foundations of the central nervous shstem

What structural structures surround and encase all components of the central nervous system?

Bones, specifically the skull encasing the brain and the spinal column encasing the spinal cord.

According to recent research mentioned in the lecture, at approximately what age does the human brain stop developing?

Around 30 years old, although the majority of development occurs by the mid-twenties.

On what day after conception does embryonic tissue develop into the ectoderm germ layer?

Around day 18.

What is the primary function of radial glia during brain development?

They grow radially outward from the ventricular zone to provide guidance to neurons migrating outward during brain development.

Around day 28, what event occurs at the anterior end of the neural tube, and what three major brain divisions are formed by the surrounding tissue?

The anterior end fully closes to form ventricles, and the surrounding tissue forms the prosencephalon (forebrain), mesencephalon (midbrain), and rhombencephalon (hindbrain).

What developmental failure is responsible for spina bifida?

Incomplete neural tube closure (or incomplete neural tube development).

By the seventh week of development, into which two sub-regions does the prosencephalon divide?

The telencephalon and the diencephalon.

By the seventh week of development, into which two sub-regions does the rhombencephalon divide?

The metencephalon and the myelencephalon.

Which major brain structures develop from the telencephalon?

The cerebral cortex, basal ganglia, and limbic system.

Which subcortical structures develop from the diencephalon?

The thalamus and the hypothalamus.

What brain structures develop from the metencephalon and myelencephalon, respectively?

The metencephalon develops into the cerebellum and pons, while the myelencephalon develops into the medulla oblongata.

How does cortical folding (gyrification) affect the surface area of the human cerebral cortex?

It triples the surface area compared to a smooth brain in the same space, providing approximately $2.5\,\text{sq ft}$ of cortical surface area.

What is the approximate thickness of the cerebral cortex gray matter, and why is it referred to as gray matter?

It is approximately $3\,\text{mm}$ thick and is called gray matter due to the presence of cell bodies, neurons, and glia.

Why are subcortical regions referred to as white matter?

They are primarily composed of axon tracts covered in lipid-based myelin sheaths, which appear white.

How do the primary cognitive roles of the left and right cerebral hemispheres differ in terms of functional lateralization?

The left hemisphere analyzes information (language, logical, and analytical thinking), while the right hemisphere synthesizes information (creativity, spatial awareness, intuitive thinking, and emotional processing).

What is the primary function of the corpus callosum?

It connects corresponding parts of the cerebral cortex of the left and right hemispheres, allowing them to work together.

What functions are mediated by the prefrontal cortex, and what historical case demonstrated these functions after an injury?

It is involved in planning complex cognitive behavior, decision making, and moderating social behavior, as demonstrated by Phineas Gage after an iron rod damaged his frontal lobe.

Describe the path of motor planning and execution across the prefrontal, premotor, and primary motor cortices.

Planning begins in the prefrontal cortex, signals are sent to the premotor cortex to organize cognitive decisions into a plan, and the primary motor cortex converts this plan into neural signals sent down the spinal cord.

Where is the primary somatosensory cortex located relative to the central sulcus?

It is located in the parietal lobe, directly posterior to the central sulcus and primary motor cortex.

In which lobes are the primary visual cortex and primary auditory cortex located?

The primary visual cortex is in the occipital lobe, and the primary auditory cortex is in the temporal lobe.

What are the functional differences between Wernicke's aphasia and Broca's aphasia?

Wernicke's aphasia involves damage near the primary auditory cortex resulting in fluent but meaningless speech and poor comprehension, whereas Broca's aphasia involves damage to the premotor cortex causing nonfluent speech or word-finding difficulty while internal thinking remains intact.

What are the primary functions of the hippocampus, amygdala, and mammillary bodies within the limbic system?

The hippocampus is involved in learning and memory, the amygdala in emotions, and the mammillary bodies (connected to the hippocampus via the fornix) in episodic memory.

Why is the term "basal ganglia" an anatomical misnomer, and what is its main function?

It is a misnomer because "ganglia" technically refers to cell body clusters in the peripheral nervous system, but these subcortical nuclei function to relay motor messages to the cerebral cortex to control movement.

What mnemonic represents the survival behaviors controlled by the hypothalamus?

The four F's: feeding, fighting, fleeing, and mating.

What structures compose the tectum of the midbrain, and what are their respective functions?

The superior colliculi, involved in the visual system, and the inferior colliculi, involved in the auditory system.

Which major structures are contained within the tegmentum of the midbrain?

The anterior end of the reticular formation, the periaqueductal gray, the red nucleus, and the substantia nigra.

What does the word "cerebellum" translate to, and what are its primary functions?

It means "little brain"; it integrates sensory and muscle movement information to coordinate and smooth motor output, while also contributing to language acquisition and cognition.

Why is severe damage to the medulla oblongata often fatal, and how does marijuana differ from opioids regarding this structure?

The medulla controls vital functions like cardiovascular regulation and respiration; opioids act on medullary receptors to stop breathing, whereas marijuana has very few receptors in the medulla, preventing fatal overdose in that manner.

On which sides of the spinal cord do sensory (afferent) and motor (efferent) axons enter and exit?

Sensory (afferent) axons enter on the dorsal (back) side, and motor (efferent) axons exit on the ventral (stomach) side.

How many total spinal segments exist in the human spinal cord, and how are they categorized?

There are 31 segments: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal nerve segment.

What is a dermatome?

The limited area of skin innervated by a single sensory spinal nerve.

What is the distinction between tetraplegia and paraplegia?

Tetraplegia (quadriplegia) refers to complete paralysis from the neck down affecting arms, hands, trunk, legs, and pelvic organs, whereas paraplegia refers to paralysis in all or part of the trunk, legs, and pelvic organs.

What are the major divisions of the nervous system?

The major divisions of the nervous system include the Central Nervous System (CNS) and the Peripheral Nervous System (PNS).

What is the Central Nervous System (CNS) composed of?

The Central Nervous System (CNS) is composed of the brain and the spinal cord, which are entirely encased in protective bone.

What is the function of the Peripheral Nervous System (PNS)?

The Peripheral Nervous System (PNS) is responsible for connecting the CNS to the rest of the body and includes somatic and autonomic nervous systems.

What does the Somatic Nervous System do?

The Somatic Nervous System is responsible for receiving sensory information and controlling voluntary skeletal muscle movements.

What does the Autonomic Nervous System control?

The Autonomic Nervous System controls involuntary physiological functions of the body's internal organs.

What is the Neuraxis?

The Neuraxis is defined as an imaginary line drawn through the center of the nervous system, extending from the bottom of the spinal cord to the front of the brain.

What does the term anterior (or rostral) refer to in anatomical positioning?

Anterior (or rostral) refers to a structure located near or towards the front or head of an organism.

What does the term posterior (or caudal) refer to in anatomical positioning?

Posterior (or caudal) refers to a structure located near or towards the back or tail of an organism.

What is meant by superior in anatomical directional terms?

Superior refers to a structure located towards the back or upper surface of the body.

Define inferior in terms of anatomical direction.

Inferior refers to a structure located towards the underside or belly of an organism.

What does lateral refer to in anatomical terms?

Lateral refers to structures positioned toward the outer sides of the body, moving away from the central neuraxis line.

What does medial refer to in anatomical terms?

Medial refers to structures positioned towards the midline, moving closer to the neuraxis line.

What is the significance of gyrification in the cerebral cortex?

Gyrification increases the total cortical surface area without expanding skull volume, supporting advanced cognitive capacities.

What are the three primary anatomical planes used in neuroimaging?

The three primary anatomical planes are the Coronal Plane, Sagittal Plane, and Horizontal Plane (Axial or Transverse Plane).

What is the function of the cerebrospinal fluid (CSF)?

CSF provides buoyancy to the brain, reducing its effective weight and protecting against physical impacts.

How does the spinal cord's orientation differ from that of the brain?

The spinal cord follows standard quadrupedal orientation with ventral pointing towards the belly, while the brain's orientation is modified due to a $90^\circ$ rotation, having dorsal pointing upwards.

How many neurons are estimated to be in the human brain?

There are approximately $86\text{ billion}$ neurons in the brain.

What are the two basic divisions of the nervous system?

The Central Nervous System (CNS) and the Peripheral Nervous System (PNS).

What structures make up the Central Nervous System (CNS)?

The brain and the spinal cord.

What is the Peripheral Nervous System (PNS)?

The part of the nervous system outside the brain and spinal cord, including the nerves attached to the brain and spinal cord.

What is a nerve?

Bundles of individual neurons contained within a protective membrane sheath that relay sensory information to the CNS from the body and relay motor information from the CNS to the rest of the body.

What is the function of a sensory neuron?

A neuron that detects changes in the external or internal environment and sends information about these changes to the central nervous system.

What is the function of a motor neuron?

A neuron located within the central nervous system that controls the contraction of a muscle or the secretion of a gland.

What is an interneuron?

A neuron located entirely within the Central Nervous System.

What are the main structural components of a neuron?

The cell body (soma), dendrites, axon, and terminal buttons.

What is the soma of a neuron?

The cell body of a neuron, which contains the nucleus.

What is a dendrite?

A branched, treelike structure attached to the soma of a neuron that receives information from the terminal buttons of other neurons.

What is a synapse?

A junction between the terminal buttons of an axon and the membrane of another neuron.

What is the function of an axon?

A long, thin cylindrical structure that conveys information from the soma of a neuron to its terminal buttons and carries action potentials.

What is an action potential?

A brief electrical and chemical event that starts at the end of the axon near the cell body and travels toward the terminal buttons.

What is axoplasmic transport?

An active process by which substances are propelled along microtubules that run the length of the axon.

How do anterograde and retrograde axoplasmic transport differ?

Anterograde transport moves substances in a direction along an axon from the cell body toward the terminal buttons, whereas retrograde transport moves substances from the terminal buttons toward the cell body.

What is the myelin sheath?

A sheath that surrounds axons and insulates them, preventing messages from spreading between adjacent axons.

What happens when an action potential reaches the terminal buttons?

The terminal buttons secretes neurotransmitters into the synapse.

What is a neurotransmitter?

A chemical released by a terminal button that has an excitatory or inhibitory effect on another neuron.

What structures compose the cytoskeleton of a cell?

It is formed of microtubules and other protein fibers linked to each other forming a cohesive mass made of $3$ kinds of protein strands that give the cell its shape.

What is a microtubule?

A long strand of bundles of protein filaments arranged around a hollow core that forms part of the cytoskeleton and is involved in axoplasmic transport.

What is cytoplasm?

The viscous, semiliquid substance contained in the interior of a cell.

What is a gene?

The functional unit of the chromosome, which directs the synthesis of one or more proteins.

What is the role of mitochondria in a cell?

They are organelles responsible for extracting energy from nutrients and producing adenosine triphosphate (ATP) to provide energy for cellular functions.

What is adenosine triphosphate (ATP)?

A molecule of prime importance to cellular energy metabolism whose breakdown liberates energy.

What are the three types of glial cells in the Central Nervous System?

Astrocytes, oligodendrocytes, and microglia.

What are the main functions of astrocytes?

They provide structural support, nutrients, and other substances to CNS neurons, regulate the chemical composition of extracellular fluid, and clear debris through phagocytosis.

What is phagocytosis?

The process by which cells engulf and digest other cells or debris caused by cellular degeneration.

What is the role of an oligodendrocyte?

A glial cell in the central nervous system that forms myelin sheaths around axons.

What is a Node of Ranvier?

A naked portion of a myelinated axon located between adjacent oligodendroglia and Schwann cells.

What functions do microglia perform?

They act as the smallest glial cells, functioning as phagocytes to protect the brain from invading microorganisms and participating in inflammatory reactions following brain trauma.

What is a Schwann cell?

A cell in the peripheral nervous system wrapped around a myelinated axon, providing one segment of its myelin sheath.

What is the function of the area postrema?

It is a region of the medulla where the blood-brain barrier is weak, allowing poisons to be detected to initiate vomiting.

What is the blood-brain barrier?

A semipermeable barrier between the blood and the brain produced by cells in the walls of the brain's capillaries.

What is membrane potential?

The electrical charge across a cell membrane, representing the difference in electrical potential inside and outside the cell.

What is the typical resting membrane potential of a neuron?

The resting potential inside the neuron is $-70\,mV$.

What is the difference between hyperpolarization and depolarization?

Hyperpolarization is an increase in membrane potential relative to resting potential (making inside more negative), whereas depolarization is a reduction of membrane potential toward zero (making inside more positive).

What is the threshold of excitation?

The value of the membrane potential (approximately $-55\,mV$) that must be reached to produce an action potential.

How are ions distributed between intracellular and extracellular fluid at rest?

Intracellular fluid contains predominantly organic ions ($A^-$) and potassium ions ($K^+$), while extracellular fluid contains mostly sodium ions ($Na^+$) and chloride ions ($Cl^-$).

What is the function of the sodium-potassium transporter?

It is a protein in the membrane that extrudes sodium ions ($Na^+$) from the cell while transporting potassium ions ($K^+$) into the cell, consuming up to $40\,mV$ of metabolic energy.

What is the all-or-none law?

The principle that once an action potential is triggered in an axon, it is propagated without decrement to the end of the fiber.

What is the rate law?

The principle that variations in the intensity of a stimulus or transmitted information are represented by variations in the rate at which an axon fires.

What is saltatory conduction?

The conduction of action potentials along myelinated axons, where the impulse appears to jump from one Node of Ranvier to the next.

What is an economic advantage of saltatory conduction?

Myelinated axons need much less energy to maintain sodium balance because sodium channels are concentrated primarily at the nodes.

What is decremental conduction?

A decrease in the size of an electrical message as it travels.

What two key structures are contained in the cytoplasm of a terminal button?

Mitochondria and synaptic vesicles.

What is a ligand?

A chemical that binds with the binding site of a receptor.

What is the difference between ionotropic and metabotropic receptors?

An ionotropic receptor contains a binding site that directly opens an ion channel when a neurotransmitter attaches, whereas a metabotropic receptor activates a G protein and an enzyme to produce a second messenger that opens an ion channel elsewhere.

What four major types of neurotransmitter-dependent ion channels exist in the postsynaptic membrane?

Sodium ($Na^+$), potassium ($K^+$), chloride ($Cl^-$), and calcium ($Ca^{2+}$).

What is the difference between an EPSP and an IPSP?

An EPSP (excitatory postsynaptic potential) is an excitatory depolarization of the postsynaptic membrane, while an IPSP (inhibitory postsynaptic potential) is an inhibitory hyperpolarization.

What two mechanisms terminate postsynaptic potentials?

Reuptake (reentry of a neurotransmitter back into the terminal button) and enzymatic deactivation (destruction of a neurotransmitter by an enzyme).

What is acetylcholinesterase (AChE)?

The enzyme that destroys acetylcholine after it is released from terminal buttons, terminating the postsynaptic potential.