Nervous Tissue and Its Divisions

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Questions and Answers

What type of tissue serves as the basic functional unit of the nervous system?

Neurons (correct)

Connective Tissue

Epithelial Tissue

Neuroglia

Which division of the nervous system has no functional subdivisions?

Autonomic Nervous System

Enteric Nervous System

Central Nervous System (correct)

Peripheral Nervous System

The PNS is responsible for delivering sensory information to which structure?

Effectors

ENS

CNS (correct)

Neuroglia

Which subdivision of the PNS is primarily responsible for controlling voluntary skeletal muscle contractions?

Somatic Nervous System Signup and view all the answers

What term is used for the target organs that respond to motor commands?

Effectors Signup and view all the answers

Which part of the nervous system is responsible for processing sensory data?

Central Nervous System Signup and view all the answers

What is the primary role of the afferent division of the PNS?

To carry sensory information to the CNS Signup and view all the answers

Which of the following statements about neuroglia is true?

They provide support and protection to neurons. Signup and view all the answers

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

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

How does cerebrospinal fluid (CSF) circulate through the central nervous system?

From the choroid plexus through the ventricles to the subarachnoid space Signup and view all the answers

Which statement best describes the protective function of the cranial meninges?

They hold the brain in position and cushion it from sudden impacts Signup and view all the answers

What role do astrocytes play in the blood-brain barrier (BBB)?

They regulate the permeability of endothelial junctions through chemical release Signup and view all the answers

Which of the following substances can typically cross the blood-brain barrier (BBB)?

Lipid-soluble compounds such as O2 and alcohol Signup and view all the answers

What is the blood-CSF barrier primarily formed by?

Tight junctions between specialized ependymal cells surrounding capillaries Signup and view all the answers

Which cranial structure allows hypothalamic hormones to enter the general circulation?

Posterior lobe of the pituitary gland Signup and view all the answers

What is the primary function of the cerebrum?

Controls higher mental functions like conscious thought Signup and view all the answers

Which structure is primarily responsible for relaying sensory information in the diencephalon?

Thalamus Signup and view all the answers

What connects the pituitary gland to the hypothalamus?

Infundibulum Signup and view all the answers

Which region of the brain is the second largest and coordinates body movements?

Cerebellum Signup and view all the answers

What is NOT a major component of the brainstem?

Cerebellum Signup and view all the answers

Which of the following structures is involved in the production of hormones?

Hypothalamus Signup and view all the answers

Which part of the brainstem connects the cerebellum to the brainstem?

Pons Signup and view all the answers

What feature of the medulla oblongata regulates autonomic functions?

Inferior portion Signup and view all the answers

How many ventricles are present in the brain?

Four Signup and view all the answers

The surface layer of gray matter in the cerebellum is called what?

Cerebellar cortex Signup and view all the answers

Which type of neuron is primarily involved in monitoring the external environment?

Somatic sensory neurons Signup and view all the answers

Which of the following correctly describes unipolar neurons?

They have a fused axon and dendrite with the cell body on one side Signup and view all the answers

Which type of neuron is described as having one long axon and two or more dendrites?

Multipolar neurons Signup and view all the answers

In the context of functional classification, which type of neuron carries instructions from the CNS to peripheral effectors?

Motor neurons Signup and view all the answers

Interoceptors are defined as sensory receptors that monitor which of the following?

Internal systems such as digestion Signup and view all the answers

Which neurons are primarily responsible for higher functions, such as memory and learning?

Interneurons Signup and view all the answers

What characterizes bipolar neurons regarding their structure?

They consist of one dendrite and one axon Signup and view all the answers

Which type of sensory neuron is responsible for the processes that extend from sensory receptors to the CNS?

Afferent neurons Signup and view all the answers

What is the role of proprioceptors in the nervous system?

Monitor the position and movement of skeletal muscles and joints Signup and view all the answers

In the classification of neurons, which type does NOT have a clear differentiation in appearance of cell processes?

Anaxonic neurons Signup and view all the answers

What is the role of the Sodium-Potassium Exchange Pump in maintaining the resting membrane potential?

It stabilizes resting membrane potential by ejecting 3 Na+ for every 2 K+. Signup and view all the answers

How does the permeability of the plasma membrane to potassium ions affect the resting membrane potential?

The membrane's high permeability to K+ contributes to a resting potential close to K+ equilibrium potential. Signup and view all the answers

What triggers the opening of chemically gated ion channels?

Binding of specific chemicals to the channel. Signup and view all the answers

Which state of voltage-gated ion channels prevents ion movement after activation?

Closed and incapable of opening (inactivated). Signup and view all the answers

What is the primary effect of depolarization on the membrane potential?

It causes a rise in membrane potential due to sodium ion influx. Signup and view all the answers

Which ion channel type is primarily responsible for the rapid propagation of action potentials in neurons?

Voltage-gated ion channels. Signup and view all the answers

What characterizes graded potentials compared to action potentials?

Graded potentials vary in magnitude and decrease over distance. Signup and view all the answers

What primarily differentiates active ion channels from passive ion channels in terms of functionality?

Active ion channels open and close in response to stimuli. Signup and view all the answers

What mainly causes repolarization of the membrane potential after a stimulus is removed?

Closure of sodium channels and opening of potassium channels. Signup and view all the answers

What is a primary factor in the establishment of resting membrane potential?

Differences in ion concentrations between intracellular and extracellular compartments. Signup and view all the answers

Study Notes

Nervous Tissue

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

Anatomical and Functional Divisions

Anatomically, the nervous system has three divisions: central nervous system (CNS), peripheral nervous system (PNS), and enteric nervous system (ENS).
The CNS consists of the brain and spinal cord and is responsible for integration, processing, and coordinating sensory data and motor commands.
Sensory data conveys info about conditions inside and outside the body.
Motor commands control or adjust peripheral organs (like skeletal muscles).
The Peripheral Nervous system (PNS) includes all nervous tissue outside the CNS and ENS.
The PNS delivers sensory information to the CNS and carries instructions from the CNS to the body's periphery.
The PNS has two functional divisions: afferent and efferent.
The CNS does not have functional divisions like the PNS.

Neuron Structure

Neurons have a cell body, dendrites, an axon, and telodendria.
The cell body (soma) contains the nucleus and cytoplasm (perikaryon).
Dendrites receive signals and extend from the cell body.
The axon is a single elongated process that carries signals away from the cell body.
The axon hillock is the connection between the cell body and the axon.
Axon terminals (telodendria) transmit signals from the axon to other cells.
Nissl bodies are dense areas of rough endoplasmic reticulum that make the nervous tissue appear gray.

Neuron Classification

Neurons are classified structurally as anaxonic, bipolar, unipolar, and multipolar.
Based on the relationship between dendrites, cell body, and axon.

Functional Classification

Sensory (afferent) neurons carry signals from sensory receptors to the CNS.
Motor (efferent) neurons carry signals from the CNS to effectors (muscles, glands, or other organs).
Interneurons connect sensory and motor neurons, and are located in the CNS.

Neuroglia in the CNS

Astrocytes: support neurons and create the blood-brain barrier.
Ependymal cells: line cavities in the brain and spinal cord.
Oligodendrocytes: form myelin sheaths around axons in the CNS.
Microglia: phagocytes that remove debris and pathogens.

Neuroglia in the PNS

Satellite cells: surround neuron cell bodies in sensory ganglia, and regulate the environment of the neurons.
Schwann cells: form myelin sheaths around axons of peripheral nerves.

Myelin

Myelin is a fatty insulation that wraps around axons.
Myelinated axons transmit impulses faster than unmyelinated ones.

Membrane Potentials

The membrane potential is the difference in electrical charge across the cell membrane.
Graded potentials are small, local changes in membrane potential.
Action potentials are large, rapid changes in membrane potential that travel long distances.
Membrane permeability varies by ion.

Active Processes

Sodium-potassium exchange pump maintains the resting membrane potential.

Graded Potentials

Graded potentials are changes in membrane potential that are localized and vary in size. They can be excitatory or inhibitory.
Depolarization causes a decrease in the membrane potential (becomes less negative).
Repolarization brings the membrane potential back to its resting state.
Hyperpolarization causes an increase in the membrane potential (becomes more negative).

Synapses

Synapse: a junction between two neurons or a neuron and an effector.
Chemical synapses: use neurotransmitters to transmit signals across the synaptic cleft.
Electrical synapses: have direct connections between cells allowing rapid signal transmission.

Neurotransmitters and Neuromodulators

Neurotransmitters are chemical messengers released by neurons.
Neuromodulators alter the rate of neurotransmitter release or the response of the post-synaptic cell.

Post-Synaptic Potentials

EPSP: excitatory post-synaptic potentials tend to initiate post-synaptic action potentials.
IPSP: inhibitory post-synaptic potential tend to decrease the ability of a neuron to initiate post-synaptic action potentials.

Summation

Spatial summation: stimuli (EPSPs & IPSPs) arrive simultaneously at different synaptic sites on the post-synaptic neuron.
Temporal summation: two or more stimuli arrive at the same site on the post-synaptic neuron in rapid succession.

Additional notes on Specific Cranial Nerves.

(Page 29): List of cranial nerves and their primary functions.
(Page 29): Cranial reflexes are automatic responses involving cranial nerves; clinically useful for checking nerve/brain condition.
Information specific to specific cranial nerves.

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Description

Explore the fundamentals of nervous tissue, including its composition of neurons and neuroglia. Gain insights into the anatomical and functional divisions of the nervous system, such as the central, peripheral, and enteric nervous systems, and their roles in communication and coordination within the body.