Today: Response and feedback loops: setpoints Speed and specificity of control systems Patterns of control pathways The organization of the nervous system Neurons Midterm test: Monday Oct. 7: 8:30 – 9:20 multiple choice questions Location: A- P in the Education Gym Q-Z in Erie Hall (lecture hall)
Setpoints can vary Acclimatization – adaptation to a given set of environmental conditions (first day of spring like weather) Acclimation – adaptation to laboratory setting
Endocrine and Nervous Reflexes Specificity of target cells Nature of signal Speed Duration of action Stimulus intensity coding
Specificity of target cells A neuron has a specific target cell. Many tissues may have receptor proteins for a hormone and may respond to the hormone.
Nature of signal In neurons, electrical signals travel long distances and chemical signals (neurotransmitters) move to the target cell.
Nature of signal The endocrine system uses chemical signals.
Electrical signals travel long distances and Nature of signal: Neuroendocrine: Electrical signals travel long distances and chemical signals (neurohormones) move into blood vessels.
Speed Electrical signals conducted very quickly Rapid signal transduction with many neurotransmitters Hormones move by diffusion from endocrine cell to target (slower) Some responses take quite a long time
Duration of action Nervous control is shorter than endocrine control Nervous – usually neurotransmitter is rapidly removed
Stimulus intensity coding Intensity is coded by neuronal firing frequency amount of neurotransmitter The amount hormone that is released codes the intensity.
Knee jerk reflex Lactation, oxytocin Autonomic stimulation of insulin release Growth hormone
Testosterone Low glucose and beta cells
Organization of the nervous system Sensory Receptors afferent pathway central nervous system (CNS, brain and spinal cord efferent neurons (peripheral nervous system PNS) target PNS: Somatic motor division Autonomic division: Sympathetic Parasympathetic
Cells of the nervous system: -neuron