Nervous System Table
Explore the **Brain**, **Spinal Cord**, and **Nerves**. The Body's Control Center.
Central Nervous System (CNS)
Cerebrum
ForebrainLargest part of the brain. Responsible for intelligence, memory, personality, voluntary muscle movements, and interpreting senses.
Cerebellum
HindbrainLocated at the back of the brain. Maintains posture, balance, and coordinates smooth voluntary movements (walking, riding a bike).
Medulla Oblongata
HindbrainBrain stem connecting to the spinal cord. Controls simple involuntary actions like heartbeat, breathing, and blood pressure.
Spinal Cord
SpineBundle of nerves running down the spine. Transmits signals between brain and body. Controls rapid reflex actions.
Relay Neurons
Inside CNSFound within the brain and spinal cord. They connect sensory and motor neurons and process information.
Hypothalamus
ForebrainControls body temperature, hunger, thirst, and sleep. Links the nervous system to the endocrine system (hormones).
Peripheral Nervous System (PNS)
Sensory Nerves
Body → BrainNerves that carry information from sense organs (eyes, skin, etc.) TO the Central Nervous System for processing.
Motor Nerves
Brain → BodyNerves that carry instructions FROM the Central Nervous System to muscles and glands to execute actions.
Sympathetic Nervous System
Body-widePrepares the body for stressful situations: increases heart rate, dilates pupils, inhibits digestion.
Parasympathetic Nervous System
Body-wideCalms the body down: decreases heart rate, constricts pupils, stimulates digestion.
Mechanism
Reflex Arc
Spinal CordAutomatic response path: Stimulus → Receptor → Sensory Neuron → Spinal Cord (Relay) → Motor Neuron → Effector (Muscle).
Neural Structure
Synapse
Between NeuronsJunction between two neurons where electrical signals are converted into chemical signals (neurotransmitters) to transmit information.
Human Nervous System: Control & Coordination
The nervous system acts as the body's electrical wiring. It detects changes in the environment (stimuli), transmits information as electrical impulses, and triggers appropriate responses.
Two Major Divisions
Central Nervous System (CNS)
The processing center. It receives information, analyzes it, and decides the action.
- • Brain: The command center.
- • Spinal Cord: The highway for signals & reflexes.
Peripheral Nervous System (PNS)
The connection network. Nerves that connect the CNS to the rest of the body boundaries.
- • Sensory Nerves: Carry signals TO the brain.
- • Motor Nerves: Carry commands FROM the brain.
Structure of a Neuron
1. Dendrite
Receives chemical signals from other neurons and starts the electrical impulse.
2. Axon
Long tail that carries the electrical impulse away from the cell body. Often covered in Myelin for speed.
3. Nerve Ending
Releases neurotransmitters into the Synapse to pass the signal to the next cell.
Reflex Action Mechanism
Why is it so fast?
Reflex actions are involuntary and rapid because the decision is made by the Spinal Cord, not the Brain. This saves crucial time to prevent injury (like pulling a hand away from fire).
Frequently Asked Questions
What is the main difference between CNS and PNS?
The CNS (Central Nervous System) consists of the Brain and Spinal Cord and acts as the control center. The PNS (Peripheral Nervous System) consists of all the nerves branching out to the body, connecting the CNS to limbs and organs.
What is a Reflex Action?
A Reflex Action is a rapid, automatic response to a stimulus (like touching a hot surface) that is controlled by the Spinal Cord to protect the body, bypassing the Brain for speed.
What are the three main parts of the Brain?
The brain has three main regions: Forebrain (Cerebrum - thinking), Midbrain (Relay center), and Hindbrain (Cerebellum & Medulla - balance & life support).
What is the function of the Cerebellum?
The Cerebellum (or "Little Brain") is responsible for maintaining posture, balance, and coordinating smooth, voluntary muscle movements (like walking or riding a bike).
What is the role of Medulla Oblongata?
The Medulla controls involuntary life-sustaining functions such as heartbeat, breathing, blood pressure, and reflexes like vomiting or sneezing.
What is the basic unit of the Nervous System?
The Neuron (nerve cell) is the structural and functional unit. It transmits electrical and chemical signals throughout the body.
What is a Synapse?
A Synapse is the tiny gap between two neurons. Electrical signals cannot jump this gap, so they are converted into chemical signals (neurotransmitters) to cross it.
Which part of the brain controls body temperature?
The Hypothalamus (in the Forebrain) acts as the body's thermostat, regulating temperature, hunger, thirst, and sleep cycles.
What protects the Brain and Spinal Cord?
The Brain is protected by the Skull (Cranium), and the Spinal Cord is protected by the Vertebral Column (Backbone). Both are also cushioned by fluid (CSF) and membranes (Meninges).
Difference between Voluntary and Involuntary actions?
Voluntary actions are controlled consciously (e.g., lifting a hand) by the Cerebrum. Involuntary actions happen automatically (e.g., heart beating) and are controlled by the Medulla or Midbrain.