A&P Exam and Lab Practical 1

Endocrine System Function

Along with nervous system, regulates functions of body to maintain homeostasis, and coordinates communication

Major endocrine glands

Pituitary gland, thyroid gland, parathyroid glands, adrenal glands, pancreas, pineal gland, thymus, ovaries & testes

Endocrine glands

ductless; secretes homornes directly into the body fluids. hormones only act on target cells that contain receptors for them.

exocrine glands

glands that secrete into ducts or tubes that lead to a body surface; secrete externally & delivers products directly to a specific site

“local hormones"

other cells beside exocrine/endocrine glands secrete these; paracrine/autocrine secretions

paracrine secretions

affect nearby cells

autocrine secretions

affect only the cells that secrete them

Nervous system vs endocrine system

neurotransmitters/hormones; nervous system responds faster while endocrine system effects last longer

hormones

released into extracellular fluid, & then diffuse into blood; method of transport depends of if hormone is lipid or water soluble; powerful in low concentrations

steroid/steroid-like hormones

lipids containing complex rings of carbon & hydrogen atoms; produced from cholesterol; sex hormones & adrenal cortex hormones (cortisol, aldosterone)

nonsteroid hormones

amines, proteins, peptides, glycoproteins

Amine hormone

derived from tyrosine; epinephrine, noepinephrine, thyroxine

protein hormones

long chains of amino acids; growth hormone

peptide proteins

short chains of amino acids; ADH, oxytocin

glycoprotein hormones

carbohydrates joined to proteins; TSH

hormone actions

exert effects by altering metabolic processes: may alter enzyme activity, may change rate of membrane transportation of a substance

hormone actions

delivered messages by binding to their receptors on/in target cells; can cause changes in target cells even in extremely low concentrations

hormone actions

number of receptors determines strength of response, & can be changed to alter the response: upregulation, downregulation

upregulation

increase in number of receptors on target cell, in response to a decrease in hormone level

downregulation

decrease in number of receptors on target cell, due to an increase in hormone level

steroid & thyroid hormones

have poor water-solubility; transported through lipid bilayer of cell membrane; bind to receptors inside cell (usually nucleus); cause transcription of particular genes; protein synthesis leads to the action

steroid vs thyroid hormones

steroid hormones can diffuse through lipid bilayer of cell membrane; thyroid hormones enter cell by specific transport methods

sequence of steroid hormone action

1. endocrine gland secretes steroid hormone

2. blood carries hormone molecules throughout body

3. unbound steroid hormone diffused through target cell membrane & enters cytoplasm or nucleus

4. hormone combines with a receptor molecule in cytoplasm or nucleus

5. steroid hormone-receptor complex binds to DNA in nucleus and promotes transcription of messenger RNA

6. messenger RNA enters cytoplasm and directs protein synthesis

7. Newly synthesized proteins produce the steroid hormone’s specific effects

nonsteroid hormone action

cannot penetrate the lipid bilayer of cell membranes; binds to receptors on the target cell membranes; use cAMP as second messenger

signal transduction

process of chemical communication from outside cells to inside

first messenger

hormone

second messenger

chemical that induces changes leading to hormone’s effect

sequence of actions of nonsteroid hormones

1. endocrine gland secretes nonsteroid hormone

2. blood carries hormone molecules throughout body

3. hormone combines with receptor site on membrane of target cell, activating G protein

4. adenylate cyclase are activated

5. Adenylate cyclase converted ATP into cyclic AMP

6. cyclic AMP activates protein kinases

7. protein kinases activate protein substrates in cell that changes metabolic processes

8. cellular changes produce hormones effects

prostaglandins

paracrine substances: potent in small amounts; not stored in cells; rapidly inactivated after use; regulate cellular responses to hormones

control of hormonal secretions

precisely regulated; negative feedback; effects can last from a few minutes to days; some excreted in urine after use; can be broken down by enzymes, mainly from liver to stop effects

pituitary gland

in sella turcica of sphenoid bone; attached to hypothalamus by pituitary stalk (infundibulum); anterior lobe & posterior lobe; secretion is controlled by hypothalamus

anterior lobe of pituitary regulation

hypothalamic releasing hormones are transported to lobe through hypophyseal portal veins & stimulates or inhibit cells of lobe to release hormones

posterior lobe of pituitary gland regulation

nerve impulses from hypothalamus travel to lobe through infundibulum & stimulates nerve endings in lobe to release hormones

releasing (or release-inhibiting) hormone

from hypothalamus & acts on specific hormone-secreting cells in anterior pituitary

anterior pituitary hormone

acts on cells in peripheral endocrine gland to stimulate secretion

peripheral endocrine gland

secretes its hormone, which exerts effects on target cells

anterior pituitary hormones

growth hormone, prolactin, thyroid-stimulating hormone (TSH), Adrenocorticotropic hormone (ACTH), follicle stimulating hormone (FSH), luteinizing hormone (LH)

hypopituitary dwarfism

deficiency of growth hormone during childhood; short stature but regular body proportions; hgh treatment must start before bones ossify

gigantism

over secretion of GH in childhood; height may exceed 8 ft; often cause by pituitary tumor

acromegaly

over secretion of GH in adulthood; bones thicken & enlargement of tongue, nose, hands, feet, jaw, heart, thyroid gland

posterior pituitary hormones

Antidiuretic hormone (ADH, vasopressin) & oxytocin

growth hormone

stimulates increase in size & rate of division of body cells & enhances movement of amino acids through membranes

prolactin (PRL)

sustains milk production after birth; amplifies effects of luteinizing hormone in males

thyroid stimulating hormone (TSH)

controls secretion of hormones from the thyroid gland

Adrenocorticotropic hormone (ACTH)

controls secretion of certain hormones from the adrenal cortex

follicle stimulating hormone (FSH)

promotes development of egg-containing follicles in ovaries & stimulates follicular cells to secrete estrogen; stimulates production of sperm in males

luteinizing hormone (LH)

promotes secretion of sex hormones; releases egg cell in females

Antidiuretic hormone (ADH)

causes kidneys to reduce water excretion; may help maintain blood pressure

Oxytocin (OT)

contracts smooth muscle in uterine wall; forces liquid from milk glands into milk ducts & ejects milk

thyroid gland

2 lateral lobes just below larynx connected by isthmus; composed of round secretory units called follicles & each follicle is surrounded by a single layer of follicular cells; colloid fills follicle cavities

hormones of the thyroid gland

thyroxine (T4), triiodothyronine (T3), & calcitonin

thyroxine (T4)

increases rate of energy release from carbohydrates; increases rate of protein synthesis; accelerates growth; necessary for nervous system maturation

triiodothyronine (T3)

same as thyroxine but much more potent

calcitonin

lowers blood calcium and phosphate ion concentrations by inhibiting release of calcium and phosphate ions from bones & increasing excretion of calcium by kidneys

hypothyroidism

causes low metabolic rate, resulting in cold sensitivity, fatigue, & weight gain; can cause problems with bone formation, growth, and intellectual abilities in newborns

hyperthyroidism

causes high metabolic rate resulting in restlessness, weight loss, & overeating; caused by non cancerous thyroid tumor, excess T4 medication, or autoimmune disease

graves’ disease

autoantibodies bind TSH receptors on thyroid cell membranes, overstimulating gland; profusion of eyes and goiters

hashimoto disease

autoantibodies destroy thyroid cells, resulting in hypothyroidism

simple goiter

deficiency of thyroid hormones due to iodine deficiency; thyroid enlarges but functions normally

parathyroid glands

located on posterior surface of thyroid gland — most people have 4; secretes parathyroid hormones

parathyroid hormone (PTH)

increases blood level of calcium & decreases phosphate; stimulates bone resorption, indirectly stimulates calcium absorption, acts on kidney to cause final step in production of vitamin D, conserves calcium in kidneys, & excretes phosphate in urine

hyperparathyroidism

fatigue, muscle weakness, painful joints, altered mental functions, depression, weight loss, bone weakening — increased PTH secretion overstimulates osteoclasts; caused by tumor

hypoparathyroidism

muscle cramps & seizures; decreased PTH secretion reduces osteoclasts activity, diminishing blood calcium ion concentration; caused by injury or surgical removal

adrenal glands

sit like cap on each kidney; consists of outer cortex & inner medulla

adrenal cortex hormones

aldosterone, cortisol, sex hormones

adrenal medulla hormones

80% epinephrine & 20% norepinephrine

function of epinephrine & norepinephrine

mimic sympathetic stimulation; increased heart rate, blood pressure, airflow to lungs, blood glucose level, & decreased digestive activities

major difference between epinephrine & norepinephrine

epinephrine causes vasodilation while norepinephrine causes vasoconstriction in skin & viscera

aldosterone

helps regulate the concentration of extracellular electrolytes by conserving sodium ions and excreting potassium ions

cortisol

decreases protein synthesis, increases fatty acid release, & stimulates glucose synthesis from noncarbohydrates

adrenal androgens

supplement sex hormones from gonads; may be converted into estrogen

renin-angiotensin system

system that helps maintain blood pressure; the product of this system, angiotensin II, increases blood pressure & promotes secretion of aldosterone

addison disease

insufficient hormone secretion from adrenal cortex; electrolyte & glucose imbalances, dehydration, low blood pressure, fatigue, nausea, increased skin pigment — can be fatal

cushing syndrome

hyper secretion of cortisol due to adrenal tumor or excess ACTH from pituitary; muscle wasting, loss of bone, elevated blood glucose, sodium retention & water retention, high blood pressure, puffy skin, abnormal fat tissue in face & back

pancreas

elongated, flattened organ posterior to stomach; pancreatic duct transports digestive juice to duodenum; is both an endocrine & exocrine gland

endocrine function of pancreas

secretes hormones into body fluids; glucagon, insulin, & somatostatin

exocrine function of pancreas

secretes digestive juices through pancreatic duct

glucagon

stimulates liver to break down glycogen & convert noncarbohydrates into glucose; stimulates break down of fats

insulin

promotes formation of glycogen from glucose, inhibits conversion of noncarbs into glucose, enhances movement of glucose through adipose & muscle cell membranes which decreases blood glucose concentration; promotes transport of amino acids into cells, enhances synthesis of proteins & fats

somatostatin

helps regulate carbohydrates

diabetes mellitus

lack of insulin or inability of cells to recognize insulin; elevated blood glucose causes damage to eyes, heart, kidney, & nerves; hyperglycemia; weight declines, hunger increases, fatigue increases, wounds do not heal well, growth stops in children, dehydration

type 1 diabetes mellitus

usually begins before age 20; autoimmune disease — immune system destroys beta cells of pancreas resulting in a lack of insulin production; 5-10% of cases

type 2 diabetes mellitus

90-95% of cases; insulin is produced but body cells do not recognize it; milder than type 1; coronary artery disease, nerve or retinal damage; also called maturity-onset or non-insulin-dependent

treating type 1 diabetes

administration of insulin obtained from pigs and cattle through injection, insulin pump, or aerosol form

treating type 2 diabetes

low carb, high protein diet, regular exercise, medications that increase glucose production, gastric bypass surgery

pineal gland

between cerebral hemispheres in brain; secretes melatonin which regulates circadian rhythms

thymus gland

found in mediastinum between lungs; secretes thompson which promote development of T-lymphocytes; important role in immunity

reproductive organs in endocrine system

ovaries produce estrogen and progesterone; testes produce testosterone; placenta produces estrogens, progesterones, and a gonadotropin

digestive glands

produces hormones to regulate digestion

heart function in endocrine system

produces natiuretic peptides to stimulate sodium secretion in urine

function of hypothalamus in stress response

hypothalamus activates sympathetic nervous system & increases secretion of adrenal hormones

general adaption syndrome

the response of the hypothalamus in response to stress; alarm stage, resistance stage, & exhaustion stage

alarm stage

fight or flight response; sympathetic impulses increase blood glucose & fatty acids, heart & breathing rate & blood pressure, dialates air passages, shunt blood to skeletal muscles, increases epinephrine secretion

resistance stage

slower & longer lasting; increased cortisol secretion; cortisol, glucagon, and GH mobilize energy sources for other tissues & organs; ADH & renin cause water retention

exhaustion stage

begins after months of resistance stage; wasting due to depletion of nutrients in body, electrolyte imbalance, suppressed immune system; due to long-term cortisone over secretion, can result in death

life-span changes in endocrine system

endocrine glands decrease in size, muscular & skeletal strength decreases as GH levels decline, ADH levels increase due to slower elimination by liver and kidneys, calcitonin levels decrease & PTH levels change causing increased risk of osteoporosis, insulin resistance may develop, changes in melatonin secretion, thymosin production declines increasing risk of infection

pancreas (picture)

adrenal glands (picture)

kinsey function in endocrine system

produces erythropoietin to stimulate red blood cell production

thymus gland (picture)