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Endocrine system

Endocrine system
Endocrine system

Carries signals similar to the nervous system but the signals are slower and last longer

Hormones:

Chemical molecules that carry signals that last for a long time
Many circulate through the whole body and bind to specific receptors
Paracrine signaling is when cells secrete hormones that degrade quickly do they only affect nearby cells
Autocrine signaling is when hormones are sent within a cell or to adjacent cells
Hormones bind to proteins called signal receptors

There are broadly 5 types,
Eicosanoids which are made from oxidation of arachidonic acid or other poly unsaturated fatty acidsFatty acids having a backbone of multiple carbon-carbon double bonds
Steroids which are organic compounds with 4 fused rings, they are derived from cholesterol, they are lipid soluble
Amino acid derived hormones which are derived from amino acids, they are water soluble
Peptide hormones which are peptides, they are water soluble
Gaseous hormones which are gaseous

Negative feedback loop:

Negative feedback loop is when when output of a system reduces the amount of subsequent output produced either directly ot indirectly.
This leads to stability in amount compared to a positive feedback loop
This is common in body, especially in the endocrine system

Gland:

Organ which secrete substances

Exocrine glands:

Glands which secrete substances outside the body
These have ducts

Endocrine glands:

Glands which make and secrete hormones inside the body
These don't have ducts
They have blood vessels connected to them and directly release their content in the blood
In humans there are 10 endocrine glands,

  • Pineal gland,
  • Pituitary gland,
  • Pancreas,
  • Ovaries,
  • Testicles,
  • Thyroid gland,
  • Parathyroid gland,
  • Hypothalamus and
  • Adrenal glands

Hypothalamus:

It is a gland that communicates between the nervous system and the endocrine system
It is connected to the pituitary gland
It regulates the release of hormones by both the anterior and posterior pituitary glands

Thyroid:

The thyroid(gland) regulates metabolism, appetite, muscle function, blood pressure, heart rate and other stuff

Pituitary gland:

The pituitary glands is the size of a kidney bean and is located at the base of the brain
The pituitary glands secretes hormones which instruct other glands to make hormones

The pituitary glands consists of 2 different glands that are fused to each other

The posterior pituitary is an extension of the hypothalamus
The posterior pituitary glands secretes oxytocin
Oxytocin stimulates the contraction of the uterus and has a role in social recognition, pair bonding and anxiety
It also secretes anti diuretic hormone which tells the kidneys to retain water

The anterior pituitary secretes a lot of hormones
One of the hormones is the thyroid stimulating hormone(TSH)
This makes the thyroid produces the thyroid hormone which increases the metabolism
This makes the pituitary gland produce less TSH
This is an example of a negative feedback loop

Adrenal glands:

These glands are responsible for your fight or flight response
When the sympathetic nervous system senses a potential threat, the hypothalamus instructs the pituitary to secrete ACTHAdrenocorticotropic hormone
ACTH tells the adrenal glands to make adrenalineepinephrine
Adrenaline tells other organs to:

  • Cut blood flow to the digestive system and the gonads
  • Increase blood flow to the lungs, muscles
  • Increase the heart rate and blood pressure
  • Enhancing your sense of smell
  • Dilating the pupils
  • Increases aleartness
  • Decreases pain felt

The adrenal glands also make hormones which help the kidneys in regulating the level of salt in the body

Pancreas:

Pancreas are the largest glands in the human body
It regulates the amount of glucose in your blood
When blood glucose is high, it secretes insulin which tells the cells to absorb glucose, adipose cells convert glucose to fat, liver and muscle cells convert glucose in glycogen
When blood glucose is low, it releases glucagon which stimulates the liver and muscles to start breaking glycogen and fat to release glucose

Testes:

The testes make androgens, primarily testosterone
They also make estrogen but a lot less than ovaries, as estrogen is a prerequisite for serotoninImportant neurotransmitter
Testosterone is responsible for the appearance of secondary sexual characteristics in men
Testosterone is involved in the development of the testicles and the prostate

Ovaries:

Ovaries make estrogens and progestins They also make androgensIncluding testosterone but a lot less than testes, as androgens are a prerequisite for the synthesis of estrogen
Estrogen is responsible for the appearance of secondary sexual characteristics in women
Estrogen is required for the production of serotonin
Progesterone prepares the uterus for pregnancy and the mammary glands for lactation
Progesterone and estrogen collectively promote menstrual changes in the inner layer of the uterus