CNS Structure and Function

Flashcards providing vocabulary terms and definitions related to the structure and function of the Central Nervous System (CNS), including topics such as meninges, cerebrospinal fluid, the blood-brain barrier, brain lobes, major brain structures, and their specific roles.

Analgesics

Drugs used to relieve pain.

Cranial Meninges

Connective tissue membranes that envelop the brain and spinal cord, consisting of the dura mater, arachnoid mater, and pia mater.

Dura mater

The outermost and toughest layer of the meninges, continuous with the epineurium of the spinal nerves.

Arachnoid mater

The thin and wispy middle layer of the meninges.

Pia mater

The innermost layer of the meninges, bound tightly to the surface of the brain and spinal cord.

Subdural space

A potential space located between the dura mater and the arachnoid mater, containing serous fluid.

Subarachnoid space

The space located between the pia mater and the arachnoid mater, filled with Cerebrospinal Fluid (CSF).

Cerebrospinal Fluid (CSF)

Fluid produced in the choroid plexus from blood, which absorbs shocks, serves as a medium for nutrient and waste exchange, and is reabsorbed into the blood in dural sinuses through arachnoid villi.

Choroid plexus

Specialized epithelial cells lining the ventricles of the brain, responsible for producing cerebrospinal fluid (CSF).

Blood-brain barrier (BBB)

A highly selective permeable barrier that separates the circulating blood from the brain, formed by capillary endothelial cells connected by tight junctions.

Tight junctions

Connections between capillary endothelial cells in the blood-brain barrier that restrict the diffusion of solutes between the cells.

Frontal lobe

A lobe of the brain involved in personality characteristics, decision-making, movement, recognition of smell, and speech (Broca's area).

Parietal lobe

A lobe of the brain involved in identifying objects, spatial awareness, pain and touch sensation, and understanding speech (Wernicke’s area).

Occipital lobe

A lobe of the brain primarily responsible for vision (ocular function).

Temporal lobe

A lobe of the brain involved in short-term memory, speech, musical rhythm, and smell recognition.

Cerebral Cortex

The outer layer of the cerebrum, responsible for sensory perception, voluntary control of movement, language, personality traits, and sophisticated mental events such as thinking and decision-making.

Primary somatosensory cortex

Located in the postcentral gyrus, where sensory input from the skin, musculoskeletal system, viscera, and taste buds is translated into perception.

Primary motor cortex

Located in the precentral gyrus, composed of pyramidal cells that allow conscious control of precise, skilled, voluntary movements.

Motor homunculus

A caricature representing the relative amounts of cortical tissue devoted to each specific motor function in the primary motor cortex.

Limbic System

A group of brain structures involved in motivation, learning, and memory, including the cingulated gyrus, hippocampus, and amygdala.

Hippocampus

A part of the limbic system crucial for sending memories to the cerebral hemispheres for long-term storage, involved in motivation and learning, and one of the first parts of the brain affected in Alzheimer’s Disease.

Amygdala

A part of the limbic system involved in emotional responses and linking emotions with memory.

Hypothalamus

A part of the diencephalon that links the brain and periphery, regulating many homeostatic functions (e.g., temperature, thirst, urine output, food intake), autonomic function, circadian cycles, and basic behavioral patterns (4 Fs: feeding, fighting, fleeing, and reproductive behavior).

Thalamus

A part of the diencephalon that serves as a relay station for all synaptic input, contributes to crude awareness of sensation, some degree of consciousness, and plays a role in motor control.

Midbrain

The smallest region of the brain, located between the hindbrain and forebrain, controlling visual and auditory systems, eye movement, and body movement (e.g., via the red nucleus and substantia nigra).

Substantia nigra

A darkly pigmented portion of the midbrain containing dopamine-producing neurons, whose degeneration is associated with Parkinson's disease.

Cerebellum

A component of the hindbrain responsible for the maintenance of balance, enhancement of muscle tone, coordination and planning of skilled voluntary muscle activity, and motor learning.

Pons

A component of the hindbrain that serves as an important link between the spinal cord and higher brain levels, relaying motor and sensory impulses, and involved in motor control, sensory analysis, respiration, and the sleep-wake cycle.

Medulla oblongata

A component of the hindbrain containing cardiovascular and respiratory rhythmicity centers, which regulate the rate and force of heartbeat, vasoconstriction/dilation, basic breathing rhythm, and protective reflexes like sneezing and coughing.

Reticular Activating System (RAS)

A network in the brain stem that determines the level of alertness, arousal, sleep, pain perception, and muscle tone by controlling the overall degree of cortical alertness or level of consciousness.

Spinal cord

A major component of the central nervous system that integrates all synaptic input from the body and is responsible for spinal reflexes and relaying signals to and from the brain.

Basal nuclei

Subcortical nuclei involved in the inhibition of muscle tone, coordination of slow, sustained movements, and suppression of useless patterns of movements.

"Why do brain cells need strong protection mechanisms?"

"Because they must live for a very long time and have very limited ability to repair or regenerate."

"How does skin damage differ from brain damage in terms of healing?"

"Skin can heal by forming scars and regenerating new cells while brain cells have very limited repair capacity."

"What is the blood-brain barrier (BBB)?"

"A protective mechanism that prevents many chemicals microorganisms and toxins from entering the brain."

"Give examples of substances that can cross the BBB easily."

"Alcohol nicotine morphine paracetamol and certain animal toxins."

"Why is crossing the BBB important in pharmacology?"

"Because large pharmaceutical molecules often cannot cross so strategies are studied to transport or reassemble drugs across the BBB."

"What protects the brain physically within the skull?"

"Cerebrospinal fluid (CSF) and three meningeal layers."

"What are the three meningeal layers?"

"Dura mater arachnoid mater pia mater."

"Describe the dura mater."

"The outermost meningeal layer thick and tough (leather-like) protecting the brain and spinal cord."

"What flows between the meningeal layers?"

"Cerebrospinal fluid (CSF)."

"What is a risk of the brain being encased in membranes?"

"If bleeding occurs (e.g. subdural hematoma) blood cannot escape causing dangerous pressure on the brain."

"What are the three meningeal layers?"

"Dura mater arachnoid mater pia mater."

"What is the dura mater?"

"The tough outermost meningeal layer beneath the skull and skin; thick and protective."

"What lies beneath the dura mater?"

"The subdural space then the arachnoid mater."

"What does 'arachnoid' mean?"

"It comes from Latin for 'spider web' due to its thin web-like appearance."

"How does the arachnoid mater appear in life vs. after death?"

"In life it looks inflated and white-striated; after death it collapses resembling a spider web."

"What is the pia mater?"

"The innermost thin meningeal layer tightly attached to the brain tissue."

"Do meninges cover just the brain?"

"No, they also cover the spinal cord and extend around spinal nerves."

"What is the epidural space?"

"The space outside the dura mater where epidural injections are given."

"What is a subdural hematoma?"

"A bleed between the dura mater and the arachnoid mater."

"What is a subarachnoid hemorrhage?"

"A bleed between the arachnoid mater and the pia mater."

"What happens if bleeding occurs within the brain tissue itself?"

"It is called a stroke (intracerebral hemorrhage)."

"What are the ventricles of the brain?"

"Fluid-filled cavities inside the brain that include the lateral ventricles third ventricle and fourth ventricle."

"How are the lateral ventricles shaped?"

"They curve like ram’s horns pointing forwards backwards and slightly outward."

"What do the ventricles contain?"

"They are filled with cerebrospinal fluid (CSF)."

"Where is CSF produced?"

"Inside the lateral ventricles by the choroid plexus."

"What is the choroid plexus?"

"A plant-like structure lining the ventricles that produces CSF and increases surface area for secretion."

"How much CSF is in the brain at a time?"

"About 150 mL roughly half a glass of water."

"How often is CSF replaced?"

"Around three times a day."

"What are the main functions of CSF?"

"Provides some nutrients removes waste products cushions the brain and spinal cord."

"Does CSF provide oxygen to the brain?"

"No oxygen is supplied by the blood; CSF mainly handles nutrients and waste removal."

"What type of solution is CSF?"

"A salty solution containing dissolved salts."

"What helps CSF circulate through the ventricles?"

"Hair-like cells (cilia) that slowly move CSF through the system."

"What are ependymal cells?"

"Cells that line the ventricles of the brain and help produce circulate and regulate cerebrospinal fluid (CSF)."

"What structure do ependymal cells form inside the ventricles?"

"The choroid plexus a plant-like structure that produces CSF."

"What are the three main functions of ependymal cells?"

"Produce CSF circulate CSF and help regulate its composition."

"Why does the brain require so much energy?"

"Neurons constantly maintain electrical potentials and homeostasis even when not firing signals."

"What percentage of the body’s energy does the brain use?"

"About 30% of oxygen and glucose despite being only 1.5–2 kg in weight."

"What happens to neurons if deprived of oxygen?"

"They begin to die within minutes causing irreversible damage."

"Why can people survive longer without oxygen when very cold?"

"Cooling slows metabolism reducing oxygen demand (e.g. avalanche survival cases)."

"What are the four main arteries supplying the brain?"

"Two carotid arteries (front) and two vertebral arteries (back)."

"What is the Circle of Willis?"

"A circular arterial network at the base of the brain where the carotid and vertebral arteries connect providing collateral circulation."

"What is the safety role of the Circle of Willis?"

"If one major vessel is obstructed blood can be redistributed from others to maintain brain supply."

"What happens if a blockage occurs beyond the Circle of Willis?"

"That brain region is deprived of oxygen leading to neuron death (stroke)."

"What separates neurons from direct contact with blood?"

"The blood-brain barrier (BBB) formed mainly by astrocytes and tight junctions."

"What are astrocytes?"

"Star-shaped glial cells that support neurons transfer nutrients/waste and form part of the BBB."

"How do astrocytes help form the BBB?"

"Their 'end feet' surround blood vessels and create tight junctions preventing most substances from passing through."

"What molecules can cross the BBB easily?"

"Lipid-soluble molecules (e.g. alcohol nicotine antidepressants)."

"Why can lipid-soluble molecules cross the BBB?"

"They dissolve in fats and diffuse through cell membranes of astrocytes."

"Can water-soluble molecules diffuse through the BBB?"

"No tight junctions block them unless specific transporters exist."

"What natural substances cross via transporters?"

"Glucose and other essential molecules."

"What are current pharmacological strategies to cross the BBB?"

"Make drugs smaller make them lipid-soluble or repackage them for transporter recognition."

"What is the 'Trojan horse' strategy for BBB penetration?"

"Encapsulating a drug in a carrier that the brain recognizes and allows through transporters."

"Why is BBB drug delivery research difficult?"

"Success depends on molecular size 3D structure and binding potential; results vary widely."

"Can viruses usually cross the BBB?"

"No the BBB is highly effective at blocking them."

"What is a major limitation of the BBB for medicine?"

"Many effective drugs work when directly infused into the brain but cannot cross the BBB naturally."

"What are the main lobes of the brain?"

"Frontal parietal occipital temporal."

"What are the main functions of the frontal lobe?"

"Personality decision making voluntary movement."

"What are the main functions of the parietal lobe?"

"Processing touch temperature and identifying objects."

"What is the main function of the occipital lobe?"

"Vision."

"What are the main functions of the temporal lobe?"

"Short-term memory speech auditory processing rhythm smell recognition."

"What structures make up the hindbrain?"

"Cerebellum pons medulla reticular formation."

"What is the role of the cerebellum?"

"Coordination and motor control (not essential for life but important for skilled movement)."

"What is the role of the medulla and pons?"

"Essential life functions such as breathing and heart rate."

"What is the tectum ('roof') of the brainstem formed by?"

"The superior and inferior colliculi."

"What is the function of the superior and inferior colliculi?"

"Subcortical processing of vision and auditory information and integration of the two."

"What is the substantia nigra?"

"A dark midbrain region containing dopaminergic neurons that degenerate in Parkinson’s disease."

"What is the forebrain composed of?"

"Cerebral cortex corpus callosum limbic system hippocampus diencephalon (thalamus, hypothalamus, pituitary).