Podcast
Questions and Answers
What type of fibers secrete acetylcholine?
What type of fibers secrete acetylcholine?
- Adrenergic fibers
- Postganglionic fibers
- Cholinergic fibers (correct)
- Preganglionic fibers
Which enzyme is responsible for the destruction of acetylcholine after its secretion?
Which enzyme is responsible for the destruction of acetylcholine after its secretion?
- Norepinephrine oxidase
- Acetylcholinesterase (correct)
- Choline acetyltransferase
- Catechol-O-methyltransferase
Where does the synthesis of norepinephrine begin?
Where does the synthesis of norepinephrine begin?
- In the synaptic cleft
- In the mitochondria of nerve endings
- In the axoplasm of terminal nerve endings (correct)
- In the secretory vesicles
How long does acetylcholine persist in the tissue after being secreted?
How long does acetylcholine persist in the tissue after being secreted?
What are the fibers that secrete norepinephrine called?
What are the fibers that secrete norepinephrine called?
What type of neuron is primarily found in the retina, olfactory mucosa, and cochlear and vestibular ganglia?
What type of neuron is primarily found in the retina, olfactory mucosa, and cochlear and vestibular ganglia?
Which of the following correctly describes the primary function of sensory neurons?
Which of the following correctly describes the primary function of sensory neurons?
What structure of a neuron is responsible for sending impulses to effector organs?
What structure of a neuron is responsible for sending impulses to effector organs?
Which type of motor nerves is under voluntary control?
Which type of motor nerves is under voluntary control?
What is the primary purpose of transmitter vesicles in the presynaptic terminal?
What is the primary purpose of transmitter vesicles in the presynaptic terminal?
What separates the presynaptic terminal from the postsynaptic neuron?
What separates the presynaptic terminal from the postsynaptic neuron?
Which type of neuron is typically associated with nerve fibers found in the spinal ganglia?
Which type of neuron is typically associated with nerve fibers found in the spinal ganglia?
What is a major part of the typical anterior motor neuron?
What is a major part of the typical anterior motor neuron?
What is the origin of the secretory cells in the adrenal medullae?
What is the origin of the secretory cells in the adrenal medullae?
Which cranial nerves are primarily involved in the parasympathetic nervous system?
Which cranial nerves are primarily involved in the parasympathetic nervous system?
Where are the postganglionic neurons of the parasympathetic nervous system typically located?
Where are the postganglionic neurons of the parasympathetic nervous system typically located?
What percentage of parasympathetic nerve fibers are found in the vagus nerves?
What percentage of parasympathetic nerve fibers are found in the vagus nerves?
What type of neurons do preganglionic sympathetic fibers connect with in the adrenal medullae?
What type of neurons do preganglionic sympathetic fibers connect with in the adrenal medullae?
Which of the following organs is NOT primarily supplied by the vagus nerve?
Which of the following organs is NOT primarily supplied by the vagus nerve?
What happens to preganglionic fibers in the parasympathetic nervous system before reaching their target organs?
What happens to preganglionic fibers in the parasympathetic nervous system before reaching their target organs?
Which structure does NOT have a connection to the parasympathetic nervous system?
Which structure does NOT have a connection to the parasympathetic nervous system?
What percentage of norepinephrine is typically transformed into epinephrine in the adrenal medulla?
What percentage of norepinephrine is typically transformed into epinephrine in the adrenal medulla?
Which process accounts for the removal of 50 to 80 percent of secreted norepinephrine?
Which process accounts for the removal of 50 to 80 percent of secreted norepinephrine?
What is the primary mechanism of action for muscarinic receptors?
What is the primary mechanism of action for muscarinic receptors?
How long does norepinephrine generally remain active in tissues?
How long does norepinephrine generally remain active in tissues?
What are nicotinic receptors primarily classified as?
What are nicotinic receptors primarily classified as?
Which enzyme is NOT involved in the destruction of norepinephrine?
Which enzyme is NOT involved in the destruction of norepinephrine?
What type of receptors does muscarine specifically activate?
What type of receptors does muscarine specifically activate?
Which of the following statements about acetylcholine is incorrect?
Which of the following statements about acetylcholine is incorrect?
Which two major classes of adrenergic receptors are identified?
Which two major classes of adrenergic receptors are identified?
What percentage of secretion from the adrenal medulla is epinephrine on average?
What percentage of secretion from the adrenal medulla is epinephrine on average?
Which receptor type does norepinephrine primarily excite?
Which receptor type does norepinephrine primarily excite?
What occurs during a mass discharge of the sympathetic nervous system?
What occurs during a mass discharge of the sympathetic nervous system?
What is the result of stimulating the adrenal medullae?
What is the result of stimulating the adrenal medullae?
Which type of tone reflects the ongoing activity of the sympathetic nervous system?
Which type of tone reflects the ongoing activity of the sympathetic nervous system?
Which of the following is a characteristic of the hormones epinephrine and norepinephrine once released into circulation?
Which of the following is a characteristic of the hormones epinephrine and norepinephrine once released into circulation?
What is the primary role of the sympathetic and parasympathetic systems in the body?
What is the primary role of the sympathetic and parasympathetic systems in the body?
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Study Notes
Neuron Classification
- Neurons are classified by the number of processes extending from the cell body.
- Most neurons are multipolar; they have multiple dendrites and one axon.
- Bipolar neurons are located in the retina, olfactory mucosa, and inner ear, involved in the senses of sight, smell, and balance.
- Pseudounipolar neurons are found in spinal ganglia and most cranial ganglia.
- Sensory neurons (afferent) receive stimuli from body receptors.
- Motor neurons (efferent) transmit impulses to effector organs, such as muscles and glands.
Functional Subdivisions of Nervous Components
- Somatic motor nerves are voluntary and innervate skeletal muscles.
- Autonomic motor nerves control involuntary functions including glands, cardiac muscle, and smooth muscle.
- Interneurons connect other neurons, forming complex circuits in the CNS and retina.
Structure of Motor Neuron
- Composed of three major parts:
- Soma: main body of the neuron.
- Axon: extends from soma into peripheral nerves, transmitting impulses.
- Dendrites: numerous branching projections extending from the soma.
Chemical Synapse Structure
- The presynaptic terminal connects to the postsynaptic neuron via a synaptic cleft (200-300 angstroms wide).
- Contains transmitter vesicles with neurotransmitters and mitochondria for energy.
Sympathetic Nerve Endings and Hormones
- Preganglionic sympathetic fibers reach adrenal medullae without synapsing.
- They end on modified neuronal cells that secrete epinephrine and norepinephrine into the bloodstream.
- Secretory cells are derived from nervous tissue and have remnants of nerve fibers.
Parasympathetic Nervous System
- Parasympathetic fibers exit through cranial nerves III, VII, IX, and X, and some sacral spinal nerves.
- Vagus nerve (cranial nerve X) contains about 75% of parasympathetic fibers. It innervates major organs in the thoracic and abdominal regions.
- Has both preganglionic and postganglionic neurons, with postganglionic neurons located within the walls of the organs they control.
Neurotransmitter Functions
- Cholinergic fibers secrete acetylcholine, while adrenergic fibers secrete norepinephrine.
- Acetylcholine synthesized in nerve endings and has a brief action time, broken down by acetylcholinesterase.
- Norepinephrine synthesis starts in nerve endings; 80% converted to epinephrine in adrenal medulla.
Acetylcholine Receptor Types
- Muscarinic receptors: use G proteins, located on effector cells of the parasympathetic and sympathetic systems.
- Nicotinic receptors: ligand-gated ion channels at synapses between preganglionic and postganglionic neurons.
Adrenergic Receptors
- Divided into alpha and beta receptors.
- Norepinephrine predominantly excites alpha receptors while epinephrine activates both types equally.
Sympathetic and Parasympathetic Stimulation
- Sympathetic stimulation can lead to excitation or inhibition depending on the organ.
- Adrenal medullae release hormones which amplify sympathetic effects and prolong actions for 2-4 minutes.
Nervous System Tone
- The sympathetic and parasympathetic systems maintain a baseline activity level known as tone.
- Tone allows for fine control in increasing or decreasing organ activity as needed.
Alarm or Stress Response
- Mass discharge of the sympathetic nervous system enhances the body’s ability for vigorous physical activity during stressful situations.
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