This actuating member (5) is equipped with: a push/pull member (30) comprising a first moving part (31) and second moving part (32) which are positioned on the base end-side of the long member (10) and which can move relative to one another in the axial direction of the long member (10), a first stretched part (33) that is stretched from the first moving part (31) to the tip-side of the long member (10), and a second stretched part (34) that is stretched from the second moving part (32) to the tip-side of the long member (10), the push/pull member (30) being pushed/pulled in the axial direction of the long member (10) in conjunction with the movement of the moving parts (31, 32) and a control member (40) which controls the movement of the moving parts (31, 32), and which is provided so as to be able to rotate in the circumferential direction of the long member (10). The control member (40) is equipped with: a first guiding part (41) that is tilted with respect to the plane (CS) orthogonal to the axial direction of the long member (10), and which guides the movement of the first moving section (31), and a second guiding part (42) that is tilted with respect to the orthogonal plane (CS), and which guides the movement of the second moving part (32).Élément dactionnement (5) qui est équipé dun élément de traction-poussée (30) comprenant une première partie mobile (31) et une seconde partie mobile (32) positionnées sur le côté terminal de base dun élément allongé (10) et pouvant se déplacer lune par rapport à lautre dans la direction axiale de lélément allongé (10), une première partie allongée (33) qui sétend de la première partie mobile (31) à la pointe de lélément allongé (10), et une seconde partie allongée (34) qui sétend de la seconde partie mobile (32) à la pointe de lélément allongé (10), lélément de traction-poussée (30) étant poussé/tiré dans la direction axiale de lélément allongé (10) en conjonction avec le mouvement des parties mobiles (31, 32), et dun éléme
