Control and Co-ordination, Class 10

 

Control and Co-ordination

Control and Co-ordination in Animals:  In animals, the nervous system and hormonal system are responsible for control and coordination.

NERVOUS CONTROL	CHEMICAL CONTOL
·    Information is carried in the form of impulses through the nerves	·    Information is carried through hormones and chemicals in blood.
·    Changes lasts for short period.	·    Changes lasts for long period.
·    Faster/ quicker in process.	·    Slower process
·    Body receives stimulus from the external environment.	·    Body receives stimulus from the internal environment.
·    There is no feedback mechanism involved.	·    Feedback mechanism is present.

 

Receptors: Receptors are the specialized tips of the nerve fibres that collect the information to be conducted by the nerves.
Receptors are in the sense organs of the animals.
These are classified as follows :

·         Phono-receptors: These are present in inner ear.
Functions: The main functions are hearing and balance of the body.

·         Photo-receptors: These are present in the eye.
Function: These are responsible for visual stimulus.

·         Thermo-receptors: These are present in skin.
Functions: These receptors are responsible for pain, touch and heat stimuli.
These receptors are also known as thermoreceptors.

·         Olfactory-receptors: These are present in nose.
Functions: These receptors receive smell.

·         Gustatory-receptors: These are present in the tongue.
Functions: These helps in taste detection.

Human Nervous System: The nervous system in humans can be divided into three main parts
1. Central Nervous System: The central nervous system is composed of the brain and the spinal cord. The brain controls all the functions in the human body. The spinal cord works as the relay channel for signals between the brain and the peripheral nervous system.

2. Peripheral Nervous System: The peripheral nervous system is composed of the cranial nerves and spinal nerves. There are 12 pairs of cranial nerves. The cranial nerves come our of the brain and go to the organs in the head region. There are 31 pairs of spinal nerves. The spinal nerves come out of the spinal cord and go to the organs which are below the head region.

3. Autonomous Nervous System: The autonomous nervous system is composed of a chain of nerve ganglion which runs along the spinal cord. It controls all the involuntary actions in the human body. The autonomous nervous system can be divided into two parts :

·         Sympathetic nervous system.

·         Parasympathetic nervous system.

Sympathetic Nervous System: This part of the autonomous nervous system heightens the activity of an organ as per the need. For example, during running, there is an increased demand for oxygen by the body. This is fulfilled by an increased breathing rate and increased heart rate. The sympathetic nervous system works to increase the breathing rate the heart rate, in this case.

Parasympathetic Nervous System: This part of the autonomous nervous system slows the down the activity of an organ and thus has a calming effect. During sleep, the breathing rate slows down and so does the heart rate. This is facilitated by the parasympathetic nervous system. It can be said that the parasympathetic nervous system helps in the conservation of energy.

Nervous System: The nervous system is composed of specialized tissues, called nervous tissue. The nerve cell or neuron is the functional unit of the nervous system. It is the nervous system which is mainly responsible for control and coordination in complex animals.

Functions of the nervous system

·         Nervous system receives information from the environment.

·         To receive the information from the various body.

·         To act according to through muscles and glands.

A neuron is the structural and functional unit of the nervous system.

 Neuron: Neuron is a highly specialized cell which is responsible for the transmission of nerve impulses. The neuron consists of the following parts

(i) Cyton or cell body: The cell body or cyton is somewhat star-shaped, with many hair like structures protruding out of the margin. These hair-like structures are called dendrites. Dendrites receive the nerve impulses.

(ii) Axon: This is the tail of the neuron. It ends in several hair-like structures, called axon terminals. The axon terminals relay nerve impulses.

(iii) Myelin sheath: There is an insulator cover around the axon. This is called myelin sheath. The myelin sheath insulates the axon against nerve impulse from the surroundings.

Types of neuron

·         Sensory neuron: These neurons receive signals from a sense organ.

·         Motor neuron: These neurons send signals to a muscle or a gland.

·         Association or relay neuron: These neurons relay the signals between sensory neuron and motor neuron.

 

Synapse: The point contact between the terminal branches of axon of one neuron with the dendrite of another neuron is called synapse.

Neuromuscular Junction (NMJ): NMJ is the point where a muscle fibre comes in contact with a motor neuron carrying nerve impulse from the control nervous system.

Transmission of nerve impulse: Nerve impulses travel in the following manner from one neutron to the next :

Dendrites → cell body → axon → nerve endings at the tip of axon → synapse → dendrite of next neuron.

Chemical released from axon tip of one neuron, cross the synapse or neuromuscular junction to reach the next cell.

Spinal cord: Spinal cord controls the reflex actions and conducts massages between different parts of the body and brain.

Reflex Action: Reflex action is a special case of involuntary movement involuntary organs. When a voluntary organ is in the vicinity of sudden danger, it is immediately pulled away from the danger to save itself. For example, when your hand touches a very hot electric iron, you move away your hand in a jerk. All of this happens in flash and your hand is saved from the imminent injury. This is an example of reflex action.

Reflex Arc: The path through which nerves signals, involved in a reflex action, travel is called the reflex arc. The following flow chart shows the flow of signal in a reflex arc.
Receptor → Sensory neuron → Relay neuron → Motor neuron → Effector (muscle)
The receptor is the organ which comes in the danger zone. The sensory neurons pick signals from the receptor and send them to the relay neuron. The relay neuron is present in the spinal cord. The spinal cord sends signals to the effector via the motor neuron. The effector comes in action, moves the receptor away from the danger.

The reflex arc passes at the level of the spinal cord and the signals involved in reflex action do not travel up to the brain. This is important because sending signals to the brain would involve more time.
Although every action is ultimately controlled by the brain, the reflex action is mainly controlled at the level of spinal cord.

Protection of brain and spinal cord

·         Brain is protected by a fluid filled balloon which acts as shocks absorber and enclosed in cranium (Brain box)

·         Spinal chord is enclosed in vertebral column.

Muscular Movements and Nervous Control: Muscle tissues have special filaments, called actin and myosin. When a muscle receives a nerve signal, a series of events is triggered in the muscle. Calcium ions enter the muscle cells. It result in actin and myosin filaments sliding towards each other and that is how a muscle contracts.

Contraction in a muscle brings movement in the related organ.

Human Brain: Human brain is a highly complex organ, which is mainly composed of nervous tissue. The tissues are highly folded to accommodate a large surface area in less space. The brain is covered by a three-layered system of membranes, called meninges. Cerebrospinal fluid is filled between the meninges. The CSF providers cushion the brain against mechanical shocks. Furthermore, protection. The human brain can be divided into three regions, viz. forebrain, midbrain and hindbrain.

Parts of Human Brain :

·         Fore-brain: It is composed of the cerebrum.

·         Mid-brain: It is composed of the hypothalamus.

·         Hind-brain: It is composed of the cerebellum, pons, medulla oblongata.

Fore Brain

It is made up of the cerebrum and diencephalon.

Cerebrum

• ·         It is the largest part of the brain. Which is divided into two parts, which are called cerebral hemispheres. These cerebral hemispheres divide into right and left. Their outer surface is highly folded due to the presence of outgrowths and grooves.
• ·         Each cerebral hemisphere is hollow internally. And their walls have inner and outer regions. The outer region is called the cerebral cortex. In which there is a cell body of neuron, and due to its gray color, it is called gray matter.
• ·         The inner region is made of white axon fibers, it is called white matter.
• ·         If the hemispheres are cut in the transverse direction, then an empty space or cavity will be found inside it. These cavities are called lateral ventricles.
• ·         The two cerebral hemispheres are interconnected by the corpus callosum, which is a sheet-like sheet of crisscrossed nerve fibers.
• ·         The left side of the brain controls the right side of the body. And so on, the right side controls the left side.

 

The cerebral cortex has three functions

• ·         It initiates voluntary muscle contractions. and controls them.
• ·         The cerebral cortex receives information coming from sensory organs, such as eyes, ears, nose, etc. and acts on them.
• ·         It performs mental functions like thinking, reasoning, planning, remembering etc.

 

Thalamus

• ·         It is an egg-shaped body made of gray matter, which is located in the middle of the bottom of the brain.
• ·         The thalamus serves as the transmission center for sensory impulses that travel to the brain. Like feelings of pain and pleasure.

 

Hypothalamus:

• ·         This is the part of the brain that is located below the thalamus.
• ·         The hypothalamus controls induced behaviour, such as eating, drinking, hatred, anger, love and lust (Labido).
• ·         It is also the regulatory center for body temperature and the amount of fluids within the body.
• ·         The pituitary gland is located below it.
• ·         The sedative and inhibitory hormones are secreted by the hypothalamus. Which controls the secretion of hormones of the pituitary gland.

 

Mid Brain

• It is a small tubular part between the anterior and posterior brain. Also called mesencephalon,
• ·         The mesencephalon (middle brain) is made up of four bodies. These bodies are called corpora quadrigemina.
• ·         The upper two bodies are called tectum and the lower bodies are called tegmentum.
• ·         Tectum is responsible for seeing and tegmentum for hearing.

 

Hind brain

It is composed of the cerebellum, pons, and medulla oblongata.

A.   Cerebellum

• ·         It is the second largest part of the brain.
• ·         It is located below the base of the brain. It has many grooves. Its cortex is also made of gray matter.
• ·         The cerebellum (cerebellum) performs the function of maintaining the balance of the body and maintaining coordination in muscular activities.
•  

B.   Medulla oblongata

• ·         This is the last part of the brain. which is attached to the spinal cord.
• ·         Medulla oblongata controls salivation, vomiting, heart beat, peristalsis of the alimentary canal and many other involuntary actions.
• ·         It is the center of breathing, coughing, swallowing etc. It is also called Myelencephalon

 

C.   Pons

• ·         It is also called Metencephalon. The pons regulates breathing.
• ·         The respiratory center in the pons is a structure called the pneumotaxic centre. Which controls the amount of air during respiration and the rate of respiration.
• ·         Brainstem is make up of The midbrain (mesencephalon), pons (methencephalon), and medulla oblongata (myelencephalon) .

CHEMICAL CONTROL

Endocrine System: The endocrine system is composed of several endocrine glands. A ductless gland is called endocrine gland. Endocrine gland secretes its product directly into the bloodstream. Hormones are produced in the endocrine glands. Hormone is mainly composed of protein. Hormones assist the nervous system in control and co-ordination. Nervous do not react to every nook and corner of the body and hence hormones are needed to affect control and coordination in those parts. Moreover, unlike nervous control, hormonal control is somewhat slower.

Hormones: These are the chemical messengers secreted in very small amounts by specialised tissues called ductless glands. They act on target tissues/organs usually away from their source. Endocrine System helps in control and coordination through chemical compounds called hormones.

Endocrine Gland: A ductless gland that secretes hormones directly into the bloodstream.

1.   Adrenaline ( Fear and fight hormones) Secreted by Adrenal gland Which is Located just above the kidneys.

Functions of Adrenaline:

 

·         Adrenaline acts on specific tissues which includes the heart and as a result the heart starts beating faster and O2 supplied to the muscle increases.

·         The blood supplied to the digestive system and the skin due to the contraction of muscles around the small arteries in these regions and it is because of this that the blood supply is diverted to the skeletal muscles.

·         Breathing rate also increases due to contraction of diaphragm and rib muscles.

As a result of these responses the animal becomes ready to deal with the situation.

2.   Thyroxin- Thyroid Gland - Neck

·         Thyroxin regulates fat, carbohydrates and protein metabolism in body and hence provide a balance for growth.

·         Iodine is essential for the synthesis of thyroxin and hence if there is iodine deficiency in diet then we suffer from goitre in which the thyroid gland does not function properly (symptom is swollen neck.).

·         People living in hilly regions suffer more from goitre due to deficiency of iodine in their diet as these regions are far away from the seas and the oceans are rich in iodine.

 

3.   Growth Hormone -Pituitary Gland - Brain

·         It regulates the growth and development of body.

·         If there is deficiency of this hormone during childhood then the person suffers from dwarfism and there is over secretion then person suffers from gigantism.

4.   Sex Hormones (regulates secondary sexual characteristics with onset of puberty)

Testosterone in male

Oestrogen + progesterone in females

5.   INSULIN  Pancreas  near the stomach

Pancreas is also a Dual Gland Because:

• Secretion of hormone ( insulin + glycogen)
• Secretion of digestive juices like pancreatic juice, amylase, pancreatic trypsin, pancreatic lipase.
• Insulin helps to regulate the blood sugar level in the body and hence if the insulin is not secreted in proper amounts then sugar level in blood rises and can lead to many harmful effects (diabetes).

Iodised salt is necessary because: Iodine mineral is essential part of thyronine hormone so it is important that we must consume iodised salt as in turn it is essential for thyroid gland as it controls carbohydrate, proteins and fat metabolism for best balance of growth deficiency of iodine might cause disease called goitre.

Diabetes: Cause : It is due to deficiency of insulin hormone secreted by pancreas that is responsible to lower/control the blood sugar levels.

Treatment : Patients have to internally administer injections of insulin hormone which helps in regulating blood-sugar level.

In case of flight or fight reaction to an emergency situation, Adrenal glands → release adrenaline into blood → which acts on heart and other tissues → causes faster heart beat → more oxygen to muscles → reduced blood supply to digestive system and skin → diversion of blood to skeletal muscles → increase in breathing rate.

Feedback mechanism: A type of self-regulating mechanism in which the level of one substance in body influences the level of another.

Control and Co-ordination in Plants: 

Co-ordination in Plants: Unlike animals, plants do not have a nervous system. Plants use chemical means for control and co-ordination. Many plant hormones are responsible for various kinds of movements in plants. Movements in plants can be divided into two main types :

1.    Tropic movement

2.    Nastic movement

Plants show two kinds of movements in response to stimulus.

 

Immediate Response (nastic movement)	Growth Related Response( tropic movement)
   These movements are shown by the sensitive parts of the plant.	   These movements are shown by all parts of the plant.
   No chemicals are involved rather plants show movement by changing the shape of their cells due to a change in their H2O concentration.	   Movement occurs due to secretion of hormones.
   Movement takes place for a short period of time and is immediately visible to the eyes.	   Movement occurs for a longer duration and the change is not visible immediately.
    Non directional movement.	    Directional movement.
   Action takes place away from the point that receive stimulus.	   Growth takes place at the same point where it receives the hormone.
    It does not provide any growth	    Growth occurs in the plant.
   E.g. drooping of leaves of touch-me not plant when touched.	   E.g. shoot growing towards sunlight, ripening of fruits.

 

1. Tropic Movement: The movements which are in a particular direction in relation to the stimulus are called tropic movements. Tropic movements happen as a result of growth of a plant part in a particular direction. There are four types of tropic movements.

(i) Geotropic movement: The growth in a plant part in response to the gravity is called geotropic movement. Roots usually show positive geotropic movement, i.e. they grow in the direction of the gravity. Stems usually show negative geotropic movement.

(ii) Phototropic Movement: The growth in a plant part in response to light is called phototropic movement. Stems usually show positive phototropic movement, while roots usually show negative phototropic movement. If a plant is kept in a container in which no sunlight reaches and a hole in the container allows some sunlight; the stem finally grows in the direction of the sunlight. This happens because of a higher rate of cell division in the part of stem which is away from the sunlight. As a result, the stem bends towards the light. The heightened rate of cell division is attained by increased secretion of the plant hormone auxin in the which is away from sunlight.

(iii) Hydrotropic Movement: When roots grow in the soil, they usually grow towards the nearest source of water. This shows a positive hydrotropic movement.

(iv) Thigmotropism Movement: The growth in a plant part in response to touch is called thigmotropism movement. Such movements are seen in tendrils of climbers. The tendril grows in a way so as it can coil around a support. The differential rate of cell division in different parts of the tendril happens due to action of auxin.

2.Nastic Movement: The movement which do not depend on the direction from the stimulus acts are called nastic movement. For example, when someone touches the leaves of mimosa, the leaves droop. The drooping is independent of the direction from which the leaves are touched. Such movements usually happen because of changing water balance in the cells. When leaves of mimosa are touched, the cells in the leaves lose- water and become flaccid, resulting in drooping of leaves.

Plant hormones: Plant hormones are chemical which help to co-ordinate growth, development and responses to the environment.

Type of plant hormones: Main plant hormones are

·         Auxin: (Synthesized at shoot tip).

Function: Helps in growth.

Phototropism: more growth of cells towards the light.

·         Gibberellin: Helps in the growth of the stem.

·         Cytokinins: Promotes cell division.

·         Abscisic acid: Inhibits growth, cause wilting of leaves. (Stress hormone)

1.   Auxins

• Auxins help the cells to grow long and hence it helps in the growth of the stem.
• When the growing plant detects light, auxins are synthesised at shoot tips.
• As the light is coming from one side the auxins diffuse towards the shady side of the shoot and keeps on accumulating there
• The concentration of auxins stimulate the cells to grow longer on the side of the shoot which is away from light and thus the plants appear to bend towards light.

2.   Gibberellins

It helps in the growth of the stem.

3.   Cytokinins

It helps to promote cell division and hence high concentration of these hormones are found in the areas of rapid cell division like fruits and seeds.

4.   Abscisic Acid (ABA)

It is the inhibitory hormone which inhibits the growth in plant. E.g. weathering of leaves, ripening of fruits.