Download Chapter 26 Hormones and the Endocrine System

Chapter 26 Hormones and the Endocrine System
Hypothalamus
The Nature of
Chemical Regulation
Hormones affect cells using
two distinct mechanisms.
Hormones and
Homeostasis
The hypothalamus exerts
master control over many
other endocrine glands.
The Vertebrate
Endocrine System
Hormone, often in antagonistic pairs,
regulate whole-body processes.
Chemical signals coordinate body functions
內分泌系統
 The endocrine system
- consists of all hormone-secreting cells.
- works with the nervous system in regulating body activities.
神經系統
 The nervous system also
- communicates, regulates, and uses electrical signals via nerve cells.
 Comparing the endocrine and nervous systems
- the nervous system reacts faster.
- the responses of the endocrine system last longer
內分泌腺
荷爾蒙
 Hormones are chemical signals, produced by endocrine glands,
usually carried in the blood, and responsible for specific changes
target cells.
Hormone from an endocrine cell
Secretory vesicles
Endocrine
cell
Hormone
molecules
Blood
vessel
Target cell
Exocrine gland vs. Endocrine gland
Hormone-secreting
cells
Neurotransmitter from a nerve cell
Nerve cell
Nerve
signals
Neurotransmitter
molecules
Nerve cell
The neurosecretory cell 神經內分泌細胞
Comparison between nervous system
and endocrine system
Hormones affect target cells using
two main signaling mechanisms
Two major classes of molecules function as hormones in vertebrates.
(1) The first class includes hydrophilic (water-soluble),
amino-acid-derived hormones. Among these are
- proteins.
- peptides (3-30 amino acids).
- amines (modified versions of single amino acids).
固醇類激素(荷爾蒙)
(2) The second class of hormones are steroid hormones, which
include small, hydrophobic molecules made from cholesterol.
膽固醇
 Hormone signaling involves three key events:
- reception.
- signal transduction.
- response.
Types of hormones (1)
(1) Peptides and proteins
(2) Amines
(3) Steroids
Types of hormones (2)
Types of hormones (3)
A hormone’s concentration in the plasma depends upon
(1) its rate of secretion by the endocrine glands
(2) its rate of removal from the blood
A hormone that binds a plasma membrane receptor
Interstitial fluid
Water-soluble
hormone
Receptor
protein
1
Plasma
membrane
Target cell
2
An amino-acid-derived hormone
binds to plasma-membrane receptors
on target cells and initiates a
signal transduction pathway.
Signal
transduction
pathway
Relay
molecules
3
Cytoplasmic
response
Cellular responses
or
Gene regulation
Nucleus
Activation
Repression
A hormones that binds an intracellular receptor
Interstitial fluid
Steroid
hormone
1
A steroid hormone can
diffuse through plasma membranes,
bind to a receptor protein in the
cytoplasm or nucleus, and form a
hormone-receptor complex that
carries out the transduction of the
hormonal signal.
Target cell
2
Receptor Cytoplasma
protein Nucleus
Nucleus
3
Hormonereceptor Gene
complex Gene
DNA
4
Transcription
mRNA
New
protein
Cellular response:
activation of a gene and
synthesis of new protein
activator
repressor
The vertebrate endocrine system consists of more than
a dozen major glands
 Some endocrine glands (such as the thyroid) primarily secrete
hormones into the blood.
 Other glands (such as the pancreas) have endocrine and
nonendocrine functions.
 Other organs (such as the stomach) are primarily nonendocrine but
have some cells that secrete hormones.
The major endocrine glands in humans
甲狀腺
Thyroid gland
下視丘
Hypothalamus
Pituitary gland
腦下垂體
副甲狀腺
Parathyroid glands
(embedded within
thyroid)
胸腺
Thymus
腎上腺
Adrenal glands
(atop kidneys)
胰臟
Pancreas
Other hormone-secreting structures:
Heart
Liver
Stomach
Pineal gland 松果體
卵巢
Ovaries
(female)
睪丸 Testes
(male)
Human endocrines glands and some of their hormones
Human endocrines glands and some of their hormones
松果體
The pineal gland
- is pea-sized, located near the center of the brain.
褪黑激素
- secretes melatonin, a hormone that links environmental light
conditions with biological rhythms.
 The thymus gland
- lies above the heart, under the breastbone, and
- secretes a peptide that stimulates the development of T-cells.
The hypothalamus, which is closely tied to the pituitary,
connects the nervous and endocrine systems
 The hypothalamus
- blurs the distinction between endocrine and nervous systems
- receives input from nerves about the internal conditions of the body
and the external environment.
- responds by sending out appropriate nervous or endocrine signals.
- uses the pituitary gland to exert master control over the endocrine
system. The pituitary gland consists of two parts.
腦垂體後葉
The pituitary gland
 The posterior pituitary
- is composed of nervous tissue.
- is an extension of the hypothalamus.
抗利尿激素
催產素
- stores and secretes oxytocin and ADH.
which are made in the hypothalamus.
 The anterior pituitary
腦垂體前葉
- synthesizes and secretes hormones that control the activity
of other
glands.
- is controlled by two types of hormones released from the
hypothalamus:
(1) releasing hormones stimulate the anterior pituitary.
(2) inhibiting hormones inhibit the anterior pituitary.
生長激素
 Pituitary secretions include
- growth hormone (GH) that promotes protein synthesis and
腦內啡
the
甲狀腺促素釋素
use of body fat for energy metabolism.
甲狀腺素
painkillers.
- endorphins that function as natural
Location of the hypothalamus and pituitary
Brain
Location of the hypothalamus and pituitary
Hypothalamus
Posterior pituitary
Anterior pituitary
Bone
Hormones of the posterior pituitary
Hypothalamus
Neurosecretory
cell
Hormone
Posterior
pituitary
Blood
vessel
催產素
Oxytocin
Anterior
pituitary
ADH
ADH: antidiuretic hormone 抗利尿激素
= Vasopressin 血管加壓素
Uterine muscles
Mammary glands
Kidney
tubules
Hormones of the anterior pituitary
Neurosecretory
cell of hypothalamus
releasing hormones
inhibiting hormones
Blood
vessel
Releasing hormones
from hypothalamus
TSH
ACTH
TSH: thyroid-stimulating hormone
促甲狀腺激素
ACTH: adrenocorticotropic hormone
促腎上腺皮質激素
Endocrine cells of
FSH: follicle-stimulating hormone
the anterior pituitary
濾泡刺激素
LH: luteinizing hormone
促黃體激素
Pituitary hormones
PRL: prolactin
泌乳激素
GH: Growth hormone
生長激素
FSH
Prolactin
Growth
Endorphins
and
(PRL)
hormone
Endophines 腦內啡
LH
Thyroid
Adrenal
cortex
Testes or
ovaries
(GH)
Mammary
glands
(in mammals)
Entire
body
Pain
receptors
in the brain
Targets and major functions of the six classical
anterior pituitary gland hormone
Growth hormone
somatotropin
Gonadotropic hormones
gonadotropins
Follicle-stimulating
hormones
Thyroid-stimulating
hormone
thyrotropin
Luteinizing
hormone
T4
T3
-lipotropin →→ mobilize fats in the circulation
-endrophin →→ pain-killing
Adrenocorticotropic
hormone
corticotropin
The hypothalamic-anterior pituitary gland system
Gonadotropin-releasing
Growth-hormone
hormone
-releasing hormone
TSH-releasing hormone
Somatostatin
= Growth-hormoneInhibiting hormone (GHIH)
Corticotropin-releasing
hormone
Dopamine
The hypothalamic-anterior pituitary gland system
Excessive production of growth hormone
Acromegaly肢端肥大症
adult
Gigantism巨人症
childhood
Pituitary dwarfism
侏儒症
The thyroid regulates development and metabolism
The thyroid gland is located in the neck,
just under the larynx (voice box).
 The thyroid gland produces two similar hormones
- thyroxine (T4).甲狀腺素
- triiodothyronine (T3).三碘甲狀腺素
The maturation of a tadpole (below)
 These hormones regulate many aspects of
into an adult frog (above),
as regulated by thyroid hormones.
- metabolism.
- reproduction.
- development.
Control of thyroxine secretion
Hypothalamus
Inhibition
TRH (TSH-releasing hormone)
Anterior
pituitary
甲狀腺促進素釋素
Inhibition
TSH (Thyroid-stimulatory hormone)
甲狀腺促進素
Thyroid
Thyroxine
甲狀腺素
Hyperthyroidism
 Hyperthyroidism甲狀腺亢進
- results from too much T4 and T3 in the blood.
- leads to high blood pressure, loss of weight, overheating,
and irritability.
- produces Graves’ disease.
葛瑞夫茲病
Hypothyroidism
 Hypothyroidism 甲狀腺功能低下
- results from too little T4 and T3 in the blood.
- leads to low blood pressure, being overweight,
and often feeling cold and lethargic.
Dwarfism
Cretinism 呆小症
I.
II.
III.
Hypopituitarism
 GH
Short stature, smart look
Proportionate body parts
IV.
Mentally normal
(IQ normal)
Sexual infantilism
V.
Cretinism
Hypothyroidism
 T4, T3
Short stature, ugly look
Disproportionately small
body parts
Mentally retarded
(low IQ)
Sexual infantilism
small gonads
甲狀腺腫
 Iodine deficiency can produce a goiter, an enlargement of the thyroid.
 In this condition, the thyroid gland cannot synthesize adequate
amounts of T4 and T3, and the thyroid gland enlarges.
No inhibition
Hypothalamus
TRH
No inhibition
Anterior
pituitary
TSH
Thyroid
No iodine
Insufficient
T4 and T3
produced
Thyroid grows
to form goiter
Goiter, a symptom of iodine deficiency,
in a Burmese woman
How iodine deficiency causes goiter
Hormones from the thyroid and parathyroid glands
maintain calcium homeostasis
 Blood calcium level is regulated by antagonistic hormones
each working to oppose the actions of the other hormone:
- calcitonin, from the thyroid, lowers the calcium level in the blood,
抑鈣素
- parathyroid
hormone (PTH), from the parathyroid glands, raises
副甲狀腺素
the calcium level in the blood.
Ca2+ homeostasis
8
7
Calcitonin
Thyroid
gland
releases
calcitonin
Stimulates
Ca2 deposition
in bones
Reduces
Ca2 reabsorption
in kidneys
9
6
Stimulus:
Rising
blood Ca2
level
(imbalance)
Blood Ca2 falls
Ca2
level
Homeostasis: Normal blood
calcium level (about 10 mg/100 mL)
Ca2
level
Stimulus:
Falling
blood Ca2
level
(imbalance)
1
Blood Ca2 rises
Parathyroid
glands
release parathyroid
hormone (PTH)
5
Stimulates
Ca2 release
from bones
2
3
PTH
Active
vitamin D
Increases
Ca2 uptake
in intestines
4
Increases
Ca2
reabsorption
in kidneys
Parathyroid
gland
Tetany 手足搐搦症,手足強直
A shortage of PTH cause the blood calcium level to drop dramatically,
leading to convulsive contractions of the skeletal muscles.
Pancreatic hormones regulate blood glucose levels
The pancreas secretes two hormones that control blood glucose:
- insulin
signals cells to use and store glucose.
胰島素
- glucagon causes cells to release stored glucose into the blood.
昇糖素
Somatostatin
Insulin Glucagon
Glucose homeostasis
Insulin
Body
cells
take up more
glucose
3
Storage of energy in fats
Synthesis of proteins
2
Beta cells
of pancreas stimulated
to release insulin into
the blood
1
4
High blood
glucose level
Stimulus:
Rising blood glucose
level (e.g., after eating
a carbohydrate-rich
meal)
Blood glucose level
declines to a set point;
stimulus for insulin
release diminishes
Liver takes
up glucose
and stores it as
glycogen
Glucose
level
Homeostasis: Normal blood glucose level
(about 90 mg/100 mL)
Glucose
level
Stimulus:
Declining blood
glucose level
(e.g., after
skipping a meal)
5
Blood glucose level
rises to set point;
stimulus for glucagon
release diminishes
8
6
Liver
breaks down
glycogen and
releases glucose
to the blood
7
Glucagon
Alpha
cells of
pancreas stimulated
to release glucagon
into the blood
Low blood
glucose level
Diabetes is a common endocrine disorder
“to flow, honey”
 Diabetes
mellitus affects about 8% of the U.S. population,
糖尿病
and results from a
- lack of insulin. (type 1)
- failure of cells to respond to insulin. (type 2)
 Both genetic and environmental factors appear to be important.
Type 1 diabetes (insulin-dependent)
 Type 1 (insulin-dependent) diabetes is
- an autoimmune disease.
- caused by the destruction of insulin-producing cells.
Type 2 diabetes (non-insulin-dependent)
 Type 2 (non-insulin-dependent) is
- caused by a reduced response to insulin.
- associated with being overweight and underactive.
- the cause of more than 90% of diabetes.
Type 3 diabetes (Gestational diabetes)
 Gestational diabetes 妊娠糖尿病
- can affect any pregnant woman (4% of pregnant women)
- lead to dangerously large babies, which can complicate delivery.
Glucose tolerance test
If the blood glucose level exceeds 200 mg/100 mL 2 hours after eating, the person has diabetes.
Results of glucose tolerance tests
Blood glucose (mg/100 mL)
葡萄糖耐受性測試
400
350
300
Diabetic
250
200
150
Healthy
100
50
0
0
1
2
1
2
3
Hours after glucose ingestion
4
5
The adrenal glands mobilize responses to stress
 The endocrine system includes two adrenal glands, sitting on top of
each kidney.
 Each adrenal gland is made of two glands fused together, the
- adrenal medulla.
- adrenal cortex.
 Both glands secrete hormones that enable the body to respond to
stress.
Hormones from the the adrenal glands
 Nerve signals from the hypothalamus stimulate the adrenal medulla to
secrete
- epinephrine (adrenaline). 腎上腺素
- norepinephrine (noradrenaline). 正腎上腺素
 These hormones quickly trigger the “fight-or-flight” responses, which
are short-term responses to stress.
促腎上腺皮質激素
 Adrenocorticotropic hormone (ACTH) from the pituitary causes the
adrenal cortex to secrete
- glucocorticoids.葡萄糖皮質素
Magic bullet
美國仙丹
- mineralocorticoids.礦物性皮質素
 The effects of these hormones cause
long-term responses to stress.
How the adrenal glands control our responses to stress
Adrenal
medulla
Adrenal
gland
Adrenal
cortex
Stress
Nerve
signals
1
Hypothalamus
3
Kidney
Releasing hormone
Cross section of
spinal cord
Anterior pituitary
Nerve cell
4
Nerve cell
Blood vessel
“corticosteroids”
steroid hormones
ACTH
5
Adrenal medulla
Adrenal
cortex
ACTH
Adrenocorticotropic
hormone
2
Epinephrine and
norepinephrine
fight-or-flight
Short-term stress response
Mineralocorticoids
rapid
Long-term stress response
1. Glycogen broken down to glucose;
increased blood glucose
2.
3.
4.
5.
Increased blood pressure
Increased breathing rate
Increased metabolic rate
brain↑
Change in blood flow patterns,
leading to increased alertness and skeletal
decreased digestive and kidney activity
Glucocorticoids
muscles ↑
slower
Mineralocorticoids
Glucocorticoids
1. Retention of sodium
ions and water by
kidneys
2. Increased blood
volume and blood
pressure
1. Proteins and fats
broken down and
converted to glucose,
leading to increased
blood glucose
2. Immune system may
be suppressed
醛固酮 aldosterone
cortisone 可體松
The gonads secrete sex hormones
 Steroid sex hormones
- affect growth.
- affect development.
- regulate reproductive cycles and sexual behavior.
 Sex hormones
include
動情激素
- estrogens, which maintain the female reproductive system and
promote
the development of female characteristics.
黃體素
- progestins, such as progesterone, which prepare and maintain the
uterus to support a developing
embryo.
男性賀爾蒙
睾丸固酮
- androgens, such as testosterone, which stimulate the
development and maintenance of the male reproductive system.
 The synthesis of sex hormones by the gonads is regulated by the
- hypothalamus.
- pituitary.
Male elephant seals in combat
Androgen in sex determination
A single hormone can perform a variety of functions
in different animals
泌乳激素
 The peptide hormone prolactin (PRL) in humans stimulates
mammary glands to grow and produce milk during late pregnancy.
 Suckling by a newborn stimulates further release of PRL.
High PRL during nursing inhibits ovulation.
 PRL has many roles unrelated to childbirth, suggesting that PRL is an
ancient hormone diversified through evolution.
- In some nonhuman mammals, PRL stimulates nest building.
- In birds, PRL regulates fat metabolism and reproduction.
- In amphibians, PRL stimulates movement to water.
- In fish that migrate between salt and fresh water, PRL helps regulate
salt and water balance.
Sucking promotes prolactin production