https://padlet.com/hglenville/1yqnpto6vxea81q Made with joy en-us 2021-12-27 01:22:34 UTC 2026-03-17 12:48:08 UTC hello@padlet.com apankarican https://padlet.com/hglenville/1yqnpto6vxea81q/wish/1974844128 Cells in retina detect loss of light and send an impulse to the Suprachaismatic Nuclei (SCN) cells in the hypothalamus, which adjusts the timing of the release of melatonin from the pineal gland. 

Melatonin is a peptide hormone. It acts on cells with a melatonin receptor. It is produced more at night and less in the morning. 

Increased concentrations of melatonin causes... 
1. drowsiness, which promotes sleep. 
2. core body temperature to drop. 
3. kidneys to produce less urine. 

Teenagers naturally begin and stop producing melatonin 2 hours later than full-grown adults do. This causes them to be alert in the evening and experience sleep-onset insomnia if they try to go to bed early. This also causes sleepiness in the mornings and makes it difficult for them to wake up in the morning. 

With jet lag, the SCN cells and pineal glad are still set to the cycle they were in the previous time zone, and not where the person currently is. This means that they are producing melatonin at the wrong times. This causes... 
1. Fatigue. 
2. Irritability. 
3. Headaches. 
4. Indigestion. 
5. A feeling of needing to sleep in the middle of the afternoon, or a need to stay awake in the middle of the night. 

Melatonin pills help reduce jet lag. They encourage the body to promote sleep at a time better suited to the time zone that the person is in currently. 

When the days are longer and the nights are shorter (summer), the body produces melatonin for a shorter period of time. This means that we get tired later and sleep shorter. 

When the days are short and the nights are longer (winter), the body produces melatonin for a longer period of time. This means that we get tired earlier and sleep longer. 

While melatonin does regulate sleep a lot, it's not actually the primary regulator of sleep. ]]> 2022-01-04 18:21:49 UTC https://padlet.com/hglenville/1yqnpto6vxea81q/wish/1974844128 https://padlet.com/hglenville/1yqnpto6vxea81q/wish/1974853293 What is it:

• stimulates metabolism in almost ALL body cells
  • increasing metabolic rate and rate of protein synthesis & triggers growth
• Regulates body temperature
• secreted by the thyroid gland 
• the structure includes four atoms of iodine and the amino acid tyrosine
• activates nuclear transcription of large numbers of genes for the synthesis of enzymes, structural proteins, transport proteins and other substance

Thyroxine and Temperature Regulation

1. temperature-activated neurons in the hypothalamus (a little region in the brain) sense when the body temperature is cooling  
2. from there a couple of different hormones are released into the blood in response to the body cooling, eventually secreting thyroxine which travels throughout the whole body. 
3. Thyroxine triggers increased metabolism in all body cells.  - ↑  metabolism = ↑ body heat therefore the body warms up.  
   
   

Thyroxine Deficiency

• "hypothyroidism"
• without thyroxine = slower metabolism
• symptoms: lack of energy, feeling tired, forgetfulness and depression, weight gain... 
• causes: Iodine deficiency, Anatomic defect in the thyroid gland, Disease of the thyroid, Tumors of the hypothalamus and/or pituitary, Thyroid cancer
  
  

Iodine Deficiency

]]> 2022-01-04 18:26:03 UTC https://padlet.com/hglenville/1yqnpto6vxea81q/wish/1974853293 jsaad24 https://padlet.com/hglenville/1yqnpto6vxea81q/wish/1974870346 Leptin is a protein based hormone produced and then secreted by cells in adipose tissues (store fat cells)
Blood leptin concentration is dependent on diet (food intake) and the amount of adipose tissue in the body.

There are leptin receptors in the hypothalamus
Once the hypothalamus detects 
1. Hypothamamus detects
2. Leptin is secreted by adipose tissue
3. Targets hypothalamus to regulate appetite activity

Leptin binds to these receptors in the hypothalamus which causes appetite inhibition and increased energy expenditure.

When fat mass decreases, the level of plasma leptin decreases. This is to regulate fat storage. There is also a decrease in body temperature and energy expenditure is decreased. This also applies in contrast when there is a fat mass increase.

Most obese humans do produce leptin but have an insensitivity.

This was discovered when injections cured obesity in mice that could not produce leptin, but it was not directly related to obesity in humans.]]> 2022-01-04 18:34:08 UTC https://padlet.com/hglenville/1yqnpto6vxea81q/wish/1974870346