The Endocrine System
The endocrine system consists of glands that secrete chemicals into the blood steam that help control bodily functioning.
- Hormones are the chemical substance released by the endocrine glands.
- In a way, hormones are like neurotransmitter in the nervous system. They are stored for subsequent release as chemical messengers, and once released they diffuse through the blood stream and bind to special receptors on target cells.
- Some chemical substances do double duty, functioning as hormones when they are release in the endocrine system and as neurotransmitter in the nervous system (nor pine phrine, for example).
Difference between Hormones and Neurotransmitters:
|Travel to distant cells||transmitted short distance with lightening along specific pathways|
|Acts on many target cells throughout the body|
Major Endocrine Gland:
- Pineal gland
- Pituitary gland
- Para thyroid glands
- Thyroid glands
- Adrenal gland
- Ovary (female) placenta (female)
Regulation of Changing Conditions in the Body:
Some hormones are released in response to changing conditions in the body and act to regulate those conditions. For example.
- Hormones released by stomach and intestines digestion.
- Kidney hormones regulate blood pressure
- Pancreatic hormone (insulin) is essential for cells to use sugar from blood.
Hormones release tends to be pulsatile. That is hormones tend to be released several times per day in brief bursts or pulses that last only a few minutes. The levels of many hormones increased or decreased in a rhythmic pattern throughout the day.
“Master Gland” of Endocrine System:
- Much of the endocrine system is controlled by nervous system through the hypothalamus. This structure at the base of the forebrain has intimate connections with the pea sized pituitary gland. The pituitary gland releases a great variety of hormones that fan out around the body, stimulating actions in the other endocrine glands. In this sense, the pituitary is the master gland although the hypothalamus is the real power behind the throne.
Intermeshing of nervous system and the Endocrine System.
- Intermeshing can be seen in the fight or flight response.
- In times of stress, hypothalamus signals Pituitary glands and ANS
In response, adrenal glands secrete hormones that radiate throughout the body propelling it to cope with an emergency. The communication between brain and endocrine in not a one-way street as hormonal fluctuation can trigger responses in the brain. For example, hormones secreted by the adrenal medulla in response to stress can signal the hypothalamus to inhibit further hormone output. The levels of many hormones are regulated through negative feedback system. When a hormone increases to a certain level, signals are sent to the hypothalamus or the relevant endocrine gland to reduce or stop further secretion of that hormone.
Modulating Human Physiological Development:
- Pituitary glands release Gonadotropins hormones which affect the gonads, or sexual glands. Prior to birth, these hormones direct the formation of the external sexual organs in the developing fetus.
- At puberty, increased levels of sexual hormones are responsible secondary sexual characteristics such as male facial hair and female breasts.
- Other hormones are responsible are spurt in physical growth that occur around puberty.
- Contribution to working memory and relational reasoning have led some theorists to suggest that it houses some sort of “executive control system” which is thought to monitor, organize and direct thought processes. Consistent with this hypothesis, people who suffer damage in the pre-frontal cortex show defaults in planning, paying attention, and seething organized.