Introduction
As the complexity of the individuals, plants or animals increases the different cells and organs become separated from each other by greater distance.
Nervous Control in Human Beings - Nervous System
It stores the previous experiences as memory that helps us to think and analyse our reactions.It conducts messages between different parts of the body.
Units of Nervous System
The units of nervous system are specialised cells called the neurons.
Transmission of Messages
The messages are transmitted in the form of electrical impulses along the fibres of the neurons.
Types of Nerves
Nerves are of three types based on the types of neurons they carry.
Receptors and Effectors
Receptors are structures at the ends of the nerve fibres that collect the information to be conducted by the nerves.
Parts of the Nervous System - Central Nervous System
The human nervous system can be divided into three main parts:Central nervous system, Peripheral nervous system, Autonomic nervous system.
Parts of the Nervous System - Peripheral Nervous System
The peripheral nervous system is made up of nerves that connect the different parts of the body (peripheral tissues) to the central nervous system.
Reflex Action
When the stimulation of a receptor results in a spontaneous, involuntary reaction, it is called reflex action or simply reflex.
Coordination in Plants
In case of plants, growth and development is in a coordinated manner. The higher plants do not show locomotion.
Growth Regulators
Growth substances are also called the phytohormones. The phytohormones have been put in five different categories based on their actions.
Endocrine System - Hormonal Control
Exocrine glands are those which pour their secretions into a duct. For example, sweat glands, tear glands, etc.
Pituitary Gland
It is made up of three lobes - anterior, middle and posterior. They secrete hormones in response to the secretion of neurohormones by the hypothalamus.
Pineal, Thyroid and Parathyroid Glands
It is a butterfly-shaped, bilobed gland that is situated at the base of the larynx. The two lobes are joined by an isthmus. The hormone secreted is thyroxine.
Thymus and Pancreas
It is a gland that is prominent behind the breastbone in children.It gradually decreases in size in adults.
Adrenal and Gonads
The adrenal glands are present on top of the kidneys and appear cap-like on top of each kidney. Each adrenal gland has two layers - outer cortex and inner medulla.
Feedback Mechanism
It is a method of controlling the hormone production. In some cases the production of hormones is controlled by the nervous system.
Summary
With increasing complexity, the organisms have had to develop means of control and coordination between the different parts of the body.
Question and Answers
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Multiple Choice Questions
