Nervous system
64 flashcards covering Nervous system for the MCAT Biology & Biochemistry section.
The nervous system is your body's primary communication network, consisting of the brain, spinal cord, and a vast array of nerves that transmit signals throughout the body. It processes information from the environment, coordinates responses, and regulates functions like movement, sensation, and even thoughts. At its core, it relies on specialized cells called neurons that generate electrical impulses and communicate via chemical messengers, allowing for rapid reactions to stimuli and maintaining homeostasis.
On the MCAT, the nervous system appears frequently in Biology and Biochemistry questions, often testing anatomy, physiology, and integration with other systems through multiple-choice formats. Expect questions on neural pathways, neurotransmitter functions, or disorders like Parkinson's, with common traps including confusing sympathetic and parasympathetic responses or mixing up sensory and motor neurons. Focus on understanding key processes like action potentials, synaptic transmission, and reflex arcs, as these tie into passages on behavior, disease, or evolution.
A solid tip: Draw and label neural circuits to visualize how signals flow.
Terms (64)
- 01
Neuron
A neuron is a specialized cell that transmits nerve impulses throughout the body, consisting of a cell body, dendrites for receiving signals, and an axon for sending signals.
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Axon
An axon is a long, slender projection of a neuron that conducts electrical impulses away from the cell body to other neurons, muscles, or glands.
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Dendrite
Dendrites are branched extensions of a neuron that receive signals from other neurons and transmit them toward the cell body.
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Myelin sheath
The myelin sheath is a fatty layer that surrounds the axons of some neurons, insulating them and speeding up the transmission of electrical signals through saltatory conduction.
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Action potential
An action potential is a rapid change in the electrical charge across a neuron's membrane, triggered by depolarization when the membrane potential reaches a threshold, allowing signals to propagate along the axon.
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Resting membrane potential
Resting membrane potential is the electrical charge difference across a neuron's membrane at rest, typically around -70 millivolts, maintained by the sodium-potassium pump and ion leaks.
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Sodium-potassium pump
The sodium-potassium pump is a protein that actively transports three sodium ions out of the cell and two potassium ions into the cell, using ATP to maintain the resting membrane potential and regulate cell volume.
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Synapse
A synapse is the junction between two neurons where neurotransmitters are released from the presynaptic neuron to bind with receptors on the postsynaptic neuron, facilitating signal transmission.
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Neurotransmitter
A neurotransmitter is a chemical substance released from a neuron that crosses the synaptic cleft to transmit signals to another neuron or target cell, influencing functions like mood and muscle contraction.
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Acetylcholine
Acetylcholine is a neurotransmitter involved in muscle contraction, learning, and memory, released at neuromuscular junctions and certain synapses in the central nervous system.
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Dopamine
Dopamine is a neurotransmitter associated with reward, motivation, and movement, playing a key role in the brain's pleasure system and disorders like Parkinson's disease.
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Central nervous system
The central nervous system consists of the brain and spinal cord, serving as the primary control center for processing information, coordinating responses, and integrating sensory input.
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Peripheral nervous system
The peripheral nervous system includes all neural structures outside the brain and spinal cord, such as nerves and ganglia, responsible for transmitting signals to and from the central nervous system.
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Brain
The brain is the organ in the central nervous system that controls higher functions like thought, emotion, and voluntary movement, divided into regions such as the cerebrum, cerebellum, and brainstem.
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Cerebrum
The cerebrum is the largest part of the brain, responsible for higher cognitive functions, sensory processing, and voluntary movements, divided into two hemispheres and four lobes.
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Cerebellum
The cerebellum is a region at the back of the brain that coordinates voluntary movements, balance, and posture by integrating sensory information and fine-tuning motor commands.
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Brainstem
The brainstem is the lower part of the brain connecting to the spinal cord, controlling essential functions like breathing, heart rate, and arousal through structures such as the medulla oblongata.
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Spinal cord
The spinal cord is a bundle of nerves running through the vertebral column, transmitting signals between the brain and the body while also coordinating reflexes.
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Reflex arc
A reflex arc is a neural pathway that enables a rapid, involuntary response to a stimulus, typically involving a sensory neuron, interneuron, and motor neuron, bypassing higher brain centers.
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Sensory neuron
A sensory neuron carries signals from sensory receptors in the periphery to the central nervous system, detecting stimuli like touch, pain, or temperature.
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Motor neuron
A motor neuron transmits signals from the central nervous system to muscles or glands, enabling voluntary and involuntary movements and secretions.
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Interneuron
An interneuron connects other neurons within the central nervous system, processing information and facilitating communication between sensory and motor pathways.
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Autonomic nervous system
The autonomic nervous system regulates involuntary functions like heart rate and digestion, divided into the sympathetic and parasympathetic branches that often work in opposition.
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Sympathetic nervous system
The sympathetic nervous system prepares the body for 'fight or flight' responses by increasing heart rate, dilating pupils, and redirecting blood flow to muscles during stress.
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Parasympathetic nervous system
The parasympathetic nervous system promotes 'rest and digest' activities by slowing heart rate, stimulating digestion, and conserving energy after stress.
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Limbic system
The limbic system is a group of brain structures involved in emotion, memory, and motivation, including the amygdala and hippocampus, which influence behavior and learning.
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Hypothalamus
The hypothalamus is a brain region that regulates basic drives like hunger, thirst, and body temperature, as well as hormone release through the pituitary gland.
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Oligodendrocytes
Oligodendrocytes are glial cells in the central nervous system that produce myelin sheaths around axons, facilitating faster nerve impulse transmission.
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Astrocytes
Astrocytes are star-shaped glial cells that support neurons by maintaining the blood-brain barrier, regulating ion balance, and providing nutrients in the central nervous system.
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Microglia
Microglia are immune cells in the central nervous system that protect against pathogens and injury by engulfing debris and releasing inflammatory signals.
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Ependymal cells
Ependymal cells line the ventricles of the brain and the central canal of the spinal cord, producing cerebrospinal fluid and aiding in its circulation.
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Neuromuscular junction
The neuromuscular junction is the synapse between a motor neuron and a muscle fiber, where acetylcholine release triggers muscle contraction.
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Long-term potentiation
Long-term potentiation is a process that strengthens synaptic connections in the brain, believed to be a cellular basis for learning and memory through repeated stimulation.
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Habituation
Habituation is a simple form of learning where an organism decreases its response to a repeated, non-threatening stimulus, allowing it to ignore irrelevant information.
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Sensitization
Sensitization is a learning process where an organism increases its response to a stimulus after experiencing a strong or aversive event, heightening alertness.
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Pain pathways
Pain pathways are neural routes that transmit pain signals from sensory receptors through the spinal cord to the brain, involving substances like substance P for perception and response.
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Visual pathway
The visual pathway is the route that carries signals from the retina through the optic nerve to the visual cortex in the brain, processing light and forming images.
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Auditory pathway
The auditory pathway transmits sound signals from the cochlea via the auditory nerve to the brain's temporal lobe, enabling hearing and sound localization.
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Olfactory system
The olfactory system detects odors through receptors in the nasal cavity, sending signals directly to the brain's limbic system for smell perception and emotional associations.
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Taste buds
Taste buds are sensory structures on the tongue that detect chemicals in food, sending gustatory signals to the brain via the facial and glossopharyngeal nerves.
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Vestibular system
The vestibular system in the inner ear maintains balance and spatial orientation by detecting head movements and sending signals to the cerebellum and brainstem.
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Motor cortex
The motor cortex is a region in the frontal lobe of the cerebrum that plans and executes voluntary movements by sending commands to the spinal cord.
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Broca's area
Broca's area is a part of the frontal lobe involved in speech production and language comprehension, and damage to it can cause expressive aphasia.
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Wernicke's area
Wernicke's area in the temporal lobe is responsible for language understanding and processing, and its damage leads to receptive aphasia.
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Basal ganglia
The basal ganglia are a group of structures deep in the brain that help coordinate movement, regulate motor control, and are involved in habits and procedural learning.
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Thalamus
The thalamus acts as a relay station in the brain, routing sensory and motor signals to the appropriate cortical areas for processing.
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Hippocampus
The hippocampus is a structure in the temporal lobe essential for forming new memories and spatial navigation, and it is affected in Alzheimer's disease.
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Amygdala
The amygdala is part of the limbic system that processes emotions like fear and aggression, influencing the body's response to threats.
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Neuroplasticity
Neuroplasticity is the brain's ability to reorganize itself by forming new neural connections throughout life, especially in response to learning or injury.
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Synaptic cleft
The synaptic cleft is the small gap between the presynaptic and postsynaptic neurons where neurotransmitters are released and diffuse to transmit signals.
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Excitatory postsynaptic potential
An excitatory postsynaptic potential is a depolarization of the postsynaptic membrane that makes the neuron more likely to fire an action potential.
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Inhibitory postsynaptic potential
An inhibitory postsynaptic potential is a hyperpolarization of the postsynaptic membrane that makes the neuron less likely to fire an action potential.
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Summation
Summation is the process where multiple excitatory or inhibitory postsynaptic potentials combine at the neuron's axon hillock to determine whether an action potential occurs.
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Refractory period
The refractory period is the time after an action potential when a neuron cannot fire another one, divided into absolute and relative phases to ensure unidirectional signal propagation.
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Saltatory conduction
Saltatory conduction is the process by which action potentials jump between nodes of Ranvier in myelinated axons, making nerve signal transmission faster and more efficient.
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Neurotransmitter reuptake
Neurotransmitter reuptake is the process where neurotransmitters are taken back into the presynaptic neuron after release, terminating their action in the synapse.
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Endorphins
Endorphins are neurotransmitters that act as natural painkillers and mood elevators, released during exercise or stress to produce feelings of euphoria.
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Nernst equation
The Nernst equation calculates the equilibrium potential for an ion across a membrane based on its concentration gradient, such as for potassium in neurons, and is given by E = (RT/zF) ln([ion outside]/[ion inside]).
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Common trap: Confusing somatic and autonomic NS
A common error is mixing up the somatic nervous system, which controls voluntary skeletal muscles, with the autonomic nervous system, which handles involuntary functions like heart rate.
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Strategy for memorizing brain regions
To memorize brain regions, group them by function, such as associating the cerebrum with cognition and the brainstem with vital functions, and use mnemonics like acronyms for key structures.
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Example of reflex arc in action
In a reflex arc, touching a hot stove sends a signal via a sensory neuron to the spinal cord, which quickly activates a motor neuron to withdraw the hand without involving the brain.
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How action potential propagates
An action potential propagates along an axon by depolarizing the membrane at one point, triggering sodium influx that spreads to the next segment, continuing as a wave.
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Role of glial cells in repair
Glial cells aid in neural repair by forming scars after injury and supporting neuron survival, though they do not transmit signals themselves.
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Autonomic imbalance in stress
During chronic stress, the sympathetic nervous system can dominate, leading to issues like elevated blood pressure, while the parasympathetic system fails to restore balance.