39 Questions
What ions are involved in the sequential movement during the action potential?
Na, K
Where is the trigger zone located in a neuron?
Axon hillock
What type of potential change occurs during hyperpolarization?
Hyperpolarization
Which part of the neuron is considered as the conducting zone?
Axon
What is the main mechanism for the transmission of action potentials along the neuron?
Electrotonic flow of current leading to depolarization of adjacent resting regions
What happens to the information about the event that elicited the action potential as it travels along the neuron?
It may not travel far due to electrotonic current leak
Why does the transmission of action potentials only go in one direction under normal circumstances?
Depolarization of adjacent resting regions leads to new action potentials in one direction
What slows down the flow of information along the neuron?
Continual regeneration of action potentials
Which of the following is responsible for the jumping of action potentials between nodes of Ranvier in myelinated nerve fibers?
Saltatory conduction
What is responsible for the formation of myelin in the peripheral nervous system?
Schwann cells
What covers the nodes of Ranvier in myelinated axons?
Myelin sheath
What causes local current flow, depolarizing adjacent inactive nodes during an action potential?
$Na^+$ and $K^+$ ion channels
Which factors affect the speed of impulse conduction?
$O_2$ levels and temperature
What are examples of demyelination diseases?
Guillain-Barré syndrome, multiple sclerosis, dementias
What causes Guillain-Barré syndrome?
Inflammation due to autoimmune response damaging peripheral nerves
What characterizes multiple sclerosis?
Inflammatory disease affecting the central nervous system with multiple lesions
What is Alzheimer's disease commonly associated with?
All of the above
Which type of muscles and glands does the autonomic nervous system primarily control?
Smooth and cardiac muscles, internal organs, glands, and blood vessels
What is the main focus of understanding in relation to the autonomic nervous system's arrangement?
Arrangement of the autonomic NS and its associated ganglia
Which part of the body is primarily controlled by the somatic nervous system?
Skin, skeletal muscles, joints, bones, and ligaments
Where do preganglionic parasympathetic motor fibers exit?
Lateral horn of sacral spinal segments S2-S4
Which cranial nerves contain parasympathetic preganglionic fibers?
CN III, VII, and IX
Where do the greater splanchnic nerves originate from?
T5-T9
Which ganglia house postganglionic motor neurons for CN X (vagus)?
Parasympathetic ganglia adjacent to the target organs
What is the main function of the enteric nervous system (ENS)?
Govern the function of the gastrointestinal tract (GIT)
Where are neurons of the enteric nervous system located?
In the wall of the GIT
What type of fibers are mainly concerned with detecting pain from viscera?
Visceral sensory fibers accompanying sympathetic fibers
What is responsible for referred pain?
Axons carrying pain sense from viscera synapsing on neurons in the dorsal horn receiving somatosensory pain fibers from the skin.
What can modify the activity of the autonomic nervous system to lower blood pressure?
Drugs blocking sympathetic nerve endings causing vasodilatation of peripheral blood vessels.
Where are the ganglia of the Parasympathetic Division located?
Adjacent to the viscera they supply
Which division of the ANS is associated with the 'Fight or Flight Response'?
Sympathetic Division
Where do the sympathetic preganglionic fibers exit the spinal cord?
T1-L2 segments
What is the function of the Parasympathetic Division of the ANS?
Slows heart rate, increases digestive functions
Where are autonomic ganglia located?
Outside the CNS in the PNS
What is the main function of Sympathetic Nervous System?
Increases heart rate and blood pressure
How many types of autonomic ganglia are there?
Sympathetic and Parasympathetic
Where are Parasympathetic ganglia typically situated?
Adjacent to the viscera they supply
What is a characteristic of sympathetic preganglionic fibers?
They exit at T1-L2 segments and join the sympathetic chain as white rami communicans.
Where does the Parasympathetic Division have its ganglia located?
In the Craniosacral outflow
Study Notes
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New action potentials are not generated at every point in membranes due to a limited number of voltage-gated sodium channels.
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Graded potentials do not result in action potentials at every point.
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Saltatory conduction is the jumping of action potentials between nodes of Ranvier in myelinated nerve fibers.
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Myelin is formed by Schwann cells in the peripheral nervous system and oligodendrocytes in the central nervous system.
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Myelin sheath covers the nodes of Ranvier in myelinated axons.
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An active node at the peak of an action potential causes local current flow, which depolarizes the adjacent inactive node, bringing it to threshold.
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Factors affecting the speed of impulse conduction include myelination and the diameter of the fiber.
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Nerve fibers are classified based on axon diameter and presence of myelination.
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Examples of demyelination diseases include Guillain-Barré syndrome, multiple sclerosis, and dementias.
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Guillain-Barré syndrome is caused by the immune system damaging the peripheral nervous system, resulting in muscle weakness and loss of reflexes.
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Multiple sclerosis is an immune-mediated inflammatory demyelinating disease of the central nervous system, characterized by multiple lesions and neurological symptoms.
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Dementia is a degenerative disease affecting memory, language, and other cognitive abilities.
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Alzheimer's disease is the most common cause of dementia.
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Self-assessment: A 27-year-old nurse named Nadia experienced tingling and numbness in her hands and feet, followed by muscle weakness and fatigue. She fell during a ward round, and electrophysiological studies revealed decreased motor nerve conduction velocity. A diagnosis of multiple sclerosis was made based on history and investigations.
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Decreased impulse conduction speed can be attributed to demyelination or axonal damage.
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Nadia's symptoms of muscle weakness and fatigue can be correlated with the decreased speed of impulse conduction.
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Factors affecting impulse conduction speed include myelination, axon diameter, and temperature.
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Other causes of demyelination include viral infections, toxins, and trauma.
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EE (Enteric Nervous System) and ANS (Autonomic Nervous System) are two different parts of the nervous system
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The Somatic Motor System is controlled by a single nerve, while the ANS has two nerves: the preganglionic and postganglionic nerves
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The ANS has two divisions: the Sympathetic Division (Fight or Flight Response) and the Parasympathetic Division (Rest and Digest Response)
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The Sympathetic Division increases heart rate and blood pressure, depresses digestive function, and increases sweating
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The Parasympathetic Division slows heart rate, falls in pressure, increases digestive functions, and stops sweating
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The Sympathetic Division has its ganglia located in the Thoracolumbar outflow, while the Parasympathetic Division has its ganglia in the Craniosacral outflow
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Autonomic ganglia are located outside the CNS in the PNS, providing a location for synapse and are of two types: Sympathetic and Parasympathetic
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Sympathetic ganglia are located along the sympathetic trunk and there are about 24 ganglia in each sympathetic trunk
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Parasympathetic ganglia are smaller and located more peripherally than sympathetic ganglia, typically situated adjacent to the viscera they supply
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The Sympathetic Nervous System has a wide distribution targeting peripheral effectors and internal organs in the head, neck, thorax, abdomen, and pelvis
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Sympathetic preganglionic fibers exit the spinal cord at T1-L2 segments and join the sympathetic chain as white rami communicans
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Parasympathetic ganglia include the Ciliary, Pterygopalatine, Otic, and Submandibular ganglia, among others, and are located adjacent to the viscera they supply
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The Sympathetic Nervous System has a wide distribution targeting peripheral effectors as skin glands, erector pili muscles, and blood vessels, as well as internal organs in the head, neck, thorax, abdomen, and pelvis.
Test your knowledge on the propagation of action potentials in nerve cells, including the differences between graded and action potentials, as well as saltatory conduction in myelinated nerve fibers.
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