Nervous Tissue and Neurons

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Questions and Answers

Which type of neuron is characterized by having only one extension that branches into two?

Pseudounipolar (correct)

Unipolar

Multipolar

Bipolar

What is the primary function of motor neurons?

Receive sensory impulses from the environment

Maintain resting potential in neurons

Transmit impulses from the CNS to muscles or glands (correct)

Connect sensory neurons to other interneurons

What is the resting potential of a neuron typically measured at?

-70 mV (correct)

-80 mV

-90 mV

-60 mV

Which type of neuron is most abundant in the nervous system?

Multipolar Signup and view all the answers

During an action potential, what primarily causes the change in membrane potential?

Increased Na+ permeability followed by K+ influx Signup and view all the answers

What is the process called when action potentials jump from one nodule of Ranvier to another?

Saltatory conduction Signup and view all the answers

What role do Na+-K+ pumps play in maintaining neuron function?

They maintain ion concentrations across the membrane. Signup and view all the answers

Which type of neuron receives sensory information and transmits it to the CNS?

Sensory neurons Signup and view all the answers

What is the primary role of neurons in the nervous tissue?

Receiving and transmitting nerve impulses Signup and view all the answers

Which part of the neuron is primarily responsible for receiving stimuli?

Dendrites Signup and view all the answers

What is the function of myelin sheaths around axons?

To increase the speed of impulse conduction Signup and view all the answers

What structures develop between the myelin sheaths on an axon?

Ranvier nodules Signup and view all the answers

Which component is NOT typically found in the cytoplasm of a neuron?

Thylakoids Signup and view all the answers

Which type of cells in nervous tissue provide support but do not transmit impulses?

Glial cells Signup and view all the answers

What primarily facilitates the axonic transport of materials necessary for nerve function?

Cytoskeleton filaments Signup and view all the answers

What is the structural feature of the nucleus in a neuron?

It is centrally located and large Signup and view all the answers

What is the primary function of the presynaptic neuron in a synapse?

To transmit the impulse to another cell Signup and view all the answers

Which type of synapse is characterized by the direct flow of ions between cells?

Electrical synapse Signup and view all the answers

What gap is present between the presynaptic and postsynaptic neurons in a chemical synapse?

Synaptic cleft Signup and view all the answers

Which type of synapse occurs more frequently in mammals?

Chemical synapse Signup and view all the answers

What occurs when an excitatory neurotransmitter binds to the postsynaptic receptor?

It depolarizes the postsynaptic cell Signup and view all the answers

Which of the following is NOT a type of neuroglial cell in the CNS?

Schwann cells Signup and view all the answers

What role do astrocytes play in the central nervous system?

Providing structural support and protection to neurons Signup and view all the answers

Which glial cell type is known for forming myelin sheaths in the CNS?

Oligodendrocytes Signup and view all the answers

What is the primary function of fibrous astrocytes in the CNS?

Controlling the blood-brain barrier Signup and view all the answers

How do oligodendrocytes differ from astrocytes?

Oligodendrocytes maintain myelin in the CNS. Signup and view all the answers

What type of cells are ependymocytes and what is their main role?

They are cylindrical cells that line the ventricles and aid in cerebrospinal fluid movement. Signup and view all the answers

What distinguishes Schwann cells from oligodendrocytes?

Schwann cells surround axons to form sheaths in the PNS. Signup and view all the answers

What is the primary role of microglial cells in the CNS?

To eliminate cellular debris and protect against infections. Signup and view all the answers

In which part of the nervous system are satellite cells found?

Peripheral nervous system Signup and view all the answers

Which statement about myelin sheaths is correct?

One oligodendrocyte can coat several axons with myelin. Signup and view all the answers

What occurs at the Ranvier nodules in myelinated fibers?

They allow for faster action potential conduction. Signup and view all the answers

Study Notes

Nervous Tissue

Nervous tissue is a complex communication system, rapidly and precisely coordinating functions within the organism.
Primary cells are neurons, specialized receptors receiving stimuli and transforming them into nerve impulses.
Neurons transmit information internally and externally, or send instructions throughout the body.
Glial cells (neuroglia) support neurons without transmitting impulses. They provide diverse support mechanisms.

Neurons

Neurons are excitable cells that receive and transmit impulses.
Neurons consist of a cell body, dendrites, and an axon.
The cell body (soma or perikaryon) contains the nucleus and most organelles.
Dendrites receive stimuli, while the axon transmits impulses.
Neuron shapes include polygonal, starry, or round, varying based on location.
Neuron nuclei are rounded, centrally located, and display high activity.
Cytoplasm has extensive rough endoplasmic reticulum (RER) and ribosomes, which can form Nissl bodies.

Neuronal Structure and Function

Dendrites extend from the cell body and receive stimuli from other neurons.
Axons emerge from the cell body, transmitting stimuli to other neurons, muscles, or glands.
Axons often branch, terminating in terminal buttons/synaptic buttons for communication.
Myelin sheaths surround axons, increasing impulse transmission speed.
Gaps in the myelin sheath (Ranvier nodes) are vital for signal propagation.

Axonic Transport

Axons transport materials (organelles, macromolecules, enzymes) from the cell body to the terminal buttons and vice-versa.
This transport is crucial for maintaining axonal structure and function.
Cytoskeletal filaments (neurofilaments, neurotubules) are essential for axonal transport.

Neuronal Classification (Morphological)

Neurons are classified based on their shape and extension arrangement:
- Unipolar: single extension acting as an axon; rare in humans.
- Pseudounipolar: single extension that divides into two; found in some ganglia.
- Bipolar: two extensions (one dendrite, one axon); present in special locations (inner ear, olfactory mucosa).
- Multipolar: numerous dendrites and a single axon; the most common type, found throughout the nervous system.

Neuronal Classification (Functional)

Neurons are functionally categorized:
- Motor neurons: originate in the CNS and send impulses to muscles or glands.
- Sensory neurons: receive impulses from internal/external environments; transmit to the CNS for processing.
- Interneurons: connect sensory and motor neurons within the CNS.

Action Potential

Nerve impulses are electrical signals generated by membrane depolarization.
Neurons and other cells are polarized (resting potential ~ -70mV) due to ion concentration differences.
Na+/K+ pumps maintain this ion gradient.
Action potential involves depolarization and repolarization (all-or-nothing).
Action potential propagation occurs along the axon; adjacent channels are depolarized in response to a signal.

Saltatory Conduction

Saltatory conduction is faster because it jumps from node to node in myelinated axons, skipping areas with few Na+ channels..
In non-myelinated axons, the action potential spreads along the entire axon.

Synapse

A synapse is the junction where impulses are transmitted from one neuron to another cell.
A presynaptic neuron transmits, and a postsynaptic cell receives.
Synapses can be electrical (quick, rare) or chemical (common type; involves neurotransmitters).
Chemical synapses involve neurotransmitter release across the synaptic cleft and binding to postsynaptic receptors.

Neuroglia (CNS Glia)

Neuroglia (glial cells) support neurons metabolically and mechanically; also protecting them.
- Astrocytes: large glial cells maintaining the blood-brain barrier.
- Oligodendrocytes: form myelin sheaths in the CNS.
- Microglia: phagocytes that eliminate cellular debris and protect from infections.
- Ependymal cells: line the ventricles and central canal of the CNS and facilitate cerebrospinal fluid circulation.

Glia of the PNS

Schwann cells: form myelin sheaths in the PNS.
Satellite cells: surround neuronal cell bodies in ganglia, providing support.

Nervous System

CNS (Central Nervous System): comprises the brain and spinal cord.
PNS (Peripheral Nervous System): outside the CNS, composed of nerves and ganglia; functionally divided into sensory and motor components.
Sensory (afferent): carries impulses to the CNS.
Motor (efferent): carries impulses from the CNS; further divided into somatic (voluntary) and autonomic (involuntary).

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Description

Explore the intricate world of nervous tissue and neurons in this quiz. Learn about the structure and function of neurons, their role in communication within the body, and the supporting role of glial cells. Test your knowledge on these essential components of the nervous system.