Cytology Flashcards
What does the polarity of a cell refer to?
The number of poles (denrites and axons)
Which polarity is commonly found in neurons?
- Multipolar
Which neuron is commonly found in specialized sensory systems?
- Bipolar
Which neuron is commonly found in general senses?
- Pseudounipolar
How is a pseudounipolar neuron identified?
It is a specialized bipolar neuron in which the axon can bypass the cell body for faster propagation.
How are neurons classified according to axon length?
- Golgi I (long)
- Golgi II (short)
What do Golgi I neurons connect?
- One subsystem to another
What do Golgi II neurons connect?
- Neurons within the same subsystem
What are segmental Golgi II neurons?
- Project to the same segment (1 - 3 segments)
What are associative Golgi II neurons?
- Project ipsilaterally
What are commissural Golgi II neurons?
- Project contralaterally
What propriospinal Golgi II neurons?
- Project to other spinal column segments ( 5 - 10 - 15 segments)
What function do propriospinal Golgi II neurons perform?
- Motor reflex functions
What are tract cells?
- Golgi I neurons that only reside in the CNS
- Cells contain same information, and respond to the same modalities
- Form tracts
Which type of Golgi neuron is an interneuron?
Golgi II
What is an afferent neuron?
- Arriving to point of reference
What is an efferent neuron?
- Exiting point of reference
Which type of neuron is typically sensory?
- Afferent
Which type of neuron is typically motor?
- Efferent
What is an excitatory neuron?
- Causes an action
What is an inhibitory neuron?
- Prevents an action, or makes it more difficult
What is a modulatory neuron?
- Nervous system influences a structure or environment that makes the target neuron harder or easier to fire
What does it mean if a neuron has tonic/ regular spiking?
- The neuron is constantly firing
What does it mean if a neuron is phasic/ busting?
- Neurons fire in bursts
What does it mean if a neuron is fast spiking?
- It has fast firing rates
What are thin spike neurons?
I don’t know ???????????
What are cholinergic neurons?
Neurons that release acetylcholine
What are cholinergic neurons’ function?
- Primary stimulator to muscles
- Inhibitor of parasympathetic nervous system
What are GABAergic neurons?
- Primary inhibitors
What are glutamatergic neurons?
- Excitatory neurons
What are dopaminergic neurons?
- Excitatory neurons that release dopamine
What are serotonin releasing neurons?
- Excitatory neurons that release serotonin
What are the non-neural cells of the CNS and PNS?
- Neuroglia
By how much do glia cells outnumber neurons?
5 - 50: 1
What percentage of the total CNS is comprised of glia cells?
- 40 %
What are the 4 main functions of the glia cells?
- Development
- Support
- Nurture: (What nutrients the nuerons will and won’t receive)
- Maintenance of relatively constant environment (nutrition, and impulse conduction)
What are the most abundant neuroglia?
- Astrocytes
What type of neuron do astrocytes resemble?
- Multipolar cells
Where are fibrous astrocytes found?
In white matter
Where are protoplasmic astrocytes found?
In gray matter
What astrocytes that are found on the outside of blood vessels called?
- Perivascular glia
Where are oligodendroglia found?
Within the white matter of the CNS
What do oligodendroglia produce?
Myelin
What tissue do microglia originate from?
- Mesoderm
What type of cells do microglia replace in the CNS?
- White blood cells
How do microglia arrive in the nervous system?
Through the blood
What are ependymal cells?
Neural epithelial derivative cells that line the ventricles.
What are the origin cells of the neuroglia?
- Spongioblasts
How many cell layers are there in the ependymal layer?
- One
What is the out-pocketing of the ependymal layer, and what is its function?
- The Choroid Plexus
- Produces CSF
What is the origin of cerebrospinal fluid?
- Blood (it is a filtrate of blood)
What are the 2 components of the blood brain barrier?
- Tight endothelial layer
- Psedopodia/ astrocytes plug holes
What cells produce myelin in the periphery?
- Schwann Cells
What cells are analogous to astroglia in the periphery?
- Satellite glia
What are the perineural glia?
- Add structure to peripheral nervous system
What is a Gliosis?
- Proliferation of astrocytes that form plaques and scars that form barriers in the nervous system
Describe an axospinous synapse.
Axon synapses with spine of dendrite
Describe an axodendritic synapse.
Axon synapses with dendrite
Describe an axosomatic synapse.
Axon synapses with cell body
Describe an axoaxonic synapse.
Axon synapses with axon
Describe a chain synapse.
Axon synapses with multiple axons
Describe an en passant synapse.
Synapse occurs along path of neuron (not at end-plate)
What is an electrical junction?
- A gap junction that conducts fast due to no neurotransmitter being required to activate
What is an iontotropic receptor?
- Actional potential hits synapses and relases neurotransmitter, which opens gate, sodium flows in, and an action potential occurs
What is a metabotropic receptor?
- Neurotransmitter causes a morphological change, and a channel is activated via a secondary transmitter
How is a neuron that originates in the spinal cord, but then has an axon that travels into the periphery myelinated?
- The axon is myelinated by oligodendroglia in the spinal cord, and by schwann cells in the periphery.
What is the branch of an axon called?
A collateral
Which protective layers of the spinal cord continue on into the peripheral nerve?
The dura and arachnoid mater.
Which protective layer lines the spinal cord directly?
Pia mater
Name the 3 protective sheaths of the spinal nerves.
Endoneurium
Perineurium
Endoneurium
Which protective coating of the peripheral nerves covers a fascile?
Perineurium
What is a fascile?
A collection of axons
What is the protective coating that lines each individual axon?
Endoneurium
What is the protective coating that lines collections of fasciles?
Epineurium
What is the epifascicular epineurium?
Epineurium that surrounds the entire nerve.
What is the inferfascicular epineurium?
Epineurium that holds all the fasciles together.
What are the 3 functions of interfascicular epineurium?
- Loose attachment to epifascicular epineurium allows for the sliding of one fascile over another
- Helps facilitate dispersion of compressive forces
- Gives nerve structure
What type of collagen makes up the perineurium?
- Type I and Type II
How is the collagen of the perineurium oriented?
- In oblique, longitudinal, and circumferential directions
How many cell layers thick is the perineurium?
-Up to 15 cell layers thick
What is the primary function of the perineurium?
Antiloading shearing responses/ mechanical strength
What function does the perineurium provide in the brain?
Blood brain barrier
What is the composition of endoneurium? (What is it made up of? What is it orientation?)
- Loose CT of type I and II; longitudinally oriented between axons
- Basal lamina made up of type IV collagen
How are nerves supplied blood?
- Vessels run longitudinally along the perineurium and periodically enter epineurium
- Divide into arterioles that form an anastomatic netowrk in epineurium and perineurium
- Vessels enter endoneurium and travel longitudinally as capillaries
Termed: Epineurial, perineurial, and endoneurial arteries
Describe the relationship between unmylelinated nerves and schwann cells.
- One schwann cell’s cytoplasm will surround many different axons like sticks and a ballon
What is the continues layer formed by multiple schwann cells surrounding a nerve?
- Neurolemma
Are myelinated or unmyelinated fibers more common?
Umyelinated
Are myelinated or unmyelinated fibers larger?
Myelinated
What is a mesaxon?
- Gap in the outer cytoplasm of the schwann cell caused by the axon
How do myelinated fibers differ form unmyelinated fibers in the periphery?
1 schwann cell: 1 axon
Schwann cell wraps around axon forming a thick fatty covering
What is a node?
The gap between myelin sheaths
What is an internode?
The area of myelination
How do myelinated axons different in the CNS compared to the PNS?
- There is no neurolemme
- There is not a 1:1 relationship
- One oligodendroglia provides myelin to many axons
Why can the CNS not regenerate as well as the PNS?
- There is no neurolemma sheath to guide axon regeneration
What is the first classification of nerve fibers?
- General: Distributed throughout the body
- Special: Restricted throughout the body
What is the second classification of nerve fibers?
- Visceral: Autonomic/ brachial arches
- Somatic: Somites, body, skin, muscles, joints
What is the third classification of nerve fibers?
- Afferent: Sensory (Received by spinal cord)
- Efferent: Motor (Sent from spinal cord)
What are the 4 anatomic functional types of cranial and spinal nerves?
- General Somatic Afferent (GSA)
- General Visceral Afferent (GVA)
- General Visceral Efferent (GVE)
- General Somatic Efferent (GSE)
What anatomic functional type of nerve provides conscious sensation (pain, temperature, touch, proprioception)?
- General Somatic Afferent
What anatomic functional type of nerve provides visceral sensation? (Pain from ischemia, blood pressure, etc.)
- General Visceral Afferent
What anatomic functional type of nerve provides autonomic motor drive to smooth and cardiac muscle and glands (parasympathetic, sympathetic - preganglionic and postganglionic fibers)?
- General Visercal Efferent
What anatomic functional type of nerve provides voluntary motor drive to skeletal muscle (derived from myotomes)?
- General somatic efferent
What is the explanation for referred pain in terms of a functional anatomical perspective?
- Visceral and somatic afferent fibers travel the same pathways, and can activate the same sensory neurons as somatic fibers
What are the only spinal/ cranial nerves that do not have all 4 components?
- Cutaneous nerves
What are the 3 anatomic functional components unique to cranial nerves?
- Special Visceral Efferent
- Special Visceral Afferent
- Special Somatic Afferent
Which anatomic functional component provides visceral sensations of taste and smell?
Special Visceral Afferent
Which anatomic functional component provides somatic sensations of vision, hearing, and equilibrium?
Special Somatic Afferent
Which anatomic functional component provides voluntary motor drive to skeletal muscle (derived from the branchiomeres)?
Special Visceral Efferent
What is the name of the general nerve classification based on size and speed of conduction?
Erlanger - Gasser
What is the name of the sensory root nerve classification?
Lloyd - Hunt
