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SC1221
SET 1
| Term | Definition |
|---|---|
| neuron | the basic functional unit of the nervous stem that transmits electrical and chemical signals |
| dendrite | branch-line extensions of a neuron that receive signals from other neurons |
| axon | long projection of a neuron that transmits impulses away from the cell body |
| myelin sheath | fatty layer surrounding axons that speeds up nerve impulse conduction |
| node of ranvier | gaps in the myelin sheath where action potentials are regenerated |
| synapse | junction between two neurons where neurotransmitters are released to transmit signals |
| neurotransmitter | chemical messenger that carries signals across a synapse (e.g, dopamine, acetylcholine ) |
| resting membrane potential(RMP) | electrical potential across the neuronal membrane when the neuron is not firing (typically around -70mV) |
| action potential (AP) | rapid, temporary change in membrane potential that transmits a nerve impulse |
| depolarization | phase of the action potential when the membrane becomes more positive due to sodium influx |
| repolarization | phase when the membrane potential returns towards resting due to potassium efflux |
| hyper polarization | membrane potential becomes more negative than resting potential, often after an action potential |
| threshold potential | critical membrane potential (around -55mV) that must be reached to trigger an action potential |
| refractory period | time after an action potential when a neuron cannot fire (absolute) or requires a stronger stimulus (relative) |
| ligand-gated ion channel | ion channel that opens in response to a chemical signal (ligand), like a neurotransmitter |
| voltage-gated ion channel | ion channel that opens and closes in response to changes in membrane potential |
| saltatory conduction | rapid transmission of an action potential along a myelinated axon, jumping from one node of ranvier to the next |
| excitatory postsynaptic potential(EPSP) | small depolarization of a postsynaptic neuron , making it more likely to fire an action potential |
| Inhibitory postsynaptic potential(IPSP) | small hyper polarization of a postsynaptic neuron, making it less likely to fire |
| central nervous system(CNS) | brained spinal cord; the control center for processing information |
| peripheral nervous system(PNS) | nerves outside the CNS that connect the body to the CNS |
| afferent neuron | sensory neuron that carries information to the CNS |
| efferent neuron | motor neuron that carries information from the CNS to muscle or glands |
| Schwann cell | glial cell in the PNS that produces myelin |
| oligodendrocyte | glial cell in the CNS that produces myelin |
| muscle fiber | a single muscle cell, multinucleated, capable of contracting in response to stimulation. |
| myofibril | rod-like structures within muscle fibers composed of sarcomeres, the contractile units |
| sarcomere | The basic functional unit of a muscle fiber, made of actin (thin) and myosin (thick) filaments. |
| actin | Thin filament in a sarcomere that interacts with myosin for muscle contraction. |
| myosin | Thick filament in a sarcomere with heads that bind actin to generate contraction. |
| tropomyosin | Protein that blocks myosin binding sites on actin in relaxed muscle, |
| troponin | Protein complex on actin that binds calcium to initiate contraction. |
| neuromuscular junction (NMJ) | Synapse between a motor neuron and a muscle fiber where signals are transmitted via acetylcholine (ACh). |
| acetylcholine (ACh) | Neurotransmitter that triggers muscle contraction by depolarizing the muscle membrane. |
| action potential (muscle) | Electrical signal that travels along the sarcolemma and T-tubules to trigger contraction. |
| sarcolemma | Plasma membrane of a muscle fiber. |
| t-tubules | Invaginations of the sarcolemma that conduct action potentials deep into the muscle fiber |
| sarcoplasmic reticulum(SR) | specialized ER in muscle cells that stores and releases calcium ions (Ca'*) to trigger contraction. |
| calcium ions | bind to troponin, causing tropomyosin to move and expose myosin-binding sites on actin |
| cross-bridge | connection formed when myosin heads bind actin during contraction |
| sliding filament theory | mechanism of muscle contraction where actin slides past myosin, shortening the sarcomere |
| contraction | process where muscle fibers generate tension and shorten |
| relaxation | process where muscle fibers return to resting length after contraction |
| ATP(Adenosine Triphosphate) | energy molecule required for both contraction (myosin heads power stroke) and relaxation (pumping Ca2+ back to SR) |
| motor unit | a single motor neuron and all the muscle fibers it innervates |
| isotonic contraction | muscle changes length while tension remains constant (e.g., lifting a weight) |
| agonist | muscle primarily responsible for producing a movement |
| antagonist | muscle that oppose the action of the agonist |
| synergist | muscle that assist the agonist in performing a movement |
| isometric contraction | muscle generates tension without changing length (e.g., holding a weight steady) |
Created by:
user-1988957