Autonomic Nervous System Chapter 3
Sympathetic Division of Autonomic Nervous System
Although continually active to some degree, this division of the autonomic nervous system has the property of adjusting in response to stressful situation such as trauma, fear, hypoglycemia, cold or exercise
Central Nervous System
Brain and Spinal Cord constitute this system
Neurotransmitters
Communication between nerve cells and between nerve cells and effector organs occurs through release of these specific chemical signals from the nerve terminals.
Parasympathetic Division
Division of autonomic nervous system that maintains essential bodily functions (e.g. elimination of wastes and digestive processes) and is required for life. It usually the dominant division during "rest and digest" situations. This system is not a functional entity & never discharges as a complete system. Instead, discrete fibers are activated separately & the system functions to affect specific organs.
Autonomic Drugs
Drugs that produce their primary therapeutic effect by mimicking or altering the functions of the autonomic nervous system.
In Somatic Nervous System: 1) a single myelinated motor neuron originating in CNS travels DIRECTLY to skeletal muscle w/o the mediation of ganglia 2) under voluntary control
How does the efferent somatic nervous system differ from the autonomic nervous system?
Acetylcholine
If transmission is mediated by this neurotransmitter, the neuron is called cholinergic. This neurotransmitter mediates the transmission of nerve impulses across autonomic ganglia in both sympathetic and parasympathetic nervous systems. It is the neurotransmitter at the adrenal medulla. Transmission from the autonomic postganglionic nerves to effector organs in the parasympathetic system also involves release of this neurotransmitter. In the somatic nervous system, transmission at the neuromuscular junction is also cholinergics.
Neurotransmission
In the autonomic nervous system, this is an example of the more general process of chemical signaling between cells.
Synaptic Signaling
In this type of signaling, the release of a neurotransmitter is triggered by the arrival of an action potential at the nerve ending, leading to depolarization. Uptake of calcium ensues to initiate docking of the synaptic vesicles and release of their contents. The neurotransmitters rapidly diffuse across the synaptic cleft or gap and combine with specific receptors on the postsynaptic (target) cell
Adrenal Medulla
Like the sympathetic ganglia, this structure receives preganglionic fibers from the sympathetic system. Lacking axons, when stimulated by the ganglionic neurotransmitter acetylcholine, this structure influences other organs by secreting the hormone epinephrine and norepinephrine into the blood.
Reflex Arcs
Most afferent impulses are translated into this type of responses w/o involving consciousness. Ex fall in blood pressure
Local Mediators
Most cells in the body secrete chemicals that act on cells in their immediate environment. These chemical signals are rapidly destroyed or removed; thus they don't enter the blood & aren't distributed throughout body. Histamine and prostaglandins are some examples
Dual Innervation
Most organs in the body are innervated by both divisions of the autonomic nervous system. What is this called?
Hypothalamus, medulla oblongata, and spinal cord
Name 3 Integrating centers in the CNS that respond to stimuli by sending out efferent reflex impulses via the autonomic nervous system
1) Receptors coupled to ion channels 2) Receptors coupled to adenylyl cyclase 3) Receoptors coupled to diacylglycerol and inositol trisphosphate
Name 3 mechanisms where binding of a neurotransmitter leads to a cellular effect
Adrenal Medulla, kidney, pilomotor muscles, and sweat glands
Name 4 effector organs/tissues that receive innervation ONLY from the sympathetic system, and thus do not have dual innervation. The control of blood pressure is also mainly a sympathetic activity with no participation from parasympathetic system.
heart, vena cava, aortic arch, and carotid sinuses
Name 4 places that baroreceptors are found
Baroreceptor Reflex Arc
Name this reflex arc : Afferent Info: 1) drop in blood pressure 2) reduced stretch of baroreceptors in aortic arch 3) reduced frequency of afferent impulses to medulla Efferent Reflex impulses via the autonomic nervous system cause: 1) inhibition of parasympathetic and activation of sympathetic division 2) Increased peripheral resistance and cardiac output 3) Increased Blood Pressure & tachycardia
Peripheral Nervous System
Neurons located outside the brain and spinal cord compromise this system
Afferent Neurons of the Autonomic Nervous System
Neurons that are important in reflex regulation and in the signaling of the CNS to influence the efferent branch of the autonomic nervous system to respond
Enteric Neurons
Neurons that innervate the GI tract, pancreas, and gallbladder, and that constitute the "brain of the gut."
Parasympathetic Neurons
Preganglionic neurons that arise from the cranium and from the sacral areas o the spinal cord and synapse in ganglia near or on effector organs. The preganglionic fibers are LONG, and the post ganglionic fibers are SHORT with the ganglia close to or within the organ innervated. in most instances there is a 1 to 1 connection between the preganglionic and postganglionic neurons enabling the discrete response of this division.
Hormones
Specialized endocrine cells secrete these substances into the bloodstream, where they travel throughout the body exerting effects on broadly distributed target cells in the body.
SYMPATHETIC DIVISION OF AUTONOMIC NERVOUS SYSTEM
Stimulation of which division of the autonomic nervous system has the following effects: 1) increase heart rate & contractility & blood pressure 2) maintain tone of vascular beds 3) mobilize energy stores of the body 4) Increase blood flow to skeletal muscles and the heart while diverting flow from the skin and internal organs 5) Dilation of pupils and bronchioles 6) Affect GI motility and the function of the bladder and sexual organs 7) secretion of epinephrine and norepinephrine from adrenal medulla 8) secretion of renin from kidney (beta 1 increases; alpha 1 decreases) 9) thick viscous secretion from salivary glands 10) decreased muscle motility and tone of GI system; contraction of sphincters 11) Relaxation of Uterus 12) dilation of blood vessels (skeletal muscle) 13) Constriction of blood vessels (skin,mucous membranes, and splanchnic area) 14) stimulation of ejaculation 15) Relaxation of detrusor; contraction of trigone and sphincter (ureters and bladder)
Autonomic Nervous System
Stimuli that evoke feelings of strong emotion, such as rage, fear, or pleasure can modify the activity of this branch of the nervous system
Fight or Flight Stimulus
Stimulus that results in sympathetic output, which is diffuse b/c postganglionic neurons may innervate more than one organ
Preganglionic and Postganglionic Neurons
The autonomic nervous system carries nerve impulses from the CNS to the effector organs by way of these 2 types of efferent neurons
Sympathetic ,Parasympathetic, and Enteric nervous systems
The efferent autonomic nervous system is divided into these 3 subdivisions
Somatic and Autonomic subdivisions
The efferent division of the PNS is further split into these 2 subdivisions
Efferent and Afferent Divisions
The peripheral nervous system has 2 divisions. Name them.
Sympathetic Neurons
The preganglionic neurons that come from thoracic and lumbar regions of the spinal cord & they synapse in 2 cord-like chains of ganglia that run in parallel on each side of the spinal cord. The preganglionic neurons are SHORT in comparison to the post ganglionic ones. Axons of the postganglionic neuron extend from these ganglia to the tissues that they innervate and regulate.
autonomic nervous system and endocrine system
These 2 systems together coordinate the regulation and integration of bodily functions
Parasympathetic Division
These are functions of which branch of the autonomic nervous system: 1) contraction of iris sphincter muscle (pupil contracts) 2) Contraction of ciliary muscle (lens accommodates for near vision) 3) Constriction, increased secretions (Trachea and bronchioles) 4) Contraction of detrusor; relaxation of trigone and sphincter (Ureters and Bladder) 5) Stimulation of erection 6) Increased muscle motility and tone (GI system) 7) Decreased Heart Rate and decreased contractility 8) Copious watery secretion (salivary glands) 9) Stimulation of tears
Afferent Division
This division of the PNS has neurons that bring information from the periphery to the CNS, thus providing sensory input to modulate function of another division thru reflex arcs
Efferent Division
This division of the PNS has neurons that carry signals away from the brain and spinal cord to peripheral tissues
Sympathetic Nervous System
This division of the autonomic nervous system tends to function as a unit, and it often discharges as a complete system. This system with its diffuse distribution of postganglionic fibers is involved in a wide array of physiologic activities, but it is NOT essential for life
Rest and Digest Stimulus
This stimulus results in parasympathetic output, which is discrete b/c postganglionic neurons are not branched but are directed to a specific organ
Somatic Nervous System
This subdivision of the efferent division of PNS is involved in voluntary control of functions such as contraction of skeletal muscles essential for locomotion
Autonomic Nervous System
This subdivision of the efferent division of the PNS regulates the everyday needs and requirements of the vital bodily functions w/o the conscious participation of the mind, which is composed of efferent neurons that innervate smooth muscle of the viscera, cardiac muscle, vasculature, and the exocrine glands thereby controlling digestion, cardiac output, blood flow, and glandular secretions.
Nervous System
This system exerts its influence by the rapid transmission of electrical impulses over nerve fibers that terminate at effector cells, which specifically respond to the release of neuromediator substances
Enteric Nervous System
This system functions independently of the CNS and controls the motility, exocrine and endocrine secretions and microcirculation of the GI tract. It is modulated by both the sympathetic and parasympathetic nervous systems.
Autonomic Nervous System
This system is a motor system that requires sensory input from peripheral structures to provide information on the state of affairs of the body. This feedback is provided by streams of afferent impulses originating in the viscera and other innervated structures that travel to integrating centers in the CNS
Endocrine System
This system sends signals to target tissues by varying the levels of blood borne hormones
1) adenylyl cyclase system 2) calcium/phosphatidylinositol
What are the 2 most widely recognized second messengers?
Acetycholine and norepinephrine
What are the 2 primary chemical signals (neurotransmitters) in the autonomic nervous system
Norephinephrine and epinephrine
When either of these 2 neurotransmitters is the transmitter, the fiber is termed adrenergic.
Membrane Receptors
a recognition site for a substance; it has a binding specificity and it is coupled to processes that eventually evoke a response; most of these sites are actually proteins and they need not be located in the membrane
Sympathetic and Parasympathetic actions
actions that often oppose each other
Ganglia
an aggregation of nerve cell bodies located in the peripheral nervous system
Fight or Flight Response
changes experienced by body during emergencies; these reactions are triggered both by direct sympathetic activation of the effector organs, and by stimulation of the adrenal medulla to release epinephrine and lesser amounts of norepinephrine
Preganglionic Neuron
efferent neuron whose body is located in the CNS
Postganglionic Neuron
efferent neuron whose body originating in the ganglion and is generally nonmyelinated and terminates on effector organs such as smooth muscles of the viscera, cardiac muscle, and exocrine glands
Second Messenger molecules
molecules that intervene between the original message (hormone or neurotransmitter) and the ultimate effect on the cell- are part of the cascade of events that translates neurotransmitter binding into a cellular response, usually through the intervention of a G protein
Gs protein
subunit involved in the activation of adenylyl cyclase to produce cAMP
Gq protein
subunit that activates phospholipase C to release diacylglycerol and inositol triphosphates