THE AUTONOMIC NERVOUS SYSTEM (ANS). What is the autonomic nervous system? The autonomic nervous...
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Transcript of THE AUTONOMIC NERVOUS SYSTEM (ANS). What is the autonomic nervous system? The autonomic nervous...
THE AUTONOMIC THE AUTONOMIC NERVOUS SYSTEM NERVOUS SYSTEM
(ANS)(ANS)
What is the autonomic What is the autonomic nervous system?nervous system?
The autonomic nervous system The autonomic nervous system (ANS) is the motor division of the (ANS) is the motor division of the
peripheral nervous system that peripheral nervous system that controls visceral activities, with the controls visceral activities, with the
goal of maintaining internal goal of maintaining internal homeostasis.homeostasis.
What does the autonomic What does the autonomic nervous system do?nervous system do?
It provides motor fibers to smooth and cardiac It provides motor fibers to smooth and cardiac muscles and glandsmuscles and glands
It operates subconsciouslyIt operates subconsciously It causes excitation and inhibitionIt causes excitation and inhibition It makes adjustments to support body activitiesIt makes adjustments to support body activities It has an efferent pathway made up of a two-It has an efferent pathway made up of a two-
neuron chain: preganglionic and ganglionicneuron chain: preganglionic and ganglionic
Two divisions of the ANSTwo divisions of the ANS
1) Parasympathetic division1) Parasympathetic division
2) Sympathetic2) Sympathetic
Although they have different roles, they Although they have different roles, they have effects on many of the same organs of have effects on many of the same organs of the bodythe body
Organs affected by both divisionsOrgans affected by both divisions
Roles of the two different Roles of the two different divisionsdivisions
1. 1. The parasympathetic division…The parasympathetic division…
_conserves body energy and maintains body _conserves body energy and maintains body activities at basal levelsactivities at basal levels
_is involved in digestion, diuresis, and _is involved in digestion, diuresis, and defecationdefecation
_causes heart rate and blood pressure to be _causes heart rate and blood pressure to be low, the skin to be warm and the pupils to low, the skin to be warm and the pupils to be constrictedbe constricted
2. 2. The sympathetic division…The sympathetic division…
_activates the body under conditions of emergency _activates the body under conditions of emergency which is why it is often called the “fight or flight which is why it is often called the “fight or flight system”system”
_is involved in emergency, exercise, and excitement_is involved in emergency, exercise, and excitement
_causes blood flow to organs to reduce and blood flow _causes blood flow to organs to reduce and blood flow to muscles to increaseto muscles to increase
_also causes skin to be cold, heart rate to increase, and _also causes skin to be cold, heart rate to increase, and rapid breathingrapid breathing
Parasympathetic division Parasympathetic division outflowoutflow
Neurons of the cranial and sacral Neurons of the cranial and sacral outflows of the parasympathetic outflows of the parasympathetic
division are located in the following division are located in the following nerves and create an effect on the nerves and create an effect on the
organs mentioned in the table below.organs mentioned in the table below.
Table of parasympathetic outflowTable of parasympathetic outflow
Cranial OutflowCranial Outflow Cranial NerveCranial Nerve Effector Organ(s)Effector Organ(s)
Occulomotor (III)Occulomotor (III) EyeEye
Facial (VII)Facial (VII) Salivary, nasal, and Salivary, nasal, and lacrimal glandslacrimal glands
Glosso-pharyngeal Glosso-pharyngeal (IX)(IX)
Parotid salivary glandsParotid salivary glands
Vagus (X)Vagus (X) Heart, lungs, and most Heart, lungs, and most visceral organsvisceral organs
Sacral OutflowSacral Outflow SS22-S-S44Large intestine, urinary Large intestine, urinary bladder, ureters, and bladder, ureters, and reproductive organsreproductive organs
Parasympathetic division outflowParasympathetic division outflow
Sympathetic division Sympathetic division outflowoutflow
Sympathetic division outflow is different from parasympathetic Sympathetic division outflow is different from parasympathetic division outflow because…division outflow because…
It arises from spinal cord segments TIt arises from spinal cord segments T11 through L through L22 Preganglionic fibers pass through the white rami Preganglionic fibers pass through the white rami
communicantes and synapse in the chain (paravertebral) communicantes and synapse in the chain (paravertebral) gangliaganglia
Fibers from TFibers from T55-L-L22 form splanchnic nerves and synapse with form splanchnic nerves and synapse with collateral ganglia collateral ganglia
Postganglionic fibers innervate the numerous organs of the Postganglionic fibers innervate the numerous organs of the bodybody
Sympathetic neurons produce the lateral horns of the spinal Sympathetic neurons produce the lateral horns of the spinal cordcord
Sympathetic division outflowSympathetic division outflow
ANS PhysiologyANS PhysiologyNeurotransmitters and Neurotransmitters and
ReceptorsReceptors The two major neurotransmitter involved in the ANS are:The two major neurotransmitter involved in the ANS are:
Acetylcholine (ACh)Acetylcholine (ACh)Norepinephrine (NE)Norepinephrine (NE)
ACh is the same neurotransmitter that is found in the somatic ACh is the same neurotransmitter that is found in the somatic motor neurons and is released in the ANS:motor neurons and is released in the ANS:
All ANS preganglionic axonsAll ANS preganglionic axonsAll parasympathetic postganglionic axons at synapses All parasympathetic postganglionic axons at synapses
with their effectorswith their effectors ACh releasing fibers are called Cholinergic FibersACh releasing fibers are called Cholinergic Fibers NE is released by most sympathetic postganglionic axonsNE is released by most sympathetic postganglionic axons NE releasing fibers are called Adrenergic FibersNE releasing fibers are called Adrenergic Fibers The effects of ACh and NE are either excitation or inhibition The effects of ACh and NE are either excitation or inhibition
which is dependant on the receptor type allowing them to exert which is dependant on the receptor type allowing them to exert these different effects at different areas in the bodythese different effects at different areas in the body
ReceptorsReceptors ACh binds to two types of receptors:ACh binds to two types of receptors:
NicotinicNicotinicMuscarineMuscarine
Nicotinic Receptors are located on:Nicotinic Receptors are located on:Motor end plates of skeletal muscles (somatic targets)Motor end plates of skeletal muscles (somatic targets)All ganglionic neurons (sypathetic and All ganglionic neurons (sypathetic and
parasympathetic)parasympathetic)The hormone-producing cells of the adrenal medullaThe hormone-producing cells of the adrenal medulla
ACh always produces a stimulatory effect when it binds with ACh always produces a stimulatory effect when it binds with nicotinic receptorsnicotinic receptors
Muscarine Receptors occur on all effector cells stimulated by Muscarine Receptors occur on all effector cells stimulated by postganglionic cholinergic fibers (parasympathetic targets like postganglionic cholinergic fibers (parasympathetic targets like the eccrine sweat glands and some blood vessels of skeletal the eccrine sweat glands and some blood vessels of skeletal muscle)muscle)
ACh binding produces a inhibitory or excitatory depending on ACh binding produces a inhibitory or excitatory depending on the receptor type of the target organ the receptor type of the target organ
ReceptorsReceptors There are also receptors know as Adrenergic There are also receptors know as Adrenergic
Receptors (two types):Receptors (two types): Alpha with two subtypes (A1,A2)Alpha with two subtypes (A1,A2) Beta with three subtypes (B1,B2,B3)Beta with three subtypes (B1,B2,B3)
The general effects of NE binding are:The general effects of NE binding are: Alpha receptors are mostly stimulatoryAlpha receptors are mostly stimulatory Beta receptors are mostly inhibitoryBeta receptors are mostly inhibitory
However, an exception to this is when NE binds to However, an exception to this is when NE binds to the Beta receptors of cardiac muscle and the result is the Beta receptors of cardiac muscle and the result is stimulatory stimulatory
Overview of the location and Overview of the location and effects of receptor subclasseseffects of receptor subclasses
Drugs and the ANSDrugs and the ANS
Knowing the locations of the cholinergic and adrenergic Knowing the locations of the cholinergic and adrenergic receptors subtypes allows specific drugs to be prescribed receptors subtypes allows specific drugs to be prescribed to obtain the desired inhibitory or stimulatory effect on to obtain the desired inhibitory or stimulatory effect on selected organsselected organs
An example of this is Atropine (blocks parasympathetic An example of this is Atropine (blocks parasympathetic effects):effects):
administered during surgery to prevent salivation administered during surgery to prevent salivation and dry up respiratory secretionsand dry up respiratory secretions
Ophthalmologists use it to dilate the pupils for an Ophthalmologists use it to dilate the pupils for an eye exameye exam
There are several examples of drugs in Table 14.4 that There are several examples of drugs in Table 14.4 that influence the Activity of the ANS on page 544influence the Activity of the ANS on page 544
Interactions of the Autonomic Interactions of the Autonomic DivisionsDivisions
Most visceral organs receive innervation by both Most visceral organs receive innervation by both sympathetic and parasympathtic fiberssympathetic and parasympathtic fibers
This dual innervation produces a dynamic This dual innervation produces a dynamic antagonism that allows visceral activity to be antagonism that allows visceral activity to be precisely controlledprecisely controlled
Sympathetic fibers increase heart and respiratory Sympathetic fibers increase heart and respiratory rates. They also inhibit digestion and eliminationrates. They also inhibit digestion and elimination
Parasympathetic fibers allow for digestion and Parasympathetic fibers allow for digestion and elimination and decrease respiratory and heart rates elimination and decrease respiratory and heart rates
Parasympathetic & Parasympathetic & SympatheticSympathetic
The parasympathetic division is know as the “resting and The parasympathetic division is know as the “resting and digesting” divisiondigesting” division
The sympathetic division controls blood pressure and The sympathetic division controls blood pressure and keeps the blood vessels in a continual state of partial keeps the blood vessels in a continual state of partial constrictionconstriction
Flight or Fright response – the sympathetic can override Flight or Fright response – the sympathetic can override the parasympathetic in an emergency to increase heart the parasympathetic in an emergency to increase heart and respiratory rates while inhibiting digestion.and respiratory rates while inhibiting digestion.
Parasympathetic division restores the heart and Parasympathetic division restores the heart and respiratory rates back to resting levels when the respiratory rates back to resting levels when the emergency is over and then returns back to it’s functions emergency is over and then returns back to it’s functions of digestion and eliminationof digestion and elimination
Sympathetic ToneSympathetic Tone& Parasympathetic Tone& Parasympathetic Tone
The Sympathetic Tone:The Sympathetic Tone: Constricts blood vessels & controls blood pressure to rise Constricts blood vessels & controls blood pressure to rise
in response to the body’s needsin response to the body’s needs Prompts vessels to dilate if blood pressure needs to be Prompts vessels to dilate if blood pressure needs to be
decreaseddecreased
The Parasympathetic Tone:The Parasympathetic Tone: Slows the heartSlows the heart Controls Digestion and EliminationControls Digestion and Elimination
ANS control is best seen in the external ANS control is best seen in the external genitalia:genitalia:
Parasympathetic fibers cause vasodilation resulting in Parasympathetic fibers cause vasodilation resulting in the erection of the penis and clitoristhe erection of the penis and clitoris
Sympathetic fibers cause ejaculation of sperm and reflex Sympathetic fibers cause ejaculation of sperm and reflex peristalsis in femalesperistalsis in females
Sympathetic DivisionSympathetic Division
The adrenal medulla, sweat glands and the The adrenal medulla, sweat glands and the arrector pili muscles of the skin, the kidneys, and arrector pili muscles of the skin, the kidneys, and most blood vessels receive only sympathetic most blood vessels receive only sympathetic fibers.fibers.
The Sympathetic Division controls:The Sympathetic Division controls:Thermoregulatory Responses to heatThermoregulatory Responses to heatRelease of Renin from the kidneysRelease of Renin from the kidneysMetabolic Effects Metabolic Effects
Control of Autonomic Control of Autonomic FunctionsFunctions
Autonomic functions are controlled by several factors:Autonomic functions are controlled by several factors:1.1. Reflex Activities mediated by the Spinal Cord and Reflex Activities mediated by the Spinal Cord and
Brain Stem (Medullary Center)Brain Stem (Medullary Center)2.2. Hypothalamic integration centers interact with both Hypothalamic integration centers interact with both
higher and lower centers of autonomic, somatic, higher and lower centers of autonomic, somatic, and endocrine responseand endocrine response
3.3. Cortical centers influence autonomic functioning Cortical centers influence autonomic functioning via connections with the limbic system; conscious via connections with the limbic system; conscious controls are rare but maybe learned via biofeedback controls are rare but maybe learned via biofeedback trainingtraining