Neuroscience Overview Quiz

Fundamentals of the Nervous System

• The nervous system has three major functions: sensory, integration, and motor.
• Sensory monitors internal and external environments via receptors.
• Integration interprets sensory information and processes complex functions.
• Motor responds to processed information to stimulate effectors (muscle contraction/glandular secretion).

General Organization of the Nervous System

• Two anatomical divisions: central nervous system (CNS) and peripheral nervous system (PNS).
• CNS includes the brain in the cranial cavity and spinal cord in the spinal canal.
• PNS is all neural tissue outside the CNS.
• Two functional divisions: somatic and autonomic nervous systems.
• Somatic: provides sensory and motor innervation to all body parts except viscera, smooth muscle, and glands.
• Autonomic: sympathetic, parasympathetic, and enteric—provides involuntary motor innervation and sensory innervation to viscera (pain and autonomic reflexes).

Somatic vs. Visceral Pain

• Somatic pain involves nociceptors in skin, muscle, tendons, and bones. Often well localized and described as throbbing or aching.
• Visceral pain involves hollow organ and smooth muscle nociceptors. It is associated with poorly localized, vague, and diffuse pain, often referred to different locations. Associated with autonomic symptoms.

Histology of Neural Tissue

• Two types of neural cells: neurons and neuroglia.
• Neurons process, transfer, and store information. They consist of a cell body and processes of varying length.
• Neuroglia support, regulate, and protect neurons. They are non-conducting.

Neuroglia (Glial Cells)

• CNS neuroglia: astrocytes, oligodendrocytes, microglia, and ependymal cells.
• PNS neuroglia: Schwann cells (neurolemmocytes) and satellite cells in ganglia.

Astrocytes

• Supportive role, regulate extracellular pH and K+ concentration, induce blood-brain barrier formation.
• Involved in structural support, repair, and regulating the environment around neurons.
• Two types: fibrous astrocytes (prominent in white matter) and protoplasmic astrocytes (prominent in grey matter).
• Special types include Bergmann glial cells in cerebellum and Muller cells in retina.

Oligodendrocytes

• Create myelin sheaths around axons in CNS.
• Myelinated axons transmit impulses faster than unmyelinated axons.

Microglia

• Brain macrophages that phagocytize cellular wastes and pathogens.

Ependymal Cells

• Line ventricles of brain and central canal of spinal cord.
• Produce, monitor, and help circulate cerebrospinal fluid (CSF).

Schwann Cells

• Surround all axons in the PNS, creating a neurilemma crucial for damaged axon regeneration.
• Create myelin sheaths around most PNS axons.
• Satellite cells support groups of neuronal cell bodies within ganglia of PNS.

Myelin in the Peripheral and Central Nervous Systems

• Myelin in both PNS and CNS is formed by different glial cells. PNS uses Schwann cells whereas CNS uses oligodendrocytes to create myelin sheaths around axons.
• Myelin speeds up the transmission of action potentials, allowing impulses to travel faster down axons.

Neuron Structure

• Neurons: structural and functional unit of nervous system
• Sensory neurons convey impulses to CNS. Includes somatic afferent for surface pain, temperature, touch, and proprioception, and visceral afferent from mucosae, glands, blood vessels.
• Motor neurons convey impulses from CNS or ganglia to effector cells (somatic efferent : voluntary impulses to skeletal muscle, visceral efferent : involuntary impulses to cardiac muscle, smooth muscle, glands).
• Interneurons communicate and integrate sensory and motor neurons within CNS.

Neuron Classification

• Structural classification: anaxonic, bipolar, pseudounipolar, and multipolar neurons, based on the number of processes emanating from the neuron cell body.
• Functional classification: sensory (afferent), motor (efferent), and interneurons, based on information type and transmission direction.

Synapses

• Specialized junctions between neurons or between axons and target cells
• Most synapses in the nervous system are chemical synapses, involving neurotransmitter release.
• The presynaptic knob contains synaptic vesicles filled with neurotransmitters.
• The synaptic cleft is the space between the presynaptic and postsynaptic neurons.
• The postsynaptic membrane contains receptors for the neurotransmitter.

Neuronal Circuits

• Diverging: one neuron stimulates many other neurons. This is prevalent in motor pathways.
• Converging: many neurons stimulate a single neuron. This is seen in sensory and integrative pathways
• Reverberating: impulses from later cells repeatedly stimulate early cells, involved in short-term memory.
• Parallel-after-discharge: a single cell stimulates a group of cells that all stimulate a common postsynaptic cell (problem-solving, complex processing).

Anatomical Organization of Neurons

• Neurons group together into organized bundles, forming nerves (PNS) and tracts/pathways (CNS).
• Cell bodies are clustered into ganglia (PNS) or nuclei/centers (CNS); these are unmyelinated and part of "gray matter"
• Axons are bundled together in myelinated structures ("white matter").

Peripheral Nerves

• Bundles of nerve fibers held together by connective tissue (epineurium, perineurium, and endoneurium).
• Individual neurons are surrounded by the neurilemma (or sheath of Schwann).

The Autonomic Nervous System

• Regulates activity of smooth muscle, cardiac muscle, and certain glands.
• Two neuron system: preganglionic neurons (in CNS) and postganglionic neurons (outside CNS).
• Two major divisions: sympathetic and parasympathetic. Sympathetic = fight-or-flight; Parasympathetic = rest-and-digest.

Sympathetic and Dorsal Root Ganglia

• Clusters of neuronal cell bodies outside the CNS. Sensory ganglia carry impulses to CNS; autonomic ganglia contain cell bodies of post-synaptic neurons.

Spinal Cord

• The spinal cord runs through the vertebral column, from the foramen magnum to the second lumbar vertebra.
• It has regions divided into cervical, thoracic, lumbar, and sacral.
• The spinal cord has an outer white matter and an inner gray matter.
• The gray matter is H-shaped, containing cell bodies of neurons and nerve fibers.
• The white matter surrounds the gray matter, containing myelinated axons organized into columns to carry information up and down the column.
• The dorsal roots carry sensory neurons, and the ventral roots carry motor neurons.

Meninges

• Connective tissue membranes covering the spinal cord: dura mater, arachnoid mater, and pia mater.
• Spaces include subdural (serous fluid) and subarachnoid (CSF).
• The meninges provide cushioning, protection and anchor the spinal cord.

Control of Autonomic Nervous System

• The hypothalamus plays a key role in regulating autonomic functions.
• The hypothalamus integrates sensory input, including emotions, and visceral information from the body, triggering outputs to nuclei in the brainstem and spinal cord.
• Posterior and lateral portions primarily control sympathetic activity, while anterior and medial regions primarily control parasympathetic activity.

ANS Neurotransmitters

• Cholinergic neurons release acetylcholine (ACh).
• Adrenergic neurons release norepinephrine (NE).

Parasympathetic Cranial Nerves

• Oculomotor, Facial, Glossopharyngeal, and Vagus nerves convey parasympathetic signals.

Parasympathetic Sacral Nerve Fibers

• Form pelvic splanchnic nerves that innervate smooth muscles and glands in the distal digestive system, urinary, and reproductive organs.

Test your knowledge on the primary functions of the nervous system and the roles of neuroglial cells. This quiz covers various aspects like sensory information processing, neuron types, and the blood-brain barrier. Perfect for students studying neuroscience or related fields.