1. Tinh tiT dong cua tim
Tim bi eat rdi khdi eo the van cd kha nang eo dan nhip nhang neu duge cung cap dii chai dinh dudng, dxi va nhiet do thfch hgp. Kha nang co dan tu ddng theo chu ki ciia tim dugc ggi la tinh tu ddng cua tim.
Tim CO dan tu ddng theo chu ki la do he din truyin tim (hinh 19.1). He dan truyin tim la tap hgp sgi dac biet ed trong thanh tim, bao gdm : niit xoang nhi, niit nhi that, bd His va mang Pudekin.
Niit xoang nhi ed kha nang tu phat xung dien. Cii sau mdt khoang thdi gian nhai dinh, mit xoang nhi lai phat xung dien. Xung didn lan ra khap co tam nhi lam tam nhi eo, sau dd lan den niit nhi thai, ddn bd His rdi theo mang Pudekin lan ra khap eo tam thai lam tam thai co.
Niit xoang nht
Nut nhT that
Mang Pudekin !
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Hinh 19.1. He dan truyin tim 2. Chu ki hoat dong cua tim
Tim CO dan nhip nhang theo chu ki. Mdi chu ki boat ddng ciia tim (chu ki tim) bat dau tir pha co tam nhi, sau dd la pha eo tam that va cudi ciing la pha dan chung. T i l p dd lai bat dau mdt chu ki tim mdi bang pha co tam n h i . . . Tam nhi eo day mau tir tam nhi xudng tam that.
Tam that eo day mau vao ddng maeh chii va ddng maeh phdi. 0 ngudi trudng thanh, mdi chu ki t i m k e o dai khoang 0,8 giay (hinh 19.2).
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Trong dd, tam nhi eo 0,1 giay, tam that co 0,3 giay, thdi gian dan chung la 0,4 giay. Vl mdi chu ki tim keo dai 0,8 giay ndn trong mdt phiit ed khoang 75 chu ki tim, nghia la nhip tim la 75 lan/phiit.
0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8s 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8s Tam nhT
Tam that
0,1s 0,3 s 0,4 s 0,8 s
Tam nhT co Tam that co Dan chung Chu ki tim
Hinh 19.2. Chu ki boat dgng eua tim Nhip tim ciia cac loai ddng vat la khae nhau (bang 19.1).
Bang 19.1. Nhip tim cua thu Dong vat
Vol Trau
Bd Lgn Meo Chudt
Nhip tim/ phut 25 - 40 4 0 - 5 0 5 0 - 7 0 6 0 - 9 0 110-130 720 - 780
• Nghien ciru bang 19.1 va tra Idi eae cau hoi dudi day : - Cho biet moi lien quan gii/a nhip tim vdi khoi lugng ea thS.
- Tai sao ed sU khae nhau ve nhip tim a cac loai ddng vat ? IV - HOAT D O N G C U A HE M A C H
1. Cdu true cua he mach
He mach bao gdm he thdng ddng mach, he thdng mao mach va he thdng tinh maeh.
He thdng ddng maeh bat dau tii ddng mach chu, tiep din la cae ddng maeh co dudng kfnh nhd dan va cudi cung la tieu ddng maeh. He thdng tinh mach bat dau tir tilu tinh mach, tilp din la cac tinh mach cd dudng kinh Idn dan va cudi ciing la tinh maeh chii. He thdng mao mach ndi giiia tilu ddng maeh vdi tilu tinh maeh.
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2. Huyet dp
Tim CO bdp ddy mau vao ddng mach, ddng thdi cung tao ndn mdt ap luc tac dung Idn thanh mach va ddy mau chay trong hd mach. Ap luc mau tac dung Idn thanh maeh dugc ggi la huylt ap.
Do tim bom mau vao ddng mach tiing dgt ndn tao ra huyet dp tam thu (ling vdi liic tim eo) va huylt dp tam truong (ling vdi liic tim dan). 6 ngudi, huyet dp tam thu bang khoang 110 - 120mmHg va huyet dp tam truong bang khoang 70 - 80mmHg.
Ngudi Viet Nam trudng thanh cd huylt dp tam thu khoang UOmmHg va huyet dp tam truong khoang 70mmHg. Huyet dp ddng maeh eua ngudi duge do d canh tay ; huylt dp eua trau, bd, ngua duge do d dudi.
Tat ca nhiing tac nhan lam thay ddi luc co tim, nhip tim, khdi lugng mau, dd qudnh cua mdu, su dan bdi cua maeh mdu deu cd thi lam thay ddi huyet dp.
• - Tai sao tim dap nhanh va manh lam huyet ap tang, tim dap cham va yeu lam huyet ap giam ?
- Tai sao khi ca thS bi mat mau thi huyet ap giam ?
Trong sudt ehilu dai eiia he maeh (tii ddng maeh ddn mao maeh va tinh mach) ed su bien ddng vl huylt dp (hinh 19.3 va bangl9.2).
mmHg 120
100
80
Huyet ap tam trUdng 60 •
40 -
20 •
Huyet ap tam thu
/
Ddng mach Tieuddngmach Maomach Tieuffnhmach TTnhmach
Hinh 19.3. Bien dgng huyet ap trong he mach
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Bang 19.2. Biin dgng huyit dp trong he mqch ciia ngudi trudng thdnh
Loai mach Ddng maeh chu
Ddng maeh Idn
Tilu
ddng maeh Mao mach Tilu Tinh mach tinh maeh chii Huyet ap
(mmHg) 120 - 140 1 1 0 - 1 2 5 4 0 - 6 0 20-40 1 0 - 1 5 ô 0
• Nghien ciru hinh 19.3 va bang 19.2, sau dd md ta su bien ddng eiia huyet ap trong he maeh va giai thich tai sao cd su bien dgng dd (dua vao ma sat eiia dich Idng chay trong ong).
3. Van tdc mdu
Van tdc mdu la tdc do mdu chay trong mdt giay. Vf du, tdc do mau chay trong ddng mach chu bang khoang 500mm/s, trong mao mach bang khoang 0,5mm/s, trong tinh mach chu bang khoang 200mm/s.
Van tdc mdu trong cdc doan mach eiia he maeh lidn quan chii ylu den tdng tiet dien ciia maeh va chenh lech huylt dp giira hai ddu doan maeh.
• Quan sat hinh 19.4, sau dd tra Idi cac cau hoi sau : - Van toe mau bien ddng nhu the nao trong he maeh ? - So sanh tong tiet dien ciia cac loai mach.
- Cho bie't moi lien quan giCra van toe mau va tong tiet dien mach.
Ddng mach Mao mach Tinh mach
Hinh 19.4. Bien dgng ciia van toe mau trong he mach a) Van tdc mau ; b) Tong tiet dien maeh.
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O ngudi, tilt dien eiia ddng mach chu bang khoang 5 - 6em , tdc do mau o day bang khoang 500mm/s. Tdng tilt dien cua mao maeh bang khoang dOOOem nen tdc do mau giam ehi cdn khoang 0,5mm/s.
- Khd ndng co ddn tu dgng theo chu ki ciia tim ggi la tinh tU ddng ] cua tim.
- Khd ndng co ddn tu ddng theo cku ki cua tim la do he ddn truyin tim. He ddn truyin tim bao gdm : nut xoang nhi, nut nhi thdt, bd His vd mqng Pudekin.
- Tim hoqt dgng theo chu ki. Mdi chu ki tim bat ddu tdpha co tdm nhi, sau dd la pha co tdm that vd cudi cung la pha ddn chung.
- Huyit dp la dp luc mdu tdc dung len thdnh mqch. Huyit dp giam I ddn trong he mqch.
- Van tdc mdu trong he mqch lien quan chii yiu din tdng tiit dien ciia mqch vd chenh lech huyit dp giua hai ddu doqn mqch.
Cau hoi va bai tap
1. Tai sao tim tach rdi khdi co the vin cd kha nang co dan nhjp nhang ? 2. Ve va chu thi'ch he dan truyen tim.
3. Tai sao huyet ap lai giam dan trong he mach ? 4. Giai thich sU bien ddi van tdc mau trong he mach.
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