Master this deck with 21 terms through effective study methods.
Generated from uploaded pdf
Neurons consist of a soma (cell body) that contains the nucleus and synthesizes molecules, dendrites that are excitable extensions with Na+, Ca2+, and K+ channels, an axon that conducts electrical signals to the synaptic terminal with high densities of Na+ and K+ channels, and synaptic terminals that contain Ca2+ channels and synaptic vesicles for neurotransmitter release.
The action potential is a rapid change in membrane potential that allows neurons to transmit signals over long distances. It is essential for communication between neurons and for the functioning of the nervous system.
The resting membrane potential is influenced by the concentrations of ions inside and outside the neuron, primarily K+ and Na+. The Nernst equation calculates the equilibrium potential for these ions, which helps establish the resting potential based on their concentration gradients.
The Nernst equation calculates the equilibrium potential for a specific ion based on its concentration inside and outside the cell. It is given by E = 58 mV log([ion]ext/[ion]int). This equation helps predict the direction of ion flow across the membrane.
When a neuron's membrane is permeable to both Na+ and K+, the Nernst equation is no longer applicable. Instead, the Goldman equation is used to calculate the membrane potential, taking into account the permeability of both ions and their concentrations.
The Goldman equation calculates the membrane potential (Vm) based on the relative permeabilities of different ions (K+ and Na+) and their concentrations inside and outside the cell. It provides a more accurate representation of the membrane potential when multiple ions are involved.
Voltage-gated Na+ and K+ channels are integral membrane proteins that change conformation in response to membrane potential. They are closed at resting potentials, begin to open at threshold potentials (around -35 mV), and are fully open at potentials above 0 mV, allowing for the influx or efflux of ions that generate action potentials.
The structure of ion channels, including transmembrane segments sensitive to voltage and segments that determine permeability, is crucial for their function. These structural features allow channels to open or close in response to changes in membrane potential, facilitating the flow of ions and the generation of electrical signals.
Synaptic terminals are the endpoints of axons where neurotransmitters are released. They contain high densities of Ca2+ channels that trigger the exocytosis of synaptic vesicles, allowing for the transmission of signals to other neurons or target cells.
The three major families of neurons are sensory neurons, which transmit sensory information; motor neurons, which send signals to muscles; and interneurons, which connect and process information between sensory and motor neurons.
The shape of a neuron, including the length of its axon and the complexity of its dendritic tree, reflects its function. For example, sensory neurons often have long dendrites to receive signals from the environment, while motor neurons have long axons to transmit signals to distant muscles.
Electrochemical equilibrium occurs when the concentration gradient of an ion is balanced by the electrical gradient, resulting in no net movement of that ion across the membrane. This is crucial for maintaining the resting membrane potential and the overall excitability of neurons.
The threshold potential is the critical level of depolarization that must be reached for an action potential to be initiated. It typically occurs around -35 mV, at which point voltage-gated Na+ channels open, leading to a rapid influx of Na+ and the generation of the action potential.
Ion channels, particularly voltage-gated Na+ and K+ channels, are essential for the propagation of action potentials. The opening and closing of these channels create localized changes in membrane potential that trigger adjacent channels to open, allowing the action potential to travel along the axon.
Myelin is a fatty substance that insulates axons, increasing the speed of action potential propagation through saltatory conduction. It allows the action potential to jump between nodes of Ranvier, where ion channels are concentrated, resulting in faster signal transmission.
Dysfunction of ion channels can lead to various neurological disorders, such as epilepsy, multiple sclerosis, and certain types of ataxia. These conditions may arise from abnormal ion channel activity, affecting neuronal excitability and communication.
During an action potential, the permeability of the membrane to Na+ increases rapidly, causing depolarization. Following this, K+ permeability increases, leading to repolarization. These changes in permeability are crucial for the rapid rise and fall of the action potential.
Ion concentration gradients, maintained by ion pumps and channels, are fundamental to neuronal excitability. The differences in ion concentrations across the membrane create the driving forces for ion movement, which is essential for generating action potentials and transmitting signals.
Experimental methods such as patch-clamp techniques, voltage-clamp experiments, and electrophysiological recordings are used to study neuronal action potentials. These methods allow researchers to measure ion currents, membrane potentials, and the dynamics of ion channel activity.
Neurotransmitters are chemical messengers released from synaptic terminals that bind to receptors on post-synaptic neurons, influencing their excitability and signaling. They can cause depolarization (excitatory) or hyperpolarization (inhibitory) of the post-synaptic membrane.
Calcium ions (Ca2+) play a crucial role in synaptic transmission by triggering the release of neurotransmitters from synaptic vesicles. When an action potential reaches the synaptic terminal, Ca2+ channels open, allowing Ca2+ influx, which initiates exocytosis of neurotransmitters.