Neuroscience Chapter on Glial Cells and Functions
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Which of the following is NOT a function of astrocytes?

  • Produce myelin sheath (correct)
  • Help destroy invading microorganisms
  • Control chemical environment around neurons
  • Anchor neurons to capillaries

    • Axons transmit messages away from the cell body in a two-directional manner.

    False (B)

    What is the name of the gaps between Schwann cells in the PNS?

    Nodes of Ranvier

    The ______ nervous system controls involuntary actions like heart rate and digestion.

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

    Match the following glial cells with their primary function in the CNS:

    <p>Astrocytes = Anchor neurons to capillaries Microglial cells = Destroy invading microorganisms Ependymal cells = Circulate cerebrospinal fluid Oligodendrocytes = Produce myelin sheath</p> Signup and view all the answers

    Which of the following is a characteristic of the somatic nervous system?

    <p>Carries impulses to skeletal muscles (A)</p> Signup and view all the answers

    Satellite cells are only found in the CNS.

    <p>False (B)</p> Signup and view all the answers

    What type of neuroglia is responsible for forming the myelin sheath in the PNS?

    <p>Schwann cells are the glial cells that form the myelin sheath in the PNS. They provide structural support and insulate axons, which allows for faster transmission of nerve impulses in the PNS.</p> Signup and view all the answers

    A synapse is a specialized junction that mediates the transfer of information between ______.

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

    What is the primary function of a neurotransmitter?

    <p>To transmit signals from one neuron to another (C)</p> Signup and view all the answers

    A bundle of axons in the peripheral nervous system is called a tract.

    <p>False (B)</p> Signup and view all the answers

    What is demyelination and what are its potential implications?

    <p>Demyelination is the loss or damage of the myelin sheath that insulates axons. This can lead to slower or disrupted nerve signal transmission, causing neurological disorders like multiple sclerosis.</p> Signup and view all the answers

    Match the following brain structures with their corresponding descriptions.

    <p>Cerebral cortex = The outer layer of the cerebrum, responsible for higher cognitive functions. White matter = Consists mainly of myelinated axons, facilitating communication between different brain regions. Gray matter = Contains primarily neuronal cell bodies, dendrites, and unmyelinated axons. Convolutions = Folds and grooves on the surface of the brain, increasing its surface area and neuronal capacity.</p> Signup and view all the answers

    Neuroplasticity refers to the brain's ability to adapt and change in response to experience or injury.

    <p>True (A)</p> Signup and view all the answers

    Which of the following is NOT a function of the meninges?

    <p>Produce cerebrospinal fluid (D)</p> Signup and view all the answers

    Describe the three layers of the meninges from superficial to deep.

    <p>The three layers of the meninges are: 1. Dura mater - the outermost, thickest layer, 2. Arachnoid mater - the middle layer with the subarachnoid space containing CSF, and 3. Pia mater - the innermost layer that closely adheres to the brain surface.</p> Signup and view all the answers

    The cerebellum is responsible for controlling muscle coordination and balance.

    <p>True (A)</p> Signup and view all the answers

    What percentage of the brain mass does the cerebellum constitute?

    <p>11%</p> Signup and view all the answers

    The cerebellum receives information from the ______, eye, ear, and the muscles of the body.

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

    Which of the following is NOT a function of the cerebellum?

    <p>Regulation of heart rate (D)</p> Signup and view all the answers

    Match the following brain structures with their corresponding functions:

    <p>Cerebellum = Controls muscle coordination and balance Reticular activating system (RAS) = Keeps the cerebral cortex conscious and alert Broca's area = Speech production Wernicke's area = Understanding spoken and written language</p> Signup and view all the answers

    What happens to individuals with lesions in Broca's area?

    <p>They can understand words but cannot speak.</p> Signup and view all the answers

    The reticular formation filters out repetitive, familiar, or weak stimuli.

    <p>True (A)</p> Signup and view all the answers

    Severe injury to the brain stem can result in ______.

    <p>permanent unconsciousness (coma)</p> Signup and view all the answers

    Which of the following is NOT a function of the diencephalon?

    <p>Controlling voluntary muscle movements (B)</p> Signup and view all the answers

    The cerebellum is primarily responsible for speech and language processing.

    <p>False (B)</p> Signup and view all the answers

    What are the three main components of the brainstem?

    <p>The three main components of the brainstem are the pons, midbrain, and medulla oblongata.</p> Signup and view all the answers

    What sensory information does the lateral spinothalamic tract carry?

    <p>Pain and temperature (B)</p> Signup and view all the answers

    The _____________ fissure divides the cerebrum into left and right hemispheres.

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

    The spinothalamic tract is a descending pathway.

    <p>False (B)</p> Signup and view all the answers

    What is the primary function of the Premotor Cortex?

    <p>Plans movement</p> Signup and view all the answers

    Match the brain structures with their primary functions:

    <p>Cerebrum = Analysis of sensory input, memory, learning, cognitive thought Cerebellum = Coordinates muscle control, maintains balance and equilibrium, fine tunes movements Diencephalon = Enables speech, judgement, thinking, reasoning, problem-solving, also function in vision, hearing, touch, and other senses Brainstem = Vital functions; breathing, consciousness, blood pressure, heart rate, sleep</p> Signup and view all the answers

    Which of the following arteries supply the brain with blood?

    <p>Both A and B (C)</p> Signup and view all the answers

    The ______ is responsible for understanding spoken language.

    <p>Wernicke’s area</p> Signup and view all the answers

    What is the function of the Circle of Willis?

    <p>The Circle of Willis is a network of interconnected blood vessels that ensures continuous blood flow to the brain, even if one of the main arteries is blocked.</p> Signup and view all the answers

    Match the following brain areas with their respective functions:

    <p>Premotor Cortex = Plans movement Broca’s Area = Plans speech, directs muscles of speech production Frontal eye field = Controls eye movement Wernicke’s area = Understanding spoken language</p> Signup and view all the answers

    The transverse cerebral fissure separates the cerebrum from the brainstem.

    <p>False (B)</p> Signup and view all the answers

    A decrease in the neurotransmitter ______ can lead to disruptions in movement coordination.

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

    The corpus striatum is responsible for producing smooth, purposeful movements.

    <p>True (A)</p> Signup and view all the answers

    What is the main function of the thalamus?

    <p>Relaying sensory information (D)</p> Signup and view all the answers

    Name two factors that influence the transformation of short-term memories into long-term memories.

    <p>Rehearsal and linking new information with old memories</p> Signup and view all the answers

    Match the brain structures with their corresponding functions:

    <p>Amygdaloid body = Processing emotions, particularly fear and aggression Flocculonodular lobe = Maintaining balance and coordinating movement Hypothalamus = Controlling vital functions like hunger, thirst, and body temperature Thalamus = Relaying sensory information to the cerebral cortex</p> Signup and view all the answers

    What is the role of the reticular activating system?

    <p>Preventing sensory overload (B)</p> Signup and view all the answers

    What are orexins and how do they affect the sleep-wake cycle?

    <p>Orexins are chemicals released during sleep that stimulate reticular neurons, causing arousal and promoting wakefulness.</p> Signup and view all the answers

    Parkinson's Disease is caused by an increase in dopamine levels in the brain.

    <p>False (B)</p> Signup and view all the answers

    Study Notes

    Nervous System Functions

    • The nervous system is composed of the central nervous system (CNS) and the peripheral nervous system (PNS).
    • The CNS includes the brain and spinal cord, which act as control centers.
    • The PNS includes cranial nerves and spinal nerves, which carry impulses to and from the CNS, connecting it to the rest of the body.

    Nervous System Organization

    • The PNS has sensory (afferent) and motor (efferent) divisions.
    • The sensory division transmits impulses from sensory receptors to the CNS.
    • The motor division transmits impulses from the CNS to effectors (muscles and glands).
    • The motor division includes the somatic nervous system (voluntary movements to skeletal muscles) and autonomic nervous system (involuntary movements to cardiac, smooth muscle, and glands.)
    • The autonomic nervous system further divides into sympathetic (mobilizes body systems during activity) and parasympathetic (conserves energy and promotes housekeeping functions during rest) divisions.

    Nervous Tissue Types

    • Ganglion: A cluster of cell bodies in the peripheral nervous system (PNS).
    • Nucleus: A cluster of cell bodies in the central nervous system (CNS).
    • Nerve: A bundle of axons in the PNS.
    • Tract: A bundle of axons in the CNS.
    • Gray matter: Unmyelinated axons, cell bodies, dendrites and terminals, and blood vessels, primarily in the CNS.
    • White matter: Myelinated axons and blood vessels, predominantly in the CNS.

    Neuron Structure

    • Dendrites: Receive signals from other neurons.
    • Cell body: Contains the cell nucleus.
    • Nucleus: Contains the genetic material of the neuron cell.
    • Axon: Conducts electrical impulses along the neuron.
    • Myelin sheath: Insulates the axon to speed up transmission of electrical signals.
    • Axon terminal: Transmits signals to other neurons or effector cells.

    Axon's Functional Characteristics

    • Axons generate and transmit nerve impulses.
    • When a nerve impulse reaches the axon terminal, neurotransmitters are released into the extracellular space.
    • Neurotransmitters transmit signals, either exciting or inhibiting a nearby neuron.

    Neuroglia

    • Astrocytes are the most abundant neuroglia in the CNS. Their functions include anchoring neurons to capillaries, controlling the chemical environment around neurons, and maintaining the blood-brain barrier.
    • Microglial cells are immune cells of the CNS. They help destroy invading microorganisms near neurons and monitor their health.
    • Ependymal cells circulate cerebrospinal fluid to cushion the brain and spinal cord.
    • Oligodendrocytes wrap around nerve fibers, forming myelin sheaths.
    • Satellite cells surround cell bodies in the PNS, acting similar to astrocytes in the CNS.
    • Schwann cells surround all nerve fibers in the PNS, creating myelin sheaths (similar to oligodendrocytes) and play a vital role in regenerating damaged peripheral nerves.

    Efferent vs. Afferent Division of the PNS

    • Efferent (motor) signals travel from the central nervous system (CNS) to effector organs.
    • Somatic nervous system controls voluntary skeletal muscle activity.
    • Autonomic nervous system controls involuntary activity of smooth muscles, cardiac muscles, and glands.
    • Afferent (sensory) signals travel to the CNS from sensory organs.
    • Somatic sensory fibers carry impulses from skin, muscles, and joints.
    • Visceral sensory fibers transmit impulses from visceral organs.

    Myelin Sheath Importance

    • Myelin sheaths are whitish, fatty (protein-lipid), segmented covers around many nerve fibers.
    • They protect and electrically insulate nerve fibers.
    • They significantly increase the speed of nerve impulse transmission (action potentials).
    • Non-myelinated fibers conduct impulses more slowly.

    Multiple Sclerosis

    • Multiple sclerosis is an autoimmune disorder that results in demyelination of CNS nerve fibers.
    • Demyelination leads to hardened patches (sclerosis) in the brain and spinal cord.
    • This disrupts communication between the CNS and the rest of the body.

    Membrane Potentials

    • Neurons communicate via electrochemical signals.
    • The cell membrane presents resistance to current flow.
    • Action potentials (nerve impulses) are electrochemical signals occurring over longer distances.
    • Action potentials are dependent on the existence of a resting membrane potential.

    Action Potentials

    • Stimuli at dendritic nerve endings trigger ion channel openings, enabling local ion flow across the plasma membrane.
    • If the inside of the plasma membrane becomes more positive than the resting membrane potential (~-55mV), an action potential is triggered (depolarization).
    • If the membrane potential doesn't reach threshold, no action potential is triggered.
    • Action potentials propagate along the axon.
    • When an action potential reaches the axon terminal, it triggers neurotransmitter release to neighboring neurons.

    Synapse Stages

    • Nerve impulses arrive at the axon terminal.
    • Calcium channels open, releasing calcium into the terminal.
    • Neurotransmitters are released.
    • Neurotransmitters bind to receptors on the postsynaptic neuron.
    • A postsynaptic potential is formed, potentially triggering an action potential in the postsynaptic neuron.

    Chemical Synapse

    • A synapse is a specialized junction between neurons.
    • It facilitates the transfer of information between neurons.
    • Action potential arriving at the axon terminal triggers calcium influx.
    • Calcium influx triggers neurotransmitter release into the synaptic cleft.
    • Neurotransmitters bind to receptors on the postsynaptic membrane.
    • This binding initiates a response in the postsynaptic neuron.

    Nerve vs. Tract

    • A nerve is a bundle of axons in the PNS.
    • A tract is a bundle of axons in the CNS.

    Demyelination

    • Stages of demyelination include:
    • Progressive decline
    • Demyelination
    • No remyelination
    • Remyelination phase
    • Functional recovery

    White Matter vs. Gray Matter

    • White matter consists mainly of myelinated axons.
    • Gray matter includes primarily unmyelinated axons, cell bodies, dendrites, axon terminals, and blood vessels.

    Neuroplasticity

    • Neuroplasticity is the brain's ability to compensate for damage or disease by forming new connections.

    Meninges

    • Meninges are protective membranes covering and protecting the CNS.
    • They protect blood vessels and enclose venous sinuses.
    • Dura mater (strongest membrane), arachnoid mater (middle), and pia mater (innermost) form layers of protection that contain cerebrospinal fluid (CSF).

    Cerebrospinal Fluid (CSF)

    • CSF cushions the brain and spinal cord.
    • It reduces the brain's weight by 97%.
    • CSF is a watery solution derived from blood plasma.

    Blood-Brain Barrier (BBB)

    • The BBB helps maintain a stable environment for the brain.
    • Substances from the blood must pass through the continuous endothelium of capillary walls before entering neurons.
    • Tight junctions between capillary endothelial cells control passage/diffusion.
    • Simple diffusion allows lipid-soluble substances to freely pass through cell membranes.
    • Specific transport mechanisms facilitate the movement of critical substances (like glucose, amino acids).

    Blood Supply to the Brain

    • The brain is supplied by two internal carotid arteries and two vertebral arteries.
    • These arteries form a circle at the base of the brain called the Circle of Willis.
    • This arrangement ensures a backup blood supply if part of the pathway is blocked.

    Traumatic Brain Injuries

    • Concussion: Temporary alteration in brain function.
    • Contusion: Permanent brain damage.
    • Hemorrhage: Pressure from blood forces brain stem through magnum foramen, often leading to death.
    • Cerebral edema: Swelling of brain tissue.

    Cerebrovascular Accidents (CVAs)

    • Strokes/Ischemic events in which blood flow to the brain is blocked, reducing the supply of oxygen and nutrients to brain cells.

    Brain Regions (4)

    • Cerebrum: Initiates and coordinates movement, controls temperature, enables speech, judgement, thinking, and reasoning.
    • Diencephalon: Includes thalamus (relay center), hypothalamus (controls endocrine and autonomic nervous system), and epithalamus (pineal gland that secretes melatonin).
    • Cerebellum: Controls muscle coordination, skilled movement, balance, and equilibrium.
    • Brainstem: Consists of midbrain, pons, and medulla oblongata. It handles vital bodily functions.

    Major Landmarks: Fissures and Sulci

    • Longitudinal fissure: Divides the cerebrum into left and right hemispheres.
    • Transverse cerebral fissure: Separates the cerebrum from the cerebellum.

    Cerebral Cortex Regions

    • White matter: Consists of myelinated fibers that connect different areas of the cortex.
    • Gray matter: (cortex) responsible for higher-level functions like analysis of sensory input, memory formation, learning, cognitive functions, voluntary movements, memory and language.
    • Basal nuclei: Subcortical nuclei that help regulate the intensity of slow and stereotyped movements.

    Motor Cortex

    • Premotor cortex: Involved in planning movements.
    • Primary motor cortex: Carries out commands from the premotor cortex.
    • Broca's area: Involved in speech production.
    • Frontal eye field: Controls eye movement.

    Basal Nuclei

    • Cognition and emotion, regulates intensity of slow movement, filters out incorrect responses, inhibits unnecessary movements.

    Insula

    • Smallest lobe deep to the frontal, parietal, and temporal lobes, involved in special senses (taste, hearing and vestibular and visceral sensations).

    Sensory and Motor Homunculi

    • Visual representations in the brain of the body indicating the area size correlating with the sensory or motor nerves associated with the respective body parts.

    Brain Stem

    • Consists of the midbrain, pons, and medulla oblongata.
    • It controls automatic behaviors necessary for survival.

    Midbrain

    • Smallest part of the brainstem.
    • Contains cerebral peduncles that contain motor tracts.
    • Contains substantia nigra.
    • Responsible for visual response, coordination of movement, and "flight or fight" response.

    Pons

    • Located between midbrain and medulla oblongata.
    • Composed of conduction tracts.
    • Plays a role in breathing, relaying impulses.

    Medulla Oblongata

    • Inferior portion of brainstem.
    • Blends into spinal cord at foramen magnum.
    • Contains many nuclei related to vital functions.

    Cerebellum

    • Located posterior to pons and medulla, involved in muscle coordination, skilled movements, balance, coordination of complex movements, and learning.

    Reticular Formation

    • Reticular activating system (RAS): Sends impulses keeping the cerebrum aroused and alert.
    • Filters out repetitive, familiar, or weak stimuli.
    • Inhibited by sleep centers, alcohol, and drugs.

    Language Function

    • Language implementation system involves association cortices in the left hemisphere.
    • Broca's Area – Speech production
    • Wernicke's Area- Understanding Spoken and Written words

    Memory Processes

    • Memory is the storage and retrieval of information.
    • Declarative: Memory of facts, faces, words, dates.
    • Procedural: Memory of knowledge and skills.
    • Includes Short-Term and Long-Term Memory processes.

    Sleep and Wake Cycles

    • Sleep is a state of partial unconsciousness.
    • Cortical activity is depressed, but brain stem activity is not affected.
    • Non-rapid eye movement (NREM) sleep includes four distinct stages.
    • Rapid eye movement (REM) sleep occurs, and dreams typically take place.

    Sleep Regulation

    • Alternating cycles of sleep and wakefulness reflect the natural circadian rhythm.
    • The hypothalamus plays a major role, containing the biological clock.

    Parkinson's Disease (PD)

    • Pathophysiology involves dopamine neuron degeneration in the substantia nigra.
    • The corpus striatum, which coordinates movement, receives less-than-optimal dopamine signals and leads to tremors in hands/legs; rigidity, slowness of movement; impaired balance.

    Other

    • Autonomic Nervous System: Consists of Parasympathetic and Sympathetic divisions controlling involuntary activities (e.g., pupil dilation, heart rate, digestion).

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    Test your knowledge about astrocytes, the somatic nervous system, and the roles of different neuroglia in the central and peripheral nervous systems. This quiz covers important concepts like neuroplasticity, synapses, and the significance of myelin sheath. Challenge yourself and see how well you understand these essential topics in neuroscience.

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