Hey guys, welcome back to another Biology with Zhan Xuan, IGCSE biology video so today we are going to go through chapter 14 which is coordination and response so this is quite a heavy chapter therefore we're just going to go detail as much as possible because this is one of the most asked questions asked topics in the exam so nervous system so nervous system is allows the body to respond to changes in the environment this is process usually coordinated by the brain so bring is one of the central nervous system organs okay and then reflex actions are extra rapid responses to stimuli and this process Allah also involves the nervous system by bypasses the brain so if you can see that in MRS GREN back to chapter one sensitivity comes into place in the definition of sensitivity it says it detects surroundings through stimuli so this is nervous system now Okay so first thing we're going to go through the receptors and effectors so what do we know about receptors and effectors okay so receptors are groups of specialized cells so they can detect changes in the environment which are called stimuli and turn them into electrical impulses okay and receptors are often located in the sense organs such as the ear eye and skin each organs has receptors sensitive to the particular kinds of stimulus so different receptors got different different types of working characteristics okay and an effector is any part of the body that produces the response so muscle Contracting move the arm a gland releasing a hormone into the blood so it's what that gives out something and yes this is just a bunch of glands here so you can see that looking down we need to know the adrenal gland the Patriotic gland is at the brain if you can see others you don't really need to know okay all right neurons so neurons are nerve cells they carry information as Tiny electrical signals they are three different type of neurons each with a slightly different function so sensory neurons carry a signal from receptors to the spinal cord and the brain so it's like a tree it's like one whole stick but they have neurons at the end of the left and the right side so these are like a receptors and relay neurons are carrying messages from one part of the central nervous system to another and a motor neuron is carry signals from the CNS to the effectors so relay is the left and then usually a motor is going to derive from the big to the small okay to the effect that's not yes yes here is just one of the diagrams so sensor neuron you can see that um there's an Impulse flowing through the big to the smaller one and then there's a cell body here and a motor neuron is also similar that they have very some big the small so from the impulses too so they went into the flow of impulses of traveling and relay neurons are basically dendrites and their flow of uh flow of impulse is going out Direction so here accent so the actions are basically it carries impulses away from the cell body and then drives a pickup signals impulses from nerve endings and my lean sheath insulates the nerve fibers and increases the speed at which the nerve impulse is transmitted okay so yeah this is all about this one so here's the CNS and the pns it's the central nervous system uh usually it's only the brain and the spinal cord and the peripheral nerve system contains connects the CNS to the body okay so yeah central nervous system so anyone responds to a stimulus coordinated by the incentral nervous system you can see the brain and the spinal cord as mentioned and gathers information about and responds to changes in the environment so there are types of stimulus receptors Sensory neurons CNS motor neuron effect and response so these are the pathway of electrical impulses in the nervous system okay and the peripheral nervous system is considered motor and sensory neurons and carrying bosses from the receptor to the cnnc they were well connected together as well as the impulses from the CNS to the effectors all right next one is voluntary and involuntary reaction so a reflex action is the way of the body to automatically and rapidly respond to a stimulus to minimize any further damage to the body so this is how the pathway works so they have stimulus and receptors and sensory motor neurons and effector and response so you can see this is the process of how stimulus receptor sensory neuron really new and motor neuron effect and response so they only have a sensory neuron in and but the CNS is moving at the slower rate so the nerve pathway followed by a reflex action is called a reflex arc okay so here are synapses so synapses they are basically a junction between two neurons which engines the impulse travel in One Direction only something like the heart where arteries only travel in One Direction and cannot mix okay so an electrical impulse just travels along an axon so this triggers the nerve endings of a chemical neuron to release chemical Messengers called neurotransmitters okay so the diffusers into the cyanide clef or the sanitip galactic cinetic Gap and bind with the receptor molecules of the membrane of the next neuron and then that's with the new that's where the new neurotransmitter is diffused diffuses in and then it binds with the receptors okay in binary receptors and then the impulse continues and stimulates the second neuron to transmit the another electrical impulse Okay so yes this is the structure of the eye now so I is one of the main sense organs so sense of organs are basically a group of receptor cells responding to specific stimuli light sound touch temperature and chemicals so yeah here is the structure of the eye we have the we just have to know the cornea the pupil the lens the iris the optic nerve retina and the fovea Okay so let me see what's so yes here so cornea reflects light and bends as it enters the eye so reflex like cornea is here the one that it's like it's uh building them outside and con Iris controls how much light enters the pupil so iris is here you can see it's like a two things holding on so I and I okay if it's easy to remember I and I and then we have lens focuses like onto the retina lenses here basically I won't mean I and then retina contains the light receptors usually behind controls how much lines being entered and carries an optic nerve carries and balances between the eye and the Brain here okay you know if you notice nerve that day definitely um and basically sends signals to the brain okay so yes the retina so two types of photoreceptor cells so Rod sensitive to demonline and black and white found further behind the on the retina and the cones are the one that's sensitive to color a small area called the fovea in the middle of the retina has many more cones than rods because we are seeing color okay so yeah here is the iris and the pupil reflex so pupil reflects is one of the most involuntary response and two things that were being separated is circular muscles and Radial muscles both of them are antagonistic muscles what is my antagonistic one relaxes and one contracts okay so when you are seeing in bright light your circular muscles to contract your radial muscles will relax okay and then your iris are contracted and much larger but the pupil size is smaller okay the amount of light in the endless is less see most of it is very contracted in right light in dim light dim light is circular muscles relax radial muscles contracts your iris is relaxed that's why it becomes smaller pupil size becomes larger amount of light enters more okay okay focusing light focusing light is basically light passes through the eyeballs the retina is refracted its rays are banned by the cornea bending line and lens make fine adjustment so the light is brought to a focus on the retina so this is a eye accommodation accommodation means the process where land changes shape to control the amount of it reflects the light refracts huh okay so you can see this is like physics now diverging and um lots of all of these things so here okay this is um okay nevermind so distance Vision means far away so you can see that it's usually much it travels further and much has space between its between the each of the uh arrows so ciliary muscles relaxes suspensory ligaments Titans and the land shape is elliptical or thin you can say and light refracted lesser same thing as brighter they allows lesser light to enter and nearer vision is where ciliary muscles contract suspensory ligaments slack and la and its land shape is spherical factor or thicker light refracted more nearly the same thing okay so yeah next one is the endocrine system okay so the endocrine glands secretes hormones into the blood and hormones are basically a chemical substance produced by a gland and Carry Out by the blood which Alters the activity of one or more specific targets of organs okay so back to here we know that that's the adrenal glands pancreas testis ovary pituitary glands okay so yeah that's all so in the mean endocrine glands that we have to know here it's like battery thyroid adrenal pancreas and dusties and ovaries they are the ones that produce customs and estrogen Okay so yes here are the few things so we have to know four different kinds of hormones basically so hormones first one is adrenaline so they are adrenal glands they prepare body for vigorous actions so which part of the target the most is respiratory respiratory circulatory system so the effect is that it's like an increased breathing rate increase pulse rate it widens the pupil and chemical control of metabolic Rays increase your blood glucose concentration and password together okay next one is insulin which is produced in the pancreas so they reduces the concentration of glucose in the blood they usually controls the blood glucose levels next one is that's this that's the produce testosterone so they cause the development of male secondary sexual characteristics so like increase mushrooms Mass increase body hair controls growth and development okay last one always that produces estrogen cause the development of female secondary sexual characteristics and helps in the control of the menstrual cycle okay so yeah so adrenaline adrenaline it's like mostly targeted to the cardio respiratory system where heart takes one of the biggest functions where because it where the pulse rate are being controlled everything that helps to run our body because blood is flowing through everywhere so we can see some examples here like sweat takes part of it because if your posture increases your body have to work much harder therefore they produce more sweat out so you can have like we want to urinate more because excretion occurs rapidly and breathe more rapidly oxygenating than blood so ready to fight or flee okay all right the difference between the nervous system and the endocrine system so nervous system you have the neurons usually made up with neurons basically and information transmitted in the form of electrical pulses in the form of electrical impulses and impulses transmitted from axons to dendrons and pulses travel very quickly and the effects of nerve impulse usually last only for a very short time and endocrine system is made up of secretory secretory cells information transmitted in the form of chemicals called hormones and chemical carry dissolved in the blood plasma travels more slowly effect of hormone May last longer Okay so this is kind of the difference so similar languages between two of them is that they have they occur in a human of course and then it's involved in survival Lots survival actions okay next one last one um this is gonna be coordination and response in plants give me a second looks like we are liking something here all right [Music] um we're going to talk a bit more of um homeostasis okay so homeostasis is basically the maintenance of a constant internal environment so they control the internal conditions within set limits and negative feedback changes causes a response that reverse the change example that if a situation is too hot your thermal regulatory system detects increase of temperature or blood temperature receptors okay and the response for too hot is that they sweat glands will produce sweat definitely and arteries dilate that's called vasodilation and layers of fat which cause for insulation so you know that once sweat is produced is to help to cool down the body so it evaporates and vasodilation is increased the blood flow to the skin surface heat lesser by radiation and therefore it turns much greater and the laser fat is definitely for insulation and if it's too cold your thermoregulatory resistant thinks that temperature is too low and muscle counts in aerobic respiration contract shivala and that's where you produce heat energy your arterials constrict vessel constriction occurs in decrease the blood flow to skin heat loss by radiation and then hair Erectors muscles contract where it pulls hair ups and trap layers of insulating air okay all right there are two scenarios in um remember that we talked about pancreas and then um all those so what happens in a scenario where blood sugar levels are too high so pancreas detox changes definitely and they of course secretes insulin okay the secret insulate what they do is that insulin travels to the liver first of all and change from glucose to glycogen okay next one is where when blood sugars are too low pancreas did like changes and banquet secretes glucagon so glucagon travels to the liver and glucagon change to glucose therefore to provide you an extra amount of sugar in your body okay so in that situations we know that type 1 diabetes is where they don't have enough insulin okay therefore they need something in order to pump sugar in order to change from glucose to glycogen and symptoms are in crystals and urine and treatments are insulin injection diet exercises basically okay so yes this that is all from homeostasis right now we're going to go through coordination and response in Plants again Plants they also produce hormones and responds to external stimuli growing towards sources of Water and Light which they need to survive so Tropic responses that's what it leads to tropism a growth response to a stimulus so we know that tropism is a growth in response positive tropism is where it towards the stimulus neglectropism is that it's away from the stimulus or opposite of the positive trapezium and phototropism it means direction of light and geotropism is due to gravity Okay so he is a one few uh scenarios we have positive phototropism inside the stem tip grows towards the light so they get maximum light for photosynthesis and negative phototropism is where it hits the root tip grows away from the light and less chance of drying out pause the new phototropism is where is the root tip towards gravity more chance of finding moisture because the absorption of root hair cells is important and negative geotropism is that the stem tip is up away from Gravity more chances to find light okay okay that's where one of the hormones main hormones in plants are called auxin so auxin are mostly made of tips of shoots and Roots they can diffuse the other parts of shoots and Roots they can change the rate of elongation in plant cells controlling how long they can become so cells includes elongate more cells in root inhibit elongation Okay so here even even like oxygen is made at the tip of the root and shoot cells on this side grow quickly so they grow on the side auxin is made at the top so auxin made in the Deep diffuses evenly down the sugar the should grow straight up so oxygen concentrates on the Shady Side this causes the Shady Side to grow faster than the light side so the shoot bends towards light okay makes sense here is when cell elongation occurs okay so when sunlight is overheat the IAA molecules produced by the African medicine are distributed even evenly in the shoot so once the sunlight Shines on the shoot and the angle the IAA molecules move to the far side and induce the elongation of cells on that side and cell elongation results in the bending of the shoot towards light so here is what happens when um there's like a tip or a guard jelly so if there's a guardian it most often can diffuse through if there's light bends okay so here are auxes and gravitropism so this is a positive gravitropism and auxins are growing appropriately okay so oxygen in gravity tropism is that if the should Place horizontally in the absence of light auxins accumulate on the lower side of the should due to gravity so the cells on the Lower Side grow more quickly the shoot bends upwards this is called negative positive gravity dropism is where it goes down so you see the root bends downwards this is called positive very tropism okay isn't that hard right okay eat the elation so each donation is where is they grow in the dark it's a little plants potentially die no photosynthesis occurs they're usually pale tall and thin small leaves far apart leaves are yellow and lastly with Killers weed killers are synthetic plant hormones one example is 24d so they affect broader leaves causes rapid growth and increase depth it basically kills the plants okay all right that is all for coordination response so I hope you understand this fairly well as it you have to remember a lot of things especially the eye and that's all for coordination response to this so I hope you uh enjoy the this video and hope to see you in the next time bye bye