Thursday, September 17, 2020


Grafting is a technique that joins two plants into one. In general, a wound is created on one of the plants, and the other is inserted into that wound so each plant's tissues can grow together. 

Instead of cross-pollinating two plants and producing a hybrid seed, grafted plants use the roots and the bottom portion of one plant (rootstock) and attach it to a tender shoot (scion) from the top portion of another plant. This is often done with trees and shrubs to combine the best characteristics of the two plants.

The Rootstock or stock: The lower plant portion used in grafting is called the rootstock. This is usually a healthy root system and some portion of the stem. You've probably seen a nubby bump at the base of rose bushes or fruit trees, like the one in the photo. This is where the graft was made; the graft union. Everything below the bump is rootstock.

Whip Grafting : Whip Grafting is one of the oldest methods of asexual plant propagation known. It is the predominant propagation method used on apples and is widely used on pear. Although most grapes are grown from cuttings in this country, whip grafting is the standard when they are propagated. Whip grafting has been the primary method employed in propagating pecan nursery stock in the southeastern United States. This technique is also used to some extent in the Southeast and west to Louisiana for top-working larger pecan trees on the above-ground portions. Since successful whip grafting is closely correlated to the presence of high humidity, this method has not been used widely in the drier sections of Oklahoma, New Mexico and Texas. A major strong point for whip grafting nursery stock is the smooth and straight trees that are produced by this method.

Cleft grafting:A cleft graft is one of the grafts used for topworking new cultivars on existing trees.

It is used for relatively small branches and done when the stock is dormant and cracks easily.

Two scions are inserted on either side of the branch and the cambium lined up along the outer edge.

When the tool is released, the pressure of the closure holds the scions in place.

Once the graft takes, only one of the scions will be retained.

Sometimes the other scion is left for a while as a nurse branch

Monday, September 14, 2020

Glandular System

The system which comprises all glands of a body is called glandular system. When we see sour food a fluid is generated inside mouth, why? The salivary gland produce salivary juice. When dust enters into eye it starts tearing because of production of tear from tear gland.

Gland: those organs which produce enzyme or hormone are called glands. Glands are divided into two types exocrine and endocrine.

1. Exocrine gland: The ducted glands are called exocrine glands. The juice produced by exocrine glands are called enzymes. The enzyme produced by them is mixed to the blood which is helpful in digestion. Tear gland, sweat gland, salivary gland etc are example of exocrine glands.

2. Endocrine gland: The ductless gland that produce hormones are called endocrine glands. As hormones excite cells and other glands they are called chemical messengers. Imbalance of hormones in body causes imbalance in growth and developments.

Difference between exocrine and endocrine glands

Exocrine Gland

Endocrine Gland

1. It is ducted

1. It is ductless

2. It produces enzyme

2. It produces hormone

3. It sends enzyme to destination via duct

3. It sends hormones to blood directly

4. Enzyme is important for digestion, respiration and other life process

4. Hormone is important for growth and development

Pituitary Gland: The pituitary gland is a small pea-sized gland that plays a major role in regulating vital body functions and general wellbeing. It is referred to as the body's 'master gland' because it controls the activity of most other hormone-secreting glands. The hormones produced by this gland are called stimulating hormone and growth hormone. The major function of these hormones is physical and psychological development.

Thyroid Gland: The thyroid is a small, butterfly-shaped gland located at the base of our neck just below the Adam’s apple. It’s part of an intricate network of glands called the endocrine system. The endocrine system is responsible for coordinating many of our body’s activities. The thyroid gland manufactures hormones that regulate our body’s metabolism. The hormone produced by thyroid gland is called thyroxin which contains iodine necessary to our body. Lack of this hormone causes less sweating, physical as well as mental disability etc. If this hormone exceeds limit excess of sweating, increase of hunger, loss of weight like effects are seen.

Parathyroid gland: Parathyroid glands are four small glands of the endocrine system which regulate the calcium in our bodies. Parathyroid glands are located in the neck behind the thyroid where they continuously monitor and regulate blood calcium levels. The hormone produced by this gland is called parathermone or parathyroid hormone. It regulates calcium on blood and bones. Excess of this hormone causes tumor and kidney stone while lack of this causes lack of calcium in blood. Due to this muscles get contracted and the condition is called tetany.

Adrenal gland: The adrenal glands are small glands located on top of each kidney. They produce hormones that we can't live without, including sex hormones and cortisol. Cortisol helps us respond to stress and has many other important functions. Another hormone produced by adrenal gland is adrenalin. Access of adrenalin causes increase of blood pressure and lack of this causes decrease in blood pressure level, decrease of sugar level and dizziness.

Pancreas: The pancreas is an organ located in the abdomen. It plays an essential role in converting the food we eat into fuel for the body's cells. The pancreas has two main functions: an exocrine function that helps in digestion and an endocrine function that regulates blood sugar. So it is also called mixed gland or dual gland as it produces enzyme and hormone both. Pancreas produces Insulin and glucagon hormones. Insulin regulates sugar level in blood. Lack of insulin increases sugar level which is called diabetes.

Gonads: gonad, sex gland, or reproductive glandis a mixed gland that produces the gametes (sex cells) and sex hormones of an organism. In the female of the species the reproductive cells are the egg cells, and in the male the reproductive cells are the sperm. The male gonad, the testicle, produces sperm in the form of spermatozoa. The female gonad, the ovary, produces egg cells. Both of these gametes are haploid cells. 

Sunday, September 13, 2020

Peripheral Nervous System

The peripheral nervous system (PNS) consists of all the nerves branching out of the brain and spinal cord. If you imagine the Central Nervous System as the main highway, then the Peripheral Nervous System forms all the connecting secondary roads. These allow electrical impulses to travel to and from the furthest regions, or periphery, of the human body. The PNS is built almost entirely from nerves. There are two main types; spinal nerves and cranial nerves. Functionally, the PNS can be divided into the autonomic and somatic nervous systems. Both of these can be further subdivided; the former into sympathetic and parasympathetic arms and the latter into sensory and motor divisions.

Cranial nerve tissue:  The nerve tissues starting from brain and again ending to brain are called cranial nerve tissues. There are 12 pairs of cranial nerves emerging from brain which collect information from the organs of head like eye, ear, tongue, nose etc.

Spinal nerve tissue: The nerve tissues emerging from spinal cord and spread to different parts of body are called spinal nerves. There are 31 pairs of spinal nerves emerging from spinal cord and spread to different parts of body. They carry information and emotions from different parts of body to brain and brain to different parts of body.

Autonomic nervous system: The autonomic nervous system is a control system that acts largely unconsciously and regulates bodily functions, such as the heart rate, digestion, respiratory rate, pupillary response, urination, and sexual arousal. Autonomic nervous system is divided to two types

1. Sympathetic: this increases the rate of heartbeat, blood pressure, breathing and function of stomach, intestine and urinary system.

2. Parasympathetic: It is opposite of sympathetic which normalizes the events mentioned above in general conditions such as heart beat, blood pressure, urination rate etc.

Reflex Action and Reflex Arc

When you touch a hot object or when a pin pricks your finger, what is your immediate reaction? Of course, you remove your hand away from the source of pain, either the hot object or the pin. In situations like these, your reactions are always immediate, involuntary and sudden. They happen without much of a thinking process. In scientific terms, this action is called the reflex action. Here the spinal cord has a major role to play.  The reflex arc shows the pathway through which the reflex action occurs.

The whole mechanism of reflex action occurs in such a fashion that there is no conscious control of the brain. Stimulation occurs through the peripheral nervous system and the response to this peripheral nerve stimulation is involuntary. In a reflex action, the spinal cord along with the brain stem is responsible for the reflex movements.

A few examples of reflex action are:

·         When light acts as a stimulus, the pupil of the eye changes in size.

·         Sudden jerky withdrawal of hand or leg when pricked by a pin.

·         Coughing or sneezing, because of irritants in the nasal passages.

·         Knees jerk in response to a blow or someone stamping the leg.

·         The sudden removal of the hand from a sharp object.

·         Sudden blinking when an insect comes very near to the eyes.

The whole process of reflex action involves some important components. They are receptor organs, sensory neurons, nerve center, associated neurons, motor neurons and effector neurons.

The receptor organs perceive the stimuli. They are situated on the sense organs. The afferent neurons or the sensory neurons carry the stimuli from receptors to the spinal cord. The ganglion of the spinal cord has the sensory neurons.

The spinal cord is the nerve center, where synaptic connections are formed. The associated neurons are present in the spinal cord. The ventral horn of spinal cord has the motor neurons. Effector organs are the glands and muscles that behave in response to the stimuli.


Neuron: The smallest unit of nervous system is called neuron. It is also called nerve cell. Neurons are cells within the nervous system that transmit information to other nerve cells, muscle, or gland cells. Most neurons have a cell body, an axon, and dendrites. The cell body contains the nucleus and cytoplasm. The axon extends from the cell body and often gives rise to many smaller branches before ending at nerve terminals. Dendrites extend from the neuron cell body and receive messages from other neurons. Synapses are the contact points where one neuron communicates with another. The dendrites are covered with synapses formed by the ends of axons from other neurons.

The cell body contains the nucleus and cytoplasm. The axon extends from the cell body and often gives rise to many smaller branches before ending at nerve terminals.

Dendrites extend from the neuron cell body and receive messages from other neurons. Synapses are the contact points where one neuron communicates with another. The dendrites are covered with synapses formed by the ends of axons from other neurons.

When neurons receive or send messages, they transmit electrical impulses along their axons, which can range in length from a tiny fraction of an inch (or centimeter) to three feet (about one meter) or more. Many axons are covered with a layered myelin sheath, which accelerates the transmission of electrical signals along the axon. This sheath is made by specialized cells called glia. In the brain, the glia that make the sheath are called oligodendrocytes, and in the peripheral nervous system, they are known as Schwann cells. The brain contains at least ten times more glia than neurons. Glia perform many jobs. Researchers have known for a while that glia transport nutrients to neurons, clean up brain debris, digest parts of dead neurons, and help hold neurons in place. Current research is uncovering important new roles for glia in brain function.


Nervous System

The system of organs and cells that make organism able to detect changes within themselves and their environment is called nervous system. Changes in the external environment include those of lighttemperaturesound, motion, taste and odour, while changes in the internal environment include those in the position of the head and limbs as well as in the internal organs. Once detected, these internal and external changes must be analyzed and acted upon in order to survive. Human nervoous system is divided to three major parts, they are,

  1. Central nervous system
  2. Peripheral nervous system
  3. Autonomic nervous system
1. Central nervous system consists of brain and spinal chord.

Brain: Brain is the largest part of central nervous system situated safe inside skull. Brain is covered by three layered membrane called meninges that help protect the brain. The three layers are called duramater, piamater and arachnoid. Duramater is attached to inner skull, piamater is attached to brain and space between arachnoid and piamater is filled with a fluid called cerebrospinal fluid. This fluid protects brain from shocks. Brain is divided into three major parts

a. Cerebrum: cerebrum occupies about 80% of brain volume. It is spread from frontal, parietal to occipital zone. It is divided to left and right hemisphere lobes. The left and right hemispheres are divided from top side by deep fissure. Outer part of cerebrum is made up of grey matter and inner part from white matter. Major function of cerebrum are

  • To detect odor
  • To control speech
  • Record memory and events
  • Hearing control
  • Detect sensation like touch, pain, pressure, temperature etc
  • Thought control
  • Analysis
  • Emotions
  • Anger control
  • Future telling

Shock or wound on cerebrum causes person to coma.

b. Cerebellum: Cerebellum also called small brain is situated behind cerebrum and above medulla oblongata. It is divided to two hemispheres on the size of lemon each. It is also formed by grey matter and white matter. The major functions of cerebellum are

  • Plays the role of body balance
  • Decides the tone of muscle
  • Controls voluntary movements

c. Medulla oblongata: it is situated below cerebellum and at the top of spinal cord. It is smallest part of

brain. It is cylindrical in shape. Shock or wound on this may cause death of person. It is also made by gray matter and white matter. The major functions of medulla oblongata are

  • Control of sneezing, swallow of food
  • Control of vomiting and to cough
  • Control of breathing
  • Control contraction and relaxation of blood vessels
  • Contraction and relaxation of digestive canal
  • secretion of digestive juice, secretion of hormones etc

Spinal cord: spinal cord is a long nervous tissue which starts from lower part of medulla oblongata to the end of lumbar vertebrae.  Its outer part is made up of white matter and inner part from grey matter. It is covered by meninges. If spinal cord gets shock or injured the lower part below wound remain paralyzed which is called spinal injury or spinal paralysis. Main functions of spinal cord are

  • It is the centre of reflex action. It shows instant reaction to change in outer environment
  • Establishes relationship between different parts of body and brain
Next: Peripheral Norvous System and autonomic nervous system