1. Nguyen tac
Dung dong dien galvanic (dien mot chieu)
(luc dong va luc md dien) va dong faradic (dien ting).
2. Nofi kich thich
Doi vdi th in kinh: d ndi day than kinh gan da nhat (vi du ranh tren rong roc doi vdi day than kinh tru).
Doi vdi cO: diem van dong.
Neu kich thich ngat quang b ln g dong dien galvanic (dong dien mot chieu) se cd xung chti nhat (hay con goi la xung vuong). Dong dien faradic (dien ting, cd xung dinh nhon hai pha: mot pha am, mot pha dtfdng ldn hdn. Binh
va dong faradic se gay co cd do day than kinh do phan bo. Neu kich thich triic tiep vao cO cung gay diidc co cd.
3. Ctfcfng do cd sof (rheobase hay ngifdng kich thich)
Cifdng do cd sd la Clidng do nho nhat de gay diiOc co cd. Cac day than kinh co ngifOng kich thich khac nhau diidc tinh b ln g mA (milliampere)
mA
a (a)
► (b)
"L/VAAJVM(c)
Hinh 2.2: Cac loai xung thudng dung trong chan doan dien a - Xung ch ii nhat. b - Xung faradic. c - Xung gia faradic
d - Xung ludi cay. e - Xung hinh thang
BANG 2.1.: NGUCfNG KICH THICH CUA DAY THAN KINH
Day than kinh Ngi/dng kich thich (mA)
-DTK mat 1 - 2,5 -DTK tru 0,2 - 0,9 -DTK giQa 0,3 - 1,5 - DTK quay 0,9 - 2,7 - DTK cd bi 0,04 - 0,28 - DTK dui 0,44 - 1,7 - DTK hong to 0,4 - 2,5 - DTK chay 0,4 - 2,5 - DTK mac 0,2 - 2 - DTK hong be 0 , 2 - 2
Chi so" ngifdng binh thifdng la:
Ngifdng faradic
--- > i
NgUdng galvanic
Khi co thifdng ton thoai hoa than kinh chi so phan ly ngUdng ldn hdn 2.
4. Thcfi tri (chronaxie):
La thdi gian toi thieu lam cho co cd vdi mot cifdng do gap hai cifdng do cd sd.
— Thdi tri day than kinh: theo Bui Thieu Stf va Lai The Vinh binh thifdng thdi tri trung binh cua cac day than kinh la:
Day tru: 0,110 miligiay Day giiia: 0,124 miligiay Day chay: 0,141 miligiay
Day mac: 0,125 miligiay
- Thdi tri cac cd: binh thiidng thdi tri cac cd trong cd the tu: 0,08 den 0,72 miligiay.
+ Cac cd d co, than va goc chi (vai, canh tay, hong, dui): Cd mat trtfdc: 0,08 - 0,16 miligiay
Cd mat sau la: 0,16 - 0,32 miligiay
+ Cac cd d dau, mat va d ngon chi (c&ng tay, ban tay, cang chan, ban chan):
Cd mat trtfdc la: 0,16 - 0,32 miligiay. Cd mat sau la: 0,44 - 0,72 miligiay
Khi co hien tufpng thoai hoa than kinh hoan toan thi thdi tri co the tang gap 100 lan so vdi binh thudng. Trong qua trinh hoi phuc than kinh, thdi tri se giam dan, nhd vay ta theo ddi dtfdc sii hoi phuc than kinh.