Neural Control and Coordination - Detailed Notes

Reference textbooks: NCERT Biology Class 11 and Class 12

1. The Nervous System:

• Basic structure and organization:

  • Central Nervous System (CNS) - brain and spinal cord.
  • Peripheral Nervous System (PNS) - nerves connecting CNS to sensory organs and muscles.
  • Neuron: Basic structural and functional unit of the nervous system, responsible for transmitting information/signals.

• Types of neurons:

  • Sensory neurons: Transmit information from sense organs to the CNS.
  • Motor neurons: Transmit information from the CNS to muscles and glands.
  • Interneurons: Connect sensory neurons and motor neurons within the CNS.

• Synapse and neuron transmission:

  • Electrical transmission - Fast transmission of signals along the neuron’s axon in the form of action potentials (electrical impulses).
  • Chemical transmission - Slower transmission of signals across synapses (junctions between neurons) using neurotransmitters (chemical messengers).

2. Central Nervous System (CNS)

• Structure of the brain:

  • Cerebrum: Largest part of the brain involved in higher-level functions such as cognition, reasoning, emotions, and voluntary movements.
  • Cerebellum: Controls coordination, balance, and posture.
  • Brainstem: Connects the brain to the spinal cord and controls vital functions like breathing, heart rate, and sleep cycles.

• Functional regions of the brain:

  • Motor cortex: Controls voluntary body movements.
  • Sensory cortex: Processes sensory information from the body and external environment.
  • Association areas: Involved in complex brain functions like memory, learning, and language processing.

• Reflex arc and its components:

  • A rapid, automatic, and involuntary response to stimuli.
  • Components:
    • Receptor - Detects the stimulus.
    • Sensory neuron - Transmits the signal to the spinal cord.
    • Motor neuron - Transmits the signal back to the effector muscle.
    • Effector (muscle) - Responds to the signal.

• Role of the spinal cord in reflex actions:

  • Conducts sensory information from the body towards the brain and motor commands from the brain towards the body.
  • Plays a crucial role in reflex actions that occur at the spinal level.

3. Peripheral Nervous System (PNS):

• Structure and function of the somatic and autonomic nervous systems:
  • Somatic Nervous System (SNS): Controls voluntary skeletal muscle movements.
  • Autonomic Nervous System (ANS): Controls involuntary functions such as heart rate, digestion, and respiration.
• Sympathetic and parasympathetic divisions of the ANS:
  • Sympathetic System - Controls responses for the “Fight-or-flight” response.
  • Parasympathetic System - Controls “Rest-and-digest” responses.
  • Neurotransmitters involved: Acetylcholine (ACh) is the primary neurotransmitter for most of the PNS, including both SNS and ANS.

4. Sensory Mechanisms:

• General senses and specialized senses:
  • General senses: Somatic senses such as touch, pressure, pain, temperature.
  • Special senses: Vision, hearing, taste, and smell.
• Structure and function of the sense organs:
  • Eye - Detects light and transmits visual information.
  • Ear - Detects sound waves and helps in hearing and balance.
  • Nose - Detects odors.
  • Tongue - Detects taste sensations.
  • Skin - Detects sensations of touch, pressure, pain, and temperature.
• Sensory receptors and their role in perception:
  • Specialized cells that convert physical stimuli (light, sound, chemicals, etc.) into electrical signals.
  • These signals are then transmitted to the CNS for processing and perception.

5. Muscle Physiology:

• Structure and types of muscles:
  • Skeletal muscle - Voluntary muscles attached to the skeleton.
  • Smooth muscle - Involuntary muscles found in internal organs and blood vessels.
  • Cardiac muscle - Involuntary muscle found in the heart.
• Mechanism of muscle contraction:
  • Sliding filament theory explains the mechanism of muscle contraction.
  • Involves the interaction of actin and myosin filaments in response to nerve signals.
• Role of the neuromuscular junction in muscle contraction:
  • The neuromuscular junction is the site of communication between a motor neuron and a muscle fiber.
  • When an action potential reaches the neuromuscular junction, it triggers the release of neurotransmitters (e.g., ACh) that initiate muscle contraction.
• Muscle fatigue and relaxation:
  • Muscle fatigue: Decreased ability of a muscle to contract, often caused by prolonged use.
  • Muscle relaxation: Return of a muscle to its resting state after contraction.

6. Brain Organization:

• Functional areas of the cerebral cortex:
  • Motor cortex: Controls voluntary movement.
  • Sensory cortex: Processes sensory information.
  • Association areas: Involved in higher-level functions such as memory, language, and decision-making.
• Hemispheric specialization and lateralization of functions:
  • Left hemisphere: Dominant in language processing and logical thinking.
  • Right hemisphere: Dominant in spatial processing, visual perception, and emotions.

7. Hormonal Control:

• Role of hormones in neural coordination:
  • Hormones secreted by endocrine glands can affect neural function.
  • Examples: Adrenaline (epinephrine) from the adrenal medulla is involved in the fight-or-flight response.
• Pituitary gland and its importance:
  • Master gland of the endocrine system, controls other endocrine glands.
  • Secretes hormones that regulate growth, reproduction, and metabolism.
• Integration of nervous and hormonal signals:
  • The nervous and endocrine systems work together to maintain homeostasis.
  • Example: Adrenaline increases heart rate and blood pressure during the fight-or-flight response.

8. Autonomic Nervous System:

• Regulation of heart rate, respiration, and digestion:
  • ANS controls heart rate, breathing, and digestive movements.
  • Sympathetic division increases these functions during times of stress, while the parasympathetic division decreases them during times of rest and relaxation.
• Fight-or-flight response and its hormonal basis:
  • Sudden mobilization of the body’s resources in response to stress or danger.
  • Controlled by the sympathetic nervous system and hormones like adrenaline (epinephrine).

9. Neurodegenerative Disorders:

• Basic concepts of neurodegenerative disorders:
  • A group of neurological conditions characterized by progressive degeneration and death of neurons.
  • Examples: Alzheimer’s disease, Parkinson’s disease, Huntington’s disease.
• Role of neural control and coordination in these disorders:
  • Affect motor control, coordination, cognitive functions, and behavior due to the loss of specific types of neurons.