Glossary of Control and Coordination

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 7. Control and Coordination  

Abscisic Acid  

A plant hormone which inhibits growth and is responsible for the wilting of the leaves and seed dormancy and germination.

Adrenal Gland  

The gland which secrets the adrenalin hormone, which is responsible for the regulation of proper cardiovascular functions

Auxin 

 A plant hormone which promotes stem elongation, growth and movement. It is produced in the stem, roots and buds. 

Axon  

A long tube which carries electric signals from a cell body to other cells

Cell Body  

Central Nervous System  

Cerebrum  

Chemotropism  

Cytokinins  

Dendrites  

Endocrine System  

Ethylene  

Forebrain  

Geotropism  

Germination  

Gibberellins  

Gustatory Receptors  

Hindbrain  

Hydrotropism  

Hypothalamus  

Insulin  

Midbrain  

Neurons  

Nucleus

Oestrogen  

Olfactory Receptors  

Pancreas  

Parathyroid Gland  

Peripheral Nervous Syste  

Phototropism  

Pineal Gland  

Pituitary Gland  

Reflex Action  

Reflex Arc  

Spinal Cord  

Synapse  

Testosterone  

Thigmotropism  

Thymus  

Thyroxin  

Tropism

7. Control and Coordination  

Nervous System  

Nervous System  

Our nervous system is broken up into the Central nervous system and Peripheral nervous system which are further divided into different parts, each performing specific functions.

Central Nervous System: Consisting of the brain and spinal cord, it is the system which processes all information received from the body's organs and determines appropriate responses.

Peripheral Nervous System: All nerves in the body with the exception of those in the brain and spinal cord. It connects the central nervous system to the organs, limbs, and skin.

Neurons 

 Neurons  

Nerve cells or Neurons are the basic building blocks of our nervous system. They are responsible for transmitting and receiving signals from different parts of the body. Following are the parts of neurons:

Dendrites: These are tree like extensions which receive information from a body part or other neurons and transmit electric signals to the cell body.

Cell body: Also known as soma, it controls all the functions of the cell via a number of important organelles that are a part of the cell body, including the nucleus.

Nucleus: Nucleus is the most important cell organelle that contains DNA, which controls the cell's growth and reproduction and contains all hereditary information of the cell.

Axon hillock:  It is the part of the cell body that processes signals received from various neurons and determines the cell’s chemical impulse in response to these signals.

Axon: A long tube which carries electric signals from a cell body to other cells.

Myelin sheath: It is made up of proteins and fats and is responsible for the protection and insulation of neurons.

Synaptic terminals: These are the terminal buttons which are located at the end of the neuron and are responsible for sending the signal on to other neurons.

Synapse: It is a small gap at the end of a neuron that allows information to pass from one neuron to the next muscle or gland.

Taste and Smell Receptors 

 Taste and Smell Receptors  

There are specialized receptors present in the neurons of the sense organs which detect information from the environment. Two such receptors are: gustatory receptors and olfactory receptors.

Gustatory Receptors: Present in the taste buds, they detect five types of taste sensations: bitter, sour, salty, sweet and fatty (or umami).

Olfactory Receptors: The part of the sensory system which sense smell. They are present in large numbers in a small area at the back of the nasal cavity.

Reflex Action  

Reflex Arc  

All reflex actions are controlled by reflex arcs. Here is an example of how the reflex arc works:

Step 1: A person touches a hot object with their fingers.

Step 2: The pain receptors in the fingers get stimulated.

Step 3: Sensory neurons carries the signal to the spinal cord.

Step 4: The signal is passed through relay neurons and sent to the brain.

Step 5: The response signal is sent through motor neurons.

Step 6: The effector muscle contracts, to pull the hand away from the hot object and prevent it from burning.

Reflex Action  

A reflex action is a rapid automatic action by the body in response to a stimulus, where the stimulus is involuntary and not controlled by the brain. 

Spinal Cord  

Spinal Cord  

The Spinal cord is a long, thin pathway that consists of nerves which carry signals between the brain and rest of the body. It is 45 cm long in men and around 43 cm in women. It is protected by 26 back bones called vertebrae.

Parts of Human Brain 

 Parts of Human Brain  

The major parts of brain are forebrain, midbrain and hindbrain.

Forebrain: It controls all the emotions, speech and movement by controlling the sensory organs.

Midbrain: It coordinates all the messages going in and out of the brain. It controls the auditory and visual systems.

Hindbrain: It controls various involuntary functions of the body such as breathing, blood circulation, salivation, sleep, sensory analysis, regulation of movement, posture and balance.

Plants Response to Stimulus 

 Plants Response to Stimulus  

The phenomenon by which the plants respond to different environmental factors showing growth or movement is known as Tropism. It is positive if response is towards the stimulus and negative if response is away from the stimulus.

Following are different types of tropism:

Phototropism: Movement or growth of an organism that is a response to the presence of light.

Geotropism: Movement or growth of an organism that is a response to the force of gravity.

Hydrotropism: Movement or growth of an organism that is a response to the presence of moisture.

Chemotropism: Movement of growth of an organism that is a response to chemical stimulus.

Thigmotropism: Movement or growth of an organism in response to touch.

Plant Hormones  

Plant Hormones  

Plants consist of various hormones that help them in growth, movement, sensing light, triggering flower development germination, and forming lateral roots. Some important hormones are:

Auxins: They promote stem elongation, growth and movement and are produced in the stem, roots and buds.

Cytokinins: They promote cell division and are produced in the roots, embryos and fruits.  They require the auxins to function properly. If there are more cytokinins than auxins, shoots are formed and if there are less cytokinins than auxins, roots are formed.

Gibberellins: They are growth hormones which are produced in stems, fruits and seeds. They promote growth and development processes such as germination, dormancy, flowering and stem elongation.

Abscisic acid:  A plant hormone which inhibits growth and is responsible for the wilting of the leaves and seed dormancy and germination. It also plays an important role in drought tolerance. When the availability of water is insufficient for a plant, the abscisic acid hormone closes the stomata to prevent water loss.

Ethylene: Ethylene helps the fruits ripen by making them softer and sweeter.  It is a gas which is distributed through the air.

Human Endocrine System

Human Endocrine System  

In the human body, hormones are released by the endocrine glands.

Pituitary (Growth hormone): The hormone that affects growth and development. It stimulates protein production and affects fat distribution

Pineal (Melatonin hormone):  The human gland that produces melatonin, the hormone that controls sleep cycles

Hypothalamus: The human gland which maintains the internal balance of the body such as heart rate, blood pressure and temperature

Thyroid (Thyroid hormone): Affects growth, maturation, nervous system activity and metabolism

Parathyroid (Peptide parathyroid hormone): Regulates calcium levels in the body

Thymus (Thymosin): The gland which secretes the thymosin hormone, which is responsible for developing a healthy immune system

Adrenal (Adrenalin hormone):Regulates cardiovascular functions

Pancreas (Insulin hormone): A hormone secreted by the pancreas, which regulates blood glucose levels

Testes (Testosterone hormone): Also known as androgens; Regulates the production of sperm, as well as the growth and maintenance of the male sexual organs

Ovaries (Estrogen hormone): Regulates the menstrual cycle and the development of the mammary glands and other female sexual organs