Bihar Board - Class 11 biology - Chapter 21: Neural Control and Coordination Handwritten Notes

Neural control and coordination enable the human body to respond to external and internal stimuli. This chapter explores the structure and functioning of the nervous system, including neurons, the brain, spinal cord, and the mechanism of signal transmission.

Key Points

1. Nervous System Overview

   • Central Nervous System (CNS): Comprises the brain and spinal cord, responsible for processing and integrating information.
   • Peripheral Nervous System (PNS): Includes cranial and spinal nerves that connect the CNS to the rest of the body.
   • Autonomic Nervous System (ANS): Regulates involuntary activities and is divided into sympathetic and parasympathetic systems.

2. Structure of a Neuron

   • Cell Body (Soma): Contains the nucleus and cytoplasm.
   • Dendrites: Short extensions that receive signals.
   • Axon: Long extension that transmits signals to other neurons or muscles.
   • Myelin Sheath: Insulating layer around the axon, speeding up signal transmission.

3. Nerve Impulse Transmission

   • Resting Potential: The polarized state of a neuron when not transmitting signals.
   • Action Potential: The depolarization and repolarization of the neuronal membrane during impulse transmission.
   • Synaptic Transmission: Transfer of impulses between neurons through chemical messengers called neurotransmitters.

4. Human Brain

   • Forebrain: Includes the cerebrum (responsible for thinking, memory, and emotions) and diencephalon.
   • Midbrain: Connects the forebrain and hindbrain and controls reflex movements.
   • Hindbrain: Includes the cerebellum (coordinates movement and balance), pons, and medulla oblongata.
   • Protective Layers: The brain is protected by the skull, meninges, and cerebrospinal fluid (CSF).

5. Spinal Cord

   • A cylindrical structure extending from the brainstem, enclosed within the vertebral column.
   • Responsible for transmitting nerve signals between the brain and the body and coordinating reflex actions.

6. Sensory Organs

   • Eyes: Responsible for vision, involving the cornea, lens, retina, and optic nerve.
   • Ears: Responsible for hearing and balance, involving the auditory canal, eardrum, cochlea, and vestibular apparatus.
   • Other Sensory Organs: Include receptors for smell (olfactory), taste (gustatory), and touch.

7. Reflex Action

   • Involuntary and instantaneous response to a stimulus, such as the knee-jerk reflex.
   • Reflex Arc: The neural pathway involved in reflex action, consisting of sensory and motor neurons and the spinal cord.

8. Disorders of the Nervous System

   • Epilepsy: Recurrent seizures caused by abnormal electrical activity in the brain.
   • Alzheimer’s Disease: Progressive memory loss due to degeneration of neurons.
   • Parkinson’s Disease: Motor dysfunction caused by a deficiency of dopamine.
   • Multiple Sclerosis: Autoimmune disorder damaging the myelin sheath of neurons.

Conclusion

Neural control and coordination are essential for regulating body functions and responding to stimuli. The nervous system, with its complex network of neurons and sensory organs, ensures seamless communication and control. Understanding the mechanisms of the nervous system aids in diagnosing and managing neurological disorders effectively.

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