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Nerve Cells (Neuron)

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[신경세포의 가지들: 영화]

환경(자극, 정보)---> peripheral receptors---> brain (인식, 기억, 명령)---> 근육조절, 행동

신경계내에는 2 종류의 세포가 있다: 1. Nerve cells (neuron) & 2. glial cells (glia)

Nerve Cells (NEURON)
4 elements: Cell body (Soma), dendrites, axon, presynaptic terminal
1011 neurons,
10,000 different types, examples: based on the number of neurites, based on dendritic tree structure

Most neurons have four functional components in common
1. Cell body (soma): 기능:- metabolic center
구조:- triangular or pyramidal shape
- pyramidal type은 apical & basal dendrites를 보임
- dendrites와 axon이 붙어 있다

2. Dendrites: 기능: -정보의 input area

3. Axon: 구조: 0.2 - 20 um 의 직경, ramification, up to 1 m
굵은것은 myelin sheath에 둘러 쌓여 있다 (fatty insulation역할함).
Nodes of Ranvier (일정간격으로, myelin sheath가 여기에는 없다)
기능: - axon potential (AP)을 all-or-none way로 먼거리로 전달 (axon hillock에서 AP를 생성)
- axoplasmic transport
- 굵은 신경섬유가 더 빠른 전도 속도를 갖는다.

4. Presynaptic terminal:
기능: 다른 neuron의 dendrites, cell body, axon과 contact하여 synapse를 형성한다.

Axon terminals form synapses with the dendrites or somata of other neurons, When a nerve impulse arrives in the presynaptic axon terminal, neurotransmitter molecules are released from synaptic vesicles into the synaptic cleft. Neurotransmitter then binds to specific receptor proteins, causing the generation of electrical or chemical signals in the possynaptic cell.

Temporal frequency coding of information

Principles of dynamic polarization:(1 방향 정보 전달)
synaptic input--->dendrites & cell body
--->axon hillock--->axon--->presynaptic terminal

Principles of connectional specificity
1) no cytoplamic continuity between nerve cells, but synaptic cleft
2) random neuronal network이 아니다
특정 postsynaptic target cell과 synaptic contact

Neuron의 기능적 3구분:
1) sensory (afferent): 정보를 외부로 부터 받아들이는 neurons
2) motor (efferent): 근육과 glands로 command를 보냄
3) interneuron: local infoamtion processing & transfer

Reference link
axonal transport: mechanism