UNIT 1 - ENDOCRINE SYSTEM Flashcards
Gland
Cells or organs that produce secretions for use in the body. Secretions are produced by specialized cells in glands from various components in blood
Exocrine gland characteristics (4)
- Secretes substances through tubes/ducts
- Ducts may be simple tubes or complex tree like ducts
- Diverse (eg. Salivary gland, mammary gland, sweat gland, pancreas, stomach, prostate)
- Varied secretions (eg. Saliva, milk, sweat, digestive enzymes, fluids to accompany gametes)
Endocrine gland
Ductless glands that secretes hormones into interstitial fluid, then blood and lymph to the target cells via receptors for a response
Functions of hormones (7)
- Stimulate secretion of exocrine glands
- Stimulate endocrine glands
- Affect growth, development, personality
- Regulate metabolism of cells
- Regulate contraction of muscle tissues
- Regulate nervous stimulation
- Control reproductive processes
Purpose of regulation of hormone secretion
Hormone levels must be tightly controlled to prevent abnormal hormone levels and a potential disease state
How is regulation of hormone secretion controlled
It is controlled by balancing hormone production and degradation. Feedback loops also govern the initiation and maintenance of hormone secretion in response to stimuli
3 categories of stimuli for hormonal stimuli:
- Humoral
- Hormonal
- Neural
Humoral stimulus
Hormone is released in response to a change in the blood or other body fluids
Hormonal stimulus
Hormone is released in response to the action of another hormone
Neural stimulus
Hormone is released by direct stimulus from neuron
Hormones
Chemical messengers that regulate activities of various body organs. It is released in one part of the body and regulates metabolic activities of cells in another part of the body
Hormone receptor
A protein located within cell membrane where the message from the hormone is received
Intracellular hormone receptors
Located inside the cell and hormones bind to DNA within nucleus to trigger protein synthesis. Hormones that bind to this receptor must be able to cross the cell membrane (lipid-soluble)
Cell membrane hormone receptors
Located on the cell membrane and hydrophilic or water soluble hormones are unable to diffuse through the lipid bilayer of membrane and must pass on their message to a receptor located at the surface of cell
Categories of hormones (4)
- Amine hormone
- Peptide hormone
- Protein hormone
- Steroid hormone
Amine hormone
Amino acids with modified groups (eg. Norepinephrine, epinephrine, thyroid hormones)
Peptide hormone
Short chains of linked amino acids (eg. Oxytocin)
Protein hormone
Long chains of linked amino acids (eg. Human growth hormone)
Steroid hormone
Derived from lipid cholesterol (eg. Testosterone, progesterone)
Nervous system
Rapid communication, short-term effect, neurotransmitters released and act at nearby synapse
Endocrine system
Communication takes longer since hormones travel through bloodstream, longer lasting effects, hormones released from place distant from where effects occur
Nervous system & endocrine system signals
Nervous system is by electrical impulses (action potentials), endocrine system is by chemical impulses (hormones)
Nervous system & endocrine system pathways
Nervous system is by the transmission by neurons, endocrine system is transported by blood
Nervous system & endocrine system speed of information
Nervous system is fast, endocrine system is slow
Nervous system & endocrine system duration of effect
Nervous system is short lived, endocrine system can be short or long lived
Nervous system & endocrine system type of action and response
Nervous system can be voluntary or involuntary, endocrine system is always involuntary
Nervous system & endocrine system target
Nervous system is localized (cells connected to neuron), endocrine system is often distant (many cells can be effected)
Hypothalamus
Structure of diencephalon of brain located anterior and inferior to thalamus and links the endocrine and nervous system
Division of pituitary lobes
Anterior pituitary, posterior pituitary
Hypothalamus functions
Produces releasing hormones that stimulate the secretion of separate hormones from anterior pituitary + produces inhibiting hormones. It also produces oxytocin and ADH that is transported via neurons and stored/released in posterior pituitary
Produced in hypothalamus and released from anterior pituitary (releasing hormones) (4)
- Corticotropoin releasing hormone (CRH)
- Thyrotropin releasing hormone (TRH)
- Gonadotropin releasing hormone (GnRH)
- Growth hormone releasing hormone (GHRH)
Inhibiting hormone produced by hypothalamus
Prolactin inhibiting hormone (PIH)
Interrelationship between hypothalamus and anterior pituitary gland
4 of the hormones that the hypothalamus produces act as releasing factors that stimulate the secretion of 5 separate hormones from anterior pituitary gland
Produced in hypothalamus and released from posterior pituitary (2):
- Oxytocin
- ADH
Does the posterior pituitary gland produce any hormones of its own
No, only the anterior pituitary gland. The hormones produced by the hypothalamus (oxytocin and ADH) travel down neuron axons from cell bodies in hypothalamus to the posterior pituitary gland where it is stored and released into the blood
Anterior pituitary hormones (6)
- Follicle stimulating hormone F(SH)
- Leuteinizing hormone L(H)
- Adrenocorticotropic hormone A(CTH)
- Thyroid stimulating hormone T(SH)
- Prolactin P
- Growth hormone G(H)
- = FLAT PiG
Follicle stimulating hormone (FSH)
Stimulates growth and hormone activity in ovarian follicles
Leuteinizing hormone (LH)
Causes development of corpus luteum (ovarian structure) and stimulates secretion of testosterone
What is LH called in males
Interstitial cell stimulating hormone
Adrenocorticotropic hormone (ACTH)
Stimulates adrenal cortex to produce glucocorticoids to control body metabolism
Thyroid stimulating hormone (TSH
Stimulates thyroid gland to release thyroxin to control body metabolism
Prolactin
Stimulates milk in female mammary glands
Growth hormone (GH)
Promotes growth in all body tissues by promoting increase in cell size and increasing synthesis of proteins and body metabolism
Hypersecretion
Overproduction of hormone
Hyposecretion
Underproduction of hormone
Pituitary dwarfism cause
Underproduction (hyposecretion) of growth hormone during childhood
Simmonds disease cause
Overproduction (hypersecretion) of growth hormone in adults
Giantism cause
Overproduction (hypersecretion) of growth hormone in childhood
Acromegaly
Condition from hypersecretion of growth hormone and very slow growth and thickening of bones, organ and tissues
Oxytocin
Causes contraction of smooth muscle of uterus to expel fetus and causes ejection of milk from mammary gland
ADH
Increases water reabsorption in the kidney by increasing the permeability to water of the distal convoluted tubule and collecting of duct in nephron. This action + narrowing diameter of BV can be used to raise blood pressure
Thyroid gland
Consists of two lobes joined together by isthmus across bottom of larynx and produces hormone thyroxine and calcitonin
Thyroxin functions (5)
- Increase metabolic rate
- Increase breakdown of fats and carbohydrates
- Increase protein synthesis
- Maintains body temperature
- Stimulates growth of nervous and skeletal system
Calcitonin functions (3)
- Lowers blood calcium and phosphate levels by inhibiting osteoclast activity (cells that breakdown bone)
- Not controlled by hypothalamus/anterior pituitary and controlled by negative feedback of calcium levels in blood
Parathyroid gland
Secrete parathyroid hormone (parathormone)
Parathormone function
Increases blood calcium by stimulating release of calcium/phosphate from bone tissue and increases absorption of calcium from intestinal mucosa and increased reabsorption of calcium in kidney
Bone formation
Osteoblasts (calcitonin from thyroid)
Bone resorption
Osteoclasts (parathyroid hormone)
Adrenal gland
Wedges of glandular and neuroendocrine tissue adhering to the top of the kidneys by a fibrous capsule separated into 2 regions; outer cortex, inner medulla
3 zones of adrenal cortex:
- Zone glomerulosa
- Zone fasciculata
- Zone reticularis
Zone glomerulosa (4)
- Secretes mineralcorticoids (salts)
- Mainly aldosterone
- Promotes Na+ and water reabsorption
- Promotes K+ and H+ secretion in urine
Zone fasciculata (6)
- Secretes glucocorticoids (sugars)
- Mainly cortisol
- Secretion regulated by ACTH and ACTH - RH
- Increases body’s resistance to stress
- Stimulates protein catabolism and glucose anabolism
- Anti-inflammatory action
Zone reticularis (3)
- Secretes androgens (sex)
- Serve as source of sex hormones until gonads mature at puberty
- Development of secondary sex characteristics in female and males
Mineralocorticoids
Hormones essential for fluid and electrolyte balance (not controlled by ACTH from pituitary gland)
Glucocorticoids
Hormones in response to long-term stressors. Hypothalamus secretes CRH which triggers release of ACTH by anterior pituitary
Androgens
Production of cortical sex hormones upon influence of ACTH from anterior pituitary gland
Adrenal medulla
Secretes epinephrine and norepinephrine (adrenalin/nonadrenalin) under ANS control
Adrenal medulla functions
Fear, excitement and danger responses
Epinephrine functions
Increase blood pressure, depth of breathing, increase heart rate and glucose levels
Norepinephrine functions
Increase blood pressure, decrease blood flow to the gut and skin
Pancreas
Both endocrine and exocrine gland (but mostly exocrine). Endocrine tissue within pancreas is located in areas called the islets of Langerhans
Insulin
Produced by islets of Langerhans from beta cells to lower blood sugar by increasing glucose uptake by body cells
Glucagon
Produced by islets of Langerhans from alpha cells to raise blood sugar
2 hormones produced by the ovaries in women
Estrogen, progesterone
Estrogen
Produced by ovarian follicles and stimulates growth of primary and secondary sex characteristics
Progesterone
Produced by the corpus luteum and stimulates the development of milk-secretory tissue in the breasts and maintains pregnancy
Hormone produced by testes in males
Testosterone
Testosterone
Stimulates development of primary and secondary sex characteristics like accessory glands, penis, body hair, deepening of voice
Gastrin
Hormone responsible for the secretion of hydrochloric acid in stomach, and some enzymes
Duodenum
Produces hormone called secretin that stimulates the pancreas to produce pancreatic juice that lead to digestion
Thymus
Located in the chest between lungs and secretes thymosin. The thymus is larger in infants, than in adults
Thymosin
Hormone involved in growth and maturation of immune cells by promoting maturation of T-cells
Pineal gland
Found in the brain attached to the roof of the 3rd ventricle and produces hormone melatonin
Melatonin characteristics/function
Responsive to light and regulates daily and seasonal circadian rhythms. It also effects gonad activity by inhibiting LH release. Levels increase 10 fold during sleep
Prostaglandins
Produced by the cell membrane and are lipids in nature. They are found in all body cells except for blood cells. They differ from hormones because they have specific effects on local target tissues
Prostaglandins functions:
- Blood pressure
- Stomach secretions
- Nerve impulse transmission
- Uterine contractions
- Immune responses
