Schooling · Class 11 · Biology · Neural Control and Coordination · Chapter on a page
CBSE Class 11 · Biology · NCERT Biology
Neural Control and Coordination: chapter on a page
A cut of Shishya's notes for this chapter: the first paragraph of the introduction and the key ideas, formulas and facts, common mistakes and quick revision lists, word for word. Nothing is added or reworded; the worked examples are left out (they are on the chapter page).
About the notes: Written by Shishya's AI on 27 Sept 2026 from the chapter's title and class level, in Shishya's own words — not a copy or summary of the textbook. Read the official chapter for the book's own text, activities and exercises.
This note's current text has no applied fact-check on record.
Mind map
Drawn from the same notes by a fixed rule (no AI): each label is the item's own words — its bold term, its label before a colon, a short formula as written, or its first words.
The mind map as a list
- Key ideas
- Neurons are the structural and…
- The resting membrane potential of a…
- An action potential is an…
- Synapses are junctions between neurons
- The central nervous system (CNS)…
- The peripheral nervous system (PNS)…
- Reflex arcs provide rapid, automatic…
- Formulas and facts
- Resting potential
- Action potential sequence
- Saltatory conduction
- Neurotransmitters
- 12 pairs of cranial nerves
- Photoreceptors
- Accommodation
- Worked examples
- Understanding the action potential
- Tracing a reflex arc
- Image formation in the eye
- Watch out for
- Thinking dendrites transmit impulses…
- Confusing depolarisation with…
- Believing reflexes are controlled by…
- Mixing up rods and cones
- Assuming the sympathetic and…
What this chapter is about
The human body performs countless activities simultaneously — walking, breathing, digesting food, maintaining balance, and responding to sudden dangers. All these actions require precise coordination, which is achieved through the nervous system. This chapter introduces students to how nerve cells generate and transmit electrical signals, how the brain and spinal cord process information, and how our sense organs detect changes in the environment.
Key ideas
- Neurons are the structural and functional units of the nervous system. Each neuron has a cell body (containing the nucleus), dendrites (receiving signals), and an axon (transmitting signals away from the cell body).
- The resting membrane potential of a neuron is about −70 mV. This is maintained by the sodium-potassium pump, which moves 3 Na⁺ ions out and 2 K⁺ ions into the cell, using ATP.
- An action potential is an all-or-none electrical signal. When a stimulus reaches threshold, voltage-gated Na⁺ channels open, causing depolarisation; then K⁺ channels open, leading to repolarisation.
- Synapses are junctions between neurons. At chemical synapses, neurotransmitters (such as acetylcholine) are released from synaptic vesicles, cross the synaptic cleft, and bind to receptors on the postsynaptic membrane.
- The central nervous system (CNS) consists of the brain and spinal cord. The brain has three main regions: forebrain (cerebrum, thalamus, hypothalamus), midbrain, and hindbrain (cerebellum, pons, medulla oblongata).
- The peripheral nervous system (PNS) includes cranial and spinal nerves. The autonomic nervous system, part of PNS, has sympathetic (fight-or-flight) and parasympathetic (rest-and-digest) divisions.
- Reflex arcs provide rapid, automatic responses. A simple reflex arc involves a receptor, sensory neuron, integration centre in the spinal cord, motor neuron, and effector organ.
- The eye and ear are specialised sense organs. The retina contains photoreceptors (rods and cones), while the cochlea in the inner ear contains hair cells that detect sound vibrations.
Formulas and facts to remember
- Resting potential: approximately −70 mV; inside of neuron is negative relative to outside.
- Action potential sequence: resting state → depolarisation (Na⁺ influx) → repolarisation (K⁺ efflux) → hyperpolarisation → return to resting state.
- Saltatory conduction: in myelinated neurons, impulses jump between nodes of Ranvier, increasing conduction speed up to 100 m/s.
- Neurotransmitters: acetylcholine (at neuromuscular junctions), dopamine, serotonin, norepinephrine, GABA.
- 12 pairs of cranial nerves arise from the brain; 31 pairs of spinal nerves arise from the spinal cord.
- Photoreceptors: rods (dim light, no colour) and cones (bright light, colour vision — red, green, blue types).
- Accommodation: the ability of the eye to change lens curvature to focus on near or distant objects.
- Organ of Corti: located in the cochlea; contains hair cells that convert sound vibrations into nerve impulses.
Common mistakes
- Thinking dendrites transmit impulses away from the cell body → dendrites receive signals; axons transmit impulses away.
- Confusing depolarisation with repolarisation → depolarisation is Na⁺ entry making inside positive; repolarisation is K⁺ exit restoring negative inside.
- Believing reflexes are controlled by the brain → simple reflexes are coordinated by the spinal cord; the brain is informed afterward.
- Mixing up rods and cones → rods work in dim light and give black-and-white vision; cones need bright light and detect colours.
- Assuming the sympathetic and parasympathetic systems always oppose each other exactly → they often have complementary but not simply opposite effects on different organs.
Quick revision
- Neurons have dendrites (receive), cell body (integrate), and axon (transmit).
- Resting potential is −70 mV; action potential involves Na⁺ influx (depolarisation) then K⁺ efflux (repolarisation).
- Synapses use neurotransmitters to pass signals between neurons.
- CNS = brain + spinal cord; PNS = cranial nerves (12 pairs) + spinal nerves (31 pairs).
- Reflex arcs enable rapid, involuntary responses without brain involvement.
- Eye: lens accommodation for focusing; retina has rods and cones. Ear: cochlea converts sound to nerve impulses.