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Revision Notes on Control and Coordination

Different organs work together in an organism to carry out different functions, this is known as coordination. Proper control and coordination is necessary to carry out essential functions of the life.

Animals Nervous System

Animals nervous system consists of specialized nerve cells also known as neurons. A typical neuron consists of cell body, axon and dendrites. Cell body contains nucleus. Dendrites detects the information from the environment. This information is picked up by the dendritic tips and sets off the electrical impulse which travels from dendrite to cell body and then to axon.



Fig.1. Structure of the Neuron

Reflex Action

A sudden response to some environment stimulus is known as reflex. For example, we sudden take off our hand from the flame without thinking.

Reflex Arch

Sensory neurons synapse in the spinal cord before it passes to the brain. This pathway is known as reflex arch.



Fig.2. Reflex Arch

Nervous System

Vertebrates nervous system is classified as central nervous system and peripheral nervous system. Brain and spinal cord are the parts of central nervous system. Peripheral nervous system consists of autonomic nervous system and somatic nervous system. Autonomic nervous system consists of spinal nerves and cranial nerves.

Human Brain

Brain is divided into forebrain, midbrain and hindbrain.


	

	
Forebrain consists of cerebrum, hypothalamus and thalamus. Forebrain is specialized in hearing, sight, smell etc. It also controls voluntary movements in our body such as movement of leg muscles. Centre for hunger is also located in the separate part of forebrain. Cerebrum or the cerebral cortex consists of 4 lobes- parietal lobe, temporal lobe, occipital lobe and frontal lobes. (NTSE LEVEL)
	




Fig. 3. Different Lobes of the Brain


	

	
Midbrain is located between the forebrain and hindbrain. It controls certain involuntary actions in the body.
	
	

	
Hindbrain consists of pons, medulla and cerebellum. It controls salivation, blood pressure and vomiting. Cerebellum also controls certain important functions such as riding a bicycle, picking up a pencil. It also maintains posture and balance of the body.
	




Fig.4. Structure of Human Brain

Brain is protected in a bony case known as cranium. Cranium also contains a fluid filled in it known as cerebrospinal fluid (CSF) that protects the brain from mechanical shock and injury. And spinal cord is protected by vertebral column.

How nervous tissue causes action?

Information is received by nervous tissue, then it passes to brain muscles and then it causes the action. The junction between the two neurons is known as synapse. Information are passed from one neuron to another neuron via electrical or chemical transmission.


	

		

			

			
Electrical transmission 
			
			

			
Chemical transmission
			
		
		

			

			
No need of neurotransmitter is needed
			
			

			
Neurotransmitter is needed
			
		
		

			

			
Fast mode of nerve impulse transmission
			
			

			
Slow mode of nerve impulse transmission
			
		
		

			

			
Impulse are directly transmitted from one neuron to another neuron
			
			

			
Impulse are not directly transmitted from one neuron to another neuron
			
		
	


 

Coordination in plants

Plants though do not have nervous system or muscles but they also respond towards the stimulus. For example, when we touch Mimosa pudica (touch-me-not plant), its leaves fold up and droop. There are two types of movements in plants -dependent on growth and independent of growth. When we touch the Mimosa pudica, its leaves fold up but no growth occurs, so it does not involve any growth. But movement of seedling is due to growth. Plants convey information from cell to cell through electrical-chemical means.

Hormones produced by the plant (NTSE LEVEL)


	

		

			

			
Hormone
			
			

			
Function
			
		
		

			

			
Auxins
			
			

			
Promote root growth
			
		
		

			

			
Cytokinin
			
			

			
Promote shoot growth and cell division
			
		
		

			

			
Gibberellin
			
			

			
Promotes flowering
			
		
		

			

			
Abscisic acid
			
			

			
Retards growth
			
		
		

			

			
Ethylene
			
			

			
It helps in fruit ripening
			
		
	


Movement due to growth

The most common example of movement of growth are tendrils. Tendrils are sensitive to touch. When they come in contact with some object, the part of tendril away from the object will grow fast compare to the part of tendril which is in contact with the object. So it is a directional movement and it appears as if the plant is moving.

Directional movements of the plants are known as tropic movements. The movement can be towards the stimulus or away from the stimulus. Examples of some movements in plants are mentioned below-


	

		

			

			
Phototropism
			
			

			
Movement due to light
			
		
		

			

			
Gravitropism
			
			

			
Movement due to gravity
			
		
		

			

			
Hydrotropism
			
			

			
Movement due to water
			
		
		

			

			
Chemotropism
			
			

			
Movement due to some chemicals
			
		
	


 

Endocrine Glands

They are the chemical messengers that are secreted in small quantities. There are two types of glands- endocrine glands and exocrine glands. Endocrine glands do not have ducts to carry the secretion and they produces the hormones.



Fig.5. Human Endocrine Glands

Exocrine glands do have ducts to carry their secretion. List of different hormones secreted and their function are given below- (NTSE LEVEL)


	

		

			

			
Endocrine Gland
			
			

			
Function
			
		
		

			

			
Thyroid gland
			
			

			
Produces thyroxine that regulates carbohydrate, protein and fat metabolism
			
		
		

			

			
Adrenal gland
			
			

			
Produces adrenaline and it is secreted at the time of fear, fight or flight
			
		
		

			

			
Pancreas
			
			

			
Produces insulin and glucagon which regulate glucose metabolism in our body.
			
		
		

			

			
Testis
			
			

			
Produces male hormone known as testosterone required male secondary sexual characteristics such as beard and moustaches.
			
		
		

			

			
Pituitary gland
			
			

			
Secretes growth hormone that regulates the growth and development of an organism
			
		
		

			

			
Ovaries
			
			

			
Produces oestrogen needed for female sexual development
			
		
	

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