Download The Endocrine Sytem

The Endocrine Sytem

Second controlling system of the body
◦ Nervous system is the fast-control system
Uses chemical messengers (hormones)
that are released into the blood
 Hormones control several major
processes

◦
◦
◦
◦
◦
Reproduction
Growth and development
Mobilization of body defenses
Maintenance of much of homeostasis
Regulation of metabolism
Pineal gland
Hypothalamus
Pituitary gland
Thyroid gland
Parathyroid glands
Thymus
Adrenal glands
Pancreas
Ovary (female)
Testis (male)
Figure 9.3
Chemical Make-up

Hormones are classified chemically as
◦ Amino acid–based, which includes
 Proteins
 Peptides
 Amines
◦ Steroids—made from cholesterol
◦ Prostaglandins—made from highly active lipids
Mechanisms of Hormone Action
Hormones affect only certain tissues or
organs (target cells or target organs)
 Target cells must have specific protein
receptors
 Hormone-binding alters cellular activity

Steroid
hormone
Nucleus
Cytoplasm
1
Receptor
protein
2
3
Hormonereceptor complex
4
DNA
mRNA
5
New
protein
Plasma
membrane
of target
cell
6
(a) Steroid hormone action
Figure 9.1a
Nonsteroid
hormone (first
messenger)
Cytoplasm
Enzyme
ATP
3
1
2
Receptor
protein
Plasma
membrane
of target cell
Second
cAMP messenger
4
Effect on cellular function,
such as glycogen
breakdown
(b) Nonsteroid hormone action
Figure 9.1b
Control of Hormone Release
Hormone levels in the blood are mostly
maintained by negative feedback
 A stimulus or low hormone levels in the
blood triggers the release of more
hormone
 Hormone release stops once an
appropriate level in the blood is reached

Hormonal Stimuli of Endocrine Glands
Most common stimuli
 Endocrine glands are activated by other
hormones

Releasing hormones
secreted into portal
circulation
Hypothalamus
Anterior pituitary
Posterior pituitary
Hypophyseal
portal system
Adrenocorticotropic
hormone (ACTH)
Growth hormone (GH)
Bones and muscles Prolactin (PRL) Follicle-stimulating Thyrotropic
hormone (TH)
hormone (FSH)
and luteinizing
Mammary
hormone (LH)
glands
Thyroid
Adrenal cortex
Testes or ovaries
© 2012 Pearson Education, Inc.
Figure 9.4
Optic
chiasma
Axon
terminals
Hypothalamic
neurosecretory
cells
Hypothalamus
Arterial blood supply
Posterior lobe
Capillary bed
Venous drainage
Anterior lobe
of the pituitary
© 2012 Pearson Education, Inc.
ADH
Oxytocin
Kidney tubules
Mammary glands
Uterine muscles
Figure 9.6
Hypothalamus
Part of the brain that sits above the pituitary
They work together
Anterior Pituitary
1. Growth hormone
2. Adrenocorticotropic hormone - ACTH
3. Thyroid stimulating hormone - TSH
Posterior Pituitary
1. Antidiruetic hormone (ADH) – promotes
re-absorption of water in kidney –
increases BP
2. Oxytocin – uterine contractions


Adrenal Glands
Respond to ACTH by producing:
1. Glucocorticoids (cortisone) – produce
glucose in blood through fatty acid
breakdown, inhibit inflammation.
2. Mineralocorticoids (aldosterone) –
promote uptake of sodium and chloride
in kidneys, water follows, increase BP
3. Epinephrine - emergency hormone

Decreased Na+ or
increased K+ in
blood
Stress
Hypothalamus
Decreased
blood volume
and/or blood
pressure
Corticotropinreleasing hormone
Anterior pituitary
Increased
ACTH blood pressure
or blood volume
Kidney
Renin
Indirect
stimulating
effect via
angiotensin
Angiotensin II
Direct
stimulating
effect
Heart
Atrial natriuretic
peptide (ANP)
Inhibitory
effect
Mineralocorticoidproducing part of
adrenal cortex
Enhanced secretion
of aldosterone targets
kidney tubules
© 2012 Pearson Education, Inc.
Increased absorption
of Na+ and water;
increased K+ excretion
Increased blood
volume and
blood pressure
Figure 9.12
Short term
Stress
More prolonged
Hypothalamus
Releasing hormones
Nerve impulses
Spinal cord
Corticotropic cells of
anterior pituitary
Preganglionic
Adrenal sympathetic
medulla fibers
ACTH
Adrenal
cortex
Mineralocorticoids Glucocorticoids
Short-term stress response
Catecholamines 1. Increased heart rate
2. Increased blood pressure
(epinephrine and
3. Liver converts glycogen
norepinephrine)
to glucose and releases
glucose to blood
4. Dilation of bronchioles
5. Changes in blood flow
patterns, leading to
increased alertness and
decreased digestive and
kidney activity
6. Increased metabolic rate
© 2012 Pearson Education, Inc.
Long-term stress response
1. Retention of sodium 1. Proteins and fats
converted to
and water by kidneys
glucose or broken
2. Increased blood
down for energy
volume and blood
2. Increased blood
pressure
sugar
3. Suppression of
immune system
Figure 9.13
Thyroid
Stimulated by Thyrotropin releasing hormone
(TRH) from the hypothalamus which stimulates
TSH from anterior pituitary.
1. Thyroxine (iodine)
 Maintains metabolism
 Hyperthyroidism – high metabolic rate, nervous,
irritable
 Hypothyroidism – low met. Rate, slow, sluggish,
overweight
2. Calcitonin – takes up calcium from blood to
bones

Disorders of the endocrine system
Goiter – iodine deficiency, thyroxin
production declines
 The hypothalamus secretes TRH, but has
no effect
 Results in enlargement of the thyroid
 Grave’s disease – antibodies in the
immune system mistakenly bind to TSH
receptors on the thyroid gland stimulating
more thyroxin production hyperthyroidism

Parathyroids
Rest on the thyroid
1. Parathyroid hormone – releases calcium
from bone to blood
 Opposite of calcitonin
 Bone remodeling

Calcitonin
Calcitonin
stimulates
calcium salt
deposit in bone.
Thyroid gland
releases calcitonin.
Stimulus
Rising blood
Ca2+ levels
Calcium homeostasis of blood: 9–11 mg/100 ml
BALANCE
BALANCE
Stimulus
Falling blood
Ca2+ levels
Thyroid
gland
Osteoclasts
degrade bone
matrix and
release Ca2+
into blood.
Parathyroid
glands
PTH
Parathyroid
glands release
parathyroid
hormone (PTH).
Figure 9.10
Bone growth
Bone grows in
length because:
1 Cartilage
grows here.
2 Cartilage
is replaced
by bone here.
3 Cartilage
grows here.
4 Cartilage
is replaced by
bone here.
© 2012 Pearson Education, Inc.
Bone remodeling
Growing shaft is
remodeled as:
Articular cartilage
Epiphyseal plate
1 Bone is
resorbed here.
2 Bone is added
by appositional
growth here.
3 Bone is
resorbed here.
Figure 5.6
Pancreas
Islets of Langerhans – produce insulin and
glucagon
1. Glucagon stimulates glycogen to break
into glucose molecules and be released
into the blood
2. Insulin decreases the glucose in the
blood

Uptake of glucose
from blood is
enhanced in most
body cells
Insulin-secreting cells
of the pancreas
activated; release
insulin into the blood
Insulin
Tissue cells
Glucose Glycogen
Pancreas
Elevated blood
sugar level
Liver takes up
glucose and stores
as glycogen
Stimulus
Blood
glucose level
(e.g., after
eating four
jelly doughnuts)
Stimulus
Blood glucose
level (e.g., after
skipping a meal)
Blood glucose rises
to homeostatic
set point; stimulus
for glucagon
release diminishes
Liver breaks
down glycogen
stores and
releases
glucose to the
blood
Blood glucose
falls to homeostatic
set point; stimulus
for insulin release
diminishes
Low blood sugar level
Glucagon-releasing
cells of pancreas
activated; release
glucagon into blood
Glucose Glycogen
Liver
Glucagon
Figure 9.15
thermoregulation
Ectotherm vs. endotherm
 Cooling by evaporation
 Warming by metabolism – shivering and
metabolizing fat
 Vasodilation and vasoconstriction of blood vessels
Ex. In hot environments, animals increase blood
flow to their ears to release heat and in cold do
the opposite.
 Countercurrent exchange – warm blood is
traveling to extremities.
 Hibernation, blubber, hair, basking,…

Reproductive Systems
Female
 Ovaries – produce eggs (ova) and secrete
estrogen and progesterone
 Stimulated by FSH and LH
 Male
 FSH – stimulates sperm production
 LH – stimulates interstitial cells to
produce testosterone

Suspensory
ligament of ovary
Uterine (fallopian) tube
Ovarian
blood
vessels
Broad
ligament
Fundus
Lumen (cavity)
of uterus of uterus
Ovary
Infundibulum
Fimbriae
Ovarian ligament
Body of
uterus
Ureter
Uterine blood
vessels
Uterosacral
ligament
Cervix
Uterine
tube
Round ligament of uterus
Endometrium
Myometrium Wall of
Perimetrium uterus
Cervical canal
Vagina
(b)
Figure 16.8b
Menstrual Cycle
Phase 1
Follicular phase (10 days)
 Anterior pituitary secretes FSH and LH
 FSH – follicle stimulating hormone
 LH – luteinizing hormone
 Follicle grows – releases estrogen which
causes uterine lining to thickenendometrium
 Estrogen also causes ant. Pit. To release LH
 The luteal surge causes ovulation
Growing follicles
Primary follicle
Degenerating
corpus luteum
Blood
vessels
Antrum
Corona
radiata
Mature vesicular
(Graafian) follicle
Germinal
epithelium
Corpus luteum
Developing
corpus luteum
Ruptured
follicle
Ovulation
Secondary oocyte
Figure 16.7
Ovulation – release of the egg from the
ovary ends the follicular phase.
 Ova floats into fallopian tube (oviduct)

Phase 2
Luteal phase
 Follicle has released the egg and changes
into the corpus luteum
 Corpus luteum continues to secrete
estrogen and now begins to produce
progesterone
 Progesterone increases vessels and glands in
uterus
 After about 13-15 days, if fertilization and
implantation have NOT occurred the corpus
luteum shuts down
Phase 3
Menstruation
 Uterus reabsorbs some of the tissue
created in the endometrium
 The rest sheds off and is passed out of
the body
Male Reproductive system
Ureter
Urinary bladder
Prostatic urethra
Pubis
Seminal vesicle
Ampulla of
ductus deferens
Membranous urethra
Ejaculatory duct
Rectum
Prostate
Bulbourethral gland
Urogenital diaphragm
Erectile tissue
of the penis
Spongy urethra
Shaft of the penis
Ductus (vas) deferens
(a)
Epididymis
Testis
Scrotum
Glans penis
Prepuce
External urethral
orifice
Figure 16.2a