Hormonal Responses (CHPT 5) Flashcards
What is the role of the endocrine glands?
Release hormones directly into the blood
There are several classes based on chemical make up. What are these classes?
Amino acid derivatives, peptide/protein, steroids.
The effect of a hormone on a tissue is determined by what?
the plasma concentration and number of active receptors
What is plasma concentration determined by?
- Rate of secretion of hormones from endocrine gland
- rate of metabolism, or excretion of hormone
- quantity of transport proteins
-Changes in plasma volume
What are some factors that influence of secretion of hormones?
- increased plasma glucose
- increased plasma amino acids
- Sympathetic activity
- Increased parasympathetic activity 
What is the magnitude of effect of a hormone dependent on?
- Concentration of the hormone
- Number of receptors on the cell
- Affinity of the receptor for the hormone
What is downregulation?
- decrease in receptor number in the response to a high concentration of hormone
What is upregulation?
Increase in receptor number in response to low concentration of hormone
What are the mechanisms of hormone action? (modify, cellular activity)
- Activation of genes to alter protein synthesis
- activating second messengers in the cell via G protein
- Altering membrane transport
What kind of hormone activates gene to alter protein synthesis?
Steroid hormones
What activates second messengers in the cell via G proteins?
-cyclic AMP
-Ca++
-Inositol triphosphate
-diaclyglycerol
What is an example of altering membrane transport?
Insulin via tyrosine kinase.
Explain the mechanism of steroid hormone action.
- Hormone passes through plasma membrane.
- Hormone by zero receptor protein in the cytoplasm or nucleus
- Hormone receptor complex binds to hormone response element on DNA, regulating gene transcription
- Protein synthesis
- Change in protein synthesis is cellular response.
Describe the Cyclic AMP second messenger.
- I’m on Bryne’s to a G protein coupled receptor on the plasma membrane.
- The G protein activates adenylate cyclase which causes ATB to be converted to cyclic AMP
- The cyclic, AMP, activates protein, thinners a
- Which activates response, protein to alter cellular activity
Explain the phospholipase C messenger mechanism.
- hormone binds to GPCR on the plasma membrane and activates G protein
- G-protein activate the effector protein phospholipase C
- Causes phosphotidylinositol (PIP2) to be broken down into inositol triphosphate (IP3) and disygkycerol (DAG)
- IP3 causes release of calcium from the intra cellular organelles that activates a calcium binding protein calmodulin
- DAG activates protein kinase C to bring about additional cellular response
Explain insulin receptors.
- Insulin binds to the tyrosine kinase receptors, alpha subunits (outside the cell)
- Binding causes the beta subunits located inside the cell to phosphorylate themselves and activate signalling proteins
- the incident. Response proteins activate glycogen synthase to synthesise glycogen from glucose
What are the major endocrine glands?
Hypothalamus and pituitary glands, thyroid and parathyroid glands, adrenal glands, pancreas, testes and ovaries
What is the role of the hypothalamus?
Control secretions from the pituitary gland
What hormones are secreted by the anterior pituitary gland? (7)
Luteinizing hormone (LH).
Melanocyte-stimulating hormone (MSH).
Thyroid-stimulating hormone (TSH).
Growth hormone (GH).
Prolactin.
Adrenocorticotropic hormone (A C T H).
Follicle-stimulating hormone (FSH).
Which hormones are secreted by the posterior pituitary gland?
- oxytocin
- antidiuretic hormone (ADH)
What is the role of Adrenocorticotropic hormone (ACTH)?
- Stimulates cortisol release from adrenal glands
What is the role of Luteinizing hormone (LH)?
- Stimulates production of testosterone and estrogen
What does the growth hormone stimulate?
- Liver and other tissues
- Protein synthesis and growth
- Increases glyconeogenesis in liver
- Blocks, glucose entry to adipose cell to favour, fat metabolisation.
Which hormones from the anterior pituitary gland stimulate cell signaling mechanisms?
Melanocyte-stimulating hormone (MSH).
Thyroid-stimulating hormone (TSH).
Prolactin.
Growth hormone (GH).
What is the role of the thyroid stimulating hormone? (TSH)
- Controls thyroid hormone released from thyroid gland
Explain the role of (insulin like growth factors) IGFs
Responsible for muscle growth
(IGF-1)
Which hormone is responsible for amino acid uptake, protein synthesis, and long bone growth?
Growth hormone
How does a growth hormone spare plasma?
- Opposes insulin action, reduces the use of plasma
- Increases glucogenesis
- Metabolises fatty acids from adipose tissue
What can the growth hormone be used to treat?
- Childhood dwarfism
- Also used by athletes and elderly
What is the role of the antidiuretic hormone?
- Reduces water loss from the body to maintain plasma volume
What stimulates the release of the antidiuretic hormone?
- High plasma osmolality and low plasma volume
- Caused by sweat loss without water replacement
Does the antidiuretic hormone increase during exercise?
- Yes, above 60% of VO2 Max to maintain plasma volume
What are the roles of Triiodothyronine (T3) and thyroxine (T4)?
- Influences resting metabolic rate.
- Permissive hormones (permit full effect of other hormones)
Which gland secrete calcitonin?
The thyroid gland
What is the role of calcitonin?
- Involved in the regulation of plasma Ca++.
- Blocks Ca++ release from bone, stimulates excretion by kidneys
What is the role of the parathyroid hormone?
- Primary hormone in plasma Ca++ regulation.
- Stimulates Ca++ release from bone.
- Stimulates reabsorption of Ca++ by kidneys.
- Converts vitamin D3 into a hormone that increases Ca++ absorption from the GI tract.
What is the role of the adrenal medulla?
- Secretes the catecholamines (Epinephrine (E) and norepinephrine (N E))
- Bind to adrenergic receptors ( (α) and (β) )
What do Epinephrine (E) and norepinephrine (N E) do?
- Fast-acting hormones.
- Part of the “fight or flight” response.
What is the role of the adrenal cortex?
- secretes steroid hormones (derived from cholesterol)
- Mineralcoticoids
- sex steroids
- glucocorticoids
What is the role of mineralocorticoids?
- releases aldosterone
- Maintenance of plasma, sodium and potassium
What are examples of glucocorticoids? What is the role?
- cortisol
- Regulation of plasma glucose 
What are examples of sex steroids and their role?
- androgens and estrogens
- Support prepubescent growth
What is the role of aldosterone?
- Control of sodium reabsorption and potassium secretion
- Regulation of blood volume and blood pressure
What is aldosterone stimulated by?
- Increase in potassium concentration and decrease in plasma volume
What is the role of cortisol?
Maintenance of plasma glucose.
What is the importance of cortisols maintenance of plasma glucose?
- promotes protein breakdown for glycogenesis
- stimulates FFA mobilisation
- stimulates glucose synthesis
- Blocks uptake of glucose into cell (promotes fatty acids as fuel)
What stimulates cortisol secretion?
- Stress via ACTH
- Exercise
What hormones do you do adipose tissue secrete?
Leptin and adiponectin
What is the role of Leptin?
- Influences appetite through the hypothalamus
- Enhances insulin sensitivity and fatty acid oxidation
What is the role of adiponectin?
- Increases insulin sensitivity and fatty acid oxidation
What is the balance between leptin and adiponectin in regards to obesity?
Higher levels of leptin and lower levels of adiponectin
- Leads to type two diabetes and low-grade inflammation
Does the pancreas have exocrine or endocrine functions?
Both
Which hormone does the pancreas secrete?
- Insulin (beta)
- Glucagon (alpha)
- Somatostatin (delta)
- Digestive enzymes and bicarbonate (into small intestine)
What is the role of insulin?
- Promotes the storage of glucose amino acids, and fats
What is the role of glucagon?
Promotes the mobilization of fatty acids in glucose
Where is testosterone released from?
The testes
What is the role of testosterone as an anabolic steroid?
- Promotes tissue (muscle) building
- Performance enhancement
What is the role of testosterone as an androgenic steroid?
- Promotes masculine characteristics
Where are estrogen and progesterone released from?
The ovaries
What is the role of estrogen and progesterone?
- Establish and maintain reproductive function
What is the role of estrogen?
- development of ovum
- Deposition of fat to thighs and buttocks
- Breast development
Skeletal muscles produce what during contractions?
- Myokines
What do myokines do during muscle contractions?
- stimulates glucose uptake and fatty acid
- Promote blood vessel growth in muscle
- Promotes liver glucose production and triglyceride breakdown
What is the role of Interleukin 6 (I L-6) in the muscle?
Both proinflammatory and anti-inflammatory.
IL-6 produced during exercise promotes what?
- promotes anti-inflammatory effects.
Glycogenolysis (effective glycogen utilization) is related to what?
- High-intensity exercise results in greater and more rapid glycogen depletion.
Plasma ??? is a powerful simulator of glycogenolysis.
- epinephrine
What causes more significant increases in plasma epinephrine?
- high-intensity exercise
Which hormones cause muscle breakdown?
- Epinephrine-cyclic A M P (via beta-adrenergic receptors)
- Ca++−calmodulin (enhanced during exercise due release from the sarcoplasmic reticulum)
What is propranolol?
- beta-receptor blocker
- no effect on muscle glycogen utilization
Plasma glucose is maintained through how many processes?
- 4
What are the four processes that maintain plasma glucose during exercise?
- Mobilization of glucose from liver glycogen stores.
- Mobilization of F F A from adipose tissue (spares blood glucose)
- Gluconeogenesis from amino acids, lactic acid, and glycerol.
- Blocking the entry of glucose into cells (forces use of FFA as a fuel)
Which permissive or slow-acting hormones maintain blood glucose homeostasis during exercise?
- Thyroxine, cortisol, and growth hormone
Which fast-acting hormones maintain blood glucose homeostasis during exercise?
Epinephrine, norepinephrine, insulin, and glucagon
Is there a change in T3 or T4 during exercise?
- no
What are the roles of thyroid hormones during exercise?
- act in a permissive manner to allow other hormones to exert their full effect
What is the role of T3?
- T3 enhances effect of epinephrine to mobilize free fatty acids from adipose tissue
Is cortisol a slow or fast acting hormone?
- slow-acting
When do concentrations of cortisol peak?
peak in the AM & drop throughout the day
What are the effects of cortisol?
- Stimulate F F A mobilization from adipose tissue.
- Enhance gluconeogenesis in the liver.
- Decrease the rate of glucose utilization by cells.
What are the effects of exercise on cortisol levels?
- Increases proportional to increases in exercise intensity.
- Accurate responses to exercise should be normalized to time of day changes in the hormone.
Changes in cortisol may be related to repair of….
- exercise-induced tissue damage.
Is the growth hormone a fast or slow acting hormone?
- slow-acting
What are the roles of the growth hormone?
- supports the action of cortisol
How does the growth hormone support the action of cortisol?
- Decreases glucose uptake by tissues.
- Increases free fatty acid mobilization.
- Enhances gluconeogenesis in the liver.
What are the effects of exercise on the growth hormone?
- Increase in plasma GH with increased intensity.
- Greater response in trained runners.
Are epinephrine and norepinephrine fast-acting or slow-acting hormones?
- fast-acting hormones
What is the role of epinephrine and norepinephrine during exercise?
- maintain blood glucose
How does epinephrine and norepinephrine maintain blood glucose levels during exercise?
- Muscle glycogen mobilization.
- Increasing liver glucose mobilization.
- Increasing FFA mobilization.
- Interfere with glucose uptake.
Does plasma E and NE increase or decrease during exercise?
- Related to increased heart rate and blood pressure during exercise.
Does submaximal intensity exercise increase or decrease E and NE?
- decrease plasma E and NE following training
Does supramaximal intensity exercise increase or decrease E and NE?
- increased plasma E and NE in trained individuals
Are insulin and glucagon slow or fast acting hormones?
- fast-acting hormones
What is insulins role?
- Uptake and storage of glucose and F F A.
Does plasma concentration of insulin increase or decrease during exercise?
- decreases
What happens to insulin levels following training?
- decrease
What is the role of glucagon?
- Mobilization of glucose and F F A fuels.
Does plasma concentration of glucagon increase or decrease during exercise?
- increases
What happens to glucagon levels following training?
- decrease
Insuline and glucagon secretion are influences by what?
- catecholamines (dopamine, epinephrine, norepinephrine)
FFA mobilization is dependent on what?
- hormone sensitive lipase (HSL).
Does FFA mobilization increase or decrease during heavy exercise?
- decreases
When is the release of FFA from adipose tissue at its highest? and when does it decrease?
- 25% VO2 max (highest)
- begins decreasing at 65% and 85%
Why does FFA mobilization decrease during heavy exercise?
- High levels of lactic acid (promotes resynthesis of triglycerides)
- Elevated H+ concentration inhibits HSL.
- Inadequate blood flow to adipose tissue.
- Insufficient albumin to transport FFA in plasma.
