How are genes and behavior linked?

Just like fish, who are born with a knack for swimming, humans are born with abilities as well. Each of us has the ability to handle certain situations by basing decisions off of what exists in our native manner. Words that refer to abilities you are born with are innate, or natural abilities. At birth, the human brain is already "programmed" for language, social interaction, self-preservation, and many other functions. We can see this in the interaction between babies and their caregivers. The scientific answer rests on the concept of evolution, which is the process where succeeding generations of organisms change as they adapt to changing environments, as a result of natural selection.

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Evolution and Natural Selection: Charles Darwin introduced the idea of evolution, focusing mostly on organisms who best adapt to their environment over a span of time. Darwin noticed that variations among birds allowed some to survive better. Darwin later called this natural selection. Natural selection, also known as "survival of the fittest", is the idea that individuals that are best suited to their environment are more likely to survive and reproduce than those that do not fit their environment as well. The individuals better suited to their environment live longer than those that aren't as suited to their environment, leaving more opportunity to pass on their favorable traits to future generations. The genes that express the favorable traits eventually come to dominate the population's gene pool. This inheritance helps explain certain psychological phenomenons/behaviors in humans, such as phobias. Most phobias are of something that was a danger warning to our ancestors, such as snakes or blood. The ancestors that had this "phobia", or simply a recognition of its danger, survived more and longer, reproduced more, and thus came to have a larger influence on the gene pool of evolving humans.

Neurons and Nerves: Building the Network

There are two main communication systems in the body, the nervous system and the endocrine system; the brain coordinates them both. The endocrine system has to do with hormones and hormonal glands that pass through the bloodstream. The nervous system has to do with neurons and the signals that shoot through and between neurons.

The basic building blocks of the nervous system are neurons. There are sensory neurons, motor neurons, and inter-neurons. Neurons are made up of dendrites, soma, axon, and terminal buttons (in that order).
Neural firing
Neural firing

Terminal buttons are the ending fragments of a neuron that deliver neurotransmitters across the synapse, or the synaptic gap, to the next neuron's dendrites. These dendrites then fire an electrical signal from the soma, through the axon, then to its terminal buttons to reach the next neuron. When the action potential occurs (meaning the nerve fires) its either completely or not at all, this is called the all or nothing principle. When the neurons aren't firing they are demonstrating resting potential. Neurotransmitters are strikingly similar to hormones, and many hormones act as neurotransmitters. Drugs can alter the transfer of neurotransmitters. Agonists mimic or enhance the effect of neurotransmitters, while antagonists inhibit these functions.

The Central Nervous System: The "Central Processing Unit"

When neurons adapt to physical change or behavioral patterns because of any experiences, they form new connections. This is called plasticity. The nervous system is divided into two main systems: the central nervous system and the peripheral nervous system. The central nervous system consists of the brain and the spinal cord.
The peripheral nervous system is the rest of the nervous system that relays information to and from the brain/spinal cord at the rest of the body. The peripheral nervous system is divided into two main components; the somatic nervous system and the autonomic nervous system. The somatic nervous system has functions similar to those of neurons themselves; sensory (afferent) and motor (efferent). The autonomic nervous system performs "automatically." Its subdivisions are the sympathetic division (arousing) and the parasympathetic division (calming). The endocrine system is the system of hormones and regulators in the body. Hormones are the chemical messengers used by the endocrine system. Hormones are produced in endocrine glands. Many drugs can affect the functions of these hormones and neurotransmitters.

The Structures of the Brain

The brain is composed of many specialized modules that work together to create mind and behavior. In order to understand how the brain functions, scientists have developed several methods of studying the brain. The different tests are EEG, CT, PET, MRI, and fMRI.

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Check out this 3D model of the brain!

The human brain has three layers; the first being the Brain Stem. The brain stem links the spine to the rest of the body; thus, it is an important part of the body's nerve pathways. The brain stem also connects different parts of the brain. The medulla is located in the lower part of the brain stem. The pons is found above the medulla. The brain stem and cerebellum control most of our basic functions. At the center of the brain stem is the reticular formation, which is a bundle of nerve cells that keeps the brain awake and alert. The thalamus is located at the top of the brain stem. Nerve fibers are sent here from the reticular formation. The limbic system is the second layer of the brain. The Limbic System is wrapped around the thalamus and assists in emotion and memories. Inside the limbic system are the Hippocampus, the Amygdala, the Hypothalamus. The brain has no power to act on its own, and therefore, must rely on neural and endocrine communication networks to carry messages to muscles, organs, and glands throughout the body.
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The thinnest, most outer layer of the brain is the Cerebral Cortex ,which has several parts to it. These include the Frontal Lobes, the Parietal Lobes, the Occipital Lobes, and the Temporal lobes. The Corpus Callosum connects the two sides of the brain by a thick bundle of fibers. The brain consists of two hemispheres: the right hemisphere and the left hemisphere. Both of the hemispheres work together to produce thoughts, feelings, and behaviors. Each side of the brain controls and regulates different thought processes. Because each hemisphere has different thought processes, each brain hemisphere has a tendency to exert control over different functions, such as language or perception of spatial relationships. When each hemisphere has dominance over certain behaviors, especially on the opposite side of the body, it is known as Cerebral Dominance.

Some SIMPLE ways to Remember What the Parts of the Brain Do:

  • Medulla = The medulla, as stated above, is in charge of involuntary functions like breathing, heart beat, blood pressure, etc.
  • Pons = Pillows (sleep) and Network (connection of the brain stem to the cerebellum).
  • Reticular Formation = Ready and focused (brain awake and alert).
  • Hippocampus = Hippos have good memories and you go to campus to learn! Hippocampus is responsible for memory and learning.
  • Hypothalamus = Like hunger ... H for hunger... and Hypo like hypoglycemia which is about low blood sugar.
  • Amygdala = A is for anger, and the other A is for afraid. Amy got angry because she didn't like getting scared. It regulates anger, fear, and memory.
  • Frontal Lobes = Think of all the ways we try to move forward in life. Frontal lobes control thinking and movement. Also language and personality.
  • Parietal Lobes = Feeling, touch, and body sensation.
  • Occipital Lobes = (looks like optic, which deals with eyes/vision) optical because it is home to the visual cortex.
  • Temporal Lobes = Hearing, think of temporal along your temples near your ears, or tempo like the beat of music.
  • Cerebellum = Think of a ballerina because the cerebellum controls your coordination and balance. The cerebellum is responsible for coordinated movements.
  • Corpus Callosum = Think of a chain or something that connects one thing to another. The Corpus Callosum relays information from one hemisphere of the brain to the other; Callosum Connects.
  • Thalamus = Relays information coming in from the senses to the part of the brain that interprets that info.
  • Broca's Area = Speech Production. Lacrosse players SAY "bros". BROca's Area involves speech.
  • Wernicke's area= Speech recognition.

Here are some good review things from a Blendspace created by Ms. Woods.

Quick Look bulleted notes of Biopsych from the textbook

Biopsycholo-G by Mr. Wray:

Quizlet Practice: