Principles of Neuroscience Flashcards
What are some identifiable functions performed by the nervous system?
The nervous system performs various functions, including controlling movement, regulating physiological functions through homeostasis and producing consciousness
During which historical periods did views about the brain’s role in thought or experience evolve?
Views about the brain’s role in through or experience evolved from Ancient Egyptians through Aristotle up to the enlightenment. early views did not attribute though to the brain and functions were initially ascribed to the heart
How does the nervous system contribute to the construction of our internal universe and perception of the external world
the nervous system constructs our internal universe by generating conscious experiences. it interprets stimuli from the external world, creating our perceptions and shaping our awareness of ourselves and the environment
What does the quote “Cogito, ergo sum” signify, and how does it relate to the understanding of the mind?
the means “I think, therefore I am” it signifies the certainty of one’s own existence through thought, emphasising that the nature of through is a private experience produced by the operation of the nervous system
How did early views regarding the seat of intellect differ and what observations led to a shift in understanding?
early views, such as Aristotle’s cardio-centric view, attributed the seat of intellect to the heart. However, observations from studying injured brains, particularly during the Renaissance, led to the recognition of the brain’s role in cognitive functions.
What is the nervous system’s composition in vertebrates and what are the components of the CNS and the PNS?
the nervous system in vertebrates comprises a central division (CNS) and a peripheral division (PNS). the CNS includes the brain and spinal cord, the PNS includes everything else that connects to and from the CNS
What are the aims of the subject in understanding neuroscience?
the aims include appreciated the scope and context of neuroscience, understanding how the nervous system can be studied, recognising the specialisation the nervous system cells, and understanding the structural and functional organisation the human nervous system
What is the significance of Neurology as a medical discipline in understanding brain function?
Neurology, as a medical discipline, allowed the structured analysis of the brain disease and injury, providing insights into how these conditions manifest as signs and symptoms
What was the major insight made during antiquity regarding the brain and the mind?
the major insight was that the brain’s operation furnishes the mind. However, this view was not widely adopted until the scientific study of mind and brain began
Who appreciated the role of the brain in experience and behaviour during Ancient Greece and Ancient Rome?
Hippocrates in Ancient Greece and Galen in Ancient Rome appreciated the role of the brain in experience and behaviour. however, they saw its function in terms of the body’s humors.
what happens when the message is received i.e. the post-synaptic response
when the message is received at the synapse, the post-synaptic response involves the activation of receptors on the post-synaptic neuron’s membrane. thus activation may lead to the generation of a new action potential, continuing the transmission of the signal along the neural pathway
what is the nature of the transmission between one neuron and another?
the transmission between one neuron and another is chemical and occurs at synapses. neurotransmitters are released from the axon terminal of one neuron and bind to the receptors on the dendrites or cell bod of the enxt neuron
is conduction uni- or bi-directional in the nervous system?
conduction in the nervous system can be both uni-directional and bi-directional, depending on the specific neural pathway and the type of signals being transmitted
how are signals transmitted along neural pathways and within neural structures?
signals are transmitted along neural pathways through electrical impulses known as action potentials. within neural structures, signals are transmitted through the movement of ions across the cell membrane
what is the composition of the nervous system?
the nervous system is comprised of neurons and glial cells
How did the ability to visualise neurons with microscopes contribute to our understanding of the nervous system
- released a diverse range of neural types in various nervous system regions, contributing to our understanding of how the nervous system functions
- microscope, especially with silver stains, allowed for the detection of neurones
Describe the primary methods for studying functional organisation in the nervous system.
functional organisation in the nervous system was first explored experimentally revealing segregation based on identifiable functions, such as sensory and motor regions in the spinal cord
What is the significance of chemical neurotransmission in the majority of synapses, and how does it differ from electrical synapses?
Chemical neurotransmission is the predominant method of synaptic connections in the nervous system. Neurotransmitters released from the pre-synaptic terminal diffuse across the synaptic cleft, interacting with post-synaptic membrane receptors, initiating various events. This is in contrast to electrical synapses, which are faster but less variable.
Explain the molecular machinery involved in chemical synapses, focusing on neurotransmitter synthesis, release, and post-synaptic effects.
Chemical synapses involve molecular machinery for neurotransmitter synthesis, packaging, release, re-uptake, and breakdown. The post-synaptic terminal contains protein arrays and mechanisms associated with neurotransmitter receptors, influencing post-synaptic cell effects.
What is neural plasticity, and why is it considered fundamental to the functioning of the nervous system?
Neural plasticity refers to the capacity of the nervous system to change in response to activity. This adaptability is crucial to the way our nervous system works and includes various forms of synaptic plasticity, allowing for adjustments in the efficacy of synapses.
What role do NMDA channels play in synaptic transmission, and how is calcium involved in this process?
NMDA channels are ligand-activated sodium channels. When glutamate binds and the post-synaptic terminal is depolarized, magnesium is dislocated, allowing Calcium ions to enter. Calcium serves as a potent cellular messenger with various actions, including increased synthesis and trafficking of AMPA receptors.
Describe the concept of long-term potentiation (LTP) and its importance, especially in the hippocampus.
Long-term potentiation (LTP) is the process where the responses of a neuron to a synaptic input depend strongly on the intensity of prior synaptic activity. The hippocampus, crucial for memory and learning, exhibits well-studied examples of LTP.`
Explain the mechanisms behind homologous and heterologous potentiation in synaptic plasticity.
Homologous potentiation occurs when only the previously active synapse is potentiated, while heterologous potentiation involves the potentiation of nearby synapses, even if they weren’t the ones intensely activated before.
How does the activation of NMDA receptors contribute to the increased synthesis and trafficking of AMPA receptors in the post-synaptic membrane during LTP?
NMDA receptor activation during LTP leads to increased synthesis and trafficking of AMPA receptors to the post-synaptic membrane. This enhances the opportunities for glutamate in the synaptic cleft to create a depolarizing sodium current in the synaptic terminal.
What questions did the discovery of growth cones and dynamic neuronal morphology raise regarding brain development and the stability of the mature brain?
Cajal’s discoveries, including superior staining revealing growth cones, prompted questions about how the brain forms connections and how fixed the mature brain is. This highlighted the dynamic and adaptable nature of neuronal connections.
How did Cajal’s recognition of superior staining contribute to the understanding of neuronal morphology, specifically in developing tissue?
Cajal’s recognition of superior staining in developing tissue led to the discovery of growth cones and dynamic neuronal morphology. It raised questions about brain connection formation and the stability of the mature brain.
What is the role of protein synthesis in maintaining long-term potentiation, and is it the sole mechanism for increasing synapse activity?
Protein synthesis is involved in maintaining long-term potentiation, but it is not the sole mechanism. Synapse activity can increase through various pathways, contributing to the complexity of information flow in the nervous system
What is cytoarchitecture, and how is it utilized in classifying parts of the brain?
Cytoarchitecture involves classifying brain parts based on microscopic appearance. The nervous system has six major divisions, including the cerebrum, diencephalon, cerebellum, brainstem, and spinal cord. Neuron doctrine revolutionized our understanding of discrete neuronal cells.
Describe the major divisions of the central nervous system (CNS) and their functions.
The major divisions of the CNS include the cerebrum, diencephalon (thalamus and hypothalamus), cerebellum, brainstem (medulla, pons, midbrain), and spinal cord. Neurons in the dorsal roots are sensory, while ventral roots are motor neurons.
Discuss the neuron doctrine and how it revolutionized our understanding of the nervous system.
The neuron doctrine, established by Wilhelm von Waldeyer in 1891, proposed that nerve cells are the anatomical and functional unit of the nervous system. It introduced the terms neuron, dendrite, and axon. Microscopy supported this doctrine, leaving questions about neuronal connectivity.
What did Charles Sherrington contribute to the acceptance of the neuron doctrine, and what observations supported his views on synapses?
Charles Sherrington supported the neuron doctrine, proposing the term “synapse” for the functional junction between neurons. His observations on degeneration patterns, slow reflex responses, and unidirectional conduction supported the existence of synaptic connections.
How does the wiring of the nervous system through synapses allow for information transmission, and what is the significance of plasticity in neuronal connectivity
Neuronal wiring through synapses allows for information transmission and is dynamic (plastic). Changes in synaptic efficacy involve molecular signaling pathways affecting intracellular processes, influencing short-term protein function to long-term gene expression changes.
Explain the process of long-term potentiation (LTP) in the context of Schaffer-collateral-CA1 synapses.
Long-term potentiation (LTP) at Schaffer-collateral-CA1 synapses involves burst activity (tetanus), resulting in increased future responses, sometimes lasting weeks or longer. It enhances the strength of synapses, affecting nearby synapses as well.
How does a burst of activity, such as tetanus, affect the strength of synapses in long-term potentiation?
Tetanus, a burst of activity with 100 impulses in a few seconds, leads to a much bigger effect on future responses in long-term potentiation (LTP). Even an hour after tetanus, a single stimulus can evoke a response twice as big as normal
Describe the roles of glutamate, AMPA receptors, and NMDA receptors in the molecular mechanisms underlying long-term potentiation.
Glutamate is the main excitatory neurotransmitter. AMPA receptors are selective Na+ channels, and NMDA receptors are ligand- and voltage-gated, allowing Ca2+ entry upon depolarisation. Mitochondria help maintain Ca2+ homeostasis near synapses
What is the key cell of the nervous system?
the neuron
Name the four types of macroglial cells that support neurons.
astrocytes, oligodendrocytes, Schwann cells (PNS), ependymal cells, satellite cells (PNS)
What is the role of microglia in the nervous system?
microglia are resident immune cells that maintain the health of the brain and CNS by acting as a defense mechanism agaisnt diseases and injuries
Why is it called the quadripartite synapse, and what are its four components?
because of its four components: pre and post-synaptic neurons, microglia, macroglia (astrocytes)
List three passive functions of macroglial cells.
Uptake and recycling of neurotransmitters, siphoning of potassium during depolarization, and maintenance of the blood-brain barrier.
What is the active function of macroglial cells in controlling neural function?
modulate neural function
How do glial cells contribute to maintaining ion balance by siphoning potassium?
Glial cells express inwardly rectifying potassium channels, which help remove potassium from the extracellular environment during depolarization.
Which neurotransmitters are recycled by glial cells, and what transporters do they express for this purpose?
GABA and glutamate and they express GABA and glutamate transporters for this purpose
What initiates calcium waves in glial cells, and what role do these waves play in communication between neurons?
Calcium waves are initiated by neurotransmitters like ATP and glutamate, trauma, spontaneous events, and inflammatory mediators. Neurons can communicate through axons.
What molecules are released by glial cells as neuromodulators, and what are they collectively known as?
Glial cells release ATP and glutamate, collectively known as gliotransmitters.
How do astrocytes, a type of macroglial cell, contribute to vascular regulation in the CNS?
Astrocytes connect neurons and blood vessels, allowing them to communicate messages to dilate or constrict vessels as needed through intracellular calcium signals.
How does intracellular calcium in glial cells influence neuronal activity?
An increase in intracellular calcium in glial cells can lead to the release of ATP, resulting in neuronal hyperpolarization and protection.
Describe the role of microglia in the nervous system, highlighting their dynamic nature and functions.
Microglia are immune cells that shape synapses, modulate neural function, and play a role in refining neural circuits. They are dynamic, constantly surveying the environment, and respond rapidly to inflammation or injury.
What are the passive and active functions of macroglial cells, and how do they contribute to the nervous system?
Passive functions include neurotransmitter deactivation, potassium siphoning, and maintaining the blood-brain barrier. Active functions involve releasing gliotransmitters and modulating the vasculature.
How do microglia regulate the vascular system, and what induces constriction at microglial contacts?
Microglia regulate the vascular system by touching blood vessels. Fractalkine induces constriction at microglial contacts.
How do microglia contribute to refining neural circuits during development?
Microglia prune or “eat” synapses that are not being used, unwanted, or weak, allowing only strong synapses to develop into adulthood.
Why are microglia considered local defence cells, and what is their response to inflammation or injury?
Microglia are local defense cells that rapidly change in response to inflammation or injury, resembling phagocytic macrophages.
What are the consequences of the loss of glial functions in diseases?
Loss of neurotransmitter uptake can cause excessive stimulation of neurons, while loss of potassium uptake can lead to changes in water balance and oedema.
What happens during the “inside-out” formation of cortical layers?
neurons are generated at remote locations and migrate into place, with the deepest layers forming first and those closer to the surface assembling last
How is the order of cortical layer formation described?
cortical layer formation follows an “inside-out” sequence, where the earliest neurons form the pre-plate, which later splits into the marginal zone (MZ) and the sub-plate (SP), with cortical plate (CP) neurons assembling into layer II-IV in sequence
Why study the development of the nervous system?
understanding the development of the nervous system is crucial because the brain is the most complex structure in the universe and it undergoes processes that adapt its function to changing environments, learns as it foes and can potentially be repaired or slowed in neurodegenerative disease by harnessing developmental mechanisms
What are the integrated steps involved in the construction of the nervous system?
the construction of the nervous system involves a continuum of steps
- neural induction
- neurulation
- morphogenesis and patterning of neural tube
- neurogenesis
- neuronal migration
- axon growth and path findings
- synaptogenesis
- gliogenesis/myelination
What is neural induction?
neural unduction is the process of assigning neural potential to a region of early embryo, where a region of the dorsal embryonic ectoderm acquires the potential to form the nervous system
What is the significance of failures in neural tube closure?
failures in neural tube closure can lead to neural tube defects such as spina bifida and anencephaly, as apoptosis occurs if any of the steps from neurogenesis to gliogenesis/myelination fail
How many neurons and synaptic connections are there in the human brain?
the human brain has approximately 10^11 neurons and 10^14 synaptic connections
According to Santiago Ramon y Cajal, why is it easier to study the developing brain?
because it is more accessible than the impenetrable full-grown forest of a mature brain
What are the primary brain vesicles formed after neural tube closure?
prosencephalon (forebrain)
mesencephalon (midbrain)
rhombencephalon (hindbrain)
What is the role of radial glia in neuroepithelial development?
radial glia, derived from neuroepithelial cells, serve as multipotent neural progenitor cells, producing neurons and glia through both symmetric and asymmetric cell divisions
What is the significance of the term ‘sex differences’?
‘Sex differences’ refer to the distinctions between males and females, encompassing various aspects such as genetics, anatomy, physiology, and behavior.
Define chromosomal sex/genetic sex.
Chromosomal sex/genetic sex is determined by the combination of sex chromosomes inherited from parents, typically denoted as XX for females and XY for males.
What are sex chromosomes, and what role do they play in sex determination
Sex chromosomes carry genes responsible for sex determination. In humans, females typically have two X chromosomes (XX), and males have one X and one Y chromosome (XY).
Where are the genes responsible for sex determination located?
The genes responsible for sex determination are located on the sex chromosomes.
During gonad development, what hormones play a crucial role, and what is their impact?
Gonad development involves the synthesis of sex hormones. In males, the testes produce testosterone, while in females, the ovaries produce estrogens and progesterone.
What is the SRY gene, and what is its role in sexual development?
The SRY gene is the testis-determining factor, a transcription factor that determines the development of male gonadal tissues. It alters the production of specific proteins, influencing sexual differentiation.
How are the primary types of circulating sex hormones determined?
The sex chromosomes determine the primary types of circulating sex hormones, with males producing testosterone and females producing estrogens and progesterone.
What is the primary source of sex steroids, and what is the common precursor for their biosynthesis?
Aromatase expression is critical because it determines whether testosterone (androgen) or estrogen is the primary active factor. Aromatase converts testosterone to estrogen, influencing the type of sex hormone produced.
Describe the temporal changes in testosterone synthesis in males during early development and puberty.
In males, there is a transient synthesis of testosterone pre-birth, leading to masculinization. Testosterone levels increase at puberty, reaching relatively constant adult levels.
Does everything depend on sex steroids, or are there other genetic mechanisms for determining sex?
While sex steroids play a crucial role, not everything depends on them. Genetic mechanisms, as seen in gynandromorphs with mixed male and female tissues, indicate additional factors influencing sex determination.
How does estrogen synthesis vary in females during different life stages?
Circulating estrogen (and progesterone) levels in females are low until puberty. During adulthood, cyclical patterns of estrogen and progesterone synthesis occur, decreasing in menopause.
How is sex steroid synthesis by the gonads regulated, and what determines the levels and pattern of FSH/LH secretion?
Gonadal steroid synthesis is regulated by pituitary hormones (FSH, LH), whose levels and patterns are determined by the hypothalamus. Hypothalamus activity is influenced by circulating hormone levels and other brain inputs through feedback mechanisms.
Differentiate between the sex hormones synthesised by male and female gonads.
Male gonads (testes) synthesize testosterone, while female gonads (ovaries) synthesize estrogens and progesterone.
Does everything depend on sex steroids, or are there other genetic mechanisms for determining sex?
While sex steroids play a crucial role, not everything depends on them. Genetic mechanisms, as seen in gynandromorphs with mixed male and female tissues, indicate additional factors influencing sex determination.
What evidence suggests hormone-independent genetic effects on brain regions?
Hormone-independent genetic effects are evident in mammals, where over 50 genes express different levels in male vs female brains before gonad formation, indicating independent effects of genetics on brain organization.
What is meant by the term “organisational effects” concerning the early effects of steroids on the nervous system?
Organizational effects refer to permanent changes in anatomical, physiological, and behavioral aspects induced by steroids during early development, contributing to sexual dimorphism.
Describe the genomic pathway of steroid action on the nervous system.
Steroids, such as androgens or estrogens, bind to specific cytoplasmic receptors (AR or ER) and form complexes that translocate to the nucleus. This activation leads to specific RNA and protein synthesis, resulting in slow and long-lasting effects.
Provide examples of behaviours that exhibit sexual dimorphism and are influenced by anatomical and physiological differences.
Sexual dimorphic behaviors include courtship and mating, parenting, aggressive/defensive behaviors, and the release of pheromones. These behaviors are defined by anatomical and physiological differences shaped by sex steroids.
Are steroid receptor expression patterns uniform throughout the nervous system?
No, steroid receptor expression patterns are not uniform. They occur in specific locations within the nervous system, influencing the effectiveness of steroids in those regions.
Besides steroids, what are the contributors to sexual dimorphism in neuronal connections and activity?
Other contributors to sexual dimorphism include sex differences in the expression of steroid hormone receptors and aromatase. These factors lead to variations in neuronal connections, activity, and neuron number.
What is the critical role of aromatase in masculinising the brain?
Aromatase, expressed during a critical developmental period, converts testosterone to estrogen in specific neurons. In males, this process is essential for masculinizing the brain, leading to permanent differences.
Are the effects of steroids on the maturing/mature nervous system reversible?
Throughout adulthood, the effects of androgens and estrogens on the nervous system are generally reversible. However, sustained hormone levels can
What is the fundamental limitation in imaging techniques such as microscopes, telescopes, or eyes, and how does it affect spatial resolution?
the fundamental limitation is imposed by the wavelength of the light. in microscopes, the spatial resolution is ultimately governed by the wavelength of visible light, restricting the maximum achievable resolution to about 250 nm
How do microscopy techniques like STED and STORM overcome the diffraction limit, and what is their mechanism?
STED narrows the point spread function by precisely deactivating the outer portion of the diffraction disc using a laser. STORM relies on the random switching of fluorescence in individual molecules, allowing their contributions to be imaged, localised and then switched off for further cycles.
What is the significance of micro-electrodes and patch-clamp electrodes in understanding neuronal activity, and how do they contribute to high-resolution electrophysiology?
Micro-electrodes record single neuron activity with excellent spatial and temporal resolution. Combining molecular biology with techniques like patch-clamp electrodes helps explicitly define the molecular basis of neuronal electrical activity.
How do brain imaging techniques differ in terms of spatial and temporal resolution, and what are some examples of whole-brain imaging technologies?
Techniques like CT scans and MRIs provide structural information but may lack spatial resolution compared to microscopes. Functional imaging techniques such as fMRI, PET, and MEG vary in spatial and temporal resolution. Whole-brain imaging technologies include CT scans, MRI, fMRI, PET, and MEG, utilising different electromagnetic radiation.
Explain how a CT or CAT scan works, highlighting its principle and potential harm.
CT scans use X-rays that pass through the brain, and attenuation readings from various angles create an image. Dense tissues attenuate X-rays more. Though X-rays can be damaging, CT scans use relatively small doses, equivalent to 8 months of normal background radiation.
What does MEG measure, and why is it often combined with MRI or CT maps?
MEG measures tiny magnetic fields generated by the brain’s neural activity. As it provides no structural information, MEG data are often combined with MRI or CT maps to enhance the overall understanding.
What is the principle behind fMRI, and how does it determine neurobiological correlates of behaviour?
fMRI detects changes in blood oxygenation levels associated with increased brain activity during specific tasks. The difference in the MRI signal reflects the oxygenation status of blood, known as the “blood oxygenation level-dependent” (BOLD) imaging technique.
What is the trade-off between temporal and spatial resolution in EEG, and how does it differ between the asleep and awake brain?
EEG has excellent temporal resolution but poor spatial resolution. The asleep brain exhibits more synchronised brain waves, reflecting more coherent cell activity.
Explain how the signal transduction of chemical molecules gives rise to biological sensation.
Chemical molecules in the environment interact with specialized sensory receptors, initiating signal transduction pathways that ultimately lead to biological sensations. For example, in the olfactory system, odorant molecules bind to olfactory receptors located on olfactory receptor neurons (ORNs) within the olfactory epithelium. This binding triggers a cascade of events
Why is resolution a key concept in all measurements, and how does it relate to the study of the nervous system?
Resolution is crucial for discerning fine details. In the nervous system, knowledge at a fine scale and very fast temporal events is required, from the molecular level (e.g., vesicles, synapses, neurotransmitters) to structural changes.
What are neuroscientists typically seeking in the study of the brain, and how does resolution play a role in this pursuit?
Neuroscientists seek reductionist, causal, mechanistic explanations of how system components interact to produce system behaviour. Resolution, both spatial and temporal, is essential for gaining detailed information and understanding the intricate workings of the nervous system.
What is the cascade of events that gives rise to biological sensation
- Odorant Binding: Odorant molecules bind to specific receptors on the dendritic cilia of olfactory receptor neurons.
- GPCR Activation: Odorant receptors are G protein-coupled receptors (GPCRs). Upon odorant binding, GPCR activation initiates intracellular signaling by activating adenylate cyclase II.
- cAMP Production: Adenylate cyclase II catalyzes the conversion of ATP to cyclic AMP (cAMP), leading to an increase in intracellular cAMP levels.
- Ion Channel Opening: Increased cAMP levels result in the opening of cyclic nucleotide-gated (CNG) ion channels, allowing influx of Na^+ and Ca^2+ ions.
- Depolarization: Ion influx leads to depolarization of the olfactory receptor neuron membrane, generating an action potential.
- Action Potential Propagation: Action potentials are propagated along the axon of olfactory receptor neurons to the olfactory bulb in the brain.
- Neurotransmitter Release: Arrival of action potentials at the olfactory bulb triggers neurotransmitter release, conveying the sensory signal to higher brain regions for interpretation.
signal transduction of gustatory systems
- Location: Gustatory receptors are primarily located on taste buds within taste papillae on the tongue, palate, and pharynx.
- Receptor Types: Taste receptors detect five primary tastes: sweet, sour, salty, bitter, and umami. Different taste receptor cells are specialized for detecting specific taste qualities.
- Signal Transduction: Taste receptor cells utilize various signalling mechanisms. For example, sweet and umami tastes involve GPCR-mediated activation of second messenger systems, leading to ion channel opening and depolarization. Sour taste involves the direct influx of H^+ ions through ion channels. Bitter taste receptors utilize GPCRs coupled to G protein gustducin, leading to activation of phospholipase C and intracellular Ca^2+ release.
signal transduction of olfactory systems
- Location: Olfactory receptors are located within the olfactory epithelium in the nasal cavity.
- Receptor Types: Olfactory receptors are specialized for detecting a wide range of odorant molecules, each receptor potentially responsive to multiple odorants.
- Signal Transduction: Olfactory receptors are GPCRs that activate adenylate cyclase upon odorant binding, leading to cAMP production and cyclic nucleotide-gated ion channel opening. This results in membrane depolarization and generation of action potentials.
olfactory vs gustatory systems
Both gustatory and olfactory systems involve the detection of chemical stimuli by specialized receptors, leading to signal transduction and the generation of sensory signals. Additionally, both systems exhibit receptor specificity and utilize GPCR-mediated signaling pathways.
Be able to identify the major elements of the central pathways leading to taste and smell
Olfactory and gustatory pathways
Olfactory pathway
After initial processing in the olfactory bulb, olfactory sensory information is relayed via mitral and tufted cells to higher brain regions, including the olfactory cortex, amygdala, and hippocampus. These regions are involved in odour discrimination, memory, and emotional responses to odours.
gustatory pathway
Taste signals are transmitted from taste buds via cranial nerves (e.g., facial, glossopharyngeal) to the brainstem and then to the thalamus. From the thalamus, taste information is relayed to the gustatory cortex, where taste perception and integration occur.
