Chapter 16- The Endocrine System Flashcards
Hormones
Long distance (not affecting the cells that are in the same tissue they are inchemical messengers that cause a change in metabolic activity of a cell
long lasting
hormone control
Reproduction
Growth and development
Immune system activation
Maintenance of various blood components (glucose, electrolytes, water, etc.)
autocrines and paractines
short-sdistance chemical messengers
more localized infections
autocrine
a chemical message that affects the same cell that produces the message
paracrine
a chemical message that is produced by one cell but affects a different cell
same tissue but different cell
Major classifications of hormones
- amino acid-based hormones- water soluble transports a protein from point a to point b
- steroid hormones- synthesized from cholesterol
lipid soluble
the only steroid hormones in the body are gonadal hormones and adrenocortical
Hormone Actions
- Altering plasma membrane permeability or membrane potential (epinephrine)
- stimulates the synthesis of enzymes/proteins in the cell
- Activates and deactivates enzymes
- induces secratory activity
- stimulates mitosis
Target cells
affected by hormones that have the appropriate receptor
2 mechanisms of hormones
- secondary messenger system through g protein (extremely efficient)
- intracellular system- hormone enters cell and binds to intracellular receptors and DNA transcription occurs
stimulus mechanisms
- humoral stimuli- change blood levels of critical ion and nutritns
- neural stimuli- nerve fibers stimulate hormone release
- hormonal stimuli- hormone released in response to other hormones
hormone concentration in blood depends on
- how fast its released from the organ
- how fast it is broken down (hormones are removed by kidneys and liver) (water soluble hormones have shortest half life)
Hormone release
negative feedback mechanism
activation of a cell depends on
- blood levels of a hormone (more blood = more binding)
- number of receptors for specific hormone on/in a cell (more receptors = more binding)
- affinity of receptor to the hormone (easier binding, the higher the effect)
up-regulation
increase receptor number in response to low hormone levels
down-regulation
decrease receptor number in response to high hormone levels (safety backup mechanism)
Permissiveness
one horone cannot have funn effect without binding of a second specific hormone
synergism
2 or more horones with similar effects bind to target cell and amplification occurs
antagoism
one hormone opposes the effect of another and they will compete
Pituitary gland
anterior and posterior pituitary
anterior pituitary
manufacturers and releases several dfifferent hormones
posterior pituitary
composed mostly of neural tissue and nerve fibers
release of hormones controlled by pituitary
- action potentials from hypothalamus causes hormone release (posterior pituitary)
- hypothalamic hormones released into hypophyseal portal system (anterior pituitary)
hypophyseal portal system
stimulate or inhibit hormone release
Oxytocin
stimulant for uterine contraction, milk ejection, “cuddle hormone”
Neurotransmitter in brain → promotes nurturing, couple bonding, trust, affectionate behavior
Stretching of cervix during childbirth sends afferent impulses to hypothalamus → stimulates posterior pituitary to release oxytocin
Antidiuretic hormone
inhibits formation of urine by increasing return of water to blood supply by kidneys
ADH will influence how much water leaves the body through urine
six anterior pituirtary hormones
- growth hormone
- Thyroid-Stimulating Hormone (TSH) (tropin)
- Adrenocorticotropic Hormone (ACTH) (tropin)
4 and 5. Gonadotropins - 4) Follicle-stimulating hormone (FSH) and 5) Luteinizing hormone (LH) (both tropin) - Prolactin (PRL)
Thyroid Hormone
major metabolic hormone that affects every cell body
1. increases metabolic rate and body heat production
2. regulates tissue growth.development
3. maintains blood pressure
parathyroid hormone (PTH)
contributes to calcium homeostasis in body
Falling blood Ca2+ levels stimulate PTH release by:
1) Stimulating osteoclasts to increase bone degradation
2) Enhancing Ca2+ reabsorption by kidneys
3) Activating vitamin D → increases absorption of Ca2+ from digestive system
Adrenal glands
stress response, electrolyte balance
adrenal cortex
outmost region that produces cortiocosteroids
Three subdivisions of adrenal cortex
A) Zona glomerulosa: produce mineralcorticoids
B) Zona fasciculata: produce glucocorticoids
C) Zona reticularis: produce gonadocorticoids
Mineralcorticoids
regulate electrolyte concentration in ECF → especially Na+ and K+
Importance:
Na+ influences water movement → can affect blood volume and blood pressure
K+ determines resting membrane potential → imbalance affects responsiveness of neurons
Glucocorticoids
influence energy metabolism of cells, provide resistance to stressors
Specific types: cortisol, cortisone, corticosterone
Cortisol release stimulated by ACTH
Release usually secretory bursts → increases when we first wake up & during eating
Stress affects cortisol release → CNS overrides negative feedback mechanism & more cortisol released
Effects of glucocorticoids:
Mobilizes body stores to create more glucose
Provokes sympathetic nervous system → vasoconstriction
Excessive release causes:
Depressed cartilage & bone formation
Inhibits inflammation
Depresses immune system
Disrupts normal cardiovascular, neural, gastrointestinal functions
Gonadocortioids
small amounts of androgens released by adrenal cortex
Some converted to testosterone, others converted to estrogen
Amount produced by adrenal cortex is very small compared to what is produced by gonads
effects of gonadocorotioids
Contribute to axillary and pubic hair development
Females → contributes to sex drive, produce estrogens post-menopause
Menopause- ovaries stop producing androgen and instead produce estrogen
adtenal medulla
innermost region of adrenal gland
Synthesize epinephrine & norepinephrine
Unequal amounts stored & released in adrenal medulla
80% epinephrine: greater influence on metabolic activity & is a dilator of airways in lungs
20% norepinephrine: greater influence on blood vessel diameter
pineal gland
secretes melatonin
Effect: regulates night-day cycles, sleeping schedule
Release controlled indirectly by visual pathways → intensity & duration of sunlight
The pancreas
Hormones produced in pancreatic islets
Function: controls blood sugar levels
Produces & secretes 2 hormones:
1. glucagon
2. insulin
Glucagon
produced by alpha cells
Hyperglycemic effect
Effects: Stimulates liver to break down glycogen, convert non-carbohydrate molecules to glucose, release glucose from liver cells
Release controlled by dropping blood glucose levels
Insulin
produced by beta cells
Hypoglycemic effect
Effects: Increases glucose uptake by body cells, inhibits glycogen breakdown, inhibits conversion of non-carbohydrate molecules to glucose
Release controlled by:
Elevated blood glucose
Rising blood levels of amino acids & fats
Acetylcholine release from parasympathetic
Any hyperglycemic hormone
Diabetes mellitus
inadequate (or absent) release of insulin by pancreas
Effect: consistently high blood sugar levels
Normal range (fasting): 99 mg glucose/dl blood (or lower)
Diabetes (fasting): 126+ mg glucose/dl blood
Type 1
autoimmune condition → insulin is not produced by the pancreas
Several genes contribute to condition
Treatment: insulin shots before meals or continuous fusion pumps
If left untreated → development of vascular & neural problems
Type 2
insulin resistance → insulin released, but cells do not respond
Correlated more with lifestyle
Some genetic component, but almost all are overweight and underactive
Similar complications to type 1 diabetes if not managed/treated
Can be managed with diet and exercise
Gonads
Females: ovaries produce estrogens & progesterone
Estrogen function: maturation of reproductive organs, appearance of secondary sex characteristics
Progesterone function: breast development, cyclic changes in uterine mucosa
Males: testes produce testosterone
Function: maturation and maintenance of reproductive organs, appearance of secondary sex characteristics, sex drive, normal sperm production
Placenta
Temporary endocrine organ
Produces estrogens, progesterone, human chorionic gonadotropin (hCG)
Function: maintains pregnancy
