- a hormone produced by the adipose tissue that appeared to provide negative feedback.
- Leptin is a peptide hormone that affects homeostasis and immune responses.
- Lowering food intake can lower leptin levels in the body, while increasing the intake of food can raise leptin levels.
main regulatory organ of appetite and effectors
- The hypothalamus, a part of the brain, is the main regulatory organ for the human appetite.
- The neurons that regulate appetite appear to be mainly serotonergic, although neuropeptide Y (NPY) and Agouti-related peptide (AGRP) also play a vital role.
- Hypothalamocortical and hypothalamolimbic projections contribute to the awareness of hunger, and the somatic processes controlled by the hypothalamus include vagal tone (the activity of the parasympathetic autonomic nervous system), stimulation of the thyroid(thyroxine regulates the metabolic rate), the hypothalamic-pituitary-adrenal axis and a large number of other mechanisms.
- Opioid receptor-related processes in the nucleus accumbens and ventral pallidum effect the palatability of foods.
- The nucleus accumbens (NAc) is the area of the brain that coordinates neurotransmitter, opioid and endocannabinoids signals to control feeding behaviour.
- The few important signalling molecules inside the NAc shell modulates the motivation to eat and the affective reactions for food.
- These molecules include the DA, Ach, oipoids and cannabinoids and their action receptors inside the brain, DA, muscarinic and MOR and CB1 receptors respectively.
sensors of appetite
- The hypothalamus senses external stimuli mainly through a number of hormones such as leptin, ghrelin, PYY 3-36, orexin and cholecystokinin; all modify the hypothalamic response.
- They are produced by the digestive tract and by adipose tissue (leptin).
- Systemic mediators, such as tumor necrosis factor-alpha (TNFα), interleukins 1 and 6 and corticotropin-releasing hormone (CRH) influence appetite negatively; this mechanism explains why ill people often eat less.
- In addition, the biological clock (which is regulated by the hypothalamus) stimulates hunger.
- Processes from other cerebral loci, such as from the limbic system and the cerebral cortex, project on the hypothalamus and modify appetite.
- This explains why in clinical depression and stress, energy intake can change quite drastically.
individuals that have anorexia have high levels of?
Individuals that have anorexia have high levels of ghrelin, a hormone that stimulates appetite, so the body is trying to cause hunger, but it is being suppressed by the person.
ghrelin and leptin
- ghrelin and leptin are released from the stomach and pancreas, respectively, into the blood stream at the signal of the hypothalamus.
- Ghrelin stimulates feelings of hunger, whereas leptin stimulates feelings of satisfaction from food.
- Any changes in normal production levels of these two hormones will lead to obesity.
- Looking at leptin, the more cells present in a body, the more adipose tissues there are, and thus, the more leptin would be produced.
- This overproduction of leptin will cause the hypothalamus to become resistant to leptin and so, although the pancreas is producing leptin, the body will not understand that it should stop eating.
- This will produce a perpetual cycle for those that are obese
pharmacology related with appetite
- Mechanisms controlling appetite are a potential target for weight loss drugs.
- Appetite control mechanisms seem to strongly counteract under eating, whereas, they appear weak to control over-eating.
- Early anorectics were fenfluramine and phentermine.
- A more recent addition is sibutramine which increases serotonin and noradrenaline levels in the central nervous system, but had to be withdrawn from the market when it was shown to have an adverse cardiovascular risk profile.
- Similarly, the appetite suppressant rimonabant (a cannabinoid receptor antagonist) had to be withdrawn when it was linked with worsening depression and increased risk of suicide.
- Recent reports on recombinant PYY 3-36 suggest that this agent may contribute to weight loss by suppressing appetite. Given the epidemic proportions of obesity in the Western world, and the fact that it is increasing rapidly in some poorer countries, observers[who?] expect developments in this area to snowball in the near future.
- Dieting alone is ineffective in most obese adults - and even obese adults who successfully lose weight through dieting, often put weight back on afterwards.
abnormalities of appetite
- Both genetic and environmental factors may regulate appetite, and abnormalities in either may lead to abnormal appetite.
- Poor appetite (anorexia) can have numerous causes, but may be a result of physical (infectious, autoimmune or malignant disease) or psychological (stress, mental disorders) factors.
- Likewise, hyperphagia (excessive eating) may be a result of hormonal imbalances, mental disorders (e.g. depression) and others.
- Dyspepsia, also known as indigestion, can also affect appetite as one of its symptoms is feeling "overly full" soon after beginning a meal.
- Abnormal appetite may also be linked to genetics on a chromosomal scale.
- In the 1950s, the discovery of the Prader Willi Syndrome, a type of obesity, displayed a causation at a gene locus.
- Additionally, anorexia nervosa and bulimia nervosa are more commonly found in females than males - thus hinting a possibility of a linkage to the X-chromosome.
- A pulmonary consolidation is a region of (normally compressible) lung tissue that has filled with liquid, a condition marked by induration (swelling or hardening of normally soft tissue) of a normally aerated lung.
- It is considered a radiologic sign.
- Consolidation occurs through accumulation of inflammatory cellular exudate in the alveoli and adjoining ducts.
- Simply, it is defined as alveolar space that contains liquid instead of gas.
- The fluid can be pulmonary edema, inflammatory exudate, pus, inhaled water, or blood (from bronchial tree or hemorrhage from a pulmonary artery).
- It is clinically important in pneumonia: the signs of lobar pneumonia are characteristic and clinically referred to as consolidation.
consolidation on xray and air bronchogram
- If the alveoli and small airways fill with dense material, the lung is said to be consolidated.
- It is important to be aware that consolidation does not always mean there is infection, and the small airways may fill with material other than pus (as in pneumonia), such as fluid (pulmonary oedema), blood (pulmonary haemorrhage), or cells (cancer).
- They all look similar and clinical information will often help you decide the diagnosis.
- If an area of lung is consolidated it becomes dense and white.
- If the larger airways are spared, they are of relatively low density (blacker).
- This phenomenon is known as air bronchogram and it is a characteristic sign of consolidation.
- Pneumonia as seen on chest X-ray.
- A: Normal chest X-ray.
- B: Abnormal chest X-ray with consolidation from pneumonia in the right lung, middle or inferior lobe (white area, left side of image).
signs indicating that consolidation might hav occured
- Signs that consolidation may have occurred include:
- Expansion of the thorax on inspiration is reduced on the affected side
- Vocal fremitus is increased on the side with consolidation
- Percussion is dull in affected area
- Breath sounds are bronchial
- Possible medium, late, or pan-inspiratory crackles
- Vocal resonance is increased.
- Here, the patient's voice (or whisper, as in whispered pectoriloquy) can be heard more clearly when there is consolidation, as opposed to in the healthy lung where speech sounds muffled.
- A pleural rub may be present.
- Fever (also known as pyrexia) is one of the most common medical signs and is characterized by an elevation of body temperature above the normal range of 36.5–37.5 °C (97.7–99.5 °F) due to an increase in the temperature regulatory set-point.
- This increase in set-point triggers increased muscle tone and chills.
- As a person's temperature increases, there is, in general, a feeling of cold despite an increase in body temperature.
- Once the new temperature is reached, there is a feeling of warmth.
- A fever can be caused by many different conditions ranging from benign to potentially serious.
- Some studies suggest that fever is useful as a defence mechanism as the body's immune response can be strengthened at higher temperatures, however there are arguments for and against the usefulness of fever, and the issue is controversial.
- With the exception of very high temperatures, treatment to reduce fever is often not necessary; however, antipyretic medications can be effective at lowering the temperature, which may improve the affected person's comfort.
- Fever differs from uncontrolled hyperthermia,in that hyperthermia is an increase in body temperature over the body's thermoregulatory set-point, due to excessive heat production and/or insufficient thermoregulation.