Neurosiences – The neuroendocrine system
2 homeostatic control centers
1. Nervous system
2. Endocrine system
Both specialise in long distance communication of cells
Intracellular communication;
• Direct; exchange ions and molecules
across gap junctions
• Paracrine; chemicals released into
extracellular fluid. Tell neighbours what
they are doing
• Autocrine; chemical released into
extracellular fluid. Affect same cell that
secrete them
• Endocrine; hormones transported through bloodstream each hormone has
target cell; specific cell in other tissue that have receptors needed to bind the
hormone
• Synaptic; across synapses. Neurotransmitter released, very clos to target cell
that have receptor
Nervous system;
• Very fast
• Target individual postsynaptic cells
• Neuron specific
• neurotransmitters
Endocrine system;
• Slow
• Target population of cells
• Endocrine cell & neurons
• Hormones & neuropeptides; signalling molecules that
bind to selective receptors
o Water-soluble (hydrophilic); cannot cross the
blood-brain-barrier (filter between bloodstream
and central nervous system)
▪ Amines; modified amino acids
▪ (neuro) peptides; short peptides
▪ Eicosanoids; derivatives of arachidonic acid
o Lipid-soluble (hydrophobic); can cross the blood-brain-barrier (filter
between bloodstream and central nervous system). So, steroid
hormones affect brain function!
▪ Steroid hormones; derivatives of
cholesterol
• Cortisol; secreted by adrenal gland
important for stress response
• 5-alfa-dihydrotestosteron
• 17-beta-estradiol
▪ Thyroid hormone; tyrosine conjugated with iodine (T3, T4)
, Transport of hormones;
• Water-soluble (hydrophilic)
They are stored in vesicles and are secreted by
exocytosis. Circulate in free form in blood
Have extracellular receptor on plasma
membrane, are often metabotropic receptors that
activates second messenger cascades
• Lipid-soluble (hydrophobic)
They are secreted by diffusion. Attach to transport-
proteins in the blood that are synthesized by the
liver
Have intracellular receptor, hormones diffuse
through plasma membrane – bind to receptor –
hormone-receptor to nucleus – bind to DNA –
gene activation – new protein is formed – alters
cell’s activity (activate transcription factors to modulate gene transcription)
Feedback mechanisms;
1. Autocrine feedback; inhibit endocrine tissue from
which they are released
2. Target cell feedback; inhibit endocrine tissue from
different tissues
The feedback mechanisms help to maintain homeostasis.
Endocrine functions of the brain;
• Hypothalamus
o Located just above the optic chiasm and the
pituitary gland
o Receive sensory input; visceral and somatic
sensory pathways, chemosensory and humoral
signals
o Receive contextual information; cerebral cortex,
amygdala, hippocampal formation
o Maintain homeostasis: blood pressure,
metabolism, body temperature
o Regulates; stress response, mating behaviour
• Pituitary gland
o Posterior; neurons transported via axons to
capillaries in posterior pituitary gland
Especially neuronal tissue
▪ Oxytocin; go to mammary gland and
uterus; regulate reproductive activities
▪ Vasopressin (ADH); retain water and
decrease urination. Blood pressure drop
because of volume raise
o Anterior
Secrete hormones via axons into bloodstream.
Especially blood
▪ Growth hormone
2 homeostatic control centers
1. Nervous system
2. Endocrine system
Both specialise in long distance communication of cells
Intracellular communication;
• Direct; exchange ions and molecules
across gap junctions
• Paracrine; chemicals released into
extracellular fluid. Tell neighbours what
they are doing
• Autocrine; chemical released into
extracellular fluid. Affect same cell that
secrete them
• Endocrine; hormones transported through bloodstream each hormone has
target cell; specific cell in other tissue that have receptors needed to bind the
hormone
• Synaptic; across synapses. Neurotransmitter released, very clos to target cell
that have receptor
Nervous system;
• Very fast
• Target individual postsynaptic cells
• Neuron specific
• neurotransmitters
Endocrine system;
• Slow
• Target population of cells
• Endocrine cell & neurons
• Hormones & neuropeptides; signalling molecules that
bind to selective receptors
o Water-soluble (hydrophilic); cannot cross the
blood-brain-barrier (filter between bloodstream
and central nervous system)
▪ Amines; modified amino acids
▪ (neuro) peptides; short peptides
▪ Eicosanoids; derivatives of arachidonic acid
o Lipid-soluble (hydrophobic); can cross the blood-brain-barrier (filter
between bloodstream and central nervous system). So, steroid
hormones affect brain function!
▪ Steroid hormones; derivatives of
cholesterol
• Cortisol; secreted by adrenal gland
important for stress response
• 5-alfa-dihydrotestosteron
• 17-beta-estradiol
▪ Thyroid hormone; tyrosine conjugated with iodine (T3, T4)
, Transport of hormones;
• Water-soluble (hydrophilic)
They are stored in vesicles and are secreted by
exocytosis. Circulate in free form in blood
Have extracellular receptor on plasma
membrane, are often metabotropic receptors that
activates second messenger cascades
• Lipid-soluble (hydrophobic)
They are secreted by diffusion. Attach to transport-
proteins in the blood that are synthesized by the
liver
Have intracellular receptor, hormones diffuse
through plasma membrane – bind to receptor –
hormone-receptor to nucleus – bind to DNA –
gene activation – new protein is formed – alters
cell’s activity (activate transcription factors to modulate gene transcription)
Feedback mechanisms;
1. Autocrine feedback; inhibit endocrine tissue from
which they are released
2. Target cell feedback; inhibit endocrine tissue from
different tissues
The feedback mechanisms help to maintain homeostasis.
Endocrine functions of the brain;
• Hypothalamus
o Located just above the optic chiasm and the
pituitary gland
o Receive sensory input; visceral and somatic
sensory pathways, chemosensory and humoral
signals
o Receive contextual information; cerebral cortex,
amygdala, hippocampal formation
o Maintain homeostasis: blood pressure,
metabolism, body temperature
o Regulates; stress response, mating behaviour
• Pituitary gland
o Posterior; neurons transported via axons to
capillaries in posterior pituitary gland
Especially neuronal tissue
▪ Oxytocin; go to mammary gland and
uterus; regulate reproductive activities
▪ Vasopressin (ADH); retain water and
decrease urination. Blood pressure drop
because of volume raise
o Anterior
Secrete hormones via axons into bloodstream.
Especially blood
▪ Growth hormone
