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The Nervous System and Coordination in Living Organisms

Updated: Jan 28



Living organisms have the ability to respond to stimuli in order to protect themselves. This response is made possible by the nervous system and hormonal system. Nerve cells, also known as neurons, play a crucial role in detecting stimuli and transmitting information to different parts of the body. In this blog, we will explore the different components of the nervous system, the functions of the brain, and how plants also exhibit coordination and response to stimuli.

The Nervous System


The nervous system is responsible for producing responses to stimuli in living organisms. It is divided into two main parts: the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord, while the PNS consists of the nerves that connect the CNS to the rest of the body.

### The Brain

The brain is a vital organ that coordinates various functions in the body. It receives information from all parts of the body and integrates it to produce appropriate responses. The brain is divided into three main parts: the forebrain, midbrain, and hindbrain.

#### Forebrain

The forebrain is responsible for the thought process. It has different regions that receive sensory impulses from various receptors, such as those for hearing, smell, and sight. The forebrain analyzes the information received and takes decisions based on the stored knowledge in the brain. It also controls voluntary muscle movements, like those involved in playing sports.

#### Midbrain

The midbrain controls visual and auditory reflexes. It also has centers for controlling eye and eyelid movements.

#### Hindbrain

The hindbrain consists of three parts: the pons, medulla oblongata, and cerebellum. The pons controls the sleep-wake cycle and breathing. The medulla controls heart rate, breathing, blood pressure, and other involuntary functions. The cerebellum is responsible for maintaining posture, balance, and coordination of movements.

Plant Coordination


Plants also exhibit coordination and response to various stimuli, such as sunlight, water, touch, and chemicals. However, unlike animals, plants do not have a nervous system or muscular system. Instead, they rely on growth and changes in cell shape to produce movements.

### Tropic Movements in Plants

Plants show directional movements in response to environmental stimuli, which are known as tropic movements. For example, stems bend towards sunlight, roots grow towards soil or water, and tendrils coil around a support. These movements are caused either by growth or by changing the shape of cells in response to stimuli.

#### Phototropism

Phototropism is the movement of plant parts towards sunlight. It allows plants to maximize their exposure to sunlight for photosynthesis. The bending of stems towards sunlight is an example of phototropism.

#### Geotropism

Geotropism is the movement of plant parts towards gravity. It allows roots to grow towards the soil for anchorage and absorption of water and nutrients. The movement of roots towards the soil is an example of geotropism.

#### Hydrotropism

Hydrotropism is the movement of plant parts towards water. It allows roots to grow towards sources of water for absorption. The movement of roots towards water is an example of hydrotropism.

#### Thigmotropism

Thigmotropism is the movement of plant parts in response to touch. It allows plants to respond to mechanical stimuli and adapt to their surroundings. The coiling of tendrils around a support is an example of thigmotropism.

#### Chemotropism

Chemotropism is the movement of plant parts towards a chemical stimulus. It allows plants to respond to chemical cues in their environment. The growth of a pollen tube towards the ovule is an example of chemotropism.

### Hormones in Plants

Tropic movements in plants are mediated by special chemical compounds called phytohormones. The five major phytohormones are auxins, gibberellins, cytokinins, ethylene, and abscisic acid.

#### Auxins

Auxins stimulate cell elongation and are responsible for tropic movements in plants. They are mostly concentrated in the shoot and root tips.

#### Gibberellins

Gibberellins also promote stem and root elongation in plants.

#### Cytokinins

Cytokinins promote cell division and are concentrated in fruits and seeds, where rapid cell division takes place.

#### Abscisic Acid

Abscisic acid acts as a growth inhibitor and helps in the wilting of leaves.

#### Ethylene

Ethylene stimulates the ripening of fruits.

Hormones in Animals


In animals, control and coordination are achieved through the endocrine system. The endocrine system consists of various endocrine glands that secrete hormones. These hormones control many body functions, such as growth, repair, and reproduction.

### Functions of Hormones

Hormones help to control many body functions, including growth, repair, and reproduction. They are secreted by glands in small quantities and are transported through the bloodstream to their target organs or tissues. Once they reach their target, they act to regulate specific functions.

### Adrenaline and the Fight or Flight Response

In dangerous or harmful situations, our body produces a hormone called adrenaline. Adrenaline helps us to respond to the situation by either fighting or fleeing. It increases the supply of oxygen and glucose to our skeletal muscles, preparing them for action. Adrenaline also affects other organs, such as the eyes, blood vessels, and heart, to optimize our response to the stimulus.

### Iodine and Thyroxine

Iodine is an essential mineral required for our body. It is necessary for the production of a hormone called thyroxine, which is produced by the thyroid gland. Thyroxine controls the metabolism of carbohydrates, proteins, and fats in our body. Insufficient iodine in our diet can lead to low production of thyroxine and result in a condition called goiter.

### Growth Hormone

Growth hormone, secreted by the pituitary gland, is responsible for the regular growth of our body. It controls the growth of skeletal muscles and bones. Deficiency or overproduction of growth hormone can lead to conditions like dwarfism or gigantism.

### Male and Female Sex Hormones

Testosterone is the male sex hormone responsible for the development of secondary sexual characteristics in males, such as the growth of facial hair, deepening of voice, and production of sperm. Estrogen is the female sex hormone responsible for the development of secondary sexual characteristics in females, such as the growth of breasts, onset of menstruation, and development of ovaries.

### Diabetes and Insulin

Diabetes is a condition where the body cannot effectively control blood sugar levels. It is characterized by high levels of blood sugar. Insulin, produced by the pancreas, helps to control blood sugar levels by facilitating the uptake of glucose from the bloodstream into cells. Some people are advised to eat less sugar and starchy foods to manage their blood sugar levels.



The nervous system and hormonal system play crucial roles in the coordination and response to stimuli in living organisms. While animals rely on the nervous system and hormonal system, plants exhibit coordination and response through growth and changes in cell shape. Understanding these systems helps us appreciate the complexity and adaptability of living organisms.

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