BIOL 1202 EXAM 4; CH 50 Notes Review

Sensory reception, transduction, transmission, and perception. All sensory pathways have these 4 basic functions in common.

What are the 4 basic functions all sensory pathways have?

Sensory Reception:

The beginning of a sensory pathway. This is the detection of stimuli by sensory receptors. They interact with stimuli, inside and outside the body.

Components: sensory receptors

Sensory receptors

sensory cells or organs. Used in sensory reception.

Transduction

The conversion of stimulus energy into a change in the membrane potential of a sensory receptor. This change in membrane potential is called a receptor potential.

Components: Receptor Potential

Receptor Potential

The conversion of stimulus energy into a change in the membrane potential of a sensory receptor. This change in membrane potential is called _________.

- These are graded potentials; their magnitude varies tremendously with the strength of the stimulus.

Transmission

Sensory information travels through the nervous system as action potentials.

- The size of a receptor potential increases with the intensity of the stimulus.

- In sensory neurons that spontaneously generate action potentials at a low rate, a stimulus changes how often an action potential is produced.

Components: Action Potentials

Action Potentials

An electrical signal that propagates (travels) along the membrane of a neuron or other excitable cell as a nongraded (all-or-none) depolarization.

Perception

The brain's construction of stimuli

Stimuli from different sensory receptors travel as action potentials along dedicated neural pathways.

The brain distinguishes stimuli from different receptors based on the path by which the action potentials arrive.

Component: Neural Pathways

Neural Pathways

a series of connected neurons that send signals from one part of the body to another.

Amplification

the strengthening of a sensory signal during transduction

Sensory Adaptation

a decrease in responsiveness to continued stimulation.

Answer: The difference between amplification and adaptation is amplification strengthens the sensory signal while sesnsory adaptation decreases the sensory signal in response to continued stimulation.

What is the difference between AMPLIFICATION and ADAPTATION?

Energy is related to sensory adaptation because sensory adaptation is within organisms to help conserve energy.

Example: Saltwater tank and an Anemone (long type of jellyfish). If you take your finger and touch the tentacle, its going to contract. Eventually It will relax and go back to normal. If you touch it again, it will contract. If you touch it multiple times, the jelly fish will realize the touching is not causing harm and it will stop reacting. If it didn't stop responding, it would end up utilizing all its energy.

How is energy related to sensory adaptation and cite an example we discussed in lecture?

Answer: Mechanoreceptors, Chemoreceptors, Electromagnetic receptors, Thermoreceptors, and Pain receptors.

What are the 5 types of SENSORY RECEPTORS?

Mechanoreceptors

Receptors that detect/sense physical deformation caused by forms of mechanical energy (pressure, touch, squeezing).

- typically consist of ion channels linked to structures that end outside the cell, such as "hairs" (cilia).

Physically: Respond primarily to gentle pressure or vibration. This can be detected by the cilia (hair).

Chemically: The mammalian sense of touch relies on mechanoreceptors that are dendrites of sensory neurons.

The opening of the channel allows cations (typically $Na^+$ or $Ca^{2+}$) to flow into the cell, following their electrochemical gradient.

How do Mechanoreceptors work physically and chemically?

The mammalian sense of touch relies on mechanoreceptors that are dendrites of sensory neurons.

How would mechanoreceptors be used in the animal kingdom?

Chemoreceptors

Receptors that detects a chemical stimulus, such as a solute or an odorant. It transmits information about the total solute concentration of a solution or responds to individual kinds of molecules. They can do either.

- distributed throughout the body to monitor both the external environment (like what you smell or taste) and the internal environment (like the oxygen levels in your blood).

Examples: Olfactory System (smell), Gustatory System (Taste)

Physically: The process begins when a specific molecule, known as a ligand (like a "tasty" sugar molecule or an "odorous" airborne chemical), comes into contact with the receptor cell.

Aqueous Interface: For most chemoreceptors, the molecule must first dissolve in a fluid—such as saliva for taste or mucus for smell—to reach the receptor proteins.

Specific Binding: The molecule binds to a highly specific receptor protein embedded in the cell's plasma membrane. This is often described as a "lock and key" mechanism.

Chemically: When a stimulus molecule binds to a chemoreceptor, the chemoreceptor becomes more or less permeable to ions.

How do Chemoreceptors work (physically and chemically)?

- The antennae of the male silkworm moth have very sensitive specific chemoreceptors.

How would Chemoreceptors be used in the animal kingdom?

Electromagnetic Receptors

Receptors that detect electromagnetic energy such as light, electricity, + magnetism.

They can be located in multiple different spots. This can be the eye, heat-sensing organs (in snakes). For the platypus, its on its bill (flat and duck-like, aiding in foraging for food).

- Many animals apparently migrate using Earth's magnetic field to orient themselves.

Physically: They can easily be detected through vibrations or sight.

Chemically: The "trigger" for the entire process is a small light-absorbing molecule called retinal, which is bound to a specific protein called an opsin (together forming rhodopsin in rod cells).

Isomerization: When a photon of light hits the retinal, it physically changes shape from a bent form (cis-retinal) to a straight form (trans-retinal).

Opsin Activation: This change in the shape of retinal destabilizes and activates the opsin protein.

How do Electromagnetic Receptors (physically and chemically)?

1. The platypus has electroreceptors on its bill that can detect the electric field generated by prey.

2. Many animals apparently migrate using Earth's magnetic field to orient themselves (Beluga whales)

How would Electromagnetic Receptors be used in the animal kingdom?

Thermoreceptors

Receptors that detect heat and cold. This helps snakes detect infrared radiation emitted by warm prey.

In humans, located in the skin and in the anterior hypothalamus.

Physically: The receptor opens a calcium channel in response not only to capsaicin but also to high temperatures ( or higher). In essence, spicy foods taste "hot" because they activate the same receptors as hot soup and coffee.

Chemically: Jalapeno and cayenne peppers that we describe as "hot" contain a substance called capsaicin. Applying capsaicin to a sensory neuron causes an influx of calcium ions.

How do they Thermoreceptors (physically and chemically)?

- Certain snakes rely on thermoreceptors to detect infrared radiation emitted by warm prey.

- Mammals have a variety of thermoreceptors, each specific for a particular temperature range

How would Thermoreceptors be used in the animal kingdom?

Pain receptors (nociceptors)

Receptors that, in humans, detect stimuli that reflect harmful conditions. They respond to excess heat, pressure, or chemicals released from damaged or inflamed tissues.

these receptors are often found in the skin's epidermis

Physically: By triggering defensive reactions, such as withdrawal from danger, the perception of pain serves an important function.

Chemically:

- The capsaicin receptor of mammals can detect dangerously high temperatures, so it also functions as a pain receptor.

- When tissues are damaged, they produce prostaglandins—local regulators of inflammation—that increase the sensitivity of nociceptors to noxious stimuli.

How do Pain receptors (nociceptors)(physically and chemically)?

Detect stimuli that reflect harmful conditions.

What does a NOCICEPTOR detect?

Comparative Pain Scale: A scale used within the medical field to describe level of pain within a patient. It goes from a scale of 1-10. Helps nurses/doctors know the severity of your condition/pain.

What is a comparative pain scale chart and how is it used in the medica field?

If you are a "10" on the comparative pain scale, the doctor might interpret that as extreme pain and an emergency. A "10" means it is an unbearable pain.

If you say you are a "10" on the comparative pain scale, how might a doctor interpret that?

Statocyst

A type of mechanoreceptor that functions in equilibrium in invertebrates by use of statoliths, which stimulate hair cells in relation to gravity. Detects the movement of granules (Statolith).

Statolith

Granules whose movements are detected by mechanoreceptors. These mechanoreceptors are contained within something.

The function statocyst play a role in is helping most invertebrates maintain equilibrium using mechanoreceptors located in statocyst.

What function does statocyst play a role in?

Provide information about the body position with respect to gravity.

What function does statolith play a role in?

Statocysts are specialized organs that help invertebrates sense gravity and maintain equilibrium. They contain statoliths, which are dense granules formed by sand or other materials. These statoliths sit freely within a chamber lined with ciliated cells. When the animal changes position, the statoliths resettle at the lowest point of the chamber, stimulating mechanoreceptors on these ciliated cells.

The statoliths are granules which can be dectected by mechanoreceptors.

How do statocysts and statoliths work?

Statoliths and statocysts are not exclusive to animals. In contrast, plants also have statoliths, but they are located within intracellular organelles.

Are statocyst and statoliths just present in animals or do we see these structures in plants also?

Vibrating objects create pressure waves in air, causes vibration of the tympanic membrane (three bones in middle of ear) transmit vibrations to oval window, creates pressure in fluid inside cochlea, pushes down on cochlear duct and basilar membrane, hair cells in vibrate up and down and create action potentials sent to brain.

Describe the process of HEARING in mammals

Tympanic Membrane

Another name for the eardrum, the membrane between the outer and middle ear. Contains the maleus, incus, and stapes.

Maleus, Incus, and Stapes

What are the 3 types of bones within the middle ear?

Oval Window

In the vertebrate ear, a membrane-covered gap in the skull bone, through which sound waves pass from the middle ear to the inner ear.

Round Window

In the mammalian ear, the point of contact where vibrations of the stapes create a traveling series of pressure waves in the fluid of the cochlea. It is at the end of the tympanic canal.

Cochlea

The complex, coiled organ of hearing that contains the organ of Corti.

- The cochlea can distinguish pitch because the basilar membrane is not uniform along its length.

- The basilar membrane and hair cells vibrate up/down.

- The cochlea can distinguish pitch because the basilar membrane is not uniform along its length.

- Each region of the basilar membrane is tuned to a particular vibration frequency.

Describe the cochlear duct and basilar membrane

Hair Cells

sensory cells with hair-like projections that detect motion.

The bending of _____ depolarizes the membranes of mechanoreceptors and sends action potentials to the brain via the auditory nerve.

Volume

the amplitude of the soundwave (distinguished by Cochlea)

Pitch

the frequency of the soundwave (distguished by basilar membrane that is tuned to a particular vibration frequency.)

Volume: AMPLITUDE of the soundwave

Pitch: the FREQUENCY of the soundwave

What is the the difference between VOLUME and PITCH?

To hear sounds, we rely on hair cells, sensory cells with hair-like projections that detect motion. They can vibrate up and down.

The bending of hair cells depolarizes the membranes of mechanoreceptors and sends action potentials to the brain via the auditory nerve.

If the hair cells get damaged, which can be due to exposure of extremely loud sounds, it can cause the hair cells to break which causes lose of hearing.

What roles do HAIR CELLS play and what happens if they get damaged?

There are three bones in the middle ear that are involved in the process of hearing. The Malleus, Incus, and Stapes.

How many bones are there in the middle ear that are involved in the process of hearing?

The three parts/regions of the human ear is Outer ear, Middle ear, and Inner ear.

What are the 3 parts/regions of the human ear?

When you get an ear infection, it typically involves inflammation and infection of the middle ear, often due to bacteria or viruses. Symptoms can include ear pain, fever, irritability, and sometimes fluid drainage from the ear.

Treatment depends on the cause and severity of the infection. Bacterial infections might require antibiotics, while viral infections often resolve on their own. If fluid persists, a doctor might recommend ear tubes to help with drainage.

Diagnosis: A doctor will examine your ear using an otoscope to look for signs of infection, such as redness, swelling, or fluid behind the eardrum.

What happens when you get an ear infection and how would a doctor diagnose and treat such a condition?

Equilibrium

In the context of human biology, refers to a state of balance within the body's internal environment.

In the human body, equilibrium is a dynamic state where metabolic processes are constantly adjusted to maintain balance. Unlike isolated systems that reach equilibrium and stop working, living cells avoid equilibrium to stay alive. Metabolic pathways in cells are kept from reaching equilibrium by continuously moving materials in and out of the cell. This allows cells to perform work throughout their life.

How is EQUILIBRIUM processed in the human body?

Utricle

a key component of the inner ear involved in maintaining balance and perceiving linear movement.

Saccule

a chamber in the inner ear that helps detect body position and movement. It works alongside the utricle to perceive gravity and linear motion.

The utricle and ______ contain hair cells projecting into a gelatinous material.

Otoliths

granules embedded in the gelatinous material, of the utricle and saccule, that allows us to perceive position relative to gravity or linear movement.

Lateral Line System

System in gnathostomes where rows of organs sensitive to vibrations are located along each side of the body of aquatic gnathostomes.

- The pick up the vibrations and respond to the environment around them

- Otoliths are formed: Otoliths are embedded within a gelatinous material inside the chambers called the utricle and saccule, located in the vestibule behind the oval window of the inner ear

- We can infer that otoliths help us perceive position relative to gravity. They help us know where we are.

How are Otolith's formed and what information can you infer about this structure?

In other vertebrate, equilibrium is processed through three semicircular canals that contain fluid and can detect angular movement in any direction.

- Fishes have only a pair of inner ears near the brain.

- Most fishes and aquatic amphibians also have a lateral line system along both sides of their body.

- The lateral line system contains mechanoreceptors with hair cells that detect/respond to water movement.

How is EQUILIBRIUM processed in other vertebrates? (besides humans)

Sight begins when photons enter the eye and strike rods and cones, which are photoreceptor cells in the retina. These cells contain visual pigments that absorb light, initiating a series of biochemical changes. The energy from photons is captured by retinal molecules within rhodopsin, a visual pigment.

Eye Structure: Light enters through the cornea and pupil, regulated by the iris. It then passes through the lens to reach the retina.

Retina Function: The retina contains layers of neurons that relay visual information from photoreceptors to the optic nerve and brain.

Photoreceptors: Rods detect light intensity for night vision; cones provide color vision with sensitivity to red, green, or blue light.

Visual Pigments: Retinal changes shape upon absorbing light, activating opsin proteins and generating action potentials sent to the brain for image perception.

How is SIGHT processed in the human body?

Photoreceptors

cells that contain light-absorbing pigments molecules

Photoreceptors

- Light detectors in the animal kingdom range from simple clusters of cells that detect direction and intensity of light to complex organs that form images.

- Light detectors all contain __________, cells that contain light-absorbing pigments molecules

Retina

The light-absorbing pigment in rods and cones of the vertebrate eye.

Lens

A transparent disk of protein.

Optic Disk

A part of the eye within the retina. Lacks photoreceptors and thus forms a blind spot, where light is not detected.

Opsin

A membrane protein that the retinal is bound to.

Rods

A type of photoreceptor cell that is more sensitive to light, but do not detect colors.

Cones

A type of photoreceptor cell that provide color vision.

- Photoreceptors: cells that contain light-absorbing pigment molecules.

- They work by: specialized cells in the retina of the eye that detect light and convert it into signals for the brain to interpret as visual images. There are two main types: rods and cones.

What is a PHOTORECPTOR and how do they work?

- Most invertebrates have a light-detecting organ.

- Insects, crustaceans, and some polychaete worms have compound eyes, which consist of up to several thousand light detectors called ommatidia.

- Compound eyes are very effective at detecting movement.

- Insects have excellent color vision, and some can see into the ultraviolent range.

- Among invertebrates, single-lens eyes are found in some jellies and polychaete worms, as well as spiders and many mollucsc.

- They work on a camera-like principle: The iris changes the diameter of the pupil to control how much light enters.

How does vision differ in invertebrates versus vertebrates?

- Planarians have very simple light-detecting organs

- A pair of ocelli ("eyespots") are located near the head.

- These allow planarians to move away from light and seek shaded regions

How do Planarians see? State information about their vision/seeing process.

Compound Eye

A type of multifaceted eye in insects and crustaceans consisting of up to several thousand light-detecting, focusing ommatidia.

Ommatidia

light detectors that are what the compound eye consists of.

Insects, birds, fish, and reptiles.

What organisms rely on the use of the ultraviolet range of electromagnetic spectrum?

Single-lens eye

The camera-like eye found in some jellies, polychaete worms, spiders, and many molluscs. Eye that contains a single lens. The eye of all vertebrates.

The Blind Spot

Also known as the optic disk. Lacks photoreceptors and thus forms a blind spot, where light is not detected. You can detect your own blind spot by covering one eye and focusing on an image which will then disappear if its in your blind spot.

Example: In class, we looked at a figure with a plus and circle. After covering our left eye, and focusing on the plus sign. The circle became non-visible.

How can you detect your OWN blind spot?

The difference between rods and cones are...

Rods: Sensitive to light, but do not detect colors.

Cones: Provide color vision. Sensitive too different wavelengths or light (Red-sensitive, Green-sensitive, and Blue-sensitive cones). They are less sensitive to light compared to rods.

What is the difference between RODS and CONES, what do they detect?

Location: Located in the retina. Primarily found in the peripheral regions of the retina, away from the fovea, which is the center of the visual field

Where is the location of rods in the eye?

Location: densely packed in the fovea, the center of the retina, where they provide sharp central vision.

Where is the location of cones in the eye?

Processing of Visual Information in the Brain

- The optic nerves meet at the optic chiasm near the center of the base of the cerebral cortex.

- Sensations from the left visual field of both eyes are transmitted to the right side of the brain.

- Sensations from the right visual field of both eyes are transmitted to the left side of the brain.

How does processing of visual information in the brain take place?

Ishihara Color Test

A test made to test colored vision. Its to see if there are any color blindness within your eyes.

- This test would be administered to make sure an individual can see certain wavelengths of light and distinguish wavelengths of light.

- The Ishihara color test works by a researcher showing an individual different plates which show different colors and numbers. Theres a number in the background. If you do not see any numbers, you may be color deficient. Approximately 5-8% of males experience color blindness compared to fewer than 1% of females. This is because females would need mutations on both X chromosomes to exhibit the condition.

Why would the ISHIHARA COLOR TEST be administered and how does it work?

Color vision mutations differ, in this example we looked at male squirrel monkeys, because male squirrel monkeys have a hard time distinguishing red from green.

Color vision mutations, particularly those affecting red and green perception, are more common in males than females due to their genetic basis. These mutations occur in the genes for photopsin proteins, which are responsible for color perception.

Approximately 5-8% of males experience color blindness compared to fewer than 1% of females. This is because females would need mutations on both X chromosomes to exhibit the condition.

How do color vision mutations differ between males and females?

Color blindness, particularly red-green color blindness, is often inherited as an X-linked trait. This means the genes responsible for this condition are located on the X chromosome.

Currently, there is no widespread cure for color blindness. However, gene therapy has shown promise in experimental settings. For instance, studies on squirrel monkeys demonstrated that injecting a virus containing the missing opsin gene into the retina could restore full color vision after several weeks.

Can color blindness be cured?

Nearsighted

sight where people have eyeballs that are too long or corneas. People can only see things UP CLOSE clearly (literally your vision). Also called Myopia.

Farsighted

sight where people have eyeballs that are too short or corneas. People can only see things far away clearly (they be needing reading glasses). Also called Hyperopia.

The difference: nearsighted means you can only see things UP CLOSE clearly and farsighted means you can only see things FAR AWAY clearly.

What is the difference between people that are NEARSIGHTED versus FARSIGHTED?

Nearsighted: Myopia

Farsighted: Hyperopia

What are the scientific terms for nearsightedness and farsightedness?

You can correct vision impairments through contact lenses, glasses, or doing some type of surgery on the eye.

How do you correct vision impairments?

Taste is processed in the human body through receptor cells for taste in mammals are modified epithelial cells organized into taste buds, located in several areas of the tongue and mouth.

Most taste buds are associated with projections called papillae. Any region of the tongue can detect all 5 taste buds.

How is TASTE processed in the human body?

Taste Buds

epithelial cells located in several areas of the tongue and mouth that detect tastants/taste.

Papillae

A projection most taste buds are associated with. Small raised structures that cover the tongue surface.

The four taste perceptions are sweet, sour, salty, bitter, and umami.

Umami

It translates to "pleasant savory taste" in Japanese and is primarily elicited by the amino acid glutamate. This taste is often associated with foods like meat and aged cheese, where glutamate naturally occurs.

Although receptors and brain pathways for taste and smell are independent, the two senses do interact.

Taste and smell are closely related senses that both rely on chemoreceptors to detect chemicals. While taste involves detecting tastants in solutions, smell involves detecting airborne odorants. These two senses interact significantly; much of the flavor we experience when eating is due to our sense of smell. If the olfactory system is blocked, such as during a cold, our perception of flavor diminishes sharply.

In aquatic animals there is no distinction between taste and smell.

Taste receptors of insects are in sensory hairs located on feet and in mouthparts.

How are taste and smell related to each other?

The four taste perceptions are sweet, sour, salty, bitter, and umami.

What are the 5 tastes humans can detect?

Yes, people do have differences in their ability to taste certain compounds. This variation is largely due to genetic differences in taste receptor proteins. For example, humans have more than 30 different receptors for bitter taste, and each receptor can recognize multiple bitter tastants. This means that some people may find certain foods extremely bitter, while others may not taste the bitterness at all.

A well-known example is the ability to taste phenylthiocarbamide (PTC), a compound that tastes bitter to some people but is tasteless to others. This difference is due to variations in the TAS2R38 gene, which encodes a bitter taste receptor.

Do people have differences in their ability to taste certain compounds?

Olfactory receptor cells are neurons that line the upper portion of the nasal cavity.

Binding of odorant molecules to receptors triggers a signal transduction pathway, generating action potentials.

How is SMELL processed in the human body?

Olfaction (smell)

dependent on the detection of odorant molecules.