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