Revision: Control and Co-ordination Science English Medium Class 10 CBSE

Nerve is a bundle of nerve fibres (axons) of separate neurons, enclosed in a tubular sheath.

• It is an automatic/quick/immediate, involuntary action in the body brought about by a stimulus.
• Involuntary functioning or movement of any organ or part of the body in response to peripheral nervous stimulation is called reflex action.

Reflex action is an automatic/quick/immediate, involuntary action in the body brought about by a stimulus. This mechanism prevents injury to the body by triggering a rapid and automatic response.

A reflex arc is the shortest route that can be taken by an impulse from a receptor to an effector.

The brain is protected by 3 membranous coverings called meninges (meninx: membrane) which continue backwards on the spinal cord.

Inflammation of the meninges is called meningitis.

Growth movements occurring in response to unidirectional external stimuli in a plant part are called tropic movements.

The direction of the response is related to the direction from which the stimulus comes. Such a response is known as tropism.

The term "tropic" comes from a Greek word "tropos" which means to "turn'.

Phototropism is the directional growth of a plant in response to light.

Positive phototropism is when a plant part, like a shoot, grows towards a light source.

Geotropism (also called gravitropism) is the directional growth of a plant in response to Earth's gravity.

Positive geotropism is when a plant part, such as a root, grows in the direction of gravity (downward).

Negative geotropism is when a plant part, such as a shoot, grows against the direction of gravity (upward).

Hydrotropism is the directional growth of a plant part in response to water or moisture.

Positive hydrotropism is when a plant part, such as a root, grows towards the source of moisture.

Thigmotropism is the directional growth of a plant part in response to touch or contact with a solid object.

Chemotropism is the growth movement of plant parts in response to chemicals.

• Voluntary actions are performed consciously, while involuntary actions (reflexes) occur automatically without conscious control.
• A stimulus is any change in the environment that initiates a reflex action.
• Reflex actions are quick, automatic responses to stimuli and do not require conscious thought.
• Examples of reflexes include withdrawal of the hand from a hot object, shivering in cold, and sweating in heat.
• All reflexes are triggered by sensory stimulation and result in either muscular movement or glandular secretion.

• Brain weighs ~1.35 kg (2% body weight, 80% water), protected in cranium, uses over 25% of body oxygen.
• Meninges & CSF — Three membranes: Dura mater → Arachnoid → Pia mater. CSF between them cushions the brain and fills the ventricles and the spinal canal.
• Forebrain — Cerebrum (85% brain mass; 2 hemispheres; 4 lobes — frontal, parietal, temporal, occipital); Diencephalon (contains thalamus and hypothalamus — regulates homeostasis).
• Midbrain — Has corpora quadrigemina (superior colliculi = visual; inferior colliculi = auditory reflexes) and red nucleus (controls posture and motor coordination).
• Hindbrain — Pons (connects brain parts); Cerebellum (balance, posture, muscle tone); Medulla Oblongata (controls heartbeat, respiration, and reflex actions like coughing, sneezing).

1. Plants do not have a nervous system or muscles, but they can still respond to stimuli like touch and light.
2. Plant movements are of two types – one independent of growth (like in the touch-me-not plant) and the other dependent on growth (like seedling movement).
3. In immediate response (like leaf folding), no growth occurs; the response is quick and due to electro-chemical signals passed from cell to cell.
4. Movement in plants happens by changing water content in cells, causing them to swell or shrink, unlike animal muscles which use proteins.

1. Hormones are chemical messengers that help in control and coordination by carrying signals through the blood to different parts of the body.
2. Adrenaline helps the body to face stress or danger by increasing heart rate, breathing, and sending more blood to muscles.
3. Thyroxin, made by the thyroid gland, controls the body’s metabolism; iodine is needed to make thyroxin, and its lack can cause goitre.
4. The pituitary gland makes growth hormone, which controls height and body growth; too little of it in childhood causes dwarfism.
5. Insulin, made by the pancreas, controls blood sugar levels; its shortage causes diabetes, and insulin injections help control it.