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Applied Physiology: Lecture 7

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Autonomic Nervous System
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controls visceral functions largely below the level of consciousness (Includes: heart rate, digestion, respiratory rate, salivation, perspiration, pupil diameter, micturition)
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What are the 3 major categories for the ANS?
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-Maintaining homeostatic conditions within the body -Coordinating the body’s responses to exercise and stress -Assisting the endocrine system to regulate reproduction
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Divisions of the ANS:
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1) Sympathetic 2) Parasympathetic 3) Enteric
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What are the neurochemical differences between the sympathetic and parasympathetic nervous systems?
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-*Sympathetic Division – adrenergic * (Adrenaline-like actions associated with Symp nerve activation In general: use of metabolic resources and emergency responses of the body) -*Parasympathetic Division – cholinergic* (ACh-like actions with Para nerve activation In general: restoration of body’s reserves and elimination of waste products)
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Give examples of the reciprocal and synergistic relationships between the sympathetic and parasympathetic NS
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1)Reciprocal ex. Heart Rate ↑ firing sympathetic nerves and a ↓ firing parasympathetic nerves results in ↑ HR 2) Synergistic Relationship: During secretion of exocrine glands of GI tract Para nerves activation: ↑ volume and enzyme content in the secretion Symp. nerves activation: contributes mucus to total secretory product
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Explain the Efferent Chain for the ANS
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Efferent path consists of *2-neuron chain* with a synapse interposed between CNS and effector cells Cell bodies of the ANS are located in the spinal cord or brainstem nuclei Efferent fiber emerges as a preganglionic axon It synapses with neurons in a peripheral ganglion Neuron in the ganglion projects as a postganglionic axon to the autonomic effector cells
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T/F: Preganglionic nerve terminals of both the sympathetic and parasympathetic nervous system release acetylcholine (ACh)?
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T
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What are the two types of receptors that ACh uses?
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Synapse at this site uses *nicotinic receptor* (same as at the neuromuscular junction) Synapse at Para postganglionic neuron/effector uses a *muscarinic receptor*
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What are the major differences between Nicotinic and muscarinic receptors after binding to ACh?
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*Nicotinic* Direct ligand-gated type Receptor and the ion channel are contained in the same structure *Muscarinic* Indirect ligand-gated type – Uses a G protein to link receptor and effector
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How is ACh action terminated after binding at a nicotinic or muscarinic receptor?
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-Diffusion away from the receptor site -Enzymatic action of acetylcholinesterase
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What is norepinephrine? What adrenegic receptors does it interact with?
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*-A catecholamine neurotransmitter* (Released at postganglionic synapses of the Symp division (exception of sweat glands) NE receptors can also be activated by epinephrine (adrenaline)) *Adrenergic receptors* α – respond best to epinephrine > NE > isoproterenol β – respond best to isoproterenol > epinephrine > NE
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What is an adrenergic receptor? What neurotransmitters does it bind?
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-Indirect, ligand-gated, G protein-linked type (Share a structural similarity w/ muscarinic type of ACh receptor) -NE and epinephrine
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Where do preganglionic neuros originate from? Where do they exit?
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– intermediolateral horn of the thoracic (T1-T12) and upper lumbar (L1-L3) spinal cord -Preganglionic neurons axons exit spinal cord in the ventral nerve roots -At the point where the ventral and dorsal nerve roots meet to form the spinal the nerve the sympathetic axons exit via the white ramus and enter the paravertebral sympathetic ganglia
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Paravertebral ganglia
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Form an interconnected chain located on either side of the vertebral column Ganglia extend above and below the thoracic and lumbar levels to provide postganglionic sympathetic axons to cervical and lumbosacral spinal nerves
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Cervical Sympathetic Ganglia
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Preganglionic axons arise from T1 to T5 3 major ganglia: superior, middle, inferior
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Lumbosacral Sympathetic Ganglia
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Preganglionic axons descend below L3 to form 2 additional lumbar and at least 4 sacral ganglia
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T/F: Sympathetic System is Widely Activated in the Fight-or-Flight Response?
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T
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T/F: PNS neurons are activated in a localized fashion?
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T (1 presynaptic PNS for every 1-20 post-synaptic neurons…Ganglia in parasympathetic division are located close to organ innervated or within its walls)
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PNS neurons are located in 2 regions
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-*Cranial portion* (emanating from brainstem) -*Sacral portion* (originating in the intermediate gray zone of sacral spinal cord
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T/F: SNS neurons are activated in a localized fashion
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F (1 presynaptic SNS neuron for every 100 post-synaptic neurons)
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Sacral PNS neurons innervate…
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-Neurons from S2-S4 segments synapse in ganglia in or near pelvic organs -Structures: Lower GI tract Urinary Bladder Reproductive Organs
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Bainstem PNS neurons innervate…
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-structures in the head, chest, and abdomen -CN: III, VII, IX, X