TP8 Endocrine System Flashcards
Describe the functions of the endocrine system
- Regulation of internal physiology
- Co-ordinates embryonic development
- Balance levels of minerals and nutrients to match demands
- Stimulated growth of metabolism
Describe hormones
- Chemical messengers
- Work slow and overtime
- travel via cardiovascular system to tissues/organs
List and describe the two types of cell communication
- Direct signalling: cells connected by gap junctions
- Indirect signalling: chemical messenger released - messenger binds with target cell
List the six different functional classifications of chemical messengers
- Paracrines
- Autocrines
- Cytokines
- Neurotransmitters
- Hormones
- Neurohormones
Describe paracrines (3 pts)
- Made locally and act on a few adjacent cells in the same tissues or organs
- Transmitted via extracellular fluid
- Growth factors - transferred from cell to cell within a single tissue
Describe Autocrines (2pts)
- Hormones produced and exerted effects on same cell
- Secretory and target cells same
Describe cytokines (2 pts)
- Referred to as immunohormones
- Produced by non-gland cells
Describe hormones (4 pts)
- Secreted from specialised endocrine glands
- Transported via circulatory system
- Long distances
- Can be transported as either free hormones, or bound to carrier proteins
Describe neurohormones (5 pts)
- Secreted by neurosecretory cells
- Secreting cell responds to an electrical signal
- Release neurohormones into the blood
- Travel to the target cells
- Different from ‘normal’ neurons - over a short distance
What does chemical structure determine?
Hydrophobic and hydrophilic - influences mechanisms of synthesis, storage, transport, release and signal transductions
List five chemical classifications of messengers
- Steroids
- Eicosanoids
- Amino acid derivatives
- Proteins and peptides
- Amino acids
Describe steroids (4 pts)
- Derived from lipids
- Synthesised on demand
- Long distance transport, bound to carrier proteins
- Hydrophobic
Describe Eicosanoids (5 pts)
- Derived from lipids
- Hydrophobic
- Synthesised via membrane phospholipids
- Synthesised on demand, released immediately
- Involved in inflammation
Describe amino acid derivatives
- Derived from amino acids
- Synthesised in cytosol
- Most are hydrophilic
Describe proteins and peptides (3 pts)
- Derived from glycoproteins, short polypeptides and small proteins
- Bind to transmembrane receptors
- Hydrophilic
Describe Amino acids
- 4x amino acids = chemical messengers
- A-glutamate
- Aspartate
- Glycine
- GABA
- Neurotransmitters in CNS
- Transported in vesicles
- Released by exocytosis
Describe the influencers in magnitude of response
- Messenger concentration
- Number receptors
- Affinity of receptors
Describe Agonist
Ligand bind to receptor = response
Describe Antagonist
Ligand bind to receptor = no response
List and describe the four types of receptors
- Intracellular: bind to hydrophobic ligands
- Ligand- gated ion channels: lead to changes in membrane potential
- Receptor enzymes: lead to changes in intracellular enzyme activity
- G-protein-coupled: activation of membrane bound G-proteins = change in cell activity
Describe G-protein-coupled receptors
- Extracellular chemical messenger binds
- Results in production of second messenger
- Second messenger continues signal transduction intracellularly
Describe primary endocrine organs
- Act to secrete hormones
- Anterior pituitary, thyroid, parathyroid, adrenals
Describe secondary endocrine organs
- Hormone secretion is secondary action
- Heart, liver, pancreas, stomach, small intestine, skin, kidneys
Describe the function of the anterior pituitary
Glandular
Describe the function of the posterior pituitary
Neural
Describe communication between hypothalamus and A. pituitary
Via Hypothalamic-pituitary portal system
Describe the posterior pituitary gland
- Paraventricular and supraoptic nuclei both have vasopressin and oxytocin producing neurons
- Hormones synthesised in the hypothalamus
- Stored in posterior pituitary
- Released into systemic circulation on demand
List the factors that influence hormone secretion
- Level of hormone in the blood
- Feedback regulation
- Hormone interactions
Describe feedback regulation
- Provide communication between:
- cells and tissues (sensors)
- integrating centers
- target tissues (effectors)
- Allow homeostasis to be maintained!
Describe negative feedback
- Moderates response
- Feeds back to decrease its own production
- Promotes homeostasis
Describe positive feedback
- Amplifies response
- Feeds back to increase its own production
- Pushes system away from homeostasis
Describe synergestic effect
Effects of hormones additive, combined effect greater than the individual
Describe permissive effect
- One hormone needed for another to produce an effect
Describe integrative/additive effects
- Hormones cause the same in target cell
- Hormones don’t use same signal pathway
- Response of target cell combinations of these hormones is additive
List the influences of hormones
- Morphological changes
- Accelerate cell division/alter gene expression
- Protein synthesis
- Stimulation of smooth muscle contraction
- Affect exocrine secretions
- Control endocrine secretions
- Regulate ion and water movement
- Affect behaviour
Describe factors that increase blood glucose
- Glucose absorption from digestive tract
- Hepatic glucose production:
- Through glycogenolysis of stored glycogen
- Through gluconeogenesis
Describe factors that decrease blood glucose
- Transport of glucose into cells:
- For utilisation for energy production
- For storage
- as glycogen through glycogenesis
- as triglycerides - Urinary excretion of glucose abnormally
Describe the environment when fed
Increased:
- glucose oxidation
- glycogen synthesis
- fat synthesis
- protein synthesis
Describe the environment when fasted
Increased:
- glycogenolysis
- gluconeogenesis
- ketogenesis
Describe the structure of the Adrenal gland
- Small paired gland sitting on top of each kidney
- Outer layer: cortex (80%)
- Inner layer: medulla (20%)
What does the adrenal gland produce
- Lipid soluble hormones derived from cholesterol
- Amine derivatives of tyrosine
Describe the cortical steroid hormones ‘Glucocorticoids’
- Primarily cortisol and corticosterone, which regulate an animals response to stress
- Lipophilic
- Rate of secretion = rate of synthesis
- Poorly soluble in blood
- Effects generally catabolic
Describe the effects of cortisol secretion on adipose tissue
Lipolysis increases
Describe the effects of cortisol secretion on muscle and other tissue
- Protein breakdown increases
- Protein synthesis decreases
Describe the effects of cortisol secretion on liver
Gluconeogenesis increases
Describe the cortical steroid hormones ‘Mineralocorticoids’
- Primarily aldosterone
- Regulates sodium reabsorption and potassium secretion
- If there ISN’T sufficient mineralocorticoids
- K+ extracellular fluid and blood increases
- Na+ and Cl- decreases
- Total vol extracellular fluid and blood
decreases
- Mineralocorticoids play key role in increasing extracellular fluid vol by increasing Na+ reabsorption
What does the adrenal medulla produce
Catecholamines
Describe the structure of Catecholamines
80% adrenaline and 20% noradrenaline and less than 1% dopamine
Describe the function of Catecholamines
- Response for the immediate fight or flight response
- Increase HR, BP, cardiac contractility
- Dilation of pupils, airways, blood vessels in
skeletal muscles - Increase cellular O2 consumption
- Increase lipolysis, gluconeogenesis,
glycogenolysis
What do follicular cells produce?
- Tetraiodothyronine (T4)
- Triiodothyronine (T3)
Describe the thyroid
Functional unit: colloid (unique)
Parafollicular ‘C’ cells - calcitonin
Chief constituent of colloid is thyroglobulin Tg
Describe the effects of thyroid hormones (6 pts)
- Increase BMR
- Decreases body weight
- Increases cardiac output
- Increases rate and depth of respiration
- Influences skin and hair growth
- Important for metamorphosis in amphibians
Describe the structure of the parathyroid gland
- Two paired smaller structures which sit on the posterior/dorsal aspect of the thyroid gland
- Secrete parathyroid hormone (PTH) which is an important regulator of blood calcium levels
