Transcript The endocrine system

Honors Anatomy & Physiology
Chapter 16
 act
together to coordinate body’s activities
 both:


use chemical messengers to communicate cell to
cell
major function: homeostasis
 endocrine:


hormones transported thru circulatory system
target cells (any cell with hormone receptor)
anywhere in body
 nervous:


slower response time
quicker conduction of signals
neurotransmitters
act on cells close by
no ducts
 secretions released
and diffuse into blood
capillaries

Endocrine
have ducts
 secretions released
onto surface
 example: sweat
glands, salivary
glands

Exocrine
bind to protein
receptors in cell
membranes (do not
enter cell)
 receptor-hormone
activate enzyme in
cytoplasm  series of
reactions result in
cell response

Peptide
enter cell & bind to
receptor in cytoplasm or
nucleus
 activates transcription
of gene  protein
 generally action slower
than peptide hormone

Steroid
 hormone’s
target is any cell with a receptor
specific for that hormone
 once hormone bound to its receptor  series of
reactions/ gene transcription  action hormone
is known for
 3 necessary factors (besides hormone reception)
1. blood levels of hormone
2. relative #s of receptors
3. affinity (strength)of binding between hormone
& receptor
 low
levels of
hormone will cause
cell to increase #
receptors
 prolonged
exposure
to high hormone
levels causes cell to
decrease # of
receptors
Up-Regulation
Down-Regulation
Humoral stimuli
1.

changing blood levels of an ion, glucose (NOT a
hormone)
Neural stimuli
2.


nerve fibers stimulate hormone release
ex: stress: sympathetic nervous system stimulates
adrenal glands NE, E
Hormonal stimuli
3.

release of hormones is response to rising/falling
levels of other hormones
 sella
turcica
 connected to hypothalamus by infundibulum
 2 lobes:
1. Anterior aka Adenohyophysis
2. Posterior aka Neurohypophysis
 posterior
lobe outgrowth of hypothalamus
 nerve bundle that runs thru infundibulum
called: hypothalamic-hypophyseal tract
makes 2 neurohormones:
1. Oxytocin
2. ADH: antidiuretic hormone aka Vasopressin

 Released:
in response to uterine contractions &
changes in the cervix in early labor(+
feedback loop)
2. breastfeeding
 Actions:
1. increase strength & frequency of
contractions until baby delivered
2. letdown of breastmilk
3. neurotransmitter in brain: “cuddle hormone”
1.
 Released:
Osmoreceptors in hypothalamus monitor solute
concentration of blood: if getting too
concentrated ADH released
2. pain
3. low BP
4. morphine & barbiturates
 Actions:
1. targets renal tubules  reabsorb more water 
concentration of blood returns to normal
2. when large amt ADH(hemorrhage) 
vasoconstriction
 Inhibited by alcohol intake  diuresis
1.
 from
ADH deficiency
 symptoms: intense thirst & large urine output
 Causes:

head trauma
 Treatment:
nothing if patient able to take in adequate fluids
 problem for unconscious or comatose patient

 anabolic

hormone:
metabolic & growth-promoting actions
 Direct
action
Metabolic:
1. mobilizes fats cells for fuel source
2. decreases glucose uptake & metabolism  raises
blood levels (anti-insulin effect)
3. increases a.a. uptake into cells  proteins

 Indirect

action
increases IGFs (insulin-like growth factors) which
stimulate actions needed for growth: nutrient
uptake, making collagen, bone deposition
 hypothalamic
regulation of secretion:
GHRH
1.


growth hormone releasing hormone
also stimulated by ghrelin from stomach
(“hunger hormone”)
GHIH
2.
1.


growth hormone inhibiting hormone
aka somatostatin
triggered by feedback of GH
 usually
caused by pituitary tumor
 treatment: surgical excision of tumor

does not reverse changes
 GH
hypersecretion in childhood
b/4 epiphyseal plates seal  VERY tall
 if continues after plates seal  acromegaly:
“enlarged extremities”
 bones of hands, face, feet continue to grow

 hyposecretion
of GH
 adults:not a problem
 childhood: normal body proportions but short
stature (max 4 ft)
 often other pituitary hormones also affected
which would affect body proportions (TSH) or
failure to mature sexually(FSH, LH)
 GH now commercially available
misused by athletes/elderly for “body building”
 (no evidence it works)
 parents that want their children taller

 thyrotropin:
target is thyroid
 stimulated by TRH thyrotropin releasing
hormone from hypothalamus
 stimulates normal development & secretory
activity of thyroidgland
 release: negative feedback loop
 aka
corticotropin
 secreted in response
to CRH(corticotropin
releasing hormone)
from hypothalamus
 CRH released before
awakening

daily rhythm altered
by: fever,
hypoglycemia,
stressors
 Action:
acts on
adrenal cortex 
cortisol
 absent
in prepubertal boys & girls
 both stimulated by GnRH (gonadotropin
releasing hormone) from hypothalamus in
puberty
 both inhibited by rising levels of gonadal
hormones

1.
2.
Follicle Stimulating
Hormone:
regulates functions of
gonads
stimulates production
of gametes in males &
females
FSH

1.
2.
3.
Luteninizing Hormone:
regulates functions of
hormones
promotes production
of gonadal hormones
in females: works with
FSH in follicle
stimulation and
maturation then LH
triggers ovulation
LH
 protein
hormone similar to GH
 action: stimulates milk production by mammary
glands




role in males unknown
females: levels rise/fall in response to estrogen
levels
in pregnancy: very hi levels 3rd trimester
breastfeeding: baby nursing stimulates release
(+ feedback loop)
 release
controlled by PIH (prolactin inhibiting
hormone), really dopamine
 stimulated
by TSH
 secretes thyroxin (T4) and triiodothyronine
(T3)

(-) feedback inhibition
 both
have similar effects on target cells
2
1.

iodine-containing amine hormones
T4
major one, has 4 iodine atoms
T3
2.


made from T4 in target tissues
has 3 iodine atoms
 causes:
thyroid gland defect lack of TRH, TSH
 Myxedema: symptoms:
1. low metabolic rate
2. feeling cold when others are comfortable
3. constipation
4. thick, dry skin
5. puffy eyes
6. mental sluggishness(not mental retardation)
 enlarged
protruding thyroid gland
 occurs when hypothyroidism caused by lack of
iodine in diet
 severe



hypothyroidism in infants
severe mental retardation
short, disproportioned body
thick tongue and neck
 excessive

secretion of thyroid hormones
Autoimmune disorder
 polypeptide
hormone released by parafollicular
cells of the thyroid
4
small glands embedded in posterior surface of
thyroid gland
 secrete: parathyroid hormone (PTH)

regulated by serum Ca++ levels
 actions:
1.
2.
3.
stimulates removal of Ca++ from bone
increases kidney tubules reabsorption of Ca++
activates Vit D which enhances Ca++
absorption from food
 pyramid
shaped organs perched atop kidneys
 fibrous capsule & cushion of fat for protection
 2 glands in 1 both structurally & functionally
1.
2.
Adrenal Medulla
Adrenal Cortex
 outer
portion of adrenals
 >24 different hormones collectively called
corticostreoids
 cells arranged in 3 zones
1. Zona Glomerulosa
2. Zona Fasiculata
3. Zona Reticularis
 Function:
 regulates
electrolyte (ions) concentrations in
extracellular fluid: especially Na+, K+
1.
Aldosterone:

primary regulator of Na+ and K+ levels


1.
2.
reduces Na+
release stimulated by:
decreasing blood vol
rising K+ levels
 regulates
blood vol & BP by regulating release of
aldosterone  Na+ & water reabsorption in
kidneys
 Mechanism:
1. decreased blood vol / BP  juxtaglomerular
cells of kidney release renin
2. renin triggers reactions that angiotensinogen
 Angiotensin II
3. Angiotensin II  stimulates adrenal cortex to
release aldosterone
 https://www.youtube.com/watch?v=bonQXcA5
Dnc
 https://www.khanacademy.org/science/health-
and-medicine/circulatorysystem/blood_pressure_control/v/generaloverview-of-the-raas-system-cells-and-hormones
 released
from zona fasiculata
 *essential to life:
1.
influence energy metabolism of most body cells
helps resist stress
 Cortisol
(hydrocortisone)
 steroid hormone modifies gene activity in
target cells
 normal
amounts promote normal function
 too much  significant anti-inflammatory&
anti-immune effects:
1. depress immune system
2. inhibits inflammation by decreasing release
of inflammatory chemicals
3. disrupts normal cardiovascular, neural, & GI
function
4. depresses cartilage & bone formation
 from
zona reticulata
 2 weak male sex hormones
 contribute to dev. of axillary & pubic hair
 some converted to stronger hormones (T) in
tissue cells others to estrogens(E)

1.
2.
account for release of E after female menopause
DHEA (dehydroepiandrosterone
Androstenedione
 part
of the sympathetic nervous system
 3rd
ventricle roof
 secretes melatonin
amine hormone, derived from serotonin
 blood levels rise & fall in response to diurnal cycle
 peak levels occur during night  drowsiness/
lowest levels ~12 noon

Insulin
1.



protein
reduces blood glucose by increasing entry of
glucose into cells/making glycogen in
hepatocytes
regulated by blood glucose levels
Glucagon
2.



protein
raises blood glucose by acting on glycogen
stores in liver
regulated by blood glucose levels
 endocrine
portion of
pancreas
 Alpha cells
 glucagon
 Beta cells
 insulin
 Delta cells
 somatostatin
 NOT



required for glucose to enter:
brain tissue
liver
kidney
 Insulin
1.
2.
3.
binding to receptor triggers:
catalyze oxidation of glucose  ATP
join glucose molecules together  glycogen
converts glucose to fat (especially in adipose
tissue)
1.
2.
3.

elevated blood glucose
increasing blood levels of amino acids &
fatty acids
release of ACh by parasympathetic fibers
as glucose is taken up by cells blood levels
decrease  beta cells stop secreting
 https://www.youtube.com/watch?v=C9XYnZdE
IPE
 upper
thorax, posterior
to sternum
 largest in infants,
decreases as we age
 produces: thymosin –
programs T cells
 produce
steroid sex hormones
 regulated by gonadotropins from pituitary
FSH
 LH

testes  testosterone
 Female: ovaries  estrogen & progesterone

placenta: secretes steroid & protein
hormones that support fetus
 Male:
 paired
 site
oval organs suspended in scrotum
of:
spermatogenesis
 production of androgens:
1. Testosterone major one
 made by interstitial cells/stimulated by FSH
& LH
 produces male 2◦ sex characteristics in
puberty
 promotes growth & maturation of
reproductive system organs
 increases libido

 paired,
almond-shaped organs in pelvic
cavity
 produce ova
 release: estrogens & progesterone
 begin functioning in puberty in response to
anterior pituitary gonadotrophins
 Estrone
&Estradiol made by follicle where
ova is maturing
 stimulate:

development of 2◦ sex characteristics
 work
with progesterone to prepare uterine
lining for implantation
 help maintain pregnancy & prepare breasts
to lactate(those estrogens made in placenta)
 made
&secreted by corpus luteum
 acts with estrogen to prepare uterine lining
for implantation
 quiets uterine muscle during early
pregnancy
 helps prepare breasts for lactation
 produces
hCG (human Chorionic
Gonadotropin)




stimulates corpus luteum of ovary to continue
producing estrogens and progesterone so lining
of uterus does not slough off (like in
menstruation)
turns pregnancy tests +
by 3rd mo pregnancy placenta produces estrogen
& progesterone (ovaries become inactive rest of
pregnancy)
also produces hPL (human placental lactogen)
works w/E & P in preparing breasts for
lactation