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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, orforce 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