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