Human Biology – Bio 156
Week 4 –Endocrine
WTK = Hormones, Endocrine Glands, Pituitary Gland, Thyroid Gland, Melatonin
The endocrine system contains glands and tissues that provide long term communication throughout the body.
HORMONES are the chemical signals that communicate with other glands or tissues.
ENDOCRINE GLANDS are ductless which means they secrete their hormones directly into the bloodstream.
The affect of hormones can be controlled by antagonistic hormones. Insulin lowers blood glucose levels while glucagon raises it.
They can also be controlled by negative feedback. When blood glucose levels rise the pancreas secretes insulin which causes the liver to store glucose. As the level of glucose in the blood decreases, the pancreas is no longer stimulated to secrete insulin.
Endocrine Glands (Hypothalamus)
The hypothalamus controls the autonomic nervous system, i.e. heartbeat, body temperature and water balance. If the blood temperature is too cold, it tells the body to shiver. If the blood temperature is too hot it tells the body to sweat.
It also controls the secretions of the PITUITARY GLAND, to which it is connected.
The hypothalamus is a tiny bit of gray matter found at the base of the brain. Some of its outgoing messages are electrical while others are hormonal and work in conjunction with the pituitary gland.
The pituitary gland is pea-sized and hangs from the hypothalamus by a thin stalk. It has two parts; the anterior pituitary and the posterior pituitary.
Endocrine Glands (Pituitary)
The posterior, or rear part, is made up of axon endings of neurons whose cells bodies are in the hypothalamus.
It secretes a hormone called antidiuretic hormone (ADH) that targets the kidneys telling them to conserve water.
It also produces oxytocin, which targets the breasts of pregnant or nursing women as well as triggering labor and childbirth.
Both ADH and oxytocin are made in the hypothalamus but are...