Control and Coordination

Control and Coordination

All the living organisms respond and react to changes in the environment around them. The changes in the environment to which the organisms respond and react are called stimuli such as light, heat, cold, sound, smell, touch, pressure etc. For example –

1. Take off the hand on touching a hot object.
2. Catching a ball by fielder.

The response which a living being makes in relation to external stimuli is called control and coordination. Both plants and animals respond to stimuli but in a different manner.

• Control and coordination are provided by nervous and muscular tissues.
• Nervous tissue is made up of an organized network of nerve cells or neurons, and is specialized for conducting information via electrical impulses from one part of the body to another.

It is nervous system which is mainly responsible for control and coordination in complex animals.

Nervous system

Nervous system is mainly composed of brain, spinal cord and nerves. Sense organs (nose, eyes, ears, tongue and skin) are a part of nervous system. The network of nerve cells and fibres which transmits nerve impulses between parts of the body. The nervous system is a complex network of nerves and cells that carry messages to and from the brain and spinal cord to various parts of the body. In vertebrates it consists of two main parts, the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord. The PNS consists mainly of nerves, which are enclosed bundles of the long fibers or axons, that connect the CNS to every other part of the body.

Function of nervous system

• Receive the information from environment by sense organs.
• Transportation of information to brain through spinal cords and nerves.
• After analyzing the information, it reacts accordingly through muscles and glands.

For example when we touch a hot object, our skin helps us to sense the heat, the nerves carry the impulse to the brain through spinal cord, and then the brain sends impulse to muscles to contract and take off the hands.

Receptors

Receptors are specialized tips of some nerve cells that detect the information from the environment and are sensitive to the change in environment. These receptors are located in our sense organs. 

Ear : (Phonoreceptors) Responsible for hearing,  balance of the body.
Eyes : (Photoreceptors) Responsible for seeing, detecting light.
Skin : (Thermoreceptors) Responsible for feeling (Heat or cold), Touch of external stimuli.
Nose :  (Olfactory receptors) Responsible for Smell detection.
Tongue : (Gustatory receptors) Responsible for Taste detection.

Neuron

It is the structural and functional unit of nervous system. Neurons are specialized cells which are combined to form nerves of the nervous system. As nerves are emerged from brain and spinal cord and branch out to almost all parts of the body, so neurons are also called unit of nervous system.

Parts of Neuron :

Dendrite : Acquires information, these small branch like projection of the cell make connections to another neurons and receive the nerve impulses.
Cell body : Acquired information travels as an electrical impulse, This main part has all the necessary components of the cell. Such as the nucleus, endoplasmic reticulum, ribosome and mitochondria. If the cell body dies, the neuron dies.
Axon : Longest fibre on the cell body is called axon. It transmits electrical impulse from cell body to dendrite of next neuron. The axon terminals relay nerve impulses.
Synapse :It is the gap between the nerve ending of one neuron and dendrite of the other neuron. Here electrical signal is converted into chemical signal for onward transmission.

Working of Neurons

Neurons are responsible for transmitting message from brain to body parts and vice versa. When receptors sense anything, a chemical reaction is triggered, this chemical reaction causes an electric impulse in dendrites. This impulse travels through the body of neuron to axon endings. Tiny amount of chemical is released in synapse by axon endings when impulse reaches there. This chemical crosses the synapse and reach to tip of dendrites where it again produces electric impulse and then this impulse travels along neuron.

Types of Neuron

Sensory Neurons: These neurons transmit message from body parts to central nervous system (which is composed of the brain and the spinal cord)

Motor Neurons: These neurons transmit from central nervous system to body parts.

Relay Neurons: These neurons relay the signals within the central nervous system.

Control and Coordination in Humans

The nervous system in humans can be divided in two main parts,

1. Peripheral nervous system
2. Central nervous system

Central Nervous System

Central nervous system consists of brain and spinal cord. It is responsible for the control and coordination of the activities of nervous system. The function of a central nervous system is to respond to the messages it receives. It directs the motor neurons that are connected to the part of the body which will respond to the stimulus.

The central nervous system collects information from all the receptors in our body.

Brain

The highest coordinating centre in our body is brain which is located inside the skull. Brain is protected by a bony structure in the skull called cranium. The three membranes called meninges surround the brain and protect it. The space between meninges is filled with a cerebrospinal fluid which helps the brain from mechanical shocks. Cranial nerves arise from the brain.

Human brain has three parts – 

1. Forebrain (cerebrum)
2. Mid brain 
3. Hind brain 

Forebrain (cerebrum):  The main thinking part of the brain is cerebrum. It is a place for faculties such as learning, reasoning, intelligence, personality, etc. All our thoughts and actions are controlled by the cerebrum. The association area of cerebrum controls thinking and memory and stores information and experiences. The sensory area of cerebrum receives information from sense organs and gives sensation. The motor area of the cerebrum sends instructions to various muscles to perform different function. All the voluntary actions are coordinated by the cerebrum.

Mid Brain: It controls cerebral reflexes like change in size of pupil, blinking of eye.

Hind brain: It consists of pons, cerebellum and medulla. The function of hindbrain is to control reflex movements of head, neck and trunk in response to visual and auditory stimuli. It also controls the reflex movements of the eye muscles.Pons helps in regulating respiration, cerebellum helps in maintaining posture and balance of the body and medulla controls various involuntary actions such as heartbeat, breathing, blood pressure, coughing, sneezing, secretion of saliva, etc. 

Functions of Brain

• Brain receives nerve impulses which carry information from the sense organs of the body.
• Brain responds to these impulses by sending instructions to muscles and glands which function accordingly.
• Brain correlates stimuli from different sense organs and produce appropriate and intelligent response.
• It coordinates the activities of the body.
• It stores information.

Spinal Cord

Spinal cord begins from medulla and extends downwards. Spinal cord is enclosed in bony structure called vertebral column at back centre of body. There are 31 pairs of nerves that arise from spinal cord. It is also surrounded by membranes called meninges. Spinal cord is concerned with the spinal reflexes and conducts nerve impulses to and from the brain. 

Functions:

• It carries message between brain and nerves.
• It controls spinal reflexes.

Peripheral Nervous System

The peripheral nervous system is made of all the nerves of the body. There are three types of nerves which make the peripheral nervous system, cranial nerves, spinal nerves and visceral nerves. All these nerves enter or leave the central nervous system.

Cranial nerves : There are 12 pairs of cranial nerves. The cranial nerves come out of the brain and go to sense organs and muscles in the head region.

Spinal nerves : There are 31 pairs of spinal nerves. The spinal nerves come out of the spinal cord and go to the sense organs and muscles which are below the head region. These nerves carry messages to brain through spinal cord.

Visceral nerves : They come out of the brain and spinal cord and go to the internal organs (like heart, kidneys etc.)

Peripheral nerves can further be divided into two parts.

i) Voluntary nervous system – It is responsible for the actions which we do in conscious control of brain. (like writing, speaking, walking etc.), Controlled by fore brain.
ii) Autonomic (Involuntary) nervous system – It is responsible for the actions which occur without the conscious control of the organisms or we can say they are not under the control of will. (like beating of heart, breathing, sweating working of kidney, digestion etc.), Controlled by mid and hind brain.

Reflex Action and Reflex Arc

Reflex Action – Reflex action is quick, sudden and immediate response of the body to a stimulus. E.g., Knee jerk, withdrawal of hand on touching hot object. Reflex action is the one which we perform automatically and is not under the voluntary control of the brain. Under reflex action same stimulus produces same kind of response every time. Movement of diaphragm, coughing, sneezing, yawning, blinking of eyes, immediately moving hand away on unknowingly touching hot plate, etc., are examples of reflex action.These are the actions which we do without thinking to protect ourselves. Reflex action is an automatic response to a stimulus, Controlled by spinal cord.

 

Reflex Arc – The pathway taken by nerve impulses in a reflex action is called reflex arc or The pathway through which nerve impulses pass during reflex action is called reflex arc.

The reflexes which involve only spinal cord are called spinal reflexes. The reflexes which involve brain are called cerebral reflexes.

Cerebral reflexes occur in the organs present in the head. These organs are directly connected to the brain. For example, when we are in dim light the pupil of our eye is big so that more light can enter into our eyes and when we are in bright light then the pupil of our eye automatically gets small. This automatic expansion and contraction of pupil is an example of cerebral reflexes.

Protection of Brain and Spinal Cord

(a) Brain : Brain is protected by a fluid filled balloon which acts as shock absorber and is enclosed in cranium (skull or brain box).

(b) Spinal Cord : Spinal cord is enclosed in vertebral column.

Coordination between Nervous and Muscular Tissue

 

Control and Coordination in plants

Despite not having sense organs plants can also sense things and respond to them. Plants respond to things like light, gravity, touch, water etc. These are environmental stimuli for a plant. Plants coordinate their behaviour by using their hormones and respond to the environmental changes. This they do by affecting the growth of a plant.

Movements in plants :Plants are fixed at one place and cannot physically move from one place to another. But plants still show movement by using hormones under the influence of stimuli. This movement is noticed in the unequal growth of the two regions of a plant.For example, auxin hormone speeds up the growth of a stem. So if one side of a stem has more auxin hormone than the other, then the side of stem which has more hormones will bend. This shows movement of a plant.

Plant movement due to external stimuli are of two types: Tropism and Nasties

Tropisms

Tropic movements happen as a result of growth of a part of a part of plant in a particular direction. When the direction of external stimulus decides the direction of response in the form of growth it is called tropism. Thus, tropism is the directional growth movement of a plant part. It can be in the direction of the stimulus or away from the stimulus. Therefore,

If the growth of a plant is in the direction of stimulus, it is called positive tropism.
If the growth of a plant is in the opposite direction or away from that of a stimulus, it is called negative stimulus.

Types of Tropism

There are five stimuli in the environment. They are light, gravity, chemical, water and touch. These stimuli give five types of tropism. They are Phototropism, Geotropism, Chemotropism, Hydrotropism and Thigmotropism.

Phototropism
When a plant part moves in response to light, it is called phototropism.The stem and leaves of a plant moves in the direction of sunlight. So, when a plant is grown in an open ground where sunlight is coming from above then the stem of a plant grows straight in an upward direction. If, however, a plant is kept at a place where sunlight is coming from only one direction then the stem of a plant bends in that direction only. On the other hand roots of a plant bend away from the direction of sunlight. If the stem of a growing plant moves or bends towards light, it is positive phototropism and if the root of a plant moves away from light, this means the roots of a plant shows negative phototropism.

This happens because of the action of auxin hormone.

• When the sunlight is coming from top, then the auxin hormone present at the tip of the stem spreads uniformly down the stem making it grow straight up.
• When the sunlight falls from only one side then the auxin hormone prefers to stay in shade and collects on other side.
• Since there is more auxin hormone on the other side of the stem, it makes that side grow faster. Thus, the stem bends towards sunlight.
• Auxin hormone has opposite effect on the roots of a plant. That is why if sunlight falls on the right side of the roots, auxin hormone collects on the left side and hampers their growth from that side. That is why, roots bend towards left and vice versa.

Geotropism
When a plant part moves in response to gravity, it is called geotropism. Roots of a plant grow towards the earth which moves in a downward direction, so they show positive geotropism and stem moves in the upward direction  from the pull of gravity so it shows negative geotropism.

Keep a potted plant in a normal position. We see that the roots are growing downwards and stem is growing upwards.
Now tilt the potted plant and keep it horizontally on the surface.
After a few days we notice that roots of the potted plant grow toward the earth and stem of the plant bends upwards away from the pull of gravity.

Chemotropism
When a plant part moves in response to chemical stimulus, it is called chemotropism. Here the stimulus is chemical. For example, the growth of pollen tube towards the ovule during fertilisation in a flower is called positive chemotropism.

 

Sugary substance acts as a stimulus for the growth of pollen tube towards the ovule. This happens because ripe stigma in the carpel of a flower secrets a chemical substance into the style towards the ovary. This sugary substance acts as a stimulus for the pollen grain which responds by growing a pollen tube in the downward direction into the style of a carpel and reaches the ovule of the flower for fertilisation.

Hydrotropism
When a plant part moves in response to water, it is called hydrotropism. Here the stimulus is water. Roots of a plant always moves towards water even if they have to grow against the pull of gravity or sideways. , so they show positive hydrotropism.

 

Thigmotropism
There are some plants which cannot stand upright on their own and need support. These plants are called climbing plants and have organs called tendrils. Tendrils are the thin thread-like growth on the stems and leaves of the climbing plants. Tendrils are sensitive to the touch of other object. When tendrils come in contact with other object, it bends towards the object by growing towards it, wind around the object and cling to it. This winding movement of a climbing plant is called thigmotropism.

Nasties or Nastic Movements

When the direction of response in a plant is not determined by the direction of stimulus, it is called nastic movement. Nastic movement is not the directional movement of the plant part.In nastic movement, whatever be the direction of stimulus, all the parts of the plant equally move in the same direction. This type of movement is generally seen in leaves, flower petals etc.

 

When we touch the sensitive place in plant electric impulses travel through the cells of the plant and act on plant hormone. The plant hormone migrate water from the cells of the pulvinus to the intercellular spaces of the other half of pulvinus. This loss of water makes pulvini lose firmness and thus its leaves droop.

After 15 to 30 minutes water comes back to the cells and leaf gets back to its original shape.

Some important plant hormones

• Auxin –  It controls growth of stem, fruits and roots.
• Gibberellins – It controls growth of stem, breaking dormancy of buds and seeds and growth of fruits.
• Cytokinin – It controls growth of plant by cell division, functioning of stomata, breaking dormancy seeds, these type of hormones present more in seeds and fruits.
• Abscissic acid – It controls inhibit growth, controls shedding of leaves, functioning of stomata and promote dormancy of seeds.

Hormones

Hormones are special chemical messengers in the body that are created in the endocrine glands. These messengers control most major bodily functions, from simple basic needs like hunger to complex systems like reproduction, and even the emotions and mood.

The best way to answer the question “what are hormones?” is to take a look at some of the major hormonal systems in the body. Hormones are created by glands, which are part of the endocrine system. The main hormone-producing glands are:

• Hypothalamus: The hypothalamus is responsible for body temperature, hunger, moods and the release of hormones from other glands; and also controls thirst, sleep and sex drive.
• Parathyroid: This gland controls the amount of calcium in the body.
• Thymus: This gland plays a role in the function of the adaptive immune system and the maturity of the thymus, and produces T-cells.
• Pancreas: This gland produces the insulin that helps control blood sugar levels.
• Thyroid: The thyroid produces hormones associated with calorie burning and heart rate.
• Adrenal: Adrenal glands produce the hormones that control sex drive and cortisol, the stress hormone.
• Pituitary: Considered the “master control gland,” the pituitary gland controls other glands and makes the hormones that trigger growth.
• Pineal: Also called the thalamus, this gland produces serotonin derivatives of melatonin, which affects sleep.
• Ovaries: Only in women, the ovaries secrete estrogen, testosterone and progesterone, the female sex hormones.
• Testes: Only in men, the testes produce the male sex hormone, testosterone, and produce sperm.

These glands work together to create and manage the body’s major hormones.

Major Types of Hormones

What do hormones do, exactly? The body has many different hormones, but certain types have a bigger role to play in the body’s health and well-being. Understanding these roles is important for those looking to protect and manage their health.

For women, Estrogen (or estradiol) is the main sex hormone. It causes puberty, prepares the body and uterus for pregnancy, and regulates the menstrual cycle. During menopause, estrogen level changes cause many of the uncomfortable symptoms women experience.

Progesterone is similar to estrogen but is not considered the main sex hormone. Like estrogen, it assists with the menstrual cycle and plays a role in pregnancy.

Cortisol has been called the “stress hormone” because of the way it assists the body in responding to stress. This is just one of several functions of this important hormone.

Melatonin levels change throughout the day, increasing after dark to trigger the responses that cause sleep.

Testosterone is the main sex hormone in men. It causes puberty, increases bone density, triggers facial hair growth, and causes muscle mass growth and strength.

When they are in proper balance, hormones help the body thrive, but small problems with hormones can cause serious and life-altering symptoms.

Endocrine System

In addition to the nervous system, the endocrine system also helps in coordinating the activities of our body.

A group of endocrine glands which produces various hormones forms the endocrine system. It is also known as hormonal system.

Gland

Gland is a cell, tissue or an organ which secretes a specific substance in the body.

 

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