Glossary
Action Potential
A brief electrical charge that travels down the axon of a neuron, serving as the primary way neurons communicate with each other.
Example:
When a neuron reaches its threshold, it fires an Action Potential, sending a rapid electrical impulse along its length.
All-or-None Response
The principle that a neuron's action potential either fires completely at full strength or does not fire at all; there is no partial firing.
Example:
Just like flipping a light switch, a neuron's All-or-None Response means it's either fully on or fully off, never halfway.
Autonomic Nervous System
A division of the PNS that controls involuntary functions of internal organs and glands, such as heart rate, digestion, and breathing.
Example:
Even when you're asleep, your Autonomic Nervous System continues to regulate your breathing and heart rate without conscious effort.
Brain
The primary control center of the CNS, responsible for processing sensory information, making decisions, and initiating responses.
Example:
Your brain allows you to understand complex concepts, remember past events, and even dream.
Central Nervous System (CNS)
Composed of the brain and spinal cord, it serves as the main processing center for all information received from the body.
Example:
After touching a hot stove, your Central Nervous System quickly processes the pain signal and initiates a withdrawal reflex.
Chemical Synapse
A type of synapse where neurotransmitters are released from the presynaptic neuron and bind to receptors on the postsynaptic neuron, leading to a slower but more flexible signal transmission.
Example:
Most communication between neurons in the brain occurs at a Chemical Synapse, where neurotransmitters carry the message across the gap.
Depolarization
The process during the action potential when the inside of the neuron becomes more positive due to the influx of positively charged ions, allowing the electrical signal to propagate.
Example:
During Depolarization, sodium ions rush into the neuron, causing its internal charge to become less negative and initiating the action potential.
Electrical Synapse
A type of synapse where neurons are directly connected by gap junctions, allowing for very rapid and direct transmission of electrical signals.
Example:
In some parts of the brain, Electrical Synapses allow for extremely fast and synchronized communication between neurons.
Interneurons
Neurons located entirely within the central nervous system that process information between sensory input and motor output.
Example:
When you hear a question, Interneurons in your brain analyze the words and formulate an answer before you speak.
Motor (Efferent) Neurons
Neurons that carry outgoing information from the central nervous system to muscles and glands, initiating movement or glandular secretions.
Example:
To write a note, Motor (Efferent) Neurons transmit signals from your brain to the muscles in your hand and fingers.
Nervous System
The body's complex communication network that uses electrical and chemical signals to transmit messages throughout the body.
Example:
When you decide to pick up a pen, your nervous system coordinates the signals from your brain to your hand muscles.
Neuron's Threshold
The minimum level of stimulation required to trigger a neural impulse or action potential in a neuron.
Example:
A neuron will only fire an action potential if the incoming signals reach its specific Neuron's Threshold of excitation.
Neurons
The fundamental building blocks of the nervous system, specialized cells that transmit electrical and chemical signals to communicate information throughout the body.
Example:
Billions of neurons in your brain work together to allow you to think, learn, and remember.
Neurotransmitters
Chemical messengers that transmit signals across the synaptic gap between neurons, influencing whether the next neuron will fire or not.
Example:
Serotonin and dopamine are Neurotransmitters that play crucial roles in mood regulation and reward pathways.
Parasympathetic Nervous System
The 'rest and digest' subdivision of the autonomic nervous system, which calms the body after a stressful event, conserving energy and returning bodily functions to a normal state.
Example:
After a thrilling roller coaster ride, your Parasympathetic Nervous System helps slow your heart rate and bring your breathing back to normal.
Peripheral Nervous System (PNS)
Consists of all the nerves that extend from the brain and spinal cord to the rest of the body, connecting the CNS to organs, limbs, and skin.
Example:
The Peripheral Nervous System allows you to feel the texture of a sweater or move your fingers to type.
Reflexes
Automatic, involuntary responses to stimuli that are controlled by the spinal cord and occur without conscious thought.
Example:
When a bright light shines in your eyes, your pupils constrict as a protective reflex.
Sensory (Afferent) Neurons
Neurons that carry incoming information from sensory receptors (like eyes, ears, skin) to the central nervous system.
Example:
When you touch a cold ice cube, Sensory (Afferent) Neurons send the sensation of coldness from your fingertips to your brain.
Somatic Nervous System
A division of the PNS that controls voluntary movements of skeletal muscles and transmits sensory information from the body to the CNS.
Example:
When you consciously decide to kick a soccer ball, your Somatic Nervous System sends the commands to your leg muscles.
Spinal Cord
A long, thin, tubular bundle of nervous tissue that extends from the brainstem, serving as a major pathway for information between the brain and the rest of the body, and also handling reflexes.
Example:
A quick knee-jerk reaction when tapped below the kneecap is a spinal cord reflex, bypassing the brain for speed.
Sympathetic Nervous System
The 'fight or flight' subdivision of the autonomic nervous system, which prepares the body for stressful or emergency situations by increasing heart rate, dilating pupils, and diverting blood flow.
Example:
Before a big presentation, your Sympathetic Nervous System might cause your heart to pound and your palms to sweat.
Synapse
The tiny gap or junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron, where chemical communication occurs.
Example:
Information is passed from one neuron to another across the Synapse via the release of neurotransmitters.