welcome to the summary video of national park biology unit 2. today we're looking at kirya to control and communication because this is a larger carrier we're going to split this into two parts the nervous system and hormones so we're going to start off in this video looking at the nervous system so first of all the nervous system is made up of two parts the first and very important part is the central nervous system sometimes abbreviated to the cns which is made up of both your brain and your spinal cord the central nervous system and the peripheral nerves all these other nerves around your body complete your entire nervous system but your central nervous system is only made up of the brain and spinal cord there are three parts of the brain that you need to know you should know how to identify them and what they actually do the first is down at the bottom of the brain and at the top of the spinal cord is the medulla this controls breathing and heart rate it controls unconscious responses that you do not need to think of the second part which is this uh outlying part at the side at the back is called the cerebellum and that is responsible for balance and muscular coordination finally the part at the top the wrinkled area that looks more like a stereotypical brain is called your cerebrum and the cerebrum is responsible for conscious thoughts such as memory reasoning and intelligence threat your nervous system is made up of neurons and through neurons information is passed along through electrical impulses this is going to be different from hormones that we'll look at in the next video there are three main neurons that we need to know though there's the sensory neuron the interneuron and the motor neuron and if you want to try and remember the order of this think sim sim sensory entered motor essentially the sensory neuron sends electrical nerve impulses from sense organs these are organs such as your skin picking up touch or your eyes picking up light information is then sent electrically through the sensory neurons to your interneurons your interneurons are found within your central nervous system which hopefully you remember is your brain and your spinal cord and this connects then to the motor neurons the motor is responsible for movement and this sends a nerve impulse from the interneurons in the central nervous system to an effector an effector can be either a muscle such as movement like i said previously or it could be a gland that releases a hormone and this effector enables a response to whatever the sensory input was so again just to show you this process once more your body is full of these sense organs which have sensory receptors and they detect stimuli or a stimulus such as light sound chemicals touch from the environment once that stimulus is picked up the electrical signal is sent from the sensory neurons to the interneurons like we said in the central nervous system and then once that information is processed in your central nervous system brain and spinal cord the interneurons send a message on to the motor neurons which create this response in an effector such as a muscle or a gland there is another response that we'll talk about as well which is to protect your body from harm and this is called a reflex the reflex art is rapid and it is automatic so if you think of um flinching away from something painful or from heat or coughing or blinking you don't think about this it's an automatic unconscious response to protect your body from harm so again we see this sensory enter a motor and ural pathway however you'll see here in the diagram a reflex reaction uh doesn't go through the brain although it still goes through the central nervous system it goes through the spinal cord the reason for this is because this is automatic you are literally not thinking about it and it has to be fast to protect you from harm so in order for reflex reactions to be fast they bypass the brain and they travel through the spinal cord that still go from sensory enter and motor neurons finally all these neurons have a gap between them and the gap between each neuron is called a synapse now for information to pass from one neuron to the other the electrical impulse once it hits the end of a neuron has to cross the synapse that impulse and that message crosses the synapse through chemicals these chemicals are called neurotransmitters which then transform transfer the message from one neuron to the other across the synapse that is your summary of the nervous system the next part of this video covers hormones and that makes up the rest of this key area