Haryana State Board HBSE 10th Class Science Notes Chapter 7 Control and Coordination Notes.
Haryana Board 10th Class Science Notes Chapter 7 Control and Coordination
Animals – Nervous System
Importance of control and co-ordination:
Multicellular organisms are made-up of various organs and organ system. It is a basic need of the body to control and co-ordinate these organs and organ systems, so that they can function properly and accomplish the voluntary as well as involuntary functions.
Stimulus:
- An event that encourages action or creates sensation is called a stimulus. (Plural : Stimuli)
- All living organisms – humans, plants and animals respond to changes occurring in their surroundings. These changes work as stimuli.
Example: On seeing sudden bright sunlight, our eyes gets closed. Here, the sudden bright light is stimulus whereas closing of eyes is response.
Receptors:
A specialized structure in the human body that receives external stimuli is called a receptor. These receptors are located in our sense organs.
The main ones are:
- Gustatory receptors
- Olfactory receptors
- Thigmo receptors
- Photo receptors and
- Audio (phono) receptors
Nerve cell:
Nerve cells or neurons are the building as well as functional units of the nervous system. They carry information from one part of the body to another.
Nerve cell has three components:
- Cell body
- Dendrites and
- Axon
Nervous tissue:
Nervous tissue is made up of organized network of nerve cells or say neurons. It specializes in conducting messages through electrical impulses from one part of the body to another.
What Happens in Reflex Action
Reflex action:
- Reflex action is an involuntary and instant response of the muscles or glands to a stimulus.
- It takes place without involving the brain.
Example: We immediately pull-back our hands when we suddenly touch a hot vessel or when someone pricks us a pin.
Reflex arc:
The pathway or say the route taken by the nerve impulses in a reflex action is known as the reflex : arc. Reflex arcs allow rapid response.
Human Brain
There are two systems which co-ordinate different activities in humans:
- Nervous system and
- Endocrine system (or) Hormonal system)
Nervous system:
It controls and co-ordinates all the parts of the body. The nervous system co-ordinates muscles, thus allowing a person to perform activities such as dancing, reading, writing, etc. It also co-ordinates certain involuntary functions like heart beat and breathing.
Endocrine system (or Hormonal system):
There arexiertain glands in the endocrine system which release chemical substances (chemical messengers) called hormones in the body. Generally, hormones regulate the slow activities of the body such as growth, metabolism, etc.
Organization of human nervous system can be done under three classes. They are:
(A) Organs of Human Nervous System:
- Brain
- Spinal cord
- Nerves
Human Nervous System :
CNS (Central Nervous System) –
- Brain
- Spinal cord
PNS (Peripheral Nervous System) –
- 12 pairs of Cranial nerves
- 31 pairs of spinal nerves
Nerves:
- Sensory nerve
- Motor nerve
- Mixed nerve
Human brain: It is divided into three major parts-
- Fore brain
- Mid brain and
- Hind brain.
Fore brain: Fore brain is the main thinking part of the brain. It has regions which receive sensory impulses from various receptors.
Midbrain: Mid brain connects the forebrain and hind brain. It is the centre for visual and auditory reflexes.
Hind brain: It consists of
- Cerebellum which lies on dorsal side and
- Pons and
- Medulla oblongata.
Co-ordination in Plants:
Plant movement: Movement of individual parts of a plant such as root, leaves, etc. is possible when they are subjected to some external stimuli like sunlight, gravitational force, water, touch, etc. Such movements of plants are called plant movements. Types: (I) Tropism and (II) Nastism.
Movement due to Growth:
The movement (response) in a plant organ is due to the effect of an external and directional stimuli is called tropism or tropic movement. Stimulus and type of movement shown by the plants:
- Light – Photoperiodism
- Gravity – Geotropism
- Chemical – Chemotropism
- Water – Hydrotropism
- Touch – Thigmotropism
Plant hormone:
Plant hormones are special chemical compounds which are synthesized at one place/organ of the plants and migrate to the target organ to act. They play an important role in control and co-ordination in plants, as well as in growth, development and responses to the environment.
Types of plant hormones:
- Growth promoting hormones – (i) Auxins, (ii) Cytokinins, (iii) Gibberellins
- Growth resisting hormones – (i) Absicic acid (ABA)
Hormones in Animals:
Hormones:
- Basically, hormones are the chemical substances (chemical messengers).
- They play an important role in various metabolic processes.
Glands: There are two types of glands. They are –
- Exocrine glands and
- Endocrine glands
Glands and hormones they release:
- Adrenal – Adrenaline
- Thyroid – Thyroxine,
- Pituitary – Growth hormone and many other hormones
- Testes (in males) – Testosterone
- Ovaries (in females) – Estrogen and progesterone
- Pancreas – Insulin
Regulation of secretion of hormones:
Hormone secretion is regulated by the feedback mechanism. In general, a particular gland secretes a specific hormone which reaches to the target organ and performs its function. After the function is over, the brain receives a message to stop the gland to secrete the hormone further. This is how hormone secretion is regulated.