Endocrinology Flashcards
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Direct communication
- Transportation via gap junctions or connexins
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Contact communication
- Information processing via molecules integrated into the membrane
- Typical in cells of the immune system
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Communication by secretion
- Cells are located relatively far away
- Molecules are secreted and received
- Typical of the immune and nervous system
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Cytoskeletal communication
- Metabolism of a cell is influenced
- This is relayed by the cytoskeletal system
Give the types of cell communication
- Direct communication
- Contact communication
- Communication by secretion
- Cytoskeletal communication
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Classical endocrine effect
- Cells secrete hormones
- Hormones reach recipient cells via blood stream
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Paracrine effect
- Signals do not enter the blood
- Acting on cells of the same tissue adjacent to the original cell
- Signals are called local chemical mediators
Give the fate of local chemical mediators in the paracrine system
They can be either:
- Broken down
- Immobilised
- Taken up by cells
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Autocrine effect
- A special form of paracrine effect
- Signal-producing cell sends and receives its own signals
List the types of information processing in the endocrine system
- Classical endocrine effect
- Paracrine effect
- Autocrine effect
- Neurotransmitters
Which part of the CNS is the integrator of the endocrine system?
The hypothalamus
The function of the hypothalamus in the endocrine system depends on…
- The levels of hormones
- Information arriving from:
- Nervous system
- Immune system
Title this figure
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Feedback within the endocrine system
What is the function of the feedback mechanism in the endocrine system?
It allows fine-tuning in the regulation of signals
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Hypothalamus
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Pituitary gland
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Target organ
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“Smart” end-users: Peripheral cells
Give the classifications of endocrine feedback mechanisms
- Long feedback
- Short feedback
- Ultra-short feedback
Give an example of where long feedback occurs
Between:
- A peripheral gland
- Hypothalamus
Give an example of where short feedback occurs
Between:
- A peripheral gland
- Pituitary gland
Give an example of where ultra-short feedback occurs
Between:
- Hypothalamus
- Pituitary gland
Which hormones are used to demonstrate the classical regulatory pathway?
Thyroid hormones
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Thyroid feedback
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Hypothalamus
TRH
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Hypophysis
TSH
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Thyroid gland
Thyroxine synthesis increases
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Blood vessel:
Thyroxine level increases
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Give examples of IC “second messengers”
- cAMP
- cGMP
- Ca2+
- Diaglycerol (DAG)
- Inositol triphosphate (IP3)
Which processes occur between:
- Signals being received
- The appearance of biological effects
Signal transduction processes
What are the reasons that a hormone-like substance could have varying effects on different cells?
- There are separate receptors in the different tissues
- The receptor is the same but a different signalling pathway is initiated
Title the figure
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Scatchard analysis
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Bmax (No. of binding sites) given by the point of intersection
What is a Scatchard analysis used for?
Used for measuring the properties of receptor-ligand interaction
Which parameters can be estimated from a Scatchard analysis?
- The total number of binding sites
- Strength (affinity) of binding between the receptor and the ligand
Title the figure
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Regulation of receptor number
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- Either:
- Long lasting hormone treatment
- The decrease of cellular metabolic needs
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“Down-regulation”
Inhibition of receptor expression
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Either:
- Removal of the endocrine gland
- Increase of cellular metabolic needs
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“Up-regulation”
Facilitation of receptor expression
How do lipophilic hormones have an effect on cells?
- They easily pass the cell membrane
- Binding to cytoplasmic proteins
- They then reach the nucleus
- Modification of genetic expression of proteins
How do water-soluble/hydrophilic peptides and glycoprotein hormones have an effect on cells?
Exert actions by binding to membrane surface receptors
G-protein dependent transduction outcomes
- Migration of G-protein to ion channel protein, activating/inactivating it
- Activate enzymes bound to the IC side of the membrane
- Influence adenylate cyclase activity → IC cAMP conc.
- Control phospholipase C activity → Produces messengers
- Control PLA2 enzyme → Arachidonic acid
Describe the receptor of G-protein independent transduction
The receptor is a transmembrane protein:
- EC ligand binding part
- Central part
- IC part which exhibits phosphorylase activity
Describe G-protein independent transduction
- Ligand bond formation
- IC polypeptide chain phosphorylates
- Receptor activates
- Biological action
Describe cell activation when the receptor is in the cytoplasm
- Lipophilic hormones pass the cell membrane
- Hormones bind to cytoplasmic proteins (receptors)
- Receptor-ligand complex formation
- DNA-binding domain of the receptor protein ‘finds’ HRE
- Biological response initiated through transcription of a protein
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Fine structure of the nuclear receptor
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Lypophilic hormone
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LBD
Ligand binding domain
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DNA-BD
DNA binding domain
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HRE
Hormone-responsive element
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BPE
Basal promoter element
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VD
Variable domain
The function of the VD
Locating of the base-pair segment of the DNA
Specific to the particular hormone
The function of HRE
Binds the DBD
DBD
DNA binding domain
Amino acid segment of the hormone-receptor complex
The function of the BPE
- Activated by receptor-DNA complex
- Expression of the structural gene begins
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The receptor in the form of an ion channel
Describe the structure of a receptor which is acting as an ion channel
- 5 membrane-integrated domains
- Ligand binding site on the EC side
- 2x alpha subunits
- 2x beta subunits
- 1x delta subunit
Give examples of receptors which are ion channels
- n-ACh-R (Nicotinic acetylcholine receptor)
- Glutamate receptors
- Anion receptors
Nicotinic acetylcholine receptors can be inhibited by…
d-tubocurarine
n-ACh-R can be stimulated/inhibited by substances affecting the…
Receptor’s 5 subunits
What are the states n-ACh-R can be in?
- Closed (before ACh binding)
- Open (After ACh binding)
Describe the processes after ACh binds to the receptor
- Conformational change
- Cation channel opens (“open state”)
- Flow of cations
- Local excitatory potential formed
- AP is triggered
Describe the closing of n-ACh-R
- The open channel becomes inactivated
- Ligand bond still exists
- Change of conformation doesn’t allow cation flow
- Channel is “inactive”
- Dissociation of the ligand
- Channel closes
Give the main groups of glutamate-sensitive receptors
- NMDA receptor
- AMPA receptor
- Kainate-receptor
NMDA receptor
- Function
N-metil-D-aspartate
- Binding Mg2+ keeps receptor closed
- Mg2+ dissociated after receptor activation
- Ca2+ influx maintains a lasting effect
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Opening of anion-receptors causes
Hyperpolarisation of CNS inhibitory synapses
What can cause hyperpolarisation of anion receptors
Nonspecific anions
- Cl-
- HCO3-
Give the main mediators of anion-receptors
- GABA
- Glycine
The function of GABA in the anion-receptor
- Either GABA-A / GABA-B
- GABA-B activation:
- Decrease IC cAMP
- Affects K+ channels
G-protein structure
- 3 subunits form a complex:
- Alpha subunit + GDP
- Beta subunit
- Gamma subunit
G-protein mechanism of action
- The ligand binds to the EC receptor
- Conformational change in the 7-M protein
- Beta + gamma subunits bind to the IC side of the receptor
- Alpha subunit conformational change
- Alpha subunit binds GTP
- Alpha subunit-GTP complex liberated
- Stimulates/inhibits ion channel/enzyme
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Describe the return of G-protein to its resting state
- GTP → GDP
- Alpha subunit binds to gamma + beta again
- G protein → Resting state
Describe Gs effect
- Activated G-protein migrates to a remote ion channel protein
- Activates the channel
Describe Gi effect
- Activated G-protein migrates to a remote ion channel protein
- Inactivates the channel
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- M2 ACh-R
- K+ channel opens
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- alfa2 type R
- K+ channel opens
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- D2 type R
- K+ channel opens
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- GABA type R
- K+ channel opens
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- S2 type R
- K+ / Ca2+ channel opens
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- OP type R
- Ca2+ channel opens
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Adenylate cyclase mechanism
Summarise the adenylate cyclase mechanism
- Influenced by G-proteins
- Gs: adenylate cyclase activity ↑
- Gi: adenylate cyclase activity ↓
Describe the steps of the Gs mechanism
- Glucagon mobilises Gs G-protein
- Liberates hepatic glycogen stores
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Describe the steps of the Gi mechanism
- alpha2-adrenergic receptor activated
- IC cAMP levels ↓
List receptors of the Gs pathway
- Prostacyclin
- Dopamine D1
- Catecholamine beta
- Anterior pituitary
- Histamine H2
- 2-type ADH
List receptors of the Gi pathway
- Dopamine D2
- Alpha1 catecholamine
- Some glutamate
- Some opioid
Title the figure
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Phospholipase C mechanism (PLC)
Give the steps of the phospholipase C (PLC) mechanism
- Activation of G-protein
- Stimulates Phospholipase C
- Converts membrane phospholipids → IP3/DAG
IP3
- Binds to IP3 receptor (on the surface of Ca2+ sequesters)
- The receptor is an ion channel
- IP3 opens the channel
- Increasing IC Ca2+
- Cellular effects
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DAG
- Similar behaviour to cAMP
- Activates type-C protein kinases
- Triggers several phosphorylation pathways
- Biological effects
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Give examples of ligands in the PLC mechanism
- ACh
- Histamine
- Purin
- PGE
- TXA2
- ADH
- Oxytocin
All of which release Ca2+
Give the steps of the Phospholipase A2 (PLA2) mechanism
- G-protein activation
- Converts phospholipids → arachidonic acid (substrate)
- Arachidonic acid → Several products
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Besides active G-proteins, what else can activate the PLA2 mechanism?
Ca2+
Arachidonic acid can pass through which further pathways?
- Lipoxygenase pathway
- Cyclooxygenase pathway
- Epoxygenase pathway
List the products of the lipoxygenase pathway
- Leukotrienes (LT)
- Lipoxins (LX)
List the products of the cyclooxygenase pathway
- Prostacyclins (PGIs)
- Prostaglandins (PGs)
- Thromboxanes (TXs)
Describe the mechanism when a receptor is also an IC enzyme
- Ligand bond formed on the outer surface
- IC polypeptide chain phosphorylates
- Activation of the receptor
- Biological action
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Give an example of direct enzyme stimulation
Insulin receptor
The receptor is able to phosphorylate itself and other proteins on the IC part of the cell
Auto-phosphorylation
- Self phosphorylating enzyme phosphorylates tyrosine residues of the IC receptor sequence
- Phosphorylated tyrosine residues bind intracellular proteins
- Specific IC responses elicited
Describe the processes after autophosphorylation
- Autophosphorylation
- Receptor-enzyme complex is taken up by the cell
- Inactivation
Describe the figure
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- Tyrosine residues are present in the enzyme’s IC domain
- Ligand binding
- Phosphorylation of IC regulatory proteins (RP1+RP2)
- Biological effects
The hypothalamus is divided into which parts?
- Magnocellular area (with large cells)
- Parvocellular area (with small cells)
Describe the movement of hormones from the hypothalamus
- Hormones produced in the parvocellular area → Adenohypophysis
- Hormones produced in the magnocellular area → Neurohypophysis
Which nuclei are found in the magnocellular area?
- Supraoptic nucleus (Oxytocin production)
- Paraventricular nucleus (ADH production)
Which nuclei are found in the parvocellular area?
- Ventromedial nucleus
- Dorsomedial nucleus
- Infundibular nucleus
Inhibit/release substances which can reach the adenohypophysis
Describe the transport of neurosecretions from the parvocellular area
- Parvocellular area
- Portal circulation of pituitary stalk via axons
- Arrive at the adenohypophysis
- Influence production + release of hormones into the blood
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Describe the transport of neurosecretions from the magnocellular area
- Magnocellular area
- From the site of production (Neurone)
- The site of release (Neurohypophysis)
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Title the figure
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Axonal transport
Describe the steps of axonal transport
- Peptide travels from hypothalamic cell → axon
- First capillarisation (Median eminence)
- Portal circulation
- Second capilarisation (anterior pituitary)
- Cells of anterior pituitary
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Basal membrane
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Axonal transport, neurosecretion
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First capillarisation (Median eminence)
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Portal circulation
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Second capillarisation (anterior pituitary)
Which portal vessel do peptides travel down in axonal transport?
Pituitary stalk
Give the proteins of axonal transport
- Kinesin (Transport from soma to synapse)
- Dynein (Returning of residues to the soma)
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In axonal transport, what determines the direction of transport of proteins?
Polarity
Parvocellular areas synthesise releasing and inhibitory substances which influence…
Tropic-hormone production of the adenohypophysis
Hypophyseotrop hormones
Hypothalamic substances that influence production + release of the pituitary gland
Give the parvocellular hormone systematic names
- RH/RF (Releasing hormone/ Releasing factor)
- IH/IF (Inhibiting hormone/ Inhibiting factor)
- ’+’ (Facilitates synthesis + secretion hormones)
- ’-‘ (Inhibits hormone synthesis and release)
E.g TSH-RH = Thyrotropin hormone releasing hormone
In adenohypophyseal systematic naming, what do the following abbreviations mean (Prior to ‘RH’ or ‘RF’)?
- T
- C
- Gn
- G
- P
- M
- T = Thyrotropin, TSH
- C = Corticotropin, ACTH
- Gn = Gonadotropin, FSH/LH
- G = Growth hormone, STH
- P = Prolactin, PRL
- M = Melanocyte stimulating hormone, MSH
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- TSH+
- Thyroliberin
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- ACTH+
- Corticoliberin
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- FSH+, LH+
- Gonadoliberin
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- GH+
- Somatoliberin
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- PRL+
- VIP, TRH
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- MSH+
- MSH-RH
List the releasing factors (short name)
- TRH
- CRF
- GnRH
- GRF
- PRF
- MRF
Function: Thyrotropin-releasing hormone
- Stimulates thyroid gland
- Stimulates hormone release
Function: Corticotropin-Releasing Factor
- Adrenocorticotropin (ACTH) stimulating hormone
- Facilitates synthesis + release of:
- ACTH
- MSH
- Endogenous opiates
- Stimulating + splitting + synthesis of POMC
Function: Gonadotropin-releasing hormone
- Facilitates synthesis + release of:
- FSH (Follicle stimulating hormone)
- LH (Luteinising hormone)
- In males + females
Function: Growth hormone releasing factor (GRF)
Synthesis + release of growth hormone
Function: Prolactin-releasing hormone (PFR)
- Prolactin synthesis + release
- Lactation
- Ovulation in the rat
What are the main parvocellular inhibiting factors?
- Dopamine
- Somatostatin
- GABA
- VIP
In adenohypophyseal systematic naming, what do the following abbreviations mean (Prior to ‘IH’ or ‘IF’)?
- G
- P
- M
- G = Growth hormone, somatotropin, STH
- P = Prolactin, PRL
- M = Melanocyte-stimulating hormone, MSH
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- TRH-, PRL-
- TSH-IH, PRL-IH
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- GH-
- GH-IH, somatostatin
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- PRL-
- PRL-IH
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- GH+
- MSH-IH, Melatostatin
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- General, an indirect inhibitor
- Norepinephrine
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- General, an indirect inhibitor
Function: GIF
- Systematic name for Somatostatin
- GIF = Growth hormone inhibiting factor
- Somatotropin inhibiting hormone
Function: PIF
- Systematic name for inhibiting factor of prolactin release + production
- Regulated by dopamine
- Hypothalamic peptide is known to decrease prolactin production
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- PRL+, GIF
- GIF+ In the pancreas
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- PRL+
- Substance-P antagonist
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- GH, PRL+
- MSH-IH, melanostatin
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- General facilitator
- Peptide family actin on gastrin
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- PRL+, GH+, TSH+
- Paracrine action of tachykinins in HP
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- PRL+
The function of: Vasoactive intestinal peptide (VIP)
- PL+
- Somatostatin-
The function of: Angiotensin-II
- Synthesis + release of somatotropin + prolactin
- MSH-inhibiting effect
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- Stimulation of water reabsorption
- Increase BP, V1 receptor, IP3
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- Preparation of uterine contractions for estrogen response, basket cell contraction
- Classical neuroendocrine reflex
Give an example of neuroendocrine reflexes
Oxytocin-mechanisms
What are the essential characteristics of a neuroendocrine reflex?
- Translation of neural information from sensory nerve to the language of the endocrine system (using the hypothalamus)
- Effect/response is not neural but hormonal
Describe the reflexes for milk ejection
- Excitation from udder sensory fibres → Spinal cord
- Excitation → Hypothalamus
- Enhanced oxytocin synthesis evoked
- Oxytocin release increases from the neurohypophysis
- Oxytocin reaches the mammary gland via blood
- Contraction of myoepithelial cells (For milk ejection)
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Give the hormonal profile of a cow in stress
- Plasma glucocorticoid level increases, causing:
- Oxytocin fall
- Prolactin fall
- Milk ejection decrease to minimum
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What are glandotropic hormones?
Give examples
Those acting exclusively on endocrine glands
- TSH
- ACTH
- FSH
- LH
What are histiotropic hormones?
Give examples
Those acting on certain organs
- STH
- PRL
The adenohypophysis develops in which structure?
Rathke’s pouch
The adenohypophysis is formed by…tissue
Entodermal glandular
The neurohypophysis is formed by…tissue
Ectodermal nervous
Give the cell types of the hypophysis
- A = Acidophils
- B = Basophils
- C = Chromophobes
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Somatotropin (GH) producing cells
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Adrenocorticotropin (ACTH) producing cells
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Thyrotropin (TSH) producing cells
Prepubertal hypopituitarism/Removal of the pituitary gland
- Results in proportional dwarfism
- In adults:
- Smaller organs
- Thin hairs
- Decreased sexual function
- Decreased protein/glycogen stores
- Decreased BMR
Congenital hyperpituitarism
- Gigantism
- In adult life:
- Acromegaly: Increase in the size of enlargeable extremities and other parts. E.g limbs
Metabotropic hormones of the hypophysis
- GH
- ACTH
- TSH
Gonadotropic hormones of the hypophysis
- PRL
- FSH
- LH
STH/GH receptor mechanism of action
- Hormone binds to the receptor
- IC conformational change
- Activation of the second messenger system
- = G-protein activated cAMP
What direct biological effect does GH have on the body?
- Stimulates somatomedins (further hormones) in the liver
- GH is therefore considered to be glandotropic + histiotropic
Increased growth hormone secretion in young age results in…
Gigantism
Increased growth hormone secretion in adults results in…
Asymmetrical growth of:
- Limbs
- Jaw
- Certain flat bones
Give the episodic release of GH
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The effect of growth hormone on protein metabolism
- Increases amino acid uptake
- Increases intracellular protein synthesis
- Positive nitrogen balance
The effect of growth hormone on lipid metabolism
- Increases catabolic processes:
- FFA + plasma triglyceride increase
- Fatty deposits are mobilised
- Glucose oxidation decreases
- Gluconeogenesis increases
- Increased plasma acetoacetic acid levels
- Increased plasma beta-OH-butyrate levels
The effect of growth hormone on carbohydrate metabolism
- Antiinsuline effects:
- Decrease insulin-dependent glucose uptake in adipose
- Diabetogenic effects:
- Increase plasma glucose level
- Glucogenesis
- Glucagon production
- Increase plasma glucose level
- Houssay’s experiment
Houssay’s experiment
Adenohypophysectomy improved the status of a diabetic dog
GH stimulates…in the liver
- Activation of thyroid hormones
- Synthesis of somatomedins
Function of somatomedins
- Influence bone, cartilage and connective tissue
- Circulate in plasma, bound by carrier proteins
Somatomedins have a similar structure to…
Insulin
- They are therefore known as IGFs (Insulin-like growth factors)*
- They cannot exert any effect on insulin receptors*
Somatomedins are also known as…
Sulphating factors
IGF =
Somatomedins (Sm)
IGF-I
Sm-C
IGF-II =
MSA
Multiplication stimulating activity
Give the effects of IGF-I
Stimulation of:
- Chondrocyte sulphate intake
- Chondrocyte + osteoblast bone forming activity
- Longitudinal bone growth
- Transversal + periosteal bone growth
- Acromegaly
Rat tibia test
- A biological hormone identification method
- Rat epiphysis’ do not close: always ready to grow
- Unknown substance is administered
- The thickness of the tibial disk is compared with its previous normal size
Describe the regulation of GH secretion
- Plasma levels of:
- Glucose
- Arginine
- Thyroid hormone
- Hypothalamic factors
Peripheral feedback of GH regulation consists of which compounds?
- Plasma metabolites
- IGF
- IGF-BP (Binding protien)
Title the figure
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Regulation of GH secretion
Regulators of GH secretion
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- Plasma glucose + amino acid levels
- Sex
- Stress
- Age
Regulators of GH secretion
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Neurosecretion:
- GH-RH
- GH-IH
Regulators of GH secretion
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Trop. hormone:
- GH
Regulators of GH secretion
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- Metabolites of peripheral tissues + IGF levels
- GH receptors
- IGF binding proteins
Practical approaches of GH
- Increase productivity
- Milk
- Genetic engineering
- rpGH = recombinant-porcine growth hormone
Show the GH effects in cow (Graph)
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Biochemical function of ACTH
In the adrenal fasciculate + reticular zones:
- ACTH increases cAMP pathway
- Stimulating glucocorticoid synthesis
What is the primary regulator of aldosterone?
Plasma [K+]
Not ACTH
Many hormones produced in the pituitary gland are synthesised from a common precursor hormone called…
PRE-POMC
- (PRE-PROOPIOMELANOCORTIN)*
- The name is derived from the most important hormones derived from it*
List the hormones derived from Pre-POMC
- Opioid peptides
- MSH
- ACTH
Hormones derived from Pre-POMC are involved in which processes?
Adaptive processes of the body
ACTH is released in the incidence of…
Stress:
- Mobilises energy reserves
- Decreases sensation of pain
Which substance stimulates all the shown cleaving processes?
Where is this substance produced?
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CRF (Corticotropin-releasing factor)
Produced in the hypothalamus
LPH =
Lipotropic hormone
CLIP =
Corticotropin like intermediate peptide
Endorphin =
Endogenous morphine
Enkephalin=
Endogenous opioid / Signal peptide
Give the steps of ACTH production
- Pre-POMC
- POMC
- ACTH
Give the effect of ACTH in the glomerulosa layer
Increases cholesterol-pregnenolone conversion →
Increasing mineralocorticoid synthesis
Synthesis of ACTH is regulated according to the…
Classical feedback principle
Long feedback
Involvement of glucocorticoid concentration in ACTH feedback
Ultra-short feedback
The inhibiting effect of ACTH on CRF
Give the steps of neural impulses causing ACTH secretion
- Nerve impulses → Hypothalamus
- Impulses are integrated by CRF synthesising cells
- Circadian fluctuation of CRF
- Determination of ACTH release
Title the figure
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Regulation of ACTH synthesis
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Exogenous/endogenous effects
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- Serotonin
- ACh
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CRF
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ACTH
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Neurosecretion
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Tropic
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Steroids
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- Norepinephrine
- GABA
Circadian rhythm of ACTH
- Short half-life
- Conc. is higher in the early morning
- Lowest at midnight
This is the cause of the fluctuation of glucocorticoid conc. (diurnal rhythm)
Annotate the figure
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- ACTH levels increase in early morning hours
TSH
- Gonadotropic peptide hormone
- Alpha chain: Species specificity
- Beta chain: Biological specificity
What increases TSH levels
- Thyroid hormones
- Hypothalmic TRH
What decreases TSH levels?
- Cortisol
- Dopamine
- Somatostatin
Role of TSH
Stimulation of thyroxine
Plasma TSH concentration is increased by…
TRH
FSH
- Increase oestrogen synthesis in the follicle
- Maturation of the follicle
- Increased testicular spermatogenesis
FSH expression is directed by…
- GnRH
- Steroids
- Inhibin
LH
- Luteinising hormone
- Located: Leydig cell → Testis / Granulosa cell → Ovary
- Increases synthesis of androgens in both organs
- Primary factor initiating ovulation
PRL
Prolactin
- Stimulate mammary gland differentiation
- Stimulate + maintain milk production
- Metabolic hormone
How is PRL stimulated
- Hypothalamic neuronal activity
- Oestrogen inhibits dopamine synthesis
- Stimulating PRL production during ovulation
Give the effects of PRL
- Facilitation of lactogenesis
- Facilitation of galactopoiesis
- Support of suckling
- Ovulation in the rat
Describe the steps toward spontaneous inhibition of PRL
- Spontaneous production of Ca2+ signal in the hypothalamus
- Dopamine synthesis in hypothalamus changes
- Levels of dopamine alter according to a tonic pattern
- Stimulation + suppression of adenohypophyseal PRL production + release
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List the stimuli of PRL production
- Pregnancy
- Suckling
- Stress
- Sleep
- Hypoglycaemia
- Dopamine
List the inhibitors of PRL production
- Dopamine
- GABA
- GAP
- Drug: Bromocryptine
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Positive physiological stimuli and negative effects
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Serotonin opioids
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Neurosecretion + Peripheral blood-derived signals
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PRL
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Trophormone
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Udder:
- Suckling
- Maternal behaviour
Other: Increase of metabolism
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‘Tonic’ central inhibition
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- Dopamine
- GABA
- GAP
PRL regulation by neurosecretion involves which hormones?
- TRH
- GnRH
- VIP
- Galanin
PRL regulation by peripheral blood involves which hormones?
- Serotonin
- Angiotensin-II
- Oestrogens
MSH
- Formed from ACTH
- Stimulation of pigment granule production
- Transport along the microtubule system → Decoloration of cells
Effect of MSH on pigment cells
- Microtubule system from the nucleus
- MSH causes:
- Granules to migrate along microtubules
- Even distribution of granules, darkening cell
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Function of melatonin
Hormone:
- Stimulates migration of scattered pigment granules
- Back to the vicinity of the nucleus
Pineal gland produces
Produces serotonin + melatonin
Melatonin secretion
- Circadian rhythm, affected by light
- Decreased illumination acts positively
- Increased daylight acts negatively
Some species:
- Melatonin production positively influences sexual activity
- In other species, it may have a negative influence
Describe the innervation of the pineal gland
- Not directly connected to the CNS
- Innervated by postganglionic sympathetic fibres
Describe the effect of decreased light intensity on the pineal gland
- Decreased illumination to retina → Sympathetic activity
- Suprachiasmatic nucleus (SCN) connection
- Excitation from cervical ganglion → CP
- Norepinephrine released here → NAT synthesis (used in melatonin synthesis)
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Title the figure
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Innervation of the pineal gland
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Norepinephrine
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Beta-receptor + Adenylate cyclase
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AMP → cAMP
Give the steps of Melatonin production
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Give the degradation of melatonin
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How does melatonin have a counter-effect on MSH?
- It inducts concentration of pigment granules
- Skin becomes pale
Give the three effects of melatonin in mammals
- Sexual function
- Psychic effects
- Defence against free radicals
(Mammals) Influence of melatonin on the sexual cycle
- Termination of the production of:
- GnRH
- FSH
- LH
- Sheep - Initiates oestrous cycle
- Horse - Inhibits estrous cycle
Relevance to seasonality
Describe melatonin levels at different human sexual maturation stages
Melatonin inhibits sexual maturation in humans
- High in children between 1-6 years old
- Decreases later during puberty: GnRH synthesis occurs
- Decrease with age
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Melatonin levels during ovulation (Human)
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During and before ovulation, the night time peak of melatonin is…
Significantly decreased
- Inhibition of LH production decreased
- Ovulation is stimulated
Describe sexual cycle activity in the cat and horse
Increased light exposure → Increased sexual activity
- Cat: 15-minute increase of light exposure decreases melatonin
- Horse: Increased daylight cycle in February:
- Early spring estrus cycles
Describe sexual cycle activity in the sheep and goat
- A decrease of daylight:
- Oestrous activity
- Fertilisation in autumn → 5-month pregnancy → Progeny born in spring
- Melatonin is g__onado__-stimulative
Summarise photo-gonado stimulation in birds (graph)
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Psychic effects of melatonin
Maintenance of cyclic processes
Determined by:
- Day/night
- Seasonal changes
Explain jet-lag
- High diurnal melatonin
- Adaptation requires 1 day for each time zone
Seasonal emotional fluctuations
- Short diurnal periods - Irregular periods of depression
- Lethargy/sleepiness/hunger
- Assigned to melatonin overproduction
- Symptoms eliminated with physiotherapy
Effect of melatonin on free radicals
- Melatonin has a defence role against free radicals
- Thought to be the cause of melatonin’s high plasma content
Scavenger substances
Compounds suitable for binding and neutralisation of free radicals
→ Melatonin is an example
List some reactive radicals
- Superoxide O2-
- Hydrogen peroxide H2O2
- Hydroxyl OH-
HRE
- Hormone-responsive elements
- Control gene expression of:
- Metabolic enzymes
- Structural proteins
HRE presence is controlled by…
Thyroid hormone
The function of the thyroid hormone in reptiles
- Growth
- Not thermoregulation
Thyroid gland secretes…
- Thyroxine (T4)
- Triiodothyronine (T3)
- Reverse triiodothyronine (rT3)
- Calcitonin
T4 is converted to…
T3
How can thyroid hormones production be stopped
By removal of the thyroid
- Surgical removal
- Thyroid destruction by radioactive iodine
Symptoms of thyroid hormone deficiency in young animals
- Dwarfism
- Neural symptoms
- Sexual development retarded
Symptoms of thyroid hormone deficiency in adult animals
- Dermal symptoms - Myxoedema
- Neural functions
- Sexual functions
- Metabolic effects
A neural symptom of thyroid deficiency in young animals
Cretinism
- Bad grasp
- Poor learning
- Constant apathy
Dermal symptoms of adult thyroid deficiency
- Shaggy fur/Hair loss
- Subcut. CT becomes swollen
Symptoms of thyroid hormone overproduction
- Emphasised catabolic processes
- Hypoxia sensitivity increases
- Increased fat burning
- Decreased lipid + protein storage
- Decreased body weight
- Tachycardia
- Left ventricle hypertrophy
- Increased irritability
Basedow’s syndrome
- Form of hyperthyroidism
- Enlarged thyroid gland + overproduction
- Eyes protrude from their sockets (Exophthalmus)
TRH synthesis is affected by which feedback loop
Long
Production of TRH/TSH is inhibited by
- Feedback loops Long/short
- An increase of IC T3 level in hypothalamic cells
Give the exogenous effects of T4 concentration
- Photoperiod
- Feeding
- Temperature
- Stress
Give the endogenous effects of T4
- Genetic determination
- Physiological state
- Changes of hormone receptor
- Activation ability of peripheral cells
Title the figure
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General regulation of thyroid hormone
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Exogenous effects
e.g cold
Which thyroid hormones influence metabolism
T4 + T3
Title the figure
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Thyroid hormone synthesis
1
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Iodine enters gland by active pump mechanism
2
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Iodine ion → Atomic iodine
Lysosomal peroxidase enzyme
3
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Iodine → Organic bonds of thyroglobulin (TG)
- Binding to tyrosine residues of the protein
- 1 iodine = Monoiodotyrosine (MIT)
- 2 iodine = Diiodotyrosine (DIT)
Thyronines are created by condensation of MIT + DIT
MIT + DIT =
T3
DIT + DIT =
T4
4
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- Epithelial cells synthesise colloid
- TG with thyroid hormones enter the follicle by endocytosis
5
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Start of hormone release:
- Endocytosis of TG
6
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Protein molecules degraded intracellularly
- Residual iodine-containing amino acids are recycled
7
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Hormones leave on the basal side of the cells by passive diffusion
What stimulates almost every step of Thyroid hormone synthesis?
TSH
Thyroid hormones are built on a…frame
Thyronine
Formed by 2 tyrosine frames
What is needed in order to keep thyroid hormones dissolved in water?
Binding proteins
Name the binding proteins of thyroid hormones
- Thyroid-binding globulin (TBG)
- Thyroid-binding prealbumin (TBPA)
- T4
Liver thyroid hormone transit time
5 Seconds
Brain thyroid hormone transit time
1 second
90% of thyroid gland secretum is…
Inactive T4
5’ deiodinase (5’D) function
T4 → active T3
5 deiodinase (5D) function
- T4 → Inactive rT3
- T3 → Inactive T2
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Inactivation pathway
Give some deiodinases
- D1 ORD
- IRD
- D2 ORD
- D3 IRD
Type I Deiodinase function
Produce T3
Type II Deiodinase function
- Provide 5’ deiodination
- Regulatory role
Type III Deiodinase function
5 deiodination (inactivation)
BAT
Brown adipose tissue
IRD
Inner-ring deiodinase
ORD
Outer ring deiodinase
List the metabolic effects of thyroid hormone
- Thermogenesis
- Regulates the Intermediary metabolism
- Facilitates the carbohydrate metabolism
- Lipid metabolism
- Protein metabolism
How to thyroid hormones increase BMR?
- Increased number of mitochondria
- Na+/K+ ATPase activity increases
Effect of thyroid hormone on carbohydrate metabolism
- Intestinal absorption of glucose increases
- Rates of gluconeogenesis + glycogenolysis increase
- Insulin secretion increases
Effect of thyroid hormone on lipid metabolism
- Increase anabolism
- Increase mobilisation
- Increase catabolism
- FFA increases in plasma
Effect of thyroid hormone on protein metabolism
- Increase in protein synthesis + breakdown
- In the case of no hormone:
- No protein-anabolism
- In the case of overdose:
- Catabolism becomes dominant
Effect of thyroid hormone on the nervous system
- Development of myelinisation
- Widespread synaptic connectivity develops between neurons
Effect of thyroid hormone on the cardiovascular system
- Permissive effect:
- Effect of catecholamines is potentiated
- Increased cardiac function + O2 consumption
Goitre
Enlargement of the thyroid gland
- Can be accompanied by hyper- or hypothyroidism
- Developed when no hormones are secreted into the blood
- Can be caused by a lack of iodine
List the goitre inducing substances
- SCN-
- Brassica sp.
- Thiourea-derivates
- Lithium
- High iodine intake
How does SCN- cause goitre?
Inhibits iodine uptake
How does Brassica cause goitre?
Inhibitors iodine incorporation
How do thiourea derivates cause goitre?
Inhibits the reduction of ionic iodine
How does lithium cause goitre?
Inhibits release of hormones
How does a high amount of iodine cause goitre?
Inhibits hormone synthesis and secretion
Which locations do not have a lot of iodine in the diet?
Locations far from the sea
Give the processes leading to endemic goitre
- Low iodine
- Disturbed synthesis of thyroid hormones
- Synthesis of TRH + TSH
- Higher BMR of thyroid
- More iodine extracted from the blood
- The growth of the gland
Give the most important reserve of iodine in the body
The thyroid gland
5-7mg
Goitre by excessive iodine intake
Decreased hormone production
- Acts as physiological feedback inside the gland
- Inhibits unnecessarily high rates of hormone production
- Can result in sustained high TSH levels
- Thyroid grows, unable to produce hormones
Canine hypothyroidism
Symptoms + treatment
- Un-rare
- Symmetrical hair loss
- Administration of thyroid hormones
- Replacement of T4 + T3
Feline hyperthyroidism
Symptoms
- Disease of cardiac muscle (Cardiomyopathy)
- Cardiac hypertrophy develops
Adrenal cortex
- Produces steroid hormones
- Mineralocorticoids
- Glucocorticoids
- Mineral + water metabolism
- Mobilisation of energy stores
List the zones of the adrenal cortex
- z. glomerulosa(ruminants) /z. arcuata
- z. fasciculata
- z. reticularis
Which species don’t have separate zones of the adrenal medulla
Birds
Is the adrenal cortex innervated?
No
z. glomerulosa produces…
Mineralocorticoids
z. fasciculata produces
Glucocorticoids
z. reticularis produces…
- Androgens
- Estrogens
Title the figure
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Long feedback loop of ACTH on the adrenal cortex
The basis of all adrenal hormone production originates from…
Cholesterol (+de novo)
What are the three groups of adrenal cortex hormone frames?
- Pregnane (21-carbon)
- Androstane (19-carbon)
- Estrane (18 carbon)
Examples of pregnanes
- Mineralocorticoids
- Glucocorticoids
Androstane
Male sexual hormones
Enzyme 1
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20,22-demolase
Enzyme 2
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3-beta-hydroxysteroid dehydrogenase-4-5-isomerase
Enzyme 3
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17-alpha-hydroxylase
Enzyme 4
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C21 hydroxylase
Enzyme 5
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18-aldolase
Enzyme 6
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17-20 desmolase
Enzyme 7
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Aromatase
20, 22 demolase function
- Key enzyme of steroid synthesis
- Belong to P450 enzyme family
3-beta-hydroxysteroid dehydrogenase-4-5-isomerase function
- Lack of this enzyme = fatal
- Needed for mineralocorticoid + glucocorticoid synthesis
17-alpha-hydroxylase function
- Determines glucocorticoid direction
- If it is lacking:
- Overproduction of aldosterone + corticosterone
- No synthesis of:
- Glucocorticoids
- Androgens
- Estrogens
C21 hydroxylase enzyme function
- Lack of this enzyme:
- Lack of aldosterone → loss of minerals
- ACTH prevalence → synthesis of only androgens/estrogens
- May stimulate male secondary sexual attributes in females
18-aldolase function
Precondition of aldosterone synthesis
17-20-desmolase function
Determines sexual steroid direction
Aromatase enzyme function
Determines sexual hormone synthesis
Give the main mineralocorticoid hormone
Aldosterone
Overdose of mineralocortiocoids
- Na+ increase
- Water reabsorbed with Na+
- Results in isoosmotic hypervolemia
- Increased urinary excretion (renal escape)
- Decreased K+ in the body
- Muscular weakness
- Paradox alkalosis
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Water reabsorption
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|soosmotic hypervolemia
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Compensatory effect of the kidney in ‘renal escape’
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Only 10% (instead of 20%)
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- Muscular weakness
- Paralysis
- Alkalosis (Aciduria)
Title the figure
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Mineralocorticoid deficiency
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- Loss of Na+ and water
- K+ + H+ retention
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Acidosis
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Isoosmotic extracellular hypovolemia
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Hyposmotic extracellular hypovolemia (25%)
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Paradox intracellular hypervolemia
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- Decrease blood volume + BP
- A decrease of renal blood flow
- Azotemia
- Death
Give the factors regulating mineralocorticoids in order of importance
- The increase of plasma K+ conc.
- Renin-angiotensin system
- The decrease of Na+ content in the body
- ACTH
How does an increase of plasma K+ regulate mineralocorticoids?
Increases aldosterone synthesis
How does the renin-angiotensin system regulate mineralocorticoids?
- System activated
- JGA detects Na+ deficiency
- Angiotensin II synthesised
- Aldosterone synthesised
Give the most prominent glucocorticoids
- Cortisol
- Corticosterone
The physiological effect of glucocorticoids
- Long-lasting mobilisation of the energy reserves of the body
- Carbohydrate metabolism
- Protein metabolism
- Lipid metabolism
Effects of glucocorticoids on the carbohydrate metabolism
- Glyconeogenesis (GNG)
- Amino acids → Liver
- Amino acid mobilisation
- Excessive GNG → Metasteroid diabetes develops
Effect of glucocorticoids on protein metabolism
- Decrease protein synthesis
- Increase protein cleaving
- Nitrogen balance decreases
Effect of glucocorticoids on lipid metabolism
- Increase lipolysis
- Increase plasma FFA levels
- Increased extent of fat burning
- Redistribution of fat:
- Fat moves from periphery → liver
Circulatory effects of glucocorticoid insufficiency
- Na+ loss, oligemia
- K+ increase → Cardiac weakness
- Increased capillary permeability → oedema
Blood cell effects of glucocorticoid insufficiency
AC overproduction:
- A decrease of: Eosinophils + basophils
- Lymphoid tissue degrades
AC extirpation:
- Lymphoid hyperplasia
Neural effects of glucocorticoid insufficiency
- AC hyperfunction - Convulsive susceptibility increase
- AC extirpation - Depression, psychic disorders
Pharmacological effects of glucocorticoids
- Anti-inflammatory effect
Effect of continuous high level of glucocorticoids (Such as stress/ drugs)
- Inhibition of mesenchymal cell proliferation
- Antiphlogistic effect
- Antiallergic effect
Inhibition of mesenchymal cell proliferation
- Fibroblast + collagen formation is inhibited
- Cicatrisation is prolonged
- Granulation + healing of wounds is inhibited
- Osteolysis → osteoporosis
Anti-inflammatory effect of glucocorticoids
- PLA2 blocking effect
- The decrease of inflammatory colour, dolor and tumor
- Decrease basophil degranulation (decrease allergic reactions)
- Masking effect
Antiallergenic effects of glucocorticoids
- Inhibit histamine release
- No direct influence on the antigen-antibody reaction
Give the responses to stress
- Specific response
- Aspecific response
Stress is elicited by…
Stressors
List some physical stressors
- Mechanical stimuli
- Surgical intervention
- Limitation of motion
- Temperature
List some pathogenic stressors
- Virus
- Bacterium
- Parasite
List some stressors related to feeding
- Deficiencies:
- Vitamins
- Microelements
- Intoxications
Give some examples of emotional stressors
- Psychic stress
- Pain
- Lack of stimuli
1
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Initial stage
- Release of ACTH
- Often accompanied by Cannon’s alarm reaction
- Effect of catecholamines declines
- ACTH remains high
2
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Resistive stage
- High production of glucocorticoids
- Unnecessary effects reduced to a minimum
- The immune system becomes inhibited
- Storing processes inhibited
- Energy needs:
- Burning fat
- Burning protein stores
- Muscles decomposed
3
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Exhaustion stage
- Energy reserves of organism expire
- Stage of collapse
- Animal dies
4
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Adaptive disorders stage
- Arthritis
- Chronic hypertension
- Ulcer
- Hepatic failure
The adrenal medulla is part of the…nervous system
Sympathetic
The adrenal medulla produces…
Epinephrine
Which cell type is found in the adrenal medulla
Chromaffin cells
Chromaffin cells: Large, few granules indicates
Noradrenaline
Chromaffin cells: many, small granules indicates
Adrenaline
Body condition after removal of the adrenal medulla
- Activity at a general state
- Reproductive functions don’t change
- Animal reacts appropriately in case of emergency
- Blood glucose stable
- Catecholamine plasma levels show characteristic changes
The process of removal of the adrenal medulla
Demedullation (AMX)
How can demedullation be executed surgically?
By keeping the adrenal cortex intact
Lack of medulla is compensated by the sympathetic nervous system
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Epinephrine
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Norepinephrine
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Dopamine
Adrenal medullar hormones are collectively called…
Catecholamines
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Tyrosine
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DOPA
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Dopamine
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Norepinephrine
Title the figure
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Adrenaline synthesis + Peptidergic co-transmission
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Amine precursor
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H+
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DBH → NE
DBH = Dopamine-beta-hydroxylase enzyme
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H+
Via ATPase pump
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NE
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PNMT
Enzyme
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E
(Epinephrine)
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Chromogranin
Degradation of hormones allows…
Suspension of hormonal effects
Give the methods of hormone inactivation
- Reuptake
- Enzymatic cleavage
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Give the two enzymes involves in enzymatic cleavage of hormones
- MAO (Monoamine oxidase)
- COMT (Catecholamine-O-methyltransferase)
Catecholamines exert their effects through…and…receptors
- Alpha
- Beta
Hormonal actions are divided into…
- Effects on circulation
- Effects on particular organs
Norepinephrine stimulates…receptors
- Alpha 1
- Beta 1
Epinephrine stimulates…receptors
- Alpha 1
- Beta 2
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- Agonist: Phenylephrine
- Antagonist: Phenoxybenzamine
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- Agonist: Phenylephrine
- Antagonist: Prazosin
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- Agonist: Clonidine
- Antagonist: Yohimbine
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- Agonist: Isoproterenol
- Antagonist: Propranolol
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- Agonist: Prenalterol
- Antagonist: Methoprolol
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- Agonist: Metaproterenol
- Antagonist: Butoxamine
Catecholamine receptors exert their effects mostly by…
G-protein dependent cAMP system
Title the figure
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Alpha receptor signaling
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ATP → cAMP
AC
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Inactive PK
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Active PK
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DAG
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Active PK-C
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IP3
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Ca2+
Title the figure
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Beta receptor signaling
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ATP
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cAMP
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Active PK
Alpha-1 receptor effects
- Smooth muscle contraction
- Glycogenolysis
- Sympathetic synaptic transduction
Alpha-2 receptor effects
Regulation of transmitter release in the CNS
Beta-1 receptor effects
- Stimulation of the heart
- Stimulation of adipose cells
Beta-2 receptor effects
- Smooth muscle relaxation
- Increase metabolism
Where do catecholamines effect?
- Circulation
- Smooth muscles
- Intermediary metabolism
- Different organs
Effects of catecholamines on circulation
- Similar to sympathetic nervous system effects
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Norepinephrine (NE) > Epinephrine (E)
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Smooth muscles
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Smooth muscle contraction
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Isoproterenol > E > NE
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Cardiac, coronary
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Enhancing, dilation
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Epinephrine
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- Bronchi
- Smooth muscles of skeletal muscle vessels
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Dilation
The receptor-type used is dependent on…
Plasma concentration
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- α1: Vasoconstriction
- β1: Increase of cardiac output
- Σ: Increase of blood pressure
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- β1: Increase of cardiac output
- β2: Vasodilation in skeletal muscles
- Σ: Redistribution of circulation
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- Differences are observed
- Σ: redistribution of circulation, increase of blood pressure
β1: Increase in cardiac output: Positive effects
- Chronotrop
- Inotrop
- Dromotrop
- Bathmotrop
Receptors in the arteriole wall in intestinal tract
- Too many alpha receptors
- Very few beta receptors
Receptors in the arteriole wall in skeletal muscle
- Too many beta 2 receptors
- Very few alpha receptors
Receptors in the smooth muscle internal to the intestinal tract
- Many alpha receptors
- Many beta2 receptors
Describe the hormonal sympathetic activation of smooth muscles
Blood distribution
- Low epinephrine → Beta effect dominates
- Vessels of skeletal muscles dilate (Beta 2 effect)
- Vasoconstriction in areas of low beta receptors (Alpha 1 effect)
- Blood translocated to muscles from intestines
- Intestinal tract relaxes (Beta2 effect)
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Effect on the smooth muscle of high epinephrine
- Alpha effect becomes dominant
- Vessels contract all over the body (Alpha 1 effect)
- Cardiac output increases
- BP increases
- Beta2 + Alpha1 effects reach equilibrium - lumen doesn’t change
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Effect on the smooth muscle of high norepinephrine
Similar to epinephrine
- Norepinephrine has very low Beta 2 effects
- Contraction of smooth muscle internal to intestines is stronger
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Effects of catecholamines on the intermediary metabolism
- Increase BMR
- Increase O2 consumption
- Cardiac output increases
- Respiration increases
- The calorigenic effect is significant + rapid
Effects of catecholamines on the carbohydrate metabolism
- Liver glycogen utilisation increase
- Plasma glucose level increase
- Glucose uptake in the muscle increases
- Glycolysis → Lactic acid synthesis increases
- Cori-cycle → Carbohydrate stores shifted from periphery to the centre
Effects of catecholamines on the lipid metabolism
- The utilisation of fat increases
- FFA levels increase
- Beta receptor effects dominate in adipose tissue
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- Glycogenolysis
- Lipolysis
- Glyconeogenesis
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Lipolysis
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Glycogenolysis
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- β2: Insulin secretion increases
- α2: Insulin secretion decreases
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- β1: Increase contractility, condition, frequency
- α1: vasoconstriction
- β2: Vasodilation
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Dilation
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- α1 : M. radialis contraction
- β2: M. ciliaris relaxation
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Increase of renin secretion
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- α1: Contraction
- β2: Relaxation
Alarm reaction
- ‘Fight or flight’
- Body enabled for rapid utilisation of a high amount of energy
- Enhancement of efficiency of physical abilities
Give the effects of the alarm reaction
- Pupils dilate
- CO increases
- Dilation of blood vessels
- Contraction of spleen
- O2 + Heat production increases
- Inhibited GI + glandular function
- Plasma glucose level increases
What regulates the adrenal cortex?
- Sympathetic nervous system
- Hypoglycemia
- Alarm reaction
- Receptor-regulation
Hypoglycaemia regulation of adrenal cortex
Direct stimulus
Alarm reaction regulation of adrenal cortex
Organism able to focus on releasing energy by secretion of catecholamines
Receptor-regulation of the adrenal cortex
Complex regulation: Up and down regulation
Summarise epinephrine effects
- Hormone of fighting
- Produced by the effects of:
- Muscle activity
- Cold
- Drop of blood pressure
Summarise norepinephrine effects
- Aggressive behaviour
- Produced by the effects of:
- Hypoxia
- Pain
- Emotional anxiety
Give the main hormones of the pancreas
- Insulin
- Glucagon
Pancreas acts as what kind of gland
- Endocrine
- Exocrine
Insulin is produced by which cells?
B cells / Beta cells
Isletas of Langerhans are composed of which cells?
- B cells
- D cells
- A cells
- F cells
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B-cells
- Insulin production
- Synthesised as pre-pro-insulin
- Role: Stimulation of anabolic + storage processes
Insulin is made up of
- A chain
- B chain
- Zinc
A-cells
- Glucagon production
- Acts only in the liver
- Roles:
- Increase plasma glucose
- Decrease glycogen synthesis
- Stimulate GNG
D-cells
- Somatostatin production
- Roles:
- Inhibition of insulin + glucagon overproduction
- Inhibit A + B cell activity
- Inhibition of every phase of digestion
- Motility decrease
- Secretion decrease
- Inhibition of insulin + glucagon overproduction
F-cells
- Pancreatic polypeptide (PP) production
- Roles:
- Biliary secretion + secretion of pancreatic enzymes
- Gastric secretion + motility increase
Protein intake enhances its secretion
Which mechanisms regulate hormone synthesis of islets of Langerhans?
- The regulatory system based on paracrine activity
- Glucose + amino acid levels of the plasma
- Neural regulatory effects
Give the steps of regulation of islets of Langerhans by paracrine activity
- B-cells exert reduce glucagon synthesis + A-cell activity
- Glucagon stimulates insulin secretion, the glucose level is limited (prevented from being lost in the urine)
- Glucagon stimulates somatostatin
- Somatostatin has a negative effect on A- and B-cells
Describe the regulation of plasma glucose
- High plasma glucose stimulates insulin secretion
- Low plasma glucose stimulates glucagon secretion
- Glucagon stimulates insulin synthesis of B-cells
- Plays role in ‘feed-forward’ mechanism
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Without GIP + enteroglucagon…
Glucose loss
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In the presence of GIP + enteroglucagon
Glucose saving
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Give the two-stage process of insulin release
- Stored insulin is released
- Newly synthesised insulin released
In the case of food consumption with high glucose content…
B-cells informed about the energy sources before the increase of plasma glucose level
In the case of food consumption with high carbohydrate content…
GIP + Enteroglucagon are liberated
- This causes the secretion of insulin in advance (‘feed forward’)
Title the figure
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Stimulation of B cells
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AC
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ATP → cAMP
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GLUT2
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- ATP increase: K+ channel closes → Depolarisation
- Glucose-6-P → Insulin synthesis, late release
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Immediate release
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De novo synthesis
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Insulin
Title the figure
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Neural effects on the B- and A-cell
Autonomic nervous system affect insulin production via…
- Sympathetic: Alpha and beta receptors
- Parasympathetic: Acetylcholine receptors
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Blocking of insulin release via the sympathetic system
- Blocking through alpha-2 receptors
- Insurance of high plasma glucose levels
- Blocking of insulin release
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Alpha2: Insulin glucagon block
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N. vagus: Insulin glucagon transient release
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Beta2: Insulin glucagon transient release
Glucose gets through the membrane via…
GLUT transporters
Insulin dependent tissues
In some tissues glucose tranpsorters are regulated by…
Insulin
How many subtypes of GLUT transporters are there?
7
GLUT-1 transporter
- Affinity
- Location
- Intermediate affinity
- In several tissues
GLUT-2 transporter
- Affinity
- Location
- Low affinity
- Pancreas cells
GLUT-3 transporter
- Affinity
- Location
- High affinity
- Neurons
GLUT-4 transporter
- Affinity
- Location
- High affinity
- Muscle, adipose tissue
GLUT-5 transporter
- Location
- Intestines, testis
Describe insulin-receptor interaction
- Two insulin molecules bind to these subunits
- Conformational change in the (IC) beta subunit
- IC protein kinase enzymes activated
The effects of insulin can be divided into which groups?
- Glucose uptake
- Metabolic effects
Effect of insulin on metabolic processes
Increases storing and anabolic processes
List the insulin-_independent_ tissues
- Brain cells
- RBC/WBC
- Brain capillaries
- Liver
- Uptake in muscle + adipose
List the insulin-_dependent_ tissues
- Muscle
- Adipose tissue
Insulin-independent tissues
Tissues metabolising glucose that can only take up glucose without the presence of insulin
Which GLUT receptor is found in the islets of Langerhans?
GLUT2
Insulin increases the synthesis of…
- Glycogen
- Protein
- Fat
By inhibiting their respective enzymes
The effects of insulin on carbohydrate metabolism
- Incorporates amino acids into proteins: GNG
- Decrease glucose level
The effects of insulin on lipid metabolism
- Triglyceride synthesis increase
- Degradation of lipid decrease
- Stimulate fatty acid synthesis from AcCoA
The effects of insulin on protein metabolism
- Stimulate amino acid uptake of all cells øhepatocytes
- Enhance protein synthesis
- The decrease in protein degradation
- Positive nitrogen balance
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Amino acid
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Glucose
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FFA
Every action of insulin is antagonised by…
Glucagon
However, only in the liver
Effect of insulin on: Dependent tissues
Facilitates glucose entry
Effect of insulin on: Adipocytes
- Glucose entry increases
- Triglyceride synthesis increases
- Lipase activity decreases
Effect of insulin on: Muscle cell
- Glucose entry + storing increases
- Glucose → energy conversion increases
- Amino acid entry, protein synthesis increases
Effect of insulin on: Liver
- Glucose entry not regulated
- Glycogen synthesis increases
- Glucose release decreases
- Ketogenesis and GNG decreases
Effect of insulin on: Neuron
- Enhances K+ entry
- Hyperpolarisation effects
Title the figure
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Glucose metabolism
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Foodstuff glucose
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Plasma glucose
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Lactic Acid
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- H2O
- CO2
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Adipocyte
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FFA
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Liver glucose
During glucose metabolism, if there are too high AcCoA concentrations…
Ketone bodies appear
- Citric acid cycle activity decreases
What are the two outcomes of insulin deficiency on protein metabolism?
- Dehydration
- Negative N balance
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Utilisation of glucose decreases
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Protein catabolism
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K+ loss
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Tissue K+ decreases
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Polyuria + polydypsia
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Amino acid levels decrease
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GNG increases
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Urinary N-secretion increases
What are the two outcomes of insulin deficiency on fat metabolism?
- Na+ loss
- Acidosis
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Glucose utilisation decreases
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Lipogenesis (storage) decreases
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Mobilisation of adipose deposits increase: Lipemia
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Production of ketone substances in the liver: Ketonemia
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Ketonuria
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Utilisation of glucose decreases
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- Liver glycogenolysis
- Muscle glycogenolysis
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Hyperglycemia
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- Glycosuria (Excess sugar in urine)
- Osmotic diuresis (Increased urine production)
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H2O + electrolyte loss
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- Dehydration
- Hemoconcentration
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Breakdown of circulation
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Production of ketone substances increases
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- Vomiting
- Diarrhoea
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- Na+ loss
- K+ loss
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- Fall of blood pressure
- RBF decrease
- Anuria (Failure of urine production)
- Coma
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Exitus
Parallel to metabolic acidosis, what else occurs?
Protein degredation
List the types of diabetes
- Type-1 (Human)
- Type-2 (Human)
- Type-3 (Canine)
Type-1 diabetes
- Appears in juvenile age
- Effects of the disease are through insulin deficiency
- Excess of glucagon
- Rapid
- Hereditary
- Insulin-dependent diabetes mellitus (IDDM)
IDDB
- Insulin-dependent diabetes mellitus
- Caused by insufficient insulin production
Type-II diabetes
- Adults/elderly
- The insufficient response of B-cells to carbohydrates
- Though that GLUT2 isn’t functioning properly
- Insulin production still regulated
- Can be normalised with a controlled diet
- Non-insulin-dependent diabetes mellitus (NIDDM)
Type-III diabetes
- Adults, 5-15 years
- Insulin-sensitive
- Late-onset, nutritive
What are autacoids?
- Biological factors which act as local hormones
- Brief duration
- Act near the site of synthesis
What are the two groups of Autacoid?
- Peptides
- Eicosanoids (Fatty acid-like substances)
Where are eicosanoids produced?
All cells in the body
Characteristics of Eicosanoids
- 20-carbon fatty acids
- The product of enzymatic reactions of phospholipids
- Mediated by G-protein → Activating PLA2 enzyme
Title the figure
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Eicosanoid synthesis
MPL stands for…
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Membrane phospholipids
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Phospholipase-A2
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Lipoxygenase
List the effects of eicosanoids of veterinary importance
- Increase inflammation
- Insulin release
- Bone resorption
- Reproduction
- Thrombocyte aggregation
- Renal effects
Effect of eicosanoids on inflammation
- Initiate inflammation
- Example: Through PMN cells
- Cause:
- Vasodilation
- Chemotaxis
- IL-1 fever
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Effect of eicosanoids on insulin release
- HPETE stimulates PGE2 pathway
- Inhibition of insulin release
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Effect of eicosanoids on bone resorption
- PGE2 produced by osteoblast cellular membrane
- Parathyroid hormone-like effect on Ca2+ mobilisation
- Allows Ca2+ entry into the plasma
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Effect of eicosanoids on reproduction
- In large animals
- PGF2-alpha production of the uterus
- The twisted part of a. ovarica + v. uterina allows diffusion of PGF2-alpha
- Leutolytic effect
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Effect of eicosanoids on thrombocyte aggregation
- Endothelial cells release PGI continuously
- This binds to membrane receptors of platelets
- cAMP increase in platelets
- Inhibited activity of PLA2
- Platelets don’t aggregate
During injury
- This mechanism is stopped
- TXA2 synthesis begins → Aggregation + thrombus
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Effect of eicosanoids on the kidney
- Prostacyclin synthesis in renal tubule enhances renin secretion
- Increase RPF
- Antagonises effect of ADH
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Regulation of eicosanoid production
- Corticosteroids + mepacrine inhibit eicosanoid synthesis
- Salicylic acid, indomethacin and ibuprofen inhibit cyclooxygenase enzyme
- Benzydamine and imidazole inhibit thromboxane synthase enzyme
- Normal production of prostaglandins
- Decreased synthesis of thromboxane
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Peptide autacoids are part of which system?
Diffuse Neuro-endocrine system (DNES)
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- K + PNE Cells
- BLP, SN, Enkephalin
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- C-cell
- CT
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- G-cell + D-cell
- Gastrin, enkephalin
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- Brush cells
- Secretin, SP, SK, glucagon, gastrin, CCK
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- A, B, D, G, PP
- Glucagon, insulin, SN, gastrin
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- Chromaffin
- NPY, enkephalin, endorphin, BLP
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- Merkel
- CT, BLP, VIP
Abbreviation: BLP
Bombesin-like peptide
Abbreviation: CCK
Cholecystokinin
Abbreviation: CRH
Corticotropin-releasing hormone
Abbreviation: CT
Calcitonin
Abbreviation: NPY
Neuropeptide Y
Abbreviation: NT
Neurotensin
Abbreviation: PP
Pancreatic polypeptide
Abbreviation: PYY
Peptide YY
Abbreviation: SK
Substance K
Abbreviation: SN
Somatostatin
Abbreviation: SP
Substance P
Abbreviation: VIP
Vasoactive intestinal peptide
List the classifications of peptide hormones
- Bombesin
- Kinins
- Somatostatin
- Neurotensin
- Endogen opioid
- Tachykinin
Bombesin peptides
- GRP
- Neuromedins
- Ranatensins
Kinin peptides
- Kininogens
- Bradykinin
- Kallikreins
Neurotensin peptides
- Angiotensin
- Xenopsin
Endogen opioids
- Enkephalin
- Dynorphins
- Exorphins
Tachykinin hormones
- Substance-P
- Neurokinin A, B, K
- VIP
Major effects of bobmesins
- Hypothermia
- Hypoglycemia
- Gastric juice secretion
Major effects of kinins
- Vasodilation
- PH-synthesis
Major effects of somatostatins
- Hyperkinesis
- Excitation
- Periphery:
- All metabolic processes are blocked
Major effects of neurotensins
- Most potent analgesic
- Opioid independent
Major effects of endogen opioids
- CNS:
- Analgesic
- GI tract
- Synchronisation of motility
Major effects of tachykinins
- Control of exocrine pancreas
- Modulates AC steroid secretion