Control and coordination

Generally we see that plants grow by pushing the soil a side and these are the movements controlled by growth. But children playing on swings and buffaloes chewing the food and cat running these are uncontrolled. These are uncontrolled because cat runs if it see rat and children play on swing to get joy and entertainment and buffaloes chews to make complex food materials to simple food materials. These are the movements not controlled by growth. A response occurs in us when there is a sudden change in our environment. Movements are definitely controlled in a manner. When we are walking with friends we whisper but we wont shout these all are controlled movements.

7.1. Animals - nervous system

When we touch a hot object we should respond to that if we did not respond it is very dangerous for us. The information in our environment is detected by some receptors which are located in nerve cells. These receptors are located in sensory organs like ears, nose and tongue. Gustatory will detect taste and olfactory receptors will detect smell.

Activity 7.1:-

When we put some sugar on our tongue. It tastes so sweet for us. But when we tastes sugar by blocking our nose we cant taste it because gustatory (the lobes which are helpful for detecting taste)and olfactory lobes(the lobes which are helpful to detect smell) are inter connected. When we smell food then only we are able to taste the food. We generally observe the taste of food in normal days but we are unable to taste the food when we are suffering with cold because our olfactory lobes are inactive at that time.

7.1.1. What happens in reflex actions?

‘Reflex’ is a word which we use when some sudden actions occur in nature. We say ‘I jumped out of the way of the bus reflex’, or ‘I pulled my hand back from the flame reflexly’, or ‘I was so hungry my mouth started watering reflexly’. We do some things without thinking about those and they are out of control. Touching fire is a very dangerous and painful act for us. But how do we respond to it? We respond to that because we already know that how it pains and effects after touching the fire. So, we react to it and we don't touch fire. How much time we think on any topic? That will definitely depends on our thinking capability. Thinking is a very complex activity. It involves many nerve impulses. In our body thinking tissue consists of dense networks which has interactively connected neurons. Why all the information in our body reaches to brain? All the information reaches to brain because all the nerve impulses from different parts of our body are connected to brain. When we touch a hot object that information reaches to brain and that brain instructs the muscles near that burning place to move the hand from that place. So, due to this reason we remove our hand from that burning place. But this is a long process. So if the nerve impulses are directly connected to the muscles then it may react quickly. So to made that possible we should send that signals to other region where it should react fast. That is the region where the nerve impulses meet at a point. That meeting point is the spina cord. So if the impulses reach the the spinal cord then our hand reacts fast and moves away from the heat. Reflex arcs are also evolved in animals. But animals have very less thinking power than human beings. They react very slow to the actions.

7.1.2 Human brain:-

Spinal cord is made up of nerves which gives us the ability to think about something. The information collected in the spinal cord will be sent to the brain which is the main coordinating system in our human body. It controls each and every part of our body. Writing, talking, moving a chair, clapping at the end of a program are examples of voluntary actions which are based on deciding what to do next. So to do these actions brain has to send messages to the muscles. The communication between the central nervous system and the other parts of the body is facilitated by the peripheral nervous system consisting of cranial nerves arising from the brain and spinal nerves arising from the spinal cord.

Brain is mainly divided into three parts they are:- 1) Fore brain 2) Mid brain 3) Hind brain
Fore brain is furtherly divided into 3 parts they are:- 1) Olfactory lobes 2) Cerebrum 3) Diencephalon

1) Olfactory lobes:- These club shaped widely spread bodies are visible from the ventral surface.

Functions:- These are connected with the sense of smell.

2) Cerebrum:- It consists of two lobes called cerebral hemisphere. The surface of the cerebrum has many folds, they appear as elevations(Gyri) and depressions(Sulci). Sulci is very prominent and divide each hemisphere into four lobes.

Functions:- 1) Site of mental abilities, controls thinking, memory, reasoning, perception, emotions and speech. 2) Interprets sensations and responds to cold, heat, pain and pressure.

3) Diencephalon:- This rhomboidal shape lobe visible from inferior surface of brain. It lies between cerebrum and mid brain. It is divided into thalamus and hypothalamus.

Functions:- 1) Relay center for sensory impulses, such as pain, temperature and light. 2)Reflex center for muscular activities. 3) Center for certain emotions such as anger. 4) Center for water balance, blood pressure, body temperature, sleep and hunger. 5) The hypothalamus controls the pituitary gland, which functions as the master gland.

4) Mid brain:- This is a small thick stalked portion. This connects forebrain with cerebellum and pons of hind brain.

Functions:- It relays motor impulses from the cerebral cortex to the spinal cord an relays sensory impulses from the spinal cord to the thalamus, reflexes for sight and hearing. Hind brain is furtherly divided into two types they are:-

1) Cerebellum 2) Medulla oblongata

Cerebellum:- It is located below the cerebrum and above medulla oblongata. It consists of two large cerebral hemispheres. Functions:- 1) Maintains posture, equilibrium and muscle tone. 2) Coordinates voluntary movements initiated by cerebrum.
Medulla oblongata:- It is almost triangular shaped. Medulla oblongata extends from pons to spinal cord.

7.1.3. How are these tissues protected?

A delicate organ in our body is the brain. It is a very important organ in our body. All the functions of various parts in our body are guided by the brain. So it has to be protected. It is placed in the bony box which is known as cranium. The cranium is a very hard box. A fluid which is present in the cranium is known as cranial fluid. It protects the brain from external shocks and injuries. If we keep our hand back to the head then we feel some hard and bumpy structure. That is our vertebral column. It is connected to our brain. It gives a lot of support to our brain.

7.1.4. How does the nervous tissue cause actions?

When the brain orders a muscle to move. It should definitely move because it gets some instructions from brain. It controls the whole body. When the brain gives instructions then the muscle changes its shape. It changes its shape due to the cellular components in muscle. The new arrangement of the proteins in muscle cells make the muscle to become shorten

1. what is the difference between reflex arc and walking?

Reflex arc is a involuntary action(which is not controlled by us) but walking is a involuntary action(which are controlled by us). Reflex arc is not controlled by any of the organ but the walking is controlled by our brain in the human body. Reflex arc is under the control of PNS(peripheral nervous system) but walking is under the control of CNS(central nervous system).

2. What happens at the synapse between two neurons?

The transfer of information between two neurons is known as synapse point.

3. Which part of the brain maintains posture and equilibrium of the body?

Cerebellum is the part in brain which maintains posture and equilibrium of the body.

4. How do we detect the smell of agarbatti(incense stick)?

The smell of agarbatti diffuses in the air. That smell is detected by the olfactory lobes. Later that information was sent to the brain. In this way we can detect the smell of the agarbatti.

5. What is the role of the brain in reflex action?

A reflex arc is the connection between receiving the signals and responding to it. In this brain plays no role. Spinal cord plays main role in this.

7.2 Coordination in plants

Animals and human beings possess special type of nervous system to respond. But plants do not have nervous system or muscles to respond. When we touch chhui-mui(touch me not plant, sensitive plant which belongs to mimosa pudica family) plant responds to our touch. When a seed germinates the plant grows towards up and the roots grow towards downwards. These happen due to some movements. plants show two different types of movement – one is dependent on growth and the other is independent of growth.

7.2.1. Immediate response to stimulus:-

The movement of plant depends on the the place where we touched and the part which moves. Plants use electric-chemical signals to communicate because they don't have specialized tissues in them like animals and human beings. In human beings brain send signals to the muscle then the muscle changes its shape likewise in the plants they also change their shape depending on the amount of water. That changing of shape is shrinking or swelling.

7.2.2. Movement due to growth:-

Some plants like pea plants are creepers. They climb up on other plants the part which creep on other plant is known as tendril. That tendril is sensitive to touch. Some part of the tendril grows very fast because that tendril is away from other plant. Some part of the tendril grows very slow because that tendril is closer to the other plant. The slow growing tendril makes curls and bound to other plants.

Activity 7.2:-

Take a conical flask and cover the mouth of the conical flask by wire mesh and keep some beans seeds on the mouth of the conical flask. Keep that in a cardboard. That cardboard should have one sided open and that one side should face the sun light. Leave that plant for some days we observe the plant bends towards the side of the light that phenomenon is known as phototropism. The roots of the plant bends away from the sun light.

Take a conical flask and cover the mouth of the conical flask with a wire mesh and place some bean seeds on the mouth of the flask and bend that flask slanted on the ground. Leave that setup for some days we observe that the plant grows towards the direction of the sunlight. That phenomenon is known as phototropism(negative geotropism). The roots bends towards the direction of the earth. This phenomenon is known as geotropism(positive geotropism).

If the plant show variations regarding water then that type is known as hydro(water)tropism. If the plant responds to chemicals then that type is known as chemotropism. The response in touch me not plant is very fast. But the response in sunflower plants to day and night is very slow. The changes related to growth is very slow.

1. What are plant hormones?

Plant hormones are nothing but the signals produced in plants regarding their growth and development. Usually these plant hormones release in very less concentrations.

2. How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?

The movement of leaves of the sensitive plant is very fast but the movement of a shoot towards light is very slow. The movements of leaves in sensitive plant is known as nastic movements. The movements of a shoot towards light is known as phototropism.

3. Give an example of a plant hormone that promotes growth.

Auxins is an example of a plant hormone that promotes growth .

4. How do auxins promote the growth of a tendril around a support?

Auxins promote the growth of a tendril around a support as it is synthesized in the tip of the shoot. On the other side it coils around other plant to gain the support.

5. Design an experiment to demonstrate hydrotropism.

Take two beakers. Place wet soil in one beaker and dry soil in another beaker. Place two beans seeds in both the beakers. In the dry soiled beaker place a beaker of water to the side of the big beaker. Leave that set up for some days. We observe that the plant roots which is kept in wet soil grows straight. The plant roots which is kept in dry soil bends towards the side of water. It indicates that the plant responds to hydrotropism.

7.3. Hormones in animals:-

In squirrels when they are ready to attack by predators they have only two chances they are ready to run or they should be ready to fight against them. These actions have to be done faster to avoid the attack from the predators. These are done by chemical signals. Adrenaline is the organ which controls the signals.

1. How does chemical coordination take place in animals?

Chemical coordination take place in animals in the form of hormones. Hormones are secreted by endocrine system. It regulates the complete growth and development in animals.

2. Why is the use of iodized salt advisable?

The use of iodized salt is advisable because it regulates thyroxine hormone in thyroid gland. Lack of that hormone causes goiter. So usage of iodized salt is very important.

3. How does our body respond when adrenaline is secreted into the blood?

It causes coronary heart to beat quickly, it provides extra oxygen to the muscle groups and blood strains receives extra oxygen. These are the responses occur when adrenaline is secreted into the blood.

4. Why are some patients of diabetes treated by giving injections of insulin?

A:-Diabetes is the disease in which the sugars in blood level increases. Insulin is secreted by islets of Langerhans in pancreas. The patients who are suffering with diabetes the secretion of insulin hormone is very less. For that patients we have to inject insulin into their blood. Insulin controls the sugars in the blood.

1 Mark questions

1. which is the largest and most prominent part of the brain?

A:- Cerebrum is the largest and most prominent part of the brain.

2. Write the function of thyroxine hormone in our body.

A:- It controls basal metabolic rate and regulates metabolism of carbohydrates, fats and proteins.

3. Name the part of hind brain which takes part in regulation of respiration.

A:- Medulla oblongata

4. Which hormone helps in lowering the level of blood glucose in human beings.

A:- Insulin.

5. We suddenly withdraw our hand when a pin pricks. Name the type of response involved in this action.

A:- Reflex action.

6. Which hormone is responsible for the development of moustache and beard in man?

A:- Testosterone

7. Name the structural and functional units of human nervous system.

A:- Neuron

8. Name two tissues that provide control and coordination in multicellular animals.

A:- 1. Nervous tissue 2. Endocrine tissue.

2 mark questions

1. What are phytohormones?

A:- Phytohormones are chemical substances other than nutrients produced naturally in plants which regulate growth, development, differentiation and a number of physiological processes. Ex:- auxin, gibberellins, abscisic acid and cytokinin's.

2. What is synapse?

A:- Synapse is a narrow fluid filled gap which functions as communicating junction between axon end of one neuron and dendrite tip of next neuron. All information of our environment is detected by specialized tip of some nerve cells.

3. State the role of the brain in reflex actions.

A:- It functions as relay center of transferring impulse from sensory to motor neurons in several reflex actions called cerebral reflexes, eg:- closure of eyes exposed to flash of light, salivation at the sight of smell of food. In spinal reflexes it acts as information collecting and evaluation center without any direct involvement in reflex action.

4. Write the functions of the following?

1.sensory neuron 2. cranium 3. vertebral column 4. motor neuron

A:- 1. Sensory neuron: Picking up sensation from the receptor and passing it to central nervous system. 2. cranium: protection of brain 3. vertebral column: protection spinal cord 4. motor neuron: taking message from central nervous system to muscle, gland or organ to perform its function.

5. State one example of chemotropism.

Growth of pollen tube towards the ovule due to chemical stimulus during the process of fertilization in a flower is an example of chemotropism.

4 Mark questions

1. Why does the flow of signals in a synapse from axonal end of one neuron to dendrites end of another neuron takes place but not in the reverse direction? Explain.

A:- At the synapse axon terminal comes in close proximity to the dendron terminal of next neuron. Axon terminal is expanded to form pre synaptic knob and the other dendrite terminal forms post synaptic depression. In between the two, lies a narrow fluid filled space called synaptic cleft. As the nerve impulse reaches the pre synaptic knob the synaptic vesicles get stimulated to release neuro transmitter in the synaptic cleft. The neuro transmitter molecules diffuse across the gap to come in contact with post synaptic membrane. In this way, nerve impulse passes across the minute gap to stimulate dendron of other neuron. The synapse acts as one way valve to conduct impulse in one direction only. This is so because chemical substance called neuro transmitter is secreted only on one side of the gap i.e., on axons side. It carries impulse across the synapse and passes it to the dendron of the other neuron. In this way, impulses travel across the neurons only in one direction i.e., from axon of one neuron to dendron of other neuron through a synapse.

2. Reflex arcs continue to be more efficient for quick responses. Justify this statement.

A:- Reflex action is an automatic and spontaneous response to a stimulus. The path way taken by nerve impulses and responses in a reflex action is called a reflex arc. It consists of receptor, sensory nerve, spinal cord, motor nerve and effector. Reflex arc is evolved in animals because the thinking process of the brain is not fast enough. Reflex arc enables the body to give quick responses to harmful stimuli so that chances of damage to body are decreased. It also prevents overloading of brain, so prevents its fatigue. Many animals have very little or none of the complex neuron network needed for thinking. So, it is likely that reflex arc has evolved as an efficient way of functioning in the absence of true thought processes. However, even after complex neuron network have came into existence, reflex arcs continue to be more efficient for quick responses.

MCQ’S

1. Which plant hormone promotes dormancy in seeds and buds?

A) auxin

B) gibberellins

C) cytokinin

D) abscisic acid

2. Roots of plants are:

A) positively geotropic

B) negatively geotropic

C) positively phototropic

D)none of these

3. Any change in the environment to which an organism responds is called

A) stimulus

B ) coordination

C) response

D)hormone

4. Breathing is controlled by which part of the brain ?

A)cerebrum

B) cerebellum

C) hypothalamus

D) medulla oblongata

5. Identify which of the following statements about thyroxin is incorrect ?

A) thyroid gland requires iodine to synthesize thyroxin

B) thyroxin is also called thyroid hormone

C) it regulates proteins, carbohydrates and fat metabolism in the body

D) iron is essential for the synthesis of thyroxin

6. Which part of nervous system controls the reflex activities of the body ?

A) brain

B) spinal cord

C) cerebrum

D) cerebellum

7. Main function of cerebrum is

A) thinking

B) hearing

C) memory

D) balancing

8. A microscopic gap between a pair of adjacent neurons over which nerve impulses pass is called

A) neurotransmitter

B) dendrites

C) axon

D) synapse

9. A part of the body which responds to the instructions sent from nervous system is called

A) receptor

B) effector

C) nerves

D) muscles

10. Fall of mature leaves and fruits from plants is triggered by which of the following substance ?

A) auxin

B) cytokinin

C) gibberellin

D) abscisic acid