Principles of Neuroscience

Question 1

What are some identifiable functions performed by the nervous system?

Answer 1

The nervous system performs various functions, including controlling movement, regulating physiological functions through homeostasis and producing consciousness

Question 2

During which historical periods did views about the brain’s role in thought or experience evolve?

Answer 2

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

Question 3

How does the nervous system contribute to the construction of our internal universe and perception of the external world

Answer 3

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

Question 4

What does the quote “Cogito, ergo sum” signify, and how does it relate to the understanding of the mind?

Answer 4

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

Question 5

How did early views regarding the seat of intellect differ and what observations led to a shift in understanding?

Answer 5

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.

Question 6

What is the nervous system’s composition in vertebrates and what are the components of the CNS and the PNS?

Answer 6

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

Question 7

What are the aims of the subject in understanding neuroscience?

Answer 7

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

Question 8

What is the significance of Neurology as a medical discipline in understanding brain function?

Answer 8

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

Question 9

What was the major insight made during antiquity regarding the brain and the mind?

Answer 9

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

Question 10

Who appreciated the role of the brain in experience and behaviour during Ancient Greece and Ancient Rome?

Answer 10

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.

Question 11

what happens when the message is received i.e. the post-synaptic response

Answer 11

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

Question 12

what is the nature of the transmission between one neuron and another?

Answer 12

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

Question 13

is conduction uni- or bi-directional in the nervous system?

Answer 13

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

Question 14

how are signals transmitted along neural pathways and within neural structures?

Answer 14

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

Question 15

what is the composition of the nervous system?

Answer 15

the nervous system is comprised of neurons and glial cells

Question 16

How did the ability to visualise neurons with microscopes contribute to our understanding of the nervous system

Answer 16

• 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

Question 17

Describe the primary methods for studying functional organisation in the nervous system.

Answer 17

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

Question 18

What is the significance of chemical neurotransmission in the majority of synapses, and how does it differ from electrical synapses?

Answer 18

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.

Question 19

Explain the molecular machinery involved in chemical synapses, focusing on neurotransmitter synthesis, release, and post-synaptic effects.

Answer 19

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.

Question 20

What is neural plasticity, and why is it considered fundamental to the functioning of the nervous system?

Answer 20

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.

Question 21

What role do NMDA channels play in synaptic transmission, and how is calcium involved in this process?

Answer 21

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.

Question 22

Describe the concept of long-term potentiation (LTP) and its importance, especially in the hippocampus.

Answer 22

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.`

Question 23

Explain the mechanisms behind homologous and heterologous potentiation in synaptic plasticity.

Answer 23

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.

Question 24

How does the activation of NMDA receptors contribute to the increased synthesis and trafficking of AMPA receptors in the post-synaptic membrane during LTP?

Answer 24

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.

Question 25

What questions did the discovery of growth cones and dynamic neuronal morphology raise regarding brain development and the stability of the mature brain?

Answer 25

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.

Question 26

How did Cajal’s recognition of superior staining contribute to the understanding of neuronal morphology, specifically in developing tissue?

Answer 26

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.

Question 27

What is the role of protein synthesis in maintaining long-term potentiation, and is it the sole mechanism for increasing synapse activity?

Answer 27

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

Question 28

What is cytoarchitecture, and how is it utilized in classifying parts of the brain?

Answer 28

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.

Question 29

Describe the major divisions of the central nervous system (CNS) and their functions.

Answer 29

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.

Question 30

Discuss the neuron doctrine and how it revolutionized our understanding of the nervous system.

Answer 30

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.

Question 31

What did Charles Sherrington contribute to the acceptance of the neuron doctrine, and what observations supported his views on synapses?

Answer 31

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.

Question 32

How does the wiring of the nervous system through synapses allow for information transmission, and what is the significance of plasticity in neuronal connectivity

Answer 32

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.

Question 33

Explain the process of long-term potentiation (LTP) in the context of Schaffer-collateral-CA1 synapses.

Answer 33

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.

Question 34

How does a burst of activity, such as tetanus, affect the strength of synapses in long-term potentiation?

Answer 34

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

Question 35

Describe the roles of glutamate, AMPA receptors, and NMDA receptors in the molecular mechanisms underlying long-term potentiation.

Answer 35

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

Question 36

What is the key cell of the nervous system?

Answer 36

the neuron

Question 37

Name the four types of macroglial cells that support neurons.

Answer 37

astrocytes, oligodendrocytes, Schwann cells (PNS), ependymal cells, satellite cells (PNS)

Question 38

What is the role of microglia in the nervous system?

Answer 38

microglia are resident immune cells that maintain the health of the brain and CNS by acting as a defense mechanism agaisnt diseases and injuries

Question 39

Why is it called the quadripartite synapse, and what are its four components?

Answer 39

because of its four components: pre and post-synaptic neurons, microglia, macroglia (astrocytes)

Question 40

List three passive functions of macroglial cells.

Answer 40

Uptake and recycling of neurotransmitters, siphoning of potassium during depolarization, and maintenance of the blood-brain barrier.

Question 41

What is the active function of macroglial cells in controlling neural function?

Answer 41

modulate neural function

Question 42

How do glial cells contribute to maintaining ion balance by siphoning potassium?

Answer 42

Glial cells express inwardly rectifying potassium channels, which help remove potassium from the extracellular environment during depolarization.

Question 43

Which neurotransmitters are recycled by glial cells, and what transporters do they express for this purpose?

Answer 43

GABA and glutamate and they express GABA and glutamate transporters for this purpose

Question 44

What initiates calcium waves in glial cells, and what role do these waves play in communication between neurons?

Answer 44

Calcium waves are initiated by neurotransmitters like ATP and glutamate, trauma, spontaneous events, and inflammatory mediators. Neurons can communicate through axons.

Question 45

What molecules are released by glial cells as neuromodulators, and what are they collectively known as?

Answer 45

Glial cells release ATP and glutamate, collectively known as gliotransmitters.

Question 46

How do astrocytes, a type of macroglial cell, contribute to vascular regulation in the CNS?

Answer 46

Astrocytes connect neurons and blood vessels, allowing them to communicate messages to dilate or constrict vessels as needed through intracellular calcium signals.

Question 47

How does intracellular calcium in glial cells influence neuronal activity?

Answer 47

An increase in intracellular calcium in glial cells can lead to the release of ATP, resulting in neuronal hyperpolarization and protection.

Question 48

Describe the role of microglia in the nervous system, highlighting their dynamic nature and functions.

Answer 48

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.

Question 49

What are the passive and active functions of macroglial cells, and how do they contribute to the nervous system?

Answer 49

Passive functions include neurotransmitter deactivation, potassium siphoning, and maintaining the blood-brain barrier. Active functions involve releasing gliotransmitters and modulating the vasculature.

Question 50

How do microglia regulate the vascular system, and what induces constriction at microglial contacts?

Answer 50

Microglia regulate the vascular system by touching blood vessels. Fractalkine induces constriction at microglial contacts.

Question 51

How do microglia contribute to refining neural circuits during development?

Answer 51

Microglia prune or “eat” synapses that are not being used, unwanted, or weak, allowing only strong synapses to develop into adulthood.

Question 51

Why are microglia considered local defence cells, and what is their response to inflammation or injury?

Answer 51

Microglia are local defense cells that rapidly change in response to inflammation or injury, resembling phagocytic macrophages.

Question 52

What are the consequences of the loss of glial functions in diseases?

Answer 52

Loss of neurotransmitter uptake can cause excessive stimulation of neurons, while loss of potassium uptake can lead to changes in water balance and oedema.

Question 53

What happens during the “inside-out” formation of cortical layers?

Answer 53

neurons are generated at remote locations and migrate into place, with the deepest layers forming first and those closer to the surface assembling last

Question 54

How is the order of cortical layer formation described?

Answer 54

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

Question 55

Why study the development of the nervous system?

Answer 55

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

Question 56

What are the integrated steps involved in the construction of the nervous system?

Answer 56

the construction of the nervous system involves a continuum of steps

1. neural induction
2. neurulation
3. morphogenesis and patterning of neural tube
4. neurogenesis
5. neuronal migration
6. axon growth and path findings
7. synaptogenesis
8. gliogenesis/myelination

Question 57

What is neural induction?

Answer 57

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

Question 57

What is the significance of failures in neural tube closure?

Answer 57

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

Question 57

How many neurons and synaptic connections are there in the human brain?

Answer 57

the human brain has approximately 10^11 neurons and 10^14 synaptic connections

Question 58

According to Santiago Ramon y Cajal, why is it easier to study the developing brain?

Answer 58

because it is more accessible than the impenetrable full-grown forest of a mature brain

Question 59

What are the primary brain vesicles formed after neural tube closure?

Answer 59

prosencephalon (forebrain)

mesencephalon (midbrain)

rhombencephalon (hindbrain)

Question 60

What is the role of radial glia in neuroepithelial development?

Answer 60

radial glia, derived from neuroepithelial cells, serve as multipotent neural progenitor cells, producing neurons and glia through both symmetric and asymmetric cell divisions

Question 61

What is the significance of the term ‘sex differences’?

Answer 61

‘Sex differences’ refer to the distinctions between males and females, encompassing various aspects such as genetics, anatomy, physiology, and behavior.

Question 62

Define chromosomal sex/genetic sex.

Answer 62

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.

Question 63

What are sex chromosomes, and what role do they play in sex determination

Answer 63

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).

Question 64

Where are the genes responsible for sex determination located?

Answer 64

The genes responsible for sex determination are located on the sex chromosomes.

Question 65

During gonad development, what hormones play a crucial role, and what is their impact?

Answer 65

Gonad development involves the synthesis of sex hormones. In males, the testes produce testosterone, while in females, the ovaries produce estrogens and progesterone.

Question 66

What is the SRY gene, and what is its role in sexual development?

Answer 66

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.

Question 67

How are the primary types of circulating sex hormones determined?

Answer 67

The sex chromosomes determine the primary types of circulating sex hormones, with males producing testosterone and females producing estrogens and progesterone.

Question 68

What is the primary source of sex steroids, and what is the common precursor for their biosynthesis?

Answer 68

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.

Question 69

Describe the temporal changes in testosterone synthesis in males during early development and puberty.

Answer 69

In males, there is a transient synthesis of testosterone pre-birth, leading to masculinization. Testosterone levels increase at puberty, reaching relatively constant adult levels.

Question 70

Does everything depend on sex steroids, or are there other genetic mechanisms for determining sex?

Answer 70

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.

Question 71

How does estrogen synthesis vary in females during different life stages?

Answer 71

Circulating estrogen (and progesterone) levels in females are low until puberty. During adulthood, cyclical patterns of estrogen and progesterone synthesis occur, decreasing in menopause.

Question 71

How is sex steroid synthesis by the gonads regulated, and what determines the levels and pattern of FSH/LH secretion?

Answer 71

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.

Question 72

Differentiate between the sex hormones synthesised by male and female gonads.

Answer 72

Male gonads (testes) synthesize testosterone, while female gonads (ovaries) synthesize estrogens and progesterone.

Question 73

Does everything depend on sex steroids, or are there other genetic mechanisms for determining sex?

Answer 73

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.

Question 74

What evidence suggests hormone-independent genetic effects on brain regions?

Answer 74

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.

Question 75

What is meant by the term “organisational effects” concerning the early effects of steroids on the nervous system?

Answer 75

Organizational effects refer to permanent changes in anatomical, physiological, and behavioral aspects induced by steroids during early development, contributing to sexual dimorphism.

Question 76

Describe the genomic pathway of steroid action on the nervous system.

Answer 76

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.

Question 77

Provide examples of behaviours that exhibit sexual dimorphism and are influenced by anatomical and physiological differences.

Answer 77

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.

Question 78

Are steroid receptor expression patterns uniform throughout the nervous system?

Answer 78

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.

Question 79

Besides steroids, what are the contributors to sexual dimorphism in neuronal connections and activity?

Answer 79

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.

Question 80

What is the critical role of aromatase in masculinising the brain?

Answer 80

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.

Question 81

Are the effects of steroids on the maturing/mature nervous system reversible?

Answer 81

Throughout adulthood, the effects of androgens and estrogens on the nervous system are generally reversible. However, sustained hormone levels can

Question 82

What is the fundamental limitation in imaging techniques such as microscopes, telescopes, or eyes, and how does it affect spatial resolution?

Answer 82

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

Question 83

How do microscopy techniques like STED and STORM overcome the diffraction limit, and what is their mechanism?

Answer 83

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.

Question 84

What is the significance of micro-electrodes and patch-clamp electrodes in understanding neuronal activity, and how do they contribute to high-resolution electrophysiology?

Answer 84

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.

Question 85

How do brain imaging techniques differ in terms of spatial and temporal resolution, and what are some examples of whole-brain imaging technologies?

Answer 85

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.

Question 86

Explain how a CT or CAT scan works, highlighting its principle and potential harm.

Answer 86

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.

Question 87

What does MEG measure, and why is it often combined with MRI or CT maps?

Answer 87

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.

Question 88

What is the principle behind fMRI, and how does it determine neurobiological correlates of behaviour?

Answer 88

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.

Question 89

What is the trade-off between temporal and spatial resolution in EEG, and how does it differ between the asleep and awake brain?

Answer 89

EEG has excellent temporal resolution but poor spatial resolution. The asleep brain exhibits more synchronised brain waves, reflecting more coherent cell activity.

Question 90

Explain how the signal transduction of chemical molecules gives rise to biological sensation.

Answer 90

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

Question 90

Why is resolution a key concept in all measurements, and how does it relate to the study of the nervous system?

Answer 90

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.

Question 91

What are neuroscientists typically seeking in the study of the brain, and how does resolution play a role in this pursuit?

Answer 91

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.

Question 92

What is the cascade of events that gives rise to biological sensation

Answer 92

1. Odorant Binding: Odorant molecules bind to specific receptors on the dendritic cilia of olfactory receptor neurons.
2. GPCR Activation: Odorant receptors are G protein-coupled receptors (GPCRs). Upon odorant binding, GPCR activation initiates intracellular signaling by activating adenylate cyclase II.
3. cAMP Production: Adenylate cyclase II catalyzes the conversion of ATP to cyclic AMP (cAMP), leading to an increase in intracellular cAMP levels.
4. 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.
5. Depolarization: Ion influx leads to depolarization of the olfactory receptor neuron membrane, generating an action potential.
6. Action Potential Propagation: Action potentials are propagated along the axon of olfactory receptor neurons to the olfactory bulb in the brain.
7. Neurotransmitter Release: Arrival of action potentials at the olfactory bulb triggers neurotransmitter release, conveying the sensory signal to higher brain regions for interpretation.

Question 93

signal transduction of gustatory systems

Answer 93

• 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.

Question 94

signal transduction of olfactory systems

Answer 94

• 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.

Question 95

olfactory vs gustatory systems

Answer 95

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.

Question 96

Be able to identify the major elements of the central pathways leading to taste and smell

Answer 96

Olfactory and gustatory pathways

Question 97

Olfactory pathway

Answer 97

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.

Question 98

gustatory pathway

Answer 98

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.