class 10 Science chapter 6 control and coordination short notes for quick revision ncert

Control and Coordination: Organism respond to stimuli using specialised systems. In animals, the nervous system detects stimuli, transmits signals via neurons, and triggers actions. Reflex arcs enable quick automatic responses for safety and efficiency.

Movements and Life

Movements are a response to environmental changes and signify life.
Two types of movements:
- Growth-related movements (e.g., seedling pushing through soil).
- Non-growth movements (e.g., animals running, children playing).

Control and Coordination

Organisms respond to environmental changes with precise movements.
Requires control and coordination through specialised systems in multicellular organisms.

Animals – Nervous System

Nervous and muscular tissue enable control and coordination.
Environmental stimuli are detected by receptors in sense organs (e.g. gustatory for taste, olfactory for smell).

Transmission of signals:
- Stimulus at the dendritic tip – chemical reaction – electrical impulse.
- Impulse travels via dendrite – cell body – axon
- At synapse, electrical impulse triggers chemical release, continuing signal transmission.
Neurons form a network for electrical impulse conduction.

Reflex Actions

Definition: Sudden, involuntary action in response to a stimulus (e.g., pulling hand back from flame).
Reflex Arc:
- Direct connection between input and output nerves via the spinal cord.
- Allows quick responses without involving the brain immediately.
Evolution:
- Reflex arcs evolved for efficiency and exist even in organism with advanced neuron networks.

Importance of Reflex Actions

Quick responses to urgent situations.
Prevents harm by bypassing the slower thinking process in the brain.

Human Brian

Functions of the Spinal Cord: Reflex actions and transmission of information to the brain.
Central Nervous System (CNS): Brain and spinal cord integrate and process information.
Voluntary Actions: Decided by the brain (e.g., writing, talking).
Peripheral Nervous System (PNS): Includes cranial and spinal nerves; links CNS to the body.
Brain Regions:
- Fore-brain: Thinking, sensory input, voluntary muscles.
- Mid-brain Relay centre for sensory and motor signals.
- Hind-brain:
  - Medula: Involuntary actions (heartbeat, blood pressure).
  - Cerebellum: Posture, balance, precision of movements.

Nervous Tissue and Action

Neurons: Transmit electrical impulses for fast communication.
Muscle Movement:
- Proteins in muscle cells shorten in response to neural signals.
- Voluntary muscles (controlled) vs. involuntary muscles (uncontrolled).

Coordination in Plants

No Nervous System: Use chemical and electrical signals.
Types of Movement
- Independent of Growth: Sensitive plant folding via water movement in cells.
- Dependent on Growth: Directional growth (e.g., roots, shoots).
Tropisms:
- Phototropism: Shoots grow towards light.
- Geotropism: Roots grow downward.
- Hydrotropism: Growth towards water.
- Chemotropism: Growth towards chemicals (e.g., pollen tube)
Plant Hormones
- Auxin: Promotes cell elongation.
- Gibberellines: Stem growth
- Cytokinins: Cell division.
- Abscisic Acid: Growth inhibition, leaf wilting.

Hormones in Animals

Hormonal Control: Chemical signals reach all body parts.
Adrenaline:
- Prepares body for action (fight/flight)
- Increases heartbeat, blood flow to muscles, breathing rate.
Thyroxin (Thyroid Gland): Regulates metabolisms requires iodine (deficiency causes goitre).
Growth Hormone (Pituitary): Control growth; deficiency causes dwarfism.
Puberty Hormones:
- Testosterone (Males): Male reproductive changes.
- Oestrogen (Females): Female reproductive changes.
Insulin (Pancreas): Regulates blood sugar; deficiency causes diabetes (treated with insulin injections)