Ch. 11 Efferent peripheral nervous system Midterm 2 on Nov 11 th will cover chapters 8, 10, 11. Today: –Autonomic division Homeostasis Organization Neurotranmsitters and neuromodulators Receptors

Mixed nerves Afferent and efferent fibers Autonomic fibers (involuntary) Somatic motor fibers (voluntary)

Autonomic Division of the Peripheral Nervous System Sympathetic “branch” –dominates in stressful situations –In emergencies “fight or flight” –Always  blood vessel diameter Parasympathetic  “rest and digest”

Sympathetic and parasympathetic contributions to homeostasis Maintain the internal environment Tonic control Antagonistic control Specific receptors determine responses

Autonomic fibers exert tonic control of blood vessels - vasodilation or vasoconstriction - sympathetic fibers - up or down control

Dual antogonistic innervation

Cooperation between sympathetic and parasympathetic effects E.g male reproductive system: –Parasympathetic fibers  penile erection –Sympathetic fibers  ejaculation

Different effect with different receptor: vasodilation or vasoconstriction

Brain regulates autonomic function Hypothalamus, pons, medulla Heart rate, blood pressure, temp. water balance Influence from limbic system and cerebral cortex Also autonomic reflexes e.g. urination

Autonomic efferent pathways **divergence**

Blue, parasympathetic, Red, sympathetic Parasympathetic ganglia are close To the targets

Autonomic neurotransmitters and receptors

Neuroeffector junction: synaptic vesicles are in varicosites

Norepinephrine release from varicosity: - MAO (monoamine oxidase) metabolizes NE