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)
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
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
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
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
6
Q
What part of the neuron houses the mitochondria?
A
Axon
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
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
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)
10
Q
What is an axon’s cell membrane called?
A
Axolemma
11
Q
What is an axon’s cytoplasm called?
A
Axoplasm
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
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
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
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
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
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)
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)
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
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)
