptic membrane .
Transmission across the synapse part nine
sodium ions diffuse across the postsynaptic membrane into thepost sysynaptic neurone
Transmission across the synapse part ten
a generator potential or excitatory post synaptic potential EPSPis created/
Transmission across the synapse part 11
if sufficient generator potentials combine then the potential across the post synaptic membrane reaches the threshold potential.
Transmission across the synapse part 12
a new action potential is created in the post synaptic neurone.
Once an action potential is achieved what will happen .
it will pass down the post synaptic neurone .
what is the role of acetylcholinesterase
if acetylcholine is left in the synaptic cleft , it will continue to open the sodium ion channels in the post synaptic membrane and will continue to cause action potentials.
what is the role of acetylcholinesterase(2)
Acetylcholinesterase is an enzyme found in the synaptic cleft. It hydrolyses the acetylcholine to ethanoic acid (acetic acid) , and choline . This stops the transmission of signals so that the synapse does not continue to produce action potentials in the post synaptic neurone.
how are the ethanoic acid and choline are recyled
they re-enter , the synaptic bulb by diffusion and are recombined, to acetylcholine using ATP from respiration in the mitochondria. The recycled , acetylcholine is stored in synaptic vesicles for future use.
what is summation
occurs when the effects of several excitatory post synaptic potentials (ESPS are added together )/.
action potentials and cell signalling
action potential is an all or nothing response . Once the action potential starts it will be conducted along the entire length of the neurone.
action potentials and cell signalling (2)
the action potentials does not vary in size or intensity. At the end of the neurone the presynaptic membrane releases neurotransmitter molecules into the synaptic cleft.
action potentials (3)
the post synaptic neurone responds to these molecules , which is an example of cell signalling . In cholinergic synapses the signal sent to the next neurone, consists of molecules of acetylcholine.
main role of the synapses
the main role is to connect two neurones , together so that a signal can be passed from one to other. However , the junctions can be much more complex than a simple connection between two neurones.
what do nerve junctions often involve
nerve junctions often involve several neurones - this could be several neurones from different places converging on one neurone or it could be one neurone sending signals out to several neurones that diverge to different effectors
what does one action potentials passing down an axon cause
it will cause a few vesicles to move to and fuse with the presynaptic membrane . The relatively small number of acetylcholine molecules diffusing across the cleft produces a small depolarisation .
what is the excitatory post synaptic potential (ESPS)
THIS on its will not be sufficient to cause an action potential in the post synaptic neurone.
why may it take several ESPS to reach the threshold to cause an action potential .
the effect of several ESPS combine together to increase the membrane depolarisation until it reaches the threshold . THIS combined effect is known as summation .
what can some presynaptic neruones produce
in additional some presynaptic neurones can produce inhibitory post synaptic potentials . These can reduce the effect of summation and prevent an action potential in the post synaptic neurone .
control of communication (1)
several presynaptic neurones might converge on one post synaptic neurone . This can allow action potentials from different part of the nervous system to contribute to generation an action potential in one post synaptic neurone - so creating a particular response . THIS Is spatial summaiton this could be useful when several different stimuli are warning us of danger .
control of communication (2) combination of several ESPS
this could be prevented from producing an action potential by one IPSP /
Control of communicaiton (3)
one pre-synaptic neurone might diverge to several post synaptic neurones . This can allow one action potential to be transmittted to several parts of the nervous system . This is usseful in reflex arc . One post synaptic neurone elicitis the reposnse while another informs the brain .
control of communication (4)
synapses ensure that action potentials are transmitted int he correct direction 0 only the presynaptic bulb contrains vesicles of acetylcholine . Therefore , if an action potential happens to start half way along a neuone and end at the post synaptic membrane , it will not cause a response in the next cell .
control of communicaiton (5)
synapses can filter out unwanted low level stimulus , creates an action , potential in the presynaptic neurone , because several vesicles of acetylcholine must be released to create an action potential in the post synaptic neurone
control of communication (6)
low level action potential can be amplified by summation . If a low level stimulus is persistent , it will generate several successive action potentials , in the presynaptic , neurone . The release of many vesicles of acetylcholine , over a short period of time will enable the posy synaptic ESPS rt combine together to produce an action potential .
control of communication (7)
after repeated stimulation a synapse may run out of vesicles containing the neurotransmitter . The synapse is said to be fatigued , . This means the nervous system no longer responds to the stimulus , we have become habituated , to it . It explains why we soon get used to a smell or a background noise . It may also help ooverstimualtion , of an effector which could cause damage .
control of communication (8)
The creation , and strengthening of specific pathways within the nervous system is thought to be the basis of conscious thought and memory . Synaptic membranes are adaptable . In particular the post synaptic membrane can be made more Sensitive , TO ACETYCHOLINE , BY THE ADDITION , OF MOST RECEPTORS . tHIS means that a particular post synaptic neurone is more likely to fire an action potential creating a specific pathway in response to a stimulus .
