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39 Cards in this Set
- Front
- Back
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WHAT ARE SENSORY RECEPTORS? |
specialised cells that detect change in our surrounding. Usually reffered to as energy TRANSDUCERS |
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WHAT IS MEANT BY ENERGY TRANSDUCER? |
Converts one form of energy to anouther form of energy. |
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GIVE EXAMPLES OF SENSORY RECEPTOR AND ENERGY CHANGES DETECTED? |
rod and cones in retina: LIGHT INTENSITY RANGE OF WAVELENGTHS olfactory cells in nasal cavity (nose): PRESENCE OF VOLATILE CHEMICALS Taste buds on tongue:PRESENCE OF SOLUBLE CHEMICALS pressure receptors on skin: PRESSURE ON SKIN sound recepto (cochlea):VIBRATION IN AIR muscel spindles: LENGTH OF MUSCEL FIBRE |
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WHAT IS A POLARISED MEMBERANE? |
one that has a potential difference acrossit during resting potential |
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WHT IS A DEPOLARISED MEMBERANE? |
Loss of polarisation across the memberane when sodium ions are entering the cell making inside less negative than usual during the action potential |
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WHICH SIDE OF THE MEMBRANE NEGATIVE AND WHICH SIDE IS POSITIVE? |
Inside is negative outside is positive |
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WHAT IS THE RATIO OF SODIUM TO POTASSIUM IONS ON EITER SIDE OF THE MEMBRANE? |
For every 3 sodiums going outside the cell there are 2 potassium ions going in? |
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WHAT ARE THE CARRIER POTEINS THAT ACTIVELY TRANSPORTS SODIUM AND POTASSIUM ACROSS THE MEMBRANE? |
sodium/potassium pumps |
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WHAT IS GENERATOR POTENTIAL? |
small depolarisation caused by sodium ions entering the cell from the receptor responding to changes in the enviroment opening the sodium ion channel. |
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WHAT IS AN ACTION POTENTIAL? |
achieved when the membrane is depolarised to a value of about +40mV. Its an all or nothing responce. |
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WHAT ARE THE DIFFERENT TYPES OF NEURONE WHAT DO THEY DO? |
sensory: CARRY ACTION POTENTIAL TO CNS motor:CARRY ACTION POTENTIAL FROM CNS TO EFFECTOR relay: CONNECT SENSORY AND MOTOR NEURONES |
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WHAT SPECIALISED FEATURES TO NEURONES HAVE HOW DO THEY HELP IT CARRY OUT ITS FUNCTION? |
many very long:CARRY ACTION POTENTIAL OVER LONG DISTANCE gated ion channels: CONTROL ENTRY AND EXIT OF SODIUM,POTASSIUM OR CALCIUM IONS sodium potasium pumps: USE ATP TO ACTIVELY TRANSPORT SODIUM AND POTASSIUM IONS maintain potential difference: TO CARRY OUT ACTION POTENTIALS mylelin sheath: INSULATE NEURONEFROM ELECTRICAL ACTIVITYIN NEARBY CELLS.PROVIDE GAPS WHERE SCHWANN CELLLS MEET NODES OF RANVIER cell body contains nucleus, many miotochondria and ribosomes: PRODUCE ATP FOR ACTIVE TRANSPORT, PROTEINS MADE sensory have long dendron:CARRY ACTION POTENTIAL FROM SENSORY TO CELL BODY WHICH IS POSITIONSED OUTSIDE CNS motor neurones have long axon: CARRY ACTION POTENTIAL TO EFFECTOR numerous dendrites:COMMUNICATION VBETWEEN OTHER NEURONES |
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WHY DO NEURONES NEED LOTS OF MITOCHONDRIA? |
To produce ATP to drive the active transport in sodium/potassium pumps Maintaining resting potential. maintain exocytosis of neurotransmitters at synapse |
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WHY DO MEMBRANES NEED SPECIALISED CHANNELS FOR DIFFUSION OF CHARGED IONS? |
charged ions can't disolve in phospholipid bilayer membranes like that of the axon, therefore can't diffuse across the membrane. ions need channel proteins to produce hydrophilic channel for diffusion or facilitated diffusion |
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DESCRIBE RESTING POTENTIAL? |
Potential difference or voltage difference across the neurone cell membrane while neurone is at rest. -60mV inside compared with outside. Cell membrane is said to be polarised. for every 3 sodium ions pumped out by sodium/potassium pumps 2 potassium ions are pumped in. Sodium ion channels are closed at rest. |
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EXPLAIN HOW ACTION POTENTIAL IS TRIGGERED? |
Change in enviroment e.g pacinian corpuscle detect pressure changed and open the sodium ion channel gates. Sodium ions flood in by diffusion down the concentration gradient into the cell from tissue fluid. causes DEPOLARISATION of membrane. gates futher along the neurone membrane open by changes in potential difference across membrane they are called VOLTAGE GATED CHANNELS
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WHAT ARE VOLTAGE GATED CHANNELS? |
Channels that allow passage of charged particles or ions. Contain gates that respond to change in potential differenc eacross membrane |
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WHY ARE ACTION POTENTIALS REFERED TO AS ALL OR NOTHING? |
a small depolarisation will not trigger and action potential and wont trigger that voltage gated channels.If the depolarisation is large enough to reach the threshold potential, it will open voltage gated channels cauasing action potential. |
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EXPLAIN THE IONIC MOVEMENT ACTROS STHE MEMBRANE DURING ACTIO POTENTIAL? |
1. resting, polarised. inside cell -60mV 2.Sodium ion channels open allowing some sodium ions to diffuse in the cell 3.membrane depolarises- becomes less negative, reaches threshold of -50mV 4. Voltage gated ion channels open sodium ions flood in by diffusion. cell becomes more positively charged inside compared to outside 5. potential difference reaches +40mV indide cell compared to outside 6. sodium ion channel gate close potassium ion channel open 7.potassium ions diffuse out bring the potential back to negative inside compared to out- REPOLARISATION 8.Potential difference overshoots slightly -HYPERPOLARISED 9.Original potential restoredto resting state. |
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WHAT IS THE THRESHOLD POTENTIAL? |
the potential difference across the membrane of about-50mV. If the depolarisation does not reach the threshold then it won't trigger an action potential. |
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WHY ARE ACTION POTENTIALS DESCRIBED AS ALL OR NOTHING? |
If the depolarisation does not reach the threshold potential it will not open the voltage gated channels.therefore action potentials only occur when the potential reaches the threshold potential. |
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SUGGEST WHY NEURONES NEED TO CONTAIN A LARGE NUMBER OF MITOCHONDRIA |
mitochondria is needed to produce ATP and pump the sodium and potassium pumps to maintain resting potentials. Also for the exocytosis of neurotransmitters at the synapse. |
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WHY DO MEMBRANES NEED SPECIAL CHANNELS FOR HE DIFFUSION OF CHARGED IONS? |
charged ions cannot pass the phospholipid bilayer so special ion channels are needed for diffusion or facilitated diffusion. |
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EXPLAIN WHY A NEURONE IS ACTIVE WHILE IT IS SAID TO BE RESTING? |
the neurone is maintaining a resting potential so sodium and potassium ions are moving in an out of the neurone. |
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WHAT IS THE ROLE OF THE ORGANIC ANION INSIDE THE NEURONE? |
the ion makes sure that the inside of the neurone is negative during rest potential. |
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WHAT IS THE DIFFERENCE BETWEEN THE GATED CHANNELS AND IN THE GENERATOR REGIONS AND THOSE FUTHER ALONG THE NEURONE? |
gated channels close and open in the generator region which operated by energy coming from the stimulus. other regions are triggered by potential difference changes and depolarisation. |
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WHY IS IT IMPOSSIBLE TO TRIGGER AN ACTION POTENTIAL IN THE MEMBRANE THAT IS HYPERPOLARISED. |
HYPERPOLARISED IS VERY POLARISED SO IT IS DIFFICULT TO REACH THE THRESHOLD POTENTIAL.VOLTAGE GATED ION CHANNELS DON'T OPEN. |
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WHAT ARE LOCAL CURRENTS? |
are the movements of ions along a neurone. caused by an increase in concentration at one point which causes diffusion away from the region of high conc. |
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EXPLAIN LOCAL CURRENTS IN DETAIL |
>sodium ion channel open at action potential. >sodium ions flood in creating high concentrations in a region >sodium potassium pumps >due to the high concentration of sodium ions at the point >the charged sodium ions repel and move along the neurone |
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WHEN SODIUM IONS DIFFUSE ALONG THE NEURONE THEY REDUCE THE POTENTIAL DIFFERENCE OF VOLTAGE ACROSS THE MEMBRANE. THIS IS THE START OF DEPOLARISATION OF THE ADJACENT AREA OF THE AXON MEMBRANE THE DECREASE IN POTENTIAL DIFFERENCE CAUSES THE SODIUM ION GATED CHANNEL TO OPEN WHICH ALLOWS MORE SODIUM ION TO DIFFUSE IN THE NEURONE. WHAT SORT OF FEEDBACK IS OPERATED IN THIS EXAMPLE? |
POSSITIVE FEEDBACK |
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WHAT IS SALTUATORY CONDUCTION? |
JUMPING CONDUCTION REFERS TO THE WAY ACTION POTENTIALS JUMP BETWEEN NODES OF RANVIER. |
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WAT IS THE MYELIN SHEATH? |
INSULATING LAYER OF FATTY MATERIAL. SCHWANN CELLS MAKE UP MYELIN. |
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WHAT IS THE ADVANTAGE OF SALTUATORY CONDUCTION? |
MYELINATED NEURONES ALLOW FASTER TRANSMISSION AND ARE QUICKER |
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WHAT ARE NEUROTRANSMITTER? |
a chemical that diffuses across the cleft of the synapse to transmit a signal to the postsynaptic neurone |
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WHAT IS CHOLINERGIC SYNAPSE? |
the synapse that uses acetylcholine is the transmitter substance |
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what are the specialist features of the synaptic knob? |
>Many mitochondria >smooth endoplasmic reticulum >vesicles containing acteylcholine >voltage gated calcium ions |
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explain the steps of the transmission across a membrane? |
-action potential arrive at synaptic knob -voltage gated calcium ion channels open due to the depolarisation -calcium ions diffuse int he synaptic knob -calcium ions cause the synaptic vesicles to fuse with the presynaptic membrane. -acetylcholine released by exocytosis -acetylcholine diffuse across cleft and bind the the specific ligand gated sodium ion channels -ligand gated sodium ion channels open -sodium ions diffuse in the post synaptic membrane -generator potential created -if sufficient generator potential is created then the potential reaches the threshold potential. -a new action potential is created. |
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what is the role of acetylcholinesterase? |
it is an enzyme in the cleft that stops the transmission of acetylcholine by breaking it down to ethanoic acid and choline. ethanoic acid and choline are recycled to combine and create acetylcholine using ATP from respiration from mitochondria. |
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EXPLAIN WHY THE CALCIUM ION CHANNELS NEED TO BE VOLTAGE GATED? |
only want to trigger the calcium ion channels if there is an action potential that has reached the threshold potential. |
