Coordination in the Body

  • Coordination: Interaction between organs to ensure they work together efficiently.
    • Example: During exercise, muscles need more energy and oxygen, so respiration, heartbeat, and blood flow increase. After exercise, the body gradually returns to normal.
  • Systems Involved:
    • Neural System: Provides quick point-to-point communication using nerves.
    • Endocrine System: Uses hormones for chemical coordination.

Neural System

  • Made of neurons, which detect, receive, and transmit stimuli.
  • Simple in lower animals (e.g., Hydra with a basic neuron network) but advanced in vertebrates (e.g., brain and ganglia in insects, complex neural systems in humans).

Human Neural System

  1. Parts:
    • Central Neural System (CNS): Brain and spinal cord; processes information and controls actions.
    • Peripheral Neural System (PNS): Nerves outside the CNS; connects CNS to the body.
  2. Types of PNS Fibers:
    • Afferent Fibers: Carry impulses to CNS from organs.
    • Efferent Fibers: Carry impulses from CNS to organs.
  3. Divisions of PNS:
    • Somatic Neural System: Sends impulses to skeletal muscles (voluntary).
    • Autonomic Neural System: Sends impulses to involuntary organs and smooth muscles.
      • Sympathetic System: Activates fight or flight responses.
      • Parasympathetic System: Promotes rest and recovery.
  4. Visceral Nervous System: Connects CNS with internal organs (viscera).

Neuron: The Basic Unit

  1. Structure:
    • Cell Body: Contains cytoplasm, organelles, and Nissl’s granules.
    • Dendrites: Short, branched fibers that carry impulses to the cell body.
    • Axon: Long fiber carrying impulses away from the cell body, ending in synaptic knobs with neurotransmitters.
  2. Types of Neurons:
    • Multipolar: One axon, many dendrites (e.g., cerebral cortex).
    • Bipolar: One axon, one dendrite (e.g., retina).
    • Unipolar: One axon, no dendrites (embryonic stage).
  3. Axons:
    • Myelinated: Covered by Schwann cells forming a myelin sheath with gaps (nodes of Ranvier); found in spinal and cranial nerves.
    • Non-Myelinated: Covered by Schwann cells without myelin sheath; found in autonomic and somatic systems.

Generation and Conduction of Nerve Impulses

  1. Resting State:
    • The neuron membrane is polarized (positive outside, negative inside).
    • Ionic Gradient:
      • More K⁺ and proteins inside the axon.
      • More Na⁺ outside.
    • Maintained by the sodium-potassium pump (3 Na⁺ out, 2 K⁺ in).
  2. Action Potential:
    • A stimulus makes the membrane permeable to Na⁺, causing Na⁺ influx and reversing polarity (depolarization).
    • The depolarized region forms the action potential (nerve impulse).
  3. Impulse Conduction:
    • The action potential travels along the axon as currents flow between depolarized and polarized regions.
    • The membrane quickly restores the resting state by pumping out K⁺.
  4. Repolarization:
    • After depolarization, K⁺ diffuses out, restoring the resting potential, making the neuron ready for another impulse.

Transmission of Impulses

  1. What is a Synapse?
    • A synapse is a junction between two neurons:
      • Pre-synaptic neuron: Sends the impulse.
      • Post-synaptic neuron: Receives the impulse.
    • Separated by a synaptic cleft in chemical synapses.
  2. Types of Synapses:
    • Electrical Synapses:
      • Neurons are very close.
      • Impulse transmission is fast and similar to conduction within a neuron.
      • Rare in humans.
    • Chemical Synapses:
      • Neurons are separated by a fluid-filled synaptic cleft.
      • Process:
        • Impulse arrives → Neurotransmitter vesicles move to the membrane.
        • Neurotransmitters are released into the cleft.
        • Bind to receptors on post-synaptic membrane → Open ion channels.
        • New potential generated (excitatory or inhibitory).

Central Neural System (CNS)

  1. Functions of the Brain:
    • Controls voluntary movements, balance, involuntary organ functions (lungs, heart), body temperature, hunger, thirst, and biological rhythms.
    • Processes sensory inputs (vision, hearing) and emotions, thoughts, memory, and speech.
  2. Protection of the Brain:
    • Enclosed in the skull.
    • Covered by cranial meninges:
      • Dura mater: Outer layer.
      • Arachnoid: Middle thin layer.
      • Pia mater: Inner layer in contact with the brain.
  3. Parts of the Brain:
    • Forebrain:
      • Cerebrum:
        • Largest part. Divided into left and right hemispheres by the corpus callosum.
        • Outer layer (grey matter): Contains neuron cell bodies; responsible for sensory, motor, and association functions like memory and communication.
        • Inner layer (white matter): Contains myelinated nerve fibers.
      • Thalamus: Major sensory and motor relay center.
      • Hypothalamus:
        • Regulates body temperature, hunger, thirst, emotions, and sexual behavior.
        • Produces hypothalamic hormones.
        • Forms part of the limbic system for emotional responses and motivation.
    • Midbrain:
      • Located between the forebrain and hindbrain.
      • Contains corpora quadrigemina for integrating visual, auditory, and tactile information.
    • Hindbrain:
      • Pons: Connects different brain regions.
      • Cerebellum: Coordinates balance and movement using information from the ear and other sensory systems.
      • Medulla Oblongata:
        • Connects brain to spinal cord.
        • Controls respiration, heart rate, and digestion reflexes.

Extra Insights for Competitive Exams

  1. Neurotransmitters:
    • Common examples:
      • Excitatory: Acetylcholine, glutamate.
      • Inhibitory: GABA (gamma-aminobutyric acid).
  2. Differences Between Electrical and Chemical Synapses:
    • Electrical: Faster, direct ion flow, bidirectional.
    • Chemical: Slower, neurotransmitter-dependent, unidirectional.
  3. Brain Functional Areas:
    • Motor Areas: Control movement.
    • Sensory Areas: Process sensory input (e.g., touch, sound).
    • Association Areas: Complex tasks like reasoning, memory, and communication.
  4. Clinical Relevance:
    • Disorders:
      • Parkinson’s: Dopamine deficiency in the brain.
      • Epilepsy: Uncontrolled neural firing.
    • Tests: EEG (Electroencephalogram) measures electrical brain activity.
  5. Memory Types:
    • Short-term: Limited capacity, temporary.
    • Long-term: Permanent storage.

By focusing on these points, one can answer both theoretical and practical questions in exams effectively.

These all are the notes of chapter 18. And important questions are below HERE. *#THANKS FOR VISITING, VISIT AGAIN#* 😊

1. What is coordination in the body?

Answer: Coordination is the interaction between different organs and systems to ensure they work together effectively. For example, during exercise, muscles need more energy, so systems like respiration, heartbeat, and blood flow increase to meet these needs.

2. Which systems are involved in coordination?

Answer: Two main systems are involved:

  • Neural System: Provides quick communication using nerves.
  • Endocrine System: Uses hormones to coordinate body functions chemically.

3. What is the role of the neural system in coordination?

Answer: The neural system provides fast communication by sending electrical signals through nerves. It coordinates actions by transmitting impulses between the brain, spinal cord, and various body parts.

4. How does the endocrine system contribute to coordination?

Answer: The endocrine system uses hormones, which are chemical messengers, to communicate between different parts of the body. Hormones regulate processes like metabolism, growth, and mood over a longer period.

5. What are neurons and how do they function?

Answer: Neurons are the basic units of the neural system. They detect, receive, and transmit electrical impulses. They are specialized to send messages throughout the body to coordinate functions.

6. How is the neural system different in lower animals and humans?

Answer: In lower animals (like Hydra), the neural system is simple, with a basic network of neurons. In humans and other vertebrates, the neural system is more advanced, with a complex brain and spinal cord.

7. What are the two main parts of the human neural system?

Answer:

  • Central Neural System (CNS): Includes the brain and spinal cord, which process information and control actions.
  • Peripheral Neural System (PNS): Includes nerves outside the CNS that connect it to the rest of the body.

8. What are afferent and efferent fibers in the PNS?

Answer:

  • Afferent Fibers: Carry impulses from organs to the CNS.
  • Efferent Fibers: Carry impulses from the CNS to organs.

9. What are the divisions of the PNS?

Answer:

  • Somatic Neural System: Controls voluntary muscles.
  • Autonomic Neural System: Controls involuntary organs and smooth muscles.
    • Sympathetic System: Prepares the body for stress (fight or flight).
    • Parasympathetic System: Promotes rest and recovery.
  • Visceral Nervous System: Connects the CNS to internal organs.

10. What is the structure of a neuron?

Answer: A neuron consists of:

  • Cell Body: Contains the cell’s organelles.
  • Dendrites: Branch-like structures that receive impulses.
  • Axon: A long fiber that carries impulses away from the cell body.

11. What are myelinated and non-myelinated axons?

Answer:

  • Myelinated Axons: Covered by myelin (a fatty substance), which speeds up nerve impulses. Found in spinal and cranial nerves.
  • Non-myelinated Axons: Do not have myelin and are slower. Found in autonomic systems.

12. How is a nerve impulse generated and conducted?

Answer: A nerve impulse begins when a stimulus makes the neuron membrane permeable to sodium ions (Na⁺). This causes depolarization and creates an action potential. The impulse travels along the axon, and the neuron restores its resting state by pumping potassium (K⁺) out, ready for another impulse.

13. What is a synapse?

Answer: A synapse is the junction between two neurons. The impulse from the pre-synaptic neuron is transmitted to the post-synaptic neuron through the release of neurotransmitters into the synaptic cleft.

14. What are the types of synapses?

Answer:

  • Electrical Synapses: Neurons are very close, and impulses travel quickly. These are rare in humans.
  • Chemical Synapses: Neurons are separated by a synaptic cleft, and neurotransmitters are used to transmit the impulse.

15. What is the function of the brain in the CNS?

Answer: The brain controls voluntary movements, balance, involuntary functions like heart rate and breathing, and processes sensory inputs. It also regulates emotions, thoughts, memory, and speech.

16. How is the brain protected?

Answer: The brain is protected by the skull and covered by three layers of meninges:

  • Dura mater: Outer, tough layer.
  • Arachnoid: Thin middle layer.
  • Pia mater: Inner layer, in contact with the brain.

17. What are the major parts of the brain?

Answer:

  • Forebrain: Includes the cerebrum (responsible for sensory, motor, and association functions), thalamus (sensory relay), and hypothalamus (regulates temperature, hunger, thirst, and emotions).
  • Midbrain: Involved in integrating visual, auditory, and tactile information.
  • Hindbrain: Includes the pons (connects brain regions), cerebellum (coordinates balance), and medulla oblongata (controls basic functions like breathing and heart rate).

18. What are neurotransmitters and their functions?

Answer: Neurotransmitters are chemicals that transmit impulses across synapses.

  • Excitatory Neurotransmitters: Like acetylcholine and glutamate, which activate neurons.
  • Inhibitory Neurotransmitters: Like GABA, which prevent neurons from firing.

19. What is the difference between electrical and chemical synapses?

Answer:

  • Electrical Synapses: Faster, direct ion flow, bidirectional transmission.
  • Chemical Synapses: Slower, use neurotransmitters, unidirectional transmission.

20. What are the functional areas of the brain?

Answer:

  • Motor Areas: Control movement.
  • Sensory Areas: Process sensory inputs (like touch or sound).
  • Association Areas: Involved in complex tasks like reasoning, memory, and communication.

Additional Knowledge:

  • Neurotransmitters play a crucial role in the communication between neurons. Deficiency in neurotransmitters can lead to disorders such as Parkinson’s disease (lack of dopamine).
  • Parkinson’s Disease: Caused by the deficiency of dopamine, leading to tremors and difficulty in movement.
  • Epilepsy: Caused by uncontrolled neural firing, leading to seizures.
  • EEG (Electroencephalogram): A test used to measure electrical activity in the brain, often used to diagnose conditions like epilepsy.
  • Memory Types:
    • Short-term memory has a limited capacity and is temporary.
    • Long-term memory stores information permanently, allowing us to retain knowledge over time.