Voltage-gated calcium (Ca²⁺) channels are essential for converting membrane potential changes into intracellular Ca²⁺ transients, initiating various physiological processes. These channels are divided into ten subfamilies in mammals, each with distinct roles in cellular signaling. The CaV1 subfamily is involved in contraction, secretion, and synaptic transmission, while CaV2 is primarily responsible for fast synaptic transmission. CaV3 subfamily is important for repetitive firing in rhythmic cells. The article discusses the molecular relationships, physiological functions, and pharmacological properties of these channels. Ca²⁺ channels in various cell types activate on membrane depolarization, mediating Ca²⁺ influx in response to action potentials and subthreshold signals. The influx of Ca²⁺ serves as a second messenger, initiating cellular events such as contraction, secretion, and synaptic transmission. In cardiac and smooth muscle cells, Ca²⁺ channels initiate contraction by increasing cytosolic Ca²⁺ concentration. In skeletal muscle, these channels interact with ryanodine-sensitive Ca²⁺ release channels to initiate rapid contraction. In endocrine cells, they mediate hormone secretion, and in neurons, they initiate synaptic transmission. In many cell types, Ca²⁺ influx regulates enzyme activity, gene expression, and other biochemical processes. Ca²⁺ currents are classified based on physiological and pharmacological properties. L-type currents are slow to inactivate and are long-lasting when Ba²⁺ is the current carrier. T-type currents activate at more negative potentials and are transient. N-type currents are intermediate in voltage dependence and inactivation rate. P-type currents are highly sensitive to spider toxins, while Q-type currents are blocked by certain toxins. R-type currents are resistant to most organic and peptide blockers. The molecular structure of Ca²⁺ channels includes α1, α2δ, β, and γ subunits. The α1 subunit is a large protein with a transmembrane structure, while the α2δ subunit is extracellular and linked to the membrane via disulfide bonds. The β subunit is intracellular and phosphorylated, and the γ subunit is a glycoprotein with transmembrane segments. The three-dimensional structure of these channels is not well understood, but some structural features have been identified. The CaV1 subfamily is involved in excitation-contraction coupling in muscle, excitation-transcription coupling in nerve and muscle, and excitation-secretion coupling in endocrine cells and at specialized ribbon synapses. The regulation of these channels involves various signaling pathways, including those involving PKA, calmodulin, and calcineurin. The distal carboxy-terminal domain of these channels plays a role in regulation and can be proteolytically processed. Ca²⁺ channels also play a role in synaptic transmission, with presynaptic channels conducting P/Q-, N-, and R-type currents. These channels interact with SNARE proteins to facilitate neurotransmitter release. G protein modulation alsoVoltage-gated calcium (Ca²⁺) channels are essential for converting membrane potential changes into intracellular Ca²⁺ transients, initiating various physiological processes. These channels are divided into ten subfamilies in mammals, each with distinct roles in cellular signaling. The CaV1 subfamily is involved in contraction, secretion, and synaptic transmission, while CaV2 is primarily responsible for fast synaptic transmission. CaV3 subfamily is important for repetitive firing in rhythmic cells. The article discusses the molecular relationships, physiological functions, and pharmacological properties of these channels. Ca²⁺ channels in various cell types activate on membrane depolarization, mediating Ca²⁺ influx in response to action potentials and subthreshold signals. The influx of Ca²⁺ serves as a second messenger, initiating cellular events such as contraction, secretion, and synaptic transmission. In cardiac and smooth muscle cells, Ca²⁺ channels initiate contraction by increasing cytosolic Ca²⁺ concentration. In skeletal muscle, these channels interact with ryanodine-sensitive Ca²⁺ release channels to initiate rapid contraction. In endocrine cells, they mediate hormone secretion, and in neurons, they initiate synaptic transmission. In many cell types, Ca²⁺ influx regulates enzyme activity, gene expression, and other biochemical processes. Ca²⁺ currents are classified based on physiological and pharmacological properties. L-type currents are slow to inactivate and are long-lasting when Ba²⁺ is the current carrier. T-type currents activate at more negative potentials and are transient. N-type currents are intermediate in voltage dependence and inactivation rate. P-type currents are highly sensitive to spider toxins, while Q-type currents are blocked by certain toxins. R-type currents are resistant to most organic and peptide blockers. The molecular structure of Ca²⁺ channels includes α1, α2δ, β, and γ subunits. The α1 subunit is a large protein with a transmembrane structure, while the α2δ subunit is extracellular and linked to the membrane via disulfide bonds. The β subunit is intracellular and phosphorylated, and the γ subunit is a glycoprotein with transmembrane segments. The three-dimensional structure of these channels is not well understood, but some structural features have been identified. The CaV1 subfamily is involved in excitation-contraction coupling in muscle, excitation-transcription coupling in nerve and muscle, and excitation-secretion coupling in endocrine cells and at specialized ribbon synapses. The regulation of these channels involves various signaling pathways, including those involving PKA, calmodulin, and calcineurin. The distal carboxy-terminal domain of these channels plays a role in regulation and can be proteolytically processed. Ca²⁺ channels also play a role in synaptic transmission, with presynaptic channels conducting P/Q-, N-, and R-type currents. These channels interact with SNARE proteins to facilitate neurotransmitter release. G protein modulation also