Neuroscience Class: Action Potentials Quiz
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Questions and Answers

What is the threshold potential that must be reached to trigger an action potential?

  • -55 (correct)
  • -70
  • 0
  • -90

    • Depolarization occurs when the inside of the cell becomes more negative.

    False (B)

    What is the role of the Na+/K+ pump in nerve cells?

    To return sodium and potassium ions to their original concentrations after an action potential.

    During repolarization, _______ ions rush out of the cell.

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

    Match the phase of the action potential with its description:

    <p>Depolarization = Membrane potential reaches +30 mV Repolarization = Membrane returns to resting potential Threshold stimulus = Excitatory stimulus reaching -55 mV Hyperpolarization = Membrane potential drops below -70 mV</p> Signup and view all the answers

    What occurs during the Absolute Refractory Period?

    <p>Threshold stimulus cannot generate another action potential (A)</p> Signup and view all the answers

    The speed of impulse conduction is faster in thin, unmyelinated axons than in thick, myelinated axons.

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

    Which part of the brain is responsible for voluntary skeletal muscle movements?

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

    What is the main factor that influences the speed of impulse conduction in myelinated axons?

    <p>Myelination and diameter of the axon</p> Signup and view all the answers

    The right hemisphere is dominant in most people for language skills.

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

    During the relative refractory period, another action potential can only be generated by a ______ stimulus.

    <p>high-intensity</p> Signup and view all the answers

    What is the long-term memory characterized by?

    <p>Persistence of memory that lasts a lifetime.</p> Signup and view all the answers

    The diencephalon is composed of structures such as the thalamus and the __________.

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

    Match the type of axon with its conduction characteristics:

    <p>Thick, myelinated axons = 120 m/sec Thin, unmyelinated axons = 0.5 m/sec Myelinated axons = Saltatory conduction Unmyelinated axons = Continuous conduction</p> Signup and view all the answers

    Match the following brain areas with their primary functions:

    <p>Thalamus = Channels sensory impulses to appropriate cerebral cortex Hypothalamus = Regulates visceral activities and maintains homeostasis Basal nuclei = Produces dopamine and helps control voluntary movement Limbic System = Controls emotional responses and behaviors toward survival</p> Signup and view all the answers

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

    <p>Processing visual information (A)</p> Signup and view all the answers

    The basal nuclei are located on the surface of the cerebral hemispheres.

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

    What does long-term potentiation involve?

    <p>An increase in neurotransmitter release and effectiveness of synaptic transmission.</p> Signup and view all the answers

    Motor tasks involving orientation in space are controlled by the __________ hemisphere.

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

    What are the components of the basal nuclei?

    <p>Caudate nucleus, putamen, globus pallidus (A)</p> Signup and view all the answers

    Which type of receptor is activated by nicotine?

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

    Acetylcholine is decomposed by the enzyme acetylcholinesterase (AChE).

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

    What part of the brain is largely responsible for controlling autonomic activity?

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

    The ________ and cerebral cortex control emotional responses.

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

    Match the following types of neurons to their functions:

    <p>Sensory neurons = Carry impulses from periphery to CNS Motor neurons = Carry impulses from CNS to effectors Interneurons = Link neurons within the CNS Efferent neurons = Another term for motor neurons</p> Signup and view all the answers

    Which structure is primarily responsible for the insulation of axons in the Peripheral Nervous System (PNS)?

    <p>Schwann cells (C)</p> Signup and view all the answers

    Neurons can regenerate effectively in the Central Nervous System (CNS).

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

    Which part of the brain connects the brain to the spinal cord?

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

    What is the primary charge of the inside of a polarized neuron at rest?

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

    _________ are cells that support clusters of neuron cell bodies in ganglia.

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

    Cerebrospinal fluid is produced in the spinal cord.

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

    What are the three layers of the meninges?

    <p>Dura mater, Arachnoid mater, Pia mater</p> Signup and view all the answers

    Match the following types of neurotransmitters to their functions:

    <p>Acetylcholine = Decomposed by acetylcholinesterase Norepinephrine = Inactivated by monoamine oxidase (MAO) Epinephrine = Adrenaline, involved in the fight or flight response Dopamine = Influences mood and reward</p> Signup and view all the answers

    The _______ is responsible for understanding and formulating language.

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

    Which of the following changes happens with aging in the nervous system?

    <p>Loss of neurons in the frontal cortex (B)</p> Signup and view all the answers

    The resting membrane potential of a neuron is about 0 mV.

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

    What is the role of the Na+/K+ Pump in neurons?

    <p>Maintains ion concentration balance</p> Signup and view all the answers

    What is one function of the cerebellum?

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

    The brain shrinks about ________ over an average lifetime.

    <p>10%</p> Signup and view all the answers

    The cerebral cortex contains the majority of neuron cell bodies in the nervous system.

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

    What connects the two cerebral hemispheres?

    <p>Corpus callosum</p> Signup and view all the answers

    Cerebrospinal fluid is absorbed by the _______ granulations.

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

    Which of the following is NOT a function of the cerebral cortex?

    <p>Regulating visceral activities (B)</p> Signup and view all the answers

    The thalamus is produced from the diencephalon.

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

    What is the volume of cerebrospinal fluid at any time?

    <p>About 140 mL</p> Signup and view all the answers

    The _______ lobe is responsible for motor commands to skeletal muscles.

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

    Which area of the brain is responsible for coordinating muscular movement?

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

    What is convergence in the context of neural functions?

    <p>One neuron receives input from several neurons. (D)</p> Signup and view all the answers

    Divergence allows one neuron to amplify impulses sent to multiple neurons.

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

    What two main categories can sensory receptors be divided into?

    <p>General senses and special senses</p> Signup and view all the answers

    Sensory receptors can be classified into five types: chemoreceptors, nociceptors (pain receptors), thermoreceptors, mechanoreceptors, and _________.

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

    Which type of sensory receptor is primarily responsible for detecting changes in temperature?

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

    Sensory adaptation refers to an increased response to continuous stimuli.

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

    What is the primary function of nociceptors?

    <p>To respond to tissue damage and pain.</p> Signup and view all the answers

    Match the following sensory stimuli with their corresponding receptors:

    <p>Smell = Olfactory receptors Taste = Taste bud receptor cells Sight = Rods and cones in retina Hearing = Hair cells in cochlea</p> Signup and view all the answers

    Which of the following is NOT a general sense?

    <p>Sight (C)</p> Signup and view all the answers

    Pain receptors can adapt significantly to continuous pain stimuli.

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

    Describe the process of transduction in sensory perception.

    <p>Transduction is the conversion of a stimulus into graded receptor potentials.</p> Signup and view all the answers

    The type of receptor that responds to changes in chemical concentrations is called a _________.

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

    What is a characteristic of proprioceptive senses?

    <p>They detect changes in muscles and body position. (B)</p> Signup and view all the answers

    Brain projections allow a person to accurately locate the region of stimulation.

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

    What type of mechanoreceptor detects fine touch and texture?

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

    Study Notes

    Nervous System Overview

    • The nervous system is the master regulatory system in the body.
    • It sends and receives information, processing it to make decisions.
    • It controls muscles and glands to respond.
    • The system maintains homeostasis, regulates thought, learning, and memory.
    • The nervous system is comprised of two main cell types: neurons and neuroglia.

    Neuron Structure

    • Neurons vary in size and shape, with differences in length, number, and size of axons and dendrites.
    • They share structural features including the cell body (soma or perikaryon) which includes the nucleus, cytoplasm, organelles, neurofilaments, and Nissl bodies.
    • Dendrites: branched receptive surfaces extending from cell body, facilitating communication.
    • Axon: Carries impulses away from the cell body, typically only one axon per neuron, ending at the axon terminal with synaptic knobs.

    Axon Features

    • Axon Hillock: Cone-shaped region where axon connects to cell body.
    • Collaterals: Branches extending from the axon.
    • Axon Terminal: Specialized endings.
    • Synaptic Knob: Rounded ending of an axon terminal.

    Schwann Cells

    • Neuroglia of the peripheral nervous system (PNS).
    • Wrap around some axons in layers called myelin, acting as electrical insulators.
    • Myelin is a mixture of fats and proteins.
    • Nodes of Ranvier: Gaps in myelin sheath between Schwann cells.

    Myelinated vs. Unmyelinated Axons

    • Myelinated axons increase conduction speed, while unmyelinated axons do not.
    • Myelinated axons are insulated by a myelin sheath comprised of Schwann cells' layered membranes.
    • Unmyelinated axons lack this myelin sheath.

    Neuron Classification by Structure

    • Multipolar Neurons: Many dendrites and one axon. Typical neuron type in the CNS and autonomic nervous system.
    • Bipolar Neurons: One dendrite and one axon. Found in special sensory organs.
    • Unipolar/Pseudounipolar Neurons: A single process from the cell body that acts as both axon and dendrite. Commonly found in the PNS.

    Neuron Classification by Function

    • Sensory (Afferent): Carry impulses from sensory receptors to the CNS
    • Interneurons (Association or Internuncial): Relay information between other neurons in the CNS.
    • Motor (Efferent): Carry impulses from the CNS to effectors (muscles or glands).

    Neuroglia of the CNS

    • Astrocytes: Support neurons, regulate ions, and help with synapse formation. They are connected to blood vessels for nutrient exchange.
    • Oligodendrocytes: Produce the myelin sheath for CNS axons.
    • Microglia: Phagocytic cells, removing excess ions and neurotransmitters.
    • Ependymal Cells: Line the central canal/ventricles of the brain/spinal cord. Regulate cerebrospinal fluid and regulate composition.

    Neuroglia of the PNS

    • Schwann cells: Encase peripheral axons with myelin in the PNS, to speed up impulses.
    • Satellite cells: Surround neuron cell bodies in ganglia, supporting and nourishing them.

    Lifespan Changes

    • Brain cell death occurs early in development and throughout life due to apoptosis
    • The brain's size often decreases with age by approximately 10%.
    • There is a notable loss of brain cells, particularly in the temporal lobes, but fewer losses in other areas like the brainstem
    • Many cells, including neurons, lose dendritic branches
    • Neurotransmitter action potentials slow down, and memory often fades
    • Other changes include compromised reflexes, increased chances of falling or fainting, and altered sleep patterns.

    Synapse

    • A synapse is a site where a neuron communicates with another neuron or an effector tissue (muscle cell or a gland), which is transmitted from one neuron to the next via neurotransmitters.
    • Neurons communicate at a synapse consisting of a presynaptic neuron which sends, a postsynaptic neuron is the receiver, and a synaptic cleft separating the two.

    Synaptic Transmission

    • Synaptic transmission describes how a presynaptic neuron sends an impulse to a postsynaptic neuron by using neurotransmitters that cross the synaptic cleft.
    • The process is one-way and is aided by neurotransmitters binding and activating chemically regulated ion channels on the postsynaptic neuron, to generate local potentials, and creating significant implications for signal processing.

    Acetylcholine (ACh) Neurotransmitter

    • A primary neurotransmitter in neuromuscular junctions, where motor neurons trigger skeletal muscle contractions.

    Nerve Fibers

    • Sensory fibers: conduct impulses toward the brain or spinal cord
    • Motor fibers: conduct impulses away from the brain or spinal cord
    • Mixed fibers: contain both sensory and motor fibers

    Classification of Nerves by Origin

    • Cranial nerves: originate from the brain.
    • Spinal nerves: emerge from the spinal cord

    Cranial Nerves

    • There are 12 pairs of cranial nerves.
    • Most are mixed nerves (containing both sensory and motor fibers).
    • Some are strictly sensory, connected to special senses, while others are primarily motor, controlling muscles and/or glands.
    • The first two pairs have fibers arising from sensory organs and the rest arise from the brainstem.

    Nervous System Structure

    • Central Nervous System: Brain and spinal cord
    • Peripheral Nervous System: Connects the CNS to the rest of the body.

    Peripheral Nervous System (PNS) Subdivisions

    • Somatic Nervous System: Voluntary movements; control of skeletal muscles
    • Autonomic Nervous System: Involuntary control of visceral organs.

    Autonomic Nervous System (ANS)

    • Hypothalamus largely controls this system for involuntary functions of visceral organs.
    • The ANS is largely divided into: •Sympathetic division: "fight-or-flight” response. Increases heart rate, blood pressure, and blood glucose •Parasympathetic division: “rest-and-digest” response. Decreases heart rate, and lowers blood pressure

    Sensory Adaptation

    • The ability for the nervous system to downregulate responsiveness to frequently occurring stimuli.
    • Sensory adaptation assists in maintaining homeostasis by filtering out non-critical stimuli and allows focusing on important occurrences.

    General Senses

    • Located throughout the body (skin, muscles, joints, and viscera).
    • Subclassified in exteroceptive (skin surface senses), interoceptive (or visceroceptive senses) to detect changes in internal organs, and proprioceptive senses (body position and movement from muscles, tendons, and joints).

    Touch and Pressure Sense

    • Free Nerve Endings: Simplest receptors, sensitive to itching and other sensations.
    • Tactile (Meissner's) Corpuscles: Abundant in hairless portions, sensitive to fine touch and texture.
    • Lamellated (Pacinian) Corpuscles: Deeper in tissues, sensitive to pressure and vibrations.

    Temperature Receptors (Thermoreceptors)

    • They are free nerve endings in skin
    • Warm receptors respond to temperatures above 25°C (77°F)
    • Cold receptors function between 10°C (50°F) and 20°C (68°F)

    Pain Receptors (Nociceptors)

    • Free nerve endings found widely in the body (except brain).
    • Activated by tissue damage, chemicals, and extreme temperatures/oxygen deficiency:
    • They produce pain sensations and adapt very little or not at all.
    • Referred pain is an unusual sensation where the pain doesn't originate from the site, due to shared nerve pathways of the sensory impulses.

    Special Senses

    • These senses are concentrated in complex organs of the head, comprising smell (olfactory organs), taste (taste buds), hearing and equilibrium (inner ears), and vision (eyes).

    Sense of Smell (Olfaction)

    • Sensory receptors are chemoreceptors responsive to chemicals dissolved in liquids.
    • Located in the nasal cavity and contain bipolar neurons (olfactory receptor cells) and support cells.
    • Olfactory receptors are responsible for 75-80% of taste perception.

    Olfactory Pathways

    • When a stimulus activates the olfactory receptors, nerve impulses travel through openings in the ethmoid bone to olfactory bulbs, olfactory tracts, the limbic system and olfactory cortex, resulting in interpretation.
    • Emotional responses are triggered by the limbic system based on the odorant molecule.

    Taste (Gustation)

    • Receptors are chemoreceptors, modified epithelial cells (taste cells).
    • Located on papillae (bumps) of the tongue, along the oral cavity.
    • Taste cells contain taste hairs (microvilli) extending through pores of taste buds.
    • Taste cells are renewed and replaced frequently (every few days).

    Taste Sensation

    • There are five primary taste sensations: sweet, sour, salty, bitter, and umami.
    • Each flavor results from one or more of these five tastes.
    • Taste receptors exhibit rapid adaptation, allowing for quick adjustment to stimuli.

    Taste Pathways

    • Sensory impulses from taste receptor cells follow three different cranial nerves: facial, glossopharyngeal, and vagus.
    • Impulses are transmitted to the medulla oblongata and then to the thalamus.
    • Taste interpretation in the gustatory cortex in the insula.

    Sense of Hearing

    • The organ of hearing and equilibrium in the ear comprises three main parts: outer (external), middle, and inner (internal).

    Outer (External) Ear

    • Comprises the auricle (funnel-shaped exterior) and external acoustic meatus(canal).
    • The auricle collects sound waves, while the acoustic meatus carries sound to the eardrum (tympanic membrane).
    • The ceruminous glands secrete cerumen (earwax) in the acoustic meatus.

    Middle Ear

    • Also called the tympanic cavity which is an air-filled space.
    • It contains the auditory ossicles (malleus, incus, and stapes) which amplify sound vibrations
    • The eardrum (tympanic membrane) transmits sound waves to the ossicles.
    • The oval window is a membrane-covered opening that transmits vibrations from the stapes to the inner ear.

    Middle Ear: Tympanic Reflex

    • A reflex triggered by loud noises, protecting the inner ear from damage.
    • Tensor tympani: tightens the eardrum
    • Stapedius; restricts the stapes' movement

    Auditory Tube

    • Also known as the Eustachian tube, connects the middle ear to the throat, maintaining equal air pressure across the tympanic membrane.

    Inner (Internal) Ear

    • The inner ear is comprised of bony labyrinth and includes the semicircular canals contributing to dynamic equilibrium, and the vestibule functions in maintaining static equilibrium.
    • The cochlea contains the membranous labyrinth, filled with endolymph and is associated with hearing.

    Cochlea

    • The cochlea is a spiral, snail shaped structure of the inner ear, which involves the scala vestibuli, scala tympani, and cochlear duct, critical for hearing.
    • Three compartments including vestibular membrane, basilar membrane, and tectorial membrane. Supporting the receptor organ for hearing (organ of Corti)

    Auditory Pathways

    • Impulses transmitted through auditory nerves to various nuclei in the medulla oblongata, midbrain, and pons and synapses.
    • Sensory signals are routed to the thalamus, and then to the auditory cortex of the temporal lobe of the cerebrum where sound is interpreted.

    Sense of Sight (Vision)

    • Visual receptors are found in the eye
    • The accessory organs of the eye for sight include the eyelids (palpebrae), which provide protection; the eyelashes offering more protection; lacrimal apparatus that produce tears; and extrinsic eye muscles enabling movement of the eye.

    Visual Accessory Organs (Eyelids)

    • Composed of skin, muscle (orbicularis oculi for closure, levator palpebrae superioris for opening), connective tissue, and the conjunctiva which is a mucous membrane covering the inside surfaces of the eyelids and a part of the eyeball.

    Visual Accessory Organs (Lacrimal Apparatus)

    • The lacrimal gland secretes tears onto the anterior surface of the eye.
    • Tears are drained from the eye by the lacrimal canaliculi, connecting to the lacrimal sac, and emptying into the nasal cavity.

    Structure of the Eye

    • The eye is a hollow, spherical organ.
    • The wall has three layers: •Outer fibrous tunic: cornea and sclera. •Middle vascular tunic: choroid, ciliary body, and iris •Inner nervous tunic: retina

    Outer (Fibrous) Tunic

    • The cornea is the anterior portion of the outer tunic, a transparent structure that refracts light rays.
    • The sclera is the posterior five-sixths, providing protection, and attachment point for muscles.

    Anterior Portion of the Eye

    • The cavity between the cornea and lens filled with aqueous humor.
    • The lens, transparent biconvex structure, helps focus light to a point on the retina.

    Iris and Aqueous Humor

    • The iris, a colored portion of the eye, controls the amount of light entering through the pupil.
    • The aqueous humor is the fluid filled in the anterior chamber to maintain pressure and nourish the cornea.

    Visual Pathways

    • Signals travel from the ganglion cells in the retina to the optic nerve, optic chiasma, optic tracts, thalamus, optic radiations, and visual cortex of the occipital lobe.
    • Some fibers connect to the brainstem to control visual reflexes and tracking of objects.

    Life Span Changes

    • Age-related hearing loss, as well as age-related visual problems (dry eyes, floaters, presbyopia, glaucoma, cataracts, and macular degeneration) may occur
    • Loss of smell and taste are also age-related conditions.

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