Control And Coordination

Neurons are the structural and functional unit of human nervous system. Parts of neuron are dendrite, nucleus, cell body, axon and nerve ending. All the information is received from dendrites and through nerve ending is passed to the next neuron.

Gustatory receptors detect the taste. They are distributed over the surface of the tongue in individual organs called taste buds. Like olfactory receptors will detect smell.

At the end of the dendritic tip information is acquired. After the information is acquired, chemical reaction is set off at the dendritic tip and an electrical impulse is generated. This impulse is passed through axon to its end. At axon end, impulse is set off and again some chemicals are released, which crosses the gap between the two nerve cells and again starts the same procedure in the second nerve cell.

A reflex action or also known as reflex is the sudden action given in response to any activity. These are the involuntary movement. Reflex action does not involve the conscious part of the brain. The path of impulses in reflex action is known as reflex arc. For example when we touch the hot pan by mistake we suddenly pull-off our hands. This response to the stimuli is known as reflex action.

Examples: - 1. On touching a hot pan we pull-off our hand.

2. Contraction of pupil when there is bright light.

Components of reflex arc are receptors, sensory neuron, spinal cord (CNS), relay neuron, motor neuron and effector. The basic function of sensory neuron is to carry the impulse from sensory organ to the central nervous system. For example when we touch a hot pan the from the receptors present on our hands the stimulus is passed to spinal cord or central nervous system through the sensory neuron.

Spinal cord and brain together make the central nervous system. All the sensory and motor impulses are sent to and from the brain through the spinal cord and also spinal cord is centre for all the reflex actions. Brain the major centre of co-ordination in the body.

Peripheral Nervous System consists of cranial nerves from the brain and spinal nerves from the spinal cord. All these nerves lie outside the spinal cord and brain. The main function of PNS is to build a communication channel between central nervous system and the other parts of the body is facilitated by peripheral nervous system.

The Human brain has three parts- fore-brain, mid-brain, and hind-brain. Fore-brain is the main part which is involved in thinking. It has all the sensory receptors so it receives all the sensory impulses. Different parts of fore-brain are responsible for hearing, seeing etc.

Fore-brain helps us to focus on the objects. In fore-brain occipital lobe is responsible for processing the sight.

hind part Medulla oblongata is responsible for the control of involuntary activities such as breathing, blood pressure(BP) etc.

Spinal cord is protected by the vertebral column, also known as the backbone. It is a hard and bumpy structure which protects the spinal cord.

In order to cause the movement of muscles, muscles change their shapes and arrangement in cell in response to nervous impulse. The new arrangement of proteins thereby, give the muscle cells a shorter form and move in direction according to the mind.

In plants also electrical-chemical means is used to convey the information of touch from the cells to cells. By changing the amount of water they change the shape of the plant cell and hence information about touch is transferred. This movement is known as growth independent movement and this is seen in the touch-me-not plant.

Tropism means movement of the part of the plant either in the direction of the stimuli or away from the stimuli. Stimuli can be light, gravity, water or chemicals. For example, in case of phototropism means movement of part of the plant in the presence of light, in this two type of movement is seen shoots moves or grows in the direction of light whereas in case of roots, it grows in the direction opposite to the light. So, with different stimulus plants show different tropism or directional movement.

They all show the growth of tendrils which are sensitive to touch. When tendrils come in contact with the support, the part which is not in contact with the support tends to grow fast and tendrils circles around the object or the support and clings over the object.

(i) ‘Photo’ means light so, in phototropism light acts as the stimulus.

(ii) ‘Geo’ means earth or gravity so, in geotropism earth or gravity acts as the stimulus.

(iii) ‘Chemo’ means chemicals so, in chemotropism chemicals acts as the stimulus.

In the given diagram, the plant is showing geotropism that is a movement of the part of the plant either in the direction of gravity or away from gravity. A shows negative geotropism or shoots are negatively geotropic as it grows away from the earth or in the opposite direction of the gravity. B shows positive geotropism or roots are positively geotropic as it grows in the direction of gravity or the earth.

Chemotropic movement means movement in the direction of the chemicals. For example, growth of pollen tube towards the ovule during fertilisation.

In an organism cells cannot continuously create and transmit electrical impulses. Thus most multicellular organism use another means of communication between different cells, called the chemical communication.

In this A chemical compound is released, which would diffuse all over around the original cells. Other, cell around will detect the compound using special molecules. They can recognize and transmit the information carried by it. These compounds are called hormones.

In the presence of light auxin is released or is synthesized at the tip of the shoot which helps the cells to grow. When the light comes from one side, auxin diffuse towards the shady part of the shoot. This concentration of auxin elongates the cells of the shady part of the shoot and hence it appears that the plant is bending towards the light.

Cytokinin are the hormones which promote cell division.

Highest concentration of cytokinin is found in the areas of rapid cell division like fruits and seeds.

Abscisic acid is the growth inhibitor hormone that is it stops the growth of the plant. Because of this hormone wilting of leaves is seen.

In stress situations adrenaline is released into the blood by adrenal glands. Its target organ is heart which as results heart rates increases so as to increase the supply of the oxygen to the muscles, blood to digestive system and skin is reduced and breathing rate increases. All these responses together prepare the body to face any stressful situation.

If there is iodine deficiency then production of thyroxin stops and as a result, the neck swells and this condition is known as goitre. Iodine is very important for the production of thyroxine hormone.

Feedback mechanism makes sure that the desired amount of hormones is released. Also, it makes sure that the timing and amount of the hormones are correct. For example in the sugar level increases in the blood, insulin is secreted which decreases the amount of sugar in the blood. As the amount of sugar falls, insulin also gets reduced.

No reflex action is not only function of spinal cord; it is function of central nervous system which consists of spinal cord and brain.

Fore-brain is associated with the feeling of hunger. In fore-brain hypothalamus is responsible for this feeling.

Cerebellum is located in hind-brain and is responsible for maintaining the balance and posture of the body.

Geotropism is necessary for proper growth and orientation of a plant. It is because of geotropism that root and shoot growth in their respective directions.

A. Auxin is a growth hormone and is responsible for cell elongation.

B. Gibberellins help in stem growth, seed germination and flowering.

Adrenaline is secreted by adrenal glands directly into the blood.

The target organ is Heart.

Centriole is responsible for carrying out cell division but in neurons, centrioles are absent so they do not divide. Another reason why neurons don’t divide is that they are linked with a brain so each time it will become difficult for the brain to reset the memory. That is why neurons do not divide.

Effectors are nothing but the muscles itself. If it is absent then the movement of the hand after receiving the signal won’t be possible since there is no organ to act upon the electric impulse. For example, in case we touch hot pan then in the absence of effectors, we won’t be able to pull back our hand.

OR

Occipital lobe of the fore-brain is for sight whereas olfactory lobe is for sense of smell.

Midbrain connects forebrain to the hindbrain. It controls the movement of the head, neck and trunk to locate sounds and visual reflexes that are involved in focusing on the objects.

It controls reflex that are involved in movement of eye muscles, pupil size etc.

When we put food in our mouth that response is a voluntary response and after that, the process of digestion and excretion comes under the involuntary response.

Tropism is the movement in the presence of any stimulus. If the movement is towards the stimulus then it called positive tropism and if the movement is away from the stimulus then it is called negative tropism.

In nastic movement, there is not directional movement in the presence of stimuli. These movement always occur in the particular direction irrespective of the type of stimuli.

Plants have auxin which is synthesized at the tip of the shoot and it is responsible for the directional growth of the shoot towards the light. In the presence of light auxin is released or is synthesized at the tip of the shoot which helps the cells to grow. When the light comes from one side, auxin diffuse towards the shady part of the shoot. This concentration of auxin elongates the cells of the shady part of the shoot and hence it appears that the plant is bending towards the light.

Pancreas produce insulin which helps in maintaining the blood glucose level in the body. When glucose level increases pancreas produced insulin which makes sure that cells take up glucose from the blood. Soon blood glucose level starts to drop and as it decreases the production of insulin also decreases.

Hypothalamus is part of hind-brain. So it becomes the part of CNS and is responsible for maintaining the homeostasis of the body. Also, it is responsible for secreting the hormones in the human body. So because of the hypothalamus there is close coordination between nerves and hormones. Also when adrenaline is released into the blood supply of oxygen increases to the muscle which helps to run and is made of nerves. So nerves and hormones together work in case of stress.

Receptors are tissues which are capable of receiving any stimuli and start the impulse which is passed to the CNS.

Three types of receptors are: -

1. Olfactory receptor: - They detect the smell

2. Gustavo receptor: - They detect the taste

3. Thermoreceptor: - they detect the temperature of the outer world.

Receptor through sensory-motor passes the information to the spinal cord which then sends the information to the brain.

(i) In both the cases stimulus of touch is same.

(ii) In the mimosa plant, the movements of leaves are in the opposite direction to the touch. On touching the leaves, they curl up towards the stem.

This is because plant cell change, their shape by changing the amount of the water in them. This happen due to swelling or shrinking of cell.

In case of the pea, plant tendrils cling over the object or the support so the movement takes places in the direction of the stimulus.

(iii) In mimosa plant, this movement is seen because of the change in concentration of water in the leaves.

In pea plant, this movement is seen because of the rapid growth of that part of a tendril which is away from the stimulus or the support.

Auxin is given in an increased dose which promotes the development of seedless fruits. Other functions of auxin are: it is responsible for elongation of cells at the shoot tip and also is responsible for showing positive phototropism.

(i) In this case adrenaline hormone will be highest in the blood. It is produced by the adrenal gland.

(ii) Supply of blood to digestive system and skin is reduced, supply of oxygen increased towards the muscles and also the blood supply to the heart is increased.

If these glands do not secrete adrenaline then our body won’t get prepared for stressful situations. Also, there are many disorders like Addison’s disorder which a person might have to face such disorders.

Yes feedback mechanism is a very important aspect of hormonal co-ordination as it is responsible for making sure that the desired amount of hormones is released. Also, it makes sure that the timing and amount of the hormones are correct. For example in the sugar level increases in the blood, insulin is secreted which decreases the amount of sugar in the blood. As the amount of sugar falls, insulin also gets reduced.

(i) A is dendrite and B is axon.

(ii) Part A that is dendrite acquires the information in the neuron.

(iii) Through part B that is axon the information travels.

(iv) The information travels in the electrical impulse.

(v) At the nerve ending the impulse is converted into a chemical signal.

(i) When a nerve input signal travelled only up to the spinal cord and gave output signal for a response, then such type of action is called an involuntary action. An involuntary action occurs without the conscience of the organism.

(ii) The nerve pathway is shown below:

(i) Hypothalamus is part of hind-brain. So it becomes the part of CNS and is responsible for maintaining the homeostasis of the body. Also, it is responsible for secreting the hormones in the human body. So because of the hypothalamus there is close coordination between nerves and hormones. Also when adrenaline is released into the blood supply of oxygen increases to the muscle which helps to run and is made of nerves. So nerves and hormones together work in case of stress.

(ii) Differences: -

(i) The endocrine system is a control system of ductless glands that secrete hormones directly through blood. Thus, a smaller size helps in easy diffusion through the blood. Moreover, the endocrine molecules are basically responsible for chemical communication in an organism. These glands secrete special small molecules which needs to be diffused with cells of target organs to detect them with special molecules. Thus, to make the process of diffusion faster in the target organ cells. Hence these hormones consists of small molecules.

(ii) The three endocrine glands and the chemicals they produce are:
1. Pineal gland - It produces melatonin. It is the hormone that affects the sleeping patterns.
2. Thyroid – This gland produces hormones which regulate the heart rate, the rate of metabolism and affect the growth.

3. Pituitary gland – The most important gland, that produces more than 9 hormones – example - thyroid stimulating hormone (TSH).
The organs of endocrine glands are shown here:

P is pancreas. H is insulin. D is diabetes or high blood sugar level.

(i) Progesterone was being injected in buffalo to increase the milk production.

(ii) Progesterone is responsible maintain the menstrual cycle in the women. Milk-producing and sex hormone.

(iii) This practice should be discouraged as it may affect the buffalo as well as the quality of milk which can have an adverse effect on us.

(iv) Responsible, good knowledge skills and aware.

(i) Hormones like testosterone and estrogen are responsible for the onset of adolescence.

(ii) Alcohol acts as a depressant and it slows down the working of the nerves cell and also the activity of CNS.

(iii) A. The government should make sure that all the liquor shops should not give drinks without checking the id card.

B. Should run awareness campaigns.

(iv) Responsible, knowledgeable and concerned.

(i) Abscisic acid is product A. Its functions are cell division (in fruits and seeds) and breaking of seed dormancy.

(ii) Abscisic acid. It inhibits the growth.

(iii) Auxin – elongation of cells and promotes the growth of seedless fruits.

Gibberellins – stem growth, seed germination and flowering.

(iv) Values like honesty and responsibility should be present in agricultural practitioners.

In this both nerves and hormonal function is involved so the only part which handles the both is hypothalamus.

At Z because the message does not reached the brain cells and as a result the man cannot feel it.

Function of P – Master hormone

Function of Q – Q is pituitary gland and it is responsible for secreting hormones.

Function of T – Centre of conscious behavior

If relay neuron is damaged, the impulse cannot pass from R-Q

Because when adrenaline is secreted the blood supply to digestive system decreases and so concentration in liver decreases and whereas blood flow increases so the all undigested food concentration of glucose in blood increases.

from the receptor the information passes from sensory neuron to relay neuron and then to motor neuron.

because all are the examples of reflex action. In all the examples a sudden response is given to stimuli.