Describe endocrine system function:   It releases chemical (hormone) into the bloodstream to be distributed thru the body.; hormones can alter metabolic activities of many different, specific target tissues and organs at the same time; and produces effects that can last for hours, days, or longer. (slower with longer lasting, more general effects than nervous system).  A cell is determined to be a target cell by the presence of specific receptors for that specific hormone.
* What sort of effects does the endocrine system have?

* What is the distribution pathway for the endocrine system?

* What determines if a cell is a target cell for a specific hormone?

*  What are the two characteristics of endocrine glands that differ from exocrine glands?

 
 Hormone concentrations are regulated by nerve control and what sort of feedback?  both negative feedback (minimize change) and positive feedback (maximize change)
* In what 3 ways are hormone concentrations regulated?

* What homeostatic mechanism is responsible for a person sweating when they are hot?

*  Oxytocin, secreted by ___________(what gland) has a role in childbirth.  What form of feedback would this be?

 
 Paracrine regulation  Chemical molecules are released and act within an organ...cells of organ regulate one another; these include prostglandins, cytokines, nitric oxide, and growth factors
 * Describe paracrine regulation.

 * Paracrine regulation includes what chemicals?

 
 Hormones  Within the category of hormones are polypeptides, glycoproteins, amines, and steroids
 * Name the types of hormones.  
 Describe steroid hormone activity   being lipid derivatives, these hormones have the ability to pass through the plasma membrane of their target cells, so their receptors are intracellular; their effect on the target cell is to influence cell activity through gene activation
*  Where would you expect to find the receptors for steroid hormones?

*  So are steroid hormones hydrophilic or lipophilic?

*  How do steroid hormones effect their target cell's activity?

Consider:  Nonpolar (lipophilic) hormones pass through the plasma membranes of intestinal epithelial cells without being digested and therefore can be taken orally as pills.  These include steroid and thyroid hormones.
 Describe non-steroid hormone activity  being protein, peptide, or amino acid derivatives, these hormones are large, water soluble molecules and do not have the ability to pass through the plasma membrane, so they have membrane-bound receptors; insulin is an example
*  What sort of signals would you expect to bind to membrane-bound receptors?

*  Give an example of this type of hormone.

 
 Describe activity of membrane-bound receptors  These can activate such functions as opening or closing membrane channels, activate G proteins, activate second messengers to produce cascading effects thru activating enzymes found in cell, and activate enzymes attached to cell membrane
*  What functions can membrane bound receptors activate?  
 Describe the relationship between the hypothalamus and the posterior lobe of the pituitary gland. hypothalamus, acting as endocrine gland, produces ADH (antidiuretic hormone (peptide) targeting kidneys to increase water reabsorption) and oxytocin (targets both male [sperm duct & prostate] and female [uterus for birth contractions & mammary glands for stimulation of milk-ejection reflex]).  These hormones are transported from the hypothalamus by neuron axons and are released through the posterior lobe of the pituitary gland.
* ADH and oxytocin are produced where and secreted where?  How do they arrive in the posterior pituitary?

* ADH targets what cells?

* Oxytocin targets what cells in a man and what cells in a woman?  This causes what in the woman?

*  Consider:  Consumption of alcohol stimulates urination by inhibiting ADH secretion.
 Describe the relationship between the hypothalamus and the anterior lobe of the pituitary gland.  The hypothalamus produces releasing hormones that travel through the hypothalamic-pituitary portal system to target cells in the anterior lobe of the pituitary gland, thereby stimulating these target cells to produce and secrete different hormones targeting different cells throughout the body.  These anterior pituitary hormones' activities are controlled by negative feedback.
*  What has primary control over the secretion of hormones from the anterior lobe of the pituitary gland?  What type of feedback controls the activities of these hormones.

*  Where are the target cells for the releasing hormones secreted from the hypothalamus?

*  Where are the target cells for the hormones produced and released by the anterior pituitary? (general idea)

 
 What is a portal system?  A portal system is where blood passes through  multiple capillary beds before returning to the heart
 *  Describe the hypothalamic-pituitary portal system?  
 Growth hormone (anterior pituitary)  Targets bones, muscles, and other tissues to stimulate growth (by promoting movement of amino acids into cells, increase rate of cell division and rate of fat metabolism) through puberty; excessive amounts after growth completion produces acromegaly and insufficient amounts in childhood can produce growth failure
*  Growth hormone targets all cells and promotes what activities to increase growth?

*  Acromegaly is what condition?

*  Growth hormone is released by what gland?

 
 Gonadotropins (anterior pituitary)  FSH and LH target and regulate growth, development and function of testes and ovaries
 * Growth, development, and function of the testes and ovaries are controlled by what two gonadotropin  hormones?  
 Parathyroid hormone (parathyroids)  Targets osteoclasts in bone to increase bone breakdown, causes kidneys to reabsorb calcium ions from the urine, and triggers activation of vitamin D... all thereby increasing blood calcium levels; produced by chief cells in parathyroids
 * What hormone, responding to and controlled by  falling calcium levels in blood, increases osteoclast activity?

* An increase in osteoclasts activity brings about what effect?

* What else does the parathyroid hormone cause to happen?

 
calcitonin   Inhibits osteoclast activity, thereby increasing calcium deposition in bone and increases excretion of calcium in kidneys; these activities cause calcium levels in blood to decline
 * What hormone is responsible for maintaining homeostasis when blood calcium levels are rising?

*  How does calcitonin bring about  a decline in blood calcium levels?

 
 Adrenal medulla  Sympathetic division nerve fibers of autonomic nervous system, stimulated by an excited person, causes adrenal medulla to produce epinephrine and norepinephrine which produce the fight-or-flight response (read "consider" below to see what is effected thru epinephrine and norepinephrine release)
*  What gland is responsible for secreting hormones involved in the "fight-or-flight" response?  What are these hormones?

*  Nerve fibers of what portion of the nervous system are stimulated to cause the adrenal medulla to secrete what hormones?

*  What is the response to these "fight-or-flight" hormones?

*  Why is always experiencing a heightened level of stress so negative to your health? (look at "consider").  Which hormones are primarily responsible for the resistance phase?

 

Consider:  Any condition within the body that threatens homeostasis a form of stress.  The body has a general response to stress.  These are known a the general adaptation syndrome, or GAS.  The 3 phases of this syndrome are the alarm phase (immediate; sympathetic activation with epinephrine & norepinephrine release --> glucose mobilization, circulation changes, increases in respiratory & heart rates, increased energy use by cells), the resistance phase (long-term metabolic adjustment; glucocorticoids released by adrenal cortex lead to mobilization of remaining energy reserves, conservation of glucose, elevation of blood glucose concentrations), and the exhaustion phase (collapse of vital systems which can lead to death).

Consider:  Norepinephrine can act both as a hormone and as a neurotransmitter.

 fight-or-flight response  sympathetic division of the nervous system; both stimulatory (increased heart rate, breakdown of glycogen to glucose, increased blood flow to skeletal muscles, release of fatty acids) and inhibitory (dilation of bronchioles leading to lungs, decrease of blood flow through digestive system)
   
Adrenal cortex hormones are all steroids; cortisol acts to maintain glucose homeostasis by stimulation breakdown of protein into a.a., which are converted into glucose by the liver (important during long periods of exercise or fasting) and has a role as an anti-inflammatory agent; aldosterone regulates mineral balance by stimulating sodium reabsorption from urine and potassium excretion
*  What category of hormones does the adrenal cortex produce?

*  If you were starving, how would cortisol effect your body?

*  What is the role of aldosterone?

Consider:  The right atrium of the heart secretes atrial natriuretic hormone, which stimulates the kidneys to excrete salt and water in the urine.  This is an antagonistic act to aldosterone.
 Describe endocrine function of pancreas  Islet cells are found among exocrine portion; when blood glucose levels increase, Beta cells secrete insulin (target cells to increase glucose uptake from blood leading to ATP generation, conversion of glucose to glycogen, protein synthesis, fat synthesis) and when blood glucose levels decrease, Alpha cells secrete glucagon ( target liver & muscel cells to convert glycogen into glucose for release into blood, increase breakdown of fats to fatty acids for the liver to convert to glucose)
*  Insulin, secreted by ________ cells in the pancreas, causes what to happen to blood glucose concentrations?

* Glucagon, secreted by _________ cells in the pancreas, causes what to happen to blood glucose concentrations?

 

Consider:  Blood glucose homeostasis is maintained thru the balancing of insulin release when blood glucose levels rise and glucagon release when blood glucose levels decline.  This helps prevent competition between neural tissues (which only use glucose as an energy source; cannot metabolize other nutrients) and other tissue for limited glucose supplies.  Both the pancreas and the adrenal cortex can be stimulated to produce hormones primarily by the concentration of certain molecules and ions in the blood, rather than neural control.

Consider:  The pancreas has a role as an endocrine gland and as an exocrine gland.

 What is body's response to irregular blood levels of glucose? too low:  Hypoglycemia can make you feel weak, confused, irritable, hungry, or tired. You may sweat a lot or get a headache. You may feel shaky. If blood glucose drops lower, you could pass out or have a seizure indicating a nervous system malfunction.

too high: 

 Fruity (acetone) breath
   Nausea and/or vomiting
   Abdominal pain
   Dry, warm skin
   Confusion
   Fatigue
   Breathing problems
   Excessive thirst
   Frequent urination
   In extreme cases, loss of consciousness

or

  • Excessive thirst and dehydration
  • Nausea and vomiting
  • Disorientation and confusion
  • Sudden hypotension, or low blood pressure (as evidenced by faintness)
  • Visual problems
  • Extreme, unexplained fatigue
  • Fever
  • In advanced cases, coma or seizure

 

   
Diabetes mellitus  results because tissues cannot take up glucose effectively, blood glucose levels become too high; proteins are broken down for metabolic energy and fat breakdown can lead to acidosis
*  A person exhibiting symptoms of excessive thirst and dehydration, excessive urination, disorientation,  extreme fatigue, excessive peeing, nausea may be showing signs of what?

*  Insulin-dependent diabetes is related to what condition in the pancreas? What is required to treat the symptoms?

*  Insulin-independent diabetes is related to what condition in the body's cells? What is required to treat the symptoms?

Consider:  Insulin dependent diabetes (Type I juvenile-onset) is due to inadequate insulin production by beta cells; insulin injections required;  Insulin independent diabetes (Type II maturity onset) is due to reduction in number of insulin receptors; life-style changes required (diet, exercise, weight)..