 Imagine you're a frog. You're sitting near a pond. It's night and it's pitch dark. You hear faint whispers moving somewhere near you. You see the colour brown moving around. It's an ant. You extend your long sticky tongue and without even moving, you've got your midnight snack. How are frogs able to do this? Well, frogs can see colour even in the dark when there's absolutely no light. This is sort of like a superpower, right? Because we can't do this. We need some light to see colours. This superpower can be attributed to the well-developed control and coordination systems of frogs. The control and coordination system includes the nervous system, sense organs and the endocrine system. These three systems work tirelessly to make sure frogs keep on croaking. Not just frogs, but these systems can be found in other animals too, like birds, reptiles and us humans. Let's first take a look at how the nervous system is organised in frogs. The nervous system is split into the central nervous system, peripheral nervous system and the autonomic nervous system. The central nervous system includes the brain and spinal cord. The peripheral nervous system includes the cranial and spinal nerves. The autonomic nervous system includes the sympathetic and parasympathetic nervous systems. These three systems work by sending electrical signals. That's how these systems communicate. If you dissected a frog and took a look inside, you'd find that the brain is enclosed within the cranium or the skull. So let's take a closer look at the central nervous system of frogs which includes the brain and spinal cord. Frogs have a long and thin brain. This is the dorsal or the back view of a frog brain. Now what are the different structures of frog brain? You have the paired olfactory nerves which transmit sensory information about smell to the paired olfactory lobes. Now these olfactory lobes process the information about smell and order. Below the olfactory lobes lie the paired cerebral hemispheres. Now the cerebral hemispheres are the thinking centre of the frog. They control all the voluntary movement in frogs. Below the cerebral hemispheres is the diencephalon. The diencephalon regulates the sleep wake cycle of the frogs. So these three structures, the diencephalon, cerebral hemispheres and the olfactory lobes make up the forebrain or the front part of the brain. Below the diencephalon are the paired optic lobes. Now the optic lobes are involved in processing visual information. The optic lobes form the midbrain or the middle part of the brain. Below the optic lobes lie the cerebellum. So the cerebellum controls posture and muscle coordination. The medulla oblongata lies below the cerebellum and it controls involuntary functions like respiration, digestion and heartbeat. So the medulla oblongata and the cerebellum make up the hindbrain or the back part of the brain. The medulla oblongata passes through the opening called the foramen magnum and becomes the spinal cord. We can take a better look at the spinal cord in the ventral or the front view of the frog brain and this is the spinal cord. This is where the medulla oblongata exits from the foramen magnum and becomes the spinal cord. You see these lines that emerge from different parts of the brain. Well these are cranial nerves and frogs have 10 pairs of cranial nerves. So there are in total 20 cranial nerves. Now these cranial nerves connect different parts of the body to different parts of the brain. The spinal cord in frogs is enclosed within a vertebral column. Remember that frogs are vertebrates specifically amphibians. So the spinal cord is enclosed within the vertebral column. From the spinal cord 10 pairs of spinal nerves emerge. So there are 10 pairs of cranial nerves and 10 pairs of spinal nerves. These nerves connect different parts of the body to the spinal cord. So we learnt that the olfactory lobes and the optic lobes process sensory information. But where does that sensory information actually come from? The sensory information from the environment is detected by the sense organs and frogs like us have many sense organs. So these are the different sense organs of the frog. Of these the eye and tympanum are well developed while the others can be considered as just clumped up nerve endings. So let's first start with the eye. The eye is located on each side of the head on the top. It bulges out of the skull like this. The position of the eye and its bulged appearance gives frogs excellent peripheral vision. Which means they're able to see about 360 degrees or something that's happening behind them. The eyes are colourful and come in different patterns. The eye also allows frogs to see underwater when it is swimming. The eye is protected by a membrane called the nictitating membrane. So the ability of frogs to see colours even in the dark can be attributed to the receptors in the eye called rod cells. Even we have rod cells but the rod cells in frogs are much more sensitive than the rod cells in human eyes. The sensitive nature allows frogs to see colours even in the dark. The tympanum is the external ear of the frog. Unlike us frogs don't have external ears but they have something called the tympanum which is like a membrane. Audio signals from the environment is transmitted to the inner and middle ears by the tympanum. The long bilobed sticky tongue of frogs has taste buds. The nasal epithelium has receptors that detect odour or smell. The frog's body is covered with sensory papillae. The sensory papillae are involved in detecting touch. So far we have seen how control and coordination by sending electrical signal works. The endocrine system of frogs is involved in control and coordination by sending hormones. Endocrine hormones as you can remember are hormones that are secreted directly into the bloodstream. Like us frogs also have many endocrine organs or glands. Let's take a look at the different endocrine organs of frogs. The pituitary can be thought of as the master gland and it is located in the brain. The pituitary gland is responsible for secreting hormones involved in growth, metabolism and sexual function. The thyroid gland secretes the thyroid hormones. Now this is a very important hormone in frogs. It regulates the process of metamorphosis or the process by which tadpoles turn into adult frogs. The pancreas which is part of the digestive system of the frog secretes the insulin hormone which is needed for the cells to take up nutrients. The gonads or the male and female sex organs secret hormones that are involved in the development and production of male and female gimmicks. The adrenal glands secret hormones involved in homeostasis. So you may be wondering why are we studying all this? Why do I have to know what the frog's insides look like? Well there is a simple answer to that. By understanding how different animals look like and how their internal structures look like we can use that information to learn more about our own human body. This is especially used in the field of medical research. So what I want you to do now is make a comparison between the nervous system, sense organs and the endocrine system of frogs and us humans. What are the similarities that you can find? And what are the differences? Why do you think these similarities exist and why do you think these differences exist? Think about that.