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Aim: How do cells of the body communicate?
1.2j Receptor molecules play an important role in the interactions between cells. Two primary agents of cellular communication are hormones, and chemicals produced by nerve cells (neuroreceptors). If nerve or hormone signals are blocked, cellular communication is disrupted and the organism’s stability is affected.
Aim: What are the target tissues for various hormones?
HypothalamusThe hypothalamus makes hormones that control the pituitary gland. In addition, it makes hormones that are stored in the pituitary gland.
Pituitary glandThe pituitary gland produces hormones that regulate many of the other endocrine glands.
Parathyroid glandsThese four glands release parathyroid hormone, which regulate the level of calcium in the blood.
ThymusDuring childhood, the thymus releases thymosin, which stimulates Tcell development.
Adrenal glandsThe adrenal glands release epinephrine and nonepinephrine, which help the body deal with stress.
Pineal glandThe pineal gland releases melatonin, which is involved in rhythmic activities, such as daily sleep-wake cycles.
ThyroidThe thyroid produces thyroxine, which regulates metabolism.
PancreasThe pancreas produces insulin and glucagon, which regulate the level of glucose in the blood.
OvaryThe ovaries produce estrogen and progesterone. Estrogen is required for the development of secondary sex characteristics and for the development of eggs. Progesterone prepares the uterus for a fertilized egg.
Testis The testes produce testosterone, which is responsible for sperm production and the development of male secondary sex characteristics
Section 39-1 Endocrine Glands
Hormones travel in circulatory system to target organs
• Ovary (gland) produces estrogen (hormone)
• Estrogens are a family of related molecules that stimulate the development and maintenance of female characteristics and sexual reproduction
Aim: What is feedback control…How does it maintain homeostasis?
Work in your groups to discuss feedback
Beta cells release insulin into the blood
Body cells absorb glucose
Blood glucose level decreases
Homeostasis: Normal blood glucose level
Blood glucose level decreases
Alpha cells release glucagon into blood
Liver converts glycogen to glucose
Blood glucose level increases
Blood glucose level increases
Liver converts glycogen to glucose
Figure 39–10 (Text) Actions of Insulin and Glucagon – Feedback Section 39-2
Heating system turns on
Thermostat senses temperature change and switches on heating system
Thermostat senses temperature change and switches off heating system
Room temperature decreases
Section 35-1
Examples of Feedback Inhibition
A home heating system uses feedback inhibition to maintain a stable, comfortable environment within
a house
Neurons also communicate by producing chemicals
Nervous
System
Nerves are made up of
Neurons
For communication between neurons to occur, an electrical impulse must travel along the nerve.
Information from one neuron flows to another neuron across a synapse
All messages are passed between connected neurons in the form of chemicals called neurotransmitters.
Neurons in the brain also communicate with chemicals
Serotonin, Histamine, Dopamine, Norepinephrine and Epinephrine