Week 22 Flashcards
What are the two pituitary hormone functional groups?
- Directly act in non-endocrine tissues- Growth hormone, prolactin, ADH, vasopressin, oxytocin, melanocyte stimulating hormone (MSH)
- Modulate secretory activity of other endocrine glands (trophic hormones) - Thyroid stimulating hormone (TSH), Adrenocorticotrophic hormone (ACTH), FSH, Luteinising hormone (LH)
What are the glands that are pituitary dependant?
Thyroid
Adrenal cortex
Gonads
What is energy homeostasis?
Maintenance of food intake against energy expenditure.
What is energy intake described as and what can influence this?
What we eat:
1. Socio economic 2. Genetic 3. Cultural 4. Psychological factors
What is the definition for energy expenditure?
Sum of internal heat and external work
What is classified as internal heat?
- Basal Metabolic Rate (BMR) - minimal energy expenditure at rest to maintain life
- Thermic effect of food - energy investments in digestion and absorption of nutrients
What happens in positive energy balance?
Energy intake higher than expenditure leads to weight gain
What happens in negative energy balance?
Energy intake lower than expenditure leads to weight loss
What are the general components of an average daily intake?
Protein, fat, carbohydrates, simple sugars, sodium, dietary fibre.
What are the main controllers for appetite regulation?
- GIT
- Key hormones
- CNS
What is the main effector organ for appetite?
Hypothalamus
What are the main GIT sensors involved in appetite regulation?
- Ghrelin
- Cholecystokinin (CCK)
- Peptide YY and pancreatic polypeptide
How does Ghrelin regulate appetite?
- It acts on the hypothalamus to increase hunger (increase food intake)
- Also increases gastric acid secretion and GIT motility.
Where and when is Ghrelin released?
Produced by the stomach when it is empty, production stops when stretch receptors are activated. (increases food intake)
How does Cholecystokinin (CCK) regulate appetite?
- Acts on hypothalamus to inhibit food intake
2. Also stimulates pancreatic/gall bladder secretion and GIT motility.
Where and when is Cholecystokinin (CCK) released?
Released from the GIT postprandially (post meal) (inhibits food intake)
Where and when is Peptide YY released?
Released by the distal intestine in proportion to the amount of calories ingested (inhibits food intake)
Where and when is pancreatic polypeptide released?
Released by the pancreas in the same way as peptide YY.
What is the effect of peptide YY and pancreatic polypeptide release?
Suppressed food intake
What are some other tissue sensors outside the GIT that regulate appetite?
Insulin
Leptin
How does exercise and physical activity regulate appetite?
- Increase in BMR (basal metabolic rate)
- Increased muscle mass (muscle has a higher resting metabolic rate)
The increase in BMR increases need for intake
- Increased muscle mass (muscle has a higher resting metabolic rate)
How is insulin related to adipose tissue?
Circulates in proportion to fat mass.
How does insulin regulate appetite?
It circulates the blood at levels equivalent to fat mass and suppresses appetite
What is the main adipokinin produced by adipose tissue?
Leptin
How is circulating leptin related to fat mass?
Circulating levels proportional to fat mass.
How does Leptin regulate appetite?
When levels are high the hunger response in inhibited
How is leptin believed to be related to obesity?
A decreased sensitivity in leptin leads to inability to detect satiety (increases risk of obesity)
What is satiety?
Feeling of being full after a meal
What is the hypophyseal portal system?
The link between the hypothalamus and the pituitary gland which allows rapid hormonal communication between the two structures
What organs receive the drug first after first part metabolism?
Well perfused ones - liver, kidney, brain
What is volume of distribution (Vd)?
It is the amount of drug in the body/ concentration
Used to represent the extent of drug distribution to tissues and not plasma.
What drugs would have a low Vd?
Drugs retained in the vascular compartment (eg warfarin)
What drugs would have a high Vd?
Drugs that are highly distributed into adipose and other non vascular compartments.
How does the plasma concentration of a drug change post IV administration?
- Initially falls sharply with time (Distribution phase)
2. Then decreases more slowly as drug has been distributed (elimination phase)
What barriers are in the blood brain barrier?
- There is tight junctions between endothelial cells
- There is also a lot of efflux transporters to pump xenobiotics such as drugs out of the brain- meaning they may not reach therapeutic levels in the brain.
What do the tight junctions of the blood brain barrier achieve?
Prevents diffusion through these spaces
What molecules can get through the blood brain barrier?
- Small non polar molecules may move across lipid membrane by passive diffusion (lipophilic)
- Large and/or polar drugs need to be transported actively or they are excluded
How does the placenta interact with medications?
- Generally does not exclude drugs
- Exposed to drugs to some extent
- Does have p-glycoprotein efflux pumps to limit exposure to potentially toxic agents.