Chapter 16 Endocrine System Flashcards
1
Q
define crine
A
to secrete
2
Q
nervous system
A
- sends messages via neurons
- fast and precise
- crisis management
3
Q
endocrine system
A
- sends messages via hormones
- slower, last longer, target most cells of body
- controls ongoing metabolic processes
4
Q
endocrine system: overview
A
- acts with the nervous system to coordinate and integrate the activity of body cells
- influences metabolic activities via hormones through blood
- system is slower but lasts longer than NS
- endocrine glands: pituitary, thyroid, parathyroid, adrenal, and pineal glands
5
Q
main classes of hormones
A
- two main classes:
- amino acid-based hormones (water based)
- steroids (lipid based)
6
Q
amino acid-based hormones
A
- water based
- amines, thyroxine, peptides, and proteins
- cannot cross cell membrane
- binds to receptors on membrane
7
Q
steroids
A
- lipid based
- synthesized from cholesterol
- gonadal and adrenocortical hormones
- since they are lipids -> can cross cell membrane
8
Q
hypothalamus
A
- controls the pituitary gland
- brain region
9
Q
pituitary gland
A
- master hormone
- secretes many different hormones
- some of which affect other glands
10
Q
thyroid gland
A
-affects metabolism among other things
11
Q
parathyroids
A
-help regulate level of calcium in the blood
12
Q
adrenal glands
A
-help to trigger the fight or flight response
13
Q
pancreas
A
-regulates the level of sugar in the blood
14
Q
ovary
A
secretes female sex hormone
15
Q
testis
A
secretes male sex hormones
16
Q
mechanism of hormone action
A
- hormone action on target cells has receptor for that hormone
- alter plasma membrane permeability of membrane potential by opening or closing ion channels
- stimulate synthesis of proteins or regulatory molecules
- activate or deactivate enzymes systems
- induce secretory activity
- stimulate mitosis
17
Q
mechanism of hormone action: amino-acid hormones (except thyroid)
A
- usually, water soluble
- binds to receptors on cell membrane (extracellular receptors)
- receptors on plasma membrane for water soluble hormones*
- activates G protein
- activates an enzyme (adenylate cyclase) inside cell
- enzyme (adenylate cyclase) converts ATP to secondary messengers (cAMP)
- secondary messengers (cAMP) activates protein kinases
18
Q
mechanism of hormone action: steroid hormones
A
- steroid hormones enter cell by passing directly across membrane
- binds to receptor to form hormone-receptor complex (intracellular receptor*)
- complex enters nucleus
- bind to DNA region
- initiates transcription of the gene to mRNA
- sends a message via mRNA directing protein synthesis
19
Q
3 plasma membrane components
A
- receptor
- G protein
- enzyme
20
Q
target cell specificity
A
- target cells must have specific receptors to which the hormone binds
- ACTH (adrenocorticotropic hormone) receptors are only found on certain cells of the adrenal cortex
- thyroxin receptors are found on nearly all cells of the body
21
Q
target cell activation
A
- target cell activation depends on 3 factors
- blood levels of the hormone
- relative number of receptors on or in the target cell
- affinity of binding between receptor and hormone
22
Q
Receptors are dynamic
A
- hormones influence the number of their receptors
- up-regulation- target cells form more receptors in response to low levels of the hormone
- down-regulation- target cells lose receptors in response to high level of the hormone
23
Q
hormones in the blood
A
- hormones are removed from the blood by:
- degrading enzymes
- kidneys
- liver
- half-life- the time required for a hormones blood level to decrease by half
- insulin (6 mins half life) vs cortisol (1 hour half life)
24
Q
permissiveness
A
one hormone cannot exert its effect without another hormone being present (i.e. reproductive hormones and thyroid hormones)
25
synergism
-more than one hormone produces the same effect on a target cell (glucagon and epinephrine cause liver to release glucose to blood)
26
antagonism
-one or more hormones opposes the action of another hormone (insulin and glucagon)
27
control of hormone release
- blood levels of hormones are controlled by negative feedback systems
- vary only within a narrow desirable range
- hormones are synthesized and released in response to:
- 1. humoral stimuli (fluids)
- 2. neural stimuli
- 3. hormonal stimuli (cascade effect)
28
humoral stimuli
- changing blood levels of ions and nutrients directly stimulates secretion of hormones
- ex. Ca2+ in the blood
- declining blood Ca2+ concentration stimulates the parathyroid glands to secrete PTH (parathyroid hormone)
- PTH causes Ca2+ concentrations to rise and the stimulus is removed
29
neural stimuli
- nerve fibers stimulate hormone release
- in response to stress sympathetic nervous system fibers stimulate the adrenal medulla to secrete catecholamines (NE and E)
- when did we recently see a release of Epinephrine (hint: extrinsic regulation) -> fight of flight response
- preganglionic sympathetic fibers stimulate adrenal medulla cells -> medulla of adrenal gland secretes catecholamines (epinephrine and norepinephrine)
30
hormonal stimuli
- hormones stimulate other endocrine organs to release their hormones
- hypothalamic hormones stimulate the release of most anterior pituitary hormones
- anterior pituitary hormones stimulate targets to secrete still more hormones
- hypothalamic-pituitary-target endocrine organ feedback loop- hormones from the final target organs inhibit the release of the anterior pituitary hormones
- tropic hormones- hormones that stimulate other hormones
- ex. hypothalamus secrete hormones that -> Stimulate the anterior pituitary gland to secrete hormones that -> stimulate other endocrine glands to secrete hormones (thyroid, adrenal, gonad)
31
nervous system modulation
- the nervous system modifies the stimulation of endocrine glands and their negative feedback mechanisms
- ex. under severe stress, the hypothalamus and the sympathetic nervous system are activated -> as a result blood glucose levels rise
- without nervous system the endocrine system strictly mechanical (i.e. home thermostat)
32
when one hormone is not effective unless another hormone is present is called
- synergism
- antagonism
- permissiveness*
- specificity
33
anterior pituitary gland
- growth hormone (GH)- protein synthesis and growth in cells
- thyroid stimulating hormone (TSH) or thyrotropin *- stimulates synthesis and release of thyroid hormone from thyroid
- adrenocorticotropic hormone (ACTH) *- stimulates release of hormones from adrenal cortex
- follicle stimulating hormone (FSH) *- production of egg/sperm, prepares uterus for implantation of fertilized egg
- luteinizing hormone (LH) *- production of egg/sperm, prepares uterus for implantation of fertilized egg
- prolactin (PRL)- stimulates milk production
- ***** tropic hormones
34
posterior pituitary gland
- antidiuretic hormone (ADH)- reabsorbs water from collecting duct
- oxytocin- uterus contractions, releases milk in nursing mothers
35
thyroid gland
- T3/T4- cell metabolism
| - calcitonin- lowers blood caclium
36
parathyroid gland
PTH- raises blood calcium
37
adrenal cortex
- mineralocorticoids
- glucocorticoids
- gonadocorticoids
- all of these regulate Na ions, energy metabolism, weak sex hormones
38
adrenal medulla glands
- epinephrine
- norepinephrine
- fight or flight
39
pineal gland
-melatonin- circadian rhythm
40
pancreas
- insulin- lowers blood sugar
| - glucagon- raises blood sugar
41
ovary gland
- estrogen
- progesterone
- female sex characteristics
42
testes
testosterone
| -male sex characteristics
43
the pituitary gland and hypothalamus
- the pituitary gland (hypophysis) has two major lobes:
- 1. posterior pituitary (lobe) (neurohypophysis)- neural tissue, hormone storage, does not manufacture
- 2. anterior pituitary (lobe) (adenohypophysis)- glandular tissue
- hypothalamus has direct control over posterior lobe and indirect control over anterior lobe
44
posterior lobe (neurohypophysis)
- neural connection to the hypothalamus
- nuclei of the hypothalamus (cell bodies) synthesize the neurohormones oxytocin and antidiuretic hormone (ADH)
- when cell bodies in hypothalamus are stimulated, axons in posterior release the hormones into blood stream
- posterior pituitary is an extension of hypothalamus
- neural tissue
- hormone storage
- does not manufacture
- 1. hypothalamus neurons synthesize oxytocin or antidiuretic hormone (ADH)
- 2. oxytocin and ADH are transported down the axons of the hypothalamic-hypophyseal tract to the posterior pituitary
- 3. oxytocin and ADH are stored in axon terminals in the posterior pituitary
- 4. when hypothalamic neurons fire action potentials arriving at the axon terminals cause oxytocin or ADH to be released into the blood
45
anterior lobe (adenohypophysis)
- no direct neural connection but a vascular connection
- via the hypophyseal portal system (hormones via capillaries and veins)
- hormones secreted by neurons in hypothalamus circulate to anterior pituitary
- anterior pituitary -> master endocrine gland -> BUT recently dethroned by hypothalamus
- glandular tissue
- 1. when appropriately stimulated, hypothalamic neurons secrete releasing or inhibiting hormones into the primary capillary plexus
- 2. hypothalamic hormones travel through portal veins to the anterior pituitary where they stimulate or inhibit release of hormones made in the anterior pituitary
- 3. in response to releasing hormones, the anterior pituitary secretes hormones into the secondary capillary plexus -> empties into the general circulation
- GH, TSH, ACTH, FSH, LH, PRL
46
portal system
two capillary plexuses (beds) connected by veins
47
tropic hormones
- thyroid stimulating hormone (TSH) or thyrotropin
- adrenocorticotropic hormone (ACTH)
- follicle stimulating hormone (FSH)
- luteinizing hormone (LH)
48
growth hormone (GH)
- stimulates most cells, but targets bone and skeletal muscle, anabolic hormone
- promotes protein synthesis and encourages use of fats for fuel
- GH release is regulated by hypothalamic hormones:
- growth hormone-releasing hormone (GHRH)
- growth hormone-inhibiting hormone (GHIH) (somatostatin)
49
homeostatic imbalances of growth hormone
- hypersecretion in children- gigantism
- hypersecretion in adults- acromegaly (after epiphyseal plates have closed)
- hyposecretion in children results in pituitary dwarfism
50
thyroid stimulating hormone (Thyrotropin)
- stimulates the normal development and secretory activity of the thyroid
- TSH release is inhibited by rising blood levels of thyroid hormones that act on the pituitary and hypothalamus -> negative feedback
- increased secretion of thyroid hormones inhibit pituitary gland from secreting TSH hormone which stimulate the thyroid which secretes thyroid hormones!
51
adrenocorticotropic hormone (corticoptropin)
- stimulates the adrenal cortex to release corticosteroids (glucosteroids)
- regulation of ACTH release:
- triggered by hypothalamic corticotropic releasing hormone (CRH) in a daily rhythm
- internal and external factors such as fever, hypoglycemia, and stressors can alter the release of CRH
52
gonadotropins
- follicle stimulating hormone (FSH) and luteinizing hormone (LH)
- secreted by gonadotrophs of the anterior pituitary
- FSH stimulates gamete (egg or sperm) production
- LH promotes production of gonadal hormones (testosterone and progesterone)
- absent from the blood in prepubertal boys and girls
53
prolactin (PRL)
- secreted by lactotrophs of the anterior pituitary
- stimulates milk production in females
- blood levels rise toward the end of pregnancy
- suckling stimulates PRL release and promotes continued milk production
54
when the pancreas releases insulin in direct response to blood glucose, this is an example of ________ stimulation
- humoral*
- neural
- hormonal
- negative feedback
55
receptors for steroid hormones are commonly located ______
- inside the target cell*
- on the plasma membrane of the target cell
- in the blood plasma
- in the extracellular fluid
- all of the above
56
the posterior pituitary
- contains axons of hypothalamic neurons
- neurologically connected to hypothalamus
- stores antidiuretic hormone (ADH) and oxytocin
- ADH and oxytocin are released in response to nerve impulses
57
antidiuretic hormone (ADH)
- hypothalamic osmoreceptors respond to changes in the solute concentration of the blood
- produced in hypothalamus, stored in posterior pituitary
- if solute concentration is high -> ADH is synthesized and released
- ADH targets collecting ducts and inhibits urine formation
- ex. (dehydration) water loss -> high osmotic pressure of blood stimulates hypothalamus -> posterior lobe of pituitary -> ADH secretion -> kidney -> water retention -> osmotic pressure decreases -> inhibits release to hypothalamus
58
oxytocin
- released in significantly higher amounts during childbirth
- stimulates uterine contraction (synthetic oxytocic drugs used to induce labor)
- hormonal trigger for milk ejection
- also acts as neurotransmitter in brain
- considered the cuddling hormone -> promotes bonding and trust
59
thyroid gland
- produces thyroid hormone (T3/T4) and calcitonin
- colloid (thyroglobulin + iodine) stored in the lumen of the follicles and is the precursor of T3/T4
- negative feedback inhibition
- thyroid hormone:
- effects all cells of the body
- increases metabolic rate and heat production
- maintenance of blood pressure
- regulation of tissue growth
- development of skeletal and nervous systems
- reproductive capabilities
60
homeostatic imbalances of TH
hyposecretion- lethargy, feeling chilled, dry skin, sluggish (hoshimotos disease)
- goiter- follicles produce colloid but no iodine, so colloid accumulates
- hypersecretion- nervousness, rapid HR, sweating, weight loss, bulging eyeballs (graves disease)
- exophthalmos- bulging eyes
61
calcitonin
- produced by parafollicular (C) cells
- antagonist to parathyroid hormone (PTH)
- inhibits osteoclast activity and release of Ca2+ from bone matrix
- lowers calcium level in blood
- inhibits calcium absorption into kidneys, intestine
- takes excess calcium and deposits into bones
- bone sparing effect- given to patients with Paget's disease and osteoporosis
62
negative feedback inhibition of thyroid hormones
- hypothalamus secretes thyroid releasing hormone (TRH)
- activates pituitary gland -> secretes thyroid stimulating hormone (TSH)
- activates thyroid gland -> releases T3, T4, calcitonin
63
parathyroid glands
- four to eight tiny glands located behind thyroid (not related)
- promotes increased Ca in the blood -> promotes reabsorption of Ca in kidney and intestine
- contain chief cells that secrete parathyroid hormone (PTH)
- PTH- most important hormone in Ca2+ homeostasis
- Ca homeostasis critical for NN transmission, MM contraction and blood clotting
- low levels of this hormone will result in tetany
- hypocalcemia (low blood Ca2+) stimulates parathyroid glands to release PTH -> PTH activates osteoclasts -> Ca2+ and PO4 released into blood -> PTH increases Ca2+ reabsorption in kidney tubules -> PTH promotes kidney's activation of vitamin D which increases Ca2+ absorption from food
- rising Ca2+ in blood will inhibit PTH release
64
where do we get Ca2+ from
- bone (stimulates osteoclasts)
- kidney (reabsorbs calcium)
- intestine (increases absorption of calcium)
65
adrenal glands
- paired, pyramid-shaped organs atop the kidneys
- structurally and functionally, they are two glands in one
- adrenal cortex- 3 layers of glandular tissue that synthesize and secrete corticosteroids
- adrenal medulla- nervous tissue; part of the sympathetic nervous system
66
adrenal cortex
- 3 layers and the corticosteroids produced
- zona glomerulosa- mineralocorticoids (aldosterone) superficial
- zona fasciculata- glucocorticoids (cortisol) middle layer
- zona reticularis- sex hormones, or gonad corticoids- innermost layer
67
mineralocorticoids (aldosterone)
- zona glomerulosa (superficial layer) secretes mineralocorticoids (aldosterone)
- regulate electrolytes (primarily Na+ and K+) in ECF
- importance of Na+: affects ECF volume, blood volume, blood pressure, levels of other ions
- aldosterone is the most potent mineralocorticoid
- stimulates Na+ reabsorption and water retention by the kidneys
68
glucocorticoids (cortisol)
- zona fasciculata (middle layer) secretes glucocorticoids (cortisol)
- cortisol is the most significant glucocorticoid
- released in response to ACTH patterns of eating and activity, and stress "fight or flight"
- prime metabolic effect is gluconeogenesis- formation of glucose from fats and proteins
- promotes rises in blood glucose, fatty acids, and amino acids
- keep blood sugar levels relatively constant
- maintain blood pressure by increasing the action of vasoconstrictors
- inflammatory response
- immune system
- heightened memory and attention
- decrease sensitivity to pain
- decrease serotonin
- suppresses the immune system
- ideal amounts of glucocorticoids promote normal function, but too much cortisol exerts anti-immune effects
69
cushing syndrome
-increase in glucocorticoid from ACTH-releasing pituitary tumor or from clinical administration of glucocorticoid drugs
70
addison's disease
- deficits in glucocorticoids and mineralocorticoids
- lose weight
- hypotension
- dehydration
71
synthetic corticosteroids (prednisone)
- used in treatment of many diseases with excessive inflammation or overactive immune system
- RA
- MS
- Asthma
- lupus
- joint inflammation
- many side effects- swelling, weight gain, MM weakness, osteoporosis, worsening of DM, cataracts
72
gonadocorticoids (sex hormones)
- most are androgens (male sex hormones) that are converted to testosterone in tissue cells or estrogen in females
- may contribute to:
- the onset of puberty
- the appearance of secondary sex characteristics
- sex drive
73
adrenal medulla (part of ANS)
- chromaffin cells secrete epinephrine (80%) and norepinephrine (20%)
- these hormones cause:
- blood glucose levels to rise
- blood vessels to constrict
- the heart to beat faster
- blood to be diverted to the brain, heart, and skeletal muscle
74
epinephrine
- adrenal medulla
| - stimulates metabolic activities, bronchial dilation, and blood flow to skeletal muscles and the heart
75
norepinephrine
- adrenal medulla
| - influences peripheral vasoconstriction and blood pressure
76
short term stress response
- adrenal medulla stimulated by nerves -> epinephrine and norepinephrine release
- glycogen broken down to glucose - >increased blood glucose
- increased blood pressure
- increased breathing rate
- increased metabolic rate
- change in blood flow patterns, leading to increased alertness and decreased digestive and kidney activity
77
long term stress response
- hypothalamus -> releasing hormone -> anterior pituitary releases ACTH -> adrenal cortex stimulated -> releases mineralocorticoids and glucocorticoids
- MINERALOCORTICOIDS
- retention of sodium ions and water by kidneys
- increased blood volume and blood pressure
- GLUCOCORTICOIDS
- proteins and fats broken down and converted to glucose, leading to increased blood glucose
- immune system may be suppressed
78
a patient is losing weight rapidly sweating profusely and is always anxious. the patient may be suffering from ____
- hypothyroidism
- cretinism
- hyperthyroidism*
- hypersecretion of calcitonin
79
where is the hormone calcitonin produced
- parathyroid gland
- hypothalamus
- anterior pituitary
- thyroid gland*
80
pineal gland
- small gland hanging from the roof of the third ventricle
- pinealocytes secrete melatonin, derived from serotonin
- melatonin may affect:
- timing of sexual maturation and puberty
- day/night cycles
- physiological processes that show rhythmic variations (body temperature, sleep, appetite)
- hypothalamus (biological clock) has many melatonin receptors
- exposure to bright lights resets clock
81
pancreas
- triangular gland behind the stomach
- has both exocrine and endocrine cells
- acinar cells (exocrine)- produce an enzyme-rich juice for digestion
- pancreatic islets (endocrine) (islets of langerhans):
- alpha cells produce glucagon (a hyperglycemic hormone)
- beta cells produce insulin (a hypoglycemic hormone)
82
glucagon
- major target is the liver, where it promotes
- glycogenolysis- breakdown of glycogen to glucose
- gluconeogenesis- synthesis of glucose from lactic acid and noncarbohydrates -> release of glucose to the blood
83
insulin
- lowers blood glucose levels
- enhances membrane transport of glucose into fat and muscle cells
- inhibits glycogenolysis and gluconeogenesis
84
glucose cycle
- increased blood glucose level
- pancreas stimulated to secrete insulin
- stimulates glucose uptake by cells
- inhibits glucose being dumped by the liver
- too little blood glucose -> pancreas secretes glucagon
85
homeostatic imbalances of insulin
- diabetes mellitus (DM) - type 1 or 2
- due to hyposecretion or hypoactivity of insulin
- 3 cardinal signs of DM:
- polyuria- increase urine output
- polydipsia- excessive thirst
- polyphagia- increased hunger and food consumption
86
ovaries and placenta
- gonads and produce steroid sex hormones
- ovaries produce estrogens and progesterone responsible for:
- maturation of female reproductive organs
- appearance of female secondary sexual characteristics
- breast development and cyclic changes in the uterine mucosa
- the placenta secrets estrogens, progesterone, and human chorionic gonadotropin (hCG)
87
testes
- testes produce testosterone that:
- initiates maturation of male reproductive organs
- causes appearance of male secondary sexual characteristics and sex drive
- is necessary for normal sperm production
- maintains reproductive organs in their functional state
88
which hormone is produced in the adrenal medulla
- cortisol
- aldosterone
- epinephrine *
- thyroid hormone
89
which of these is NOT a tropic hormone
- adrenocorticotropic hormone (ACTH)
- follicle-stimulating hormone (FSH)
- luteinizing hormone (LH)
- prolactin (PRL)*
- all of the above
90
low BMR, mental and physical sluggishness is the result of low levels of which hormone
- growth hormone
- thyroid hormone*
- insulin
- ADH
- parathyroid hormone
91
thyroid releasing hormone (TRH)
secreted by the hypothalamus
92
define endocrine gland
-a ductless gland that empties its hormone into the extracellular fluid, from which it enters the blood
