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An action potential is a large, all-or-none electrical signal that travels along the axon of a neuron, allowing for the transmission of information. It occurs when a neuron depolarizes, reaching a threshold that triggers the opening of voltage-gated sodium channels, leading to a rapid influx of sodium ions.
Saltatory conduction is the process by which an action potential 'jumps' from one node of Ranvier to another along a myelinated axon. This increases the speed of conduction and efficiency of signal transmission in the nervous system.
The refractory period is the time following an action potential during which a neuron cannot fire again. This period is crucial for ensuring that action potentials are discrete events and helps to maintain the directionality of signal transmission.
A synapse is the junction between two neurons where neurotransmitters are released to transmit signals. It plays a critical role in communication within the nervous system, allowing for the transfer of information between neurons.
Neurotransmitters are chemicals that transmit signals across synapses from one neuron to another. They bind to receptors on the postsynaptic neuron, leading to changes in membrane potential and influencing neuronal activity.
Myelin is an insulating layer that surrounds the axons of some neurons, increasing the speed of electrical conduction. It is produced by oligodendrocytes in the CNS and Schwann cells in the PNS.
Oligodendrocytes are the cells that myelinate axons in the central nervous system (CNS), while Schwann cells perform this function in the peripheral nervous system (PNS).
Astrocytes are star-shaped glial cells in the CNS that provide support to neurons, maintain the blood-brain barrier, and regulate blood flow and nutrient supply to the nervous tissue.
Microglia are the resident immune cells of the CNS that act as phagocytes, removing debris and dead cells, and playing a role in the immune response within the brain and spinal cord.
The resting membrane potential is the electrical potential difference across the neuronal membrane when the neuron is not firing, typically around -70 mV. It is primarily determined by the distribution of ions, particularly sodium and potassium, across the membrane.
Sodium (Na+) is the ion that is predominantly found outside the neuron. Its concentration gradient is crucial for the generation of action potentials, as it enters the neuron during depolarization.
Potassium (K+) is primarily found inside the neuron. It plays a key role in repolarization during action potentials, as it exits the neuron to restore the resting membrane potential.
During depolarization, the neuron's membrane potential becomes less negative, moving towards zero. This is primarily due to the influx of sodium ions (Na+) through voltage-gated sodium channels.
Repolarization is the process that restores the membrane potential to a more negative value after depolarization. This is primarily achieved by the efflux of potassium ions (K+) from the neuron.
Hyperpolarization is a change in the membrane potential that makes it more negative than the resting potential. This decreases neuronal excitability and makes it less likely for the neuron to fire an action potential.
A graded potential is a small, local change in membrane potential that varies in magnitude and can summate. Unlike action potentials, which are all-or-none events, graded potentials can be depolarizing or hyperpolarizing and do not always lead to an action potential.
In muscle anatomy, 'adductor' refers to muscles that move a limb toward the midline of the body, playing a crucial role in various movements and stability.
'Rectus' refers to muscles that are straight in alignment, often used to describe certain muscle groups such as the rectus abdominis.
'Oblique' refers to muscles that are positioned at an angle, often involved in rotational movements and stabilization of the trunk.
The main function of the nervous system is to control and communicate information throughout the body, coordinating responses to internal and external stimuli.
The central nervous system (CNS) is made up of the brain and spinal cord, which are responsible for processing information and coordinating responses.
Sensory neurons carry impulses from sensory receptors to the central nervous system, allowing the body to perceive and respond to environmental stimuli.
Motor neurons carry impulses away from the central nervous system to effectors such as muscles and glands, facilitating movement and physiological responses.
Gray matter consists of neuron cell bodies and is involved in processing information, while white matter is made up of myelinated axons that facilitate communication between different brain regions.