Neurosciences 7+24
HC 10
Chapter 7
There are two systems in place that are specialized in long distance communication of cells,
both the nervous and endocrine system. The former signals via synaptic transmission and
projecting axons, while the endocrine system secretes hormones for paracrine and
endocrine transmission – this is signaling to adjacent cells or via the bloodstream,
respectively. The only difference here is that the former is very fast, targets individual cells,
uses neurotransmitters and is neuron specific. The latter is slower, targets populations of
cells and uses hormones/neuropeptides. These last two are signaling molecules that bind to
selective receptors.
The neuro-endocrine system is primarily formed by a tight connection between the
hypothalamus and pituitary gland beneath. These formed the endocrine activity of the
brain, hence the neuro-endocrine system. It functions in releasing hormones, under
regulatory basis and for homeostatic purposes. The hormones released, or the ones the
pituitary releases but which invoke a release of the final hormone product from the target
organ, are either hydrophilic or -phobic. Hydrophilic hormones are the amines,
neuropeptides and eicosanoids, whereas the hydrophobic ones are the steroid and thyroid
hormones. Hydrophilic hormones can travel freely through the blood, in which they are
released following exocytosis from vesicles – like neurotransmitters. Hydrophobic hormones
on the other hand, reach the blood simply by diffusion through the plasma membrane. Once
in the blood, there are carrier proteins in place to aid in the transport of the hormones. Also
with regards to the receptors, do the two hormone types differ. Hydrophilic hormones bind
to receptors on the cell membrane (primarily metabotropic receptors), while hydrophobic
hormones bind to receptors intracellularly, whereby often transcription factors are activated
and thus gene transcription is influenced. Along these lines, you can postulate that
hydrophilic hormones act on the rather short-term but fast, while hydrophobic hormones
act on the long-term with a somewhat slower response.
Commonalities between the two include the extent of amplification both experience and
the feedback loops on the tissue organ or e.g. the hypothalamus. Conventionally, the
hormone axis is as follows: endocrine tissue hormone 1 hormone 2, with hormone 1,
2 and the endocrine tissue itself (autocrine) negatively providing feedback to the production
by the endocrine tissue. This, to maintain homeostasis.
The blood brain barrier in place privileges the CNS by protecting it from pathogenic dangers,
but also prevent hydrophilic hormones from acting. Only hydrophobic hormones can pass
the barrier, which exists of tight junctions between endothelial cells, a basal lamina and
surrounding astrocytes. There is actually no blockage of lipophilic compounds, meaning one
such hormone has a widespread effect on the brain – which is flooded with receptors.
The brain, as an endocrine gland, has two major players; the hypothalamus and the
pituitary, which are actually in close connection. The hypothalamus, which lies superior to
the pituitary and optic chiasm, receives sensory and contextual input, integrating this to
confer a homeostatic response by evoking a response in the pituitary. On top of
homeostatic functions, the hypothalamus also working in mating behavior and the stress
response. The pituitary can be subdivided into two parts, namely the posterior and anterior
pituitary. The former directly releases the hormones it receives from the hypothalamus,
HC 10
Chapter 7
There are two systems in place that are specialized in long distance communication of cells,
both the nervous and endocrine system. The former signals via synaptic transmission and
projecting axons, while the endocrine system secretes hormones for paracrine and
endocrine transmission – this is signaling to adjacent cells or via the bloodstream,
respectively. The only difference here is that the former is very fast, targets individual cells,
uses neurotransmitters and is neuron specific. The latter is slower, targets populations of
cells and uses hormones/neuropeptides. These last two are signaling molecules that bind to
selective receptors.
The neuro-endocrine system is primarily formed by a tight connection between the
hypothalamus and pituitary gland beneath. These formed the endocrine activity of the
brain, hence the neuro-endocrine system. It functions in releasing hormones, under
regulatory basis and for homeostatic purposes. The hormones released, or the ones the
pituitary releases but which invoke a release of the final hormone product from the target
organ, are either hydrophilic or -phobic. Hydrophilic hormones are the amines,
neuropeptides and eicosanoids, whereas the hydrophobic ones are the steroid and thyroid
hormones. Hydrophilic hormones can travel freely through the blood, in which they are
released following exocytosis from vesicles – like neurotransmitters. Hydrophobic hormones
on the other hand, reach the blood simply by diffusion through the plasma membrane. Once
in the blood, there are carrier proteins in place to aid in the transport of the hormones. Also
with regards to the receptors, do the two hormone types differ. Hydrophilic hormones bind
to receptors on the cell membrane (primarily metabotropic receptors), while hydrophobic
hormones bind to receptors intracellularly, whereby often transcription factors are activated
and thus gene transcription is influenced. Along these lines, you can postulate that
hydrophilic hormones act on the rather short-term but fast, while hydrophobic hormones
act on the long-term with a somewhat slower response.
Commonalities between the two include the extent of amplification both experience and
the feedback loops on the tissue organ or e.g. the hypothalamus. Conventionally, the
hormone axis is as follows: endocrine tissue hormone 1 hormone 2, with hormone 1,
2 and the endocrine tissue itself (autocrine) negatively providing feedback to the production
by the endocrine tissue. This, to maintain homeostasis.
The blood brain barrier in place privileges the CNS by protecting it from pathogenic dangers,
but also prevent hydrophilic hormones from acting. Only hydrophobic hormones can pass
the barrier, which exists of tight junctions between endothelial cells, a basal lamina and
surrounding astrocytes. There is actually no blockage of lipophilic compounds, meaning one
such hormone has a widespread effect on the brain – which is flooded with receptors.
The brain, as an endocrine gland, has two major players; the hypothalamus and the
pituitary, which are actually in close connection. The hypothalamus, which lies superior to
the pituitary and optic chiasm, receives sensory and contextual input, integrating this to
confer a homeostatic response by evoking a response in the pituitary. On top of
homeostatic functions, the hypothalamus also working in mating behavior and the stress
response. The pituitary can be subdivided into two parts, namely the posterior and anterior
pituitary. The former directly releases the hormones it receives from the hypothalamus,
