Histology: Muscle and Nerves PDF

CMED 114 Dr. Audie Silva | September 27, 2024 HISTOLOGY: MUSCLE AND NERVES OUTLINE General Objectives 1 💡 Must Know 📚 Book 📜 Prev Trans 📣 Lectur...

CMED 114 Dr. Audie Silva | September 27, 2024 HISTOLOGY: MUSCLE AND NERVES OUTLINE General Objectives 1 💡 Must Know 📚 Book 📜 Prev Trans 📣 Lecturer Specific Objectives 1 General Objectives Characteristics and Types of Muscles 1 To know the development of the muscular system. Characteristics 1 To know the different types of muscle tissue. Pharyngeal Arch Muscle 2 SKELETAL MUSCLE 2 Specific Objectives Location 2 Discuss the embryonic origin of the muscular system. Describe the development of the three muscles. Organization 2 To describe the structure and function of the different Connective Tissue of Skeletal Muscle 2 types of muscle. Characteristics of Skeletal Muscle 3 To differentiate their appearance in the tissue section. Development of Skeletal Muscle 3 To describe the fiber–types of skeletal muscle. Skeletal Muscles 3 To define a motor unit. Motor Unit 4 To define myoepithelial cells and its function. The Neuromuscular Junction 4 To discuss muscular growth, dystrophy and repair. Differentiate common congenital anomalies associated with CARDIAC MUSCLE 4 development of muscles Location 4 Characteristics of Cardiac Muscle 5 Characteristics and Types of Muscles Development of Cardiac Muscle 5 Responsible for movement of the body and for change in the SMOOTH MUSCLES 6 size and shape of internal organs Location 6 Basis of movement is conversion of ATP to mechanical Characteristics of Smooth Muscle 6 energy by myofilaments Cells have excitable cell membrane important for Development of Smooth Muscle 6 propagation of initial stimuli Contractile Apparatus 6 Almost all muscle tissues are of mesodermal origin Common Muscular Disease (at birth) 6 Other Common Muscular Diseases 7 Characteristics NERVOUS TISSUE 8 Irritability- ability to respond to stimuli Nervous System Organization 8 Contractility- ability to shorten A. Central Nervous System 8 Extensibility- ability to stretch Elasticity- ability to regain its original length B. Peripheral Nervous System 8 C. Connective Tissue of Nervous Tissue 9 D. Fundamental Properties of Neurons 9 THREE TYPES OF MUSCLE Parts of the Neurons 9 A. Dendrites 9 B. Cell body/perikaryon 9 C. Axon 9 Skeletal muscle Classification of neurons 10 A. Structural Classification 10 B. Functional Classification 10 Neuroglial cells (not excitable) 10 A. Astrocytes 10 B. Microglial cells 10 C. Ependymal cells 10 Cardiac muscle D. Oligodendrocytes 10 E. Schwann cells 10 Synapse 11 CEREBRUM 11 CEREBELLUM 12 PURKINJE CELLS 12 SPINAL CORD 12 Smooth muscle Common Disorders of the Nervous System 13 SUPPLEMENTARY INFORMATION 13 REVIEW QUESTIONS 13 FREEDOM WALL 13 Transcribers: Jin, Y. & Ty. M. / Editors: Batay-an, S. & Marquina, R.A. 1 CMED 114 MUSCLE AND NERVE Pharyngeal Arch Muscle Connective Tissue of Skeletal Muscle Migration of myoblasts from the pharyngeal arches forms the muscles ENDOMYSIUM loose connective tissue that is found between of branchiomeric origin. each muscle fiber composed of collagenous and reticular fibers in which small capillaries MUSCLES CARTILAGE NERVE and neuronal branches course SUPPLY PERIMYSIUM connective tissue + fat + blood vessels and 1st pharyngeal muscles of mandible, trigeminal nerves group muscle fibers into fascicles arch mastication, malleus, nerve (mandibular arch) anterior belly of incus digastric muscle, EPIMYSIUM dense connective tissue that surrounds muscle mylohyoid, groups large blood vessels and nerves tensor tympani penetrate this layer to reach muscle fibers and tensor palatini **Each muscle fiber is surrounded by a basement membrane **Take note of the organization of muscles from Smallest to Largest Second muscles of facial stapes, facial nerve pharyngeal arch expression, styloid (hyoid arch) stapedius, process, stylohyoid, stylohyoid posterior belly of ligament, the digastric and lesser horn auricular muscle and upper part of the body of hyoid Third pharyngeal stylopharyngeus lower part of glossophary arch muscle the body and ngeal nerve greater horn of the hyoid bone 4th and 6th cricothyroid superior thyroid, pharyngeal levator, palatine laryngeal cricoid, arches pharyngeal, branch of arytenoids, constrictor, the vagus corniculate, intrinsic muscle nerve, cuneiform of the larynx recurrent cartilages of laryngeal the larynx branch of the vagus nerve SKELETAL MUSCLE Location Muscles of axial and appendageal skeleton visceral skeletal muscles Organization Muscle fibers run parallel and straight muscle tissue has many fasciculi Fasciculus - a bundle of muscle fibers (muscle cells) Myofiber - comprised of myofibrils in cross-section, the myofibrils are arranged in polygonal structure Myofibrils are bundles of myofilaments and consist of: ○ Thick Filaments - myosin and titan ○ Thin filaments - actin and tropomyosin-troponin complex Transcribers: Jin, Y. & Ty. M. / Editors: Batay-an, S. & Marquina, R.A. 2 CMED 114 MUSCLE AND NERVE Characteristics of Skeletal Muscle Consists of very long tubular cells called muscle fibers (sartorius muscle up to 30 cm, stapedius muscle only about 1 mm; diameters vary from 10 to 100 μm) Contain many peripherally placed nuclei, several hundred rather small nuclei with 1 or 2 nucleoli are located just beneath the plasma membrane Show cross-striations called striated muscle Innervated by the somatic nervous system Makes up the voluntary muscle Contractile Apparatus ○ responsible for striated appearance of the skeletal muscle ○ myofilaments: myosin and actin ○ contractile unit: sarcomere–the portion of a myofibril between two adjacent Z lines. ○ striations – alternate dark and light bands under microscope A band: stained dark →the myosin filaments I band: stained light →the actin filaments not overlapping myosin H band: myosin not overlapping actin Z disk: disk in the center of I band from which actin anchors and extends M line: myomesin and C protein, function to anchor the myosin Development of Skeletal Muscle MYOTOMES Myoblasts that form skeletal muscles of the trunk derived from mesoderm in myotome regions of somites Limb muscles develop from myogenic precursor cells in limb buds First indication of myogenesis: elongation of nuclei and cell bodies of mesenchymal cells as they differentiate into myoblasts Skeletal Muscles Thoracic and abdominal regions: myotome divides into EPIMERE (small dorsal portion) and HYPOMERE (large ventral portion) ○ Epimere – supplied by dorsal ramus of the spinal nerve; will develop into the extensor muscles of the back ○ Hypomere – supplied by the ventral ramus of the spinal nerve; will develop into the lateral and ventral flexor musculature Transcribers: Jin, Y. & Ty. M. / Editors: Batay-an, S. & Marquina, R.A. 3 CMED 114 MUSCLE AND NERVE Different bands of the muscles under microscope Muscles that control precise body movements may have as few as 2-3 muscle cells per motor neuron (e.g., eye muscles), while muscles that control gross body movements may have as many as 2,000 muscle cells per motor neuron (e.g., gluteal muscles) The Neuromuscular Junction 1. Excitable cells (muscle and nerve) make contact and communicate with one another at specialized regions called synapses 2. At each synapse a small gap, called the synaptic cleft, Motor Unit separates the two excitable cells Motor neuron – delivers the nervous stimulus that ultimately 3. Motor neuron, communicates with skeletal muscle cell, causes a muscle tissue to contract across the synaptic cleft via neurotransmitters Motor unit – refers to one motor neuron plus all of the 4. Synapse formed between motor neuron and skeletal muscle skeletal muscle cells it stimulates cell: neuromuscular (myoneural) junction A single motor neuron makes contact and thus stimulates 5. Motor neuron branches into clusters of bulb-shaped axon about 150 individual skeletal muscle cells terminals (end bulbs), each cluster forming a synapse with a All the cells contract and relax together, as a unit group of muscle cells (motor unit) Total strength of any particular muscle is determined by the 6. Region of muscle cell membrane that participates in the total number of motor units being used at any given time synapse with the axon terminal is the motor end plate CARDIAC MUSCLE Location Heart, base of great vessels (aorta and pulmonary arteries), pulmonary veins, superior and inferior vena cava Transcribers: Jin, Y. & Ty. M. / Editors: Batay-an, S. & Marquina, R.A. 4 CMED 114 MUSCLE AND NERVE Characteristics of Cardiac Muscle One centrally placed nucleus; nuclei oval, rather pale and located centrally in the muscle cell which is 10 - 15 μm wide Cells exhibit cross-striations; contractile apparatus are similar to skeletal muscles Cells are short, narrow with branching 1. Innervated by the autonomic nervous system, which adjusts the force generated by the muscle cells and the frequency of the heartbeat 2. Involuntary striated muscle 3. Intercalated disks: specialized attachment sites between adjacent cardiac cells a. a. fascia adherens (adhering junctions): major constituent of the transverse component of the intercalated disk; responsible for its staining in routine H&E preparations b. maculae adherents (desmosomes): bind the individual muscle cells to one another; help prevent the cells from pulling apart under the strain of regular repetitive contractions; serves to reinforce the adhering junctions b. c. gap junctions: constitute the major structural element of the lateral component of the intercalated disk; provides ionic continuity between adjacent cardiac muscle cells Development of Cardiac Muscle Develops from splanchnic mesoderm surrounding the developing heart tube Cardiac myoblasts differentiate from the primordial myocardium Myoblasts adhere to each other, but the intervening cell membranes do not disintegrate; these areas of adhesion give rise to intercalated discs Rheumatic Disease (Picture below) Transcribers: Jin, Y. & Ty. M. / Editors: Batay-an, S. & Marquina, R.A. 5 CMED 114 MUSCLE AND NERVE SMOOTH MUSCLES Contractile Apparatus Location Myofilaments: ❖ Blood vessels, tunica media, ducts, GI system, respiratory ○ Actin and myosin system, urogenital system, etc. ○ No striation Microfilaments ○ not regularly arranged, oriented obliquely to the long axis of the cell ○ Actin filaments attach to sarcolemma via dense bodies, which function as Z disk analogues ○ Gap junctions are present for united contraction ○ Calcium regulation of contraction At the level of the thick filament Calcium-calmodulin complex leads to phosphorylation of myosin, → contraction Characteristics of Smooth Muscle Shape: Short, elongate fusiform cells Nucleus: Mononucleated, centrally placed Lack T Tubule System: have a membrane system of sarcolemma invaginations that are analogous to T system to deliver Ca2+ to the cytoplasm ○ (Note: Sarcolemma - cytoplasmic membrane of the muscle cells) Longitudinal section (fusiform) vs Cross Section (circular) (Note: Smooth muscle - fusiform shape. Cardiac - Branched) Common Muscular Disease (at birth) Development of Smooth Muscle Congenital arthrogryposis Smooth muscle differentiates from splanchnic mesoderm ○ failure of normal muscle development may be surrounding endoderm of the primordial gut and its widespread, leading to immobility of multiple joints derivatives ○ Cause: encompasses both neurogenic and Smooth muscle in walls of many blood and lymphatic primary myopathic diseases. The involved vessels arises from somatic mesoderm muscles are replaced partially or completely by fat Muscles of the iris (sphincter and dilator pupillae) and and fibrous tissue. myoepithelial cells in mammary and sweat glands are Congenital torticollis derived from ectoderm ○ fixed rotation and tilting of the head due to fibrosis Myoblasts become spindle-shaped but do not fuse; remain and shortening of the sternocleidomastoid muscle mononucleated on one side. ○ Some cases of torticollis (Wryneck) result from tearing of fibers of the sternocleidomastoid muscle during childbirth. Transcribers: Jin, Y. & Ty. M. / Editors: Batay-an, S. & Marquina, R.A. 6 CMED 114 MUSCLE AND NERVE Other Common Muscular Diseases Myasthenia Gravis Muscular Dystrophy ○ an autoimmune disease ○ genetic disease, a group of muscle diseases ○ muscle weakness and fatigue caused by cause the damage of muscle fiber breakdown of the neuromuscular junction. ○ no specific cure for it and the symptoms include ○ the brain does not have control over these weakness, immobility and imbalance. muscles. ○ Types ○ can cause drooping eyelids, difficulty in breathing Duchenne Muscular Dystrophy or swallowing and loss of facial muscle control. (DMD): A genetic disorder characterized ○ Treatment: medication or surgery. by progressive muscle degeneration and weakness, caused by mutations in the Amyotrophic Lateral Sclerosis (ALS) / Lou Gehrig’s dse dystrophin gene. ○ a very serious neurodegenerative disease; also Myotonia: A symptom characterized by known as Lou Gehrig’s disease. delayed relaxation of muscles after ○ progressive and leads to the destruction of contraction, often seen in myotonic neurons that control voluntary muscles, eventually dystrophy or other neuromuscular causing loss of muscle function conditions. ○ Early signs: dyspnea (difficulty breathing), difficulty Becker Muscular Dystrophy (BMD): in speaking (dysarthria), and difficulty swallowing Similar to Duchenne but less severe; (dysphagia). also caused by mutations in the ○ Paralysis: advanced stage symptom. dystrophin gene, leading to progressive muscle weakness. Mitochondrial Myopathies Limb-Girdle Muscular Dystrophy ○ Mitochondrial dysfunction leads to insufficient (LGMD): A group of disorders that energy production in cells, especially affecting cause weakness and wasting primarily muscles and other energy-dependent tissues. This in the muscles of the shoulders and hips results in muscle weakness, deafness, blindness, (limb-girdle area). arrhythmia (irregular heartbeat), and potentially heart failure. Cerebral Palsy mitochondria get damaged → weakness ○ one of the most common congenital motor of muscles, deafness, blindness, disabilities in children, affecting posture, balance, arrhythmia and heart failure and motor functions. ○ can cause seizures, dementia, vomiting and ○ associated with loss or abnormal muscle tone, droopy eyelids (ptosis) which affects movement control. This damage ○ nausea, headache and difficulty in breathing are often occurs either during pregnancy or childbirth also commonly reported symptoms. due to complications such as lack of oxygen to the brain. Rhabdomyolysis ○ rapid destruction of the skeletal muscle Fibrodysplasia Ossificans Progressiva ○ muscle fibers break down into myoglobin which ○ soft tissue hardens and becomes bone-like gets excreted in urine permanently. ○ muscle weakness, pain and stiffness ○ bone grows between joints and movements get ○ Treatment is possible when it is detected in early permanently restricted. stages by means of IV fluids, dialysis or ○ no effective cure available. only pain management hemofiltration. can be done through medication Polymyositis Dermatomyositis ○ degenerative and inflammatory in nature ○ inflammation in both the muscles and skin, leading ○ involves chronic inflammation that leads to muscle to muscle weakness and distinctive skin rashes. degeneration and weakness. ○ an autoimmune disease harming the connective ○ affects connective tissues throughout the body, tissue and weakening the muscles. leading to widespread muscle weakness, and in ○ no cure for this condition, but the progression can some cases, muscle atrophy (shrinking of be controlled by taking corticosteroids and muscles). immunosuppressive drugs. Fibromyalgia Compartment Syndrome ○ a chronic and debilitating muscle disorder ○ the blood vessels, muscles and nerves get ○ causes pain, fatigue, tenderness and stiffness of compressed in a closed area, which ends up in muscles cutting off the oxygen supply. ○ considered a genetic disorder and affects more ○ The result is tissue death which can even lead to women than men. paralysis ○ Immediate treatment is fasciotomy. ○ pressure on muscles will be released after the surgery Transcribers: Jin, Y. & Ty. M. / Editors: Batay-an, S. & Marquina, R.A. 7 CMED 114 MUSCLE AND NERVE Myotonia Tendonitis ○ muscles relax slowly after stimulation or ○ tendon gets inflamed or irritated, inflammation can contraction occur in any tendon of the body ○ causes problem when grip is released and when ○ seen more commonly in wrists, elbows, shoulders you get up from sitting or sleeping position and heels. ○ Treatment: medication, physiotherapy and ○ causes pain, mild swelling, tenderness anticonvulsants. ○ treated with pain relievers, rest and ice compress. Myofascial Pain Syndrome NERVOUS TISSUE ○ a chronic pain disorder of the muscles Learning Objectives: ○ causes aching and burning sensation on trigger 1. Know the components of tissue in the central and points which are sensitive spots of muscles peripheral nervous systems ○ cause joint stiffness, knot in the muscles and 2. Understand the meaning of terms gray matter and sleeplessness due to pain white matter ○ managed by corticosteroids, injections of 3. Relate nerve function to the properties of neurons botulinum, massage and physiotherapy. and their cell processes: axons and dendrites Rotator Cuff Tear Nervous System Organization ○ rigorous, fast or hard movements (baseball and tennis) can cause a tear in the tendon which causes pain and reduced mobility ○ torn tendon can be repaired by surgery Muscle Cramps ○ can occur suddenly and involuntarily, in one or more muscles ○ can happen late night or after exercising and can be caused due to a variety of reasons, lasting for seconds to minutes ○ Gentle massage helps temporarily. Sprains and Strains ○ twist or pull in the ligaments (sprain), muscles or tendons (strain) which can either be sudden or over a period of time may cause sprains and strains A. Central Nervous System ○ back and hamstring muscles are commonly nerve cells: neuronal cell bodies and their dendrites and affected axons (both myelinated and unmyelinated) ○ cause pain, swelling and difficulty in movement supporting cells (the neuroglia): oligodendroglia, astrocytes ○ rest and ice compress are advised. It’s important and microglia to keep the area immobile and take medicine for meninges: dura, arachnoid, and pia the pain. blood vessels Talipes B. Peripheral Nervous System ○ also known as clubfoot neurons organized into clusters called ganglia ○ a congenital deformity in which one or both feet supporting cells including satellite cells associated with the are twisted out of shape or position ganglionic neurons and Schwann cells which form the myelin ○ typically involves abnormal positioning of the foot sheath and ankle, leading to difficulty walking or standing. connective tissue elements (endoneurium, perineurium and epineurium) Pes Planus blood vessels ○ also known as flat feet in which the muscles supporting the arch weaken and cause flattening Nervous tissue is made up of neurons and neuroglial cells of the arch due to the downward pressure. Neuroglial cells are involved with support, nutrition, and ○ 2 types of flat feet: rigid and flexible. defense of nervous system Rigid flat feet: often causes pain and Nerve - made up of many nerve cell fibers (neurons) bound stiffness, and treatment may involve together by connective tissue orthotic devices, physical therapy, or Neuron - the functional unit of the nervous system, transmit even surgery in severe cases. impulses Flexible flat feet: typically painless and symptom-free, and can be treated with corrective footwear, exercise, and massage to strengthen the muscles supporting the arch. Transcribers: Jin, Y. & Ty. M. / Editors: Batay-an, S. & Marquina, R.A. 8 CMED 114 MUSCLE AND NERVE C. Connective Tissue of Nervous Tissue Axon hillock Epineurium - sheath of dense connective tissue surrounds located at the junction where the axon originates from the the nerve perikaryon (the cell body) Perineurium - surrounds bundles of nerve fibers ○ Short region: The axon hillock is a small, ○ Blood vessels of various sizes can be seen in the cone-shaped area at the base of the axon. epineurium ○ Axon origin: It is the site where the axon starts, Endoneurium - consists of a thin layer of loose connective and it plays a crucial role in initiating action tissue, surrounds individual nerve fibers potentials (electrical signals). ○ important for integrating incoming signals from the dendrites and determining whether or not an action potential will be generated and transmitted down the axon. Axolemma plasma membrane that covers the axon facilitates the transmission of nerve impulses by managing ion exchange during action potentials. Axoplasm neuronal cytoplasm that extends into the axon, providing the necessary environment for axonal function. involved in the transport of materials (such as proteins and organelles) between the cell body and the axon terminals, supporting the overall function of the neuron Initial segment the point between the axon hillock and the point at which myelination begins. Cross section vs Longitudinal Section 💡 Nuclei in peripheral nerve - more elongated / “serpentine/snack-like” D. Fundamental Properties of Neurons Excitability – can react to stimulus by generation of an impulse Axon is myelinated so that signals can travel faster Conductivity – impulse generated can be propagated Parts of the Neurons A. Dendrites multiple elongated processes the main receptive domain. B. Cell body/perikaryon trophic center. contain granules called Nissl bodies found in the cytoplasm of the cell body. Synthesis of neurotransmitters, proteins, trophic factors. an integration domain Microscopic view of the neuron C. Axon generates/conducts impulses to other nerve cells. forms the transmission domain Distal portion of the axon forms the terminal arborization. Each branch terminates in a dilatation called boutons. Transcribers: Jin, Y. & Ty. M. / Editors: Batay-an, S. & Marquina, R.A. 9 CMED 114 MUSCLE AND NERVE Classification of neurons A. Structural Classification grouped structurally according to the number of processes extending from their cell body. Multipolar polar = end pole 3+ processes, most common neuron type (>99%) Major neuron type in CNS Bipolar spindle shaped with a dendrite at one end and an axon at the other Unipolar Generation of nerve impulse have only a single process or fiber which divides close to the At rest, membrane of nerve cells is positively charged on the cell body into two main branches (axon and dendrite) outside and negatively charged on the inside → called resting potential Multipolar - motor and interneurons When activated, ion channels open and there is differential Bipolar neuron - ear and eye efflux/influx of ions creating an electrical potential (an Unipolar - most of the body sensory neurons impulse) B. Functional Classification Neuroglial cells (not excitable) sensory or afferent A. Astrocytes motor or efferent nutritional and physical support scarring in case of neuronal damage regulates cerebral blood flow B. Microglial cells belong to mononuclear phagocyte system in the CNS C. Ependymal cells line ventricles and provide physical support D. Oligodendrocytes myelination in the CNS E. Schwann cells myelination in the PNS Transcribers: Jin, Y. & Ty. M. / Editors: Batay-an, S. & Marquina, R.A. 10 CMED 114 MUSCLE AND NERVE Synapse Communication between neurons ○ Each synapse has 1. Presynaptic area 2. Synaptic cleft 3. Post synaptic area Electrical impulse is carried via chemical messengers in the synapse then reconverted to electrical impulse in the postsynaptic area ANATOMY OF THE BRAIN CEREBRUM Cerebrum - Gray matter outside and white matter inside Transcribers: Jin, Y. & Ty. M. / Editors: Batay-an, S. & Marquina, R.A. 11 CMED 114 MUSCLE AND NERVE PURKINJE CELLS Purkinje cells separates Gray and White Matter in the Cerebellum SPINAL CORD Spinal Cord - Gray Matter Inside, White Matter Outside CEREBELLUM Cerebellum - Gray matter outside and white matter inside Surface of brain and spinal cord has adherent meninges (Pia mater) Transcribers: Jin, Y. & Ty. M. / Editors: Batay-an, S. & Marquina, R.A. 12 CMED 114 MUSCLE AND NERVE Common Disorders of the Nervous System Trauma 5. What key difference exists between oligodendrocytes Infections and Schwann cells in their myelination capabilities? Degeneration A) Oligodendrocytes myelinate in the peripheral nervous Structural Defects system, while Schwann cells do so in the central nervous Tumors system. Blood Flow disruption B) Schwann cells can myelinate multiple axons, while Autoimmune disorders oligodendrocytes can only myelinate one. C) Oligodendrocytes myelinate multiple axons, while Schwann cells myelinate only one. Vascular stroke, transient ischemic attack (TIA), D) There is no difference; both types perform the same disorders subarachnoid hemorrhage, subdural hemorrhage and hematoma, and extradural hemorrhage function in different locations. Infections meningitis, encephalitis, polio, and epidural 6. In a study on synaptic transmission, a student observes abscess the process of neurotransmitter release from the presynaptic neuron. What best describes what happens Structural brain or spinal cord injury, Bell's palsy, cervical next? disorders spondylosis, carpal tunnel syndrome, brain or A) The neurotransmitter directly generates an electrical spinal cord tumors, peripheral neuropathy, and impulse in the presynaptic neuron. Guillain-Barré syndrome B) The neurotransmitter diffuses across the synaptic cleft to bind with receptors on the postsynaptic neuron. Functional headache, epilepsy, dizziness, and neuralgia C) The neurotransmitter remains in the synaptic cleft disorders indefinitely. D) The presynaptic neuron absorbs the neurotransmitter Degeneration Parkinson disease, multiple sclerosis, amyotrophic lateral sclerosis (ALS), Huntington chorea, and after it is released. Alzheimer disease ANSWERS AND RATIONALE SUPPLEMENTARY INFORMATION 10-minute Neuroscience - 1. A https://www.youtube.com/watch?v=5p9ucgRDie8 2-Minute Neuroscience: The Neuron- 2. Answer: B) Bipolar https://www.youtube.com/watch?v=6qS83wD29PY Rationale: Bipolar neurons have one dendrite and one axon extending from the cell body. They are typically found in sensory systems, such REVIEW QUESTIONS as the retina of the eye. 1. What do you call a bundle of muscle fibers (muscle cells)? A) Fasciculus 3. Answer: C) Astrocytes B) Myofiber Rationale: Astrocytes provide structural and nutritional support to C) Myofilament neurons and play a critical role in regulating blood flow in the brain, making them key players in maintaining the health of the central 2. A researcher is studying a new type of neuron found in nervous system. the retina that has one dendrite and one axon extending from the cell body. What type of neuron is this most 4. Answer: A) The inside of the membrane is negatively charged likely to be? compared to the outside. A) Multipolar Rationale: At resting potential, the inside of a neuron is negatively B) Bipolar charged relative to the outside due to the distribution of ions, primarily C) Unipolar sodium and potassium, across the membrane. D) Pseudounipolar 5. Answer: C) Oligodendrocytes myelinate multiple axons, while 3. During an experiment, a scientist observes that a certain Schwann cells myelinate only one. glial cell type provides support and nourishment to Rationale: Oligodendrocytes are found in the central nervous system neurons while also regulating blood flow in the brain. and can myelinate multiple axons, while Schwann cells are found in the Which type of cell is she most likely observing? peripheral nervous system and myelinate only one axon. A) Microglial cells B) Ependymal cells 6. Answer: B) The neurotransmitter diffuses across the synaptic C) Astrocytes cleft to bind with receptors on the postsynaptic neuron. D) Oligodendrocytes Rationale: In synaptic transmission, neurotransmitters released from the presynaptic neuron diffuse across the synaptic cleft and bind to 4. Which of the following correctly describes the resting receptors on the postsynaptic neuron, initiating a response. potential of a neuron? A) The inside of the membrane is negatively charged FREEDOM WALL compared to the outside. “May the God of hope fill you with all joy and peace as you trust in Him, B) It is established by the high concentration of sodium ions so that you may overflow with hope by the power of the Holy Spirit.” inside the cell. Romans 15:13 C) It occurs only when the neuron is actively firing an impulse. Transcribers: Jin, Y. & Ty. M. / Editors: Batay-an, S. & Marquina, R.A. 13