Nervous Tissue and System Anatomy

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Questions and Answers

What is a characteristic feature of unipolar neurons?

Their axon and dendrites are fused. (correct)

They have multiple dendrites.

They contain an elongated cell body.

They are primarily found in the brain.

Which type of neuron is considered rare and has one axon and one dendrite?

Anaxonic neurons

Multipolar neurons

Bipolar neurons (correct)

Unipolar neurons

Which of the following types of neurons is primarily responsible for interconnecting sensory and motor functions?

Unipolar neurons

Sensory neurons

Interneurons (correct)

Motor neurons

What type of sensory receptor is responsible for monitoring the position and movement of skeletal muscles and joints?

Proprioceptors Signup and view all the answers

Which statement correctly describes multipolar neurons?

They are the most common type of neuron. Signup and view all the answers

Which type of motor neuron innervates skeletal muscles?

Somatic motor neurons Signup and view all the answers

What role do visceral sensory neurons play?

They relay information about internal bodily functions. Signup and view all the answers

Which of the following pairs correctly associates functional neuron types?

Sensory neurons - Afferent Signup and view all the answers

What is the primary role of GABA in the central nervous system?

To inhibit postsynaptic action potentials Signup and view all the answers

Which neurotransmitter is primarily associated with emotional states and attention?

Serotonin Signup and view all the answers

What type of summation involves rapid, repeated stimuli at a single synapse?

Temporal summation Signup and view all the answers

How do neuromodulators differ from neurotransmitters in their effects?

They alter the rate of neurotransmitter release Signup and view all the answers

Which of the following is a characteristic feature of opioids?

They bind to the same receptors as endorphins Signup and view all the answers

Which biogenic amine is involved in both Parkinson's disease and cocaine use?

Dopamine Signup and view all the answers

What is the effect of a neuron receiving multiple IPSPs?

It is inhibited from producing an action potential Signup and view all the answers

What indirect mechanism can neurotransmitters use to affect cellular processes?

Activation of intracellular enzymes Signup and view all the answers

Which of the following acts on chemically gated ion channels for direct effects?

Acetylcholine Signup and view all the answers

What distinguishes the function of dissolved gases like nitric oxide in the nervous system?

They influence intracellular signaling through different pathways Signup and view all the answers

What is one of the primary functions of specialized ependymal cells in the choroid plexus?

Secrete cerebrospinal fluid (CSF) Signup and view all the answers

Which structure is primarily responsible for the adjustments in CSF composition?

Specialized ependymal cells Signup and view all the answers

What is the consequence of a cerebrovascular accident (CVA) on the brain?

Oxygen deprivation leading to neuron death Signup and view all the answers

Which component of the circulatory system primarily removes blood from the brain?

Dural venous sinuses Signup and view all the answers

What feature differentiates the blood-brain barrier (BBB) from general circulation?

Presence of astrocytes regulating permeability Signup and view all the answers

Where do specialized ependymal cells form the blood-CSF barrier?

Choroid plexus Signup and view all the answers

What is a key feature of the cranial meninges in relation to brain protection?

They hold the brain in position and provide cushioning Signup and view all the answers

What is primarily responsible for stabilizing the resting membrane potential at -70 mV?

Sodium-Potassium Exchange Pump Signup and view all the answers

Which type of ion channel primarily opens in response to changes in voltage across the membrane?

Voltage-gated ion channel Signup and view all the answers

During depolarization, what primarily causes the membrane potential to rise?

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

What happens during the repolarization phase of an action potential?

Potassium ions exit the cell Signup and view all the answers

What distinguishes graded potentials from action potentials?

Graded potentials do not spread far from the stimulation site Signup and view all the answers

Where are chemically gated ion channels predominantly found?

On the cell body and dendrites of neurons Signup and view all the answers

How many sodium ions are ejected for every two potassium ions brought into the cell by the Sodium-Potassium Exchange Pump?

3 Na+ for 2 K+ Signup and view all the answers

What initiates the local current during depolarization?

Sodium ions moving parallel to the plasma membrane Signup and view all the answers

What characterizes a voltage-gated ion channel in its closed state?

It is closed but capable of opening upon stimulation. Signup and view all the answers

Which of the following statements accurately describes the selective permeability of the plasma membrane?

It selectively allows certain ions to pass while restricting others. Signup and view all the answers

What describes the period when the membrane is unable to respond to any stimulation?

Absolute refractory period Signup and view all the answers

What is the primary function of the sodium-potassium exchange pump in neurons?

It restores concentrations post-action potential. Signup and view all the answers

During which type of propagation does the action potential travel slower?

Continuous propagation Signup and view all the answers

What is primarily involved in repolarization of the neuron membrane after an action potential?

Efflux of K+ Signup and view all the answers

What happens immediately after voltage-gated K+ channels begin to close?

Membrane is briefly hyperpolarized. Signup and view all the answers

What defines the relative refractory period?

Only a strong stimulus can trigger another action potential. Signup and view all the answers

Which segment of the neuron initiates action potential during continuous propagation?

Initial segment Signup and view all the answers

What occurs at nodes during saltatory conduction?

Action potential develops. Signup and view all the answers

What is the effect of the inflammatory response during action potential transmission?

Alters membrane potential stability. Signup and view all the answers

How many Na+ ions are exchanged for K+ ions by the sodium-potassium exchange pump?

3 Na+ for 2 K+ Signup and view all the answers

Study Notes

Nervous Tissue

Nervous system includes the brain, spinal cord, and receptors in sense organs.
Nervous tissue consists of neurons and neuroglia (glial cells).
Neurons are basic functional units for intercellular communication.
Neuroglia are supporting cells of the nervous system.

Anatomical Divisions of the Nervous System

Nervous system is anatomically divided into the Central Nervous System (CNS), the Peripheral Nervous System (PNS), and the Enteric Nervous System (ENS).
CNS consists of the brain and spinal cord, responsible for integrating, processing, and coordinating sensory data and motor commands.
Sensory data describes conditions inside or outside the body.
Motor commands control or adjust certain peripheral organs, for example muscles.
PNS is all nervous tissue outside the CNS/ENS, delivers sensory information to the CNS, and carries motor commands to peripheral tissues and systems.
PNS has afferent and efferent divisions.
CNS does not have functional divisions.

Neurons

Neurons are generally long-lived, highly metabolic, and excitable.
Their cell bodies contain a nucleus and nucleolus.
Perikaryon is the cytoplasm surrounding the nucleus.
Nissl bodies (RER and ribosomes) are crucial for protein synthesis in neurons.
Dendrites are slender extensions that receive signals.
The axon is a single long process and transmits action potentials.
Axolemma is the cytoplasm of the axon.
Axon hillock connects the axon to the cell body, it's the base of axon.
Axon collaterals are branches of the axon.
Axon terminals (telodendria) are the tips of the telodendria.

Classification of Neurons

Classification is based on the relationship between the dendrites, cell body, and axon.
Anaxonic neurons are small with similar-looking processes.
Bipolar neurons are small and rare, with one dendrite and one axon.
Unipolar neurons (pseudounipolar neurons) are mostly sensory neurons.
Multipolar neurons have one axon and many dendrites, and they are the most common type.

Functional Classification of Neurons

Sensory (afferent) neurons carry information from sensory receptors to the CNS.
Motor (efferent) neurons carry instructions from the CNS to effectors.
Interneurons connect sensory and motor neurons within the CNS.

CNS Neuroglia

Neuroglia are support cells and protect neurons.
Astrocytes maintain blood-brain barrier and support neurons.
Ependymal cells form epithelium of the central canal and ventricles.
Oligodendrocytes form myelin sheaths in CNS.
Microglia are phagocytic cells that clean up debris.

PNS Neuroglia

Satellite cells surround neuron cell bodies in ganglia and regulate interstitial fluid around neurons.
Schwann cells form myelin sheaths around axons.

Neural Responses to Injuries

Wallerian degeneration occurs in the PNS, when distal part of an axon degenerates following injury.
Nerve regeneration in CNS is limited due to astrocytes releasing chemicals that block regrowth.

Membrane Potential

All plasma membranes exhibit membrane potentials due to ion movements.
Resting membrane potential is the membrane potential of a resting cell (-70mV).
Graded potentials are temporary, localized changes in resting potential caused by stimulus.
Action potentials are electrical impulses, propagated along axon surfaces towards synapse.

Action Potentials

Action potentials start at threshold (-60mV to -55mV).
Action potentials are "all-or-none" events, either fired or not.
Depolarization, activation of Na+ channels, and rapid inward Na+ flux result in a positive potential.
Inactivation of Na+ channels and activation of K+ channels leads to repolarization and loss of K+ resulting in return to resting potential.
Refractory period is the time membrane cannot respond to additional stimuli.
Types of propagation include continuous and saltatory.

Propagation of Action Potentials

Action potential propagation occurs in a series of steps.
Continuous propagation happens in unmyelinated axons, with sequential activation of local currents to depolarize adjacent areas to threshold.
Saltatory propagation occurs in myelinated axons with current to jump from node to node, speeding up the transmission. This is faster and more energy efficient.

Axon Diameter and Propagation Speed

Larger diameter axons transmit signals faster.
Type A fibers (large diameter, myelinated) carry information rapidly.
Type B fibers (medium diameter, myelinated) convey information at medium speed.
Type C fibers (small diameter; unmyelinated) transmit information slowly.

Synapses

Synapses are specialized sites where neurons communicate with each other or other cells.
Presynaptic neuron releases neurotransmitters.
Postsynaptic neuron receives neurotransmitters, causing graded potentials.

Types of Synapses

Electrical synapses involve direct ion flow between cells.
Chemical synapses involve neurotransmitters.

Postsynaptic Potentials

Excitatory postsynaptic potential (EPSP) is a graded depolarization potential.
Inhibitory postsynaptic potential (IPSP) is a graded hyperpolarization potential.

Summation

Summation combines EPSPs and IPSPs to determine if a neuron reaches threshold for an action potential.
Temporal summation involves rapidly repeated stimuli at a single synapse.
Spatial summation involves simultaneous stimuli arriving at multiple synapses.

Brain and Cranial Nerves

Brain has several parts with specific functions (Cerebrum, Cerebellum, Diencephalon, Brainstem).
Cranial nerves (12 pairs) serve diverse sensory & motor functions.
Blood supply essential to brain tissues and proper functioning.
Blood Brain barrier (BBB) isolates the CNS from general circulation.

Functional Areas of the Cerebrum

Motor areas, sensory areas, and association areas carry out specific roles in the CNS (motor areas controlling voluntary movements, sensory areas processing sensory information, and association areas enabling higher mental functions).
Association areas, like Wernicke's area, contribute to language comprehension.

Memory and Emotion

Limbic system plays a crucial role in emotion, motivation, and memory.
The limbic system includes several interconnected structures.

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Description

Explore the fundamentals of nervous tissue and the anatomical divisions of the nervous system in this quiz. Understand the roles of neurons and neuroglia, and discover the differences between the Central, Peripheral, and Enteric Nervous Systems. Test your knowledge of how these systems function in processing sensory data and motor commands.