Introduction to the Nervous System and the Brain

The Nervous System

• The nervous system controls every action you make, including breathing, resting, running, and playing.
• The nervous system consists of the central nervous system and the peripheral nervous system.
• The central nervous system consists of the brain and spinal cord.
• The peripheral nervous system consists of nerves spread throughout the body.

The Brain

• The brain is the command center of the nervous system and is found within the skull.
• It is responsible for processing information and sending messages to the body that control movement and regulate the body's functions.
• The brain is made up of billions of neurons.
• Neurons communicate with each other using electrical and chemical signals, allowing us to think, feel, and move.
• The brain gathers information from senses like sight, sound, and touch to understand the environment.
• It sends signals to the rest of the body to control movements and bodily functions like breathing and heart rate.
• The brain is divided into different parts, each with a specific function.

The Cerebrum

• The cerebrum is the largest part of the brain.
• It is responsible for thinking, problem-solving, and controlling our movements.
• The cerebrum is divided into two hemispheres, the left and the right.
• Each hemisphere is responsible for controlling different parts of our body.
• The two hemispheres work together to allow us to function as a whole.
• The left hemisphere controls the right side of the body, including movement and the senses.
• It is responsible for speech, reading, writing, mathematical calculations, and logical reasoning.
• The right hemisphere controls the movement and senses of the left side of the body.
• It plays a role in spatial reasoning, such as understanding maps and navigating through spaces.

The Cerebellum

• The cerebellum is located at the back of the brain.
• It controls balance and coordination.

Brain Regions

• The forebrain is the front part of the brain responsible for processing information from our senses, regulating emotions, and controlling movements. The cerebrum is part of the forebrain.
• The midbrain is the middle part of the brain responsible for controlling reflexes and eye movements.
• The hindbrain is the back of the brain responsible for regulating heartbeat, breathing, and other functions that we do not consciously control. The cerebellum and medulla oblongata are part of the hindbrain.
• The medulla oblongata is the base of the brainstem, which connects the brain to the spinal cord.

Nerves

• Nerves act as pathways through which the brain sends and receives information.
• They run throughout the body and connect to the brain and spinal cord.
• The senses of sight, touch, taste, and scent are sent to the brain through specific nerves.
• Some nerves control our muscles and help us move.

Neurons

• Neurons are special cells in our body that help us communicate and feel things.
• A neuron is made up of three main parts: the cell body, dendrites, and axon.
• The cell body contains the neuron's nucleus and other components.
• Dendrites receive information from other neurons.
• The axon directs nervous impulses to send information from the cell body to other neurons, muscles, or glands.

How the Nervous System Works

• In the example of picking up a pencil:
  • Your brain sends a signal through your spinal cord to the nerves that control the muscles in your arm and hand.
  • The muscles in your arm and hand contract, allowing you to reach out and grasp the pencil.
  • Sensory receptors in your fingers send information back to your brain about the pencil's weight, texture, and shape.
  • Your brain uses this information to adjust your grip on the pencil, making sure it is secure and comfortable to hold.
  • Your brain sends another signal to your arm and hand muscles to lift it off the desk.
• This example shows how the nervous system allows you to control your muscles and interact with the world around you.

Reaction Time

• Reaction time is the time between the nervous system detecting something and its reaction to it.

How Messages Travel

• In a reflex arc:
  • A sensory receptor in your skin detects a stimulus (e.g., heat) and sends a message along a sensory neuron to your spinal cord.
  • The message passes through an interneuron in the spinal cord.
  • The interneuron sends a message along a motor neuron that tells your muscles to move away from the stimulus.
  • Your body moves away from the stimulus. You feel a sensation of pain, which is another message that travels back to your brain.

Damaged Nerves

• The consequences of damage depend on the affected nerve type.
• Sensory nerve damage can cause loss of sensation or abnormal sensation.
• Motor nerve damage can cause paralysis or ineffective muscle function.
• Nerve damage can also cause changes in blood pressure, pulse rate, and breathing patterns. It can also cause muscular weakness, twitching, or spasms.
• The degree and duration of these effects vary based on injury location, nerve damage, and the person's health and recovery speed.

Keeping your Nervous System Healthy

• Eat a healthy diet with fruits, vegetables, and whole grains.
• Get plenty of exercise.
• Wear a helmet when riding a bicycle or motorcycle or when participating in activities that could result in injuries.
• Protect your spine by maintaining good posture and avoiding activities that could injure your back.
• Keep your posture straight and upright when you sit.