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.

Cell Communication

Endocrine Glands produce Hormones (chemicals)

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

Feedback Mechanism to control Blood Pressure

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

Homeostasis is disrupted by paralysis

Discuss with your partner what happens to cell communication when paralysis occurs

Give an example of what can cause paralysis.