april 25, 2014 – chemical signals and hormones i 1.no pre-lecture quiz 2.cell-to-cell signaling...
TRANSCRIPT
April 25, 2014 – Chemical signals and hormones I
1. No pre-lecture quiz2. Cell-to-cell signaling – an introduction3. Endocrine systems & hormones4. Case study: The importance of thyroid hormones (T3 & T4)
Introduction to chemical signals in animals – Major categoriesEndocrine cells may be organized into glands
Neurotransmitters
Introduction to chemical signals in animals – Major categories
Neuroendocrine pathway
Neuroendocrinesignal
Endocrine pathway Neuroendocrine-to-endocrine pathway
Neuroendocrinesignal
Endocrinesignal
Endocrinesignal
Endocrine cell
Effectorcell
Response
Response
Stimulus Stimulus
Fee
db
ack
inh
ibit
ion
Fee
db
ack
inh
ibit
ion Sensor cell
Effectorcell
Fee
db
ack
inh
ibit
ion
Neural signal
CNS
Stimulus
Sensor cell
Neural signal
CNS
Response
Effectorcell
Endocrine cell
Endocrine systems are regulated by negative feedback
Steroids
CortisolEpinephrine
Amino AcidDerivatives
Receptor
Secretin
Peptides and Polypeptides
Receptor
Receptor
Target cell
Most not lipid soluble;bind to receptors onsurface of target cell
Not lipid soluble;bind to receptors onsurface of target cell
Lipid soluble;bind to receptorsinside target cell
Chemical characteristics of hormones – major classes
Hormone Transport and Action on Target
Hydrophobic messengers pass into cell where they bind with transcription factors which affect gene expression.
Hydrophilic hormones bind to a receptor on the cell membrane which causes several reactions known as a signal transductionpathway. This can affect the properties of enzymes/proteins, etc. or it may affect gene expression.
This picture shows a hormone traveling throughthe cell membrane and binding with a transcription factor.
Which of the following statements are true?
A) This is a membrane soluble (hydrophobic) hormone thatalters gene transcription.
B) This is a membrane soluble (hydrophobic) hormone thatalters immediate enzyme activity and cell processes.
C) This is a membrane insoluble (hydrophilic) hormone thatalters gene transcription.
D) This is a membrane insoluble (hydrophilic) hormone thatalters immediate enzyme activity and cell processes.
Barry Bonds was accused of using a steriod ‘the cream’ to increase his athletic performance. He supposedly applied this to his skin. What does this tell you about the nature of this hormone?
A. The hormone was membrane insoluble.B. The hormone was membrane soluble.C. The hormone initiated a signal transduction pathway.D. A and C
Steroids
Polypeptides
Amino acid derivatives
Major endocrine glands
Figure 47-3-1Hypothalamus
Growth-hormone-releasing hormone:stimulates release of GH from pituitarygland
Corticotropin-releasing hormone (CRH):stimulates release of ACTH from pituitarygland
Gonadotropin-releasing hormone:stimulates release of FSH and LH from pituitary gland
Thyroid-releasing hormone: stimulatesrelease of TSH from thyroid gland
Antidiuretic hormone (ADH): promotesreabsorption of H2O by kidneys
Oxytocin: induces labor and milk releasefrom mammary glands in females
Steroids
Polypeptides
Amino acid derivatives
Figure 47-3-3
Pituitary gland
Thyroid-stimulating hormone (TSH):stimulates thyroid gland to secretethyroxine
Prolactin: stimulates mammary glandgrowth and milk production in females
Follicle-stimulating hormone (FSH)and luteinizing hormone (LH): involvedin production of sex hormones;regulate menstrual cycle in females
Growth hormone (GH): stimulates growth
Adrenocorticotropic hormone (ACTH):stimulates adrenal glands to secreteglucocorticoids
Steroids
Polypeptides
Amino acid derivatives
Figure 47-3-2
Adrenal glands
Thyroid gland
Thyroxine: increases metabolic rateand heart rate; promotes growth
Kidneys
Epinephrine: produces many effectsrelated to short-term stress response
Aldosterone: increases reabsorption ofNa+ by kidneys
Cortisol: produces many effects related toshort-term and long-term stress responses
Vitamin D: decreases blood Ca2+
Testes (in males)
Erythropoietin (EPO): increasessynthesis of red blood cells
Testosterone: regulates developmentand maintenance of secondary sexcharacteristics in males; other effects
Steroids
Polypeptides
Amino acid derivatives
Figure 47-3-4
Parathyroid glands
Pancreas (islets of Langerhans)
Ovaries (in females)
Insulin: decreases blood glucose
Glucagon: increases blood glucose
Estradiol: regulates development andmaintenance of secondary sexcharacteristics in females; other effects
Progesterone: prepares uterus for pregnancy
Parathyroid hormone (PTH): increases blood Ca2+
Steroids
Polypeptides
Amino acid derivatives
Thyroid Hormone
Thyroid hormone:- Actually two hormones (T3/T4)
Mammals mainly secrete T4 - but some T4 is converted under certain circumstances- Same receptor binds both,
but ↑affinity for T3
T3/T4 are membrane soluble- ↑metabolism in muscles, heart, liver & kidney
T4 T3
Thyroid Gland
Low levels of iodine cause ~90% of goiters.Why?
Figure 47-8
T3
Juvenile frog (tadpole)
T3
Locomotion
Respiration
Excretion
Nutrition
Swim via movements of muscular tail
Gas exchange occurs in gills, across skin,and in lungs
Most are herbivorous; have a long gutspecialized for digesting algae and plants
Most nitrogenous wastes excreted asammonia
Adult frog
Locomotion
Respiration
Nutrition
Excretion
Gas exchange occurs across skin, and inlungs
Tailless; walk or hop
Most nitrogenous wastes excreted as urea
Most are carnivorous; have a large mouthor long tongue for catching prey; short gutspecialized for digesting proteins
Researchers figured out that tadpoles could be induced to undergo metamorphosis by feeding them ground up thyroid glands from horses.
They could also prevent metamorphosis by surgically removing the tadpoles' thyroid glands.
In juvenile amphibians, cells respond to increased levels of T3 in one of three ways:
(1) They may begin growing and form new structures, such as legs;(2) They may die, as in cells that form the tadpole's tail; or(3) They may change structure and function.
Researchers figured out that tadpoles could be induced to undergo metamorphosis by feeding them ground up thyroid glands from horses.
They could also prevent metamorphosis by surgically removing the tadpoles' thyroid glands.
In juvenile amphibians, cells respond to increased levels of T3 in one of three ways:
(1) They may begin growing and form new structures, such as legs;(2) They may die, as in cells that form the tadpole's tail; or(3) They may change structure and function.
Take home message: The same hormone can multiple physiological effects
Anadromous versus Resident Stream Sticklebacks
Higher metabolic rates
Migrate from ocean to freshwater to breed
Bigger
Lower metabolic rates
Permanent residents in freshwater
Smaller
Anadromous versus Resident Stream Sticklebacks
Higher metabolic rates
Migrate from ocean to freshwater to breed
Bigger
Lower metabolic rates
Permanent residents in freshwater
Smaller
I-Clicker - Which one has higher levels of thyroid hormone?
A) MarineB) Stream
Kitano, J. et al. 2010. Adaptive divergence in the thyroid signaling pathway in the stickleback radiation. Current Biology 20:2124-2130.
Marine Stream
Does T4 really affect metabolism?
Experiment:
For both marine and stream fish . . .
1. Expose some to higher levels of thyroid (T4)
2. Some unmanipulated (control)
3. Expose some to a thyroid inhibitor
Measure Oxygen Consumption.
Experiment:
For both marine and stream fish . . .
1. Expose some to higher levels of thyroid (T4)
2. Some unmanipulated (control)
3. Expose some to a thyroid inhibitor
Measure Oxygen Consumption inboth marine and freshwater fish.
What are the predictions?
Does T4 really affect metabolism?
Experiment:
Expose some to higher levels of thyroid (T4)
Some unmanipulated (control)
Expose some to a thyroid inhibitor
Does T4 really affect metabolism?
Elevated T4 levels in marine fish were associated with upregulation of genes involved in aerobic metabolism (OXPHOS)
Does T4 really affect metabolism?
There are lots of other elements of the fish that differ, possibly due to thyroid hormone.
-initiation of migration (for marine fish)-activity levels
There are lots of other elements of the fish that differ, possibly due to thyroid hormone.
-initiation of migration-activity levels
-DNA polymorphisms in binding sites of TSH
Altering individual behaviors by altering overall thyroid levels seems like a pretty blunt way to go about changing specific phenotypes.
How could this system be fine-tuned to optimize specific traits under different contexts?
A.) changes in TRH expressionB.) changes in TSH expressionC.) alterations of TSH receptorsD.) alteration of T3/T4 receptors in specific cell types.