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Summary behavioural endocrinology (HAP-21806)
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Samenvatting behavioural endocrinologyChapter 1- the study of behavioural endocrinology (CL1)
Hormones: chemical messengers released from endocrine glands(a ductless gland from which
hormones are released into the blood system in response to specific physiological signals) that travel
through the blood system to interact with cells at some distance away and causes a biological
response.
EPO is released from kidneys and increases the circulating red blood cells, that provide oxygen to
muscles and other tissues.
Neurotransmitters: chemical messengers that communicate between nerve cells(neurons).
Cytokines: a protein chemical messenger that evokes the proliferation of other cells, especially in the
immune system.
Hormones only can influence cells that have specific receptors for that hormone. The cells that have
those receptors are the target cells. The interaction of the hormone with the receptor leads to
activation of enzymatic pathways or to effect on gene expression and protein synthesis. There are
also nongenomic effects, which are the influence of hormones on the behaviour. Individual
difference in hormone-behaviour interactions usually reflect complex influences of hormone
concentrations, patterns of hormone release, numbers and locations of hormone receptors and the
efficiency of those receptors in triggering signal transduction pathways that ultimately affect gene
transcription. So when the concentrations of the hormone are above the threshold of activation, it
does not affect differences in behaviour between individuals.
Levels of analysis
- Immediate causation: the physiological mechanisms underlying behaviour
- Development: the role of experience in individual behaviour
- Evolutionary approaches: the perspectives adopted by biologists who assume that
evolutionary processes are central to issues in ecology, systematics and behaviour
- Adaptive function: the role of any structural, physiological or behavioural process that
increases an individuals fitness to survive and reproduce as compared with other
conspecifics.
Effect of hormones on behaviour
,Chapter 2- the endocrine system (CL2)
Chemical communication
- Intracrine: intracrine substances regulate intracellular events, peptide hormones or growth
factors that bind and act inside cells
- Autocrine: autocrine substances feed back to influence the same cells that secreted them, a
signal secreted by a cell into the environment that affects the transmitting cell
- Paracrine: paracrine cells secrete chemicals that affect adjacent cells, a cell releases a
product that induces changes in a nearby cell
- Endocrine: endocrine cells secrete chemicals into the blood-stream, where they may travel
to distant target cells
- Ectocrine: ectocrine substances, such as pheromones, are released into the environment by
individuals to communicate with others
Neurohormone: a hormone that is released into the blood from a neurosecretory cell rather than
from an endocrine gland
Endocrine gland
- They are ductless
- They have rich blood supply
- Hormones are secreted into the blood stream
- Hormones can travel in the blood to virtually every cell in the body and can thus potentially
interact with any cell that has appropriate receptors
- Hormone receptors are specific binding sites, embedded in the cell membrane or located
elsewhere in the cell, that interact with a particular hormone or class of hormones
Exocrine glands: a gland that has a duct through which its product is secreted into adjacent organs or
the environment (salivary, sweat, mammary glands)
Water-soluble proteins or small peptides are stored in endocrine cells in vesicles, which contain
hormone molecules in a protein matrix. The hormones are released by the process of exocytosis. The
hormones enter the bloodstream from the extracellular space.
Steroid hormones are lipid-soluble and can move easily through the cell membrane, they are not
stored in the endocrine cells. The precursor of steroid hormones is cholesterol, which can be stored
in lipid droplets within cells. They are not water or blood soluble so they form a reversible bond with
a carrier protein while circulating in the blood.
The high affinity of hormone receptors, hormones can be very potent in their effects, despite the fact
that they are found in very dilute concentration in the blood. When the blood concentration of a
hormone is high, binding with receptors that are specific for other related hormones can occur in
sufficient numbers to cause a biological response.
When sufficient receptors are not available because of a clinical condition, or because previously high
concentrations of hormone have occupied all the receptors and new ones have yet to be made, a
biological response may not be sustained. Such a reduction in the numbers of available receptors
may lead to endocrine deficiency despite normal levels of circulating hormones.
Hypothalamus: a part of the diencephalon located just below the thalamus that is important in the
regulation of autonomic and endocrine functions
, Pituitary gland: an endocrine gland that sits below the hypothalamus and has two distinct
anatomical components, the anterior pituitary and the posterior pituitary, each derived from
different embryological origins and having different functional roles in the endocrine system.
Major endocrine structures
- Hypothalamus: control of hormone secretions
- Pineal gland: reproductive maturation, body rhythms
- Anterior pituitary: hormone secretion by thyroid, adrenal cortex and gonads; growth
- Posterior pituitary: water balance, salt balance
- Thyroid: growth and development, metabolic rate
- Adrenal cortex: salt and carbohydrate metabolism, inflammatory reactions
- Adrenal medulla: emotional arousal
- Pancreas: sugar metabolism
- Gut: digestion and appetite control
- Gonads: body development, maintenance of reproductive organs in adults
Protein and peptide hormones
- Peptide: few amino acids, protein: larger
- They are stored in endocrine cells and released to the circulatory system by exocytosis. They
are soluble in the blood.
- Hormones are removed from the blood via degradation or excretion. The metabolism is
reported in terms of its biological half-life: the amount of time required to remove half of a
hormone or other substance from the blood
- Insulin, glucagons, neurohormones of hypothalamus, tropic hormones of anterior pituitary,
inhibin, calcitonin, parathyroid hormone, gastrointestinal hormones, ghrelin, leptin,
adiponectin, posterior pituitary hormones
Hypothalamic hormones
- The hypothalamus contains collections of neuronal cell bodies(nuclei), at the base of the
brain. The hypothalamus receives information via axons.
- The neurosecretory cells are modified neurons specialized for release of chemical
messengers. Neurohormones are released by neuronal impulses analogous to the release of
neurotransmitter, but they are released into the blood vessels of the pituitary gland.
- Hypothalamic hormones are small peptides, 6 releasing hormones
Thyrotropin-releasing hormone(TRH): a tripeptide hormone secreted by the
hypothalamus that stimulates the release of thyroid-stimulating hormone(TSH) from
the anterior pituitary
Growth hormone-releasing hormone(GHRH, somatocrinin): polypeptide hormone
that is released from the arcuate nucleus of the hypothalamus that provokes the
secretion of growth hormone from the anterior pituitary
Gonadotropin-releasing hormone(GnRH): a decapeptide hormone from the
hypothalamus that regulates FSH and LH release from the anterior pituitary
Melanotropin-releasing hormone(MRH): a hexapeptide that stimulates the
secretion of melanotropin
Corticotropin-releasing hormone(CRH): a peptide hormone secreted by the
hypothalamus that stimulates the release of ACTH by the anterior pituitary
Kisspeptin
- Inhibiting hormones
Somatostatin: growth hormone-inhibiting hormone. A peptide hormone secreted from
the hypothalamus that reduces the secretion of growth hormone by the anterior
pituitary
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