Neural Control and Coordination
NCERT Line-by-Line Breakdown for NEET 2026
Unit 5: Human PhysiologyCoordination is the process through which two or more organs interact and complement the functions of one another. The Neural System provides an organized network of point-to-point connections for quick coordination. In this chapter, we decode the Neuron, the Nerve Impulse, and the Human Brain.
1. Human Neural System
Divided into two main parts:
Includes the Brain and Spinal Cord. It is the site of information processing and control.
Comprises all nerves associated with CNS (Cranial & Spinal nerves).
- Afferent Fibers: Tissue → CNS.
- Efferent Fibers: CNS → Tissue.
Divisions of PNS
- Somatic Neural System: Relays impulses to Skeletal muscles (Voluntary).
- Autonomic Neural System (ANS): Relays impulses to Smooth muscles/Organs (Involuntary).
- Sympathetic: Fight or Flight.
- Parasympathetic: Rest and Digest.
2. Neuron: The Structural Unit
A neuron is a microscopic structure composed of three major parts:
[Image of neuron structure]| Part | Description |
|---|---|
| Cell Body | Contains cytoplasm, organelles, and Nissl’s Granules (RER & Ribosomes – Protein synthesis). |
| Dendrites | Short fibers branching repeatedly. Transmit impulse towards the cell body. |
| Axon | Long fiber. Transmits impulse away from the cell body. Distal end is branched and bulbous (Synaptic knob). |
- Myelinated: Enveloped by Schwann cells. Form Myelin sheath. Gaps are Nodes of Ranvier. (Found in Spinal/Cranial nerves).
- Non-myelinated: Enclosed by Schwann cell but NO myelin sheath. (Found in ANS/Somatic neural systems).
3. Nerve Impulse Generation
A. Resting Potential (Polarized State)
The membrane is Polarized (-70 mV).
- Axoplasm: High K+ and -ve proteins. Low Na+.
- Outside: High Na+. Low K+.
- Maintenance: Na-K Pump actively transports 3 Na+ OUT and 2 K+ IN.
B. Action Potential (Depolarization)
When a stimulus is applied:
- Na+ channels open → Rapid influx of Na+.
- Reversal of polarity (Inside becomes +ve). This is Action Potential.
C. Repolarization
Na+ channels close. K+ channels open → Efflux of K+ → Restores negative charge inside.
[Image of synaptic transmission diagram]• Electrical Synapse: Pre- and post-synaptic membranes in close proximity. Fast. Rare in humans.
• Chemical Synapse: Separated by Synaptic Cleft. Neurotransmitters (e.g., Acetylcholine) bind to receptors on post-synaptic membrane → Open ion channels.
4. Central Neural System (Brain)
Protected by Skull and Cranial Meninges: Dura mater (Outer), Arachnoid (Middle), Pia mater (Inner – contact with brain).
[Image of human brain sagittal section]A. Forebrain
- Cerebrum: Two hemispheres connected by Corpus Callosum. Cortex (Grey matter) deals with memory, communication.
- Thalamus: Major coordinating center for sensory and motor signaling.
- Hypothalamus: Controls Body Temperature, urge for eating/drinking. Contains Neurosecretory cells (Hormones).
- Limbic System: (Amygdala + Hippocampus + Hypothalamus) → Regulation of Sexual behavior and Emotional reactions (Excitement, fear, rage).
B. Midbrain
Located between Thalamus/Hypothalamus and Pons. Contains Cerebral Aqueduct. Dorsal portion has 4 lobes: Corpora Quadrigemina (Visual and Auditory reflexes).
C. Hindbrain
- Pons: Fiber tracts connecting brain regions. Pneumotaxic center.
- Cerebellum: Very convoluted surface. Maintains Balance and Posture.
- Medulla Oblongata: Connected to spinal cord. Controls Respiration, Cardiovascular reflexes, and Gastric secretions.
Brain Stem = Midbrain + Pons + Medulla.
📝 Rapid Fire MCQs
Q1. Which part of the brain controls body temperature?
- A) Cerebrum
- B) Cerebellum
- C) Hypothalamus
- D) Medulla
Click to check Answer
Answer: C) Hypothalamus.
Q2. The resting membrane potential is maintained mainly by:
- A) Voltage-gated Na+ channels
- B) Sodium-Potassium Pump
- C) Neurotransmitters
- D) Ca++ channels
Click to check Answer
Answer: B) Sodium-Potassium Pump (3 Na+ out, 2 K+ in).