Flashcards in Block 2 - Nerve Tissue Deck (67):
How is the extra plasma membrane removed for the presynaptic knob membrane?
Through clathrin-coated vesicles via endocytosis
Why are neurons known as electric capacitors?
The voltage across their plasma membrane is not constant and therefore they conduct signals via electricity down their axons.
What are the 5 morphological differences bewtween an axon and a dendrite?
Axon - no Nissl bodies, myelin sheath, constant diameter, restricted branching, smooth surface
Dendrite - Nissl bodies, no myelin sheath, tapered, branches profusely, rough surface
How many neurons are contained in the body, on average?
What are the two major components of nerve tissue?
Neurons and Neuroglia (glial cells)
What are the three functional categories of neurons?
Sensory, interneurons, and motor
What type of cell lines the ventricles of the brain and produce/absorb CSF?
What is absent from the axon hillock?
Describe a neuron's nucleus
Large, rounded typically with a euchromatic nucleus and prominent nucleolus
How are neurotransmitters deactivated in the synaptic cleft?
Recapture or degradation
What two processes are found in pseudounipolar neurons? How do they work together?
Peripheral process collects information and Central process delivers it to central nervous system
Which cells form a lipid layer surrounding PNS axons and envelop unmyelinated axons?
What 4 supports cells are found in the CNS?
With high-affinity reuptake aside, how are the other 20% of neurotransmitters broken down?
Through enymes associated with the synpatic membrane. Ex. acetylcholine broken down into acetate and choline
What are two types of somesthetic receptors? Where are each found?
Free nerve endings - mediate pain
Encapsulated nerve endings - Meissner's corpuscle, Pacinian corpuscle, etc.
How was can action potentials travel down an axon?
What are two types of anterograde transport? How long does each one take?
Slow axonal transport and fast axonal transport
Where does an axon begin from the cell body?
The axon hillock
What are two types of astrocytes? Where are they found?
Protoplasmic astrocytes found in gray matter, numerous short branching processes called perivascular feels along blood capillaries.
Fibrous astrocytes have prominent cytoskeleton and are found in white matter. Have fewer processes with less branching
How does botulinum (neurotoxic) affect the axon terminal of neurons?
Prevents release of acetylcholine from synaptic vesicles
Where are satellite cells found?
In ganglia of PNS, surrounding individual cell bodies of neurons. The provide pathways for metabolic exchange and provide electrical insulation
Are ependymal cells true epithelial tissue?
No, while they are a form a simple cuboidal, they have no basil lamina. Covered in microvilli
Describe the steps in a chemical synapse
1) An action potential reaches the axon terminal
2) This causes opening of Ca++ channels
3) Ca++ in the axon temrinal causes the release of neurotransmitters into the synaptic cleft
4) These neurotransipers bind to post synaptic membrane proteins and cause local depolarization
What are two types of sensory nerve endings?
Special sense nerve endings (smell, sight, hearing, and equilibrium)
What is the role of astrocytes?
Moving metabolic substances between blood and nerve cells, forming the BBB.
Numerous mitochondria and large nuclei
What are the two major types of synapses?
Electrical and Chemical
How does the rabies virus affect a person after a bite?
1) The virus replicates in the muscle cell over 1-2 weeks
2) After replication, virus finds a motor endplate
3) Virus enters synaptic terminal and travels up the axon via retrograde axonal transport
4)After reaching the body of the motor neuron, it can spread to other neurons
5) Once the CNS is affected, severe inflamation occurs. Changes in light intensity or any sounds can cause seizures.
6) Ends up in salivary glands and can be transmitted during a bite
What does a motor end-plate consist of?
Axon terminal with presynaptic vesicles containing acetylcholine
Synaptic cleft space between nerve cell and muscle cell
Sarcolemma of a muscle cell forms junction folds and receptors for acetylcholine are found there
Which receptors are formed by stacks of lamellae into cylindrical structures, providing sense of touch?
How do oligodendroccytes mylinate CNS neurons?
Tongue-like projections of one oligodendrocyte wrap around multiple spots of a neuron (Nodes of Ranvier are between)
In a neuron, where do you find well-developed SER but no Nissl bodies or ribosomes?
What percentage of neurotransmitters are recaptured? Under what mechanism?
80% via high-affinity reuptake (reincorporated by endocytosis into vesicles ready for repackaging)
Ex. catecholamines (dopamine and norepinephrine))
What is the name of a neuron cell body?
What is the end of an axon called that communicates with other cells?
The axon terminal
What results from an inhibitory synapse?
A negative potential, hyperpolarization of the postsynaptic membrane making the ability to generate an action potential less likely
Which way are sodium ions pumped in a nerve cell? What kind of resting membrane potential does this cause?
Sodium is actively pumped out, causing a negative resting membrane potential
Which CNS support cell is the largest?
How many axons can a neuron have?
What makes up the well developed cytoskeleton of a neuron?
Neurofilaments (neuron specific intermediate filament), along with microfilaments and microtubules
What is myathenia gravis and how does it affect motor endplates?
An autoimmune disease causing extreme muscle weakness
Auto-antibodies to acetylcholine receptor are produced, binding to receptor sites, weakening the muscle responses to nerve stimuli
What is the difference between anterograde flow and retrograde flow?
Anterograde flow: from the perikaryon to periphery of axon. Done by kinesins
Retrograde flow: from the axon to the perikaryon. Dobe by dyneins
What disease causes partial loss of myelin in the CNS and can result in loss of sensitvity and partial paralysis?
What are microglial cells and what disease are they associated with?
Phagocytes with dark indented nuclei
Describe the differences of a schwann cells role in myelinated vs unmyelinated fibers?
In myelinated, a single axon is in the middle of the sheath. Plasma membrane layers of the schwann cells fuse to create a lipoprotein complex. Action potentials travel through saltadory conduction
In unmyelinated, serveral axons enveloped by one cell. Action potentials here are wave-like.
What are the only neurons in an adult human body that are replaced on a regular basis?
Besides allowing for rapid depolarization travel down an axon, what can occur at Nodes of Ranvier?
What surrounds most neurons to aid in signal conduction, acting as insulation?
What are two types of support cells in the PNS?
Schwann cells and satellite cells
What are 4 types of synapses?
Axodendritic, axosomatic, axoaxonic, and motor end-plate
What does fast axonal transport move?
membrane bound organelles including SER compartments, synaptic vesicles, and mitochondria
Why can't neurons undergo cellular division? What, however, is sometimes retained and why?
They lack centrioles.
Centrosome, potential contribution to microtubule nucleation
What results from an excitatory synapse?
Depolarization of the following neuron's plasma membrane, multiple of which can contribute to an action potential
How does curare affect the motor endplate?
Binds to acetylcholine receptors and acts as a muscle relaxant
What are the three types of neurons in the body (related to shape)? Where are each predominantly found?
Pseudounipolar (dorsal root ganglia and some crainial nerve ganglia)
Bipolar (sensory, primarily in major sense organs such as eye retina, elfactory mucosa, and cochlea/semicircular canals)
Multipolar (most common, motor and interneurons)
Which two toxins can disable chemical synapses, including motor endplates?
Curare toxin and Botulinum toxin
Which receptors are the largest of encapsulated nerve endings, consisting of concentric sheets of CT to respond to vibrations and deep pressure (pancreas, mesenteries, skin)
Neurons form synapses to allow them to communicate with what 3 structures?
Which support cell stains positive for glial fibrillary acidic protein (GFAP)?
Astrocytes, cytoskeleton made of intermetiate filaments
What are two types of chemical synapses?
Excitatory and Inhibitory
What are astrocytomas?
Brain tumors caused by astrocytes.
20% of all brain tumors are caused by astrocytes
80% of tumors that originate in the brain are cuased by astrocytes
What is the continuation of the plasma membrane called that an axon is enclosed in?
Which multipolar neurons have a short axon?
Golgi type 2, found as interneurons in CNS
What is glial scar?
Formed when local damage to the brain causes astrocytes to do gliosis (change to glial cells in brain)
What are the most common neuroglial cells? What makes them distinct?
Oligodendrocytes, smaller than astrocytes
Small nuclei, abundant SER, and prominent golgi
Which multipolar neurons have a long axon? Where are their found?
Golgi type 1, found in motor nuclei
What are well developed RER denses structures called? How are they formed?
Nissl bodies, formed by parallel arrays of RER cisternae