Neurons Flashcards
What is Nissl substance?
Rough endoplasmic reticulum and polysomes
Important for protein synthesis in neurons.
What is the axon hillock?
Area of soma where axon arises and site of initiation of action potentials
Critical for the generation of action potentials.
What are unipolar neurons?
Single stem that bifurcates to form 2 processes: peripheral and central process
Innervate peripheral tissues and bring somatic and visceral sensory information to CNS.
Where are bipolar neurons located?
In retina, spiral ganglion of cochlea, vestibular ganglion of vestibular organ, and olfactory epithelium
They have 2 processes.
What characterizes multipolar neurons?
One axon and many dendrites
Most prevalent type of neuron.
What are interneurons?
Local-circuit neurons that transmit signals to sensory neurons, motor neurons, or other interneurons
Important for reflexes and neural processing.
Define resting membrane potential.
Potential difference across membrane in unstimulated state
Inside of cell is more negative than extracellular environment.
What is the ionic composition of extracellular fluid?
High sodium, low potassium, high chloride
Important for establishing resting membrane potential.
What is the ionic composition of intracellular fluid?
High potassium, low sodium, high protein (anions)
Contributes to the negative charge inside the cell.
What is the role of the Na/K ATPase pump?
Exchanges 3 Na for 2 K in, maintaining more negative charge inside
Requires ATP to function.
What triggers the generation of action potentials?
Rapid change in permeability of the neuron to Na/K
Generated at axon hillock.
What happens at threshold potential?
Cell reaches -55 mV, opens voltage gated Na channels
Leads to rapid depolarization.
What occurs during repolarization?
Na channel gate closes and voltage gated K channels open
K exits cell, restoring internal negativity.
What is hyperpolarization?
K channels remain open, making the cell excessively negative
Results in refractory period where action potentials cannot be generated.
What is the difference between absolute and relative refractory periods?
Absolute: no AP can be generated; Relative: very strong stimulus can generate AP
Key for understanding neuron firing.
What factors affect conduction velocity?
Larger diameter axons and myelinated axons
Higher conduction velocity with less resistance to ion flow.
What is saltatory conduction?
Propagation of action potentials in myelinated axons via nodes of Ranvier
Increases conduction speed.
Fill in the blank: The net effect of ionic gradients is sodium moving _______.
into cells
Essential for depolarization.
What effect does hyperkalemia have on neurons?
Potassium stays inside, depolarizes, making neurons more excitable
Can lead to cardiac arrhythmias.
What happens during hypokalemia?
K moves out, hyperpolarizes, making it difficult to generate AP
Can cause weakness.
What is the result of hypercalcemia on Na channels?
More Na channels closed, leading to hyperpolarization
Can result in weakness.
What is the effect of hypocalcemia on action potentials?
More Na channels open, easier to generate AP
Can lead to seizures, twitching, or tetany.
True or False: Hyponatremia has a significant effect on action potentials due to many leak channels.
False
Not a significant effect on AP.
What is a synapse?
A junction between two neurons where neurotransmission occurs
Synapses can be electrical or chemical.
What characterizes an electrical synapse?
Ion channels connect cytoplasm of presynaptic and postsynaptic cells at a gap junction
Ionic currents flow passively through gap junction pores.
Where do electrical synapses commonly occur?
Hypothalamus, neocortex, hippocampus, thalamus
These areas are critical for various neural functions.
What is a chemical synapse?
Contains no gap junctions and has a narrow synaptic cleft
It involves neurotransmitter release and receptor binding.
What is the sequence of events in a chemical synapse?
Action potential arrival, depolarization, Ca influx, NT release, and receptor binding
This process is crucial for signal transmission between neurons.
What neurotransmitter is exclusively used in neuromuscular synapses?
Acetylcholine
It is responsible for muscle contraction.
List three neurotransmitters in the peripheral nervous system.
- Acetylcholine
- Norepinephrine
- Epinephrine
These neurotransmitters play key roles in various physiological responses.
What are the primary excitatory neurotransmitters?
- Glutamate
- Aspartate
They are essential for promoting neuronal firing.
What are the primary inhibitory neurotransmitters?
- GABA
- Glycine
They help to prevent excessive neuronal firing.
What role do microglia play in the CNS?
Act as macrophages, proliferate when activated, and release NO to prevent viral replication
They are crucial for immune response in the CNS.
What do ependymal cells cover?
Ventricles and central canal
They are involved in the production and circulation of cerebrospinal fluid.
What is the function of oligodendrocytes?
Form myelin sheaths on adjacent axons
They are critical for the insulation of neuronal axons in the CNS.
What do Schwann cells do?
Wrap plasma membrane around axon to form myelin internode
They are essential for myelination in the peripheral nervous system.
What are the functions of astrocytes?
- Provide structural and metabolic support
- Seal CNS surfaces
- Release neurotrophic factors
- Exchange ions
- Repair after injury
They play a multifaceted role in maintaining CNS homeostasis.
What causes astrocytic swelling?
Hypoxia, trauma, and hypoglycemia
This can lead to changes in ionic composition affecting neuronal function.
What is astrocytic hyperplasia?
Proliferation of astrocytes around necrotic areas due to destructive lesions
It occurs in response to trauma and is part of the repair process.
Fill in the blank: Serotonin (5-HT) is derived from _______.
tryptophan
Fill in the blank: Histamine is derived from _______.
histidine
True or False: Acetylcholine is released by cholinergic neurons.
True
