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Endocrine System 1. Hormones – Func8on – Classifica8on – General process
2. Secretory control: The Pituitary gland and the hypothalamus – Hormonal media8on
through an axis system 3. Hormonal Regula8on – Stress Response – Metabolism
• Endocrine glands – Single gland made up of many secretory cells
– Secrete many different hormones
– Each hormone binds to different receptors on different target cells
Endocrine glands
Secretory Cells
Hormones Hormones
Hormones
Target Cell
Target Cell Target Cell
Endocrine System
Hormones: Func8on • Chemical produced and released by endocrine cells
• Regulates func8on of other cells • There are a few of them...
• Hormones carried in bloodstream – Can exert effects over long-‐distances
• Bind to receptor proteins on specific target cells – Pass by many cells through circula8on
• Hormones control many bodily func8ons: – Water balance – Environmental/physical stress
– Metabolism – Reproduc8on, growth, development
Hormones
Hormones: Func8on
• Greater rate of secre8on = greater effect on target cells – Because hormones are more concentrated in blood
• Target cells have 1000s receptor proteins – Greater ability to receive more hormones = higher sensi,vity
Endocrine glands
Secretory Cells
Hormones Hormones
Hormones
Target Cell
Target Cell Target Cell
Hormones: Classifica8on 1. Steroid hormones – Lipid-‐soluble (diffuse through cell membranes) – Binds to receptor proteins located INSIDE cell – Ac8on is slow because steroid hormones produce proteins
Figure 2.25d
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Hormones: Classifica8on 2. Pep8de hormones – Chains of amino acids – Binds to receptors on cell membrane -‐ enzyme-‐linked or G-‐
protein coupled reac8ons – Binding ac8vates 2nd messenger (cAMP) to ac8vate other
enzymes
Figure 2.25c
Hormones: Classifica8on 3. Amine hormones – Modified chains of amino acids
New proteins 1. Hormone binds to
receptor proteins on target cell – G-‐protein coupled,
Intracellular, Enzyme-‐ac8vated
2. Interacts with DNA in target cell – Alters gene expression (may
trigger protein synthesis)
3. New proteins carry out func8on
Hormones
Target Cell
Target Cell Target Cell
Endocrine System: General process
New func8ons
Endocrine System 1. Hormones – Func8on – Classifica8on – General process
2. Secretory control: The Pituitary gland and the hypothalamus – Hormonal media8on
through an axis system 3. Hormonal Regula8on – Stress Response – Metabolism
Hypothalamus • Maintains homeostasis by regula8ng internal environment – Regulates hormones released from pituitary gland
– Produces some hormones secreted by the pituitary gland
– Controls body temperature
– Maintains water balance
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Pituitary Gland 2. Anterior pituitary – Hormones synthesized
and secreted in endocrine cells in 8ssues
1. Posterior pituitary • Hormones secreted
here are synthesized in hypothalamus
Posterior Pituitary Gland 1. Median eminence 2. Infundibular stalk – Contain axons of neurons from hypothalamus
3. Pars nervosa – Neurons synapse
with arteries – Release hormones
from hypothalamus to bloodstream • Vasopressin
(an8diure8c hormone)
• Oxytocin
Anterior Pituitary Gland
2. Travel through series of vessels to anterior pituitary
3. S8mulate/inhibit release of hormones from endocrine cells in anterior pituitary
• Made up of endocrine cells • Hypothalamo-‐hypophysical portal system: 1. Hypothalamus secretes neurohormones into
median eminence
Anterior Pituitary Gland • Hypothalamus secretes two kinds of
neurohormones • Releasing hormones s8mulate anterior pituitary to
release specific hormone
Anterior Pituitary Gland • Hypothalamus secretes two kinds of
neurohormones • Releasing hormones s8mulate anterior pituitary to
release specific hormone • Release-‐inhibi8ng hormones inhibit anterior pituitary from secre8ng hormones
CNS ‘controls’ endocrine system Internal/External
signals and/or s8muli Sensory receptors
Secrete neurohormones
Signals integrated in CNS Motor neurons
synapse with neurosecretory cells
Affect endocrine glands and 8ssues
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Endocrine System 1. Hormones – Func8on – Classifica8on – General process
2. Secretory control: The Pituitary gland and the hypothalamus – Hormonal media,on
through an axis system 3. Hormonal Regula8on – Stress Response – Metabolism
Hormone media8on • Axis system: when secre8ons of one endocrine gland act on (mediate) the secre8ons from another
• Hypothalamus-‐anterior pituitary-‐thyroid axis mediates hormones released from the thyroid
Hormone media8on
• Hypothalamus-‐Pituitary-‐Adrenal Cortex (HPA) axis mediates hormones released from the adrenal cortex STRESS RESPONSE
• Axis system: when secre8ons of one endocrine gland act on (mediate) the secre8ons from another
Adrenal Cortex
• Glucocor,coids secreted in response to stress – Promote increased blood glucose concentra8on
– Cor8sol is main human glucocor8coid
• Adrenal gland secretes many hormones for several systems
HPA axis • Nervous and endocrine systems TOGETHER mediate HPA axis
Hormone media8on in the HPA axis
1. Synergys,c: one hormone amplifies effect of another • Vasopressin + CRH
à increased produc8on of CRH
• Vasopressin alone à minimal effect
• How do nervous and endocrine systems interact to affect hormone produc8on/secre8on?
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Hormone media8on in the HPA axis
1. Synergys8c 2. Permissiveness:
Presence of one hormone required for other to operate • Adrenaline causes
vasoconstric8on ONLY if cor8sol is present
• How do nervous and endocrine systems interact to affect hormone produc8on/secre8on?
Hormone media8on in the HPA axis
• How do nervous and endocrine systems interact to affect hormone produc8on/secre8on?
1. Synergys8c 2. Permissiveness 3. Antagonism: one
hormone opposes ac8on of another • Insulin promotes uptake
of glucose from blood; glucagon s8mulates release of glucose into blood
Endocrine System 1. Hormones – Func8on – Classifica8on – General process
2. Secretory control: The Pituitary gland and the hypothalamus – Hormonal media8on
through an axis system 3. Hormonal Regula,on – Stress Response – Metabolism
Stress response • Adrenal cortex secretes glucocor8coids
• Alters many physical processes – Reduced feeding, reproduc8on
– Increased heart and breathing rate
– Heightened alertness – Release of stored energy – O2/nutrients sent to CNS
Stress response • Involves autonomic NS and HPA axis
Stress response 1. Stress event à Autonomic NS and HPA axis response – NS: Adrenal Medulla à Epinepherine, norepinepherine – HPA axis: hypothalamus à Cor8cotropin-‐releasing hormone
(CRH); pituitaryà adrenocor8cotropin-‐releasing hormone (ACTH)
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Stress response 1. Stress event à Autonomic NS and HPA axis response
Phase 1 (fast) responses:
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à More blood to vital organs to fuel “fight or flight” response à To fuel muscle and heart rate increases (simple sugars easiest to convert) à To counteract increased circula8ng blood glucose
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Stress response 2. Signals integrated between CNS and HPA axis
-‐ epinephrine further s8mulates CRH produc8on -‐ CRH and epinephrine increase alertness
Stress response 3. Adrenal cortex releases glucocor8coids
Stress response 3. Adrenal cortex releases glucocor8coids Phase 2 (slow) responses:
à More circula8ng glucose (brain func8on) à More faiy acids (func8on of other 8ssues) à More amino acids (8ssue repair)
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3
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Stress response 4. Chronic stress has long-‐las8ng effects
Chronic responses:
à Inhibited gonadotropin, GH (suppressed reproduc8on) à High blood pressure (hypertension) à Bone-‐thinning à Suppressed immune system à Atrophy/shrinkage of hippocampus (memory, emo8ons)
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Endocrine System 1. Hormones – Func8on – Classifica8on – General process
2. Secretory control: The Pituitary gland – Hormonal media8on
through an axis system 3. Hormonal Regula,on – Stress Response – Metabolism
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Hormonal regula8on of metabolism • Cells need nutrients con8nuously – Fats, carbohydrates, proteins
• Rely on stored energy sources • Hormones regulate storage, mobiliza8on, conversion into useable forms – Sense body’s needs/requirements
Hormonal regula8on: Metabolic func8ons
• Concentra8on of blood glucose is main factor in metabolic func8oning
• Two main hormones secreted by pancreas 1. Insulin: decreases
blood glucose concentra8on
2. Glucagon: increases blood glucose concentra8on
Hormonal regula8on: Insulin • Short-‐term storage/release of nutrients
• Insulin binds to protein receptors à facilitates diffusion of glucose into target cells
Eat Food
Pancreas releases insulin
é storage of all three nutrients
é uptake of glucose, faiy acids, amino acids from blood
ê Blood glucose concentra8on
Decrease in blood glucose: hypoglycemic effect
Carbohydrates cause spike in blood glucose
1. High carb meal 2. Glucose in blood
surges 3. Insulin released 4. Facilitated diffusion
into cells 5. Lowers blood
glucose
Proteins DO NOT cause spike in blood glucose
1. Low carb meal 2. NO Surge of
glucose in blood 3. Insulin s8ll released 4. Facilitated diffusion
into cells 5. Lowers blood
glucose
Diabe8cs don’t produce insulin • Blood glucose remains high • Kidneys can’t filter glucose – Excreted as waste and not used for energy! – Diabe8cs are told to avoid carbohydrates (simple sugars)
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Hormonal regula8on: Glucagon
• Pep8de hormone secreted by pancreas • Released when blood glucose low, amino acids high
Hormonal regula8on: Glucagon • S8mulates gluconeogenesis
• Causes blood glucose to rise: Hyperglycemic effect