tirsdag den 24. maj 2011

Nervous system

Nervous system is the system of nerve cells (neurons) as in animals and humans gather and process information and coordinate various bodily functions with each other and the outside world. Human nervous system is divided into the central nervous system (CNS) which includes the brain, the extended marrow and spinal cord and peripheral nervous system (PNS) which consists of 31 rygmarvsnerver and 12 cranial nerves.

Functionally divided nervous system in a somatic nervous system which is subject to the will control and manage functions such as movement, sensation, thought and speech, and an autonomous nervous system is unaffected by the will and regulates the internal organs functions. A neuron can be divided into different parts: the soma is the cell body, ie. it contains the nucleus, and other body or. Apart from soma expires axons which is a kind of "loop" ie. they pass electrical signals, and these are discharged into the dendrites can transmit signals to other nerve cells. Axons are covered by myelin sheaths that ensures isolation of the flow, which increases the speed of the signal. Neuronal cell's membrane is selectively permeable, so that charged ions as Na +, Cl - and K + can not diffuse through, but penetrates through the protein channels, and this transport can be both passive and active. O 2 and CO 2 can freely diffuse because they are small and neutral voltage. The rest is due to different loading concentrations of a potential across the membrane at-70mV, this is essential, since the cell if it does not have this difference in voltage, can not send or receive signals. When a sancecelle is affected by the stimuli changed the potential of axons, this response is called an action potential.

At-55mV is the so-called threshold value. If this is exceeded the signal is transmitted through the sodium channels are opened and then pouring Na + into the cell. Ie the tension in the cell increased in the positive direction up to approx. 30mV. Diffunderingen of sodium into the cell is determined by a voltage difference from the intracellular environment to the extracellular environment. When the potential when the aforementioned peak channel will be closed again (after <0.5> + Channels open, causing the membrane potential repolariseres, and falls down at-70mV. Immediately following an action potential, there will be a hyper-polarization ( "during the shoot), where membrane potential falls below-70mV, this happens because both sodium and potassium channel closure in this case made Na-K-pumen started and restores resting membrane potential, a new signal can started.