20. Nervous System #biology #saat #تحصيلي #riyadh

🐚 Cochlea “a snail‑shaped structure… filled with fluid and lined with tiny hair cells.” ⚡ Action Potential “another name for a nerve impulse.” 💊 Drug “a substance, natural or artificial, that alters the function of the body.” 🎯 Dopamine “a neurotransmitter found in the brain that is involved with the control of body movements and other functions.” 🧠 Sympathetic Nervous System “controls organs and is most active during emergencies or stress.” 😌 Parasympathetic Nervous System “controls organs and is most active when the body is at rest.” 🌿 Dendrite “receives impulses from other neurons and transmits them to the cell body.” 🔗 Axon “transmits nerve impulses from the cell body to other neurons and muscles.” 🧬 Cell Body “consists of the neuron's nucleus and many of the cell organelles.” 🔄 Pons “relays signals between the cerebrum and cerebellum.” 🧩 Medulla Oblongata “relays signals between the brain and the spinal cord.” 🌡️ Hypothalamus “regulates body temperature, thirst, appetite, and water balance.” 🧠 Cerebrum “the largest part of the brain… divided into two halves called hemispheres.” 👂 Somatic Nervous System “relays information from external sensory receptors to the central nervous system.” ❤️ Autonomic Nervous System “carries impulses from the central nervous system to the heart and other internal organs.” 🛰️ Peripheral Nervous System “consists of sensory and motor neurons; transmits information to and from the brain and spinal cord.” 🧭 Central Nervous System “coordinates all of the body's activities; consists of the brain and spinal cord.” 🔌 Neuron “specialized cells that help you gather information, interpret it, and react to it.” 🔍 Lens “the part behind the iris that inverts an image and focuses it on the retina.” 🎚️ Threshold “the minimum stimulus to cause an action potential to be produced.” 🌙 Rods “light‑sensitive cells that are excited by low levels of light.” 🌈 Cones “function in bright light and provide information about color to the brain.” 🧪 Neurotransmitter “a chemical that diffuses across a synapse then binds to receptors of the dendrite of a neighboring neuron.” 🟦 Node “gap in the myelin sheath along the length of an axon.” 🔀 Synapse “gap between one neuron’s axon and another neuron’s dendrite.” 🔁 Reflex Arc “a nerve pathway that consists of a sensory neuron, an interneuron, and a motor neuron.” 👁️ Retina “innermost layer of the eye that contains rods and cones.” 🔄 Semicircular Canals “inner‑ear structure that transmits information about body position and balance to the brain.” 🔗 Addiction “the psychological and physiological dependence on a drug.” 💤 Depressant “drugs that slow down the central nervous system.” ⚡ Stimulant “drugs that increase alertness and physical activity.” 📈 Tolerance “occurs when a person needs more and more of the same drug to get the same effect.”