Set 3 (Part II) Flashcards
What do some cells use as a second messenger of cAMP? What is activated?
- Calcium
- Phospholipase C
How does oxytocin trigger myometrial contractions?
Through the Phospholipase C pathway
Describe the phospholipase C pathway.
- Binding of messenger to receptor activates a G-protein
- Phospholipase C is activated and converts PIP2 to DAG and IP3
- IP3 mobilizes intracellular calcium stores and releases it into the cytoplasm
- Activation of calmodulin, which induces protein to change shape
- Cellular response
What stimuli cause hormone secretion?
- Nervous (stress)
- Ion levels (ex: calcitonin, parathyroid, aldosterone)
- Other hormones
- Environment
How is hormonal secretion usually controlled?
- Negative feedback loop
- Output of a system counteracts a change in input
What is the simplest mechanism of hormone regulation?
When an endocrine gland is sensitive to the physiological changes produced by its target cells
Explain the mechanisms that occur when the plasma concentration of thyroid hormones fall.
- Hypothalamus releases TRH
- Anterior pituitary releases TSH
- Thyroid releases thyroid hormones
- Thyroid hormones signal the hypothalamus to shut off the release of TRH
What is the stimulation for release of parathyroid hormone (PTH)?
Decrease in blood calcium
What is the action of parathyroid hormone?
- Stimulates osteoclasts in bone to release more calcium from storage in bone tissue
- Stimulates the release of calcitriol from bone
What is an example of a short feedback loop? How?
- Parathyroid hormone in response to low calcium levels
- Each parathyroid gland is senses to changes in the physiological variable its hormone regulates
What is the stimulation for release of calcitonin?
Increased calcium in the blood
What is the action of calcitonin?
- Stimulates calcium uptake by bone (osteoblasts)
- Decreases blood calcium
What is the stimulation for release of calcitriol?
Parathyroid hormone (PTH)
Why do new mothers need to watch their calcium intake?
Because the process of lactation decreases calcium stores
Where is the pituitary gland located?
- In a well-protected location in the brain
- Located on the ventral surface of the brain within the skull
- Difficult to access
What is the infundibulum?
Stem-like stalk that connects the pituitary to the hypothalamus
What is the neurohypophysis?
- Posterior pituitary
- Extension of the nervous system
What is the adenohypophysis?
- Anterior pituitary
- True thyroid gland
What is the function of the hypophyseal portal system?
- Allows deoxygenated blood to be carried down with the hormones produced by the hypothalamus
- Are shuttled directly to the anterior pituitary
- Faster, more direct communication
What does the hypophyseal portal system relay?
Hypothalamus and anterior pituitary
Where are the posterior pituitary hormones produced? What is its function?
- Produced in the hypothalamus
- Only responsible for storage
What are the two hormones released by the posterior pituitary?
- Antidiuretic hormone (ADH): acts on kidney tubules
- Oxytocin: acts on uterus smooth muscle and mammary glands
What are the two divisions of the anterior pituitary?
- Pars anterior: forms the major portion
- Pars intermedia
What is the tissue of the anterior pituitary composed of? What kind of cell? What kind of connective tissue? How is it vascularized?
- Irregular clumps of secretory cells
- Fine connective tissue fibers
- Surrounded by a rich vascular network
What do somatotrophs secrete?
Growth hormone
What do corticotrophs secrete?
- ACTH
- Melanocyte-stimulating hormone (MSH)
What do thyrotrophs secrete?
TSH (thyroid-stimulating hormone)
What do lactotrophs secrete?
Prolactin
What do gonadotrophs secrete?
- LH
- FSH
Describe hormone release by the anterior pituitary.
- Neurons synthesize trophic hormones and release into portal system
- Endocrine cells release their hormones into the second set of capillaries for distribution to the rest of the body
How does growth hormone work? What does it stimulate? What is it produced by?
- Produced by somatotrophs
- Promotes growth by stimulating the liver to produce growth factors, which in turn accelerate amino acid transport into cells
How does growth hormone promote growth of bone, muscle, and other tissue?
- Accelerating amino acid transport into the cells
- All processes involve protein anabolism
Why does growth hormone produce a hyperglycemic effect?
- It accelerates mobilization of lipids from cells and speeds up lipid catabolism
- The shift from glucose metabolism to lipid metabolism causes a large amount of glucose to remain in the blood = hyperglycemia
What has the opposite effect of growth hormone?
Insulin
What are the three consequences of growth hormone in metabolism?
- Promotes protein anabolism
- Promotes lipid mobilization and catabolism
- Shifts energy use from glucose metabolism to lipid metabolism (increases blood glucose)
What are the only two hormones released from the anterior pituitary that have a releasing factor and an inhibiting factor from the hypothalamus?
- Growth hormone
- Prolactin
What is the function of prolactin during pregnancy and after the baby is born? What is it produced by?
- Lactotrophs
- Pregnancy: promotes development of the breasts, anticipating milk secretion
- Birth: stimulates the mother’s mammary gland to produce milk
What are tropic hormones?
- Hormones that have a stimulating effect on other endocrine glands
- Tend to stimulate the synthesis and secretion of the target hormone
Where are tropic hormones secreted by in the anterior pituitary?
Basophils of the pars anterior
What are the four principal tropic hormones secreted by the anterior pituitary?
- TSH
- ACTH
- FSH
- LH
What is the function of TSH?
- Promotes and maintains development of the thyroid
- Causes thyroid to secrete T3 and T4 to regulate metabolism
What is the function of ACTH?
Promotes and maintains normal growth and development of the cortex of the adrenal gland
ACTH stimulates the release of which hormones? From where?
- Cortisol
- Aldosterone
- From the adrenal cortex
What is the effect of cortisol?
- Released during long-term stress
- Decreases inflammation
- Has a glucose-sparing effect (frees up glucose) to have energy to beat the stressor
Which hormone has a glucose-sparing effect?
Cortisol
What is the effect of FSH in females?
- Acts on the ovary where it stimulates follicles to grow toward maturity
- Stimulates follicle cells to secrete estrogens
- Stimulates growth and development of the follicle that’s supporting the oocyte
What is the effect of FSH in males? What cells do they act on?
- Stimulates development of seminiferous tubules of testes
- Maintains spermatogenesis
- Acts on Sertoli cells
What is the function of LH in females?
- Stimulates formation and activity of corpus luteum of the ovary
- Supports FSH in stimulating maturation of the follicles
What does the corpus luteum secrete when stimulated by LH?
- Progesterone
- Estrogen
What is the function of LH in males?
Stimulates interstitial cells (Leydig cells) in testests to develop and secrete testosterone
What are gonadotrophins? Give two examples.
- Hormones that stimulate growth and maintenance of gonads
- LH and FSH
How do the releasing and inhibiting hormones from the hypothalamus influence the secretion of hormones in the anterior pituitary?
By acidophils and basophils
What happens to FSH levels at menopause?
They rise
Describe the estrogen-progesterone feedback loop.
- Estrogen peak occurs during ovulation, causes LH surge
- LH is responsible for producing the corpus luteum after ovulation
- When the CL forms, you have an increase in progesterone
Target hormones inhibit hypothalamic and anterior pituitary hormone secretion via ___________.
negative feedback
What happens to the hypothalamus and the pituitary when there is a rise in cortisol from the adrenal cortex?
- Hypothalamus: reduce CRH secretion
- Anterior pituitary: reduce sensitivity of the ACTH secreting cells to CRH
What is a portal system?
Arrangement of blood vessels in which blood exiting one tissue is immediately carried to a second tissue before returning to the heart
What are the five releasing hormones released by the hypothalamus into the anterior pituitary?
- Growth hormone releasing hormone (GHRH)
- Corticotropin releasing hormone (CRH)
- Thyrotopin-releasing hormone (TRH)
- Gonadotropin-releasing hormone (GnRH)
- Prolactin releasing hormone (PRH)
What are the two inhibiting hormones released by the hypothalamus into the anterior pituitary?
- Growth hormone inhibiting hormone (GHIH)
- Prolactin inhibiting hormone (PIH)
What is the relationship between the hypothalamus and the posterior pituitary?
Neurosecretory cells have their bodies directly in the hypothalamus and their axon terminals in the posterior pituitary
Describe hormone release from the posterior pituitary.
- Hormone is made an packaged in a cell body of a neuron
- Vesicles are transported down the cell
- Vesicles containing hormone are stored in the posterior pituitary
- Hormones are released into blood
What are the three methods by which hormone pathologies can occur?
- Hormone excess
- Hormone deficiency
- Abnormal responsiveness of target tissues
What is Cushing’s disease?
Hypercortisol secretion
What are the causes of hormone excess?
- Benign tumours
- Cancerous tumours
What are the potential causes of Cushing’s disease?
- Tumour of adrenal gland secreting cortisol
- Tumour elsewhere secreting ACTH, which in turn stimulates excessive secretion of cortisol
What are the symptoms of Cushing’s disease?
- Breakdown of muscle proteins and redistribution of body fat
- Spindly arms and legs accompanied by a rounded “moon face”
- Pendulous abdomen
- Flushed appearance
What are the causes of hypothyroid secretion?
- Iodine deficiency
- Stress
- Congenital (rare)
What are the symptoms of hypothyroidism?
- Swelling of facial tissues (puffiness)
- Slow heart rate
- Low body temperature
- Sensitivity to cold
- Dry hair and skin
What are the five normal cortisol actions?
- Protein breakdown
- Glucose formation
- Lipolysis
- Anti-inflammatory effects
- Depression of immune responses
What are the five normal thyroid hormone actions?
- Increase metabolic rate
- Caloregenic effect
- Stimulate protein synthesis (increase use of glucose and FA for ATP production)
- Enhance actions of catecholamines
- Accelerates body growth
How do thyroid hormones increase basal metabolic rate?
Stimulates the use of oxygen to produce ATP
How do thyroid hormones produce a calorigenic effect?
Stimulates synthesis of additional sodium-potassium ATPases
What are the six normal functions of insulin?
- Accelerate facilitated diffusion of glucose into cells
- Speed conversion of glucose into glycogen
- Increase uptake of amino acids and protein synthesis
- Speed synthesis of fatty acids
- Slows glycogenolysis
- Slows gluconeogenesis
What is the cause of type II diabetes?
Obesity
What are symptoms of type II diabetes?
- High blood glucose
- Weight loss
- Excessive thirst
- Frequent urination
Why does ketosis occur in type II diabetics?
- Glucose is not taken up by cells
- Since they can’t utilize glucose, they must use fat to provide energy
- Ketosis is a by-product of fatty acid breakdown
Match the communication with its property.
A) cytokine B) gap junction C) hormone D) neurohormone E) neurotransmitter F) paracrine signal G) autocrine signal
- Electrical
- Chemical
- Electrical and chemical
- a, c, d, e, f, g
3. b
What communication methods are transported in the circulatory system?
Cytokines, neurohormones, hormones
What communication methods are released by neurons?
Cytokines, neurohormones, neurotransmitters
A cat sees a mouse and pounces on it. Give two reasons why this internal signal to pounce cannot have been transmitted by a paracrine signal.
- Because the eyes are too far apart from the legs
- Because the response was too rapid for it to have occurred by diffusion
List four components of signal pathways.
- Signal
- Receptor
- Intracellular signal
- Target proteins
Name three cellular locations of receptors.
- On the cell membrane
- In the cytosol
- In the nucleus
Place the following terms in the correct order for a signal transduction pathway:
Cell response, receptor, second messenger, ligand
Ligand; receptor; second messenger; cell response
Place the following terms in the correct order for a signal transduction pathway:
Amplifier enzyme, cell response, phosphorylated protein, protein kinase, second messenger
Amplifier enzyme; second messenger; protein kinase; phosphorylated protein; cell response
Will the cell depolarize or hyperpolarize if Cl- channels open?
Hyperpolarize
Will the cell depolarize or hyperpolarize if K+ channels open?
Hyperpolarize
Will the cell depolarize or hyperpolarize if Na+ channels open?
Depolarize
To decrease a receptor’s binding affinity, a cell might (select all that apply):
A) synthesize a new isoform of the receptor
B) Withdraw receptors from the membrane
C) Insert new receptors into the membrane
D) Use a covalent modulator
A) and D)
The three main amplifier enzymes are a) ______, which forms cAMP; b) ________, which forms cGMP; and c) ________, which converts a phospholipid from the cell’s membrane into two different second messenger molecules.
a) Adenylyl cyclase
b) Guanylyl cyclase
c) Phospholipase C
Would the following reflexes have positive or negative feedback?
A) glucagon secretion in response to declining blood glucose
B) increasing milk release and secretion in response to baby’s suckling
C) Urgency in emptying one’s urinary bladder
D) Sweating in response to rising body temperature
A) Negative
B) Positive
C) Negative
D) Negative
What distinguishes a neurotransmitter from a neurohormone?
- Neurotransmitters act on nearby cells (paracrine action)
- Neurohormones act on distant targets
What is the classic definition of a hormone?
A chemical secreted into the blood that acts on a distant target in very low concentrations
Catecholamines belong to which class of hormone?
Amino-acid derivatives
Metabolites are inactivated hormone molecules, broken down by enzymes primarily found in the ______ and _______, to be excreted in the _______ and _______, respectively.
liver, kidneys
bile, urine
Melatonin is made from the amino acid ________, and the catecholamines and thyroid hormones are made form the amino acid _________.
tryptophan
tyrosine
A hormone that controls the secretion of another hormone is known as a ________ hormone.
trophic
What characteristic defines neurohormones?
Synthesized and secreted by neurons
What class do oxytocin and vasopressin belong to?
Peptide neurohormones
Differentiate primary and secondary endocrine pathologies.
- Primary: arises in the last endocrine gland of the pathway
- Secondary: arises in a gland secreting a trophic hormone
Up-regulation allows a target cell to __________.
A) develop tolerance of a particular drug
B) increase the sensitivity of a target cell to a ligand
C) decrease its number of receptors for a ligand
D) decrease its binding for a ligand
B) increase the sensitivity of a target cell to a ligand
Name the hormone that promotes storage of organic fuels (glucose, amino acids, and fats) and reduces blood glucose levels.
Insulin
Hormones known as catecholamines are __________.
amines
Which of the following is NOT a peptide hormone?
A) prolactin
B) epinephrine
C) oxytocin
D) atrial natriuretic peptide
B) epinephrine
What is a merocrine gland?
Vesicle releases its contents (intact cell)
What is a holocrine gland?
Cell with a secretory product dislodges
What is an apocrine gland?
Pinched off portion of cells release secretory product
Which of the following statements about amine hormones is true?
A) Amine hormones are released from the parent cells by simple diffusion.
B) Amine hormones are synthesized on demand.
C) Amine hormones can be transported by being dissolved in plasma or bound to carrier proteins.
D) Insulin and parathyroid hormone are examples of amine hormones.
C) Amine hormones can be transported by being dissolved in plasma or bound to carrier proteins.
