Overview of Endocrine System Flashcards
Endocrine system role
communication
uses glands to release hormones in bloodstream to target specific tissues
glands + hormones
- hypothalamus
- pituitary gland
- thyroid
- parathyroid
- islets of langerhans
- adrenal
- pancrease
- ovaries
- testes
function of endocrine system
– Respiration
– Metabolism
– Reproduction
– Sensory Perception
– Movement
– Sexual development
– Growth
Endocrine System mechanism
- The regulated secretion of
hormones of endocrine cells, into the extracellular fluid. - Diffusion of the hormone to the
vasculature and its circulation
throughout the body: and - Diffusion of the hormone out of the
vascular compartment into extracellular
space and binding to a specific
receptor within cells of a target organ.
hormones are secreted by endocrine glands or cells into the blood. only target cells with specific receptors for hormone respond to the signal
Types of Hormonal Pathways
- endocrine : travels far for distant target cells
(larger amounts as it may be diluted or lost in blood) - paracrine : only activates adjacent cell
- autocrine : target sites on same cell
3 ways it acts on target cells
- Controlling rate of enzymatic reactions
- Controlling ion and molecular transport across the membrane
- Controlling gene expression and protein synthesis
modes of action
- Secreted into the blood and transport to a distant target cell;
- At the target cell, hormones must bind to target cell receptors
– known as the cellular mechanism of action - Response depends on the target receptor and signal transduction pathways
– e.g., second messengers, different receptors - Hormone actions need to be terminated
Termination of Hormone Action
– Limiting the secretion of hormone –>Through feedback loops.
– Remove or inactivate the hormone in the circulation –> Degraded by enzymes mainly found in the liver and kidneys.
– Terminating the activity of the hormone in target cells –> Receptor-hormone complex was brought into the cell by endocytosis and
the hormone is then digested in lysosomes.
negative feedback loops
Negative feedback loop – a hormone acts on one or more target organs to induce a change (either a decrease or increase) in circulating levels of a specific component, and the change in this component then inhibits secretion of the hormone.
positive feedback loops
Positive feedback loop – a hormone increases levels
of a specific component, and this component
stimulates secretion of the hormone, confers instability.
Feedback Loops
two types of negative feedback loops
- physiological response driven negative feedback
- endocrine axis-driven negative feedback
3.
Hormone Function
– Some hormones regulate the production and secretion of another hormone “a stimulatory hormones”
– These are tropic hormones
* anterior pituitary –> Thyroid stimulating hormone (TSH)
* Function: stimulates thyroid gland –> to secrete thyroid hormones
– Some hormones act directly on non-endocrine target tissues
– Non-tropic hormones e.g insulin
– Thyroid hormones increase metabolic rate of cells
Classes of Hormones and the effect of diff chemical groups
– Hormones can be grouped into three major structural classes:
– Amino acid derivatives (amines)
– Peptides
– Steroids
Hormones Can also be grouped according to solubility:
– Peptide and amines are hydrophilic
– Steroid hormones are lipophilic
These chemical groups affects:
– Hormone’s distribution
– Type of receptor it binds to
– Hormones function
Amine Hormones
– Hormones derived from modification of amino acids
– -COOH terminal, or carboxyl, group is removed
– -NH3+ or amine, group remains
– Amine hormones are synthesized from the amino acids tryptophan or tyrosine
– Derived from a single amino acid
Peptide Hormones
Derived from multiple amino acids linked to form an amino acid chain
