Chapter Notes: Control and Co-ordination- Class 10 Science
In this chapter, we will learn about various activities took place in humans and plants in such a systematic way that all organs can work efficiently. We will learn how our body control functions via nervous system and hormone secretions.
The nervous system composed of some special kind of tissues which are called nervous tissues. Neurons and nerve cells are two functional unit of nervous system. In complex organism nervous system is responsible for all kind of control and co-ordination like in humans.
- Nervous system receives information from the surroundings.
- It also receives information from other bodies.
- Then act accordingly through muscles and glands.
Neuron is the structural and functional unit of nervous system.
- Motor neuron- Neurons send signals to muscles and glands.
- Sensory neuron- Receive signals from sensory organs.
- Relay neuron- Neurons relay the signals between motor and sensory neurons.
- The information from receptors transmitted at the end of dendrites of nerve cell as form of a chemical reaction which created an electric impulse later.
- This impulse travels from dendrites to axon through cell body.
- Then this electric impulse created further chemicals at the end of axon.
- These chemicals cross the synapse and initiate similar electric impulse at dendrite of other neurons.
- Similarly respond signals transferred to muscles or gland through same synapse.
A typical neuron consists of cell body, axon, and dendrites.
- Cell body contains nucleus.
- Dendrites get the information from the surrounding which are received by dendrite tips and set off the electrical impulse which will travel to axon through cell body.
- Myelin sheath is an insulator covering around the axon. This sheath insulates the axon from other impulse for the surroundings.
Synapse- This is the gap between the nerve ending of one neuron and dendrites of second neuron where electrical signal converts into chemical signals and then further transmitted.
There are three types of responses in human body –
- Voluntary- Controlled by our fore brain like Writing, talking etc.
- Involuntary- Controlled by hind brain and mid brain like heart beats, vomiting etc.
- Reflex action- Controlled by spinal cord like withdrawal of hand from some heat surface.
Sometimes we need to respond faster so we can save our body from harm. In this scenario, we need to respond taken by our spinal cord not by our brain to save time so our body would be protected from any kind of injury.
- Cerebral reflex
- Spinal reflex
This is the pathway through which reflex action occurs.
NMJ is the point where muscle fibers come in contact with motor neurons which are carrying nerve impulse from CNS.
The nervous system of the human body can be categorized into three main parts-
CNS is composed of brain and spinal cord. The brain controls all the activities in human body. The spinal cord works as the relay channel between the PNS and the brain.
PNS is composed of the cranial nerves and the spinal nerves. There is 12 pair of cranial nerves in human body with 31 pairs of spinal nerves. The cranial nerves comes out from brain and go to organ with in the brain while spinal nerves come out from spinal cord and go to organ below the head region.
ANS composed of chain of nerve which runs along spinal cord. It controls the involuntary activities in human body.
- Sympathetic nervous system– SNS serves for increasing any organ activities as per demand.
- Parasympathetic nervous system– PNS serves to slow down any organ activity when there is less need of it.
The brain is composed of the cerebrum, cerebellum, and brainstem.
It is the largest and main thinking part of the brain. It comprises of:-
- Cerebrum- It is responsible for reasoning speech, intelligence, hearing and use of information. It combines all the information from different receptors and interpreted after combining them. It consists of Sensory area, association area and motor area.
- Olfactory lobes- Mainly, responsible for smell from different receptors. This is pair of small solid club shaped bodies separated from each other.
- Hypothalamus- This part control urge for drinking, eating etc with body temperature.
Mid brain controls reflex movements of eye pupil, visual reflexes for focusing on the object. It also controls movement of head, neck, and trunk. It works to connect forebrain and hindbrain.
- Cerebellum- It controls different voluntary muscular activities. It maintains the posture of the body and equilibrium of the body during various activities.
- Pons – Lies above the medulla and take part in respiration in human body.
- Medulla oblongata- It controls involuntary actions like breathing, BP, etc and regulates reflex responses like salivation and vomiting. It is found continuously with spinal cord.
It is long tubular bundle of nervous tissues arising from medulla oblongata. It transmits neural signals between brain and all other parts of the body.
Protection of brain and spinal cord
- Brain is protected by fluid filled balloon which works as a shock absorber and enclosed in cranium which is known as brain box.
- Spinal cord is protected by vertebral column in which it is enclosed.
Muscles have some filaments know as actin and myosin. When muscles gets the nerve signals some actions took place due to which calcium ions enters into muscle cells. It cause actin and myosin move towards each other due to which muscle contracts.
Limitation of electric communication- nervous system
Nervous system is limited to only those cells which are connected to nervous tissues.
Electric signals cannot transmit immediately one after other.
There are Hormones (Chemical messengers) which regulates biological process, secreted by endocrine glands (a ductless gland). Hormones are mainly composed of proteins.
Thyroid gland- It produces thyroxin that regulates carbohydrate, protein and fat metabolism in human body. Insufficient secretion of the thyroxin leads to swelling in throat known as goiter.
Adrenal gland- It produces adrenaline and it is secreted at the time of fear, fight or flight in human body. It is also known as hormone of emergency and also helps to regulate the salt level in blood.
Pancreas- It produces insulin and glucagon which regulate glucose metabolism in human body. The deficit secretion of insulin cause the blood sugar increase which causes a condition called diabetes.
Testis- It produces male hormone known as testosterone required male secondary sexual characteristics in human body like beard and moustaches.
Pituitary gland- It secretes growth hormone that regulates the growth and development of an organism.
Ovaries- It produces estrogen needed for sexual development in female body.
Feedback mechanism is a mechanism that tends to initiate (accelerate) or to inhibit (slow down) a process.
Feedback mechanisms help regulate biochemical pathways. (a) In negative feedback, the end product accumulates and inhibits the action of the first enzyme thereby slowing the reaction. (b) In positive feedback, the end product stimulates an enzyme in the pathway to increase overall production.
It is controlled by phyto-hormones and external stimulus.
These can be classified again into 5 types. They are:
- Phototropism (Due to light)-When the movement of a plant is in response to light. The shoot system of a plant exhibits phototropism and towards the light.
- Geotropism (Due to gravity) – When the movement of a plant towards the soil. The root system of a plant exhibits geotropism and towards the earth’s gravity.
- Hydrotropism (Due to water) – When the movement of a plant towards the water. The stimulus here is water.
- Chemotropism (Due to chemicals) – When the movement of plants in response to any chemical stimulus. During reproduction pollen tube moves towards the ovule in flower.
- Thigmotropism (Due to touch) – When there is a directional movement in plants in response to touch. For e.g. the plant tendrils climb around any touch which support it.
Note- Growth of plant can be both towards the stimulus ( positive tropism) or away of it (negative tropism)
Nastic movements in plants are non-directional movements which are independent of any stimulus and even growth.
- Thigmonasty- The leaves of a Mimosa pudica (touch me not plant), fold up when touched. These kinds of changes occur due to the changes in the amount of water in the leaves.
- Photonasty- Nastic movement in response to light