Neuroscience: Neurons and Synaptic Potentials

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Questions and Answers

Which of the following neurotransmitters is classified as a biogenic amine?

GABA

Glutamate

Serotonin (correct)

Acetylcholine

Which of the following statements is true regarding neurotransmitter removal from the synaptic cleft?

A specific mechanism exists for their removal. (correct)

Transporters are only found in the postsynaptic membrane.

All neurotransmitters are removed via enzymatic breakdown only.

Neurotransmitters diffuse away and are not recycled.

Which type of neurotransmitter includes amino acids?

Biogenic amines

Gaseous neurotransmitters

Peptide neurotransmitters

Classical low molecular weight neurotransmitters (correct)

Which of the following neurotransmitters acts as a neuromodulator?

Adenosine Signup and view all the answers

What is the role of nitric oxide in neurotransmission?

It serves as a signaling molecule that diffuses freely across membranes. Signup and view all the answers

Which neurotransmitter is primarily associated with muscle activation at the neuromuscular junction?

Acetylcholine Signup and view all the answers

What is the primary effect of EPSPs on the post-synaptic membrane?

They depolarize the membrane. Signup and view all the answers

What determines the final response of a post-synaptic cell during synaptic integration?

The summation of both EPSPs and IPSPs. Signup and view all the answers

Which of the following correctly describes the pathway formed by motor neurons?

They form a convergent pathway. Signup and view all the answers

Which of the following ions typically contributes to the hyperpolarization observed in IPSPs?

K+ Signup and view all the answers

Which criterion is NOT necessary for a substance to qualify as a neurotransmitter?

It must be released in response to an action potential. Signup and view all the answers

What is the primary role of neurotransmitters?

To facilitate communication between neurons. Signup and view all the answers

What is the primary neurotransmitter released by post-ganglionic sympathetic neurons?

Norepinephrine Signup and view all the answers

Which part of the nervous system is responsible for the 'rest and digest' response?

Parasympathetic nervous system Signup and view all the answers

What is the typical composition of a synapse in terms of protein involvement?

60 different proteins Signup and view all the answers

Where do pre-ganglionic sympathetic neurons originate from?

Thoracic and lumbar regions Signup and view all the answers

Which of the following statements about the neuromuscular junction (NMJ) is true?

It is covered by Schwann cells. Signup and view all the answers

What primarily determines the type of neurotransmitter released by a neuron?

The type of neuron (pre or post-ganglionic) Signup and view all the answers

What effect does the sympathetic nervous system have on the heart?

Increases both rate and force of contraction Signup and view all the answers

Which neurotransmitter is released at the neuromuscular junction?

Acetylcholine Signup and view all the answers

Which physiological response occurs when the parasympathetic nervous system is activated?

Increased gastrointestinal motility Signup and view all the answers

What role do dendritic arborizations play in neuronal function?

Enhance connectivity and signal reception Signup and view all the answers

Study Notes

Sensory and Motor Neurons

Sensory neurons create a divergent pathway, transmitting signals away from sensory receptors.
Motor neurons form a convergent pathway, integrating multiple signals to elicit a response.

Synaptic Potentials

EPSPs (Excitatory Post-Synaptic Potentials)
- Depolarize the post-synaptic membrane.
- Typically result from increased permeability to Na+ or Ca2+.
IPSPs (Inhibitory Post-Synaptic Potentials)
- Hyperpolarize the post-synaptic membrane.
- Generally caused by increased permeability to Cl- or K+.

Synaptic Integration

Post-synaptic cells can receive thousands of synaptic inputs, both excitatory and inhibitory.
Interaction between EPSPs and IPSPs through synaptic integration leads to the final cellular response.

Neurotransmitter Characteristics

Over 50 different neurotransmitters exist; neurons are named according to the neurotransmitter they release (e.g., cholinergic, noradrenergic).
Criteria for Classification as a Neurotransmitter:
- Synthesized in the neuron.
- Present in the presynaptic terminal in sufficient amounts.
- Mimics action of endogenously released transmitter when applied externally.
- Has a mechanism for removal from the synaptic cleft.

Common Neurotransmitters

Classical Neurotransmitters:
- Acetylcholine
- Noradrenaline
- Adrenaline
- Dopamine
- Serotonin (5-HT)
- Histamine
- Glutamate
- GABA
- Glycine
Other potential neurotransmitters include ATP, adenosine, nitric oxide, and over 50 peptide neurotransmitters.

Autonomic Nervous System Functions

Sympathetic Division:
- Dilates pupils, increases heart rate and force, constricts arterioles (excluding skeletal muscle and coronary circulation), relaxes bronchial smooth muscle, reduces gut motility, stimulates liver processes (glycogenolysis and gluconeogenesis), and relaxes the bladder.
Parasympathetic Division:
- Constricts pupils, decreases heart rate and force, contracts bronchial smooth muscle, increases gut motility, relaxes sphincters, and contracts the bladder.

Pre and Post-Ganglionic Neuron Functions

Sympathetic Nervous System:
- Pre-ganglionic neurons exit the thoracic and lumbar regions, synapsing near the spinal cord, using acetylcholine (ACh).
- Post-ganglionic neurons release noradrenaline (NA) at effectors.
Parasympathetic Nervous System:
- Pre-ganglionic neurons exit from the brainstem and sacral region, synapsing near effector organs, also using ACh.
- Post-ganglionic neurons remain cholinergic, releasing ACh.

Synaptic Anatomy and Transmission

Neurons can form ‘1 to 1’ or ‘1 to many’ synapse contacts.
Synaptic structure is complex, involving numerous proteins for structural roles and molecule trafficking.
Dendritic arborization is essential for neuronal function and connectivity.

Neuromuscular Junction (NMJ)

NMJ is a specialized synapse between α-motor neurons and muscle fibers, with each neuron synapsing with several fibers, forming a motor unit.
α-motor neurons originate from the CNS and are characterized by fast, myelinated fibers.
ACh is the neurotransmitter at the NMJ, and it's distinct due to its association with Schwann cells.

Reflex Action

The myotatic reflex, such as the knee-jerk reflex, illustrates basic synaptic transmission and neuromuscular interaction in response to stimuli.

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Description

Explore the intricate functions of sensory and motor neurons, including the divergent and convergent pathways they form. This quiz also delves into excitatory and inhibitory post-synaptic potentials (EPSPs and IPSPs), and their roles in neuron communication. Test your understanding of these essential concepts in neuroscience.