PSL300H1 Lecture Notes - Lecture 1: Negative Feedback, Positive Feedback, Autocrine Signalling
Document Summary
A key aspect of physiology is homeostasis = the process of maintaining a constant internal environment despite changing conditions. Negative feedback for homeostasis, positive feedback for change. Positive feedback: e. g. oxytocin and control of uterine contractions. Biological rhythms result from changes in a setpoint. Gap junctions form direct cytoplasmic connections between adjacent cells. Contact dependent signals require interaction between membrane molecules on two cells. Autocrine signals act on the same cell that secreted them. Paracrine signals are secreted by one cell and diffuse to adjacent cells. Long-distance communication may be electrical signals passing along neurons or chemical signals that travel through the circulatory system. Hormones are secreted by endocrine glands or cells into the blood. Only target cells with receptors for the hormone respond to the signal. Neurotransmitters are chemicals secreted by neurons that diffuse across a small gap to the target cell. Neurohormones are chemicals released by neurons into the blood for action at distant targets.
