VIII. DIEN THE KICH THICH CAM GlAC THAN THE 1 Dai cifdng
2. Giai phau dtfdng dan truyen cam giac
a. Ccf the ngiidi co nhieu loai cam giac
- Cam giac nong: cam giac xuc giac (sd), dau, nhiet (nong, lanh).
Cam giac sau: cam giac 0 cO, gan, xtfdng, khdp (gom cam giac sau cd y thtfc va cam giac sau khong cd y thtfc).
Cam giac giac quan: thinh giac, khtiu giac, thi giac, vi giac, thang bing.
b. He thong truyen vd phan tich cam giac
- Thu the cam giac (receptor): la ndi tiep nhan cac xung dong than kinh dau tien. Dd la nhtfng d&u tan cung cua cac duoi gai cua neuron cam giac thtf nhat. Nd nam d da, cd, xtfdng khdp, quanh cac mach mau, mang nao. 0 moi vi tri nd deu cd dac ti'nh dac hieu rieng, cd nghia la moi loai thu the chi tiep nhan mot loai kich thich nhat dinh nhtf xuc giac, dau, nhiet
- Dtfdng dan truyen cam giac: moi dtfdng dan truyen cam giac gom cd 3 neuron (hinh 2.5)
+ DUdng cam giac nong:
• Neuron 1:
Than te bao nam d hach gai
Duoi gai (dendrid hay sdi ngoai vi: prolongement cellulipete) nhan cac kich thich ttf cac thu the dac hieu d ngoai vi va tham gia vao cau tao cac day than kinh.
Sdi true (axon hay sdi trung Udng: prolongement cellulifuge) khdp noi vdi neuron 2.
• Neuron 2:
Than te bao nam d sting sau cua tuy. Duoi gai: khdp noi vdi neuron 1
Sdi true: di len doc theo tuy song va tan cting d doi thi. Dtfdng di trong tuy cua cac neuron nay khac nhau tuy theo tting loai cam giac:
Cam giac sd: sdi true di cheo qua mep xam sau tdi cot ben cua ben doi dien lam thanh bo gai - lifdi - thi (faisceau spinoreticulo - thalamique).
Cam giac dau va nhiet: sdi true di cheo qua mep xam trtfdc tdi cot ben cua ben doi dien lam thanh bo gai - thi (faisceau spinothalamique). Cac sdi bat cheo khong phai d cung mot mtic khoanh tuy ma cac sdi bat cheo d cao hdn 2 - 3 khoanh tuy. Bo gai thi theo cot ben qua hanh, cau, cuong nao va tan cung d nhan ben doi thi.
• Neuron 3: di tti doi thi len vo nao cting ben va tan cting d phan trUdc cua hoi dinh len.
+ Diidng cam giac sau
Diidng cam giac sau cd y thtic, gom 3 neuron (hinh 2.5): Neuron 1:
Than te bao n&m d hach gai
Duoi gai tham gia vao cau tao day than kinh cam giac, nhan cac ki'ch thi'ch d cd, gan, khdp.
Sdi true khong di vao sting sau tuy song ma vao ngay cot sau cung ben hdp thanh bo Goll va bo Burdach, hai bo nay di len tdi nhan Goll va nhan Burdach n&m d tram hanh.
Neuron 2:
Than te bao nam d nhan Goll va Burdach. Duoi gai khdp noi vdi neuron 1
Sdi true bat cheo dtfdng gitfa d hanh nao (decussation piniforme) de tdi doi thi.
Neuron 3 (doi thi - vo nao):
Than te bao nkm d nhan bung ben cua doi thi, sdi true di tdi trung tam phan tich cam giac d vo nao nam d hoi dinh len va mot so vung khac dac biet la thuy dinh.
Tren dtfdng di cua dtfdng cam giac sau cd y thtfc, bo Goll va bo Burdach nhap vao bo gai thi d doan hanh nao tren de tao thanh giai Reil gitfa.
• Dtfdng dan truyen cam giac sau khong y thtfc: la dtfdng dan truyen cam giac ve do cang cua cd, gan cd, day ch ln g khdp trong viec gitf ttf the va trong cac phan xa gitf vtfng ttf the. Dtfdng nay ttf hach gai qua tieu nao roi mdi tdi doi thi. Theo mot so" tac gia dtfdng nay ttf hach gai chi di tdi tieu nao (dtfdng gai - tieu nao) gom cd hai neuron.
Neuron 1:
Than te bao n&m trong hach gai
Duoi gai (sdi ngoai vi) tiep nhan cac cam giac d thoi cd, cac gan cd.
- Sdi true (sdi trung tfdng) tan cung d dau s in g sau tao thanh hai nhan: bong Clarke va nhan Bechterew.
■. J gitfa
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H anh n ao z ' ' I T ~ K
Hinh 2.5: Dtfdng cam giac (nong va sau) co y thtfc: 1. Bo gai - li/di - thi (quamep xam sau - cam giac sd)
Bo gai - thi (qua mep xam trudc - cam giac sau dau va nong lanh) 3. Diidng cam ac sau co y thCfc.
Hinh 2.6: Dtfdng cam giac sau khong y thtfc