Topics to be learn

  • Introduction
  • System for control and coordination in animals
  • Nervous System → Receptors
  • Neuron
  • Reflex Action
  • Human Nervous System
  • Human Brain
  • Coordination in Plants
  • Plant Hormones
  • Hormones in Animals
  • Importance of iodine
  • Diabetes

 Introduction

  • All living organisms respond to changes in their environment.
  • These changes are called stimuli (e.g., light, heat, cold, sound, smell, touch).
  • Both plants and animals respond to stimuli but in different ways.

Systems for Control and Coordination in Animals

  • Control and coordination in animals are managed by two main systems:
    • Nervous system & Endocrine system

Nervous System

  • Control and coordination are provided by nervous and muscular tissues.
  • Nervous tissue is made up of neurons (nerve cells) that conduct information via electrical impulses.


Receptors

  • Receptors are specialized tips of nerve cells that detect information from the environment. They are located in our sense organs.
  • Types of receptors and their functions:
  • Ear: Acts as phonoreceptors (receives sound). Helps in hearing and maintaining balance.
  • Eyes: Acts as photoreceptors (receives light). Helps in seeing.
  • Skin: Acts as thermoreceptors (feels temperature). Helps in feeling heat, cold, and touch.
  • Nose: Acts as olfactory receptors (sense of smell). Helps in detecting smells.
  • Tongue: Acts as gustatory receptors (sense of taste). Helps in detecting tastes.

Neuron

Neuron: The structural and functional unit of the nervous system.

Functioning of a Neuron

  • Information acquisition:
    • Receptors detect information, creating a chemical reaction that generates an electrical impulse.
  • Impulse travel:
    • The impulse travels from the dendrite to the cell body, then to the axon.
  • Chemical release:
    • Electrical impulses cause chemicals to be released at the end of the axon.
    • These chemicals cross the synapse (gap) to the next neuron's dendrite.
    • The impulse continues to muscle cells or glands.


Parts of a Neuron

  • Dendrite: Acquires information.
  • Cell body: Transmits the electrical impulse.
  • Axon: Long fiber transmitting the impulse from the cell body to the next neuron's dendrite.
  • Synapse: Gap where the electrical signal is converted into a chemical signal for transmission.

 Reflex Action
  • Reflex action: Quick, sudden, and immediate response to a stimulus.
    • Example: Knee jerk, withdrawal of hand on touching hot object.

Components of Reflex Action

  • Stimulus: Detectable change in the environment that an organism reacts to.
  • Reflex arc: Pathway through which nerve impulses pass during a reflex action.
  • Response: The final reaction after the reflex action.


Types of Responses

  1. Voluntary: Controlled by the forebrain.
    • Example: Talking, writing.
  2. Involuntary: Controlled by the midbrain and hindbrain.
    • Example: Heartbeat, vomiting, respiration.
  3. Reflex action: Controlled by the spinal cord.
    • Example: Withdrawal of hand on touching a hot object.

Need for Reflex Actions

  • Reflex actions allow the body to act quickly in certain situations (e.g., touching a hot object or pinching).
  • Responses are generated by the spinal cord instead of the brain, reducing reaction time and preventing injury.

Human Nervous System

  • Human nervous system consists of two parts:
    • Central nervous system (CNS)
    • Peripheral nervous system (PNS)

Central Nervous System (CNS)

  • Consists of: Brain, Spinal Cord.

Peripheral Nervous System (PNS)

  • Consists of: Cranial nerves (arise from the brain), Spinal nerves (arise from the spinal cord).

 

Human Brain

  • Brain: Main coordinating center of the body.
  • Three major parts:
    • Fore-brain
    • Mid-brain
    • Hind-brain

 
Fore-brain

  • Most complex part of the brain, consists of the cerebrum.
  • Functions:
    • Thinking part of the brain.
    • Controls voluntary actions.
    • Stores information (memory).
    • Receives and integrates sensory impulses.
    • Associated with hunger.

Mid-brain

  • Controls involuntary actions such as:
    • Change in pupil size.
    • Reflex movements of head, neck, and trunk.

Hind-brain

  • Three parts:
    • Cerebellum: Controls posture and balance, precision of voluntary actions (e.g., picking up a pen).
    • Medulla: Controls involuntary actions (e.g., blood pressure, salivation, vomiting).
    • Pons: Involved in involuntary actions, regulation of respiration.

Protection of Brain and Spinal Cord

  • Brain:
    • Protected by a fluid-filled balloon (acts as a shock absorber).
    • Enclosed in the cranium (skull or brain box).
  • Spinal Cord: Enclosed in the vertebral column.
Coordination between Nervous and Muscular Tissue
  • For voluntary actions, the brain sends messages to muscles.
  • Communication between the central nervous system (CNS) and other body parts is facilitated by the peripheral nervous system (PNS).
    • Cranial nerves arise from the brain.
    • Spinal nerves arise from the spinal cord.
  • The brain integrates different inputs and outputs, allowing us to think and act.

Limitations of Electric Communication/Nervous System

  1. Limited Reach: Electric impulses only reach cells connected by nervous tissue.
  2. Transmission Delay: After sending an impulse, cells need time to reset before sending another.
  3. Plant Limitation: Plants do not have a nervous system.

Chemical Communication

  • Chemical communication helps overcome the limitations of electric communication.

Coordination in Plants

  • Plants exhibit three types of movements:
    1. Independent of growth
    2. Dependent on growth

Independent of Growth

  • Immediate response to stimuli.
  • Plants use electrical-chemical means to convey information.
  • Movement occurs by cells changing shape, swelling or shrinking due to water changes.
    • Example: Drooping of leaves of the 'Touch-me-not' plant when touched.

Dependent on Growth

  • Tropic movements: Directional movements in response to a stimulus.
    • Tendrils: Part away from an object grows rapidly, causing the tendril to circle the object.
    • Phototropism: Movement towards light.
    • Geotropism: Movement towards or away from gravity.
    • Chemotropism: Growth of pollen tube towards ovule.
    • Hydrotropism: Movement towards water.

Plant Hormones

  • Plant hormones are chemical compounds that coordinate growth, development, and responses to the environment.
  • Main plant hormones:
    • Auxin: Synthesized at the shoot tip. Helps cells grow longer, involved in phototropism (response to light).
    • Gibberellin: Promotes the growth of the stem.
    • Cytokinins: Promotes cell division, present in higher concentrations in fruits and seeds.
    • Abscisic Acid: Inhibits growth, causes wilting of leaves, known as the stress hormone.

Hormones in Animals

  • Hormones are chemical substances that coordinate activities and growth in living organisms.
  • Endocrine glands secrete hormones into the blood.

Endocrine Glands and Hormones



Importance of Iodine

  • Iodized salt is necessary because iodine is an essential part of thyroxine.
  • Thyroxine regulates metabolism of carbohydrates, fats, and proteins.
  • Deficiency of iodine causes goiter (swollen neck).

Diabetes

  • Diabetes: A disease where blood sugar level increases.
  • Cause: Deficiency of insulin hormone secreted by the pancreas.
  • Treatment: Injections of insulin hormone.

Feedback Mechanism

  • Ensures hormones are secreted in precise quantities and at the right time to prevent harmful effects from excess or deficiency.

Example of Feedback Mechanism

  • Control of blood sugar level:
    • High blood sugar → Pancreas releases insulin → Lowers blood sugar.
    • Low blood sugar → Pancreas releases less insulin → Raises blood sugar.