Autonomic Nervous System A look at sympathetic and parasympathetic divisions, Portions of Chapter 17

Compare Somatic & Autonomic Somatic nervous system- voluntary, consists of sensory convey info from somatic & special sensory receptors, primarily head, body wall, & limbs to CNS motor neurons to conduct impulses to skeletal muscles only Autonomic nervous system-involuntary,consists of sensory neurons convey info from autonomic sensory receptors, located primarily in viserca, to the CNS motor neurons conduct nerve impulses to smooth muscle, cardiac muscle, glands and adipose tissue. Motor portion consists of 2 branches: sympathetic division & parasympathetic division

Autonomic Nervous system ANS sensory neurons- usually interoreceptors, monitor: blood CO2, degree of stretch in walls of organs or b.v. Can produce conscious sensations if intense Damaged viscera or angina pectoris Somatic pain can produce changes in ANS ANS motor neurons regulate viscera by  or  activity of effectors (smooth & cardiac muscle, glands) ANS effector tissues generally function even if their nerve supply is interrupted ex- heart being removed for transplant is still beating

Somatic vs. Autonomic Special & somatic senses Voluntary from c.c, some basal ganglia, cerebellum, brain stem, s.c. 1 neuron: motor neuron from CNS to effector NT= Ach Effector= skeletal muscle Contraction of skeletal muscle Interoreceptors, some special and somatic Involuntary; from limbic sys, hypothalamus, brain stem and s.c., some c.c 2 neuron: pregang  postgang  effector NT=Ach in pre, Ach or NE in post Smooth & cardiac muscle, glands Contract or relax smooth muscle,  or  force of cardiac,  or  gland secrete

Dual innervation Motor output of ANS has 2 branches: Sympathetic and parasympathetic Most organs have dual innervation- receive impulses from both sympathetic & para Generally, one will be excitatory and the other inhibitory

Sympathetic & Para- fig 15.2,3 Sympathetic = fight or flight response: Pupils dilate  heart rate, force of contraction, b.p airways dilate bv to kidneys and GI constrict  blood flow there &  urine output bv to skeletal, cardiac muscle dilate glycogenolysis & lipolysis by liver;  blood glucose Processes not essential to stress response slow or stop “E situations:” exercise, emergency, excitement, and embarrassment Parasympathetic= resting & digesting activities SLUDD- salivation, lacrimation, urination, digestion, defecation 3 decreases: heart rate, airway diameter, pupil diameter

Sympathetic ganglia Sympathetic- at synapses between pre & postganglionic neurons, 2 groups of ganglia: sympathetic trunk- vertical row on either side of the vertebral column extending from the base of the skull to the coccyx since near the spine, most axons are short generally innervate organs above the diaphragm. prevertebral ganglia- anterior to vertebral column & close to the large abdominal arteries generally post ganglionic innervate organs below diaphragm 3 main: celiac, superior mesenteric, inferior mesenteric Preganglionic may synapse w/ 20+ postganglionic sympathetic affect almost entire body simultaneously

Parasympathetic ganglia Parasympathetic- at synapses between pre & postganglionic neurons in: terminal ganglia -close to or within wall of viscera axons extend CNS to terminal ganglion in an innervated organ  longer than most sympathetic preganglionic axons In ganglion, presynaptic usually synapes with 4-5 postsynaptic neurons all supply single visceral effector parasympathetic response localized to one effector

Symp vs. Para-- effects Balance between 2 regulated by hypothalamus Generally, effects are regulating controlled conditions in the body such as: blood pressure, by adjusting heart rate force of ventricular contraction, & b.v. diameter regulating diameter of bronchial tubes adjust motility & muscle movement in digestion defecation & urination by regulating sphincters Few have only sympathetic innervation: Sweat glands, arrector pili, kidneys, spleen, bv, adrenal medulla

Comparison of NT, table 17.2 Cholinergic neurons- release Ach, brief effect due AchE Ach excitatory at NMJ, inhibitory at some others ALL symp & parasymp preganglionic neurons Symp postganglionic innervate (most sweat glands) ALL parasymp postganglionic neurons Adrenergic neurons- release norepinephrine (NE), AKA noradrenalin Produce actions similar to Ach (excite or inhibit) most sympathetic postganglionic neurons