The Chemistry of the Mind of a Dog

Introduction

YouTube Video



Do you ever wonder what your dog is thinking? What’s going through their mind? Do they share the same emotions we do? Though the mind of a dog is not as complex as a human’s, the chemical processes that conjure up these emotions are generally the same. Dogs have all the same brain structures that humans do, meaning they also express the same emotions as us. They feel sadness, joy,excitement, loneliness, and anger just like we do.

I chose to do this project on dogs because dogs are my favorite thing in the whole world. I am also very interested in neuroscience and I wanted to find out if other species’ brains worked the same way as humans. I felt that if dogs and humans can form such a close bond, there must be similarities in the ways we think and feel.


Composition of ...

  • neurons (nerve cells)

    • cell body

      • cytosol - 70% water (H2O) and about 30% Potassium (K) ions

      • nucleus

        • DNA (deoxyribonucleic acid)

          • adenine (C5H5N5)

          • cytosine (C4H5N3O)

          • guanine (C5H5N5O)

          • thymine (C5H6N2O2)

        • RNA

          • adenine (C5H5N5)

          • cytosine (C4H5N3O)

          • guanine (C5H5N5O)

          • uracil (C4H4N2O2)

  • serotonin (C10H12N2O)

  • dopamine (C8H11NO2)

  • norepinephrine (C8H11NO3)

  • synaptic vesicles

10% cholesterol (C27H46O)


Main Chemicals, Compounds, Components

The first main component of the mind of a dog is the sensory system. The sensory system is a group of subsystems (sight, smell, touch, sound, taste) used to detect and understand one’s environment.The sensory system is powered by receptors, which are neurons that receive sensory information and send it to a specific area of the brain. Some different types of receptors are chemoreceptors, mechanoreceptors, electromagnetic receptors, thermoreceptors, and pain receptors. Chemoreceptors detect smell and taste, and then send this information to the somatosensory cortex in the parietal lobe of the brain. Mechanoreceptors detect sound and touch and initiate balance and stretching. They send this information to the auditory cortex in the temporal lobe. Electromagnetic receptors detect visible light, and then send this information to the visual cortex in the occipital lobe. Thermoreceptors detect hot and cold temperatures, and send this information to the somatosensory cortex in the parietal lobe. Pain receptors detect pressure, chemicals, and severe heat. They send this information to the somatosensory cortex in the parietal lobe.

Outside stimuli cause dogs to experience different reactions and emotions. For example, pain inflicted by a human or another dog would stimulate distrust, anger, or fear. Seeing another dog while on a walk would stimulate fear, anger, or curiosity. Being home alone for an extended amount of time would stimulate anxiety. Loss of a close human or fellow pet would stimulate mourning or cause depression. Smelling food would stimulate excitement.


Another main component of the mind of a dog is neurotransmission, or synaptic transmission. When a neuron (a nerve cell that delivers information to and throughout the brain) receives signals from sensory organs, it shares the information with other neurons in the specified area of the brain through neurotransmission (see video for a visual aid). Neurotransmitters (chemicals that deliver information from neuron to neuron) are transported down the axon of the neuron cell to the axon terminal where they are then stored in “packages” called synaptic vesicles. When the synaptic vesicle fuses with the presynaptic membrane it causes the neurotransmitters to spill into the synaptic cleft. The information is shared when the neurotransmitters bind to the receptor proteins in the postsynaptic membrane of the receiving neuron.

Some neurotransmitters implicated in behavior problems are serotonin, dopamine, and norepinephrine. Serotonin is associated with anger, aggression, body temperature, mood, sleep cycles, appetite, and impulse control. A depletion of serotonin can cause aggression or a weakened immune system. Fluctuations in the amount of serotonin being released occur when the dog is hungry, stressed, or sleep deprived. Dopamine is associated with pleasure, focus, mood, learning, memory, and motivation. High levels of dopamine are caused by reward induced motivation, such as a treat, and cause repetitive behaviors that seem to be without purpose. Low levels cause depression, inability to move, or inability to remain motionless. Norepinephrine is associated with alertness, rest cycles, attention, and memory. Low levels can cause depression. Abnormal amounts of neurotransmitters are usually caused by acute or chronic stress.


Chemistry's Role

A dog’s most important sense is their sense of smell. Chemoreceptors are the sensory receptors that detect smell and taste. Dogs can have up to 1.5 billion chemoreceptors in each nasal passage, each one coated in mucous. All odor-producing materials release vapors, and these gaseous molecules dissolve in the mucous and interact with the receptors. There are a few different theories about how odor molecules interact with the receptors. The most widely accepted theory is that chemoreceptors respond to the shape, size, and electronic arrangement of an odor molecule. This response takes place at areas specific to particular combinations of shape and size. Once the odor molecules interact with the chemoreceptors, the chemoreceptors send information on the smell to the olfactory bulb and then the somatosensory cortex (in the parietal lobe), which then causes a reaction through the dog’s behavior, whether it be joy, anger, curiosity, etc.

Neurotransmission occurs when a neuron receives signals from sensory organs and shares the information with other neurons through neurotransmitters in the specified area of the brain. The neurotransmitters are transported down the axon of the neuron cell to the axon terminal where they are then stored in “packages” called synaptic vesicles. synaptic vesicles are madeup of 40% phosphatidylcholine (C42H82NO8P), 32% phosphatidylethanolamine (C7H12NO8PR2), 12% phosphatidylserine (C13H24NO10P), 5% phosphatidylinositol (C47H83O13P), and 10% cholesterol (C27H46O). When the synaptic vesicle fuses with the presynaptic membrane it causes the neurotransmitters to spill into the synaptic cleft. The information on the smell is shared when the neurotransmitters bind to the receptor proteins in the postsynaptic membrane of the receiving neuron.


Background Research

A dog’s brain functions very similarly to a human’s. Dogs can have mental conditions like humans, such as anxiety, depression, and OCD. Though dogs brains are 1/10 the size of humans, their olfactory bulbs (where scent is assimilated) are four times larger than ours. humans, on average, have about 50 million receptor cells in each nasal passage, whereas dogs can have 30 times that amount.

Resources

http://moderndogmagazine.com/articles/which-emotions-do-dogs-actually-experience/32883

dog emotions and thoughts compared to human emotions and thoughts

http://k9aggression.com/medical-issues-overview/brain-chemistry-or-chemical-imbalances/

brain chemistry or chemical imbalances involved in canine aggression

mental conditions

https://k9aggression.com/neurotranmitters-implicated-dog-aggression/

neurotransmitters in a dog’s brain

major neurotransmitters implicated in behavior problems

http://www.macalester.edu/academics/psychology/whathap/ubnrp/meth08/biochemistry/serotonin.htm

information on different types of neurotransmitters

https://faculty.washington.edu/chudler/chnt1.html

http://www.columbia.edu/cu/psychology/courses/1010/mangels/neuro/transmission/transmission.html

synaptic transmission process

visual aid

https://en.wikipedia.org/wiki/Cytosol

chemical structure of cytosol

http://www.ncbi.nlm.nih.gov/books/NBK26821/

chemical structure of DNA

https://answers.yahoo.com/question/index?qid=20090210211116AA3Ewa3

chemical structure of RNA

https://en.wikipedia.org/wiki/Synaptic_vesicle#Composition

full information on the synaptic vesicle

http://study.com/academy/lesson/the-sensory-system-definition-parts-functions.html

http://www.biology-online.org/9/8_sensory_systems.htm

full information on the sensory system and receptors

http://www.responsibledog.net/canine_senses.html

full information on all 5 of dogs’ senses and how they compare to humans’

http://scifun.chem.wisc.edu/chemweek/Odors/chemorec.html

chemoreception: the chemistry of odors

chemical information on odor molecules and how they react with the chemoreceptors inside the nose



About the Author
Addison Wartnow is a junior at Billings Senior High School. She is involved in many activities, such as volleyball, STEM club, Senior Advocates, and orchestra. Addison loves animals and volunteers at her local animal shelter. Once she graduates, she would like to go to school to study pediatrics or sports medicine.
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