IB MYP Integrated Science- Biology - Nervous system-Study Notes - New Syllabus

Nervous System

🌟 Introduction

The nervous system is the body’s control and communication network.
It helps us sense, think, move, and respond to changes inside and outside the body.
It works using electrical signals (nerve impulses) and chemical messages (neurotransmitters).

🧩 What the Nervous System Does?

• Detects changes (stimuli)
• Processes information
• Sends commands to muscles and glands
• Maintains body coordination
• Enables learning, memory, emotions, thinking

🧬 Basic Unit: The Neuron

Structure of a Neuron

• Dendrites – receive signals
• Cell body – has nucleus, controls activities
• Axon – carries impulses away
• Myelin sheath – insulates axon, speeds impulses
• Axon terminals – pass signal to next cell

Types of Neurons

• Sensory neurons
  Carry impulses from sense organs to CNS
• Motor neurons
  Carry impulses from CNS to muscles/glands
• Interneurons
  Connect neurons inside CNS

🧠 Divisions of the Nervous System

A) Central Nervous System (CNS)

Made of brain + spinal cord

• Receives information
• Processes it
• Sends decisions to body

Brain Parts

• Cerebrum
  Thinking, memory, learning
  Voluntary actions
• Cerebellum
  Balance, posture
  Coordination of movement
• Medulla (brainstem)
  Controls involuntary actions
  Breathing, heartbeat, swallowing

Spinal cord

• Main pathway between brain and body
• Controls reflex actions

B) Peripheral Nervous System (PNS)

All nerves outside CNS.

Two Divisions

• Somatic nervous system
  Voluntary movements
• Autonomic nervous system
  Involuntary functions
  • Sympathetic – fight or flight
  • Parasympathetic – rest and digest

⚡ How a Nerve Impulse Travels

• Stimulus detected
• Electrical impulse travels along axon
• Jumps across synapse using neurotransmitters
• Next neuron carries signal forward

Synapses ensure one-way transmission.

🛡️Reflex Actions

Quick, automatic responses that protect the body.

Example:
Touching something hot → sensory neuron → spinal cord → motor neuron → pull hand away

Reflex arc components:

Stimulus → receptor → sensory neuron → interneuron → motor neuron → effector

👁️ Sense Organs & Their Roles

• Eye – vision, light detection
• Ear – hearing + balance
• Tongue – taste
• Skin – touch, temperature, pain
• Nose – smell

These organs provide input to nervous system.

🔌 Coordination with Other Systems

• Works with endocrine system to maintain homeostasis
• Controls muscles, enabling movement
• Links with respiratory and circulatory systems to match oxygen needs
• Controls digestion via autonomic nerves

⚠️ Disorders of the Nervous System

• Stroke
• Paralysis
• Parkinson’s disease
• Alzheimer’s
• Epilepsy
• Multiple sclerosis (myelin damage)

📌 Summary Table

⚡ Quick Recap 
Nervous system controls everything you feel, think, and do.
Neurons carry impulses using electrical and chemical signals.
CNS = brain + spinal cord; PNS = all nerves.
Brain has cerebrum (thinking), cerebellum (coordination), medulla (involuntary).
Reflex actions protect the body and are very quick.
Sense organs provide sensory input.
Works closely with all organ systems to maintain balance.