Biology Notes

Neurotransmitters and receptors Did you know there are billions of neurons—and trillions of synapses—in your amazing brain? ^1 1 start superscript, 1, end superscript  (No wonder you can learn anything, including neurobiology!) Most of your synapses are  chemical synapses , meaning that information is carried by chemical messengers from one neuron to the next. In the article on synapses, we discussed how synaptic transmission works. Here, we’ll focus on  neurotransmitters , the chemical messengers released from neurons at synapses so that they can “talk” to neighboring cells. We’ll also look at the receptor proteins that let the target cell “hear” the message. Neurotransmitters: Conventional and unconventional There are many different kinds of neurotransmitters, and new ones are still being discovered! Over the years, the very idea of what makes something a neurotransmitter has changed and broadened. Because the definition has expanded, some recently discovered n

Excretion in Invertibrate Excretion in Planaria Habitat : Planaria is a fresh water invertebrate.   Excretory product: planaria remove ammonia and it is ammonotlic. This excretion occurs by two methods, diffusion, specialized excretory system. Excretory organs: Planaria has simple tubular excretory system called protonephiridia. Protonephridia arranged in two longitudinal trunk one on each side of the body. Each track consists of a network of tubules without internal openings. These tubules divide into small branches which open in flame cells. Tubules open on the outside by small opening called nephridiophores. Structure of flame cell: Flame cells are club shaped hollow cells. Each flame cell contains nucleus, cytoplasm and internal cavity. Group of cilia is present in the cavity. Cilia perform a movement like a flame of candle. Flame cells also has many cytoplasmic elongations. Mechanism of excretion: Flame cells absorb wastes and push them into the cavit

Nitrogenous Wastes Of Animal: Waste Products Of Animals: The nitrogenous wastes are urea,ammonia and uric acid . These all wastes are not removed by the same animal. These wastes are produced and excreted by different animal which are living in different habitats. The type of nitrogenous waste and their excretion depend upon the habitat of an animal. 1.Ammonia (NH3): It is the excretory product of aquatic animals ,developes by the break down of amino acids,harmful to the living cells,excreted by diffusion and highly soluble in water. About 500 ml of water is needed to remove one gram of ammonia . Animals those excrete ammonia are called ammonotelic . Examples: Eartworm, protozians, sponges and fishes etc. 2.Urea {CO (NH2)2}: It is the excretory products of mostly land animals ,produced by the liver from ammonia,less toxic than ammonia and can be store in the body for short time. One gram of urea require 50 ml of water for excretion. Animals those remove urea are