Capillary

2012-10-26T11:15:31Z

110027450: Created page with "The capillaries are the smallest vessels in the body, these vessels are where the materials ion the blood stream exchange with the interstitial fluid.<ref>Human Physiology, 5th e..."

The capillaries are the smallest vessels in the body, these vessels are where the materials ion the blood stream exchange with the interstitial fluid.<ref>Human Physiology, 5th edition, pg 469, Dee Unglaub et al</ref> Once the oxygenated blood leaves the heart it is pumped down a series of smaller and smaller vessels until it reaches the capillery network. It is here where oxygen transfer takes place and also the exchange of other materials. The capilaries are mostly found at the surface of tissues, but are also responsible for the oxygen supply of organs, and are therefore found in them. One example is the capillaries that run along the outside of the heart providing it with its oxygen supply. <ref>Human Physiology, 5th edition, pg 471</ref> 

As the capillaries are responsible for the exchange of Oxygen, CO2 and other materials the capillary walls must be very thin to provide a suitable exchange interface, it is therefore only made up of a single layer of endothelium cells and this allows easy exchange. <ref>Human Physiology, 5th edition, pg 514, Dee Unglaub et. al.</ref>

Dendrites

2011-11-26T22:44:16Z

110027450: Created page with " A Dendrite is an extension of the cell body from a neuronal cell, this the place in a neuronal cell where it receives communication from other neuronal cells and where it i..."

A Dendrite is an extension of the cell body from a neuronal cell, this the place in a neuronal cell where it receives communication from other neuronal cells and where it is determined whether or not an action potential is transmitted down the axon.<ref>Alberts et al., 5th edition, G:10</ref> In a dendrite when neurotransmitters cross the synaptic cleft and bind to receptors on the membrane a signal is transferred, unlike in the axon of a neuronal cell the signal is not an action and in fact a [[Graded_potentials|graded potential]]. The graded potential can be of varying strengths and depending on the strength of the graded potential when it reaches the axon hillock if the graded potentials exceed the threshold level then an action potential is sent down the axon. There are two types of graded potentials, one is excitorary and the other is inhibitory. The excitorary potential is known as an EPSP, this is initiated by Na+ ion channel opening and the entering of Na+ ions into the cell depolarising the membrane potential, the inhibitory potential, the IPSP is initiated by the Cl- ion channel opening and this hyperpolarises the membrane potential and will as a result cancel out an EPSP and inhibit a action potential being produced

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Capillary

Dendrites