Download Hormonal control and responses

Hormonal control and responses
Types of Hormones
• Amino acid derivatives
– epinephrine, serotonin, melotonin
• Protein
– insulin, parathyroid hormone, growth hormone
• Steroids
– derived from cholesterol
– sex hormones, mineralocorticoids,
prostaglandins
Hormone-receptor interaction
• Some hormones circulate to all tissues, but
only act on some
• receptor must be present for effect to occur
– eg thyroid stimulating hormone only exerts an
effect on the thyroid
– conversely some hormones work on virtually
all tissues (insulin)
Blood Hormone Concentration
• the effect of a hormone related to
concentration in blood (to a point)
• Concentration affected by 4 factors
–
–
–
–
rate of hormone secretion
rate of metabolism or excretion
transport proteins
plasma volume (affected by exercise)
Control of Hormone Secretion
• Rate of insulin secretion from the pancreas
is dependent on:
– Magnitude of input
– Stimulatory vs. inhibitory
Factors That Influence the Secretion
of Hormones
Mechanisms of Hormone Action
• alteration of membrane transport (insulin)
• stimulation of DNA synthesis (testosterone,
estrogen)
• activation of “second messengers”
– hormone doesn’t enter the cell
Relationship of Hypothalamus,
Pituitary and Target Glands
The Hypothalamus is the “Master
Gland”
• the hypothalamus controls the pituitary in
two ways
– the hypothalamus can release “releasing
hormones”
• releasing hormones act on anterior pituitary (TSH,
ACTH, GH)
– neurons originating in the hypothalamus act on
posterior pituitary (ADH)
Positive and Negative Input to the
Hypothalamus (Growth Hormone)
Growth Hormone
• uptake of amino acids and protein synthesis
• opposes insulin
– reduces use of plasma glucose
– increases gluconeogenesis
– mobilizes FFA
Antidiuretic Hormone (ADH)
• causes resorbtion of H2O to maintain fluid
• stimulated by two factors
– high plasma osmolality (sweating)
– low plasma volume (loss of blood, exercise)
Intensity vs. Plasma ADH
The Adrenal Glands
• Medulla
– secretes epinephrine (E) and norepinephrine
(NE)
• Cortex
– secretes mineralocorticoids, glucocorticoids
Response to Catecholamines:
Role of Receptor Type
Receptor
Type
Effect of
E/NE
Membrane-bound
enzyme
Intracellular
mediator
Effects on Various Tissues
1
E=NE
Adenylate cyclase
 cAMP
 Heart rate
 Glycogenolysis
 Lipolysis
2
E>>>NE
Adenylate cyclase
 cAMP
 Bronchodilation
 Vasodilation
1
ENE
Phospholipase C
 Ca++
 Phosphodiesterase
 Vasoconstriction
2
ENE
Adenylate cyclase
cAMP
Opposes action of 1 & 2
receptors
Aldosterone (Mineralocorticoid)
• regulates K+ and Na+ concentrations
• controls resorbtion in the kidney
• involved in thirst response
Intensity vs. Mineralocorticoid
Response
Cortisol
• Actions
– promotes breakdown of tissue protein (inhibits
protein synthesis)
– mobilizes FFA from adipose
– stimulates gluconeogenesis
– blocks entry of glucose into tissues (increases
fat utilization)
• Involved in adaptation response to stress
(exercise)
Control of Cortisol Secretion
Pancreas
• Insulin
– aids in transport of glucose into cells
– stimulated when blood sugar increases (storage
of glucose, amino acids and fat)
– inhibited during exercise
• Glucagon
– opposite effect of insulin
– stimulated by low blood glucose
– mobilizes glucose and fatty acids
Sex Hormones
• testosterone
– elevated during short-term high intensity
exercise
– levels typically lower in endurance trained
individuals
Estrogen
• promotes higher levels of fat
metabolism ?
• chronic endurance training may
suppress E2 (amenorrhea)
Muscle Glycogen Utilization
• glycogen metabolism controlled by
epinephrine (cAMP) and intracellular Ca++
(calmodulin) from sarcoplasmic reticulum
– epinephrine increases rapidly with intense
exercise
– adrenergic blockade
– glycogen depleted only in exercising muscles
• Ca++ faster than cAMP and more specific
Blood Glucose Homeostasis During
Exercise
• mobilization of glucose from liver glycogen
stores
• mobilization of plasma FFA from adipose
tissue to spare plasma glucose
• synthesis of new glucose in the liver
(gluconeogenesis) from AA, La, and
glycerol
• blocking of glucose entry into cells to force
the substitution of FFA as a fuel
Slow Acting Hormones
• Thyroxine
– allows other hormones (eg epinephrine) to exert
effect
• Cortisol
• GH
Cortisol and Maintenance of
Plasma Glucose
At low intensity, cortisol decreases- at
high intensity it increases
Growth Hormone Effects During
Exercise
Growth Hormone During Exercise
• Combine amino acids and glycerol to make
glucose in the liver
• Breaks down triglycerides (fat) in the
adipose tissue to make FFA available
• Blocks entry of glucose into the cell
• All of these go to maintain blood glucose
Plasma GH Response vs. Intensity
GH Response in Runners vs. Controls
(Runners have improved response)
Fast Acting Hormones
• catecholamines (epinephrine and
norepinephrine)
– N primarily neurotransmitter at synapse
– E primarily plasma hormone
• insulin
• glucagon
Effects of Catecholamines during
Exercise
Catecholamines (adrenergic)
During Exercise
• Break down glycogen in liver to free
glucose available
• Break down triglycerides in the adipose
tissue to make FFA available
• Block entry of glucose into the cell
Catecholamine Response during
Prolonged Exercise
Insulin (storage) vs. Glucagon (mobilization)
Insulin Levels Reduced during
Moderate to Intense Exercise
Endurance Training Attenuates Insulin
Response at Given Workload
Reduced Glucagon Response after
Endurance Training
Take home…
• Almost all of the hormonal responses will be
attenuated with endurance training
– Exception-growth hormone
Glucagon Response Reduced after
Endurance Training Because…
• increased utilization of FFA as fuel substrate
• decreased reliance on plasma glucose
• therefore decreased reliance on liver
glycogen
Remember
• -adrenergic… inhibition
• -adrenergic… excitation
Adrenergic Control of Pancreatic
Hormones
Effect of Increased Sympathetic
Activity on Fuel Utilization
Glucose Uptake by Cells can
Increase 7-25 Fold During
Exercise. How?
• increased blood flow to exercising tissues
• increased metabolism causes gradient
(diabetics)
• increased # s of glucose transporter at
membrane (diabetics)
General Hormonal Responses to
Graded or Prolonged Exercise
Lactic Acid Inhibits FFA Release
from Adipose Tissue (Means?)