SWOT with Narayankar

Forebrain consists of olfactory lobes, cerebrum and diencephalon.  i.   Olfactory lobes (Rhinencephalon): These highly reduced in human brain and covered by cerebrum from all sides except ventral. Each lobe consists of an olfactory peduncle and olfactory bulb. ii.  Cerebrum (Telencephalon):  a. It is a largest part of the brain, constituting about 85% of total brain.  b.It is divided into right and left cerebral hemispheres by means of a deep median, long fissure. The two hemispheres are internally connected to each other by corpus callosum .  C. The outer surface of cerebrum is called cerebral cortex , which has outer thin region composed of grey matter and the deep inner part is cerebral medulla , which is composed of white matter.  d.  The surface of each cerebral hemisphere is greatly folded by many convolutions or gyri and grooves called sulci . These greatly increase total surface area for accommo dation of the vast number of nerv

I. The study of all aspects of brain is called encephalology. ii.Cavity of medula is the 4th ventrical cavity.

a.  Cerebrospinal fluid (CSF) remains enclosed inside the ventricles due to any abnormalities in the brain like tumours, inflammation developmental malformations.  b. This interferes with the drainage of CSF from the ventricles into the subarachnoid space and, thus excess of CSF accumulates in the ventricles. c. The CSF pressure rises causing a condition called hydrocephalus. Hydrocephalus can be fatal and requires immediate treatment.

i.  Cerebrospinal fluid (CSF) is lymph like extra cellular fluid, secreted by the choroid plexuses of pia mater and ependymal cells lining the ventricles of brain and central canal of spinal cord. ii. CSF is drained from brain to the outside into the blood stream by the three openings in the roof of medulla oblongata. iii. CSF is slightly alkaline fluid with a specific gravity of 1.005.  iv. A total of 100 -120 cc of CSF is present in and around the CNS.  v. CSF is continuously generated by the ependymal cells lining the ventricles and central canal and simultaneoulsy drained out of the brain into the blood stream. Functions of CSF:   i.The meninges and CSF act as a shock absorber and protect the brain and spinal cord from mechanical injuries. ii. It also maintains constant pressure inside cranium.  iii. It helps in exchange of nutrients and wastes between blood and brain tissue.  iv. It helps in the supply of oxygen to the brain.  V. It protects the brain from desiccation.

Meninges  are the protective membranes surrounding the brain and spinal cord. They are as follows:  i. Dura mater: It is the outermost tough, non vascular, thick and fibrous meninx and is attached to the inner side of the cranium. Sub-dural space present between dura mater and arachnoid mater is filled with serous fluid ii. Arachnoid mater: It is the middle, thin and non-vascular layer of connective tissue having web like appearance. Sub-arachnoid space is present between arachnoid mater and pia mater is filled with Cerebrospinal fluid (CSF). iii. Pia mater: It is the innermost delicate, highly vascular membrane. It lies in close contact with the CNS.

I. Sympathetic Nervous System (SNS): a. It is also called thoraco-lumbar outflow. b.It originates in the thoracic and lumbar region of spinal cord (T1 to L3) and consists of 22 pairs of sympathetic ganglia which lie on a pair of sympathetic cords on lateral sides of the spinal cord. c.The pre-ganglionic nerve fibres are short and post ganglionic nerve fibres are long. d. Adrenaline and Nor-adrenaline are produced at the terminal of postganglionic nerve fibres at the effector organ: hence it is also called adrenergic fibres. e.  Sympathetic nervous system controls body activities during emergencies (fight or flight response). It has excitatory and stimulating effect on most organs of the body except on the digestive and the excretory organs.  ii. Parasympathetic Nervous System:  a.It is also called cranio-sacral outflow. b. Parasympathetic nervous system consists of the branches from the cranial (III, VII, IX, X) nerves, sacral (I, III) and spinal (V) nerves. It consists of ganglia wh

 Nervous system in humans is well developed and complex. It is classified into three parts: Central nervous system (CNS), Peripheral nervous system (PNS) and autonomic nervous system (ANS).   i. Central Nervous System: a It consists of brain and spinal cord. b. It lies along the mid dorsal axis.  C.Brain is enclosed within the brain box/cranium of the skull, whereas the spinal cord occupies the vertebral canal of the vertebral column. ii . Peripheral Nervous System (PNS):  a.It connects central nervous system to the different parts of the body having receptors and effectors. b. Depending on the connection to the CNS, the peripheral nerves are classified into afferent nerves and efferent nerves. c. Efferent nerve fibres transmit sensory impulses from the tissues or organs to the CNS whereas afferent nerve fibres transmit regulatory or motor impulses from the CNS to the various peripheral tissues and organ. iii. Autonomous Nervous System (ANS): a. It transmits impulses from CNS to the i

The choroid plexus is like a special factory in your brain that makes cerebrospinal fluid, or CSF for short. Think of CSF as the brain's natural cushioning and cleaning fluid. It's a clear liquid that surrounds your brain and spinal cord, keeping them safe from knocks and helping remove waste. The choroid plexus is made up of tiny, finger-like structures called villi. These villi are like the workers in the factory. They filter blood that flows through them and use some of its ingredients to create CSF. This CSF is then released into spaces in your brain called ventricles, and from there, it flows around your brain and spinal cord, doing its job of protecting and nourishing your nervous system. So, in simple terms, the choroid plexus is a brain factory that makes a special fluid called cerebrospinal fluid, which keeps your brain and spinal cord safe and healthy.

Lymph is a clear, watery fluid that circulates throughout your body, just like blood. It plays a crucial role in your immune system, which helps your body fight off infections and diseases. Lymph is made up of water, proteins, and white blood cells. It's produced in various tissues and organs, primarily in lymph nodes, tonsils, and the spleen. Here's how it works: 1. Collection: Lymph is collected from tissues all over your body. It picks up waste materials, bacteria, and harmful substances along the way. 2. Transport: Lymph travels through a network of vessels, much like blood vessels, called the lymphatic system. These vessels carry lymph to lymph nodes, which act as checkpoints. 3. Filtering: In lymph nodes, white blood cells check the lymph for harmful invaders. If they find any, they mount an immune response to destroy these threats. 4. Return: After filtering, lymph is returned to the bloodstream to maintain a healthy balance of fluids in your body. In simple terms, think

An aqueous solution is basically a mixture of two things: water and something else that dissolves in water. Imagine you have a glass of water, and you want to put some sugar in it. You stir the sugar into the water until it disappears completely. Now, you have a sugar-water mixture, and this is called an aqueous solution. In simple words, "aqueous" just means "in water." So when something is dissolved in water, we can call it an aqueous solution. It's like when you mix things together in water, and they become one, like sugar in water or salt in water. The water can hold onto these things and make them disappear, creating a solution.

Combustion is a chemical reaction that happens when a substance, often a fuel like wood, gasoline, or natural gas, combines with oxygen from the air and produces heat, light, and new substances. Let's break down this process step by step: 1. **Fuel**: You start with a substance called a "fuel." Fuels are things that can burn, like wood in a campfire or gasoline in a car's engine. These fuels are made up of different chemicals, and they have energy stored in them. 2. **Oxygen**: In the air around us, there is a gas called oxygen. Oxygen is essential for combustion to occur. It's like the ingredient needed for the fire to burn. When you breathe, you're using oxygen from the air to keep your body going. 3. **Ignition**: For combustion to start, you need something to heat up the fuel to a certain temperature. This can be a spark, a flame, or even just a lot of heat from the sun. Once the fuel gets hot enough, it begins to break apart. 4. **Chemical Reaction**: Whe

 When you add zinc (Zn) dust to a copper sulfate (CuSO4) solution, a chemical reaction will occur between the zinc and copper sulfate. This reaction is a classic example of a displacement or single replacement reaction. In this reaction, zinc will displace copper from copper sulfate, resulting in the formation of zinc sulfate and the liberation of copper metal.  The balanced chemical equation for this reaction is as follows: Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s) Now, let's discuss the temperature changes that may occur during this reaction: 1. **Exothermic Reaction (Heat Release):** This reaction is exothermic, which means it releases heat energy. As the zinc displaces copper from copper sulfate, chemical bonds are broken and formed. Breaking bonds requires energy, and when new bonds are formed, energy is released. In this case, more energy is released when the new bonds in zinc sulfate are formed compared to the energy required to break the bonds in copper sulfate and zinc. This r

 When limestone powder (which is primarily composed of calcium carbonate, CaCO3) is heated in an evaporating dish, several chemical reactions occur. Here's what happens: 1. **Decomposition of Calcium Carbonate**: The main reaction that takes place is the decomposition of calcium carbonate into calcium oxide (quicklime) and carbon dioxide gas. The chemical equation for this reaction is:    CaCO3(s) → CaO(s) + CO2(g)    In this reaction, heat energy is absorbed to break the bonds in calcium carbonate, resulting in the formation of calcium oxide and the release of carbon dioxide gas as a product. 2. **Formation of Calcium Oxide**: The resulting product, calcium oxide (CaO), is also known as quicklime. Quicklime is a white, caustic, and crystalline solid that has various industrial uses. 3. **Evaporation of Water**: If there is any moisture or water content in the limestone powder, it will evaporate during the heating process, leaving behind dry calcium carbonate before the decompositi

 Naphtha balls, also known as mothballs, are small, solid, white or translucent balls that are used as a pesticide and deodorant. They are primarily employed to protect clothing and other textiles from damage caused by moths and other fabric-eating insects. Naphtha balls are typically made from either naphthalene or paradichlorobenzene, two chemical compounds that release a vapor that is toxic to insects when exposed to air. Here's how naphtha balls work: 1. Insect Repellent: Naphthalene or paradichlorobenzene sublimes, which means they turn from a solid directly into a gas without becoming a liquid in between. When exposed to air, these substances release a strong odor that is toxic to moths, larvae, and other fabric-damaging insects. 2. Storage Protection: Naphtha balls are often placed in storage containers, closets, or drawers with clothing or textiles to create a protective barrier. The vapor they emit helps deter moths and other insects from laying eggs on or feeding on these

 Writing molecular formulas for different compounds involves representing the types and numbers of atoms that make up the compound. To do this, you need to follow certain requirements and rules: 1. Identify the Elements: Determine which elements are present in the compound. You can usually do this based on the chemical name or formula of the compound. 2. Determine the Ratio: Find the ratio in which these elements are combined in the compound. This is crucial for writing the correct molecular formula. 3. Use Subscripts: Write the symbols of the elements involved, using subscripts to indicate the number of atoms of each element in the compound. Subscripts are small numbers written to the right and slightly below the element's symbol. 4. Simplify the Ratio: If possible, simplify the ratio of atoms in the compound. Ensure that the subscripts represent the smallest whole number ratio of atoms. This is important because molecular formulas should not contain fractions or decimals in subsc

 Structural isomerism is a concept in chemistry where molecules with the same chemical formula have different arrangements of atoms. It's like having a set of building blocks (atoms) and arranging them in various ways to create different structures. These different structures are called isomers, and they can have distinct chemical and physical properties. Here are ten examples to illustrate structural isomerism: 1. **Butane and Isobutane:** Both have the formula C4H10, but their carbon atoms are arranged differently. Butane has a straight chain of carbon atoms, while isobutane has a branched structure. 2. **Ethanol and Dimethyl Ether:** Both have the formula C2H6O, but they have different structures. Ethanol has a hydroxyl (-OH) group attached to one of its carbon atoms, while dimethyl ether has an oxygen atom sandwiched between two carbon atoms. 3. **Propanal and Acetone:** They both have the formula C3H6O, but their structures vary. Propanal has an aldehyde functional group (-CHO

 In chemistry, a functional group is like a special team of atoms that work together to give a molecule its unique properties and reactivity. Functional groups are like the building blocks of organic compounds, which are the chemicals that make up living things and many other substances around us. Here's a more detailed explanation with 10 examples of common functional groups: 1. **Hydroxyl Group (-OH):** This group consists of an oxygen atom bonded to a hydrogen atom. It's found in alcohols like ethanol (found in alcoholic beverages) and is responsible for their ability to dissolve in water and participate in chemical reactions. 2. **Carbonyl Group (C=O):** It's a carbon atom double-bonded to an oxygen atom. In aldehydes (like formaldehyde) and ketones (like acetone), this group determines their reactivity and characteristics. 3. **Carboxyl Group (-COOH):** This group includes a carbonyl group and a hydroxyl group. It's found in carboxylic acids like acetic acid (found

Polyatomic ions might sound a bit complex, but they're actually quite simple once you break them down. 1. **Ions:** First, let's understand what ions are. Atoms are the tiny particles that make up everything around us, and they have a balance of positively charged particles (protons) and negatively charged particles (electrons). Sometimes, atoms can gain or lose electrons, which makes them either positively charged or negatively charged. These charged atoms are called ions. 2. **Polyatomic:** Now, "poly" means many, and "atomic" means related to atoms. So, a polyatomic ion is a group of two or more atoms that are stuck together and act like a single charged particle. These groups of atoms have a net positive or negative charge, just like individual ions. 3. **Examples:** Let's look at some common polyatomic ions:    - **Nitrate (NO3-):** This is a group of one nitrogen atom (N) and three oxygen atoms (O) that are bonded together with a negative charge. S

  The valency of an element is a measure of its ability to combine or bond with other elements to form compounds. It tells us how many chemical bonds an atom of that element can form when it reacts with other atoms. Here's a simple breakdown: 1. Valency depends on an element's outermost electron shell. Elements "want" to have a full outer shell of electrons because this makes them stable. 2. Elements in the same column (group) of the periodic table often have similar valencies. For example, elements in Group 1 like hydrogen and sodium have a valency of 1 because they have one electron in their outer shell, which they can easily lose to form a bond. 3. Elements in Group 2 have a valency of 2 because they need to lose two electrons to have a full outer shell. 4. Elements in Group 17 have a valency of 1 because they need to gain one electron to complete their outer shell. 5. Elements can also share electrons to achieve a full outer shell, and their valency reflects how m

  Molecules are the building blocks of matter, and they come in two main types: molecules of elements and molecules of compounds. Let's break them down in simple terms: 1.  Molecules of Elements: - These are made up of atoms of the same element bonded together. - An element is a basic substance like oxygen (O2), hydrogen (H2), or nitrogen (N2). - When two or more atoms of the same element join together, they form a molecule of that element. - For example, in oxygen gas (O2), two oxygen atoms bond together to create an oxygen molecule. 2.  Molecules of Compounds: - These are formed when atoms of different elements combine. - Compounds are substances like water (H2O), table salt (NaCl), or carbon dioxide (CO2). - In compounds, the atoms are different, and they chemically join to form molecules. - Water, for instance, consists of two hydrogen atoms and one oxygen atom bonded together (H2O). In summary, molecules of elements are made of identical atoms, while molecules of compounds are

Mitochondrion is known as the power house of the cell. It plays significant role in aerobic respiration Mitochondria are absent in prokaryotic cells and red blood corpuscles (RBCs). The structure of mitochondrion:  i. Shape of the mitochondria may be oval or spherical or like spiral strip. ii. It is a double membrane bound organelle. i. Outer membrane is permeable to various metabolites due to presence of a protein-Porin or Parson's particles. IV. Inner membrane is selectively permeable to few substances Both membranes are separated by intermembrane space. only. vi. Inner membrane shows several finger like or plate like folds called as cristae which bears numerous particles oxysomes & cytochromes/electron carrier. vii. Inner membrane encloses a cavity called inner chamber, containing a fluid-matrix. viii. Matrix contains few coils of circular DNA, RNA, 70S types of ribosomes, lipids and various enzymes of Krebs' cycle and other pathways.

Glyoxysomes are membrane bound organelles containing enzymes that convert fatty acids to sugar. They are observed in cells of germinating seeds where the cells utilize sugar (formed by conversion of stored fatty acids) till it starts photosynthesising on its own.

The organelle which helps in maintaining turgidity of the cell and a proper internal balance of cellular contents is known as vacuole.  i. The vacuoles are bound by semipermeable membrane, called tonoplast membrane. This membrane helps in maintaining the composition of vacuolar fluid (cell sap), different from that of the cytosol. ii. Composition of cell sap differs in different types of cells.  iii. In vacuoles along with excretory products other compounds are stored that are harmful or unpalatable to herbivores, thereby protecting the plants. iv. Attractive colours of the petals are due to storage of such pigments in vacuoles.  v. Generally, there are two or three permanent vacuoles in a plant cell. vi. In some large plant cells, a single large vacuole occupies the central part of the cell. It is called central vacuole. In such cells, vacuole can occupy about 90% of the total volume of the cell. vii. The cell sap of central vacuole is a store house of various ions and thus is hyperto

i. Lysosomes are considered as dismantling and restructuring units of a cell.  ii. These are membrane bound vesicles containing hydrolytic enzymes . The enzymes in lysosomes are used by most eukaryotic cells to digest (hydrolyse) macromolecules. iii. The lysosomal enzymes show optimal activity in acidic pH. iv. Lysosomes arise from Golgi associated endoplasmic reticulum. v. Lysosomes are polymorphic in nature and are classified as primary lysosomes, secondary or hybrid lysosomes, residual body and autophagic vesicle. The list of lysosomal enzymes includes: All types of hydrolases viz, amylases, proteases and lipases. Reason for been called as Suicidal bags: i. Lysosomes which bring about digestion of cell's own organic material like a damaged cell organelle are called autophagic vesicle (suicide bags). ii. An autophagic vesicle essentially consists of lysosome fused with membrane bound old cell organelle or organic molecules to be recycled. iii. Thus, lysosomes are cap

Golgi complex or Golgi apparatus or Golgi body act as a assembly, manufacturing cum packaging & transport unit of cell. i. Structure of Golgi complex: a. Golgi complex consists of stacks of membranous sacs called cisternae. b. Diameter of cisternae varies from 0.5 to 1μm. c. A Golgi complex may have few to several cisternae depending on its function. d. The thickness and molecular composition of membranes at one end of the stack of a Golgi sac differ from those at the other end. e. The Golgi sacs show specific orientation in the cell. f. Each cisterna has a forming or 'cis' face (cis: on the same side) and maturing or 'trans' face (trans: the opposite side). g. Transport vesicles that pinch off from transitional ER merge with cis face of Golgi cisterna and add its contents into the lumen. ii. Location of Golgi complex: Golgi bodies are usually located near endoplasmic reticulum. iii. Functions of Golgi complex: a. Golg

Smooth endoplasmic reticulum (SER):  i. Depending on cell type, it helps in synthesis of lipids for e.g. Steroid secreting cells of cortical region of adrenal gland, testes and ovaries.  ii. Smooth endoplasmic reticulum plays a role in detoxification in the liver and storage of calcium ions (muscle cells).  Rough Endoplasmic Reticulum (RER): i. Rough ER is primarily involved in protein synthesis. For e.g. Pancreatic cells synthesize the protein insulin in the ER. ii. These proteins are secreted by ribosomes attached to rough ER and are called secretory proteins. These proteins get wrapped in membrane that buds off from transitional region of ER. Such membrane bound proteins depart from ER as transport vesicles. iii. Rough ER is also involved in formation of membrane for the cell. The ER membrane grows in place by addition of membrane proteins and phospholipids to its own membrane. Portions of this expanded membrane are transferred to other components of endomembrane system.

i. Endoplasmic reticulum is a network present within the cytosol. ii. It is present in all eukaryotic cells except ova (female reproductive cell/egg cell)  and mature red blood corpuscles. iii. Under the electron microscope, it appears like network of membranous tubules (ERs) and sacs called cisternae. iv. This network of ER divides the cytoplasm in two parts viz. one within the lumen of ER called laminal cytoplasm and non-laminal cytoplasm that lies outside ER. v. Membrane of ER is continuous with nuclear envelope at one end and extends till cell membrane. It thus acts as intracellular supporting framework and helps in maintaining position of various cell organelles in the cytoplasm. vi. Depending upon the presence or absence of ribosomes, endoplasmic reticulum is called rough endoplasmic reticulum (RER) or smooth endoplasmic reticulum (SER) respectively.

i. The cell contains ground substance called cytoplasmic matrix or cytosol. ii. This colloidal jelly like material shows streaming movements called cyclosis. iii. The cytoplasm contains water as major component along with organic and inorganic molecules like sugars, amino acids , vitamins, enzymes , nucleotides , minerals and waste products. iv. It also contains various membrane bound cell organelles like endoplasmic reticulum, Golgi complex, mitochondria, plastids , nucleus, microbodies and cytoskeletal elements like microtubules . v. Cytoplasm acts as a source of raw materials as well as seat for various metabolic activities taking place in the cell. vi. It helps in distribution and exchange of materials between various cell organelles.

 i. Saltatory conduction is the rapid passage of action potential along myelinated nerves from one node of Ranvier to the other. ii. It occurs at the rate of 120 m/s. 9

Nerve impulses, also known as action potentials, are how our nervous system sends signals. Here's a simplified explanation of how it works: 1. **Starting the Signal:** It begins with a message, like when you touch something hot. Specialized cells called neurons detect this and decide to send a signal. 2. **Creating Electricity:** Neurons use electricity to send signals. Inside a neuron, there are ions (charged particles) that are unevenly distributed. This creates an electrical imbalance. 3. **Triggering the Action Potential:** When the neuron decides to send a signal, it opens special channels in its outer membrane. This allows positive ions like sodium (Na+) to rush into the neuron, briefly reversing the electrical charge. 4. **The Wave:** This reversal of charge is like a tiny electrical wave that travels down the neuron's long, skinny "wire" called the axon. 5. **Myelin Sheath (Optional):** Some neurons are wrapped in a fatty covering called myelin, which acts lik

1. Medullated nerve fibres have the insulating fatty myelin sheath. ii. This myelin sheath prevents the flow of ions between the axoplasm and the extracellular fluid. Thus, the transport pumps and ion gated channel operate only in the region where the myelin sheath is absent. i.e. nodes of Ranvier.

i.  The ionic gradient across the resting plasma membrane is maintained by the sodium potassium pump.  ii. Sodium potassium pump gets operated when Na + gates are closed and K + gates are open as the permeability of the membrane for Na + decreases and that for K + increases.  iii. It actively transports 3 Na + outwards for 2 K + into the cell.  iv.It is an electrogenic pump. 

i. The transmission of the nerve impulse along the long nerve fibre/ axon tube is a result of electrical changes across the neuronal membrane during conduction of an impulse.  ii. Each neuron has a charged cellular membrane with a voltage which is different on the outer and inner side of the membrane. iii. The resting nerve remains in a polarised state by maintaining an excess of Na + on the outer side, whereas on the inner side there is an excess of K +along with large negatively charge protein molecules and nucleic acid.  iv. Application of stimulus on the resting nerve results in the increased permeability of the membrane to Na+. Ca+ rush into the axon from the extracellular fluid (ECF) and bring about depolarisation. V. The membrane potential changes from -70 my (resting potential) to about +30 mV to +60 mV (action potential). Vi. Depolarisation is now triggered in the next part while the initial part itself starts undergoing repolarisation. vii. After a short interval

i. Chemical synapse between a motor neuron and a muscle cell is called a neuromuscular junction. It has three components - the pre-synaptic terminal (mostly axonic terminal), the synaptic membrane of the post synaptic cell (usually on the dendrite of the next neuron/gland cell/ muscle) and the post synaptic neuron.  ii. The impulse travels along the axon of the pre-synaptic neuron to the axon terminal. Pre-synaptic neurons have several synaptic knobs at their ends. These synaptic knobs have synaptic vesicles that contain neurotransmitter molecules. iii. When an impulse reaches the synaptic knob, voltage sensitive Ca ++channels open and the Call++ ions diffuse inward from the extracellular fluid.  iv. Increase in level of calcium ion concentration inside the cells initiates a series of events that fuse synaptic vesicles with the cell membrane of pre-synaptic neuron, where the neurotransmitters are released by exocytosis. V. The released neurotransmitters bind to the receptors of the pos

i. Synapse is a junction between two nerve cells with a minute gap (synaptic cleft) in between them which allows transmission of impulse by a neurotransmitter bridge.  ii. It is point where the neurons communicate with one another.  iii. A synaptic cleft or a small intercellular space lies in between two cells having a width about 20-30 nm between them. iv. Electrical synapse and chemical synapse are the two types of synapses:   a. Electrical synapse: In this type of synapse, the gap between the neighbouring neurons is narrow. The synapse between such closed neurons is 6mechanical. eoAn electrical conductive link is formed between the pre and post synaptic neurons. At the gap junction, the two cells are within almost 3.8 mm distance of each other. Transmission across the gap is faster but depends on the connection located at the gap junctions between the two neurons. Electrical synapses are found in parts of body which require producing fastest response. e.g. Defence reflexes. They

 Ligand gated ion channel is responsible for the transmission of impulse.

a. When a neuron receives an impulse, it passes it to the next neuron. The impulse travels along the axon of the pre-synaptic neuron to the axon terminal. b. Pre-synaptic neurons or aXons have synaptic knobs at their ends or terminals. These synaptic knobs have synaptic vesicles which contain neurotransmitter molecules.  C. When the impulse reaches a synaptic knob, Ca channels open and Ca ions diffuse inward from the extracellular fluid. d. This causes release of neurotransmitters which bind to the receptors of the post synaptic cell.  e. The neurotransmitter is destroyed by the enzyme cholinesterase. A new impulse/ next impulse is generated and conducted to the synaptic gap.

Neurotransmitter is released by the process of exocytosis.

Synaptic vesicles molecules. contain neurotransmitter

The process by which the impulse from the pre synaptic neuron is conducted to the post synaptic neuron or cell is called synaptic transmission. It is a one way process carried out by neurotransmission.

Excitability/Irritability : Nerve fibres have polarized membrane, thus they have the ability to perceive stimulus and enter into a state of activity.

The ratio of neuroglia to neuron is less than 1:1 (calculated by recently validated isotropic fractionator - counting method) The total number of glial cells in the human brain is less than 100 billion, while the number of neurons in the brain is around 86 billion.

i. Blood brain barrier prevents the passage of ions and large molecules from the blood into the brain tissue. ii. The endothelial cells lining the blood capillaries and astrocytes help in this process. ENRICH YOUR KNOWLEDGE  The blood-brain barrier (BBB) protects brain cells i from harmful substances and pathogens by preventing passage I of many substances from blood into brain tissue. The blood-brain barrier consists mainly of tight junctions that seal together the endothelial cells of 1 brain capillaries, along with a thick basement membrane around the capillaries. The processes of many astrocytes, press up against the capillaries and secrete chemicals that maintain the permeability characteristics of the tight junctions 

i. Pre-synaptic neurons - The neuron carrying an impulse to the synapse is called the pre-synaptic neuron. ii. Post synaptic neuron - The neuron receiving input at the synapse is the post synaptic neuron. iii. Synaptic cleft - The intercellular space between two nerve cells.

i. Excitability/Irritability: Nerve fibres have polarised membta, thus they have the ability to perceive stimulus and enter into a state of activity. ii. Conductivity: It is ability of nerve to transmit impulses along the whole length of axon.  iii. Stimulus: It is any detectable, physical, chemical, electrical change in the external or internal environment which brings about excitation in a nerve/muscle/organ/organism. A stimulus must have a minimum intensity called threshold stimulus, in order to be effective. Subliminal (weak) stimulus will have no effect while supraliminal (strong) stimulus will produce the same degree of impulse as the threshold stimulus. iv. Summation effect: A single subliminal stimulus will have no effect but when many such weak stimuli are given again and again they may produce an impulse due to summation of effects. V. All or none law: The nerve will either conduct the impulse along its entire length or will not conduct the impulse at all (this occurs in ca

Fluid Mosaic Model: i. Fluid mosaic model was proposed by Singer and Nicholson (1972). ii. This model states that plasma membrane is made up of phospholipid bilayer and proteins. iii. Proteins are embedded in the lipid membrane like icebergs in the sea of lipids. iv. Phospholipid bilayer is fluid in nature. v. Quasi-fluid nature of lipid enables lateral movement of proteins. This ability to move within the membrane is measured as fluidity vi. Based on organization of membrane proteins they are of two types, as: a. The intrinsic proteins occur at different depths of bilayer i.e. they are tightly bound to the phospholipid bilayer and are embedded in it. They span the entire thickness of the membrane. Therefore, they are known as transmembrane proteins. They form channels for passage of water. b. The extrinsic or peripheral proteins are found on two surfaces of the membrane i.e. are loosely held to the phospholipid layer and can be easily removed.

Eukaryotic plasma membrane/ Cell membrane/ Biomembrane: i. It is thin, quasi-fluid structure present both extracellularly and intracellularly.  ii. Extracellularly, it is present around protoplast and intracellularly, it is present around most of the cell organelles in eukaryotic cell. It separates cell organelles from cytosol.  iii. Thickness of bio-membrane is about 75Å. iv. Cell membrane appears trilaminar (made up of three layers) when observed under electron microscope. It shows presence of lipids (mostly phospholipids) arranged in bilayer. v. Lipids possess one hydrophilic polar head and two hydrophobic non-polar tails. Therefore, phospholipids are amphipathic. vi. Lipid molecules are arranged in two layers (bilayer) in such a way that their tails are sandwiched in between heads. Due to this, tails never come in direct contact with aqueous surrounding.  vii. Cell membrane also shows presence of proteins and carbohydrates. viii. Ratio of proteins and lipids varies in different cel

i. Middle lamella: It is thin and present between two adjacent cells. It is the first structure formed from! cell plate during cytokinesis. It is mainly made up of pectin, calcium and magnesium pectate. Softening of ripe fruit is due to solubilization of pectin. ii. Primary wall: In young plant cell, it is capable of growth. It is laid inside to middle lamella. It is the only wall seen in meristematic tissue, mesophyll, pith, etc. iii.  Secondary wall: It is present inner to primary wall. Once the growth of primary wall stops, secondary wall is laid. At some places thickening is absent which leads to formation of pits.

Groups and electronic configuration: Characteristics of the Groups and Periods: Various properties of all the elements in a group show similarity and gradation. However, the properties of elements change slowly while going from one end to the other (for example, from left to right) in a particular period.  • The number of valence electrons in all these elements from the group 1, i.e. the family of alkali metals, is the same. Similarly, the element from any other group, the number of their valence electrons to be the same. For example. the elements beryllium (B9), , magnesium (Mg) and calcium (Ca) belong to the group 2, i.e. the family of alkaline earth metals. • There are two electrons in their outermost shell the number of valence electrons are 2. Similarly, there are seven electrons in the outermost shell of the elements such as fluorine (F) and chlorine (CI) from the group 17, i.e. the family of halogens. • While going from top to bottom within any group, one electronic shell gets a

Modern Periodic Table and electronic configuration of the elements : The characteristics of the groups and periods in the modern periodic table are because of electronic configuration of the elements. • It is the electronic configuration of an element which decides the group and the period in which it is to be placed. • The neighbouring elements within a period differ slightly in their properties while distant elements differ widely in their properties. • Elements in the same group show similarity and gradation in properties.

Structure of the Modern Periodic Table • In the modern periodic table, the elements are arranged in the order of their increasing atomic numbers. There are seven horizontal rows called periods 1 to 7. There are eighteen vertical columns called groups 1 to 18. The arrangement of the periods and groups results into formation of boxes. Atomic numbers are serially indicated in the upper part of these boxes. Each box corresponds to the place for one element. There are two series of elements placed separately at the bottom of the periodic table. These are called lanthanide series and actinide series. There are 118 boxes in the periodic table including the two series. • The elements in the modern periodic table are divided into four blocks: the s-block, the p-block, the d-block and the f-block. The groups, 1 and 2 together with hydrogen form the s- block elements. The groups 13 to 18 form the p-block elements. The groups 3 to 12 together form the d- block elements. The two series (the lanthan

Modern Periodic Law: After the discovery of electron, scientists started exploring the relation between the electron number of an atom and the atomic number. The atomic number in Mendeleev's periodic table only indicated the serial number of the element. Henry Moseley showed that the atomic number of an element is the most fundamental property and not its atomic mass. Accordingly Mendeleev's Periodic law was modified into Modern Periodic law and it can be stated as: The chemical and physical properties of elements are a periodic function of their atomic numbers.

General characteristics of prokaryotic cells: i. Prokaryotic cells are primitive type of cells. ii. It does not have membrane bound cell organelles (like endoplasmic reticulum, Golgi complex, mitochondria, etc.) and well-defined nucleus (nuclear membrane is absent).  iii. Genetic material is in the form of nucleoid. iv. Cell envelope       a. Prokaryotic cell has chemically complex protective cell envelope having glycocalyx, cell wall & plasma membrane.       b. In some bacteria, glycocalyx occurs in the form of a slime layer (loose sheath). Other bacteria have a thick and tough covering called capsule. It helps in protection of bacterial cell.  v.  Cell Wall The Gram-positive bacteria show presence of peptidoglycan layer in the cell wall and Gram-negative bacteria show presence of murein in the cell wall. It gives mechanical strength to the cell. Note: In Gram-negative bacteria, cell wall is made up of two layers; inner layer of Murein peptidoglycan and outer layer of Lipopolysacc

i.Totipotency (totus entire, potential power) is the capacity or the potential of living nucleated differentiate into any other type of cell and thus, can form a complete new organism.  ii. A cell is totipotent as it has the entire genetic information of the organism stored in its nucleus. iii.Embryonic animal cells are totipotent and are termed as stem cells. Stem cells are used in curing many diseases. Therefore, they have great potential for medical applications.

i. The rigid, protective and supportive covering, outside the cell membrane is called cell wall. It is present in plant cells, fungi and some protists. ii.Algae show presence of cellulose, galactans, mannans and minerals like calcium carbonate in cell wall. iii.In other plants, it is made up of hemicelluloses, pectin, lipids and protein.  iv. Microfibrils of plant cell wall show presence of cellulose which is responsible for rigidity. v. Some of the depositions of cell wall are silica (grass stem), cutin (epiderma walls of land plants), suberin(endodermal cells of root), wax, lignin. vi. Function: Provides support, rigidity and shape to the cell. Protects the protoplasm against mechanical injury and infections.

i. Eukaryotic cells are the cells possessing well-defined nucleus and membrane bound organelles (like mitochondria, endoplasmic reticulum, ribosomes, Golgi complex etc.).  ii. Eukaryotes include protists, plants, animals and fungi.

Demerits of Mendeleev's Period  • The elements cobalt (Co) and nickel (Ni) have the same whole number atomic mass. As a result there was an ambiguity regarding their sequence in Mendeleev's periodic table. • Isotopes were discovered long time after Mendeleev put forth the periodic table. A challenge was posed in placing isotopes in Mendeleev's periodic table as isotopes have the same chemical properties but different atomic masses. • The rise in atomic mass does not appear to be uniform when elements are arranged in an increasing order of atomic masses. It was not possible, therefore, to predict how many elements could be discovered between two heavy elements. • Position of hydrogen : Hydrogen shows similarity with halogens (group VII). For example, the molecular formula of hydrogen is H, while the molecular formulae of fluorine and chlorine are F, and Cl2 In the same way, there is a similarity in the chemical properties of hydrogen and alkali metals (group I). There is a s

Merits of Mendeleev's periodic table: • To give the proper place in the periodic table, atomic masses of some elements were revised in accordance with their properties. • For example, the previously determined atomic mass of beryllium, 14.09, was changed to the correct value 9.4, and beryllium was placed before boron. • Mendeleev had kept some vacant places in the periodic table for elements that were yet to be discovered. • Three of these unknown elements were given the names eka-boron, eka-aluminium and eka-silicon from the known neighbours and their atomic masses were indicated as 44, 68 and 72, respectively. Their properties were also predicted. • Later on these elements were discovered subsequently and were named as scandium (Sc), gallium (Ga) and germanium (Ge) respectively. The properties of these elements matched well with those predicted by Mendeleev. • Due to this success all convinced about the importance of Mendeleev's periodic table. • When noble gases such as heli