The Endocrine System

Endocrine System Glands-secrete hormones Hormones- chemical substances that carry messages through the blood and other bodily fluids For example, The pituitary gland makes growth hormone, which tells your cells grow. Hormones are another, other than neurotransmitters, way for cells to communicate.

Hormones Vs. Neurotransmitters Nervous System Messages through Synapses Quick transmission Specific neuron targets Stimulate membranes to excite or inhibit Hormones Endocrine System Messages through blood Slower transmission Further targets Regulate by diffusing throughout body

Pituitary Gland Center control of the endocrine system that secretes a large number of hormones Directed by hypothalamus Controls other endocrine glands

Thyroid Gland Makes hormones that affect growth and energy use Thyroxine Oversupply=Overactive, no sleep, weight loss Undersupply=Lazy, lethargic, weight gain

Parathyroid Glands Make hormones that control mineral levels in bone and blood

Adrenal Glands Make a hormone called adrenalin/epinephrine Emergency energy Heartbeat, breathing, etc.

Sex Glands Ovaries make female sex hormones called estrogen and progesterone. Regulates Female sex characteristics Testes make a male hormone called testosterone. Regulates male sex characteristics

Feedback Systems Almost all body functions use feedback systems, responses to changes, to maintain homeostasis. Homeostasis- variables are regulated so that internal conditions remain stable and relatively constant

Feedback systems work together with the Nervous and Endocrine Systems. Sensory Nerve Cells- detect changes in the body and… 1. Send a message to the brain for a quick response. OR 2. Relay message to the endocrine system to send chemical messages through the blood.

Why do we need feedback? Feedback systems are always monitoring and regulating factors like body temperature, pH, and amounts of oxygen, nutrients and carbon dioxide. Feedback systems make sure the amounts of these substances in body tissues and liquids stays constant even if there are changes in the environment.

Types of Feedback Systems 1. Negative feedback High amounts of substances need to be reduced Example: High amounts of CO2 in the body when you exercise would make you breathe more quicklyexhaling CO2

Types of feedback 2. Positive feedback: A stimulus causes production of a substance which increases the activity and more substance is produced. Ex: Contractions in labor cause production of oxytosin, which increases contractions, causing production of more oxytosin.

Feedback Examples... Regulating substances going into and out of each cell Regulating the flow of blood in your heart or lungs. There is a chemical sensor in your arteries that can tell if oxygen is too low, or CO2 is too high. In both cases, this message will cause you to breathe more quickly. Keeping your body temperature constant (98.6 F) Maintaining a normal body pH (7.4) in your cells and body fluids.