Quiz 7 - Hormones, Fatty Acid Metabolism, Regulation of Metabolism, Musculoskeletal system, Diabetes, Bone Physio Flashcards
Homeostasis
Physiologic ability to maintain a relative stable internal environment despite external changes.
4 features of feedback mechanisms
- System Variable
- Set Point
- Detector
- Corrective mechanism
Hormones
Chemical messengers secreted into the blood to alter rates of processes in target organs and cells.
Low concentrations produce effects.
Control long-term homeostatic processes of growth, development, metabolism, reproduction and internal environment regulation.
Endocrinology
Study of endocrine system and hormone action
Where do hormones bind?
Receptors on or in target cells
What do hormones control?
- Rates of enzymatic reactions
- Movement of ions or molecules across membranes
- Gene expression and protein synthesis.
Where are hormones produced?
Endocrine cells and organs
Where are hormones released?
Endocrine glands
Thyroid hormone
Made in thyroid, controls basal metabolism
Cortisol
Made in adrenal cortex, controls energy metabolism and stress responses.
Mineralcorticoids
Made in adrenal cortex, regulate plasma volume via effects on serum electrolytes
Vasopressin
Made in the posterior pituitary, regulates plasma osmolality via effects on water excretion
Parathyroid hormone
Made in the parathyroids, regulates calcium and phosphorus levels.
Insulin
Made in the B cells of the pancreas, regulates plasma glucose concentration.
Neurocrine
Secretion of hormones into the bloodstream by neurons
Endocrine
Secretion of hormones into the bloodstream by endocrine glands
Paracrine
Hormone molecules secreted by one cell affects adjacent cells
Autocrine
Hormone molecule secreted by a cell affects the secreting cell.
Three chemical classes of hormones
- Steroid hormones
- Peptide and protein hormones - 50 aas is a protein
- Amine hormones (tyrosine derivatives)
Lipophilic hormones
Fat-soluble
Steroid and thyroid hormones
Bind to intracellular receptors
Hydrophilic hormones
Water-soluble
All other hormones
Bind to extracellular receptors and trigger signaling cascades
Amine hormones
Thyroid hormones and Catecholamines (epinephrine, norepinephrine)
Derived from amino acid tyrosine
Thyroid hormones
Thyroxine
Derived from Tyrosine (Amine hormone)
Bind to nuclear receptors
Catecholamines
Epinephrine and Norepinephrine
Derived from Tyrosine
Bind to cell surface receptors
Peptide and Protein hormones
Water soluble
Most numerous hormones
Often produced as preprohormones that are cleaved and modified
Often carried inactively bound to a protein to carry it though the blood
Modification of Peptide hormones
- Genes code for mRNA, translated into preprohormone
- Preprohormone formed in ER, broken into prohormone in the Golgi
- After posttranslational modification in the Golgi, peptide hormone is secreted
Prohormones exist for which hormones?
Insulin Somatostatin Glucagon Enkephalin ADH (Vasopressin) Gastrin Parathyroid hormone Calcitonin ACTH
Signal transduction/Extracellular Hormone Receptor Pathway
Hydrophilic hormone binds to cell surface GPCR, G-protein activates second messenger (like cAMP), 2nd messenger activates other effects
Steroid hormones
Derived from Cholesterol
Lipid Soluble
Must be carried in plasma by plasma blinding globulins
“Bound” steroid hormones serve as a reservoir
Plasma binding globulins
Bind to steroid hormones in the plasma
Albumin, testosterone binding globulin, thyroxine binding globulin
Intracellular Hormone Receptor Pathway
Lipid soluble hormones cross membrane, bind to intracellular receptors (hormone-receptor complex), HRC binds to DNA and acts as transcription factor, directing protein synthesis
Aromatase Enzyme/Aromatization
Enzyme that converts “Free” androgen hormones into estrogens.
Occurs in trophoblastic tumors
Occurs normally in adipocytes, liver, brain.
5 Factors that effect circulating hormone levels
- Synthesis and secretion rate
- Rates of degradation and uptake
- Receptor binding/availability of receptors
- Affinity of hormone for plasma carriers
- Free hormones equilibrate with bound hormones
Negative feedback regulation of hormones
Hormone shuts down stimulating or releasing factors, ending hormone action
Positive feedback regulation of hormones
Uncommon, hormones enhance releasing and stimulating factors
Occurs in childbirth (parturition)
Long-loop feedback
Target gland hormone may feedback and inhibit its production
Short-loop feedback
Stimulating hormone (trophic hormone) inhibits hormone production
Pituitary gland anatomy
- Anterior pituitary - pars anterior
- Intermediate lobe - pars intermedia
- Posterior pituitary - neurohypophysis/pars nervosa
- Infundibulum - stalk that links to hypothalamus
Hypothalamo-hypophysial portal system
Capillary system that links secretory neurons of hypothalamus with storage portion of anterior pituitary
Pituitary hormone
Ocytocin
ADH
Adrenocorticotrophic hormon (ACTH)
Hypothalamic-Pituitary-Adrenal Axis (HPA)
Responsible for adaptation of stress response, regulates many body functions
Feedback control of Osmolality
Vasopressin/ADH made in hypothalamus, secreted from neurohypophysis/Posterior pituitary. Hypothalamic osmoreceptors control release of ADH. ADH causes aquaporins to be inserted into collecting duct of renal tubules to reabsorb water
Adrenal gland hormones
- Mineralcorticoids - Aldosterone, secreted by zona glomerulosa (top layer of adrenal cortex)
- Glucocorticoids - Cortisol, secreted by zona faciculataa (Middle layer)
- Adrenal androgens - Dehydroepiandrosterone (DHEA), secreted by zona reticularis (bottom layer)
- Epinephrine (80%) and Norepinephrine (20%) - secreted by adrenal medulla
Aldosterone
Mineralcorticoid
Promotes sodium reabsorption and potassium excretion by renal tubules
Imbalanced increase causes hypokalemia and muscle weakness
Imbalanced decrease causes hyperkalemia and cardiac toxicity
Aldosterone escape - persistent elevated EC fluid volumes causes loss of excessive Na+ and water, causing dehydration
Cortisol
Glucocorticoid
Stimulates gluconeogenesis, increasing serum glucose
Has anti-inflammatory effects, adversely affects immunity, eosinophil and lymphocyte counts decreasae
Adrenal androgens
DHEA, DHEAS, androstenedione, 11-hydroxyandrostenedione
Formation of progesterone and estrogen via aromatization
Development of sex organs
ACTH effects androgen release, so secretion parallels cortisol
Acute stress
Fight or flight response
Epinephrine and norepinephrine
Blood glucose rises, BP rises, Bronchioles dilate
Chronic stress
Steroid hormones secreted
Immune suppressed
Water retention
Eventual exhaustion
Cortisol regulation
Negative feedback loop
Endocrine gland hyposecretion
Hormone deficiency (Ex. Type 1 Diabetes)
Hormone resistence
Ex.) Type 2 Diabetes
Hormone Excess
Tumors of glands produce excessive hormone
Ex.) Acromegaly - gigantism, too much growth hormone. Treated with somatostatin
Ex.) Graves disease - antibodies bind to hormone receptors causing thyroid hormone release
Addison’s Disease
Adrenal insufficiency, leads to hypoglycemia, weight loss, postural hypertension, weakness, GI distubances
Cushing’s Syndrome
Excess ACTH causes excess cortisol
Moon face, buffalo hump, buisability, poor wound healing
Hypothyroidism
Insufficient thyroid hormone
Fatigue, constipation, dry skin, depression, enlarged thyroid
Hashimoto’s disease - autoimmune hypothyroidism
Hyperthyroidism
Excess thyroid hormone
Weight loss, fast heart rate, exopthalmos (bulging eyes), enlarged thyroid
Grave’s disease - autoimmune hyperthyroidism
Dietary Lipid processing
- Bile salts emulsify dietary fats in the small intestine, forming mixed micelles
- Intestinal lipases degrade trigycerides
- Fatty acids and other breakdown products taken into intestinal mucosa, converted into triglycerides
- Triglycerides incorporated with cholesterol and apolipoproteins into chylomicrons
- Chylomicrons move through lymphatic system and into blood vessels
- Lipoprotein lipase in blood vessels converts triglycerides into fatty acids and glycerides. Fatty acids enter cells
(C chains 14C or longer need protein to transport across membrane) - Fatty acids are oxidized as fuel or reesterified into storage
How are fatty acids transported?
Albumin carries free fatty acids in serum
Lipoproteins carry triglycerides and cholesterol (Chylomicrons)
4 classes of Lipoproteins
- Chylomicrons - take triglycerides from gut to muscle, liver, etc.
- Very Low Density Lipoprotein - created in liver, sent to tissues
- Low Density Lipoprotein - made from VLDL when triglycerides are removed at body cells
- High Density Lipoprotein - has low triglyceride content, collects lipids from vasculature
Triacylglycerol cycle
Triacylglycerol (triglycerides) cycles between adipose tissue, blood and liver to mobilize fatty acids for energy. Imbalanced towards triglycerides and storage rather than free fatty acids for energy
Adipose triglyceride mobilization
Glucagon binds to adipose cell surface receptor, triggars G protein, adenylyl Cyclase, cAMP cascade. Protein Kinase A triggers Triglyceride breakdown into free fatty acids that are released into the bloodstream.
Fatty acids are brought into body cells via a transporter, then are used for Beta Oxidation.
Lipid Catabolism
Glycerol enters glycolysis, produces 5% of energy from fatty acids
Fatty acids form Acyl-CoAs, generate 95% of energy from fatty acids
Acyl-Carnitine/Carnitine Transporter
Carnitine used as carrier to bring Carbon chains from cytosol, across intermembrane space and into matrix of mitochondria
3 stages of fatty acid oxidation
- Beta Oxidation - breaks fatty acids into acetyl-CoAs and generates NADH and FADH2
- Citric Acid Cycle - Utilizes acetyl-CoAs to generate NADH and FADH2
- Oxidative Phosphorylation - Utilized NADH and FADH2 to generate ATP. Generates 108 ATP from one 16C chain
Fatty Acid Beta Oxidation
Removes a 2 carbon piece at the Beta carbon, producing 1 NADH and 1 FADH per Acetyl-CoA produced
What happens to Acetyl-CoA after production in Beta Oxidation?
- Enters Citric Acid Cycle
- Converted into Ketone Bodies to use for energy production when glucose is low.
- Formed back into fatty acids
Citrate shuttle
Acetyl-CoA is produced in mitochondria matrix, but lipid synthesis occurs in the cytoplasmic space. OXA is converted into Citrate using Acetyl-CoA. Citrate leaves the mitochondria and is converted back into OXA, releasing Acetyl-CoA into the cytoplasm.
Acetyl-CoA Carboxylase
Adds a CO2 to Acetyl-CoA, creating Malonyl-CoA, which is used to create fatty acid chains
Fatty Acid Synthase
Enzyme binds Malonyl-CoA to Acetyl-CoA, releasing CO2 and using NADPH. Creates a 4 Carbon chain. Repeats to add 2C at a time.
Creates palmitate - 16:0 fatty acid. Further processing can create an 18:1 fatty acid
NADPH is an electron donor
Essential Fatty Acids
18:2 and longer chains cannot be created by mammals and must be ingested. Linoleate is first essential fatty acid
Regulation of Fatty Acid Synthesis and breakdown
Insulin promotes phosphatase activation of Acetyl-CoA Carboxylase, promoting Fatty Acid Synthesis.
Glucagon promotes PKA inactivation of ACC, suppressing fatty acid synthesis.
Production of Malonyl-CoA via ACC suppresses carnitine acyl-transferase I which initiates Beta Oxidation, thus suppressing Beta Oxidation
Phosphatidic acid
Precursor to phospholipids and triglycerides
What is Cholesterol formed from?
Acetyl-CoA
Cholesterol uses
Lipoprotein and steroid hormone formation
Atherosclerotic Plaque formation
Cholesterol accumulates in macrophages (foam cell), which apoptoses and deposits cholesterol-rich plaque in artery lumens.
Autonomic Nervous System
Sympathetic and Parasympathetic control of organ function. Direct contact from nervous system to organs
Neuroendocrine system
Hormone control of organ function. Indirect control via the HPA axis - Hypothalamus, Pituitary, Adrenals
Hypothalamus methods of control
- Direct - autonomic - innervation of pre-ganglionic neurons
- Indirect - Hormonal - release of pituitary and adrenal cortex hormones
3 Parts of the Autonomic Nervous System
- Sympathetic - fight or flight
- Parasympathetic - rest and digest
- Enteric nervous system - digestive system
Carotid Body
Site of chemoreceptors that detect blood O2/CO2 composition. Autonomic control of cardiac function
Autonomic control of cardiac function
Chemoreceptors and baroreceptors analyze blood
Sympathetic - norepinephrine - increases heart rate and vasoconstricts
Parasympathetic - cholinergic - decreases heart rate and vasodilates
Increased BP inhibits tonic sympathetic activity and activates vagal parasympathetic activity
Baroreceptors
Detect blood pressure. Autonomic control of cardiac function
What does the liver regulate?
Blood sugar
Carbohydrate storage (glycogen) and regulation
Amino acid content
Lipid formation and mobilization
First pass metabolism - blood enters directly from gut
What does the pancreas regulate?
Insulin release during high blood sugar
Glucagon release during low blood sugar
Duodenum pH buffering
Protease release
What does the gallbladder regulate?
Bile salts release to degrade lipids
What’s important about Glucose-6-Phosphate
It is the branching point - can become glucose, glycogen, go down pentose phosphate pathway, become acetyl-CoA
Leptin
Triggers satiety signals in the hypothalamus. Eat less, metabolize more
Grehlin
Triggers hunger signals in the hypothalamus. Eat more, metabolize less
Insulin release pathway
Beta Cells maintain voltage potential. Increasing concentration of ATP leads to blockage of K+ out. Depolarization results, opening Ca2+ channels in. Ca2+ triggers release of insulin granules
Glucagon release pathway
Alpha cells work just like Beta cells, only ADP concentration increase blocks K+ channels
Superior/Cranial/Rostral
Head end
Inferior/Caudal
Feet end
Proximal
Toward main body
Distal
Away from main body
Median
Midline, divides right from left
Medial
Close to midline to side
Lateral
Away from midline to side
Coronal
Divides front from back
Anterior/Ventral
Front
Posterior/Dorsal
Back
Saggital
Median plane in skull
Transverse
Cross section cut parallel to ground
Axial
Transverse plane in skull
Extension of neck
Tilt head back
Flexion of neck
Tilt head forward
Rotation
Circular motion around a joint
Axial skeleton
Head, vertebrae, ribs, sternum
Appendicular skeleton
Everything else, including the pelvis and scapula and clavicles
Numbers of ribs
7 pairs of true ribs
3 pairs of false ribs
2 pairs of floating ribs
Scapula landmarks
Superior angle, supraspinous fossa, scapular spine, acromion, coracoid process, intraspinous fossa, medial border, subscapular fossa
Pelvic bones
Os Coxae - 3 bones fused
Ilium, Ischium, Pubis
Synarthroses
Immovable joints
Fibrous - Skull sutures, Gomphoses (teeth)
Diarthroses
Freely movable
Synovial
Limits to joint movement
Bones, Muscles, ligaments, other tissue
Superficial back muscles
Trapezius Levator scapulae Rhomboid major and minor Latissimus dorsi Innervated by ventral rami
Trapezius
Spinal accessory nerve
Rotation of scapula for abduction of arm beyond 90 degrees
Extends neck
Levator Scapulae
Dorsal scapular nerve
Elevates scapula
Rhomboid major and minor
Dorsal scapular nerve
Retracts, adducts scapula
Latissimus dorsi
Thoracodorsal nerve
Adducts humerous
Deep back muscles
Spenius muscles Erector Spinae muscles Transversospinalis muscles Suboccipital muscle group Innervated by dorsal rami
Splenius muscles
From back of head to spinal column
Erector Spinae muscles
Iliocostalis muscles - from ilium of pelvis to ribs
Longissimus muscle - from lumbar all the way to cervical
Spinalis muscle - along spinous processes in thoracic region
Tranversospinalis muscles
Semispinalis - Along spinous processes from Occipital to thoracic
Multifidus - Along spinous processes from sacrum to ribs - lower back pain muscle
Suboccipital muscles
Rectus Capitis Posterior Minor and Major Obliquus Capitis Inferior and Superior Suboccipital nerve dorsal ramus of C1 Bilateral contraction extends head/neck Unilateral contraction rotates head to same side
Obliquus Capitis Superior muscle
Contraction tilts head like a curious dog
Deltoid
Axillary nerve
Abduction of arm from 15 degrees to 90
Subscapularis
Upper and lower subscapular nerves
Glenohumeral internal rotation
Supraspinatus
Suprascapular nerve
Glenohumeral abduction to 15 degrees
Infraspinatus
Suprascapular nerve
Genohumeral external rotation
Pectoralis major
Lateral and medial pectoral nerves
Pectoralis minor
Medial pectoral nerve
Glenohumeral adduction
Subclavius
Nerve to subclavius
Glenohumeral adduction
Serratus Anterior
Long thoracic nerve
Scapula protraction
Brachial plexus
Ventral rami from C5-T1 Meet in 3 trunks Divide Separate into 2 anterior cords and one posterior cord Many nerves branch from here
What brachial plexus nerves branch in what region?
Roots - Dorsal Scapular Nerve off C5, Long Thoracic Nerve off C5-C7, Nerve to Subclavius off C5-C6
Trunks - no nerves
Divisions - no nerves
Posterior Cord - Upper Subscapular nerve, Thoracodorsal nerve, Lower subscapular nerve, axillary nerve
Lateral Cord - Lateral Pectoral Nerve
Medial cord - Medial pectoral nerve
Diabetes Mellitus
Inability of the body to regulate glucose through insulin
Type 1 Diabetes
Autoimmune loss of insuline-producing B-cells
Genetically Linked
Juvenile onset
Insulin-dependent
Type II Diabetes
Insensitivity to insulin
Lifestyle and genetics - weight gain and obesity
Adult onset (though becoming common in juveniles)
Non-insulin dependent
Gestational Diabetes
Develops during pregnancy
Fetus induces changes in metabolism
Causes a predisposition to Type II later in life
Frequency of Diabetes in the US
29.1 million with disease - 9.3% of US population
Symptoms of Type I diabetes
Polyuria and Thirst Weakness Polyphagia and weight loss Blurred Vision Peripheral Neuropathy Nocturnal Enuresis Sweet smelling breath and urine Impaired wound healing
Symptoms of Type II diabetes
Polyuria and thirst Weakness Blurred Vision Peripheral Neuropathy Sweet smelling breath and urine Impaired wound healing
What does Type I diabetes ultimately cause?
Lack of insulin leads to a dysregulated metabolic state of extreme fasting and starvation
Pathogenesis of Type I diabetes
Loss of insulin signaling - Glucose not taken into cells, remains in blood
Systemic mimicry of prolonged fasting - Cells unable to take in glucose, glucose release from glycogen and adipose increases, ketone bodies created and released
Ketoacidosis
Uncontrolled Type I causes ketoacidosis by release of ketone bodies in attempt to “feed” body cells. Leads to osmotic diuresis –> Dehydration –> Electrolyte imbalance –>Coma and tachycardia
Treatment of Type I diabetes
- Insulin administration - Injections or pump
- Glucose monitoring
- Diet - low carbohydrate
Insulin administration
Different types
Basal insulin - maintains low-level systemic insulin
Bolus - Given when food is consumed
Pathogenesis of Type II diabetes
Progressive increase in fasting glucose due to reduced insulin sensitivity followed by a degeneration of insulin production
As insulin resistance increases, B-cells try to compensate, experience stress
B-cells fatigue, fail and degenerate
How might adipose signaling drive type II diabetes?
Enlargement of adipocytes releases protein (MCP-1) that brings in macrophages. Macrophages release TNF alpha, releasing fatty acids. Lipids deposit in improper places, interfering with glucose movement, producing insulin resistance.
Type II diabetes management
- Lifestyle - reduced carbohydrate and sugars, increase physical activity, maintain healthy body weight
- Oral Hypoglycemics - increase insulin secretion, increase insulin sensitivity, decrease carbohydrate absorption
- Insulin - required when B-cell mass degenerates
Type II drugs
- Sulfonylurease - increase B-cell insulin secretion by binding close K+ channels
- Metformin - Uncouples Oxidative Phosphorylation, reduces liver gluconeogenesis and lipogenesis
- Peroxisome Proliferator-activated receptor agonists - increase glucose transporter expression
- Alpha-glucosidase inhibitors - Prevent carbohydrate absorption
- Drug combinations
How is diabetes detected
- Urinalysis
- Glucose monitoring
- HBA1c - measure of glycolated hemoglobin
- Glucose tolerance test
- C-peptide test - cleavage product of proinsulin
Hypoglycemia
Low blood sugar
Hyperglycemia
High blood sugar
Long-term diabetic complications
Cardiovascular Disorder - heart disease, stroke, peripheral vascular disease
Blindness - glaucoma, retinopathy
Kidney disease
Neurologic Complications - Peripheral neuropathy, autonomic neuropathy, erectile dysfunction
Impaired wound healing and amputation
Plasma calcium
Vital 2nd messenger, necessary for muscle contraction, coagulation, nerve function
Bone Calcium
99% of body calcium
- Readily exchangeable reservoir
- – 500 mmol/day in and out - Slowly exchangeable stable calcium
- – Bone remodeling, 7.5 mmol/day exchanged with ECF
What does phosphate do?
- Component of ATP
- Biological buffer
- Modify proteins
How is phosphate regulated?
Many of the same systems that regulate Ca2+ regulate phosphate, but sometimes in reciprocal fashion.
Body Phosphorus
500-800 g
85-90% in skeleton
300 mg/d in and out of bone per day
What foods are high in phosphate?
Dark greens, beans, shellfish, lean meat
NaPi-lla
Sodium dependent Phosphate cotransporters
Absorb Pi in the duodenum and small intestine
Stimuli that increase Ca absorption including vitamin D increase these transporters in the intestine
Parathyroid hormone function
Secreted by Chief Cells of Parathyroid Glands
Mobilize calcium and bone and increase urinary phosphate excretion
1,25-Dihydroxycholecalciferol (1,25 (OH)2D)
Steroid hormone formed from Vit. D in skin via sun processed in liver and kidneys
Increases calcium absorption from the intestine and increase Ca2+ in bone
Downregulates PTH formation and release
Calcitonin
Secreted by parafollicular cells in the thyroid gland
Lowers free calcium by:
1. Inhibiting Ca2+ reabsorption in intestines
2. Inhibiting osteoclast activity
3. Stimulating Osteoblast activity
4. Inhibits Ca2+ reabsorption in the kidneys
Vitamin D
Sterols produced by the action of ultraviolet from the sun on certain provitamins
Fatty fish
90% obtained through exposure to sunlight
Hydroxylation reactions activate it
Other hormones that act on Ca
Glucocorticoids - lower plasma Ca levels by inhibiting osteoclast formation and activity
Growth hormone - increases Ca excretion in urine, but has greater increase of intestinal Ca absorption
Estrogens - Prevent osteoporosis by inhibiting the stimulatory effects of cytokines on osteoclasts
Insulin - Increases bone formation
Compact/Cortical bone
Makes up outer layer of bone
80% of bone in body
Trabecular/spongy bone
Inside cortical bone
remaining 20% of bone
Epiphyses
Specialized areas at end of long bones
Epiphysial plate - site of actively proliferating cartilage
Width of the epiphysial plate is proportional to the rate of growth and is affected by hormones
Growth ceases with epiphysial closure
Osteoclasts
Erode and absorb previously formed bone
Attach to bone via integrins, creating sealing zones.
Acidify area to dissolve hydroxyapatites
Proteases break down collagen
Digested products endocytosed, then released
Osteoblasts
Modified fibroblasts that lay down Type 1 Collagen to form new bone
Osteopetrosis
Osteoclasts are defective and unable to resorb bone
Osteoblasts opperate unopposed
Bone density increases and growth becomes distorted, few foramina for nerves
Osteoporosis
Relative excess of osteoclast function results in loss of bone matrix and high risk of fractures
Involutional osteoporosis - as age increases, bone loss increases
Treatment: bisphosphonates - inhibit osteoclasts
Rickets/Osteomalacia
Vitamin D and/or Ca2+ deficiency
Rickets in children - bowing of weight-bearing bones, dental defects
Osteomalacia in adults - muscle weakness and bone pain, enamel hypoplasia