Endocrine system Flashcards
Regulatory functions
Metabolism Ion regulation Water balance Water balance Tissue maturation Immune system regulation Heart rate and blood pressure Control of reproductive functions Control of food intake and metabolism Control of blood glucose and other nutrients
Endocrine glands
Hypothalamus Pineal gland Pituitary gland Thyroid Thymus Adrenals Ovaries Parathyroids Pancreas Testes
Similarities with nervous system
Both associated with the brain (hypothalamus, epithalamus)
May use same chemical messenger as neurotransmitter or hormone
Two systems are cooperative
Differences between nervous system
Transport (blood, axon)
Speed of response (seconds, milliseconds)
Duration of response (minutes or days, seconds or milliseconds)
Amplitude or frequency-moderated system
General characteristics of hormones
Stability (half-life)
Communication (interaction with target cell)
Distribution (dissolve in blood plasma so distributed quickly as circulate in the blood)
Stability - general hormone characteristic
Long half-life - regulate activities that remain at a constant rate
- Usually lipid soluble and travel in plasma attached to proteins
Short half-life - water soluble hormones as proteins, epinephrine, norepinephrine
- Rapid onset and short duration
Half-life
Length of time it takes for half a dose of substance to be eliminated from circulatory system
Hormone classification
Lipid-soluble
Water-soluble
Based on chemical behaviour
Determining potential sites of action
Further subdivision in classification
Steroid hormone
Non-steroid hormones
Lipid-soluble hormones
Non polar Steroid hormones Thyroid hormones Fatty acid derivative hormones Travel in blood bound to binding proteins Small Low solubility Longer half life - slower degradation Direct effect - straight into nuclear receptor
Water-soluble hormones
Polar
Protein hormones
Peptide hormones
Most amino acid derivative hormones
Dissolve in blood
Many are large - slower diffusion through membranes
Some are small - attach to larger proteins to avoid being filtered out of the blood
Patterns of hormone secretion
Chronic hormone secretion
Acute hormone secretion
Episodic (cyclic) hormone secretion
Chronic hormone secretion
Maintenance of relatively constant concentration of hormone
Thyroid hormone
Acute hormone secretion
Epinephrine in response to stress
Episodic (cyclic) hormone secretion
Female reproductive hormones
Control of hormone secretion
Negative feedback mostly
Action of substance other than a hormone on an endocrine gland (pH or calcium in blood)
Neural control of endocrine gland
Control of secretory activity of endocrine gland by hormone or neurohormone secreted by another endocrine gland
Where nervous and endocrine systems interact
Pituitary gland and hypothalamus
Anterior pituitary produces hormones that regulate
Body functions
Secretions of other endocrine glands
Anterior pituitary gland
Releases growth hormone - influence growth of all tissues
Actions of growth hormone
Increases tissue uptake of amino acids
Synthesises new protein
Stimulates long bone growth
Posterior pituitary gland
Releases antidiuretic hormone (ADH)
Actions of ADH
Reduces water loss
Stimulated through low water conc. or low plasma volume
Osmolality increases and plasma volume decreases during exercise
Exercise above 60% max will show increased ADH to maintain plasma volume
Adrenal medulla
Epinephrine and Norepinephrine Part of sympathetic nervous system Increase: Metabolic rate Rate and force of heart contraction Blood pressure Muscle blood flow
Maintain plasma glucose concentration
Adrenal cortex
Secretes over 30 different steroid hormones - corticosteroids
Mineralocorticoids (aldosterone)
Glucocorticoids (cortisol)
Gonadocorticoids (androgens and estrogens)
Cortisol
Maintains plasma glucose during fasting and exercise
Makes amino acids available for tissue repair
Released in response to hypoglycaemia, exercise and stress
Pancreas releases
Insulin
Glucagon
Insulin
Stimulates uptake of nutrients and storage of glycogen, proteins and fats
Facilitates glucose diffusion across membranes
Lack causes glucose to be lost in urine
Secretion influenced by blood glucose levels
Glucagon
Stimulates metabolism of glucose and fatty acids
Increased secretion in response to low plasma glucose conc.
Testosterone
Anabolic (tissue building)
Androgenic (promoter of masculinity)
Responsible for muscle growth
Primary parameter to assess anabolic status of the body
Effects of testosterone
Influence protein synthesis
Mineralisation of skeleton
Growth plate maturation and function
During exercise, hormone concentrations…
Increase
Greater intensities = greater increase
Except insulin - decreases
Smaller increase in trained people
What can be useful when monitoring sports training?
Hormonal evaluation
Which hormones used to detect overtraining syndrome?
Testosterone to cortisol ratio
Reflects anabolic/catabolic status of the body
Below threshold - may indicate overtraining
Can be caused by both mental and physical stress
