Neurons Flashcards
What are the main components of a typical neuron?
The main components are the cell body (soma), dendrites, axon, axon terminals, and the myelin sheath.
What is the function of the cell body (soma) in a neuron?
The cell body contains the nucleus, which stores genetic information, and organelles like mitochondria that provide energy. It integrates signals received by the dendrites.
What is the function of dendrites in a neuron?
Dendrites are branched extensions that receive electrical signals (neurotransmitters) from other neurons and transmit them to the cell body.
What is the function of the axon in a neuron?
The axon is a long projection that carries electrical impulses away from the cell body to the axon terminals or another neuron.
What is the myelin sheath and its function?
The myelin sheath is a fatty covering surrounding the axon, which insulates the axon and increases the speed of electrical signal transmission.
What are Nodes of Ranvier, and why are they important?
Nodes of Ranvier are gaps in the myelin sheath where the axon is exposed. They help in saltatory conduction, which allows the electrical signal to jump from node to node, speeding up transmission.
What are axon terminals, and what is their function?
Axon terminals are the ends of the axon where neurotransmitters are released to transmit signals to the next neuron or muscle.
What is the synapse, and how does it function?
The synapse is the junction between two neurons or a neuron and a target cell, where neurotransmitters are released from the axon terminal to carry the signal across the gap to the next cell.
How are neurons classified based on their structure?
Neurons are classified as multipolar, bipolar, and unipolar, based on the number of processes extending from the cell body.
What is a multipolar neuron, and where is it found?
A multipolar neuron has one axon and multiple dendrites. It is the most common type, found in the CNS (brain and spinal cord).
What is a bipolar neuron, and where is it typically found?
A bipolar neuron has one axon and one dendrite. It is commonly found in the sensory organs, such as the retina of the eye and olfactory system.
What is a unipolar neuron, and where is it found?
A unipolar neuron has one process extending from the cell body, which splits into two branches. It is found in sensory neurons of the peripheral nervous system.
How are neurons classified based on their function?
Neurons are classified as sensory (afferent) neurons, motor (efferent) neurons, and interneurons (relay neurons) based on the direction they transmit signals.
What is the function of sensory (afferent) neurons?
Sensory neurons carry signals from sensory receptors (like skin or organs) to the CNS for processing.
What is the function of motor (efferent) neurons?
Motor neurons carry signals from the CNS to muscles or glands to produce movement or secretions.
What is the function of interneurons (relay neurons)?
Interneurons are found within the CNS and connect sensory neurons to motor neurons, facilitating communication between different parts of the nervous system.
What are neuroglia (glial cells), and what is their general function?
Neuroglia, or glial cells, are supporting cells of the nervous system that provide structural support, protection, insulation, and assist in the maintenance and repair of neurons.
What are the four types of glial cells found in the Central Nervous System (CNS)?
The four types are astrocytes, oligodendrocytes, microglia, and ependymal cells.
What is the function of astrocytes, and where are they located?
Astrocytes are found throughout the CNS. Their functions include maintaining the blood-brain barrier, regulating ion concentrations, providing nutrients to neurons, and aiding in repair after injury.
What is the function of oligodendrocytes, and where are they located?
Oligodendrocytes are located in the CNS and are responsible for producing the myelin sheath that insulates axons, speeding up electrical signal transmission.
What is the function of microglia, and where are they located?
Microglia are the immune cells of the CNS, located throughout the brain and spinal cord. They act as phagocytes, removing cellular debris, pathogens, and dead neurons.
What is the function of ependymal cells, and where are they located?
Ependymal cells line the ventricles of the brain and the central canal of the spinal cord. They produce and circulate cerebrospinal fluid (CSF), which cushions the brain and spinal cord.
What are the two types of glial cells found in the Peripheral Nervous System (PNS)?
The two types are Schwann cells and satellite cells.
What is the function of Schwann cells, and where are they located?
Schwann cells are found in the PNS and form the myelin sheath around peripheral axons, similar to oligodendrocytes in the CNS, aiding in the rapid transmission of electrical signals.
What is the function of satellite cells, and where are they located?
Satellite cells are located in ganglia of the PNS. They provide support and regulate the exchange of nutrients and waste between neurons and the surrounding environment.
How do Schwann cells differ from oligodendrocytes in terms of myelination?
Schwann cells in the PNS myelinate a single axon, while oligodendrocytes in the CNS can myelinate multiple axons at once.
Why are neuroglia critical for neuronal function?
Neuroglia provide support, nourishment, and protection to neurons, maintain the homeostasis of the neural environment, and play key roles in repair and immune defense in the CNS and PNS.
How do glial cells contribute to the blood-brain barrier?
Astrocytes in the CNS help maintain the blood-brain barrier by regulating the passage of substances from the bloodstream to the brain, protecting neural tissue from harmful chemicals.
What role do glial cells play in neural repair?
Schwann cells assist in repairing peripheral nerves by guiding the regrowth of damaged axons, while astrocytes help form scar tissue and support CNS recovery after injury.
What is the resting membrane potential of a neuron?
The resting membrane potential is the electrical charge difference across the cell membrane when the neuron is not transmitting a signal. It is typically around -70 mV.
What causes the resting membrane potential to be negative inside the cell?
The inside of the cell is negative due to a higher concentration of negatively charged proteins and potassium ions (K⁺), along with a lower concentration of positively charged sodium ions (Na⁺) compared to the outside.
What are the key ions involved in establishing the resting membrane potential?
The key ions are potassium (K⁺), sodium (Na⁺), and chloride (Cl⁻). K⁺ is more concentrated inside the cell, while Na⁺ and Cl⁻ are more concentrated outside the cell.
What is the role of the sodium-potassium pump (Na⁺/K⁺ pump) in maintaining the resting membrane potential?
The Na⁺/K⁺ pump uses ATP to actively transport 3 Na⁺ ions out of the cell and 2 K⁺ ions in, helping to maintain the concentration gradients of sodium and potassium, which are crucial for the resting membrane potential.
Why is the sodium-potassium pump considered electrogenic?
The Na⁺/K⁺ pump is electrogenic because it moves 3 positively charged Na⁺ ions out of the cell for every 2 positively charged K⁺ ions it brings in, creating a net negative charge inside the cell.
What role do potassium ions (K⁺) play in establishing the resting membrane potential?
K⁺ ions tend to move out of the cell through leak channels due to their concentration gradient, but are pulled back inside by the negative charge inside the cell. This movement is crucial for maintaining the negative resting potential.
How does the permeability of the membrane to different ions affect the resting membrane potential?
The membrane is more permeable to K⁺ than Na⁺, allowing K⁺ to move out of the cell more easily, contributing to the negative charge inside. The low permeability to Na⁺ helps keep the inside of the cell negative.
What is the equilibrium potential of potassium (K⁺), and why is it important?
The equilibrium potential of K⁺ is around -90 mV. It represents the point at which the electrical force pulling K⁺ in and the concentration gradient pushing K⁺ out are balanced, helping to set the resting membrane potential.
What is the role of sodium ions (Na⁺) in the resting membrane potential?
Sodium ions have a low permeability at rest, but a small amount leaks into the cell, making the resting membrane potential slightly less negative than the K⁺ equilibrium potential.
How do chloride ions (Cl⁻) influence the resting membrane potential?
Chloride ions are negatively charged and tend to be more concentrated outside the cell. They passively distribute across the membrane, stabilizing the negative resting membrane potential.
How does the resting membrane potential prepare a neuron for action potential generation?
The resting membrane potential establishes a polarized state (inside negative, outside positive), allowing the neuron to respond quickly to stimuli and generate an action potential when depolarized.
What happens to the resting membrane potential if the Na⁺/K⁺ pump is inhibited?
If the Na⁺/K⁺ pump is inhibited, the concentration gradients of Na⁺ and K⁺ would gradually dissipate, leading to a loss of the resting membrane potential and impairing the neuron’s ability to generate action potentials.
What is a graded potential in the nervous system?
A graded potential is a temporary change in the membrane potential of a neuron, usually occurring in the dendrites or cell body. It varies in size depending on the strength of the stimulus.
How does a graded potential differ from an action potential?
Graded potentials are small, local, and variable in magnitude, while action potentials are all-or-nothing and always of the same magnitude once the threshold is reached.
What causes graded potentials to occur?
Graded potentials are caused by opening of ion channels in response to a stimulus such as neurotransmitters binding to receptors, light, pressure, or changes in temperature.
What are the two types of graded potentials?
The two types of graded potentials are depolarizing potentials (making the inside of the cell less negative) and hyperpolarizing potentials (making the inside more negative).
What is a depolarizing graded potential?
A depolarizing graded potential occurs when the membrane potential becomes less negative (closer to zero) due to influx of Na⁺ ions or other positive ions, making the neuron more likely to fire an action potential.
What is a hyperpolarizing graded potential?
A hyperpolarizing graded potential makes the membrane potential more negative (further from zero) due to efflux of K⁺ ions or influx of Cl⁻ ions, making it less likely that an action potential will be generated.
