Podcast
Questions and Answers
Which division of the peripheral nervous system is responsible for transmitting signals from the body to the central nervous system?
Which division of the peripheral nervous system is responsible for transmitting signals from the body to the central nervous system?
Which neurotransmitter is primarily associated with the cholinergic neurons?
Which neurotransmitter is primarily associated with the cholinergic neurons?
What are the primary receptors that respond to adrenergic neurotransmitters?
What are the primary receptors that respond to adrenergic neurotransmitters?
Which of the following best differentiates the autonomic and somatic nervous systems?
Which of the following best differentiates the autonomic and somatic nervous systems?
Signup and view all the answers
Which type of cholinergic receptor is primarily located at the neuromuscular junction?
Which type of cholinergic receptor is primarily located at the neuromuscular junction?
Signup and view all the answers
What is the primary effect of acetylcholine on the heart?
What is the primary effect of acetylcholine on the heart?
Signup and view all the answers
Which of the following describes the action of α2 receptors?
Which of the following describes the action of α2 receptors?
Signup and view all the answers
What role does acetylcholinesterase play in the degradation of acetylcholine?
What role does acetylcholinesterase play in the degradation of acetylcholine?
Signup and view all the answers
Which subtype of β-adrenoceptors is primarily associated with cardiac stimulation?
Which subtype of β-adrenoceptors is primarily associated with cardiac stimulation?
Signup and view all the answers
Which action is primarily mediated by β2 receptors?
Which action is primarily mediated by β2 receptors?
Signup and view all the answers
What is the primary effect of acetylcholine on the urinary system?
What is the primary effect of acetylcholine on the urinary system?
Signup and view all the answers
What triggers the release of calcium from the endoplasmic reticulum in response to α1 receptor activation?
What triggers the release of calcium from the endoplasmic reticulum in response to α1 receptor activation?
Signup and view all the answers
What is the consequence of presynaptic α2 receptor activation on norepinephrine release?
What is the consequence of presynaptic α2 receptor activation on norepinephrine release?
Signup and view all the answers
Which neurotransmitter is primarily released during sympathetic nervous system activation?
Which neurotransmitter is primarily released during sympathetic nervous system activation?
Signup and view all the answers
Which mechanism primarily mediates the effects of α1 receptors?
Which mechanism primarily mediates the effects of α1 receptors?
Signup and view all the answers
What do cholinergic nerve fibers primarily release?
What do cholinergic nerve fibers primarily release?
Signup and view all the answers
Which neurotransmitter is associated with adrenergic nerve fibers?
Which neurotransmitter is associated with adrenergic nerve fibers?
Signup and view all the answers
What differentiates the parasympathetic nervous system’s action potential response from the sympathetic system?
What differentiates the parasympathetic nervous system’s action potential response from the sympathetic system?
Signup and view all the answers
Which receptors do acetylcholine bind to in parasympathetic postganglionic neurons?
Which receptors do acetylcholine bind to in parasympathetic postganglionic neurons?
Signup and view all the answers
Which neurotransmitter is classified as the main excitatory neurotransmitter in the central nervous system?
Which neurotransmitter is classified as the main excitatory neurotransmitter in the central nervous system?
Signup and view all the answers
Which neurotransmitter pair is correctly matched with its associated receptor?
Which neurotransmitter pair is correctly matched with its associated receptor?
Signup and view all the answers
What characterizes neurotransmitter release during an action potential?
What characterizes neurotransmitter release during an action potential?
Signup and view all the answers
Which type of neurotransmitter interaction occurs when acetylcholine binds to nicotinic receptors?
Which type of neurotransmitter interaction occurs when acetylcholine binds to nicotinic receptors?
Signup and view all the answers
What primary function do local mediators serve in cellular signaling?
What primary function do local mediators serve in cellular signaling?
Signup and view all the answers
Which neurotransmitter is known as the major inhibitory neurotransmitter in the central nervous system?
Which neurotransmitter is known as the major inhibitory neurotransmitter in the central nervous system?
Signup and view all the answers
What is the primary function of the afferent division of the peripheral nervous system?
What is the primary function of the afferent division of the peripheral nervous system?
Signup and view all the answers
Which component of the autonomic nervous system is primarily responsible for the 'fight or flight' response?
Which component of the autonomic nervous system is primarily responsible for the 'fight or flight' response?
Signup and view all the answers
In the anatomy of efferent neurons, where do the preganglionic neurons originate?
In the anatomy of efferent neurons, where do the preganglionic neurons originate?
Signup and view all the answers
Which neurotransmitter is primarily associated with cholinergic neurons?
Which neurotransmitter is primarily associated with cholinergic neurons?
Signup and view all the answers
Which aspect correctly describes the somatic nervous system (SNS)?
Which aspect correctly describes the somatic nervous system (SNS)?
Signup and view all the answers
What is a key characteristic of the autonomic nervous system?
What is a key characteristic of the autonomic nervous system?
Signup and view all the answers
Which of the following best describes postganglionic neurons in the autonomic nervous system?
Which of the following best describes postganglionic neurons in the autonomic nervous system?
Signup and view all the answers
Which functions are primarily associated with the parasympathetic nervous system?
Which functions are primarily associated with the parasympathetic nervous system?
Signup and view all the answers
Where do sympathetic preganglionic neurons typically originate from?
Where do sympathetic preganglionic neurons typically originate from?
Signup and view all the answers
What is the role of ganglia in the peripheral nervous system?
What is the role of ganglia in the peripheral nervous system?
Signup and view all the answers
What is the effect of alpha-1 adrenergic receptor stimulation on urine retention?
What is the effect of alpha-1 adrenergic receptor stimulation on urine retention?
Signup and view all the answers
Which action is a result of beta-2 adrenergic receptor stimulation?
Which action is a result of beta-2 adrenergic receptor stimulation?
Signup and view all the answers
What is the primary action of sympatholytics?
What is the primary action of sympatholytics?
Signup and view all the answers
How do indirect-acting agonists function in adrenergic drug actions?
How do indirect-acting agonists function in adrenergic drug actions?
Signup and view all the answers
What effect does alpha-2 receptor stimulation have on norepinephrine release?
What effect does alpha-2 receptor stimulation have on norepinephrine release?
Signup and view all the answers
Which of the following describes the action of direct-acting agonists?
Which of the following describes the action of direct-acting agonists?
Signup and view all the answers
What is the primary adrenergic effect of beta-1 receptor stimulation?
What is the primary adrenergic effect of beta-1 receptor stimulation?
Signup and view all the answers
What mechanism do sympathomimetics utilize?
What mechanism do sympathomimetics utilize?
Signup and view all the answers
Study Notes
Nervous System Organization and Divisions
- The Nervous System is made up of the Central Nervous System (CNS), the Peripheral Nervous System (PNS)
- The CNS consists of the brain and spinal cord.
- The PNS has two divisions: Afferent and Efferent
- Afferent - Sends sensory signals TO the CNS; includes visceral stimuli (from internal organs & mucosal surfaces) and sensory stimuli (from external sources)
- Efferent - Sends signals FROM the CNS to the effector organs; includes somatic nervous system (SNS) and Autonomic Nervous System (ANS)
Anatomy of Afferent Neurons
- Afferent neurons include sensory receptors, fibers, and are important for reflexes and signaling the CNS about the need for an efferent response.
Functional Division of Efferent PNS
- Somatic Nervous System (SNS) - Conscious, voluntary, controlled function; uses cholinergic motor neurons to innervate skeletal muscle
- Autonomic Nervous System (ANS) - Unconscious, involuntary, regulatory function; uses cholinergic & adrenergic neurons to innervate various organs
Anatomy of Efferent Neurons (somatic and autonomic)
- Preganglionic neurons: Originate in CNS, emerge from brainstem/spinal cord, form synapses in ganglia, and are myelinated (fast transmission).
- Postganglionic neurons: Cell body begins in ganglia, ends on effector organ, and is nonmyelinated.
- Ganglia: Neural clusters that act as relay stations for signals; can transmit, redirect, or diffuse signals.
Somatic Nervous System (SNS)
- Directly connects the CNS to skeletal muscle.
- No ganglia.
- Myelinated for fast transmission.
Autonomic Nervous System (ANS)
- Sympathetic (Fight or Flight): Increases energy; releases epinephrine from adrenal medulla (works as a unit, discharges as a complete system).
- Parasympathetic (Rest and Digest): Maintains homeostasis & essential bodily functions; opposes sympathetic actions; innervates specific organs and activates targets separately.
- Enteric: Controls digestive organs; covered in greater detail in GI lectures.
Anatomy of Sympathetic and Parasympathetic Neurons
- Sympathetic: Most originate from thoracic and lumbar regions of spinal cord; preganglionic neurons are shorter than postganglionic neurons; ganglia are closer to CNS.
- Parasympathetic: Originate from cranial nerves III, VII, IX, X and sacral spinal cord (S2-S4); preganglionic neurons are longer than postganglionic neurons; ganglia are closer to effector organs.
Function of Sympathetic Nervous System (SANS)
- Fight or Flight response activated by direct sympathetic stimulation and adrenal medulla stimulation.
- Releases epinephrine.
- Functions as a unit; discharges as a complete system.
Function of Parasympathetic Nervous System (PANS)
- Maintains homeostasis and essential bodily functions.
- Opposes or balances actions of the sympathetic system.
- Never discharges as a complete system.
- Innervates specific organs; activates targets separately.
Neurotransmitters and Signal Transduction
- Signals are sent from CNS to effector organs via neurotransmitters released from nerve terminals.
- Neurotransmitters are responsible for communication neuron-to-neuron and neuron-to-effector organ.
- Other signal types:
- Hormones: Released by endocrine cells into bloodstream.
- Local mediators: Act locally on surrounding cells; rapidly degraded and removed (e.g., prostaglandins).
Neurotransmitters (NTMs)
- Action Potential (AP) leads to NTM release.
- AP arrives at axon terminal, depolarization occurs, voltage-gated Ca2+ channels open, Ca2+ enters, signals vesicles to move to membrane.
- Vesicles merge with membrane releasing NTM into synapse.
- NTM diffuses, binds to postsynaptic neuron receptors.
- Triggers a response, which may trigger another action potential.
Common Neurotransmitters
- Cholinergic: Acetylcholine (ACh)
- Adrenergic (NE): Norepinephrine (NE)
- Dopaminergic: Dopamine (DA)
- Serotonergic: Serotonin (5-HT)
- GABAergic: Gamma-aminobutyric acid (GABA)
- Glutamatergic: Glutamate (Glu)
- Opioid: Endorphins
Major Neurotransmitters
- Glutamate: Major excitatory NTM
- GABA: Major inhibitory NTM
- They balance each other; an imbalance can lead to disease.
Some Neurotransmitter/Receptor Pairs
- Epinephrine, Norepinephrine (NE): α & β adrenergic receptors
- Dopamine (DA): D receptors
- Serotonin (5-HT): 5-HT receptors
- GABA: GABA receptor (NMDA, AMPA)
- Acetylcholine (ACh): Nicotinic & muscarinic cholinergic receptors
- Glutamate (Glu): NMDA, AMPA, mGluR receptors
- Endorphins: Opioid receptors
Neurotransmitter Synthesis
- Notice the enzymes involved.
- Enzymes are good drug targets.
Cholinergic Nerve Fibers
- Neurons that release Acetylcholine (ACh)
- All somatic motor neurons release ACh, which binds to nicotinic receptors on skeletal muscle cells.
- All preganglionic autonomic neurons (sympathetic & parasympathetic) release ACh, which binds to nicotinic receptors.
- Parasympathetic postganglionic neurons release ACh, which binds to muscarinic receptors.
- Direct release of ACh onto adrenal medulla, which binds to nicotinic receptors on adrenal medulla.
Adrenergic Nerve Fibers
- Release Norepinephrine (NE) from sympathetic postganglionic neurons to adrenergic receptors on effector organs.
- The adrenal medulla releases epinephrine into the bloodstream.
- Epinephrine acts as a chemical messenger in effector organs (sometimes acts as neurotransmitter, but mostly as a hormone).
Cholinergic Receptors
- Nicotinic Receptors: Located on presynaptic receptors of cholinergic neurons (negative feedback mechanism), and on other presynaptic receptors.
Actions of Acetylcholine (Parasympathetic Actions)
- Decreases heart rate, cardiac output, blood pressure.
- Stimulates salivary secretion.
- Increases gastric acid secretion.
- Stimulates intestinal secretions and motility.
- Increases bronchiolar secretions.
- Causes bronchoconstriction.
- Increases detrusor muscle tone (causes urination).
- Stimulates ciliary muscle contraction for near vision.
- Constricts pupillary sphincter muscle (miosis).
Degradation of Acetylcholine (ACh)
- Signal is rapidly terminated at the postjunctional effector site.
- Acetylcholinesterase (AChE) breaks down ACh into choline and acetate in the synaptic cleft.
Adrenergic Receptors
- Two subtypes based on affinities for α agonists and antagonists:
- α1 Receptors: Primarily on postsynaptic membranes of effector organs; mediate smooth muscle constriction.
- α2 Receptors: Primarily on sympathetic presynaptic nerve endings; control release of NE.
Alpha-1 Receptors
- Found on postsynaptic membranes of effector organs.
- Mediate many of the classic effects involving smooth muscle constriction.
- Activate G-protein pathway, leading to:
- Phospholipase C activation
- Generation of second messengers DAG and IP3
- IP3 triggers release of calcium from ER into cytosol.
- DAG activates other proteins in the cell.
Alpha-2 Receptors
- Located on sympathetic presynaptic nerve endings.
- Control NE release.
- Most released NE activates the sympathetic adrenergic postsynaptic neuron, but some circles back to α2 receptors on the presynaptic membrane.
- Presynaptic receptor stimulation leads to feedback inhibition and blocks further NE release.
- This acts as local regulation for NE output during high sympathetic activity.
Beta-Adrenoreceptors
- Strong response to isoproterenol.
- Three subgroups based on affinities for adrenergic agonists and antagonists:
- β1: Heart
- β2: Lungs
- β3: Adipose tissue
- β1 equal affinity for epinephrine and NE.
- β2 higher affinity for epinephrine than NE.
- Binding activates adenylyl cyclase and increases cAMP concentrations inside the effector cell.
Locations of Alpha and Beta Receptors
- α1: Vessels, smooth muscle, iris sphincter.
- α2: Presynaptic nerve endings, platelets, pancreatic beta cells (some on postsynaptic organs).
- β1: Heart, kidneys, adipose tissue.
- β2: Lungs, skeletal muscle, blood vessels in skeletal muscle, liver, uterus, pancreatic beta cells.
Characteristic Responses Mediated by Adrenoreceptors
- α1 stimulation: Vasoconstriction and increased total peripheral resistance and blood pressure.
- β1 stimulation: Cardiac stimulation.
- β2 stimulation: Vasodilation and smooth muscle relaxation.
Summary Table of Adrenoreceptors in ANS
| Adrenergic Receptor | Location | Effector Response |
|---|---|---|
| α1 | Vessels, smooth muscle, iris sphincter | Vasoconstriction, contraction of smooth muscle |
| α2 | Presynaptic nerve endings, platelets, pancreatic β cells | Inhibition of NE release, decreased sympathetic outflow |
| β1 | Heart, kidneys, adipose tissue | Increased HR, contractility, renin secretion |
| β2 | Lungs, skeletal muscle, blood vessels in skeletal muscle | Bronchodilation, vasodilation, relaxation of smooth muscle |
Adrenergic Drug Actions
- Affect receptors stimulated by NE or epinephrine.
-
Sympathomimetics: Activate adrenergic receptors.
- Direct acting agonists: Directly activate adrenergic receptors.
- Indirect-acting agonists: Enhance release or stop reuptake of NE.
- Sympatholytics: Block activation of adrenergic receptors.
Summary Review Table - Adrenergic Receptors and Drug Actions
| Adrenergic Receptor | Effect when Stimulated | Actions of Receptor Agonist | Actions of Receptor Antagonist |
|---|---|---|---|
| α1 | Vasoconstriction; contraction of urinary sphincter | vasoconstriction | vasodilation |
| α2 | Presynaptic: Decreases NE release; Postsynaptic: Decreases sympathetic outflow | Decreases NE release, decreased sympathetic outflow | Increases NE release |
| β1 | Increases HR, contractility, renin secretion | Increases HR, contractility, renin secretion | Decreases HR, contractility, renin secretion |
| β2 | Bronchodilation; arteriole dilation (except skin and brain) | Bronchodilation, vasodilation | Bronchoconstriction, vasoconstriction |
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
Explore the divisions of the Nervous System, including the Central and Peripheral Nervous Systems. This quiz will cover the roles of Afferent and Efferent neurons, as well as the functions of the Somatic and Autonomic Nervous Systems. Test your knowledge on the anatomy and functionality of the nervous system components.
