Download Endocrine System

Endocrine System
• coordinates and integrates activity of body
cells
– Via hormones
– In conjunction with nervous system
• Response: slow onset
• Duration: long lasting
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Endocrine System: Overview
• Neuroendocrine organ
– Example: Hypothalamus
• Endocrine glands
– Examples: pituitary,
thyroid, parathyroid,
adrenal, and pineal
glands
• exocrine and endocrine
glands
– Examples: Pancreas,
gonads, placenta
© 2013 Pearson Education, Inc.
Hormones
• Classes
– Amino acid-based hormones
– Steroids
• Source: Endocrine glands
– Travel in bloodstream
• Target cells: Receptor specificity
– up-regulation: ____ # receptors, in response to
low hormone level
– Down-regulation: _____# receptors, in response
to high hormone level
Control of hormone release
• Types of Stimuli
– Humoral stimuli
• ions and nutrients => hormone secretion
– Neural stimuli
• sympathetic nerve fibers => hormone
secretion
– Hormonal stimuli
• hormones => another hormone secretion
• Schema: hypothalamus => pituitary gland
=> endocrine gland
Control of hormone release
• Blood levels of hormones
– Controlled by negative feedback systems
– schema: Stimulus => hormone secretion
• (-)-feedback: hormone level =>  hormone secretion
Oxytocin
• Source: hypothalamus
• targets
– Breast: milk ejection
• “Let-down reflex”
• during nursing
– Uterus: contraction
• induce parturition
• reduce postpartum
bleeding
6
Anti-diuretic hormone (ADH or
vasopressin)
• Source: hypothalamus
• Target
– Collecting tubules &
ducts
• H2O reabsorption
– Arteriolar constriction
• Regulation of ADH
– Dehydration
– Overhydration
• Diabetes Insipidus (DI)
– Central or Nephrogenic
7
Growth hormone (GH)
• Source
– Hypothalamus: GHRH
– Pituitary gland: GH
• Blood glucose
• Anabolism: Bone & tissue
growth
– “thyroid hormone”
– Liver: Somatomedins
(IGF – insulin-like growth
factor)
• Cartilage-growth
• Major targets
– bone
– skeletal muscle
Growth hormone
• Metabolic actions
– ↑ plasma glucose
• adipose tissue and skeletal muscle: Inhibit glucose
uptake
• adipose tissue: lipolysis
• Liver: gluconeogenesis
– ↑amino acids uptake into muscle
• Release in pulsatile fashion
– ↑Secretion GH: Sleep, Puberty, Exercise
– ↓ Secretion GH: Obesity, hyperglycemia
Clinical Considerations
• Excess
– ↑blood glucose concentration
• Insulin release => pancreatic cell burnout
– Excess growth
• Gigantism
• Acromegaly
• Deficiency
– Dwarfism
Acromegaly vs. Gigantism
Figure 16.7 Disorders of pituitary growth hormone.
© 2013 Pearson Education, Inc.
Prolactin
• Source
– Hypothalamus: Prolactin
releasing hormone (PRH)
– Pituitary gland: prolactin
• Target
– Mammary glands
• development
• milk secretion
Prolactin
• Conditions
– Suckling
• ↑prolactin, ↓dopamine
=> Milk secretion
• ↓GnRH => contraception
– Hypersecretion
• inappropriate lactation
• lack of menses &
infertility in females
• impotence in males
Thyroid Hormone
• Source
– Hypothalamus:
• Thyrotropin releasing
hormone
– Pituitary gland:
• Thyroid stimulating
hormone
– Thyroid gland (follicular
cells)
• Thyroid hormone
– T4 – more abundant,
potent (-)-feedback
– T3 – biologically more
active
Thyroid hormone
• Adults: NOT essential for life, but affect the
quality of life
• Children: ESSENTIAL for the normal growth &
development in children (TESTED in
newborns)
– Thyroid hormone has permissive effects on
•
•
•
•
Growth hormone
epinephrine
Growth
Maturation of the reproductive organs
Thyroid Hormone
• Targets: cells
– Basal Metabolic Rate
•
•
•
•
↑oxygen consumption (thermogenesis)
Glucose absorption in GI
Lipolysis
Protein catabolism (adults)
– Heart rate
– Bone growth
• “growth hormone”
– Nervous system development
Goiter
Graves’ disease
• Autoimmune disease
– thyroid-stimulating
immunoglobulins
Adrenal Gland
• Capsule
• Adrenal Cortex
• Adrenal Medulla
Adrenal Gland
• Adrenal Cortex
– Zona Glomerulosa:
– aldosterone
– Zona Fasciculata
– glucocorticoids (cortisol)
– Zona Reticularis
– testosterone (androgens)
• Adrenal Medulla
– Epinephrine &
norepinephrine
Aldosterone
• Source
– Adrenal cortex: Zona Glomerulosa
• Target
– Kidneys: collecting ducts
• Na+ reabsorption
• elimination of K+
• Pathology
– Deficiency: Addison’s disease
– Excess: Conn’s syndrome
• Excess Na+: Hypertension and edema
• Loss K+: abnormal function of neurons and muscle
Figure 16.15 Major mechanisms controlling aldosterone release from the adrenal cortex.
Primary regulators
Blood volume
and/or blood
pressure
K+ in blood
Other factors
Stress
Blood pressure
and/or blood
volume
Hypothalamus
Kidney
Heart
CRH
Renin
Direct
stimulating
effect
Initiates
cascade
that
produces
Anterior
pituitary
Atrial natriuretic
peptide (ANP)
ACTH
Angiotensin II
Inhibitory
effect
Zona glomerulosa
of adrenal cortex
Enhanced
secretion
of aldosterone
Targets
kidney tubules
Absorption of Na+ and
water; increased K+ excretion
© 2013 Pearson Education, Inc.
Blood volume
and/or blood pressure
Glucocorticoids
• Source
– hypothalamus
• Cortisol Releasing
Hormone (CRH)
– Pituitary gland
• Adrenocorticotropic
hormone (ACTH)
– Adrenal cortex
• Glucocorticoids
– ESSENTIAL for life
– Continuous secretion
– permissive effects on
» Glucagon
» Epinephrine
Glucocorticoids
• Keep blood glucose relatively constant
– Gluconeogenesis: protein catabolism & lipolysis
– ↓glucose utilization:
• Decrease sensitivity to insulin
– "Saves" glucose for brain
• provide resistance to stress
• ↑ blood pressure
– vasoconstriction => quickly distribute nutrients to
cells
28
Glucocorticoids
• anti-inflammatory effects
– Inhibits diapedesis
– Inhibits the release of cytokines & antibody
production
• net Ca2+ loss from the body
– ↑catabolism in calcified bone matrix
29
Figure 16.17 Stress and the adrenal gland.
Short-term stress
Prolonged stress
Stress
Nerve impulses
Hypothalamus
CRH (corticotropinreleasing hormone)
Spinal cord
Corticotropic cells
of anterior pituitary
To target in blood
Preganglionic
sympathetic
fibers
Adrenal medulla
(secretes amino acid–
based hormones)
Catecholamines
(epinephrine and
norepinephrine)
Short-term stress response
• Heart rate increases
• Blood pressure increases
• Bronchioles dilate
• Liver converts glycogen to glucose and releases
glucose to blood
• Blood flow changes, reducing digestive system activity
and urine output
• Metabolic rate increases
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ACTH
Mineralocorticoids
Adrenal cortex
(secretes steroid
hormones)
Glucocorticoids
Long-term stress response
• Kidneys retain
• Proteins and fats converted
sodium and water
to glucose or broken down
for energy
• Blood volume and
• Blood glucose increases
blood pressure
• Immune system
rise
supressed
Cushing’s Syndrome
• Diabetes-like
– ↑plasma glucose
• Tissue wasting
– Muscle breakdown
– dark striation & stria
• protein breakdown
• obesity in the trunk, “moonface”, buffalo hump
– ↑appetite & ↑food intake
→ Extra fat deposits in the
trunk & face
• Virilization of female
– ↑↑adrenal androgen
Figure 16.16 The effects of excess glucocorticoid.
Patient before onset.
© 2013 Pearson Education, Inc.
Same patient with Cushing's
syndrome. The white arrow shows
the characteristic "buffalo hump" of
fat on the upper back.
Addison’s disease
Gonadocorticoids (Sex Hormones)
• Most weak androgens (male sex hormones)
– converted to testosterone in tissue cells, some to
estrogens
• May contribute to
– Onset of puberty
– Appearance of secondary sex characteristics
– Physiologically significant in females
•
•
•
•
pubic and axillary hair
pubertal growth spurt
sex drive
Estrogens in postmenopausal women
© 2013 Pearson Education, Inc.
Adrenal Medulla
• Medullary chromaffin cells
– epinephrine (80%) and norepinephrine (20%)
•
•
•
•
Vasoconstriction
Increased heart rate
Increased blood glucose levels
Blood diverted to brain, heart, and skeletal muscle
© 2013 Pearson Education, Inc.
Melatonin
• Source
– Pineal gland
• Melatonin
• Melatonin may affect
– Timing of sexual maturation and puberty
– Day/night cycles
– Physiological processes that show rhythmic variations
(body temperature, sleep, appetite)
Pancreatic hormones
Insulin
• hormone of absorptive
state
– Lowers blood glucose levels
• targets
– fat and muscle cells:
glucose uptake
• Glycogen synthesis
• Triglyceride synthesis
• antagonizes glucagon
Glucagon
• hormone of postabsorptive
state
– increases blood glucose levels
• targets
– Liver: Glycogenolysis
– Fat cells: lipolysis
• Promotes glucose sparing
for nervous system
– by diverting body cells to
utilizing other sources of
energy
17-38
Physiological Functions of Calcium
• signal molecule in signal transduction
• coagulation cascade (blood clotting)
• plasma calcium concentration affect
excitability of neurons
– hypocalcemia  Na+ permeability in neurons
 neurons depolarized  nervous system
hyperexcitable (tetany)
– hypercalcemia  Na+ permeability in neurons
 neuromuscular activity
Ca2+ Homeostasis: Bone
Remodeling
Calcitonin
• Source
– Thyroid gland: Parafollicular
cells
• Normalize plasma Ca2+
level (objective: Ca2+)
– ↓bone breakdown
• Inhibits osteoclastic activity
• Inhibits release of Ca2+ from
bone matrix
– Ca2+ uptake and incorporation
into bone matrix
Parathyroid hormone:
• Source
– parathyroid gland : Chief cell
• Normalize plasma Ca2+
level (objective: ↑Ca2+)
– ↑bone breakdown
• Stimulates osteoclastic
activity
– ↑renal reabsorption of Ca2+
– Promotes activation of
vitamin D
• ESSENTIAL for life