Control And Coordination

Abscisic acid (ABA) is one of the essential plant hormone which functions mainly as a growth inhibitor.

It plays primary regulatory roles by:

(a) Initiating and maintaining seed and bud dormancy in plants.

(b) In the plants response to stress, specially water stress- it also promotes closing of stomata to prevent water loss.

(c) It promotes leaf abscission (falling of leaves).

(d) It inhibits shoot growth but promote root growth.

Explanation: Presence of ABA delays the plants growth and inhibits division of cells which lead to inhibition of shoot growth. Under stress condition like winter, plants adapt a mechanism of preventing the seed and bud from germination (dormancy) to survive.

Cytokinin is the plant hormone responsible for the promotion of cell division and gibberellins is the hormone responsible for cell elongation.

Explanation: HORMONES are chemical compounds which help to coordinate growth, development and responses to the environment. Cytokinins (CK) are a class of plant growth substances (phyto-hormones) that promote cell division. They are the positive regulators of cell division in shoot apical meristem.

Gibberellins (GAs) are plant hormones that regulate growth and influence various developmental processes, including stem elongation.

Adrenaline is the hormone which is secreted during emergency. The gland which secretes adrenaline is called adrenal gland.

Explanation: Hormones are chemical messengers whose secretion is maintained by endocrine glands. Adrenalin gland (is an endocrine gland) is situated above both kidneys. It helps in regulation (increasing) of blood pressure, heart beat, carbohydrate metabolism (during emergency).

Cerebellum is responsible for maintaining body posture and equilibrium. It does so by controlling & coordinating muscular movements.

Explanation: Cerebellum is the part of Hind-brain. This portion of brain is maintaining the voluntary actions of a body which are under the control of a person. Example: Picking up of a pen.

The nerve impulse flows in one direction. The dendrites receive incoming nerve impulses from other neurons. This impulse travels from the dendrite to the cell body and then at the end of the axon transmits the impulse to another neuron or receptor.

Explanation: one single path is followed from neuron to neuron. This tells it is a unidirectional process. The axon have doesn’t have the ability to take up stimulus and only cell body of neuron can take up signal because it has dendrites. This means every part of neuron has specific function in a synchronised manner.

Neuroglia, also called glial cells or simply glia, is non-neuronal cell in the central nervous system (brain and spinal cord) and the peripheral nervous system. They have a supporting role in the protection and maintenance of neurons.

Explanation: There are two groups of cells that comprise the human nervous system – neurons and neuroglia. This means neuroglias are cells in our nervous system that are not neurons. They just maintain the environment inside the nervous system to in equilibrium. They regulate homeostasis.

The pathway of the reflex action is called Reflex arc. Reflex action is any spontaneous, involuntary and automatic response to a stimulus to protect us from harmful situations. For e.g. when a person touches a hot plate a sudden action leading to withdrawal of hand occurs in a certain manner, this path of manner determines the reflex arc.

Explanation: It means that reflex action is the response which is completed by a pathway called reflex arc. For example: knee jerk etc.

These 3 steps occur to generate a response with a stimulus in a reflex arc

(i) Receive the information from environment

(ii)Receive the information from various body parts.

(Stimuli Response)

(iii) To act accordingly through muscles and glands and generate response.

a) Gibberellins- These are plant hormones that regulate growth and influence various developmental processes, including stem elongation.

b) Auxin- The primary function of the auxin hormones is to elongate plant cells in the stem. Auxin by some mechanism breaks the bonds holding its cellulose fibers together. These broken bonds give the cell wall greater flexibility and expandability, so that more water can enter the cell by diffusion, causing the cell itself to elongate.

c) Cytokinin- They are a class of plant growth substances (phytohorm-ones) that promote cell division. They are the positive regulators of cell division in shoot apical meristem. They are presenting in greater concentration in areas of rapid cell division, such as in fruits and seeds.

d) Abscisic Acid (ABA)- It is the growth inhibitory hormone or the stress hormone. It restrains the growth and causes the falling of old leaves.

Neurons are the structural & functional unit of Nervous system (Brain). Reflex actions are sudden responses. The sensory nerves that detect the heat are connected to the nerves that move the muscles of the hand. Such a connection of detecting the signal from the nerves and responding to it quickly is known as reflex arc. Reflex arcs are formed in the spinal cord and the information reaches the brain and brain responses to it.

â passing of information takes place –

(i) By Electric impulse (inside the neuron) and

(ii) In the form of chemicals (At synapse)

This tells that neurons are the medium by which stimuli is sent to the brain and then to the action centre where the response has to occur.

Like this:

Stimulus → Receptor organ → Sensory nerve → Spinal cord →Effector organs→ Response

Deficiency of iodine cause a disease called goitre. It occurs due to lack of thyroxine production by the thyroid gland.

Symptoms include:

a) Swollen neck

b) Hampered metabolism

c) Coughing

d) Difficulty in breathing.

Explanation: Iodised Salt is Necessary because iodine mineral is a necessary part of thyroxine hormone secreted by the thyroid gland. Thyroxine helps in regulating the metabolism of carbohydrates, fats, and proteins. It is responsible for governing the rate of metabolism in the body.

The excess or deficiency of hormones has a harmful effect on our body. Feedback mechanism makes sure that hormones are secreted in precise quantities and at right time.

Explanation: Insulin is the hormone secreted by the pancreas to maintain blood sugar level. If it is not secreted in the proper amount, the blood sugar level raises causing harmful effects. Hence it is important that the hormone should be present in a correct amount for proper function. This regulation of hormone secretion is achieved by a feedback mechanism. This system will switch off the machinery (hormone synthesis) when it is sufficient in the body and will switch it on only when the concentration is less.

Synapse is the space junction between two adjacent nerves. OR The point of contact between the terminal branches of axon of one neuron with the dendrite of another neuron is called synapse. It is a structure in a nervous system.

The electrical impulse causes the release of chemicals at the end of axon. These chemicals cross the synapse (gap) and start a similar electrical impulse in the dendrite of the next neuron. So this means that synapse allow the delivery of impulses from neurons to other cells such as muscle cells or glands.

Explanation: It takes place when a chemical i.e. neurotransmitter is diffused at the axon end points towards the dendrite point of another neuron. These stimulate the chemo- receptors present in Dendron and generate the signal further.

(a) Olfactory receptors--- (iii) Nose

(b) Thermo receptors (temperature receptors) --- (iv) Skin

(c) Gustatoreceptors--- (i) Tongue

(d) Photoreceptors--- (ii) Eye

Explanation: Receptors are molecules that receive signals from outside of a cell.

Olfactory receptors are expressed in the cell membranes of olfactory receptor neurons and are responsible for the detection of odorants (i.e., compounds that have an odour) which give rise to the sense of smell.

Thermo receptors are specialized nerve cells that are able to detect differences in temperature.

Gustato receptors are taste buds. They facilitate the sensation of taste.

A photoreceptor cell is a specialized type of neuron found in the retina. Photoreceptors convert light into signals that can stimulate biological processes.

The excess or deficiency of hormones has a harmful effect on our body. Feedback mechanism makes sure that hormones are secreted in precise quantities and at right time.

For example Diabetes is due to deficiency of Insulin hormone secreted by the Pancreas that is responsible to lower/control the blood sugar levels. This regulation of hormone secretion is achieved by a feedback mechanism. This system will switch off the machinery (hormone synthesis) when it is sufficient in the body and will switch it on only when the concentration is less.

Explanation: Insulin is the hormone secreted by the pancreas to maintain blood sugar level. If it is not secreted in the proper amount, the blood sugar level rises to cause harmful effects. Hence it is important that the hormone should be present in a correct amount for proper function.

Adrenaline is the hormone which is secreted during an emergency. The gland which secretes adrenaline is called adrenal gland.

When adrenaline is secreted into the blood it prepares our body for action. It speeds up heart beat and breathing, raises blood pressure and allows more glucose(Carbohydrate) to go into the blood to give us lot of energy quickly to run or fight. And hence it is an emergency hormone. When secreted in large amounts, it speeds up the heartbeat and hence supplies more oxygen to the muscles. It is secreted in the body when the body is under severe physical/emotional stress or depression.

Explanation: Hormones are chemical messengers whose secretion is maintained by endocrine glands. Adrenalin gland (is an endocrine gland) is situated above both kidneys. It helps in regulation (increasing) of blood pressure, heart beat, carbohydrate metabolism (during an emergency).

Insulin is the hormone injected to a patient with diabetes.

Explanation: This disease occurs due to high blood sugar level. This is due to inability of pancreatic glands to secrete sufficient amount of insulin. Injection of insulin hormone helps in its treatment. To regulate its level a feedback mechanism occur that makes sure that hormones are secreted in precise quantities and at right time.

If the cerebellum is not functioning properly than involuntary processes will get disturbed. It is responsible for maintaining body posture and equilibrium by controlling & coordinating muscular movements. But if it's not working properly then the balance of the body gets disturbed. We will not be able to walk properly. Thus the body parts which are responsible for our movement will not respond.

Explanation: Cerebellum is the part of Hind-brain. This portion of the brain is maintaining the voluntary actions of a body which are under the control of a person. Example: Picking up of a pen.

Reflex arc is the neural pathway which controls an action response. It allows the reflex action to act faster. The components of reflex arc are:

So the process goes as Stimulus → Receptor organ → Sensory nerve → Spinal cord (interneurons will act) →Effecter neurons →Effecter organs→ Response

The muscle cells move by contraction and relaxation by utilizing the energy in the form of ATP. Muscle contraction is initiated by signals sent by the CNS to the muscle fibres. During contraction, the muscles fibers shorten, the muscle pulls on the ligaments that connect the bones and the movable body parts.

During relaxation, the muscle fibres come to their original position. This movement of muscles cells or the muscle fibres results in the movement of the body parts.

The nervous system of vertebrates (including humans) constitutes the central nervous system (CNS) and the peripheral nervous system (PNS). The central nervous system consists of the brain and spinal cord. The peripheral nervous system (PNS) connects the central nervous system (CNS) to sensory organs (such as the eye and ear), other organs of the body, muscles, blood vessels and glands.

CNS is more protected as its main line of defence is the bones of the skull and spinal column, which create a hard physical barrier to injury. Brain in protected by cranium and spinal cord is protected by a cylindrical like column.

Explanation: Brain lies inside a bony box, called cranium while the spinal cord lies within the vertebral column or backbone, such bony structures protect them from mechanical injury and shock. Inside these bony structures lie a series of layers of tissue referred to as meninges. Also cerebrospinal fluid present in the brain and spinal cord serves as a pad to cushion the central nervous system from shock.

A reversible change in the position of plant parts due to a change in turgor pressure in certain specialized cells. The growth observed is independent, and has immediate response to the stimuli. Plants use electrical-chemical means to convey information from cell to cell. For movement to happen, cells change their shape by changing the amount of water in them, resulting in swelling or shrinking of the cell.

Turgor pressure is the force within the cell that pushes the plasma membrane against the cell wall. It occurs due to changes in the osmotic pressure of the cells involved in the movements. Turgor pressure within cells is regulated by osmosis and this also causes the cell wall to expand during growth. Osmosis is the process in which water flows from an area with a low solute concentration, to an adjacent area with a higher solute concentration until equilibrium between the two areas is reached, this helps in maintaining turgor pressure occurring through osmosis, help in maintaining equilibrium in plants to prevent turgor movement. The plants that lack turgor pressure show turgor movement.

Examples of turgor movement in plants are:

● Leaves of Mimosa plant folds and droops down when anyone touch them.

● Leaves of Medicago marina plants close or sleep at night whereas opens up during day time.

Explanation: It can be explained with the example of a complete process. It has been concluded that loss of turgor pressure within the leaves of Mimosa pudica is responsible for the reaction the plant has when touched. In that plant turgor pressure is different in the upper and lower pulvinar cells of the plant, and the movement of potassium and calcium ions throughout the cells cause the increase in turgor pressure. When touched, the pulvinus is activated and exudes contractile proteins, which in turn increases turgor pressure and closes the leaves of the plant.

Autonomic nervous system, in vertebrates, the part of the nervous system that controls and regulates the internal organs without any conscious recognition or effort by the organism. The autonomic nervous system regulates certain body processes, such as blood pressure and the rate of breathing. This system works automatically (autonomously).

The autonomic nervous system has two main divisions:

● Sympathetic

● Parasympathetic

After the autonomic nervous system receives information about the body and external environment, it responds by stimulating body processes, usually through the sympathetic division, or inhibiting them, usually through the parasympathetic division.

Functions of Sympathetic nervous system:

● It is responsible for the response commonly referred to as "fight or flight.

● It prepares the body to react to stresses such as threat or injury.

● It causes muscles to contract and heart rate to increase.

Functions of Para-sympathetic nervous system:

● It is referred to as "rest and digest."

● It controls functions of the body at rest.

● It helps maintain homeostasis in the body.

● It causes muscles to relax and heart rate to decrease.

Para-sympathetic nervous system can be controlled by factors (such as exercise and experience) that can help people exert a level of control over the sympathetic responses. The two systems generally do not function well at the same time. That is, when faced with imminent danger, the body will divert blood flow from parasympathetic nerve functions (such as digestion) to sympathetic nerve functions (such as muscle contraction and heavy breathing to run away).

When the movement in plants is growth dependent then it is called tropic movement. It is a directional movement in response to a stimulus. For example:

(i) Phototropism- Movement towards the direction of light. Example: Movement of the shoot of plant upwards towards the light.

It can be explained by the help of this diagram. This kind of movement is induced by light. The stem mostly grows and turns towards the source of light, therefore it is said to be positively phototropic. Auxin distribution controls phototropism.

In 1, Sunlight strikes the plant from directly above. Auxin (pink dots) encourages growth straight up. In 2, 3, 4, Sunlight strikes the plant at an angle. Auxin is concentrated on one side, encouraging growth at an angle from the preceding stem. More growth of the stem on the shaded side is due to more accumulation of auxin on the shaded side than on the illuminated side.

This unequal distribution of auxins on the two sides may be due to following two reasons:

(i) Translocation of auxins from illuminated side to the shaded side.

(ii) Inhibition of auxin synthesis in the illuminated side(light side).

(ii) Geotropism- Movement in the direction of gravity or away from gravity. Example: Root growing downward.

The effects of gravity on plants are not like those of light and temperature because it is both continuous in action and constant in strength. Primary roots and certain other portions of the root system tend to grow directly toward the centre of gravity and hence called positively geotropic.

Mechanism of Geotropism:

Geotropism too can be explained on the basis of differential (unequal) distribution of auxins. In a horizontally placed plant the auxin accumulation on the lower side of the stem and root apices due to gravity. In the stem higher concentration of auxin on the lower side of the apex stimulates its growth on that side. This results in the growth of the stem in the upward direction showing negative geotropism.

On the other hand, in the case of root, the higher concentration of auxin on the lower side inhibits the growth on the upper side than on the lower side. As a result the root apex grows downward (i.e., Positive geotropism)

When a potted seedling was placed horizontally within a dark wooden chamber, the stem was seen to bent upwards, i.e., in a direction opposite to the pull of gravity. This is a negative geotropism. When roots were taken out of the pot, they showed a curvature or bend opposite to the bend of the stem. This curvature is in the direction of the pull of gravity. It is positive geotropism.

(i) Auxin- It is a growth promoting hormone.

● The primary function of the auxin hormones is to elongate plant cells in the stem. Auxin by some mechanism breaks the bonds holding its cellulose fibers together. These broken bonds give the cell wall greater flexibility and expandability so that more water can enter the cell by diffusion, causing the cell itself to elongate.

● Auxins are also responsible for adventitious root development, secondary growth in the vascular cambium,

● Inhibition of lateral branching, and fruit development. In fact, seedless fruits can be artificially created by applying synthetic auxin to plants; this causes fruit to develop even though fertilization (and thus seed formation) has not occurred.

(ii) Abscisic acid- It is the growth inhibitory hormone or the stress hormone.

● It restrains the growth and causes the falling of old leaves.

● It maintains the period of dormancy in seeds and buds.

● It also causes the guard cells of the stomata to close when the plant is losing too much water.

(a) Thyroxine

This hormone is secreted by the thyroid gland. The thyroid is located in the neck/throat. region. It is the main hormone secreted into the bloodstream. It regulates carbohydrate, protein & fats metabolism process. It plays vital roles in digestion, heart and muscle function, brain development and maintenance of bones.

(b) Adrenaline

This hormone is secreted by adrenal. The adrenal gland is located above both kidneys. It regulates blood pressure (increasing) heartbeat, carbohydrate metabolism (during an emergency). Adrenaline is carried in the bloodstream and affects the autonomous nervous system, which controls functions such as the heart rate, dilation of the pupils, and secretion of sweat and saliva

(c) Insulin

This hormone is secreted by the pancreas. The pancreas is located below the stomach. It reduces and regulates the blood sugar level by a feedback mechanism. It, therefore, helps cells to take in glucose to be used for energy.

(d) Growth hormone

This is secreted by the pituitary gland (master gland). This gland is located in Mid-brain. It regulates growth and development. It stimulates the growth of essentially all tissues of the body, including bone.

(e) Testosterone

It is a sex hormone which is secreted by testis in males. The testis is located in the genital area. Its changes are associated with puberty. (Sexual maturity). It leads to the development of secondary male characters like deep voice, beard, etc

Human Brain: It is enclosed in the cranium (brain box) and is protected by cerebrospinal fluid which acts as a shock absorber. The human brain has three major parts or regions: (a) Fore-brain (b) Mid Brain (c) Hind Brain.

They also have components:

â Fore-brain

It is the most complex/specialized part of the brain.

(A)Cerebrum-

(i) Main thinking and largest part of the brain.

(ii) It has 3 main areas:

a) Sensory area- to receive impulses from sense organs via Receptors

b) Motor area- control voluntary movements.

c) Association areas- Reasoning, learning & intelligence.

(B) Thalamus – It relays sensory information to the Cerebrum.

(C) Hypothalamus- It forms the link between Nervous system & Endocrine system.

â Mid brain- It connects the fore-brain with the hind-brain. It is the portion of the central nervous system associated with vision, hearing, motor control, sleep/wake, arousal (alertness), and temperature regulation.

â Hind brain- Connects the Fore brain & Hind brain

a) Cerebellum – Controls & coordinates muscular movements, maintaining body posture and equilibrium.

b) Pons- Acts as a bridge between brain & spinal cord

c) Medulla oblongata- Controls involuntary actions like blood pressure, salivation, vomiting, etc.