1、1. Importance of Homeostasis1). It can maintain the composition of the body in fairly strict limits. ( ion concentrations, pH, blood gasses, T etc).2). It results in normal functions. 2. How is the homeostasis achieved ?This is done by several regulation mechanisms， particularly the feedback control
2、. 3. 3 patterns of regulation: Nervous Regulation （神经调节)Hormonal Regulation （体液调节）Autoregulation （自身调节）4. Nervous Regulation Characteristics: It responses fast. It acts exactly. Duration is short.5. Hormonal Regulation Characteristics : It responses slowly. It acts extensively. It lasts for long tim
3、e.6. Auto-regulation Characteristics: Amplitude of its effect issmaller than other two types. Extension of its effect is smaller than other two types.Role: only a supplement to the actionsof other two types of regulations.7. Negative feedback Significance: Reverse effect of original stimulus. Preven
4、t small changes from becoming too large. Help maintain homeostasis. This is the most common and important control mechanism in the body.8. Positive feedback Significance:amplify changes or response and enhance or reinforce action of original stimulus so as to promote an activity to finish. sometime
5、useful ,But sometime it is known as vicious cycle （恶性循环）because it can lead to instability or even death ! 9. Interaction between two types of feedbackNormally the negative feedback can overcome the positive feedback, thus a vicious circle fails to develop. 10. Feed-Forward Control SignificanceIt ma
6、kes human body to foresee and adapt the environment promptly and exactly.an adaptive control 11 . Summary of Control of Body Function Homeostasis is kept by feedback control. Negative feedback minimizes the changes， leading to stability. Positive feedback does not favor stability. But,it can promote
7、 activity, useful. Feed-forward makes human body to foresee and adapt the environment promptly. Dysfunction of homeostasis will lead to sickness or death.12. Types of transport via membrane1)Simple diffusion ( 单纯扩散 ) 2)Transport mediated by membrane proteinsFacilitated diffusion (易化扩散）Active transpo
8、rt （主动转运）Endocytosis and exocytosis （入胞、出胞）13. Lipid Bilayer Characteristics： It has fluidity Proteins flow literally in it. It has selective permeability.Functions:stand( 支架) barrier( 屏障) participation in signal transduction (PIP2)14. Membrane Proteins Characteristics : It is globular in shape. It
9、is floating in bilayer. It combines with lipid in two forms. 15. Membrane Proteins Forms and Functions:1) Integral protein （整合蛋白） channel 通道carrier 载体pump 离子泵transporter 转运体controller (G-p)2) Peripheral protein （表面蛋白）enzymes 酶 controllers16. Membrane Carbohydrates Glycoprotein (糖蛋白) Glycolipid (糖脂）F
10、unctionscharged negatively.（荷负电） function as receptor or antigen.(受体，抗原)1) Negatively charged, let the cell to repel negative objects2) Attach cells one to another3) Acts as receptor substance for binding hormone such as insulin4) Participate in immune reaction as antigen17. Major function of the ce
11、ll membrane Act as a barrier Receive information Import and export Move and expandIt acts as a selective barrier to transport substances.18. Simple Diffusion Mechanism* a physical process * driving force: Potential energy (势能) of molecules themselves. does not need ATP! 19. Factors effecting simple
12、diffusion The magnitude of concentration gradient. Driving force of diffusion. Permeability of the membrane. Lipid solubility. Molecular weight Charged Temperature. Higher temperature, faster diffusion rate. Surface area of the membrane. Microvilli increase surface area.20. Facilitated Diffusion Mec
13、hanism 1. by channel protein 2. by carrier protein Types A. Facilitated diffusion via carrier B. Facilitated diffusion via channel Facilitated Diffusion via CarrierDefinition diffusion carried out by carrier protein.Substances glucose, amino acid.Mechanism a “ferry ” or “shuttling ” process.Characte
14、ristics Down concentration gradient Chemical specificity Saturation Competitive inhibition Facilitated Diffusion via ChannelSubstances ions: Na+, K+, Ca2+, Cl-Definition diffusion carried out by channel proteinChannel, also called ion channel or channel proteins, It is one of the integral proteins w
15、ith aqueous pore , through which ions can flow in or out .gate-aqueous pathway or aqueous pore Characteristics of the channel 1) Ionic selectivity: ion channel are often selectively permeable to certain substances Na+ channel, K+ channel, Ca2+ channel, Cl- channel2) Gating channel: many of the chann
16、els can be opened or closed by gatesVoltage gated channel The molecular conformation of the gate responds to the electrical potential across the cell membrane, this type of channel is called voltage gated (or dependent) channel.Chemically gated channelSome protein channel gates are opened by the bin
17、ding of another molecule with the protein;this causes a conformational change in the protein molecule that opens or closes the gate.This type of channel is called chemically-gated (or dependent) channelMechanically gated channelSome protein channel gates may be opened by the mechanical deformation o
18、f the cell membrane. This type of channel is called mechanically-gated channel. Organ of Corti: hair cellsNo gated channel3) Functional states change: Close Resting, Non-conducting conformation(s). Gate will open when stimulated. Open or activation Activation, conducting conformation. Gate is open.
19、Ion flow in or out. InactivationInactivation, Another Non-conducting Conformation. Gate still closed even stimulated. 4) Time dependence21. the Na+/K+ ATPase Na+ pump Characteristic of -subunitSpans the cell membrane , 3 receptors for binding Na+ inside, 2 receptors for binding K+ outside. 1 site fo
20、r binding ATP inside, ATP enzyme that can converts ATP to ADP and PiCharacteristics of the Transport by Na+ pump1) Directional transport2) Coupling process3) ATP is directly required4) Electrogenic processImportance of the Na+-K+ Pump Maintain high intracellular K+ concentration gradients across the
21、 membrane. Develop and Maintain Na+ and K+ concentration gradients across the membrane Control cell volume and phase Maintain normal pH inside cell Electrogenic action influences membrane potential Provides energy for secondary active transport22. Summary of Active Transport1). It occurs uphill agai
22、nst the chemical gradient by expending ATP.2). Two forms: primary and secondary active transport.3). Primary active transport uses ATP directly. 4). Secondary active transport uses ATP indirectly 5). It can create and maintain chemical gradient.23. Transport of ions and small moleculesPassiveTranspo
23、rt : Simple diffusion Facilitated diffusion Down chemical gradient Decrease ionic gradient ATP is not needed Active Transport: Primary active transport Secondary active transportAgainst chemical gradient ,Create & maintain gradient ,Expend energy（ATP ）24. Resting Potential Property1 Stable direct cu
24、rrent2 Negative inside, positive outside. 3 Values differ in cells neuron: - 70- 90 mv skeletal muscle: -90 mv myocardium:- 40- 90 mv 25. Ionic Mechanisms of RP1) Two basic conditions for RP Na+ and Cl- are more concentrated outside the cell K+ and organic anions (organic proteins) are more concentr
25、ated inside.2) different membrane permeability for ions3) Driving force for ion transmembrane diffusion Electrochemical driving force K+ equilibrium potential Concentration differences of Na+ and K+ across the membrane exist. At rest, membrane is only permeable to K+ ion by leak channel. Resting mem
26、brane potential is closer to equilibrium potential of K+ ions.26. Factors that affect resting potential1. Difference of K+ ion concentration across the membrane2 .Permeability of the membrane to Na+ and K+.3. Action of Na+ pump27. Action Potential Property1 It is an “all or none” phenomenon. Thresho
27、ld / suprathreshold stimulus causes a complete action potential.“All or none” means that action potentials occur maximally or not at all. There is no such thing as a partial or weak action potential.2 It can be transmitted in two directions. 3 The wave form and amplitude do not reduce with its propa
28、gation 28. Types of stimulus:Threshold stimulus: The stimulus with the intensity equal to thresholdSubthreshold stimulus: The stimulus with the intensity weaker than the thresholdSuprathreshold stimulus: The stimulus with the intensity greater than the threshold.29. Initiation of an Action Potential
29、 Depolarization stage Na+ inflow Repolarization stage K+ outflow Summary Threshold stimulus cause the depolarization of membrane potential to “threshold“ level leads to opening of Na+ channels, allowing Na+ to enter the cell Interior becomes positive Next K+ channels open, K+ leaves the cell and the
30、 interior again becomes negative. The Na+ channels then close automatically followed by a period of inactivation.Process lasts about 1/1000th of a second. 30. Propagation of the Action Potential（Signal Transmission along Nerve Fiber）“ local current flow ” theory 局部电流学说 Factors that affect the propag
31、ation1) Bioelectric properties of the membrane2) Velocity and amplitude of membrane depolarization31. Ion Permeability during the AP gNa increases quickly, but then inactivation kicks in and it decreases again. gK increases more slowly, and only decreases once the voltage has decreased. The Na+ curr
32、ent is autocatalytic. An increase in V increases gNa , which increases the Na+ current, and increases V, etc. Hence, the threshold for action potential initiation is where the inward Na+ current exactly balances the outward K+ current. During subthreshold stimulus, inward Na+ current does not balanc
33、e the outward K+ current, which causes local response.32. Local response Property1 It is a graded potential (not all or none). 等级性电位 2 Its propagation is electrotonic propagation 电紧张式传导3 It can be summed (summation). 总和现象Spatial summation: 空间总和Temporal summation: 时间总和33. Local Potential Role1 It may
34、 facilitate the cell. 易化作用2 It may cause cell to excite with its summation. 经总和引起兴奋 34. difference between action potential and local potentialAction Potential Local Potential1. Caused by threshold / subthreshold suprathreshold stimulus stimulus 2. Amplitude ofdepolarization high low3. All or none Y
35、es No ( graded )4. Transmissiondistance: long short pattern: no attenuated electrotonic 5. Summation No Yes6. Significance sign/mark: Yes Norole: elicit cell function facilitate cell7. Others: refractory period Yes No 35. Threshold Stimulation and ExcitabilityThreshold Excitability Threshold Excitab
36、ilityThreshold stimulus / threshold intensity is the index for value excitability36. Four periodsAbsolute refractory periodRelative refractory periodSupranormal periodSubnormal period37. Factors that Determine the Excitability1 The difference between resting potential and threshold potential2 State
37、of ion channel38. Illustration of the Neuromuscular Junction (NMJ)(1) Nerve terminal, voltage gated Ca2+ channel mediates neurotransmitter release synaptic vesicle (Ach) quantum release of ACh The amount of ACh contained in one vesicle is called a quantum of ACh. About 10000 ACh molecules 250 vesicl
38、es ACh by an action potential (2) Space of junction, 50nm Extracellular fluid(3) End plate membrane, N2 -ACh channel End plate potential (EPP)a local depolarization at end plate membrane due to Na+ inflow ACh enzyme (ACHE, AChase) (Acetylcholinesterase)It can break down ACh in a few ms. (4) Normal m
39、embrane voltage gated Na+ channelsvoltage gated K+ channelsexcitation (action potential)39. Neuromuscular Transmission: Step by StepNerve action potential invades axon terminalDepolarization of terminal opens Ca channelsCa+2 induces fusion of vesicles with nerve terminal membrane.ACh is released and
40、 diffuses across synaptic cleft.ACh binds to its receptor on the postsynaptic membraneBinding of ACh opens channel pore that is permeable to Na+ and K+.The movement of Na+ and K+ depolarizes muscle membrane potential (EPP) ACh unbinds from its receptorso the channel closesACh is hydrolyzed by AChE i
41、nto Choline and acetateCholine is taken up into nerve terminalCholine resynthesized into ACh and repackaged into vesicle40. Steps of Transmission at the Junction Nerve action potential invades axon terminal Depolarization of terminal opens Ca2+ channel Ca2+ induces fusion of vesicles with nerve term
42、inal membrane. ACh is released and diffuses across synaptic cleft. ACh binds to its receptor on the postsynaptic membrane The movement of Na+ and K+ depolarizes muscle membrane potential (EPP) Excitation of whole normal membrane.41. Properties of Transmission a chemical process. 化学传递 ( 1:1) unidirec
43、tional 单向 It has time delay. 时间延搁 ( 20nm/0.5-1 ms) It is easily affected by drugs and some factors. 易受影响42. Sarcotubular system 肌管系统 Transverse tubule ( T 管 ）传导兴奋 Sarcoplasm reticulum (SR) JSR(Cisterna): 终池 Ca2+ pool Ca release channelLSR: Ca2+ pump 钙泵 Triad 三联管 兴奋收缩耦联43. Characteristics of Sarcomer
44、es It is made of filaments It is rich in membrane tubule system Sarcomere is the basic contractile unit44. Molecular Characteristics of FilamentsThick filament 粗肌丝 :myosin （肌凝蛋白） 2 binding sites（结合点）to ATP and to actin ATP enzymeThin filament 细肌丝 3 types of molecules actin （肌动蛋白）binding site to cros
45、s bridgetropomyosin （原肌凝蛋白）troponin （T,C,I） （肌钙蛋白 T,C,I）Attachment of cross bridge to actin a cross bridge cycling 横桥周期 45. Process of Muscle Contraction Sliding filament theory 肌丝滑行学说 a cross bridge cycling 横桥周期 Myosin head is energized. Attachment of cross bridge to actin. Power stroke causes cont
46、raction. Detachments of heads from actin. Myosin head is energized again. 46. Summary of Mechanism of Muscle Contraction Sarcomere is the basic contractile unit. Two types of proteins:Contractile proteins: Actin MyosinControl proteins: Tropomyosin Troponin Cross bridge cycle includes 4 steps. Contraction & relaxation expend ATP. 47. Two results of filament sliding 滑行结果 force or tension shortening48. How many roles does ATP play in Muscle contractionATP plays 3 roles in contractionInduce attachments and provide energy for power strok
