Nervous System and Neuron Function
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Questions and Answers

What are the three divisions of the peripheral nervous system?

  • Somatic nervous system and autonomic nervous system
  • Sympathetic nervous system and parasympathetic nervous system
  • Central nervous system, peripheral nervous system, enteric nervous system
  • Sensory division and efferent division (correct)

    • What are the two divisions of the efferent division of the peripheral nervous system?

  • Sensory division and efferent division
  • Central nervous system, peripheral nervous system, enteric nervous system
  • Sympathetic nervous system and parasympathetic nervous system
  • Somatic nervous system and autonomic nervous system (correct)

    • What are the two divisions of the autonomic nervous system?

  • Central nervous system, peripheral nervous system, enteric nervous system
  • Somatic nervous system and autonomic nervous system
  • Sympathetic nervous system and parasympathetic nervous system (correct)
  • Sensory division and efferent division

    • What is a synapse in neurons?

    <p>The region where an axon terminal communicates with its postsynaptic target cell</p> Signup and view all the answers

    What are the three parts of a neuron?

    <p>Dendrites (input signal), cell body (integration), presynaptic axon terminal (output signal)</p> Signup and view all the answers

    Which of the following are glial cells in the central nervous system?

    <p>Ependymal cells, astrocytes, microglia (modified immune cells), oligodendrocytes</p> Signup and view all the answers

    Which of the following are glial cells in the peripheral nervous system?

    <p>Schwann cells, satellite cells</p> Signup and view all the answers

    What happens to graded potentials as they spread out from the point of origin?

    <p>They decrease in strength due to current leak out of the cell</p> Signup and view all the answers

    What happens to a subthreshold graded potential at the trigger zone?

    <p>It does not initiate an action potential</p> Signup and view all the answers

    What happens during the absolute refractory period?

    <p>No stimulus can trigger another action potential.</p> Signup and view all the answers

    What happens during the relative refractory period?

    <p>Only a larger-than-normal stimulus can initiate a new action potential.</p> Signup and view all the answers

    Which ion is primarily responsible for the resting membrane potential?

    <p>Potassium</p> Signup and view all the answers

    What happens in normokalemia during a subthreshold graded potential?

    <p>It does not fire an action potential</p> Signup and view all the answers

    What happens in normokalemia during a suprathreshold stimulus?

    <p>It fires an action potential</p> Signup and view all the answers

    What happens in hyperkalemia to the membrane potential?

    <p>It is brought closer to the threshold</p> Signup and view all the answers

    What happens in hypokalemia to the neuron's ability to fire an action potential?

    <p>The neuron is less likely to fire an action potential.</p> Signup and view all the answers

    What indicates the strength of a stimulus?

    <p>The frequency of action potential firing</p> Signup and view all the answers

    Explain a divergent pathway of integration in neurons.

    <p>One presynaptic neuron branches to affect a larger number of postsynaptic neurons</p> Signup and view all the answers

    What happens during no temporal summation between graded potentials?

    <p>Two subthreshold graded potentials will not initiate an action potential if they are far apart in time</p> Signup and view all the answers

    What are the neurotransmitters used in sympathetic and parasympathetic pathways in autonomic synapses?

    <p>Sympathetic pathways use acetylcholine and norepinephrine whereas parasympathetic pathways use acetylcholine</p> Signup and view all the answers

    What is the function of the adrenal medulla in autonomic synapse?

    <p>Secretes epinephrine into the blood</p> Signup and view all the answers

    List the targets of autonomic synapses.

    <p>Smooth/cardiac muscles, some endocrine/exocrine glands, some adipose tissue</p> Signup and view all the answers

    Where do somatic nervous system synapses occur?

    <p>Neuromuscular junction (NMJ)</p> Signup and view all the answers

    What are simple receptors in the somatic nervous system?

    <p>Neurons with free nerve endings; may have myelinated or unmyelinated axons</p> Signup and view all the answers

    What are complex neural receptors in the somatic nervous system?

    <p>Have nerve endings enclosed in connective tissue capsules</p> Signup and view all the answers

    What are special sense receptors in the somatic nervous system?

    <p>Cells that release neurotransmitter onto sensory neurons, initiating an action potential</p> Signup and view all the answers

    What are tonic receptors?

    <p>Slowly adapting receptors that respond for the duration of the stimulus</p> Signup and view all the answers

    Which receptors respond to strong noxious (painful) stimuli?

    <p>Nociception receptors</p> Signup and view all the answers

    What are pain and itch senses mediated by?

    <p>Nociception receptors</p> Signup and view all the answers

    How does inflammation affect perception of pain?

    <p>Increases it</p> Signup and view all the answers

    What are the two possible nociception pathways?

    <p>Reflective protective responses; ascending pathway to the cerebral cortex (pain and itch)</p> Signup and view all the answers

    Explain the gate-control model of pain modulation.

    <p>Nonpainful stimuli can diminish the pain signal</p> Signup and view all the answers

    What is referred pain?

    <p>Pain in internal organs is often sensed on the surface of the body</p> Signup and view all the answers

    What is neuropathic chronic pain?

    <p>Damage to, or long-term changes, in the nervous system may be due to diabetes (chronically elevated glucose) or chemotherapy (peripheral neuropathy)</p> Signup and view all the answers

    What are the three divisions of the trigeminal nerve (cranial nerve V)?

    <p>Ophthalmic division (V1), maxillary division (V2), mandibular division (V3)</p> Signup and view all the answers

    What senses does the trigeminal nerve process?

    <p>Touch, proprioception, pressure, vibration, and nociception from the face/meninges/brain blood vessels</p> Signup and view all the answers

    What is the trigeminovascular system associated with?

    <p>Headaches (contained within V1 ophthalmic division), plays a role in cerebral blood flow</p> Signup and view all the answers

    What does the trigeminovascular system innervate?

    <p>Brain blood vessels and meninges</p> Signup and view all the answers

    What does the trigeminovascular system join with?

    <p>Somatosensory peripheral neurons that innervate periosteum and muscles</p> Signup and view all the answers

    What are the neuropeptides within the trigeminovascular system?

    <p>Calcitonin gene-related peptide (CGRP), substance P, neurokinin A</p> Signup and view all the answers

    How is the trigeminovascular system activated?

    <p>Unipolarly</p> Signup and view all the answers

    What are the phases of a migraine?

    <p>Premonitory, aura*, headache, postdrome</p> Signup and view all the answers

    What are the symptoms of the premonitory phase of a migraine?

    <p>Neck pain, fatigue, mood/cognitive effects, food cravings</p> Signup and view all the answers

    What are the symptoms of the aura phase of a migraine?

    <p>Visual disturbance*, numbness and tingling, mumbling or slurred speech</p> Signup and view all the answers

    What are the symptoms of the headache phase of a migraine?

    <p>Pain, nausea and vomiting, sensory sensitivity</p> Signup and view all the answers

    What are the symptoms of the postdrome phase of a migraine?

    <p>Tiredness, concentration impairment</p> Signup and view all the answers

    What is cortical spreading depolarization?

    <p>Transient wave of neuronal depolarization; hyperexcitability due to glutamate and/or extracellular potassium (associated with aura symptoms)</p> Signup and view all the answers

    How is serotonin involved in migraines?

    <p>Usually involved in cortical excitability and vasoconstriction; decreased levels of it in migraines which causes vasodilation</p> Signup and view all the answers

    How are neuropeptides involved in migraines?

    <p>CGRP, substance P, neurokinin A stimulate mast cells (release histamine and prostaglandins) and promote vasodilation/neurogenic inflammation which causes activation of pain receptors</p> Signup and view all the answers

    What changes in hypothalamic function can occur during the premonitory phase of a migraine?

    <p>Polyuria, mood change, appetite change</p> Signup and view all the answers

    Why might there be increased activity in the occipital cortex during a migraine?

    <p>Photosensitivity</p> Signup and view all the answers

    How is the brainstem involved in the symptoms of a migraine?

    <p>Nausea</p> Signup and view all the answers

    Which of the following are clinical features of a migraine?

    <p>Duration 4-72 hours; unilateral; moderate-severe pain; pulsatile pain; other symptoms include nausea, vomiting, aura</p> Signup and view all the answers

    What are some common triggers of tension-type headaches?

    <p>Muscle tightness, sleep deprivation, dehydration, stress</p> Signup and view all the answers

    What is the origin of pain in tension-type headaches?

    <p>Muscular nociceptors; input from myofascial structures via trigeminal ganglion and dorsal horns of spinal cord at C1 to C4</p> Signup and view all the answers

    What is hyperalgesia?

    <p>Exaggerated response to painful stimuli</p> Signup and view all the answers

    What is allodynia?

    <p>Pain response to non-painful stimuli</p> Signup and view all the answers

    Which fibers are abnormally sensitive in chronic pain due to tension-type headaches?

    <p>A-beta fibers</p> Signup and view all the answers

    What are myofascial trigger points?

    <p>Muscle areas with hypersensitivity to pressure; cause referred pain</p> Signup and view all the answers

    What is central sensitization in tension-type headaches?

    <p>Trigeminal nucleus, dorsal horn, thalamus; hypersensitivity at non-head/neck areas</p> Signup and view all the answers

    Study Notes

    Nervous System Organization and Function

    • Nervous system is organized into three major divisions: central nervous system (CNS), peripheral nervous system (PNS), and enteric nervous system.
    • The PNS further divides into sensory and efferent divisions.
    • The efferent division splits into the somatic nervous system and autonomic nervous system.
    • The autonomic system is composed of the sympathetic nervous system and parasympathetic nervous system.

    Neuron Structure and Function

    • Neurons have dendrites for input, a cell body for signal integration, and axon terminals for output.
    • Synapses are the spaces between neurons where signals are transmitted.
    • Glial cells support neurons in CNS (ependymal, astrocytes, microglia, oligodendrocytes) and PNS (Schwann cells, satellite cells).
    • Graded potentials weaken as they spread from the origin due to current leakage.
    • Subthreshold graded potentials fail to initiate an action potential at the trigger zone; suprathreshold do.
    • Action potentials are influenced by refractory periods: absolute (no stimulus can trigger another action potential), relative (only a larger stimulus can).
    • Resting membrane potential is primarily determined by potassium ions.
    • Hyperkalemia brings the neuron closer to threshold, while hypokalemia makes it harder to reach threshold.

    Neurotransmitter Release and Synaptic Integration

    • Stimulus strength is encoded by action potential firing frequency.
    • Divergent pathways involve a single presynaptic neuron influencing multiple postsynaptic neurons.
    • Convergent pathways involve numerous presynaptic neurons influencing a single postsynaptic neuron.
    • Temporal summation occurs when two subthreshold graded potentials arrive close together in time, potentially triggering an action potential.
    • Synaptic transmission in the autonomic nervous system uses acetylcholine and norepinephrine (sympathetic), whereas parasympathetic pathways mainly use acetylcholine.
    • The adrenal medulla releases epinephrine into the bloodstream.
    • Autonomic pathways target smooth/cardiac muscles, glands, and adipose tissue.
    • Somatic nervous system transmission occurs at neuromuscular junctions (NMJs).

    Sensory Neuron Receptors and Pain

    • Sensory receptors in the somatic nervous system categorized as simple (free nerve endings), complex (encapsulated), or special sense (neurotransmitter-releasing cells).
    • Receptors can be tonic (slowly adapting) or phasic (rapidly adapting).
    • Nociceptors respond to noxious stimuli (chemical, mechanical, thermal).
    • Inflammation increases pain perception.
    • Nociception pathways include reflexive responses and those leading to pain and itch sensation in the CNS.
    • Pain modulation can occur through the gate-control model, where non-painful stimuli lessen pain sensation.
    • Referred pain occurs when pain from internal organs is perceived on the body surface.
    • Neuropathic pain stems from damage or changes in the nervous system.

    Cranial Nerves (Trigeminal - CN V)

    • The trigeminal nerve (CN V) has three divisions: ophthalmic (V1), maxillary (V2), and mandibular (V3).
    • CN V processes sensations like touch, proprioception, pressure, vibration, and nociception from the face, meninges, and brain blood vessels.
    • The trigeminovascular system is responsible for headaches and cerebral blood flow, innervating brain blood vessels and meninges, with connections to somatosensory peripheral neurons.
    • Neuropeptides like CGRP, substance P, and neurokinin A are important in this system.
    • Trigeminovascular system activation is unipolar.
    • Migraine phases include premonitory, aura (visual disturbances, numbness, tingling), headache, and postdrome (tiredness, concentration impairment).
    • Cortical spreading depolarization involves a wave of neuronal depolarization.
    • Serotonin is involved in migraine regulation, with decreased levels associated with vasodilation.
    • Neuropeptides (CGRP, substance P, neurokinin A) cause vasodilation, and inflammation through mast cell activation.

    Headaches (Tension-type and Cluster)

    • Tension-type headaches are related to muscle tension, often triggered by stress or sleep deprivation, involving muscular nociceptors with referred pain potential.
    • Central sensitization and hyperalgesia (exaggerated pain) or allodynia (pain from non-painful stimuli) can be present.
    • A-beta fibers are abnormally sensitive in chronic tension-type headaches.
    • Myofascial trigger points cause referred pain in muscle areas.
    • Central sensitization involves trigeminal nucleus, dorsal horn, and thalamus.
    • Nitric oxide is thought to induce tension headache central sensitization.
    • Cluster headaches involve circadian and seasonal patterns; activation of ipsilateral inferior hypothalamic gray matter; release of CGRP, resulting in parasympathetic activation via superior salivatory nucleus and release of vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating peptide (PACAP).

    Cognitive Aging and Dementia

    • Normal cognitive aging shows some short-term memory decline, but long-term memory retrieval processes are affected.
    • Neurotransmitters like acetylcholine and glutamate are affected by declines in neural network connectivity.
    • Dementia is defined as deterioration of cognitive function interfering with activities.
    • Alzheimer's disease is a common dementia cause (60-80%).
    • Other dementia causes include vascular, frontotemporal, Creutzfeldt-Jakob, Wernicke-Korsakoff, Huntington's, and Parkinson's diseases, as well as dementia with Lewy bodies.
    • Alzheimer's disease presents with micro (amyloid plaques and neurofibrillary tangles) and macro changes (cortical atrophy).
    • Amyloid plaques are caused by altered APP degradation and amyloid beta protein accumulation.
    • Neurofibrillary tangles form from hyperphosphorylated Tau protein accumulation.
    • Decreased acetylcholine production is often present in Alzheimer's disease.
    • APO-E4 is linked to amyloid deposition and clearance.
    • Vascular disease can contribute to Alzheimer's.
    • Alzheimer's hallmark symptoms include short-term memory loss, language difficulty, and behavioral changes.
    • Survival after diagnosis is around eight to ten years.

    Myasthenia Gravis

    • Myasthenia gravis is an autoimmune neuromuscular disorder causing motor end-plate dysfunction.
    • Deficiencies in acetylcholine receptors are a key feature.
    • Thymus abnormalities are present in many cases.
    • This leads to decrements in the amplitude of muscle cell action potentials and may cause respiratory compromise.
    • Symptoms often start in cranial muscles.

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    Explore the organization and functions of the nervous system in this quiz. Delve into the divisions of the nervous system, the structure of neurons, and the mechanisms of signal transmission. Test your knowledge on key concepts like graded potentials and synapse functions.

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