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What regions of the body are associated with the sympathetic nervous system?
What regions of the body are associated with the sympathetic nervous system?
Which term describes the system associated with the parasympathetic nervous system?
Which term describes the system associated with the parasympathetic nervous system?
What is the role of the first neuron (preganglionic neuron) in the autonomic nervous system?
What is the role of the first neuron (preganglionic neuron) in the autonomic nervous system?
How does sympathetic nervous system activation affect organ systems?
How does sympathetic nervous system activation affect organ systems?
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Where are the cell bodies of the second neuron (postganglionic neuron) located?
Where are the cell bodies of the second neuron (postganglionic neuron) located?
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What is the main function of the autonomic nervous system?
What is the main function of the autonomic nervous system?
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What are the two branches of the autonomic nervous system?
What are the two branches of the autonomic nervous system?
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Which statement about the Sympathetic nervous system is true?
Which statement about the Sympathetic nervous system is true?
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What effect does the Parasympathetic nervous system have on heart rate?
What effect does the Parasympathetic nervous system have on heart rate?
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How does the diameter of bronchioles change under the influence of the Sympathetic nervous system?
How does the diameter of bronchioles change under the influence of the Sympathetic nervous system?
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What happens to GI motility when the Sympathetic nervous system is activated?
What happens to GI motility when the Sympathetic nervous system is activated?
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Which body function is generally considered less important during a fight-or-flight response stimulated by the Sympathetic nervous system?
Which body function is generally considered less important during a fight-or-flight response stimulated by the Sympathetic nervous system?
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Which neurotransmitter is associated with the activation of the Parasympathetic nervous system?
Which neurotransmitter is associated with the activation of the Parasympathetic nervous system?
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What is the primary neurotransmitter released by postganglionic neurons in the sympathetic nervous system?
What is the primary neurotransmitter released by postganglionic neurons in the sympathetic nervous system?
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What type of receptors are alpha1 adrenergic receptors primarily associated with?
What type of receptors are alpha1 adrenergic receptors primarily associated with?
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Which receptor type is primarily found on target organs and tissues supplied by postganglionic neurons of the parasympathetic nervous system?
Which receptor type is primarily found on target organs and tissues supplied by postganglionic neurons of the parasympathetic nervous system?
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Where do preganglionic neurons of the parasympathetic nervous system originate?
Where do preganglionic neurons of the parasympathetic nervous system originate?
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Which neurotransmitter is released from the adrenal medulla into the bloodstream?
Which neurotransmitter is released from the adrenal medulla into the bloodstream?
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What happens when norepinephrine binds to beta1 adrenergic receptors?
What happens when norepinephrine binds to beta1 adrenergic receptors?
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Which drug type mimics the effects of catecholamines?
Which drug type mimics the effects of catecholamines?
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What characterizes cholinergic neurons in the autonomic nervous system?
What characterizes cholinergic neurons in the autonomic nervous system?
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What effect do muscarinic receptors have when activated by acetylcholine?
What effect do muscarinic receptors have when activated by acetylcholine?
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What identifies postganglionic sympathetic neurons?
What identifies postganglionic sympathetic neurons?
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Which of the following receptors inhibits the activity of the parasympathetic nervous system?
Which of the following receptors inhibits the activity of the parasympathetic nervous system?
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Which type of receptor is found between motor neurons and muscle in the somatic nervous system?
Which type of receptor is found between motor neurons and muscle in the somatic nervous system?
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What is a common therapeutic use of sympathomimetics in emergencies?
What is a common therapeutic use of sympathomimetics in emergencies?
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Study Notes
The Autonomic Nervous System
- The autonomic nervous system controls subconscious bodily functions.
- It's divided into two branches: sympathetic and parasympathetic.
Sympathetic Nervous System
- Also known as "fight-or-flight"
- Associated with survival in emergency situations
- Responsible for energy expenditure.
- Causes an increase in heart rate, force of heart contraction, and dilation of bronchioles and pupils.
- Decreases GI motility and function.
- Increases blood flow to muscles.
- Decreases blood flow to other organs.
Parasympathetic Nervous System
- Also known as "rest-and-digest" or "rest-and-restore."
- Associated with processes that occur in the normal resting state.
- Responsible for energy conservation.
- Causes decreased heart rate, force of heart contraction and constriction of bronchioles and pupils.
- Increases in GI motility and function.
Structure of the Autonomic Nervous System
- Sympathetic nervous system: arises from thoracic and lumbar regions of the spinal cord, often referred to as the thoracolumbar system.
- Parasympathetic nervous system: arises from the brain and sacral region of the spinal cord, often referred to as the craniosacral system.
- The autonomic nervous system involves two neurons:
- First neuron (preganglionic): originates in the central nervous system (CNS) and extends to a cluster of nerve cells called an autonomic ganglion.
- Second neuron (postganglionic): nerve cell bodies located in the autonomic ganglion. Its axon connects to the target organ (muscle or gland).
Neurotransmitters
-
Sympathetic:
- Primary neurotransmitter is norepinephrine.
- Related neurotransmitters are norepinephrine, epinephrine (adrenaline), and dopamine.
- Neurons that release norepinephrine are called adrenergic.
- Norepinephrine/epinephrine is released into bloodstream directly from the adrenal medulla.
-
Parasympathetic:
- Acetylcholine is the primary neurotransmitter.
- Neurons that release acetylcholine are referred to as cholinergic neurons.
- All preganglionic neurons are cholinergic. The postganglionic neuron determines if the effect is sympathetic or parasympathetic.
Receptors involved (examples)
-
Sympathetic:
- Alpha 1, 2 adrenergic receptors, Beta 1, 2 adrenergic receptors
-
Parasympathetic:
- Nicotinic, Muscarinic cholinergic receptors
-
Alpha 1 adrenergic: cause vasoconstriction in certain blood vessels.
-
Beta 1 adrenergic: increases heart rate and force of contraction
-
Beta 2 adrenergic: causes bronchodilation (opening of bronchioles)
-
Nicotinic receptors in sympathetic/parasympathetic: Found on the second neuron (postganglionic) in both systems, but also found in the somatic (voluntary) system between motor neurons and muscle.
-
Muscarinic receptors in parasympathetic: Found on target organs and tissues supplied by postganglionic neurons of the parasympathetic nervous system (PSNS).
Summary of impulses in the Autonomic Nervous System
- Presynaptic neurons extend to autonomic ganglia.
- Presynaptic neurons release acetylcholine into the synaptic cleft.
- Acetylcholine binds to nicotinic ganglionic receptors on postganglionic neurons.
- Postsynaptic neurons transmit impulses to the end organs, releasing either norepinephrine (sympathetic) or acetylcholine (parasympathetic).
Drugs affecting the Autonomic Nervous System
- Some drugs enhance neurotransmission (receptor agonists).
- Some drugs induce neurotransmitter release.
- Some drugs prevent neurotransmitter breakdown.
- Other drugs suppress neurotransmission (presynaptic blockers, receptor antagonists, ganglion blockers).
Clinical Relevance of the Autonomic Nervous System
- Clinical conditions—Epinephrine (adrenaline) is used to treat conditions like anaphylaxis, cardiac arrest or shock
- Treatments—Atropine is to treat conditions like bradycardia or respiratory distress, and blocks "rest and digest."
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Description
Explore the intricacies of the autonomic nervous system, including its two main branches: sympathetic and parasympathetic. Understand their functions, effects on the body, and how they help maintain homeostasis during different situations, from emergencies to restful states.
