The Myelin Sheath
The myelin sheath is a fatty, protective covering that surrounds many nerve fibers (axons) in the nervous system.
Functions of the Myelin Sheath
- Insulates nerve fibers like the plastic coating around an electrical wire.
- Protects neurons from damage.
- Allows electrical signals to travel much faster.
- Helps nerve cells communicate efficiently.
- Supports normal movement, thinking, sensation, and coordination.
Without healthy myelin, nerve signals slow down or become disrupted, causing problems with movement, sensation, memory, or thinking.
Neurons
A neuron is a specialized nerve cell that sends and receives information throughout the nervous system.
Neurons act as an interconnected information-processing network, allowing different parts of the body and brain to communicate.
Functions of Neurons
- Receive information from the body and environment.
- Process information.
- Send messages to other neurons, muscles, and glands.
- Control thoughts, emotions, movement, learning, memory, and body functions.
Every thought, movement, sensation, and emotion depends on billions of neurons working together.
Neurotransmitters
A neurotransmitter is a chemical messenger used by neurons to communicate with one another.
When an electrical signal reaches the end of a neuron, neurotransmitters are released into the tiny gap between neurons (called the synapse).
The neurotransmitters then bind to receptors on the next neuron, allowing the message to continue.
Examples of Neurotransmitters
| Neurotransmitter | Function |
|---|---|
| Dopamine | Movement, reward, motivation |
| Serotonin | Mood, sleep, appetite |
| Acetylcholine | Learning, memory, and muscle movement |
| GABA | Calms brain activity |
| Glutamate | Learning and memory (main excitatory neurotransmitter) |
| Norepinephrine | Alertness, attention, stress response |
Receptors
A receptor is a protein located on the surface of a neuron or other cell.
Its job is to receive neurotransmitters.
When the correct neurotransmitter attaches to its matching receptor (similar to a key fitting into a lock), the receiving cell responds.
Receptors
- Detect chemical messages.
- Receive neurotransmitters.
- Start or stop electrical signals.
- Help regulate communication between neurons.
Memory
Memory is the brain's ability to store, retain, and retrieve information.
There are several types of memory.
Short-Term Memory
Short-term memory is the brain's temporary storage system.
It keeps information active for a short period while you use it.
Rather than being stored in a single location, short-term memory mainly depends on the prefrontal cortex, particularly for temporarily holding and manipulating information.
Functions
- Holds information for immediate use.
- Helps with problem-solving.
- Supports conversations.
- Helps you remember instructions for a short time.
Capacity
- About 4–7 pieces of information at one time.
Duration
- Around 15–30 seconds unless the information is repeated or rehearsed.
Examples
- Remembering a phone number long enough to dial it.
- Keeping a shopping item in mind.
- Following spoken directions.
Working Memory
Working memory is closely related to short-term memory but involves actively using and manipulating information rather than simply storing it.
Examples
- Solving mental arithmetic.
- Reading while remembering the previous sentence.
- Following several-step instructions.
- Planning what to say next in a conversation.
The prefrontal cortex plays a major role in working memory.
Long-Term Memory
Long-term memory stores information for days, years, or even a lifetime.
Unlike short-term memory, it has an extremely large capacity.
Long-term memories include:
- Facts
- Experiences
- Skills
- Language
- Personal memories
- Knowledge
The Hippocampus
The hippocampus is a small structure located deep within the brain.
It is essential for forming new long-term memories.
Rather than permanently storing memories itself, the hippocampus acts like a router or filing system, organizing new information and helping transfer it into long-term storage in different areas of the neocortex.
Functions of the Hippocampus
- Forms new memories.
- Helps convert short-term memories into long-term memories.
- Supports learning.
- Helps with spatial navigation (remembering places and directions).
Damage to the hippocampus can make it difficult to form new long-term memories.
The Neocortex
The neocortex is the outer layer of the brain and serves as the brain's long-term storage area.
Different types of memories are stored in different regions of the neocortex.
Examples include:
- Visual memories
- Language
- Knowledge
- Skills
- Personal experiences
How Information Moves into Long-Term Memory
Learning generally follows these steps:
- Information enters through the senses.
- The prefrontal cortex holds it briefly in short-term or working memory.
- If the information is repeated, meaningful, or emotionally important, the hippocampus organizes and strengthens it.
- During sleep and repeated practice, the hippocampus helps transfer the memory to the neocortex for long-term storage.
- Later, the stored memory can be retrieved when needed.
Short-Term Memory vs. Long-Term Memory
| Feature | Short-Term Memory | Long-Term Memory |
|---|---|---|
| Main Brain Area | Prefrontal cortex | Hippocampus (formation) and neocortex (storage) |
| Purpose | Temporary information | Permanent information |
| Capacity | About 4–7 items | Effectively unlimited |
| Duration | 15–30 seconds | Days to a lifetime |
| Examples | Phone number, directions | Childhood memories, riding a bicycle, vocabulary |
Summary
- Myelin sheath: Fatty insulation around axons that speeds up nerve impulses.
- Neurons: Specialized nerve cells that receive, process, and send information throughout the nervous system.
- Neurotransmitters: Chemical messengers that allow neurons to communicate.
- Receptors: Proteins on cells that receive neurotransmitters and trigger a response.
- Short-term memory: Temporary storage mainly supported by the prefrontal cortex.
- Working memory: Active use and manipulation of information held in short-term memory.
- Hippocampus: Forms and organizes new long-term memories.
- Neocortex: Stores long-term memories across many areas of the brain.
- Long-term memory: A vast, long-lasting storage system for knowledge, skills, and life experiences.
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