NERVOUS SYSTEM: Sympathetic Nervous System

Chapter 1: Introduction: Physiology of Stress

  • Stress is a useful response in life-threatening situations

  • Sympathetic nervous system responds to stress by redirecting energy to the brain, heart, and muscles

  • Modern life triggers stress responses even in non-life-threatening situations

Chapter 2: How Signals Travel to Effectors

  • Signals in the autonomic nervous system cross two synapses

  • Neurons travel from the spinal cord to ganglia, where they synapse with another nerve fiber

  • The final synapse leads to an effector organ, creating a response

Chapter 3: Hormones & Neurotransmitters Communicate Stress

  • Stress response involves neurotransmitters and hormones

  • Neurotransmitters are released by neurons to communicate with other neurons or effector organs

  • Hormones are secreted by glands and regulate various bodily functions

Chapter 4: Preganglionic Fibers Release Acetylcholine (ACh)

  • Preganglionic neuronal axons carry signals from the brain to ganglia

  • Acetylcholine (ACh) is released as a neurotransmitter in sympathetic ganglia

  • ACh stimulates action potentials in postganglionic fibers, boosting the signal

Chapter 5: Postganglionic Fibers Release Norepinephrine

  • Postganglionic fibers release norepinephrine as a neurotransmitter

  • Norepinephrine crosses the final synapse and creates a response in the effector organ

Chapter 6: Adrenal Glands Release Norepinephrine and Epinephrine as Hormones

  • Preganglionic fibers also release ACh to the adrenal glands

  • Adrenal medulla releases epinephrine and norepinephrine as hormones

  • Hormones travel through the bloodstream to various organs

Chapter 7: Neurotransmitters vs. Hormones

  • Norepinephrine can function as both a neurotransmitter and a hormone

  • Its function determines whether it is referred to as a neurotransmitter or a hormone

Chapter 8: How Norepinephrine Works: Alpha and Beta Receptors

  • Norepinephrine works by both stimulating and inhibiting the same systems in the body simultaneously

  • Norepinephrine causes an increase in blood flow in some parts of the body while restricting blood flow in other areas

  • The response to norepinephrine depends on the type of receptors present on the effector cells

    • Smooth muscle cells controlling some blood vessels have alpha receptors, which cause contraction and restrict blood flow

    • Smooth muscle cells controlling other blood vessels have beta receptors, which cause relaxation and increase blood flow

  • The smooth muscle around blood vessels that feed skeletal muscles have beta receptors to provide oxygen to the muscles

  • The blood vessels leading to the stomach and intestines have alpha receptors to reduce blood flow to those areas

  • The sympathetic responses work together to create a full-body response in emergencies

  • Frequent activation of the sympathetic nervous system and the stress response can have negative consequences like high blood pressure, digestive problems, and immune system suppression

Chapter 9: Review

  • The sympathetic nervous system controls the body's stress response

  • Signals in the sympathetic nervous system travel to effectors using acetylcholine in the ganglion and norepinephrine at the effector

  • Signals can also go directly to the adrenal glands, where norepinephrine and epinephrine are secreted as hormones

  • The same messenger chemical can evoke different responses depending on the receptors present

    • Alpha receptors cause smooth muscles to constrict

    • Beta receptors cause smooth muscles to relax

Chapter 10: Credits

  • The episode was written by Kathleen Yale, edited by Blake de Pastino, and consulted by Dr. Brandon Jackson

  • The director and script supervisor is Nicholas Jenkins, the editor is Nicole Sweeney, the sound designer is Michael Aranda, and the