Neural Control and Coordination: Class 11 Biology Notes

Neural Control and Coordination: Class 11 Biology Notes

Introduction

Neural control and coordination allow the body to respond rapidly to internal and external stimuli. The nervous system, consisting of the brain, spinal cord, and nerves, coordinates body functions and reflexes. This post covers the structure of neurons, types of nervous systems, reflex arcs, and the brain’s functional regions.

1. Nervous System Overview

The nervous system regulates and coordinates body activities. It is divided into:

  • Central Nervous System (CNS): Brain and spinal cord. Controls sensory input, processing, and motor output.
  • Peripheral Nervous System (PNS): All nerves outside CNS. Connects CNS to body organs.
  • Autonomic Nervous System (ANS): Controls involuntary activities. Divided into:
    • Sympathetic: “Fight or flight” response.
    • Parasympathetic: “Rest and digest” functions.

2. Neuron: The Functional Unit of Nervous System

  • Structure of a Neuron:
    • Cell body (Soma): Contains nucleus and organelles.
    • Dendrites: Short, branched fibers that receive signals.
    • Axon: Long fiber transmitting impulses away from cell body.
    • Myelin Sheath: Fatty layer around axon for faster impulse conduction.
    • Axon Terminals: Endings that release neurotransmitters.
  • Types of Neurons:
    • Sensory (Afferent): Carry impulses from receptors to CNS.
    • Motor (Efferent): Carry impulses from CNS to effectors.
    • Interneurons: Connect sensory and motor neurons within CNS.

3. Reflex Action

  • Reflex is an automatic, rapid, involuntary response to a stimulus.
  • Reflex Arc: Pathway of nerve impulse in a reflex. Steps:
    1. Stimulus activates receptor.
    2. Impulse travels through sensory neuron.
    3. Interneuron in spinal cord processes impulse.
    4. Impulse travels via motor neuron.
    5. Effector (muscle or gland) responds.
  • Example: Knee-jerk reflex.

4. Brain and Spinal Cord

a) Brain

  • Forebrain:
    • Cerebrum: Controls voluntary actions, intelligence, memory, senses.
    • Thalamus: Relay center for sensory information.
    • Hypothalamus: Controls autonomic functions, temperature, hunger, thirst.
  • Midbrain: Controls reflexes and vision/hearing coordination.
  • Hindbrain:
    • Cerebellum: Coordinates balance, posture, and movement.
    • Medulla Oblongata: Regulates heartbeat, respiration, and digestion.

b) Spinal Cord

  • Conveys messages between brain and body.
  • Coordinates simple reflexes.

5. Mechanism of Nerve Impulse Transmission

  • Resting Potential: Neuron at rest (-70 mV).
  • Action Potential: Rapid reversal of membrane potential when stimulated.
  • Synapse: Junction between two neurons; neurotransmitters transmit the impulse across the synaptic cleft.

6. Disorders of Nervous System

  • Parkinson’s Disease: Degeneration of dopamine-producing neurons.
  • Alzheimer’s Disease: Progressive memory loss and cognitive decline.
  • Epilepsy: Abnormal electrical activity in the brain causing seizures.
  • Poliomyelitis: Viral infection affecting motor neurons, leading to paralysis.

MCQs for Exam Preparation

  1. The structural and functional unit of the nervous system is:
    • A) Axon
    • B) Neuron
    • C) Dendrite
    • D) Synapse
    • Answer: B) Neuron
  2. Which part of the neuron receives impulses from other neurons?
    • A) Axon
    • B) Dendrites
    • C) Soma
    • D) Myelin sheath
    • Answer: B) Dendrites
  3. Knee-jerk reflex is an example of:
    • A) Voluntary action
    • B) Reflex action
    • C) Conditioned response
    • D) Sensory adaptation
    • Answer: B) Reflex action
  4. Which part of the brain controls balance and coordination?
    • A) Cerebrum
    • B) Cerebellum
    • C) Medulla
    • D) Hypothalamus
    • Answer: B) Cerebellum
  5. Which division of the autonomic nervous system is active during “fight or flight”?
    • A) Parasympathetic
    • B) Sympathetic
    • C) Somatic
    • D) Central
    • Answer: B) Sympathetic
  6. Neurotransmitters are released at:
    • A) Dendrites
    • B) Axon terminals
    • C) Cell body
    • D) Nucleus
    • Answer: B) Axon terminals
  7. Resting potential of a neuron is approximately:
    • A) +70 mV
    • B) -70 mV
    • C) 0 mV
    • D) -50 mV
    • Answer: B) -70 mV
  8. Which part of brain controls autonomic functions like heartbeat and respiration?
    • A) Cerebellum
    • B) Medulla oblongata
    • C) Cerebrum
    • D) Thalamus
    • Answer: B) Medulla oblongata
  9. Interneurons connect:
    • A) Sensory neurons to effectors
    • B) Motor neurons to effectors
    • C) Sensory neurons to motor neurons
    • D) Brain to muscles
    • Answer: C) Sensory neurons to motor neurons
  10. Which disease is characterized by progressive memory loss and cognitive decline?
    • A) Parkinson’s
    • B) Alzheimer’s
    • C) Epilepsy
    • D) Poliomyelitis
    • Answer: B) Alzheimer’s