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MSK Exam 2 > Nervous Tissue > Flashcards

Nervous Tissue Flashcards

1
Q

Nervous Tissue

A
  • specialized to send and receive electrical signals through the body
  • allows the nervous system to communicate with and control the body via their interconnections
  • one key feature is that this tissue can generate and propagate electrical signals called action potentials
  • contains two basic cell types: neurons (functional unit), glial cells (support)
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2
Q

Central Nervous System (CNS)

A
  • nervous tissue present in the dorsal body cavity
  • consists of brain and spinal cord
  • it processes incoming stimuli from the internal and external environment and determines the appropriate response; it then sends signals through the body (via PNS) for a response
  • much wider range of glial cells in this system to support the neurons
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3
Q

Peripheral Nervous System (PNS)

A
  • nervous tissue found throughout the body outside of the dorsal body cavity
  • responsible for collecting information from the external and internal environments and sending it to the CNS (afferent signals)
  • transports information from the CNS to the appropriate muscle, gland, etc. in the body for the appropriate response (efferent signals)
  • nervous tissue is found in nerves and ganglia (clusters of cell bodies)
  • only two types of glial cells here because of the different packaging of the neurons
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4
Q

Neuron

A
  • the functional unit/cell in nervous tissue
  • sends and receives electrical signals within the body allowing the parts to be interconnected and function
  • often highly specialized in their role: excitable (respond to a stimulus), conduct electricity (AP) and secrete NTs
  • the shape and size of these cells are highly variable
  • limited ability to undergo mitosis
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5
Q

Soma (Perikaryon)

A
  • the cell body of a neuron
  • holds the nucleus and the organelles within its neuroplasm (cytoplasm)
  • contains many processes – dendrites, axons
  • processes the incoming information from the dendrites and sends the signal along the axon in warranted
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6
Q

What part of the neuron houses the mitochondria?

A

Axon

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7
Q

Chromatophilic Substance (Nissl Substance/Bodies)

A
  • the distinctive (basophilic) rough ER within the soma
  • allows the neuron to produce NTs and maintain the cell
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8
Q

Dendrite

A
  • extension of the neuron cell body that picks up information (stimuli at synapses or dendritic spines) and transfers it to the cell body
  • neurons contain many dendrites to receive both excitatory and inhibitory signals
  • vary in shape but are often short and highly branched
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9
Q

Axon

A
  • extension of the neuron cell body that allows the neuron to communicate via synapses with other neurons or tissues within the body (muscles or glands)
  • creates an AP which allows for communication
  • able to interact with other axons to modify the signal being sent
  • typically neuron only has one
  • branches at the terminal end of the neuron – terminal arborization
  • due to its distance from the soma, it has its own terminology – axolemma for neurolemma (cell membrane), axoplasm for neuroplasm (cytoplasm)
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10
Q

What is an axon’s cell membrane called?

A

Axolemma

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11
Q

What is an axon’s cytoplasm called?

A

Axoplasm

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12
Q

Axon Hillock

A
  • the triangular area between the soma and the axon
  • it summates the electrical signal (AP) and triggers the AP down the axon if the threshold is met
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13
Q

Synaptic Knob (Terminal Bouton)

A
  • the rounded dilation found at the end of the axonal terminal branches
  • in chemical synapses, this area stores NTs and releases them when the neuron is ready to send a signal with another structure
  • in electrical synapses, gap junctions provide direct transmission of the ion to propagate the electrical signal
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14
Q

Multipolar Neuron

A
  • a neuron that has multiple dendrites and one axon
  • most common type of structural classification
  • this is seen in motor (efferent) neurons, and some sensory and interneurons too
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15
Q

Unipolar / Pseudounipolar Neuron

A
  • a neuron that does not have any true dendrites but does have two axons
  • one axon travels to the CNS while the other axon travels toward a peripheral location
  • common with sensory (afferent) neurons
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16
Q

Bipolar Neuron

A
  • a neuron that has one dendrite and one axon
  • this type is found in sensory roles such as the retina, inner ear, and olfactory membrane
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17
Q

Sensory Neurons (Afferent Neurons)

A
  • type of neuron that picks up signals from the internal and external environment, and transmits that information to the CNS
  • divided into two groups: somatic (conscious input from skin, MSK system, special senses) and visceral (sensory information from internal organs and cardiovascular structures)
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18
Q

Motor Neuron (Efferent Neuron)

A
  • type of neuron that takes information from the CNS and distributes it through the body for a response (muscle and glands)
  • can be divided into two groups: somatic (conscious or voluntary control of skeletal muscle), and autonomic (unconscious control of internal organs and glands)
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19
Q

Interneuron

A
  • type of neuron that is present in the CNS
  • it receives, processes, links, and communicates with other neurons in the body, creating functional networks called circuits
  • most neurons in the body are this type of neuron
  • structurally classified as either anaxonic (no axon) or multipolar
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20
Q

Synapse

A
  • where one neuron meets another neuron or the intended signal target (effector cell)
  • a uni-directional signal is transferred between the two parts – a presynaptic neuron to a postsynaptic structure
  • two types of synapses: electrical and chemical
21
Q

Electrical Synapse

A
  • presynaptic neuron touches the postsynaptic neuron or structure and transfers the electrical signal directly
  • this type of synapse is located in the heart – ions pass through the gap junctions continuing the electrical signal from the presynaptic to the postsynaptic
22
Q

Chemical Synapse

A
  • presynaptic neuron does not touch the postsynaptic neuron or structure; instead there is a synaptic cleft between the two structures
  • to transfer the signal, the presynaptic neuron releases NTs
  • Ex. neuromuscular junction (neuron -> muscle fiber)
23
Q

Neuromuscular Junction

A
  • example of a chemical synapse
  • neuron meets up with a myocyte
  • AP of the neuron is passed from the nervous system onto the muscular system
  • signal changes from electrical (ions) to chemical (NT) at the synapse
24
Q

Presynaptic Axon Terminal

A
  • component of neuromuscular junction
  • the terminal end of the neuron’s axon, the synaptic knob
  • NTs are located in the synaptic knob and are released when triggered to pass the AP to the muscle
  • glial cells called neurolemmocytes surround this area and help maintain it
25
Q

What cells surround the Presynaptic Axon Terminal?

A

Neurolemmocytes

26
Q

Synaptic Cleft

A
  • component of neuromuscular junction
  • the space between the neuron and the myocyte
  • NTs released from the neuron pass through this gap and bind to receptors on the myocyte
27
Q

Motor Endplate (Postsynaptic Cell Membrane)

A
  • component of neuromuscular junction
  • part of the myocyte that contains receptors for the NTs released from the neuron
  • the NTs bind to the receptors, causing the muscle tissue to respond – can be excitatory or inhibitory
28
Q

Glial Cell

A
  • located in both the CNS and PNS
  • cells that provide a supportive role in the nervous tissue, taking place of connective tissue proper, including protecting and insulating the neurons
  • also help ensure an optimal working environment for neurons
  • undergo mitosis and create the majority of the nervous tissue
29
Q

Oligodendrocyte

A
  • the myelinating cell of the CNS
  • type of glial cell
  • has many processes that surround multiple neuron axons – can myelinate many axons at once
  • covers axons with myelin (lipid and protein membrane) which helps insulate the axon and speed up the signal transmission
  • contributes to the white matter of the brain
  • under the microscope they appear as small cells with rounded condensed nuclei and unstained cytoplasm
30
Q

Gray Matter

A
  • present in the brain and spinal cord (CNS)
  • refers to the neuron cell bodies, dendrites, synapses and the glial cell bodies
  • in the spinal cord, this is the inner aspect of the cord (appears as a butterfly pattern)
  • in the brain, this is the outer, external surface that is present deep within the brain in areas called cerebral nuclei
  • appears grayish in color to the naked eye
31
Q

White Matter

A
  • present in the brain and spinal cord (CNS)
  • refers to the myelinated axons (lipids and proteins); also contains astrocytes and microglial cells
  • in the spinal cord, this is more superficial
  • in the brain, this is located deeper
  • appears white in color to the naked eye
32
Q

Astrocyte

A
  • present in the CNS
  • contains many processes coming from the central cell body; enlarged terminal ends surround capillaries of the blood-brain barrier
  • helps during the embryonic development of the CNS, associates with/covers synapses, and assists in the blood-brain barrier and interstitial fluid composition
  • these cells fill in areas of damaged brain tissue like connective tissue did in the skin creating scar tissue
  • communicate via gap junctions/electrical synapses to allow them to carry out their role
    -Histology: star-shaped
33
Q

Ependymal Cell

A
  • cell that is present in the cavities inside the brain (ventricles) and spinal cord (central canal)
  • part of the choroid plexus that aids with the production and circulation of cerebrospinal fluid (CSF supplies needed substances such as ions to the brain and spinal cord neurons)
  • apical surface might have cilia or microvilli which aid in CSF movement and absoprtion
  • Histology: cuboidal or columnar shaped
34
Q

Microglial Cell

A
  • a macrophage found within the CNS
  • helps with the immune response
  • contains many cell bodies at the center with numerous branches shooting outwards
  • while it moves throughout tissue, it removes damage or inactive synapses as well as foreign invaders
  • originates from myocytes
  • only glial cells that migrate
35
Q

What cell do Microglial cells originate from?

A

Myocytes

36
Q

What cell surrounds a neuron cell body in the PNS?

A

Satellite Cell

37
Q

Satellite Cell

A
  • a glial cell that is found in the PNS
  • multiple of these cells surround a neuron cell body found in ganglia (accumulations of neuron cell bodies of the PNS)
  • function in protecting the soma from the surrounding environment and provide insulation
  • ganglia are often surrounded by connective tissue making them appear like discrete, bulbous structures to the naked eye
  • Histology: appear like squamous or cuboidal cells around the soma
38
Q

Neurolemmocyte (Schwann Cell)

A
  • the myelinating cell of the PNS
  • protects the neuron’s axon by creating a myelin sheath (lipid and protein) around the motor or sensory axons
  • although not all axons in the PNS are myelinated, they have neurolemmocytes associated with them because they cover the axon through the synapse
39
Q

Neurolemmocyte (Schwann Cell)

A
  • the myelinating cell of the PNS
  • can only myelinate one cell axon at a time
  • protects the neuron’s axon by creating a myelin sheath (lipid and protein) around the motor or sensory axons
  • although not all axons in the PNS are myelinated, they have neurolemmocytes associated with them because they cover the axon through the synapse
40
Q

Nodes of Ranvier

A
  • gaps in the myelinated axon – often called nodal gaps
  • they allow the electrical signal (AP) to pass over the myelination which speeds up the signal transduction because the AP doesn’t have to travel the entire axolemma
41
Q

Nerve

A
  • a bundle of neurons (can be myelinated or unmyelinated) and their supporting glial cells that travel through the body (PNS)
  • different types of nerves in the body based on the type of neurons they hold: sensory only, motor only, or mixed
  • the mixed type (contains both sensory and motor neurons) is the most common
42
Q

Endoneurium

A
  • the deepest connective tissue layer in a nerve
  • composed of loose connective tissue surrounding each of the neuron’s axons and associated neurolemmocytes
  • separates and insulates the electrical signals traveling along the axons
  • also serves as a pathway for capillaries and contains fibroblasts
43
Q

Perineurium

A
  • it is connective tissue that bundles a group of axons together (fascicle) in a nerve
  • fibrocytes join together via tight cellular junctions to create the blood-nerve barrier
  • fascicles hold neurons that are going to the same area in the body
44
Q

Nerve Fascicle

A
  • a bundle of nerve fibers belonging to a nerve in the PNS – essentially it is a group of nerve fibers
  • it is enclosed by perineurium, a layer of fascial connective tissue
45
Q

Epineurium

A
  • the most superficial connective tissue layer within a nerve
  • it bundles fascicles within a nerve together and fills in the spaces between them, providing support and protection as the nerve travels throughout the body
46
Q

Characteristic of the chromatophilic substance found in neurons:

A

it is the site of mRNA translation for proteins of the axolemma
(this is a region with concentrated rER and other polysomes that are basophilic and help in the production of cytoskeletal proteins and proteins for transport/secretion)

47
Q

What structure in the choroid plexus is responsible for transporting water directly into the CSF from capillaries?

A

Ependymal Cells

48
Q

Term that applies to a collection of neuron cell bodies in the CNS:

A

Nuclei
(deep within the brain are localized, variously shaped darker areas called cerebral nuclei, each containing large numbers of aggregated somas)

49
Q

Characteristic of the connective tissue layer that surrounds individual fascicles in a large peripheral nerve:

A

Important part of the blood-nerve barrier
(groups of axons with their schwann cells and endoneurium are surrounded by the perineurium, consisting of layered squamous fibroblastic cells joined by tight junctions)

MSK Exam 2 (14 decks)

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