Neurons

Question 1

What is Nissl substance?

Answer 1

Rough endoplasmic reticulum and polysomes

Important for protein synthesis in neurons.

Question 2

What is the axon hillock?

Answer 2

Area of soma where axon arises and site of initiation of action potentials

Critical for the generation of action potentials.

Question 3

What are unipolar neurons?

Answer 3

Single stem that bifurcates to form 2 processes: peripheral and central process

Innervate peripheral tissues and bring somatic and visceral sensory information to CNS.

Question 4

Where are bipolar neurons located?

Answer 4

In retina, spiral ganglion of cochlea, vestibular ganglion of vestibular organ, and olfactory epithelium

They have 2 processes.

Question 5

What characterizes multipolar neurons?

Answer 5

One axon and many dendrites

Most prevalent type of neuron.

Question 6

What are interneurons?

Answer 6

Local-circuit neurons that transmit signals to sensory neurons, motor neurons, or other interneurons

Important for reflexes and neural processing.

Question 7

Define resting membrane potential.

Answer 7

Potential difference across membrane in unstimulated state

Inside of cell is more negative than extracellular environment.

Question 8

What is the ionic composition of extracellular fluid?

Answer 8

High sodium, low potassium, high chloride

Important for establishing resting membrane potential.

Question 9

What is the ionic composition of intracellular fluid?

Answer 9

High potassium, low sodium, high protein (anions)

Contributes to the negative charge inside the cell.

Question 10

What is the role of the Na/K ATPase pump?

Answer 10

Exchanges 3 Na for 2 K in, maintaining more negative charge inside

Requires ATP to function.

Question 11

What triggers the generation of action potentials?

Answer 11

Rapid change in permeability of the neuron to Na/K

Generated at axon hillock.

Question 12

What happens at threshold potential?

Answer 12

Cell reaches -55 mV, opens voltage gated Na channels

Leads to rapid depolarization.

Question 13

What occurs during repolarization?

Answer 13

Na channel gate closes and voltage gated K channels open

K exits cell, restoring internal negativity.

Question 14

What is hyperpolarization?

Answer 14

K channels remain open, making the cell excessively negative

Results in refractory period where action potentials cannot be generated.

Question 15

What is the difference between absolute and relative refractory periods?

Answer 15

Absolute: no AP can be generated; Relative: very strong stimulus can generate AP

Key for understanding neuron firing.

Question 16

What factors affect conduction velocity?

Answer 16

Larger diameter axons and myelinated axons

Higher conduction velocity with less resistance to ion flow.

Question 17

What is saltatory conduction?

Answer 17

Propagation of action potentials in myelinated axons via nodes of Ranvier

Increases conduction speed.

Question 18

Fill in the blank: The net effect of ionic gradients is sodium moving _______.

Answer 18

into cells

Essential for depolarization.

Question 19

What effect does hyperkalemia have on neurons?

Answer 19

Potassium stays inside, depolarizes, making neurons more excitable

Can lead to cardiac arrhythmias.

Question 20

What happens during hypokalemia?

Answer 20

K moves out, hyperpolarizes, making it difficult to generate AP

Can cause weakness.

Question 21

What is the result of hypercalcemia on Na channels?

Answer 21

More Na channels closed, leading to hyperpolarization

Can result in weakness.

Question 22

What is the effect of hypocalcemia on action potentials?

Answer 22

More Na channels open, easier to generate AP

Can lead to seizures, twitching, or tetany.

Question 23

True or False: Hyponatremia has a significant effect on action potentials due to many leak channels.

Answer 23

False

Not a significant effect on AP.

Question 24

What is a synapse?

Answer 24

A junction between two neurons where neurotransmission occurs

Synapses can be electrical or chemical.

Question 25

What characterizes an electrical synapse?

Answer 25

Ion channels connect cytoplasm of presynaptic and postsynaptic cells at a gap junction ## Footnote Ionic currents flow passively through gap junction pores.

Question 26

Where do electrical synapses commonly occur?

Answer 26

Hypothalamus, neocortex, hippocampus, thalamus ## Footnote These areas are critical for various neural functions.

Question 27

What is a chemical synapse?

Answer 27

Contains no gap junctions and has a narrow synaptic cleft ## Footnote It involves neurotransmitter release and receptor binding.

Question 28

What is the sequence of events in a chemical synapse?

Answer 28

Action potential arrival, depolarization, Ca influx, NT release, and receptor binding ## Footnote This process is crucial for signal transmission between neurons.

Question 29

What neurotransmitter is exclusively used in neuromuscular synapses?

Answer 29

Acetylcholine ## Footnote It is responsible for muscle contraction.

Question 30

List three neurotransmitters in the peripheral nervous system.

Answer 30

* Acetylcholine * Norepinephrine * Epinephrine ## Footnote These neurotransmitters play key roles in various physiological responses.

Question 31

What are the primary excitatory neurotransmitters?

Answer 31

* Glutamate * Aspartate ## Footnote They are essential for promoting neuronal firing.

Question 32

What are the primary inhibitory neurotransmitters?

Answer 32

* GABA * Glycine ## Footnote They help to prevent excessive neuronal firing.

Question 33

What role do microglia play in the CNS?

Answer 33

Act as macrophages, proliferate when activated, and release NO to prevent viral replication ## Footnote They are crucial for immune response in the CNS.

Question 34

What do ependymal cells cover?

Answer 34

Ventricles and central canal ## Footnote They are involved in the production and circulation of cerebrospinal fluid.

Question 35

What is the function of oligodendrocytes?

Answer 35

Form myelin sheaths on adjacent axons ## Footnote They are critical for the insulation of neuronal axons in the CNS.

Question 36

What do Schwann cells do?

Answer 36

Wrap plasma membrane around axon to form myelin internode ## Footnote They are essential for myelination in the peripheral nervous system.

Question 37

What are the functions of astrocytes?

Answer 37

* Provide structural and metabolic support * Seal CNS surfaces * Release neurotrophic factors * Exchange ions * Repair after injury ## Footnote They play a multifaceted role in maintaining CNS homeostasis.

Question 38

What causes astrocytic swelling?

Answer 38

Hypoxia, trauma, and hypoglycemia ## Footnote This can lead to changes in ionic composition affecting neuronal function.

Question 39

What is astrocytic hyperplasia?

Answer 39

Proliferation of astrocytes around necrotic areas due to destructive lesions ## Footnote It occurs in response to trauma and is part of the repair process.

Question 40

Fill in the blank: Serotonin (5-HT) is derived from _______.

Answer 40

tryptophan

Question 41

Fill in the blank: Histamine is derived from _______.

Answer 41

histidine

Question 42

True or False: Acetylcholine is released by cholinergic neurons.

Answer 42

True