Melzack and Wall

Building on the purely biomedical model of pain, the biopsychosocial model of pain takes into account complex interactions between biological factors (e.g., hormones, genetics, and the body’s natural pain-killing compounds, known as endogenous opioids), psychological factors (e.g., mood, pain coping, and pain …

Psychological factors, such as the situational and emotional factors that exist when we experience pain, can profoundly alter the strength of these perceptions. Attention, understanding, control, expectations, and the aversive significance can affect pain perceptions.

hypothalamus

You may feel hungry frequently if your diet lacks protein, fiber, or fat, all of which promote fullness and reduce appetite. Extreme hunger is also a sign of inadequate sleep and chronic stress. Additionally, certain medications and illnesses are known to cause frequent hunger.

Eating behavior is also believed to be linked with brain networks besides factors such as hormone modulation, impulsivity and inhibitory control1. Reward networks including the orbitofrontal cortex and insula are the most affected by eating behaviors12,13,14,15.

Anorexia is a mental health condition that involves compulsively restricting food intake. Because of a restricted diet, many people with anorexia experience cognitive problems. In extreme cases, anorexia can cause brain damage. Research has shown that starvation caused by anorexia can lead to brain damage.

Stress can influence our appetite in several ways. Short periods of stress can inhibit our appetite, but in the long run, too much stress can increase it, trigger food cravings, and cause weight gain. Using a mouse model, new research examines the neuroscience behind stress eating, with a focus on the brain’s amygdala.

Based on this behavioral neuroscience, it is not surprising that a dysregulation in these feeding-reward-related neurotransmitters and brain areas is seen in studies of eating disorders. Dopamine (blue), serotonin (green), acetylcholine (red) and the opioids (orange) have each been indicated in disordered eating.

They found that serotonin produced by these cells is a signal to other neurons in the circuit, leading to an increase in anxiety. Giving mice an SSRI has the same effect on this brain circuit as putting the animals in a fearful situation: Serotonin levels rise and anxiety-like behaviors increase.

Long-Term Effects

• Bone weakening (osteoporosis).
• Anemia.
• Seizures.
• Thyroid problems.
• Lack of vitamins and minerals.
• Low potassium levels in the blood.
• Decrease in white blood cells.
• Amenorrhea (absence of menstruation in females).

Anorexia Nervosa, Restricting-Type Prolonged food restriction causes muscular atrophy of the entire digestive tract. This leads to slow stomach emptying (called gastroparesis) and is a direct cause of the trapped gas, bloating and abdominal distention seen with anorexia.