Neuroglial Cells and Multiple Sclerosis Quiz
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Questions and Answers

What is the primary function of microglial cells in the central nervous system (CNS)?

  • To form myelin sheaths around nerve fibers
  • To circulate cerebrospinal fluid
  • To provide defensive support (correct)
  • To create permeable barriers between fluids

    • Which characteristic distinguishes ependymal cells?

  • They possess cilia to circulate cerebrospinal fluid (correct)
  • They are involved in neural signal transmission
  • They are primarily responsible for myelination
  • They have a branched structure

    • What do oligodendrocytes primarily wrap around in the CNS?

  • Nerve fibers (correct)
  • Blood vessels
  • Ependymal cells
  • Neuronal cell bodies

    • What is primarily affected by multiple sclerosis?

    <p>Young adults</p> Signup and view all the answers

    What forms the barrier between cerebrospinal fluid and the surrounding tissue in the CNS?

    <p>Ependymal cells</p> Signup and view all the answers

    What happens to the myelin sheaths in the central nervous system during multiple sclerosis?

    <p>They are destroyed by an autoimmune response</p> Signup and view all the answers

    Which of the following statements is true regarding oligodendrocytes?

    <p>They provide insulation for thicker CNS nerve fibers</p> Signup and view all the answers

    What do the increased Na+ channels in demyelinated axons cause?

    <p>Cycles of relapse and remission</p> Signup and view all the answers

    How do cilia on ependymal cells assist in the CNS?

    <p>They facilitate the circulation of cerebrospinal fluid</p> Signup and view all the answers

    Which symptom is commonly associated with multiple sclerosis?

    <p>Visual disturbances</p> Signup and view all the answers

    What role do microglial cells play in the maintenance of the CNS?

    <p>Protection against pathogens and injury</p> Signup and view all the answers

    What type of drugs are typically used to treat multiple sclerosis?

    <p>Drugs that modify immune system activity</p> Signup and view all the answers

    Which type of neuroglia is specifically known for its branched structure?

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

    What term describes the junctions that mediate information transfer between neurons?

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

    In the context of synapses, what is the role of the presynaptic neuron?

    <p>Conducts impulses toward the synapse</p> Signup and view all the answers

    Which type of cell could a postsynaptic neuron be in the peripheral nervous system?

    <p>Muscle cell or gland cell</p> Signup and view all the answers

    What is the primary function of the somatic nervous system?

    <p>Conduct impulses from the CNS to skeletal muscle</p> Signup and view all the answers

    Which component is part of the peripheral nervous system?

    <p>Cranial nerves</p> Signup and view all the answers

    What type of fibers convey impulses from skin, skeletal muscles, and joints to the CNS?

    <p>Sensory fibers</p> Signup and view all the answers

    Which subdivision of the autonomic nervous system works to prepare the body for stressful situations?

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

    The visceral motor nerve fibers are primarily associated with which system?

    <p>Autonomic nervous system</p> Signup and view all the answers

    Which part of the nervous system is considered the voluntary nervous system?

    <p>Somatic nervous system</p> Signup and view all the answers

    Which division of the peripheral nervous system transmits impulses to muscles and glands?

    <p>Motor division</p> Signup and view all the answers

    Which statement about the sympathetic and parasympathetic divisions is correct?

    <p>They work in opposition to each other</p> Signup and view all the answers

    What mechanism does not terminate neurotransmitter effects?

    <p>Continuous binding to receptor</p> Signup and view all the answers

    How do electrical synapses mainly differ from chemical synapses?

    <p>They use gap junctions for rapid communication</p> Signup and view all the answers

    What type of potential is caused by neurotransmitter binding that results in hyperpolarization?

    <p>Inhibitory postsynaptic potential (IPSP)</p> Signup and view all the answers

    Which factor does not influence the strength of postsynaptic potentials?

    <p>Type of receptor activated</p> Signup and view all the answers

    What is the primary result of an excitatory postsynaptic potential (EPSP)?

    <p>Depolarization of the postsynaptic membrane</p> Signup and view all the answers

    In which regions are electrical synapses most abundant?

    <p>Hippocampus and embryonic nervous tissue</p> Signup and view all the answers

    What occurs if an EPSP reaches threshold strength?

    <p>Triggering of an action potential</p> Signup and view all the answers

    Which of the following is true regarding the reuptake of neurotransmitters?

    <p>It is a mechanism for terminating neurotransmitter effects</p> Signup and view all the answers

    At time = 0 ms, what is the state of the action potential at the recording electrode?

    <p>The action potential has not yet reached the recording electrode.</p> Signup and view all the answers

    What occurs at 2 ms in the propagation of the action potential?

    <p>The action potential reaches its peak.</p> Signup and view all the answers

    What is the primary reason the inside of a cell is more negative than the outside?

    <p>More K+ ions diffuse out of the cell than Na+ ions diffuse in.</p> Signup and view all the answers

    What is the membrane potential at the peak of the action potential?

    <p>+30 mV</p> Signup and view all the answers

    Which ion is primarily responsible for the greater permeability of the plasma membrane at rest?

    <p>K+</p> Signup and view all the answers

    What is the function of the sodium-potassium pump (Na+/K+ ATPase)?

    <p>It stabilizes the resting membrane potential by maintaining concentration gradients.</p> Signup and view all the answers

    What characterizes the membrane potential at 4 ms?

    <p>The membrane potential is hyperpolarized.</p> Signup and view all the answers

    What happens to the resting membrane potential when the concentration of K+ outside the cell increases?

    <p>The resting membrane potential becomes more positive.</p> Signup and view all the answers

    What is the state of the action potential immediately after its peak?

    <p>The membrane hyperpolarizes.</p> Signup and view all the answers

    During which phase would the membrane potential be at -70 mV?

    <p>At rest before the action potential.</p> Signup and view all the answers

    How do graded potentials differ from action potentials?

    <p>Graded potentials can operate over short distances, while action potentials are long-distance signals.</p> Signup and view all the answers

    What does hyperpolarization indicate in the cycle of an action potential?

    <p>The membrane potential is lower than resting potential.</p> Signup and view all the answers

    What major factor influences changes in membrane potential?

    <p>Alterations in the concentration of ions across the membrane.</p> Signup and view all the answers

    What is likely to happen after the membrane reaches the hyperpolarized state?

    <p>The membrane returns to resting potential gradually.</p> Signup and view all the answers

    Which of the following statements about the resting membrane potential is correct?

    <p>It is a consequence of unequal ion distribution across the plasma membrane.</p> Signup and view all the answers

    Which of the following ions is least permeable across the plasma membrane at rest?

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

    What role do muscle spindles play in the function of reflexes?

    <p>They send signals regarding muscle length.</p> Signup and view all the answers

    Which type of sensory endings in muscle spindles is responsible for detecting the rate and degree of stretch?

    <p>Anulospiral endings</p> Signup and view all the answers

    What does the central region of intrafusal muscle fibers lack?

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

    What might an exaggerated reflex indicate in a clinical assessment?

    <p>Potential degeneration or pathology in specific nervous system regions</p> Signup and view all the answers

    Which of the following best describes extrafusal muscle fibers?

    <p>They contract and enable muscle movement.</p> Signup and view all the answers

    What type of receptors respond specifically to pain-causing stimuli?

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

    What type of reflex is primarily associated with the stretch reflex?

    <p>Somatic reflex</p> Signup and view all the answers

    Which receptors are responsible for sensing changes in temperature?

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

    Which of the following statements about the tendon organs is true?

    <p>They send information regarding muscle tension.</p> Signup and view all the answers

    Clinical testing of somatic reflexes can reveal...

    <p>Conditions of the nervous system.</p> Signup and view all the answers

    What are exteroceptors primarily responsible for?

    <p>Responding to touch, pressure, pain, and temperature from external sources</p> Signup and view all the answers

    Which classification of receptors provides information about the position of body parts?

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

    What distinguishes chemoreceptors from other types of receptors?

    <p>They respond to changes in chemical substances.</p> Signup and view all the answers

    What is the result of activating sensory receptors?

    <p>Nerve impulses triggered by graded potentials</p> Signup and view all the answers

    Which statement accurately describes proprioceptors?

    <p>They respond to stretch in muscles and joints.</p> Signup and view all the answers

    Which type of receptor would primarily be involved in detecting extreme heat or cold?

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

    Where is the primary visual cortex located?

    <p>Extreme posterior tip of occipital lobe</p> Signup and view all the answers

    What area of the cerebral cortex is primarily responsible for interpreting pitch and loudness from the inner ear?

    <p>Primary auditory cortex</p> Signup and view all the answers

    Which cortex is involved in the conscious awareness of balance?

    <p>Vestibular cortex</p> Signup and view all the answers

    What is the primary function of the primary motor cortex?

    <p>To allow conscious control of precise movements</p> Signup and view all the answers

    Which area is primarily associated with motor speech production?

    <p>Broca's area</p> Signup and view all the answers

    The olfactory cortex is part of which larger structure involved in the perception of smells?

    <p>Limbic system</p> Signup and view all the answers

    What is the primary function of the gustatory cortex?

    <p>Perception of taste</p> Signup and view all the answers

    What is the role of the premotor cortex in movement?

    <p>It helps plan and stage motor activities</p> Signup and view all the answers

    What type of receptors are nociceptors classified as?

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

    Which area of the cerebral cortex is responsible for conscious perception of visceral sensations?

    <p>Visceral sensory area</p> Signup and view all the answers

    The term 'motor homunculi' refers to what concept?

    <p>The mapping of body muscles to specific areas on the primary motor cortex</p> Signup and view all the answers

    Where are tactile (Merkel) discs primarily located?

    <p>In deeper layers of the epidermis</p> Signup and view all the answers

    Which type of corpuscle is involved in detecting deep pressure and vibration?

    <p>Lamellar (Pacinian) corpuscles</p> Signup and view all the answers

    What key function does the frontal eye field serve in the cerebral cortex?

    <p>Controlling voluntary eye movements</p> Signup and view all the answers

    What function does the visual association area primarily serve?

    <p>Interpreting visual stimuli based on past experiences</p> Signup and view all the answers

    The primary auditory cortex is located at which part of the brain?

    <p>Superior margin of temporal lobes</p> Signup and view all the answers

    What is the primary function of hair follicle receptors?

    <p>Detect the bending of hairs</p> Signup and view all the answers

    What distinguishes the location of Broca's area in the brain?

    <p>It is usually found in the left hemisphere</p> Signup and view all the answers

    What classification do almost all encapsulated dendritic endings belong to?

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

    Which statement best describes the pyramidal cells found in the primary motor cortex?

    <p>They enable conscious control of precise muscle movements.</p> Signup and view all the answers

    What is the role of the pyramidal (corticospinal) tracts emerging from the primary motor cortex?

    <p>To carry motor information from the cortex to the spinal cord</p> Signup and view all the answers

    Which sensory receptor is mostly located in sensitive areas, such as the fingertips?

    <p>Tactile (Meissner’s) corpuscles</p> Signup and view all the answers

    Which type of receptor is primarily activated by chemicals released from damaged tissue?

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

    What is the primary characteristic of encapsulated dendritic endings?

    <p>They are involved in discriminative touch</p> Signup and view all the answers

    What is primarily secreted by the pineal gland in the epithalamus?

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

    Which regions comprise the brain stem?

    <p>Midbrain, pons, and medulla oblongata</p> Signup and view all the answers

    What role does the cerebellum primarily serve in motor activity?

    <p>Coordinating and fine-tuning movements</p> Signup and view all the answers

    Which of the following is NOT a characteristic of the brain stem?

    <p>Regulates emotions and language</p> Signup and view all the answers

    What information does the cerebellum receive from proprioceptors?

    <p>Body position and momentum</p> Signup and view all the answers

    Which function is associated with the cognitive processes of the cerebellum?

    <p>Comparing expected and actual outputs</p> Signup and view all the answers

    In terms of brain composition, how much mass does the cerebellum represent?

    <p>11% of total brain mass</p> Signup and view all the answers

    Which structure forms the roof of the third ventricle?

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

    Which of the following is NOT considered one of the special senses of the body?

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

    What is the primary role of the conjunctiva in the eye?

    <p>To protect the eye and provide lubrication</p> Signup and view all the answers

    Which accessory structure of the eye is responsible for enhancing vision by controlling the amount of light entering?

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

    What term describes the space where the palpebral and bulbar conjunctiva meet?

    <p>Conjunctival sac</p> Signup and view all the answers

    Which component of the eye is mainly responsible for its protection and function?

    <p>Fat cushion</p> Signup and view all the answers

    What is the significance of the small blood vessels found in the bulbar conjunctiva?

    <p>To cause eye redness when dilated</p> Signup and view all the answers

    Which accessory structure is responsible for tear production?

    <p>Lacrimal apparatus</p> Signup and view all the answers

    Which of the following statements about the eyeball's visibility is correct?

    <p>One-sixth of the eye’s surface is visible externally</p> Signup and view all the answers

    Which structure is responsible for maintaining the clarity of the cornea?

    <p>Corneal endothelium</p> Signup and view all the answers

    What is the primary role of the ciliary zonule?

    <p>Supporting the lens in place</p> Signup and view all the answers

    Which part of the eye is known as the blind spot?

    <p>Optic disc</p> Signup and view all the answers

    What fluid is contained in the anterior segment of the eye?

    <p>Aqueous humor</p> Signup and view all the answers

    What is the outermost layer of the eye called?

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

    Which region of the eye has the highest concentration of photoreceptor cells?

    <p>Fovea centralis</p> Signup and view all the answers

    What is the function of the cornea in the eye?

    <p>Bends and allows light to enter the eye</p> Signup and view all the answers

    Which component is not part of the posterior segment of the eye?

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

    Which taste sensation is most sensitive to activation based on gustatory cell response?

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

    What is the process called where a chemical must dissolve in saliva to stimulate taste?

    <p>Taste transduction</p> Signup and view all the answers

    Which mechanism is responsible for the salty taste sensation?

    <p>Na+ influx</p> Signup and view all the answers

    What is the potential explanation for humans' liking of fatty foods?

    <p>Ability to taste long-chain fatty acids</p> Signup and view all the answers

    In the activation of taste receptors, which type of neurotransmitter is mainly released?

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

    How quickly do taste receptors generally adapt to a stimulus?

    <p>3-5 seconds</p> Signup and view all the answers

    Which of the following components is NOT necessary for tasting a chemical?

    <p>Presence of fat molecules</p> Signup and view all the answers

    What is the possible sixth taste sensation that is being investigated?

    <p>Fatty taste</p> Signup and view all the answers

    What type of vision do cones provide?

    <p>Detailed, high-resolution vision in bright light</p> Signup and view all the answers

    Which statement correctly describes color blindness?

    <p>It can be caused by the absence of one or more cone pigments.</p> Signup and view all the answers

    Which visual pigments are associated with cones?

    <p>Green, blue, and red opsins</p> Signup and view all the answers

    What initiates the electrical impulses along the optic nerve?

    <p>The conversion of bent retinal to all-trans-retinal</p> Signup and view all the answers

    In what way do cones differ from rods in terms of signal pathways?

    <p>Cones have nonconverging pathways for detailed vision.</p> Signup and view all the answers

    What is the most common type of color blindness?

    <p>Red-green color blindness</p> Signup and view all the answers

    Which statement about retinal isomers is true?

    <p>The conversion from bent to straight triggers visual signal transmission.</p> Signup and view all the answers

    How does cone vision contribute to color perception?

    <p>Different wavelengths stimulate different cones, creating a variety of hues.</p> Signup and view all the answers

    What is the primary function of the ciliary body in the eye?

    <p>Controls the shape of the lens</p> Signup and view all the answers

    How do the sphincter pupillae and dilator pupillae affect the pupil during different lighting conditions?

    <p>Sphincter pupillae constrict the pupil in bright light</p> Signup and view all the answers

    Which layer of the retina is responsible for absorbing light?

    <p>Pigmented layer</p> Signup and view all the answers

    What role does the ciliary zonule play in the structure of the eye?

    <p>Suspends the lens in place</p> Signup and view all the answers

    Which of the following statements correctly describes the function of photoreceptor cells in the retina?

    <p>Transduce light energy into electrical signals</p> Signup and view all the answers

    What effect do emotional states have on pupil size?

    <p>Pupils dilate when facing appealing stimuli</p> Signup and view all the answers

    Which structure is continuous with the ciliary body and helps to regulate light entry through the pupil?

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

    What is the composition of the retina's inner layer?

    <p>Two-layered membrane with photoreceptors</p> Signup and view all the answers

    Which chamber of the cochlea contains endolymph that is rich in potassium ions?

    <p>Scala media</p> Signup and view all the answers

    What is the main role of the stria vascularis in the cochlea?

    <p>It secretes endolymph to maintain ionic balance.</p> Signup and view all the answers

    Where do the scala tympani and scala vestibuli connect within the cochlea?

    <p>At the helicotrema</p> Signup and view all the answers

    How many rows of outer hair cells are present in the spiral organ of the cochlea?

    <p>Three rows</p> Signup and view all the answers

    Which membrane serves as the 'roof' of the cochlear duct?

    <p>Vestibular membrane</p> Signup and view all the answers

    What type of fluid is found in the scala tympani and scala vestibuli?

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

    Which structure separates the scala media from the scala vestibuli in the cochlea?

    <p>Vestibular membrane</p> Signup and view all the answers

    What is the primary function of the cochlear branch of nerve VIII?

    <p>Transmits sound stimuli to the brain</p> Signup and view all the answers

    What type of chemical messenger secretes chemicals that act on the same cells that release them?

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

    Which class of hormones is synthesized from cholesterol?

    <p>Steroid hormones</p> Signup and view all the answers

    How do hormones primarily exert their effects on target cells?

    <p>By binding to receptors on target cells</p> Signup and view all the answers

    Which action is NOT typically associated with hormone action on target cells?

    <p>Inhibiting enzyme synthesis</p> Signup and view all the answers

    What is a characteristic feature of eicosanoids in relation to hormone classification?

    <p>Most scientists classify them as paracrines rather than hormones.</p> Signup and view all the answers

    What is the primary function of the endocrine system in the body?

    <p>Regulating metabolic activities through hormones</p> Signup and view all the answers

    Which of the following hormones would be produced by an endocrine gland?

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

    Which gland is classified as both an endocrine and exocrine organ?

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

    How does the speed of responses between the endocrine system and nervous system compare?

    <p>Endocrine responses are slower and longer lasting</p> Signup and view all the answers

    Which of the following is NOT a function of the endocrine system?

    <p>Control of voluntary movements</p> Signup and view all the answers

    What type of substances do exocrine glands produce?

    <p>Non-hormonal substances</p> Signup and view all the answers

    Which of the following organs is specifically identified as a neuroendocrine organ?

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

    Which cells or organs are known to produce hormones aside from endocrine glands?

    <p>Adipose cells and thymus</p> Signup and view all the answers

    What is the primary regulatory factor for prolactin (PRL) release?

    <p>Prolactin-inhibiting hormone (PIH)</p> Signup and view all the answers

    What physiological effect occurs as a response to suckling?

    <p>Stimulation of prolactin release</p> Signup and view all the answers

    Which event is associated with rising blood prolactin levels?

    <p>End of pregnancy</p> Signup and view all the answers

    What is the likely result of decreased levels of prolactin-inhibiting hormone (PIH)?

    <p>Stimulated release of PRL</p> Signup and view all the answers

    What hormonal change is likely responsible for breast swelling and tenderness during the menstrual cycle?

    <p>Increase in estrogen</p> Signup and view all the answers

    How do water-soluble hormones primarily exert their effects?

    <p>By acting on plasma membrane receptors</p> Signup and view all the answers

    What is the first step in the cyclic AMP (cAMP) signaling mechanism?

    <p>Hormone binds to the receptor</p> Signup and view all the answers

    What role does cAMP play in the cellular signaling process initiated by hormones?

    <p>It acts as a second messenger activating protein kinases</p> Signup and view all the answers

    Which of the following is NOT a characteristic of lipid-soluble hormones?

    <p>They act via second messengers</p> Signup and view all the answers

    What happens to cAMP in the signaling cascade after its formation?

    <p>It is rapidly degraded by phosphodiesterase</p> Signup and view all the answers

    What is the primary effect of insulin-like growth factors (IGFs) on cells?

    <p>Cellular uptake of nutrients for DNA and protein synthesis</p> Signup and view all the answers

    Which second-messenger system is primarily associated with amino acid-based hormones?

    <p>cAMP system</p> Signup and view all the answers

    Which hormone inhibits growth hormone (GH) release?

    <p>Growth hormone–inhibiting hormone (GHIH)</p> Signup and view all the answers

    Hypersecretion of growth hormone in children leads to which condition?

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

    What is the function of adenylate cyclase in the cAMP signaling pathway?

    <p>To convert ATP into cAMP</p> Signup and view all the answers

    Which type of hormones can enter the cell and directly activate genes?

    <p>Thyroid hormones</p> Signup and view all the answers

    What physiological condition results from hyposecretion of GH in children?

    <p>Pituitary dwarfism</p> Signup and view all the answers

    What stimulates the release of growth hormone-releasing hormone (GHRH)?

    <p>Low blood levels of GH or glucose</p> Signup and view all the answers

    Acromegaly is a result of hypersecretion of which hormone in adults?

    <p>Growth hormone (GH)</p> Signup and view all the answers

    Which substance is known to stimulate the release of growth hormone besides hypothalamic hormones?

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

    Which condition is typically NOT associated with a deficiency of growth hormone in adults?

    <p>Increased muscle strength</p> Signup and view all the answers

    What is the role of diacylglycerol (DAG) in the PIP2-calcium signaling mechanism?

    <p>It activates protein kinases.</p> Signup and view all the answers

    How do calcium ions function as a second messenger in cellular signaling?

    <p>They bind to calmodulin, activating various enzymes.</p> Signup and view all the answers

    What distinguishes insulin signaling from other hormone signaling mechanisms?

    <p>It functions through a tyrosine kinase receptor.</p> Signup and view all the answers

    What is the main consequence of the receptor-hormone complex entering the nucleus?

    <p>It initiates DNA transcription to produce mRNA.</p> Signup and view all the answers

    Which of the following hormones operates without using a second messenger system?

    <p>Thyroid hormone</p> Signup and view all the answers

    Which component is a product of the hydrolysis of PIP2 by phospholipase C?

    <p>Both diacylglycerol and inositol trisphosphate</p> Signup and view all the answers

    What role does calmodulin play in the presence of calcium ions?

    <p>It binds calcium ions and activates other enzymes.</p> Signup and view all the answers

    What triggers the amplification of cellular responses in PIP2 signaling?

    <p>Calcium-bound calmodulin activating target enzymes</p> Signup and view all the answers

    Study Notes

    Chapter 11 Part A: Fundamentals of the Nervous System and Nervous Tissue

    • The nervous system is the master controlling and communicating system of the body
    • Nervous system cells communicate via electrical and chemical signals
    • These signals are rapid and specific, usually causing almost immediate responses
    • The nervous system has three overlapping functions:
      • Sensory input: gathering information from both inside and outside the body by sensory receptors
      • Integration: processing and interpreting sensory input
      • Motor output: activating effector organs (muscles and glands) to produce a response

    Organization of the Nervous System

    • The nervous system is divided into two principal parts:
      • Central nervous system (CNS): The brain and spinal cord, which act as integration and control centers
      • Peripheral nervous system (PNS): The portion outside the CNS, comprised mainly of nerves extending from the brain and spinal cord. This includes spinal nerves to and from the spinal cord, and cranial nerves connecting to and from the brain

    Peripheral Nervous System (PNS) Divisions

    • Sensory (afferent): Conveys impulses from skin, skeletal muscles, and joints to the CNS, and from visceral organs to the CNS
      • Somatic sensory fibers
      • Visceral sensory fibers
    • Motor (efferent): Transmits impulses from the CNS to effector organs (muscles and glands)
      • Somatic nervous system: responsible for conscious control of skeletal muscles
      • Autonomic nervous system: responsible for involuntary control of cardiac muscle, smooth muscle, and glands, divided into sympathetic and parasympathetic divisions

    Neuroglia

    • Nervous tissue histology:

      • Neuroglia (glial cells): supporting cells that surround and wrap delicate neurons
      • Neurons (nerve cells): excitable cells that transmit electrical signals

    • Neuroglia of the CNS: Four types support CNS neurons:

      • Astrocytes: most abundant, versatile, highly branched cells that cling to neurons and capillaries. Support and brace neurons. Play a role in exchanges between capillaries and neurons, guide migration of young neurons, control chemical environment around neurons, influence neuronal functioning, participate in information processing in brain
      • Microglial cells: small, ovoid cells with thorny processes that touch and monitor neurons. Migrate toward injured neurons. Can transform to phagocytize microorganisms and neuronal debris. Defensive cells in CNS
      • Ependymal cells: range in shape from squamous to columnar, may be ciliated, line the central cavities of the brain and spinal column, and form a permeable barrier between cerebrospinal fluid (CSF) and tissue fluid bathing CNS cells
      • Oligodendrocytes: branched cells, processes wrap CNS nerve fibers, forming insulating myelin sheaths in thicker nerve fibers.

    • Neuroglia of the PNS: Two types seen in PNS:

      • Satellite cells: surround neuron cell bodies in PNS, similar function to astrocytes in CNS
      • Schwann cells (neurolemmocytes): surround all peripheral nerve fibers and form myelin sheaths in thicker nerve fibers. Vital to regeneration of damaged peripheral nerve fibers; similar function as oligodendrocytes.

    Neurons

    • Neurons (nerve cells): structural units of the nervous system, large and highly specialized cells that conduct impulses

    • Special characteristics: extreme longevity, amitotic (with few exceptions), high metabolic rate (requiring continuous oxygen and glucose supplies), all have cell body and one or more processes

    • Neuron Cell Body (perikaryon or soma)

    • Biosynthetic center of a neuron that synthesizes proteins, membranes, and chemicals

    • Contains Rough ER (chromatophilic substance, or Nissl bodies), and a spherical nucleus with a nucleolus

    • Neuron Processes: Armlike processes that extend from cell body; CNS has both neuron cell bodies and their processes; PNS contains chiefly neuron processes (whose cell bodies are in CNS), including:

      • Tracts: bundles of neuron processes in CNS
      • Nerves: bundles of neuron processes in PNS
      • Dendrites: receptive regions that convey incoming messages toward cell body as graded potentials
      • Axon: the conducting region of a neuron that generates nerve impulses and transmits them to axon terminal

    • The axon structure:

      • Each neuron has one axon that starts at cone-shaped area called axon hillock
      • In some neurons, axons are short or absent; in others the neuron extends the length of the neuron
      • Long axons are called nerve fibers
      • Axons have occasional branches called axon collaterals, that branch profusely at their end (terminus). This often results in as many as 10,000 terminal branches
      • Distal endings are called axon terminals or terminal boutons

    • The axon: functional characteristics:

      • Axon is the conducting region of a neuron
      • Generates nerve impulses and transmits them along axolemma (neuron cell membrane) to axon terminal
      • Terminal: region that secretes neurotransmitters released into extracellular space
      • Can excite or inhibit neurons it contacts
      • Carries on many conversations with different neurons at same time

    • Myelin sheath

      • Composed of myelin, a whitish, protein-lipid substance
      • Functions to protect and electrically insulate axon, increase speed of nerve impulse transmission
      • Myelinated fibers: segmented sheath surrounds most long or large-diameter axons
      • Nonmyelinated fibers: do not contain sheath; conduct impulses more slowly

    Chapter 11 Part C: Fundamentals of the Nervous System and Nervous Tissue (Continued)

    Synapses

    • Synapses: junctions that mediate information transfer from neuron to neuron or from neuron to effector cell.
      • Presynaptic neuron: neuron conducting impulses toward synapse
      • Postsynaptic neuron: neuron, muscle cell, or gland cell transmitting signal away from synapse
      • Synaptic connections:
        • Axodendritic: between axon terminals and dendrites
        • Axosomatic: between axon terminals and cell body
      • Chemical synapses:
      • Specialized for release and reception of chemical neurotransmitters
      • Typically composed of two parts:
        • Axon terminal of presynaptic neuron: synaptic vesicles filled with neurotransmitter
        • Receptor region on postsynaptic neuron's membrane

    Transmission across synaptic cleft

    • Synaptic cleft prevents nerve impulses from directly passing from one neuron to the next. It is a chemical, not electrical, event.
    • Depends on the release, diffusion, and receptor binding of neurotransmitters.
      • Ensures one-directional communication between neurons

    Chemical Synapses steps:

    • AP arrives at axon terminal of presynaptic neuron
    • Voltage-gated Ca2+ channels open, and Ca2+ enters axon terminal
      • Ca2+ flows down electrochemical gradient from ECF (extracellular fluid) into inside of axon terminal
    • Ca2+ causes synaptic vesicles to release neurotransmitters
      • This causes synaptotagmin in vesicles react w/ SNARE proteins to control axon membrane fusion
      • The higher the impulse frequency, the more synaptic vesicles are released for greater effect on postsynaptic cell
    • Neurotransmitter diffuses across synaptic cleft and binds to specific receptors on postsynaptic membrane (usually chemically gated ion channels).
    • Binding of neurotransmitter opens ion channels, creating graded potentials
      • Binding causes receptor protein to change shape triggering ion channel opening. This can lead to excitatory or inhibitory events on postsynaptic cell.
    • Neurotransmitter effects are terminated as long as neurotransmitter is binding to receptors, so the process needs to be regulated. This happens through:
      • Reuptake by astrocytes or axon terminal
      • Degradation by enzymes
      • Diffusion away from synaptic cleft

    Electrical Synapses

    • Less common
    • Neurons are electrically coupled
      • Joined by gap junctions that connect cytoplasm of adjacent neurons
      • Communication is very rapid; often bidirectional.
      • Found in some brain regions responsible for eye movements or hippocampus in areas involved in emotions (often in embryonic tissue)

    Postsynaptic Potentials

    • Neurotransmitter receptors cause graded potentials that vary in strength based on amount of neurotransmitter and time it stays in cleft

      • EPSPs (excitatory postsynaptic potentials): creates graded potential depolarization due to greater Na+ influx than K+ efflux. They brings neuron closer to AP threshold
      • IPSPs (inhibitory postsynaptic potentials): creates graded potential hyperpolarization due to the flow of K+ out of cell or Cl- into the cell, moving neuron farther away from threshold.

    • Two types of Summations

      • Temporal summation-impulses arrive at same synapse in rapid-fire order, adding to each graded potential (influences whether or not it reaches threshold
      • Spatial summation-stimuli from different locations arrive nearly simultaneously at the same synapse, adding to the impact (influences whether or not it reaches threshold).

    • Action potentials: must be strong enough to reach a threshold voltage to produce APs, which is an all-or-none event.

    • Coding for stimulus intensity: CNS tells the difference between weak and strong stimuli based on AP frequency. Higher frequency equals stronger stimulus.

    • Refractory periods: time neurons cannot trigger another AP

      • Absolute refractory period: time from opening until resetting of Na+ channels (ensures each AP is an all-or-none event).
      • Relative refractory period: follows the absolute period where some K+ channels are still open (repolarization is happening) and threshold of AP generation is elevated.

    • Conduction velocity: rate APs propagate from axon to axon is determined by the axon's diameter and myelin presence.

      • Continuous conduction: slow propagation in nonmyelinated axons where each segment depolarizes then repolarizes sequentially.
      • Saltatory conduction: much faster propagation in myelinated axons, where impulses "jump" from gap to gap along the axon (Nodes of Ranvier).

    • CNS (central nervous system)

      • Clinical imbalance; MS (multiple sclerosis): autoimmune disease destroying CNS myelin sheaths; causes slow impulse conduction.

    Additional Information

    • Neurotransmitters: Chemical messengers released at the axon terminal that transmit signals across synapses.  Their effects are terminated in three primary ways: reuptake, enzymatic degradation or diffusion.

    Chapter 16 Part A: The Endocrine System

    • Endocrine system: acts with the nervous system to coordinate body functions

      • Hormones: long-distance chemical signals (carried in blood/lymph)
        • Exert effects on target cells with specific receptors
        • Alter target cell activity (e.g., changing membrane permeability)

    • Hormone release: controlled by negative feedback systems

      • Increased effects on target organs decrease further hormone release
      • Hormone levels typically remain within a certain narrow, desirable range
      • Endocrine gland stimulation occurs via humoral stimuli (changing ion/nutrient blood levels), neural stimuli (nerve fiber signals), or hormonal stimuli (other hormones released into the blood)
      • Nervous system modulation: can adjust hormone levels when needed. Modifies stimulation or inhibition of endocrine glands.

    • Types of Hormones:

      • Amino acid-based hormones:
        • Synthesized from amino acids.
        • Examples: Peptides, proteins, and amino acid derivatives
      • Steroid hormones:
        • Synthesized from cholesterol
        • Examples: Gonadal and adrenocortical hormones
      • Other type: eicosanoids, are considered hormones by some scientists, but mostly considered paracrines

    • Target Cell Specificity:

      • Target cells must have specific receptors for their corresponding hormone.
      • Amount of hormone can influence number of receptors
        • Up-regulation: increased receptor number
          • Response from target cells to low hormone levels
        • Down-regulation: decreased receptor number
          • Response from target cells to high hormone levels

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    Description

    Test your knowledge on the functions and characteristics of neuroglial cells in the central nervous system (CNS), including the effects of multiple sclerosis. This quiz covers topics such as microglial cells, oligodendrocytes, and ependymal cells, as well as related medical treatments and symptoms. Challenge yourself to see how well you understand these critical components of neurobiology.

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