16.1-16.5 Endocrine System Flashcards
Coordinates and integrates activity of the body; Works with the nervous system
Influences metabolic activities via hormones
Endocrine system
Chemical messengers secreted by cells into extracellular fluids
Travel through blood and lymph for long distances
Bind to cellular receptors
Regulate metabolic function of other cells
Hormones
Study of hormones and endocrine organs
Endocrinology
Endocrine system responses are _________ but _________ than nervous system responses
Acts at diffuse locations (anywhere blood can reach)
Slower, longer
- Reproduction
- Growth and Development
- Maintenance of electrolyte, water, nutrient balance
- Regulation of cellular metabolism and energy balance
- Mobilization of body defenses
What ES controls:
One or more cells that make and secrete a product
Gland
To secrete
-Crine
Internal, within
External
Endo-
Externally secreting
Produce non hormonal substances (ex. sweat, saliva)
Have ducts to carry secretion to membrane surface
Exocrine glands
Internally secreting; Produce hormones; Lack ducts
(Some have functions of endo and exocrine ex. Pancreas)
Endocrine glands
Chemicals that exert effects on same cells that secrete them
(not always considered part of ES)
Autocrine
Act within same tissue produced, chemicals that affect cells other than those that secrete them
(not always considered part of ES)
Paracrine hormones
First class of hormone; Amino acid derivatives, peptides, and proteins
Most hormones
Amino acid hormones
Second class of hormone; Synthesized from cholesterol
Gonadal and adrenocortical hormones
Steroid hormones
Possible third class
Eicosanoid hormones
How do hormones act?
Through second messengers/activating genes
Tissue with receptor for specific hormone
Hormones alter target cell activity
Response depends on type of target cell
Target cells
- Alters plasma membrane permeability
- Stimulates synthesis of enzymes
- Activates or deactivates enzymes
- Induces secretory activity
- Stimulates mitosis
Changes hormones make:
First action of hormones; Cannot cross the plasma membrane to enter the cell
Act on plasma membrane receptors by binding to outside
Most use a secondary messenger mechanism
Most amino acid hormones (except thyroid)
Water-soluble hormones
Second action hormones; Can cross the plasma membrane
Act on intracellular receptors inside
Receptor-hormone complex directly activates genes
Steroid and thyroid hormones
Lipid-soluble hormones
- Hormone (1st messenger) binds to receptor
- Receptor activates G protein
- G protein activates adenylate cyclase
- Adenylate cyclase converts ATP to cAMP (2nd messenger)
- cAMP activates protein kinases
Water soluble hormone mechanism
- Type of target cell
- Specific protein kinase the cell contains
- Substrates in the cell available for protein kinase to act upon
Motion by cAMP requirements:
- Steroid hormone diffuses through the plasma membrane and binds to intracellular receptor
- Receptor-hormone complex enters the nucleus
- The receptor-hormone complex binds a specific DNA region
- Binding initiates transcription of the gene to mRNA
- mRNA directs protein synthesis
Lipid-soluble mechanism
Regulated by negative feedback; Causes blood levels of hormones to vary only within narrow, desirable range
Hormone secretion –> hormone levels rise –> effect occurs on target organ –> further hormone release is inhibited
Hormone release
Endocrine gland stimuli; Changing blood levels of ions (Ca2+) and nutrients directly stimulate secretion of hormones
Response: Parathyroid hormone released, increases blood Ca2+
Humoral stimuli
Endocrine gland stimuli; Nerve fibers stimulate hormone release by action potential
Response: Adrenal medulla cells secrete epinephrine and norepinephrine
Neural stimuli
Endocrine gland stimuli; Hormones secreted by endocrine organs stimulate other endocrine organs to release their hormones; Chain reaction
Hormonal stimuli
Hormones from final target organs inhibit release of anterior pituitary gland
Hypothalamic-pituitary-target endocrine feedback loop
NS makes adjustments to hormone levels when needed
NS can override normal endocrine controls and maintain homeostasis
Nervous system modulation
- Blood level of hormone
- Relative number of receptors on/in target cell
- Affinity of binding between receptor and hormone
Target cell activation:
Target cells create more receptors in response to low hormone levels
Up-regulation
Target cells lose receptors in response to high hormone levels
Down-regulation
Concentration of circulating hormone in blood reflects:
- Rate of release of hormone
- Speed at which the hormone is inactivated
Hormones are either bound to a protein carrier or float free?
True
Kidneys
Liver
Degrading enzymes (target cells)
Things that remove hormones from blood:
Time required for level of hormone in blood level to decrease by half
Half life
hormone fact sheet
onset and duration
Multiple hormones may act on same target at same time?
True
1st hormone interaction; When one hormone cannot exert its effects without another hormone being present
Permissiveness
2nd hormone interaction; When more than one hormone produces same effects on target cell, causing amplification of effects
Synergism
3rd hormone interaction; When hormone opposes the action of another hormone
Antagonism
