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Autonomic Nervous System

Autonomic Nervous System. Controls automatic functions at subconscious level ______________ nervous system - nerves emerge from thoracic and lumbar vertebral regions ( thoracolumbar system ) Thoracic nerves 1-13, Lumbar nerve 1

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Autonomic Nervous System

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  1. Autonomic Nervous System • Controls automatic functions at subconscious level • ______________ nervous system - nerves emerge from thoracic and lumbar vertebral regions (thoracolumbar system) • Thoracic nerves 1-13, Lumbar nerve 1 • ____________________ nervous system - nerves emerge from brain and sacrum (cranial-sacral) • Cranial nerves 3, 7, 9, 10; Sacral nerves 2, 3, 4

  2. Table 13-3. Effects of Sympathetic and Parasympathetic Nervous Systems Sympathetic System Parasympathetic System Effect Effect Heart rate Increases Decreases Force of heart contraction Increases No significant effect Diameter of bronchioles Increases (dilates) Decreases (constricts) Diameter of pupil Increases (dilates) Decreases (constricts) GI motility, secretions,and blood flow Decreases Increases Diameter of skin blood vessels Decreases No significant effect Diameter of muscle blood vessels Increases No significant effect Diameter of blood vessels to kidney Decreases No significant effect

  3. Neurotransmitters and Receptors • Sympathetic nervous system • 1º neurotransmitter—_____________________ • Released from Sympathetic POSTganglionic neurons • ADRENERGIC neurons - neurons that release norepinephrine • Epinephrine/norepinephrine also released from adrenal medulla • To elicit an effect, effector organ must contain receptor for epi/norepi

  4. Neurotransmitters and Receptors 1. ______- adrenergic receptors – cause vasoconstriction of skin, GI tract, and kidney (don’t need to digest, make urine, or bleed profusely) 2. _______-adrenergic receptors - increase heart rate and force of contraction 3.________-adrenergic receptors - cause bronchodilation (relaxation)

  5. Neurotransmitters and Receptors • Parasympathetic nervous system • 1º neurotransmitter—__________________ • CHOLENERGIC neurons - release acetylcholine • (Even though norepinephrine is the neurotransmitter associated with the sympathetic nervous system, the PREganglionic neuron in BOTH the Sympathetic and Parasympathetic systems is a CHOLINERGIC neuron that releases ACETYLCHOLINE) • 2 types: • Nicotinicreceptors- found on POSTganglionic neurons in BOTH the Sympathetic and Parasympathetic systems • Muscarinicreceptors- found on the target organs and tissues supplied by the postganglionic neuron of the parasympathetic nervous system

  6. Summary: receptor types

  7. Reflexes Reflexes are rapid, automatic responses to stimuli. They serve to protect the body and maintain homeostasis • ____________ reflexes - involve contraction of skeletal muscles • _______________ reflexes - regulate smooth muscle, cardiac muscle, and endocrine glands • _______________ reflex - stimulus and response are on same side of body • ________________ reflex - starts on one side of body and travels to opposite side

  8. Reflex Arc 5 Components: Sensory receptor—activated by stimulus Sensory neuron—transports AP to gray matter of spinal cord or brain stem (cranial n.) and synapses with other neurons Interneuron—sensory info integrated with info from other sensory neurons Motor Neuron—response is sent out via motor neuron Target organ—effector cell

  9. Stretch Reflex (tap knee) • Monosynaptic (1) reflex arc; ipsilateral reflex • Involves 1 sensory neuron and 1 motor neuron • Signals also sent to: • Antagonistic muscle (inhibitory) • Cerebellum/Cerebrum

  10. Withdrawal Reflex • Also called flexor reflex; ipsilateral reflex • Several interneuron synapses • Several segments of spinal cord • Results in: • Contraction of muscles • Before cerebrum is aware • Inhibition of antagonist muscles

  11. Crossed Extensor Reflex • Contralateral reflex • Withdrawal reflex initiated • Afferent sensory neuron synapses with interneurons • Causes contraction of opposite extensor muscles

  12. CNS Moderation of Reflexes • Upper CNS (brain) normally produces an inhibitory effect on the reflex arcs (muffled effect) • With injury, intact reflex arcs caudal to spinal cord trauma become __________________ • Trauma to a portion of the reflex arc results in either ______________ or absent reflexes

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