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OHIO / Biological Sciences / BIOS 1710 / How molecules/odorants bind to their receptors?

How molecules/odorants bind to their receptors?

How molecules/odorants bind to their receptors?


School: Ohio University
Department: Biological Sciences
Course: Biological Sciences II: Ecology, Evolution, Animal Body Systems
Professor: Scott moody
Term: Fall 2017
Tags: sensory-systems, transduction, smell, TAST, eyes, EAR, and brain
Cost: 25
Name: BIOS 1710: Biological Sciences II, Week 2 Notes
Description: Notes covered for chapter 36 from lecture and book. Againg What we went over for ch 37 will be on next weeks notes. If you have any questions feel free to email me: sj026514@ohio.edu
Uploaded: 09/02/2016
10 Pages 133 Views 1 Unlocks

Week 2

How molecules/odorants bind to their receptors?

Aug 29-Sept 2

Ch 36

Sensory Systems

Receptors- what allows us to sense the physical properties of the environment

Receptors  protein  

How is action potential is sent up the axon to the glomeruli in the olfactory bulb?

Sensory Recepors  

What are the types of eye structures?

If you want to learn more check out Why do rights require positive action?

neruon Sensory Organs

Sensory Transduction- conversion of physical or chemical stimuli into nerve  impulses

Types of Sensory Receptors: If you want to learn more check out Why material of capacity doesn't matter?

• Chemoreceptors- perceive specific molecules  

• Mechanoreceptors- respond to touch or pressure

• Thermoreceptors- detect temperature changes

• Nociceptors- sense pain or harmful stimuli

• Photoreceptors- respond to wavelength of light

• Electroreceptors detect electrical fields  

Effective Transduction 

Strength of signal  

- Intensity is not based on size of action potential but firing rate Firing rate- number of action potential fired over a period of time (spatial/temporal  summation)

Low intensity ???? low firing rate


We also discuss several other topics like Who are the earliest teachers of public speaking in ancient greece?

High intensity ???? high firing rate

If you want to learn more check out Why use depositions?

Continuous Stimuli

- Allows us to ignore background ‘noise’ by adaptation

Adaptation- receptors reducing their firing rate  Don't forget about the age old question of What is a conflicts between a state and a non- state armed group outside that state’s territory?

Locating the signal

Lateral Inhibition- enhances the strength of a sensory signal locally but diminish it  peripherally




• -Humans (and most mammals) have nearly 1,000 genes for expression  olfactory receptors ???? Meaning 5% of our genes are  

for smell

o each neuron has one type of receptor Don't forget about the age old question of Why study the oceans?

o half (in humans) do not work because of  


• receptors are coupled with G-proteins (molecular  

switches) which activate cAMP to open K and Na  



1. Molecules/odorants bind to their receptors  

2. Action potential is sent up the axon to the glomeruli in  

the olfactory bulb

3. Sent to interneurons  

4. Integrate information then sent to brain  

Olfactory Bulb


Gustation- Taste 

• Each taste bud ahs 100 taste cell and a 10 day life span

• Humans have about 10,000 taste buds

5 basic tastes:

1. Sweet: they think there are 3 different receptors  

2. Sour: protons; controlled by pH, lower pH= more sour

3. Bitter: 40-80 genes

4. Salty: from Na entering the channel creating action potential 5. Savory

Sensing Gravity, Movement, and Sound 

Hair Cells- sense movement and vibration

-When a pressure wave bends sterocillia it opens K channels

Lateral Line System- where hair cells are in sharks and fish to  

detect motion and things nearby

Gravity Sensing Organs

Statocysts- organ found in most invertebrates; internal chamber  lined by hair cells that project into the chamber  

Statolith- free to move around in the statocysts and propelled by  gravity; when pressed up against hair cells it locates direction of  gravity  

The Ear 

Hearing- ability to sense sound, which consists of waves of  

pressure in air or water

Frequency- difference in pitch

Humans- 20 Hz- 2,000Hz

Dogs- up to 44,000 Hz

Elephants- 1Hz

Amplitude- determines loudness  

Important parts of the ear:

• Pinna- enhances the reception of sound waves; outer ear

• Tympanic Membrane (eardrum)- transmits sound into the ear; outer ear • Malleus, Incus, and Stapes- amplifies the waves; bones; middle ear • Oval Window- then membrane; attached the stapes and part of the cochlea,  inner ear

• Cochlea- a coiled chamber; contains hair cells; means snail in Latin; inner ear

Vestibular System- organs that make up the  

inner ear

-provide a sense of gravity and body  


- has hair cells

-sense angular motions of the head in three  

perpendicular planes (Allows us to hold a gaze  

while in movement)

Process of hearing:

1. Outer ear pushes pressure waves into the ear canal and tympanic membrane  at the same frequency  

2. Amplified (30x) by the 3 bones of the middle ear

3. Vibrates against the oval window  

4. Oval window generates the waves to the fluid of the cochlea where  transduction takes place

5. Hair cells sense the waves

The Cochlea

-Contains the organ or corti  

- Has hari cells that are supported by the basilar membrane on the bottom (can  move)

Visual of Cochlea ‘rolled out’ with pressure waves

Narrow- stiff and responds to high  

frequencies; 20,000 Hz

These die off first

Wide- flexible and responds to low  


YouTube video of cochlea animation  



Conduction  Deafness- loss  of function of  the tympanic  membrane or  ossicles of the  

middle ear;  ossicles stiffen  with age  causing loss of  ability ot hear  high frequency  sounds

Nerve  Deafness caused by  inner ear or  auditory  pathway  damage, including damage to hair cells  


Electromagnetic Receptors- respond to electrical, magnetic, and light stimuli **Light-detecting photoreceptors are the most common and diverse Types of Eye Structures 

1. Eyecups

a. Flatworms have two on the dorsal surface  

b. Detect the direction ad intensity or light sources  

c. Pigmented epithelium blocks light so light is only received from above  and in front  

2. Compound eye

a. Insects and crustaceans

b. Some can see ultraviolet light

c. Ommatidia- light-focusing, number in eye determines the resolution i. In a single ommatidia light is focused through a lens onto  

overlapping photoreceptors

ii. Sensitive to about 1°-2° of light in visual field  

3. Single-lens Eye

a. Vertebrates and cephalopod mollusks

b. Work like a camera

c. Focus light rays on a particular region of photoreceptors

d. Can detect objects by motion and shape

e. Some spiders have this

Anatomy of the Human Eye 

Sclera- tough, white outer layer, covers the  

eye, mucus production to keep the eye  


Choroid- carries blood vessels for  


Cornea- front of the eye, part of the sclera,  


Pupil- light enters through this opening

Convex Lens- light passes through ???? close object= rounded, distant object= relaxed  and flatten  

*If this becomes cloudy you get cataracts  

Ciliary Muscles- attached between sclera and lens, contraction/relation adjusts the  lens to focus image

Iris- opens and closes to adjust the amount of light, surrounds the pupil, gives eye  color

Aqueous Humor- interior region in front of lens, filled with clear water liquid that is  produced and drained constantly by small ducts at base of eye ???? blockage can  increase pressure and can cause glaucoma possible blindness  

Vitreous Humor- large cavity behind lens, filled with a gel-like substance, makes up  most of the eye’s volume  

Retina- initially process light stimuli thin tissue, contains photoreceptors, cornea and lens bend light and focuses them here, light rays cross: flip image up to down  and left to right

Why do we have two eyes??

For binocular vision allowing for depth and distance perception  *ability to combine images form both eyes to produce one image  Detecting Light 

Opsin- photosensitive protein, converts light energy into electrical signals,  cylindrical groups in the plasma membrane of most photosensitive cells Retinal- derivative of vitamin A, absorbs light

Rhodopsin- transmembrane protein found photosensitive cells of vertebrates,  covalently bout to retinal  

-Photosensitive cells are modified neurons with leaky Na channels -Resting membrane potential (in the dark) is less negative about 34mV


1. Retinal absorbs light photo

2. Conformational change from sis to trans configuration  

3. Causes Na channels to close

4. Cell membrane becomes hyperpolarized and neurotransmitter release is  reduced

-Photoreceptors do not fire action potential but inhibit the fire rate of other neurons in the eye when stimulated by light energy ???? provides information about the  intensity and pattern of light received  

***In summery: when light photons hit a receptor it closes the Na channel NOT  opens it; usually it is a ‘dark current’ for depolarization  

Color Vision 

-by photoreceptor cells that contain visual pigments  sensitive to different  wavelength of lights

- Rods and cones have disks where opsin is

Cone Cells- color-sensitive pigments, provide the sharpest vision, 6 million  -Absorb light at blue (short), green (medium), or red (long) wavelengths -Color-blind people lack function in green and/or red cones

* this is a sex linked gene their for it is more common in males  

Rod Cells- allow animals to see in low light more than cone cells, sensitive to light,  detect shades from white to black, found periphery of the eye to detect motion in the  periphery at night, 125 million

**Rod and cone cells make up about 70% of all sensory receptors cells in the human  body

Why is it harder to see color at night?

Cone cells have a low sensitivity to light

Fovea- cone cells are most concentrated here, no rod cells, center of the visual field Color in Animals: 

-Depends on number of cones and particular opsin

-Nocturnal animals have few cones but many rods

-Some deep see fish have two opsin for blue

-Birds, insect, and some mammals can see ultraviolet light

-Rattlesnakes and pit vipers and infrared light to detect prey in the dark  Cellular Organization 

-retina consist of five layers of neurons  


1. Rods and cones synapse on to bipolar cells- do  

not fire action potential, adjust their release of  


2. Bipolar cells synapse onto ganglion cells 

located on the front of the retina

3. If activated transmits action potential by the  

*optic nerve to the visual cortex

*begins at the front of the retina and  

exits at the back; creates an area with  

out light-sensitive cells (Blind Spot)

Horizontal Cells- communicate between neighboring  

airs of photoreceptors and bipolar cells  ???? enhances  

contrast  to sharpen the image

Amacrine Cells- communicate between neighboring  

bipolar cells and ganglion cells ???? enhancing motion  

detection and adjusting for changes in illumination of  


Functional Studies of the Brain

Brain Mapping  

• Electrical stimulation  

o You do not have pain receptors in the brain so you can have an awake  brain surgery  

o They would stimulate parts of the brain and see what the reaction  would be

• fMRI

• Lesion Studies

o Broca’s Patient

✂ Found that the frontal area is where language was used

✂ Broca’s Area of the brain  

o HM

✂ Had sever epilepsy  

✂ Removed the hippocampus  

✂ When doing so he was no longer able to retain new memories o Phineas Gage

✂ Had a work related accident that ended with a pipe through his  skull in the frontal lobe  

✂ He survived but had impulse control and anger issues  

The Brain

Major Regions 

1. Forebrain

a. Cerebral Cortex

b. Thalamus

c. Hypothalamus

2. Midbrain

a. Part of the brain stem

3. Hindbrain

a. Pons  

b. Medulla (part of the brainstem  

c. Cerebellum

**Basic body functions and behaviors- hindbrain and midbrain

   Advanced cognitive functions- forebrain, particularly cerebral cortex ???? much  larger in mammals, especially humans


Cerebellum- coordinates complex motor patters

Brain Stem- autonomic center  

Thalamus- relays sensory information to the  


Hypothalamus-controls homeostasis and releases  


Cerebrum- cerebral cortex is the thin outer layer,  

bulk of the brain, divided into life and right  

hemispheres (each having 4 lobes) by a thick band of  

axons called the corpus callosum, involved in  

conscious thought and memory  

Limbic System-  Part of the forebrain (medial  

temporal lobe);  involved in drives, emotion,  

memory formation

Hippocampus- part of the limbic system; long-term memory

Amygdala- part of the limbic system, controls fear (fight or flight response) Four Lobes of the Brain 

- cerebral hemispheres are the larges structures of the mammalian brain and  consists of a highly folded outer layer of gray matter (4mm thick) called the cortex

Why is the cortex folded?

To increase surface area to increase amount of neurons

- Under the cortex is a white matter (myelinated axons)  

Sulcus- clear deep crevices that define the different lobes

Frontal lobe- anterior region of the cerebral cortex;  

decision making, planning, emotional control, personality  

Parental lobe- two of them; posterior to the frontal lobe  

and separated by the central sulcus; body awareness

(touch and temperature) and ability to preform complex


Temporal lobe- on the side below the parietal lobes;  

process sound, memory, and understanding speech

Occipital lobe- behind the parietal lobe in the back of the  

brain; processes visual information from the eyes

Primary Motor Cortex- part of the frontal lobe, ‘command’  

neurons produce complex coordinated behaviors by  

controlling skeletal muscle movements

Primary Somatosensory Cortex- part of the parietal lobe, integrates tactile  information from specific body regions and sends it to the motor cortex ** both motor and somatosensory cortices makes connections to the opposite side  of the body by sending axons that cross over in the brainstem and spinal cord ???? right cortex controls the left side of the body and vice versa  

Topographic Maps 

- Brain mapping for part of the brain

-Larger the body part on map the more space  

dedicated with axons

Other types:

• Auditory cortex- by pitch

• Understanding language in left temporal  

lobe (Wernicke’s Area)

• Speaking Language in left frontal lobe  

(Broca’s Area)

• Spatial visualization and analysis on the  

right side

• Occipital lobe maps visual information

maintained in midbrain centers and cortex


The primary cortical area where the sensation of touch is processed in the  1. Occipital  

2. Temporal  

3. Parietal  

4. Frontal  

Correct Answer: 3

Learning and Memory

Cognition- ability to process and integrate complex source of information, interpret  and remember past events, solve problems, reason, and from ideas Learning- enduring, adaptive change in behavior

Memory- retention of learned information  

How: the hippocampus transforms reinforced short-term memories into long-term  memories by respectively relaying information to regions of the cerebral cortex - Learning and memory involve long or short term structural/chemical  changes at the synapses

- Long-term memory involves change in gene expression

Synaptic Plasticity- ability to adjust synaptic connections; LTP

- Repeated release of a neurotransmitters stimulates the production of new  receptors and dendrites  

Long-term Potentiation (LTP)-induced by high frequency stimulation - Discovered in the hippocampus

- Best model for how learning and memory work

- Found at synapses where glutamate is

- Glutamate binds to NMDA and AMPA receptors

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