BIOM PART TWO - Lecture 1 Flashcards
Who was Claude Bernard?
The father of modern physiology
What did Claude Bernard suggest?
Our internal environment remains remarkably constant despite changes in the external milieu
(provides stable conditions for cells in the body)
What did Walter Cannon suggest?
Coined the term “homeostasis” to describe the relative stability of the internal environment
What is the general process of homeostasis?
Sensor –> Integration/Control Center —> Effector
What does a sensor do?
Detect shift in physiological variable outside normal range
What does integration/control centre do?
Sets normal range
What does an effector do?
Return to normal
What direction is Homeostasis going in?
A negative direction (constant negative feedback loops)
What does Homeostatic control rely on?
Sensor: constantly monitors
Integrating Centre: coordinates
Response System: changes
What do most systems operate in?
A negative feedback manner
What are some major regulatory systems?
- Skin
- Cardiovascular
- Renal
- Digestive
- Respiratory
- Musclo-Skeletal
What are some regulated factors?
Water, pH, Oxygen, CO2, temperature
What is Regulation?
Homeostasis and Maintenance of Metabolic Processes
What is Homeostasis maintained by?
The endocrine system
What is Diabetes an example of?
Defined by a loss of homeostasis
What are examples of endocrine disorders?
Diabetes mellitus: 6th leading cause of death
Thyroid Diseases
Endocrine Ovarian Disorders
What is Hyper Function?
Too much hormone
What is Hypo function?
To little hormone
What is Resistance?
Too little effect
What does hormone mean?
To excite or arouse
What is endocrine gland?
A tissue which releases a substance into the bloodstream; this substance then travels via the blood to influence a target cell
What was significant about the Classic Minkowski experiment?
The discovery of insulin
What was the Classic Minkowski Experiment?
1.) Surgically remove pancreas in dog –> The dog developed symptoms of diabetes (excessive urine, thirst)
2.) Implanted a piece of pancreas under the skin –> prevented symptoms if diabetes (reversed effect)
*Noted that the pancreas has an important effect
What did Banting and Best similarity discover?
Insulin
What did Banting and Best do?
1.) Identified anti-diabetic substance in pancreatic extracts
2.) Injecting extracts prevents symptoms of diabetes (i.e, elevated blood glucose)
What is Insulin?
Peptide hormone produced by beta cells of the pancreas
What does Insulin promote?
Absorption of glucose from blood to skeletal muscle and fat tissue
What is the inactive form of Insulin?
Hexamer, Zinc Ion, and Histidine Residues
What is the active form of Insulin?
Monomer
What makes a chemical a hormone?
1.) Proteins and Polypeptides (<100 amino acids)
2.) Steroids (cholesterol derivatives)
3.) Glycoproteins
4.) Amines (catecholamines or thyroid)
What are the level of effects?
Autocrine
Paracrine
Endocrine
What is Autocrine?
Acts on itself
What is Paracrine?
Acting on a cell nearby
What is Endocrine?
Go through blood in order to release target
What do hormones bind to?
Receptors in target cells
What do receptors have a high speciality for?
A particular hormone (non specific binding can occur - eg, hormone overspill)
What is there a continuous turn-over of?
The receptor hormone complex (essential for any signalling system)
Where are receptors for most hormones (peptide) found?
In the plasma membrane of target cells
Where are receptors for steroid and thyroid hormones found?
Inside the target cell
What do Catecholamines and peptide hormones bind to?
The extracellular domain of the receptor and activates one or more cytoplasmic signalling pathway
What do cytoplasmic signalling pathways involve?
Phosphorylation and Enzyme Activation
What do some of these pathways lead to
DNA/mRNA/proein pathway response; others have local effect in target cell
What are the steps of the Adenylate Cyclase pathway?
- Hormone and Receptor, G proteins dissociate
- a-subunit activates AC
- Catalyzes product of cAMP
- Removes regulatory unit from PK
- PK activates other molecules (hormonal response)
What are the steps of the Epinephrine and Adenylate Cyclase?
- Epinephrine binds to B-adrenergic receptor on liver cells
- G proteins activated - subunit carrying GDP dissociates, GDP –> GTP
- Subunit catalyzes adenyl cyclase which catalyzes ATP –> cAMP
- cAMP activates PKA which activates phosphorylase
- Phsophorylase converts glycogen to glucose-6-phosphate
- Glucose-6-phosphate –> glucose (released from liver)
Who were Robert Lefkowitz and Brian Kabila?
Won the 2012 Nobel prize in chemistry
What did Robert and Brian determine?
How the billions of cells in our body sense their environments
What type of receptor did they focus on?
G protein coupled receptors
Why is understanding how these proteins work important?
It has been crucial to unravelling the complex network of signalling between cells
What are the steps of the Phospholipase C-Ca2+ pathway?
- Hormone + receptor, G protein dissociate
- Activates PLC
- Causes breakdown of membrane phospholipid to IP3
- IP3 binds to ER
- Release of stored Ca2+ into cytoplasm
- Ca2+ activates other molecules (hormonal responses)
What do alpha-adrenergic receptors do?
Activate phospholipase C (via Gq)
What do beta adrenergic receptors activate?
Adenyl Cyclase (via Gs)
What do G subunits fall into?
Several sub types: G(s) alpha, G(a) alpha, etc.
What is the pathway of steroid hormone receptors?
- Steroid Hormones (e.g, estrogen, androgen,) transported bound to carrier protein (lipophilic)
- Steroid Hormone binds cell cytoplasm receptor
- Translocates to the nucleus, binds to DNA (acts as a txn factor)
- Stimulates gene transcription
- Protein products
- Response
What are the mechanisms of Thyroid Receptors?
- Thyroxine (T4) and Carrier Binding Protein
2.) T4 —> T3
3.) T3 uses binding proteins to enter nucleus
- Hormone-receptor complex binds DNA
- New mRNA
- Protein
- Response
