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解生(synaptic transmission and neural integration)

可以 | 2023-06-22 11:17:18 | 巴幣 10 | 人氣 98

enkephalin 腦啡肽

postsynapse 突觸後神經元

retina 視網膜

Electrical Synapses Identified in the retina, cortex, brainstem (breathing), and hypothalamus (neuroendocrine neurons)

主要還是chemical synapse ，electrical 比較少

effector cell:muscle and gland

bud味蕾

axodendritic樹突 synapse

axosomatic體細胞 synapse

axoaxonic軸突 synapse

大部分neurotransmitter(水溶性) 在cytosol合成；反之，脂溶性不是。

鈣離子決定neurotransmitter 的釋放

Continual binding of neurotransmitter to receptor does not occur because a number of processes quickly clear the neurotransmitter from the cleft, thereby terminating the signal.

synapse cleft突觸間隙

Synaptic Communication

1. Action potential

2. Voltage-gated Ca2+ channels open

3. Ca2+ entry triggers vesicle docking and secretion

4. Neurotransmitter diffuses and binds to receptor

5. Response terminated by removal of neurotransmitter from the synaptic cleft

The type of removal of neurotransmitter from the synaptic cleft去除bind在Synapse 的分子方法：

1. 分解Degradation by enzymes (multiple locations)

2. 回收Neurotransmitter reuptake into presynaptic terminal

3. 單純離開Diffusion out of synaptic cleft

postsynaptic potential(PSP) 突觸後電位

excitatory興奮 postsynaptic potential(EPSP)

inhibitory抑制 postsynaptic potential(IPSP)

Slow response慢反應中, 的direct coupling快反應：GPCR去open or close ion channel

Slow response慢反應中, 的second messenger system慢反應：GPCR去打開enzyme 接著產生second messenger ，second messenger open or close ion channel

可以維持較久，直到second messenger 被分解，結束transduction pathway

Na 60mV

equilibrium -70

K -94mV

Fast EPSP：又稱ionotropic receptor ，打開cation channel，因為Na在胞內少，所以Na流進細胞內比K流進出細胞外多，去極化

Slow EPSP：即Slow response慢反應中, 的second messenger system慢反應：GPCR去打開adenylate cyclase 接著產生cAMP(second messenger) ，second messenger(cAMP) 磷酸化protein kinase A，再磷酸化K+ ion channel，而關閉K ion channel(leak channel)

(ps.關閉通道代表平常是開的，就是leak channel)

Inhibitory Synapses

If K channels open:

• K+ moves out IPSP

If Cl– channels open:

• Cl– moves in IPSP

or

• Cl– stabilizes membrane potential

Cl–的Electrical force 往外；chemical force往內，兩者相反有點抵消的感覺，所以決定Cl–往哪的關鍵是有無active transport

active transport會把Cl–往外送，所以可以判斷出Cl–平常往內走

如果沒有active transport 的話，就沒有膜電位了

No active transport of chloride(沒往外), chloride at equilibrium穩定膜電位

沒有active運輸的話Cl-早就平衡→膜電位不會因為ligand-gated ion channel而改變(-70mV)

Cl-的OS：我沒有不平衡，我超平衡的

No active transport of chloride, excitatory synapse active(cation channel)：陽離子進來胞內，膜電位改變，Cl-就不平衡了，Cl- 的ligand-gated ion channel就有用了，把陽離子的用處抵消(抑制型，穩定膜電位)

看清楚題目要問有無Cl- pump

反過來說，膜電位變負的話，為了平衡，Cl- 的ligand-gated ion channel會使Cl-往外

Derived from amino acids

Catecholamines: derived from tyrosine(degraded by Monoamine oxidase ,MAO)

• Dopamine

• Norepinephrine (noradrenalin)

• Epinephrine (adrenalin)

Serotonin: derived from tryptophan

Histamine: derived from histidine

At excitatory synapses

• Aspartate

• Glutamate