KAAP220 Lecture Notes - Lecture 23: Arrector Pili Muscle, Coronary Circulation, Skeletal Muscle

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Lecture 23
The autonomic nervous system
Somatic NS - physical interaction with the external environment; can control voluntarily;
receptors are exteroceptors and proprioceptors
Controls conscious and some subconscious (reflexes) skeletal muscle contractions
2 motor neuron pathway with an upper motor and lower motor
Upper motor is in primary motor cortex
ANS controls visceral function - mostly outside our awareness; regulates internal environment,
maintaining homeostasis; 2 parts - visceral sensory (detect changes from interoceptors) and visceral
motor (involuntary and reflexive motor to smooth muscle, cardiac muscle, and glands); effectors
are smooth muscle, cardiac muscle, and glands
Control centers located in the hypothalamus (in the diencephalon)
2 motor neurons carry this information in sequence from the CNS out to the visceral effectors
Neuron chain - preganglionic neurons and ganglionic neurons (postganglionic)
Somatic - 1 motor neuron from CNS to skeletal muscle; cell bodies in anterior horn of spinal cord
or in brainstem nuclei
Autonomic - 2 motor neuron chain from CNS to effectors; preganglionic cell bodies
Divisions of ANS
Sympathetic
Parasympathetic
Usually have opposing effects - may also work independently; sometimes can innervate separate
structures; sometimes can work together in processes
Sympathetic - coordinates and directs the body’s response to stressful or frightening situations -
emergency, excitement, and exercise; “fight or flight”
Parasympathetic - conserves energy; bring us back down from a sympathetic response; restores
nutrients that maybe were expended during fight or flight; “rest and digest”
Sympathetic activity
Dilates pupils - more light comes in
Increases HR; bronchodilates - makes airways bigger, which allows more air to get in your lungs
and more oxygen to your blood
Vessels vasoconstrict to skin and GI - don’t need blood to go to our skin or go digest when we’re
stressed, need oxygenated blood to supply the heart and skeletal muscle (to run away)
Vasodilates coronary arteries and skeletal muscle arteries
Activates arrector pili and sweat glands
Secretion of epinephrine and norepinephrine
Stimulates breakdown of molecules for fuel
Parasympathetic activity
Constricts pupils, accommodation (lens is rounded out so you can see things closer to your face as
opposed to far away when you’re running in fear)
Decreases HR
Bronchoconstricts
Stimulates secretion of tears and saliva
Increases GI motility - increases smooth muscle in the gut
Vasodilates vessels to GI
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