Nervous System Overview and Organization

The brain, spinal cord, and all nerves that connect them to the body.

The most complex system in the human body, responsible for detecting and responding to changes.

The nervous system's ability to maintain a stable internal environment by regulating and controlling body functions.

The brain and spinal cord, which process and integrate information from the peripheral nervous system.

The network of nerves that carry sensory information to the CNS and motor commands from the CNS to the rest of the body.

The part of the PNS that controls voluntary movements and receives sensory information from the body.

The part of the PNS that controls involuntary functions like heart rate, digestion, and breathing.

The part of the autonomic nervous system that prepares the body for stress or action, like 'fight-or-flight.'

The part of the autonomic nervous system that promotes relaxation and digestion, like 'rest-and-digest.'

The basic building blocks of the nervous system, responsible for receiving, integrating, and transmitting information.

Specialized cells that support and protect neurons, providing physical support, nutrients, and insulation.

The most abundant type of glial cell, responsible for regulating the environment around neurons, contributing to the blood-brain barrier, and potentially to synapses.

A bundle of neurons that transmit information throughout the peripheral nervous system. They carry sensory information to the brain and spinal cord and motor commands to muscles and glands.

Neurons that carry information from sensory receptors to the central nervous system.

Neurons that transmit information within the central nervous system, connecting different parts of the brain and spinal cord.

Neurons that carry motor commands from the central nervous system to muscles and glands to produce movement and actions.

A simple neural circuit responsible for reflexive actions, allowing rapid responses to stimuli without conscious thought.

A reflex arc involving the withdrawal of a body part in response to a painful stimulus. It involves sensory neurons detecting pain, interneurons in the spinal cord, and motor neurons triggering muscle contraction.

Short, branching extensions of a neuron that receive signals from other neurons and relay them towards the cell body.

The central part of a neuron containing the nucleus, where metabolic reactions take place.

A long, single extension of a neuron that conducts nerve impulses away from the cell body towards other neurons.

A fatty insulating layer that surrounds some axons, speeding up the transmission of nerve impulses.

A type of glial cell that forms the myelin sheath around axons in the peripheral nervous system.

Tissue in the central nervous system composed of myelinated axons, appearing white.

Tissue in the central nervous system composed of unmyelinated neurons, appearing grey.

The difference in electrical charge between the inside and outside of a neuron's membrane when it is at rest.

The minimum level of stimulation required to trigger an action potential in a neuron.

A rapid electrical signal that travels down the axon of a neuron, carrying information.

The process of a neuron's membrane becoming less polarized, with the inside becoming less negative.

The process of a neuron's membrane returning to its resting potential after depolarization.

A brief period after an action potential during which a neuron is less sensitive to stimulation.

The speed at which a nerve impulse travels down an axon.

The space between the axon terminal of one neuron and the dendrite or cell body of another neuron.

A junction between two neurons, or between a neuron and a target cell (muscle or gland).

Chemical messengers released by neurons at synapses that transmit signals to the next cell.

The process by which a neurotransmitter is released from a presynaptic neuron and binds to receptors on a postsynaptic neuron.

A synapse where neurotransmitters stimulate the postsynaptic neuron, making it more likely to fire an action potential.

A synapse where neurotransmitters inhibit the postsynaptic neuron, making it less likely to fire an action potential.

The process by which neurotransmitters are removed from the synaptic cleft after transmission.

A type of neurotransmitter that is released by motor neurons at the neuromuscular junction and stimulates muscle contraction.

A type of neurotransmitter involved in mood, sleep, appetite, and learning.

A type of neurotransmitter involved in mood, attention, and reward.

A type of neurotransmitter involved in alertness, memory, and learning.

A type of neurotransmitter involved in inhibiting brain activity, promoting relaxation and sleep.

A type of neurotransmitter involved in stimulating brain activity and promoting arousal.

The junction between a motor neuron and a muscle fiber.

The process by which a nerve impulse from a motor neuron triggers a muscle contraction.

The neuron that releases the neurotransmitter.

The neuron that receives the neurotransmitter.

A neurotransmitter that increases the likelihood of the postsynaptic neuron firing an action potential.

A neurotransmitter that decreases the likelihood of the postsynaptic neuron firing an action potential.

When acetylcholine is released at the neuromuscular junction, it binds to receptors on muscle fibers, causing them to contract.

When an excitatory neurotransmitter binds to its receptor, it opens ion channels, allowing positive ions to flow into the postsynaptic neuron. This makes the neuron more likely to fire an action potential.

When an inhibitory neurotransmitter binds to its receptor, it opens ion channels, allowing potassium ions to flow out of the postsynaptic neuron, making it less likely to fire an action potential.

An imbalance in neurotransmitter levels can lead to various neurological and psychiatric disorders.

Low levels of dopamine are associated with Parkinson's disease, characterized by tremors, muscle stiffness, and difficulty moving.

High levels of dopamine are associated with schizophrenia, characterized by hallucinations, delusions, and thought disorders.

Low levels of serotonin are associated with depression, characterized by persistent sadness, loss of interest, and feelings of hopelessness.

Low levels of norepinephrine are associated with attention deficit hyperactivity disorder (ADHD), characterized by inattentiveness, hyperactivity, and impulsivity.

Low levels of GABA are associated with anxiety disorders, characterized by excessive worry, fear, and nervousness.

Some drugs are designed to impact neurotransmitter activity, either by increasing, decreasing, or mimicking their effects.

Antidepressants aim to increase serotonin levels in the brain.

Stimulants, like Ritalin, increase dopamine and norepinephrine levels, which can help improve focus and attention.

Benzodiazepines, like Xanax, increase GABA activity, reducing anxiety by calming brain activity.

The brain and spinal cord are the control center of the body, responsible for coordinating all activities.

The spinal cord is a vital communication link between the brain and the rest of the body, carrying signals for movement, sensation, and reflexes.

The spinal cord acts as a relay station for messages between the brain and the body, and also processes simple reflexes.

The spinal cord is protected by layers of bone (vertebrae), soft tissue (meninges), and cerebrospinal fluid, which acts like a cushion.

The brain is the main control center of the nervous system, responsible for complex thinking, emotions, movement, and many vital functions.

The cerebrum is the largest part of the brain responsible for higher-level functions like thinking, learning, memory, and personality.

The cerebellum is responsible for balance, coordination, and smooth muscle movements.

The brain stem regulates vital involuntary functions such as breathing, heart rate, and blood pressure.

The left and right hemispheres of the brain are connected by the corpus callosum, which allows them to communicate.

The frontal lobe is responsible for executive functions, planning, decision-making, and personality.

The parietal lobe is responsible for processing sensory information like touch, temperature, pain, and spatial awareness.

The occipital lobe is responsible for processing visual information and forming images.

The temporal lobe is involved in processing auditory information, language comprehension, and memory.

The midbrain controls visual reflexes and eye movements.

The pons relays sensory information between the cerebrum and the cerebellum.

The medulla oblongata controls vital functions like respiration, heart rate, and blood pressure.

The limbic system is responsible for emotions, motivation, and memory.

The amygdala is involved in processing emotions, especially fear and aggression.

The hippocampus is responsible for forming and retrieving new memories.