Nervous System Organization Quiz

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Questions and Answers

What is the primary function of sensory nerves?

To convert electrical impulses into chemical signals

To send information to the central nervous system (correct)

To control muscle contractions

To communicate with glands

Which type of nerve is responsible for controlling muscle and gland functions?

Reflex nerves

Motor nerves (correct)

Interneurons

Sensory nerves

What is a synapse?

The connection between the spinal cord and muscles

A type of neurotransmitter

The area where electrical impulses are delivered

The junction between one neuron and the next cell (correct)

What role do neurotransmitters play in the nervous system?

They convert electrical impulses into chemical signals Signup and view all the answers

Which of the following best describes reflex arcs?

Interconnections between sensory and motor nerves Signup and view all the answers

What is another name for synapses between nerve and muscle cells?

Neuromuscular junctions Signup and view all the answers

Which term describes the signals sent by sensory nerves?

Nerve impulses Signup and view all the answers

What distinguishes motor nerves from sensory nerves?

Motor nerves control body activities; sensory nerves do not Signup and view all the answers

What are action potentials characterized by?

Brief, rapid, and large changes in membrane potential Signup and view all the answers

Which type of channels open during the depolarization phase of an action potential?

Voltage-gated Na+ channels Signup and view all the answers

What happens to the membrane potential after K+ channels open?

Membrane potential decreases and returns to resting level Signup and view all the answers

How does the strength of an action potential change as it travels?

It remains constant Signup and view all the answers

What initiates an action potential?

Threshold potential being reached due to Na+ influx Signup and view all the answers

What is the resting membrane potential typically around?

-70mV Signup and view all the answers

What is the main function of voltage-gated K+ channels during an action potential?

To help return the membrane potential to resting levels Signup and view all the answers

What occurs after the closing of voltage-gated Na+ channels during an action potential?

Voltage-gated K+ channels open Signup and view all the answers

What occurs when the membrane reaches the threshold potential?

Voltage-gated Na+ channels open Signup and view all the answers

What is the threshold potential at which an action potential is generated?

-50 mV Signup and view all the answers

What primarily causes the flow of sodium ions into the intracellular fluid (ICF)?

Opening of voltage-gated Na+ channels Signup and view all the answers

What is responsible for restoring the membrane potential to its resting state?

K+ efflux Signup and view all the answers

During the absolute refractory period, what is primarily inactivated?

Sodium channels Signup and view all the answers

What is one consequence of K+ movement out of the cell during repolarization?

Restoration of resting membrane potential Signup and view all the answers

How does the refractory period affect action potentials?

It prevents the generation of a new action potential after a stimulus Signup and view all the answers

What result does the opening of VGPCs during repolarization lead to?

Outward flow of potassium ions Signup and view all the answers

What drains into the T-tubes in skeletal muscle?

Sarcoplasmic reticulum Signup and view all the answers

What type of neurons run from the CNS to the muscles and glands?

Somatic motor neurons Signup and view all the answers

Where are the cell bodies of motor neurons located?

Ventral horn Signup and view all the answers

What occurs at the neuromuscular junction?

Chemical transmission between neuron and muscle Signup and view all the answers

What do action potentials traveling down motor neurons cause?

Contraction of skeletal muscle fibers Signup and view all the answers

What is created from a single vesicle release at the neuromuscular junction?

Miniature end plate potentials (mEPP) Signup and view all the answers

What type of muscle fibers are innervated by motor neurons?

Skeletal muscle fibers Signup and view all the answers

What forms a chemical synapse at the neuromuscular junction?

Motor neuron terminals and muscle fibers Signup and view all the answers

What is the primary function of sensory neurons?

To carry signals towards the CNS Signup and view all the answers

Which part of the nervous system is responsible for voluntary movements?

Motor nervous system Signup and view all the answers

What defines a neurotransmitter?

A chemical released by neurons to transmit signals Signup and view all the answers

During neurotransmission at the neuromuscular junction, which enzyme degrades the neurotransmitter acetylcholine?

Acetylcholinesterase Signup and view all the answers

Which of the following best describes nicotinic receptors at the neuromuscular junction?

They are ionotropic receptors that mediate fast synaptic transmission Signup and view all the answers

Which division of the peripheral nervous system is responsible for involuntary control of smooth muscles?

Autonomic nervous system Signup and view all the answers

What occurs during depolarization of the plasma membrane?

The inner cell becomes more positive relative to the outside Signup and view all the answers

What is the role of the axon in a neuron?

To transmit signals away from the cell body Signup and view all the answers

Which type of neuron would have multiple projections from its cell body?

Multipolar neurons Signup and view all the answers

Which system is NOT part of the autonomic nervous system?

Somatic nervous system Signup and view all the answers

Study Notes

Organization of the Nervous System

The nervous system is divided into the central nervous system (CNS) and the peripheral nervous system (PNS).
The CNS consists of the brain and spinal cord.
The PNS consists of sensory nerves (afferent nerves) and motor nerves (efferent nerves)
The PNS can be further divided into the afferent division and the efferent division.
The afferent division transmits information from the body to the CNS (arriving).
The efferent division transmits information from the CNS to the body (exiting, effector organ)
The efferent division can be further divided into the somatic nervous system and the autonomic nervous system.
The somatic nervous system controls skeletal muscle.
The autonomic nervous system controls smooth muscle, cardiac muscle, exocrine glands, and some endocrine glands.
The autonomic nervous system has three subdivisions: sympathetic, parasympathetic, and enteric.

Structural Units of the Nervous System: Neurons

Neurons have a cell body (soma), dendrites, and an axon.
Dendrites are projections from the cell body that receive impulses.
Axons are projections from the cell body that transmit impulses.
The axon hillock is the section where the axon begins.
The telodendron is the end of the axon.
The synaptic terminal is the end of the telodendron where the neuron makes a connection with another cell.

Signal Transduction

Dendrites or the cell body receive signals that cause a depolarization or hyperpolarization of the plasma membrane.
Axons propagate output signals: action potentials.

Ways to Classify Neurons (I)

Morphology (shape) : Neurons are classified as bipolar (two projections from cell body) or multipolar (multiple projections from cell body)
Afferent and Efferent nerves: Neurons that transmit information towards the CNS are afferent (arriving). Neurons that transmit information from the CNS are efferent (exiting, effector organ).
Neurotransmitter: Neurons are classified by the substance or chemical they release (e.g. dopamine, acetylcholine).

Functional Ways to Classify Neurons/Nerves (II)

Sensory nerves send information to the CNS about the internal and external environment.
Motor nerves control the activity of the body by controlling muscle and gland functions.
The motor response to sensory input requires integration of information through interconnections between nerves and reflex arcs.

The Synapse

The synapse is the junction between one neuron and the next cell.
Specialised structures at the synapse convert electrical impulses to chemical signals for communication between cells (electro-chemical coupling).
Types of synapse:
- Nerve-Nerve
- Nerve-Organ / Organ-Nerve
- Nerve-Muscle
- Nerve-Gland
Synapses between nerve and muscle cells are also called neuromuscular junctions or motor end plates.

Neurotransmitters

Neurotransmitters are typically small, rapid-acting molecules (e.g. dopamine, acetylcholine).

Potentials (II): Action Potentials

Action potentials (APs) are brief, rapid, large changes in membrane potential, during which the potential reverses.
APs involve only a small portion of the total excitable cell membrane at any given time.
APs do not decrease in strength as they travel from their site of initiation.

The Refractory Period - One Way Traffic

The refractory period is the time during which a further stimulus applied to the neuron or muscle fiber will not trigger another action potential.
The refractory period is due to the inactivation of sodium channels (absolute refractory period) and repolarization brought about by the opening of potassium channels and potassium ions (K+) movement out of the cell (relative refractory period).

Skeletal Muscle

Skeletal muscle is controlled by the somatic nervous system.

Peripheral Nervous System & Nerve-Muscle Junctions

The output of the PNS consists of motor neurons running from the CNS to the muscles and glands - called effectors - that take action.
Nerve (somatic motor nerves) – skeletal muscle – neuromuscular junction (NMJ).
Nerve (Autonomic NS) – cardiac or smooth muscle.

Motor Neurons Innervate Skeletal Muscle Fibers

Cell bodies of motor neurons are located in the ventral horn of the spinal cord.
These neurons have thick, myelinated axons (somatic efferent fiber).
Motor neurons lose their myelin sheath at the motor end plate.
At the motor end plate, each axon terminal forms a neuromuscular junction with a single muscle fiber.

The Neuromuscular Junction (I)

Motor neurons and skeletal muscle fibers are chemically linked at the NMJ.
Action potentials traveling down motor neurons cause the contraction of skeletal muscle fibers.
The NMJ is always excitatory.
Single vesicle release at the NMJ creates miniature end plate potentials (mEPP).
Action potentials release neurotransmitter acetylcholine (ACh).

Neuromuscular Junction

The NMJ is a chemical synapse between a motor neuron and a muscle fiber.
The NMJ is responsible for the transmission of nerve impulses from a motor neuron to a muscle fiber.
The NMJ is essential for the activation of muscle contraction.

What is a Neuromuscular Junction?

A chemical synapse between a motor neuron and a muscle fiber.

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Description

Test your knowledge on the organization of the nervous system, including the central and peripheral nervous systems. This quiz covers the divisions of the PNS, the somatic and autonomic nervous systems, and the functional roles of neurons. Challenge yourself to understand how these systems work together to transmit information in the body.