Sensory Physiology - Class

Question 1

what is a sensory receptor?

Answer 1

A sensory receptor is a specialized cell or cell component that detects and responds to specific types of stimuli, such as light, heat, sound, pressure, or chemical signals, converting them into electrical signals that are communicated to the nervous system, initiating sensory perception or response.

Question 2

classification of sensory receptors?

Answer 2

Classification of Sensory Receptors:

Mechanoreceptors: Detect mechanical forces (e.g., touch, pressure, vibration).

Thermoreceptors: Respond to changes in temperature.

Nociceptors: Sensitive to pain-causing stimuli.

Photoreceptors: Respond to light (e.g., rods and cones in the eye).

Chemoreceptors: Detect chemical stimuli (e.g., taste, smell).

Electroreceptors: Detect electric fields (mostly in aquatic animals).

Question 3

steps in sensory reception

Answer 3

Stimulus Detection: Specific receptor cells respond to environmental stimuli.

Transduction: Conversion of the stimulus into an electrical signal by the receptor.

Amplification: Enhancement of the signal within the sensory cell.

Transmission: Sending the signal to the central nervous system.

Integration: The brain processes the information and forms an appropriate response.

Question 4

Aspects of Sensory Stimulus Encoding:
modality, intensity, location, and duration

Answer 4

Aspects of Sensory Stimulus Encoding:

Modality: Type of stimulus or the sensation it produces (e.g., heat, sound, light).

Intensity: Strength or amplitude of the stimulus, often encoded by the frequency of action potentials.

Location: Determined by the specific location of the activated receptors within the body or sensory organ.

Duration: Length of time the stimulus lasts, reflected by the duration of the receptor’s response.

Question 5

What is the sensory receptor for each type of stimulus:

1. chemical
2. mechanical
3. light
   4.Temperature
4. Magnetic fields
5. Electrical fields

Answer 5

1. chemoreceptor
2. mechanoreceptor
3. photoreceptor
4. thermoreceptor
5. magnetoreceptor
6. electroreceptor

Question 6

How do Ap’s code for Intensity of stimulus?

Answer 6

By frequency and # of neurons firing.

Question 7

How do Ap’s code for location and duration of stimulus?

Answer 7

Location: Action potentials (APs) encode the location of a stimulus based on the specific sensory neurons that are activated. Different sensory neurons respond to stimuli in specific body areas, so when a neuron fires, the brain interprets the signal as coming from its respective location.

Duration: The duration of a stimulus is encoded by the frequency and pattern of APs. A sustained stimulus leads to a prolonged series of APs, while a brief stimulus results in a shorter burst of APs. The temporal pattern of action potentials helps the brain determine how long a stimulus lasts.

Question 8

labeled line vs cross fiber coding?

Answer 8

These are two theories for how modality is encoded for.

Labeled Line Coding: Each sensory neuron responds to a specific type of stimulus from a specific location, and the brain interprets the signal based on which neuron is firing. This means the pathway from receptor to brain is “labeled” for a specific sensation.

Cross Fiber Coding: Different types of sensory stimuli are encoded by patterns of activity across many neurons. Each neuron can respond to multiple stimuli, and different combinations of neuronal activity can represent different stimuli, allowing more complex interpretations of sensory input.

Question 9

the difference between taste and smell?

Answer 9

Taste (Gustation): Involves chemoreceptors on the tongue that detect dissolved compounds, resulting in basic taste sensations like sweet, sour, salty, bitter, and umami.
–> Typically dissolved chemicals are in HIGH concentration

Smell (Olfaction): Relies on olfactory receptors in the nasal cavity that respond to airborne chemicals, offering a more nuanced range of complex scents and contributing significantly to flavor perception.
–> Typically, dissolved chemicals are at low concentration

Question 10

5 categories of taste and their transduction mechnisms:

Answer 10

Sweet: Detected by G protein-coupled receptors (T1R2 + T1R3) that activate a second-messenger system to block potassium channels, leading to cell depolarization.

Sour: Triggered by hydrogen ions (H+) from acidic substances that directly enter taste cells, blocking potassium channels and causing depolarization.

Salty: Sodium ions enter taste cells through sodium channels, directly leading to depolarization.

Bitter: Detected by various G protein-coupled receptors (T2Rs), which activate a second-messenger system that leads to the release of calcium from internal stores, causing neurotransmitter release.

Umami: Detected by G protein-coupled receptors (T1R1 + T1R3) similar to sweet taste receptors, and involves a second-messenger system that also blocks potassium channels for cell depolarization.

Question 11

olfactory reception and combinatorial encoding

Answer 11

Olfactory Reception: Olfactory receptors in the nose detect molecules (odorants) and trigger signal transduction pathways. Each receptor neuron expresses only one type of olfactory receptor protein, which binds to specific chemicals in the air.

Combinatorial Encoding: Each odorant can bind to multiple types of olfactory receptors with varying affinities, and each receptor can be activated by multiple odorants. The brain interprets the complex pattern of receptor activation across the olfactory bulb to identify and discriminate different odors. This encoding allows for the perception of a vast array of odors from a relatively limited number of receptors.

Question 12

olfactory diversity across species.

Answer 12

Variation in Receptor Genes: Different species have varying numbers of olfactory receptor genes, influencing their sense of smell. For example, dogs have about 1,000 olfactory receptor genes, humans around 400, and some aquatic mammals have fewer due to their adaptation to underwater environments.

Sensory Adaptation: Species adapt their olfactory capabilities based on ecological needs. Predators typically have advanced olfactory systems for tracking prey, whereas some prey species have developed acute smell for detecting predators or foraging.

Functional Differences: The structural and functional organization of the olfactory system can differ significantly, affecting sensitivity and discrimination of odors crucial for survival, reproduction, and social interactions.

Question 13

vomeronasal organ

Answer 13

Function: Detects pheromones, chemicals important for inter-species communication related to reproduction and social behaviors.

Location: Situated at the base of the nasal cavity in many vertebrates, including reptiles, some mammals, and amphibians.

Use: Primarily involved in detecting sex and territorial pheromones, influencing behaviors such as mating and aggression.

Absence in Some Species: Not found in adult humans and some other primates, suggesting a reduced role or different evolutionary pathway for pheromone detection in these species.

Question 14

taste receptor and taste bud?

Answer 14

Taste Receptor: Specialized sensory cells located within taste buds that detect specific chemical stimuli and initiate signal transduction pathways leading to taste perception.

Taste Bud: A cluster of taste receptor cells found mainly on the tongue, each taste bud contains 50-100 receptor cells of various types that respond to different taste qualities (sweet, sour, salty, bitter, umami). Taste buds are housed in papillae, the small bumps visible on the tongue’s surface.

Question 15

internal vs external chemoreceptors?

Answer 15

Internal Chemoreceptors:
Location: Found within the body, typically in the bloodstream or tissues.
Function: Detect changes in the internal environment, such as CO2 and pH levels, important for maintaining homeostasis.

External Chemoreceptors:
Location: Located on body surfaces exposed to the external environment, such as the tongue and nose.
Function: Sense external chemical stimuli, including tastes and smells, crucial for feeding, predator detection, and social interaction.

Question 16

process of taste pathway?

Answer 16

Stimulus: Chemicals from ingested food or drink dissolve in saliva.

Receptor Activation: These chemicals bind to specific receptors on the surface of taste cells within the taste buds.

Signal Transduction: Binding triggers an intracellular response, often involving ion channels or second-messenger systems, generating an electrical signal.

Nerve Impulse: The electrical signal prompts release of neurotransmitters, generating a nerve impulse in the gustatory nerves.

Transmission to Brain: Impulses are carried via the facial, glossopharyngeal, and vagus nerves to the gustatory cortex in the brain, where the perception of taste is recognized and interpreted.