[Music] yes yes it's uncle jigs answered its videos all about the reaction time required practical so we finished all of biology 1 now we own the bondage of tuba quite practical this video was broken down into these sections the first one is the organization of the nervous system then we're looking at the reflex arcs then they require practical itself and finally possible questions that you may get in your exams as always check out the description below for today's worksheet and also the answers to the previous videos worksheet as well okay let's do this tag now if I was to place you in a dark room and stimulate this part of your brain you hear things even though there's no sound in the room and if I stimulate this part you take space even though there's nothing in your mouth now if we follow these connections from the taste center and auditory center in your brain we see that these cells end up being connected to your tongue and ears respectively the same is true for all your other sense organs the nose the eyes all of them have a specific part of the brain that they stimulate in order for you to be aware of your environment think about how mad that is your brain is making up your reality based on what these cells are doing your nervous system can be summed up in this flowchart stimuli receptor coordinator effect on stimuli are changes in your environment for example a sound wave propagating from your own when you get a notification at this stage it's just vibrations in the air the receptors detect the stimuli and send an electrical impulse in this example that would be the hair cells in your inner ear that detects the sound wave but you have different receptors for your different sense organs each adapted to absorb in the different types of stimuli in your environment the coordinator is technically your central nervous system which is just your brain and spinal cords we can abbreviate that to just CNS the spine is evolved in B fences which will touch up in the mid the brain processes your electrical impulses and decides what to do with all of that information the nerve cells that connect your receptors in your sense organs to your CNS are called sensory neurons now just a quick side note on these names a new run is just another name for a nerve cells but nerves are bundles of hundreds of neurons even thousands in some locations get into the habit of calling individual nerve cells new right so you don't make the mistake of calling them nerves you may end up getting on the examiners nerves if you do that oh wow tough crowd when the brain decides what to do with you that impulse arm in this example working out what the sound is and its direction it sends an impulse to your motor neurons these are new ones that nature C&S to effectors effectors could either be muscles or glands when an impulse from a motor neuron hits a glint it causes it to release substances these could be stuff like hormones enzymes mucus anything like that but in our example the impulse is going to the muscles in your neck to turn your head towards the direction of the phone check out my video on specialized animal cells for more details on the structure of neurons okay here are some summary notes on all of that one of the most important survival mechanisms that we have are reflexes reflexes are rapid automatic responses that do not involve the conscious part of the brain since it doesn't use the brain it means that you can react very quickly and limit the damage that something might be causing you let's say you're putting up your Christmas lights and you burn your hand you don't have to think about moving your hand your body gladly makes that decision without your permission have a look at this diagram the thing that makes this response so fast is that initially does not go to your brain the signal of pain or regret that you feel form after you moved your hand away this butterfly looking saying here your spinal cord this flow chart shows you the passage of information in a reflex all stimuli receptor sensory neurons relaying neuron motor neuron effector and dent your response first you have your stimulus this is the fire in this example then your receptor in this example is the heat and pain receptors in your skin which send electrical impulses down your sensory new one the sensory neuron extends into your spinal cord do not call it your spine your spine is the bone okay then over here when you look at two new runs next to each other you see that they're not actually touching when an impulse arrives at the end of an axon chemicals are released from that new rod these diffuse across the synapse this gap is called a synapse and then they're bind to the receptors on the next neuron check out my video on diffusion for the full breakdown on how that works after the chemicals bind you probably guessed it the next neuron then sends an electrical impulse down it's tax on your new ones in the spinal cord are called your relay neurons the V manual then pass the q2 signals across another sign maps to your motor new run again notice that the signal does not initially go to your brain the motor neurons then stimulates the muscle cells causing them to contract and then your response is that your hand moves away from your stimuli here are some summary know some of the reflux up now we're ready for the require practical itself this is probably the easiest require practicals to do but the idea of reaction time can be a bit confusing at first the action time is a measure of how long it takes an organism to react to a stimuli look at these two reaction times 0.25 and 2.50 which one is the fastest the key is to remember that you're talking about time and not speed if it was speed then obviously 2.5 liters per second is faster than 0.25 meters per second but know you are talking about the time so the shorter your reaction time the quicker you are the first individual to do 0.25 seconds to react to a stimulant while the second was 10 times slower taking 2.5 seconds to react a cheap way an easy way of doing this in school is just to measure how long it takes you to catch herb fallen ruler you just even measure that this is you don't have to use time anywhere here the stimuli is the full length ruler that visual information goes into your brain which sends an electrical impulse that are mostly your hand to contract and catch these examiner's can give you various variations on this experiment I'll be looking at two in particular investigate whether practice reduces human reaction time that's our first one these are the steps for that first reaction time experiment sit down on a chair and place your weaker hand on the table number two your partner will hold the rule of vertically with the Zil centimetre end in between your thumb and first finger number three without telling you or giving you any signs your partner will let go of the ruler number four you don't try to catch the brunette as soon as possible when you see it drop it number five you record your distance in a table like this and repeat to get a total of ten results number six switch places with a partner and repeat the experiment then number seven we're gonna use a conversion table which looks like this this converts your distance into reaction time now it is very likely that you will see some decrease in reaction time that just shows you that the more you practice the better you become or something another way that a practical beat could be carried out is like this investigate how caffeine affects reaction time in this investigation you carry out the same steps but you do one experiment without coffee or caffeine and the number one Wolfe caffeine caffeine is a stimulant which increases your awareness so you should reduce your reaction time because you're taking a stimulant that makes you more alert so you'll be better able to detect when that wheeler is dropping there are other variations that they could give you the steps would be the same the only thing that's changing is your independent variable and your independent variable in the exams could be soft like investigate if age affects reaction times or age is your independent variable it could also be gender it could be directions like music or conversation as they're things that they can change let's look at the possible questions that you could get for this require practical dive and torture this first one suggest improvements to the experiment what you can do here is to increase the number of repeats and calculate and me what this does is that it reduces the impact of random errors you could also use more people and this gives you a bigger sample size you could also use a computer program that measures reaction time this will reduce the chances of the person catching the ruler anticipating when the ruler is dropping another question you could get is explain the anomalous result what they can do here that they could get you to identify an anomaly calculate the mean and then explain how that anomaly occurred if your result is lower than expected the person could have predicted when the ruler will drop and saw already started a process of trying to catch it if the number is higher than expected then the person could have been distracted by something maybe a conversation or someone get a detention who knows so yeah that was reaction time way deeper this is actually the easiest required practicals so make sure you got this one a lot anyway make sure you check out the worksheet below in the on certain last week's worksheet Merry Christmas and all that if you're a year leaven you better be using some of this time to revise has a recording this you have 20 weeks onto your biology 1 paper so you bear be revising over the holidays yeah you got to with Tim advice anyway like if you like subscribe become necessary and yeah in a bit you