PSYC 1200 - Chapter 3

Heredity

Heredity

The biological process responsible for passing on traits from one generation to another

Genes

Guide the process of creating proteins (building blocks) that make up our physical structures and regulate development and physiological processes

Genes contain info for making specific molecules/proteins that allow human cells to function and control how the body grows and operates.

Made up of segments of DNA.

Genotype

Genetic makeup of an organism

The unique set of genes that comprise that individuals genetic code

Example: Genetic material passed between generations

Phenotype

The physical traits and behavioural characteristics expressed

Show genetic variation.

Observable characteristics

Example: Eye colour, facial features, height

Behavioural Genomics

Study of DNA and how specific genes are related to behaviour.

How genes influence behaviour.

Behavioural Genetics

How genes and the environment influence behaviour.

How genes and the environment work together to influence personality.

Example: Gene for cancer doesn’t always mean you will get cancer.

Behavioural Genetics Twin Study

Monozygotic Twins: came from 1 egg, approximately 100% genetically identical.

Dizygotic (Fraternal) Twins: come from 2 eggs, fertilized by 2 different sperm cells, approximately 50% genes in common, same as regular siblings.

Individuals that are more genetically related will be more similar if that trait is mostly genetically determined.

If behaviour is environmentally determined, then people who grew up in different houses may not be similar.

Adoption Studies

If behaviour of children is more like their adoptive parents, then that behaviour is likely more environmentally determined.

If behaviour of children is more like their biological parents, then that behaviour is likely more genetically determined.

Heritability

How much the genetic differences between individuals contribute to differences in behaviour, or specific traits within a population

Tells us how genes explain the differences in the expression of a trait (within a population), but it doesn’t tell us how genes contribute to the trait itself.

Genes are either…

Active (expressed): Contribute to the production if proteins.

Inactive (not expressed): Don’t contributes to the production of proteins.

Specific gene expression/activation is influenced by genetics, and environmental factors.

Epigenetics

How experiences cause changes in gene expression without altering genetic code.

CRISPR-Cas9

Technique that allows genetic material to be removed, added, or altered in specific locations of a genome.

Natural Selection

Favourable (useful for survival) traits become increasingly common in a population of interbreeding individuals, while unfavourable traits (less useful for survival) become less common.

Evolution

Change in the frequency of genes occurring in an interbreeding population over generations.

Not a continuous process

Never “finished”

Evolutionary Psychology

Attempts to explain human behaviours based on the beneficial function(s) that may have served our species development.

Example: Homo Sapiens: Planning, problem solving, direct attentional focus, communication (symbolic representation)

Nervous System

A system of nerves (bundle of neurons) involved in the coordination of behaviour.

Central Nervous System

Brain and spinal cord

Peripheral Nervous System

Nerve connections throughout the body

Neurons

Type of cell found in the nervous system

Responsible for sending and receiving messages throughout the body.

Neuron Structure

Cell body, dendrites, axon, myelin, axon terminals

Cell Body (Soma)

Contains the nucleus that houses the cells genetic material.

Dendrites

Small branches attached to the cell body that receive messages from other cells.

Axon

Transports information in the form of electrochemical reactions from the cell body.

Myelin

Coats and insulates the axon as the messages are sent down (more effective transmission because it prevents the electrochemical signals from dissipating)

Axon Terminals

Bulb-like extensions at the end of the axon. Filled with vesicles containing neurotransmitters.

Types of Neurons

Sensory neurons, motor neurons, interneurons

Sensory Neurons

Send sensory information to the brain (touch, hear, see, smell, taste).

Motor Neurons

Send signals from brain to move muscles.

Interneurons

Communication between neurons

Important for reflexes (example: if you touch something hot and need to move your hand)

Neurogenesis

Formation of new neurons

Neuroplasticity

The process by which the brain changes and rewires itself bases on experience

Neuron Electrical System

Resting State (Resting Potential):

Relatively stable state during which the cell is not transmitting messages. Higher concentration of positively charged ions outside of the neuron. Results in a negative net charge inside the axon compared to the outside.

Ions like to be evenly distributed. They move from areas of high concentration to low concentration.

Ion Channels: small pores on the neuron’s cell membrane. Allow ions to pass through neuron.

What happens when a neuron is stimulated

Ion channels open (begins at base of axon)

Positive ions move into the cell, changing the charge of the neuron to positive (negative to positive)

If the positive charge reaches the firing threshold, it will create an action potential.

Action Potential

Wave of electrical activity starting at the beginning of the axon (near cell body) and rapidly travels down the length of the axon.

After the cell has fired, the positively charged ion are channelled back out and the neuron returns to resting state.

After Action Potential

Ion channel closes, allowing a return to resting state.

The cell is now hyperpolarized, more negative than its original resting potential.

Refractory period: Neuron cannot fire until it returns to original resting potential.

When the action potential reaches the axon terminal, neurotransmitters are released into the synapse.

Synapse

The area involving one neuron’s axon terminal, and another neuron’s dendrites.

Separated by a tiny space called the synaptic cleft.

Presynaptic Cell

Neuron that releases its neurotransmitters.

Postsynaptic Cell

Neuron that receives neurotransmitters from presynaptic cell.

Neurotransmitters from the presynaptic neuron will influence the charge of the postsynaptic neuron.

Excitatory Neurotransmitter

Increases the likelihood of an action potential for that neuron

Inhibitory Neurotransmitter

Decreases the likelihood of an action potential for that neuron

Each neurotransmitter fits into a particular post synaptic receptor

What happens when neurotransmitters are released back into synapse

They are either broken down by enzymes or reuptake.

Reuptake

Process where neurotransmitter molecules are reabsorbed into the axon terminals or the presynaptic neuron

Peripheral Nervous System

Transmits signals between the brain and the rets of the body.

Divided into two subcomponents:

Somatic and Autonomic

Somatic System

Nerves that control skeletal muscles responsible for voluntary and reflexive movements.

Nerves that receive sensory input from the body

Autonomic System

Unconscious control of glands and bodily organs (heartrate, body sweat).

Two subcomponents:   

Sympathetic, and Parasympathetic           

Sympathetic

Control of responses that prepare the body for action (fight or flight)

Example: Increased blood flow/heartrate signals sent to skeletal muscles to prep for movement.

Parasympathetic

Maintains homeostasis balance.

Returns body to non-emergency state.

The two cerebral hemispheres

Left and right hemisphere

Corpus Callosum

Neutral fibres connecting the two hemispheres.

Hindbrain

Contains structures critical for basic life sustaining processes

Brainstem

Bottom of brain. Sends signals from brain to the rest of body.

Medulla, and Pons

Medulla

Regulation of breathing, heart rate, etc. (minimal conscious control)

Pons

Handles unconscious processes and jobs such as sleep-wake cycle (wakefulness)

Cerebellum

Coordination and timing of movement, maintaining balance, attention, and emotional responses.

Midbrain

Relay station between sensory and motor areas

Superior Colliculus

Orientating visual attention.

Inferior Colliculus

Orientating auditory attention.

Forebrain

Everything above the midbrain

Many interconnected structures critical to processing emotion, memory, thinking, and reasoning.

Basal Ganglia

Manage the signals your brain sends to help you move your muscles

Responsible primarily for motor control

Amygdala

Facilitates memory formation for emotional events

Mediates fear responses.

Recognizing and interpreting emotional stimuli

Hippocampus

Involved in long term memory formation.

Learning and the formation of new memories

Hippothalamus

Homeostasis (temp, hunger, thirst, sex)

Thalamus

Relays incoming sensory information to different brain regions

Cerebral Cortex

Wrinkled outer layer of the brain (wrinkles = more surface area)

Involved in higher functions such as thought, language, and personality.

Consists mostly of cell bodies and dendrites (grey matter)

These neurons’ axons spread to different brain regions (white matter)

Lesioning the Brain (Morris Water Maze)

Used to measure spatial learning and navigation in rats.

Transcranial Magnetic Stimulation (TMS)

Application of an electromagnetic pulse to a targeted region of the brain

The pulse typically disrupts the natural brain activity at that region (disrupts the flow of ions around the brain)

Induces a temporary lesion.

Can also be used to stimulate the targeted brain region (by applying a weaker pulse) and increase activity at this location.

Structural Neuroimaging Examples

Computerized tomography (CT scan)

Magnetic Resonance Imaging (MRI)

Diffusion Tensor Imaging (DTI)

Computerized Tomography (CT scan)

X-rays are sent through the brain by a tube that rotates around the head.

Rays pass through different tissues at different rates because some tissues are denser than others.

Images show differences in tissue density (grey matter vs. white matter vs. ventricles)

Pictures taken at different positions reconstructed to create 3-D image.

Magnetic Resonance Imaging (MRI)

Creates clear images of the brain based on how different regions absorb and release energy while in a magnetic field.

Diffusion Tensor Imaging (DTI)

Measures white matter pathways (axons) in the brain.

Functional Neuroimaging

A type of brain scanning that provides information about activity in the brain during a particular behaviour or in response to a stimulus.

Potential trade-off between two components of functional neuroimaging temporal resolution and spatial resolution.

Temporal Resolution

How small/accurate a time period can be measured. How long you must wait for the scan to come through.

Spatial Resolution

How clear the image of the brain is?

Functional Neuroimaging Examples

Electroencephalography (EEG)

Magnetoencephalography (MEG)

Position Emission Tomography (PET)

Functional Magnetic Resonance Imaging (fMRI)

Electroencephalography (EEG)

Measures patterns of the brain activity (neuronal firing) using multiple electrodes attached to the scalp.

Measures brain activity every millisecond (excellent temporal resolution)

Limited spatial resolution (less effective at locating region of the brain).

Magnetoencephalography (MEG)

Measures tiny magnetic fields created by the electrical activity of nerve cells in the brain.

Also measures brain activity every millisecond (excellent temporal resolution).

Slightly better at locating brain activity, but still not great special resolution.

Position Emission Tomography (PET)

A radioactive substance is injected into the blood, and it travels to regions of the brain engaged in a particular task and is measured.

Increased blood flow (carrying oxygen) to brain regions that are more active (higher radioactivity will be measured in brain regions that are more active)

Radiotracers allow for the measurement of certain neurotransmitters receptors.

Good spacial resolution but bad temporal resolution (> 2 mins).

Functional Magnetic Resonance Imaging (fMRI)

Measures the amount of oxygen rich blood flow in active brain regions.

This is called BOLD (blood oxygen level dependant) response.

Not great temporal resolution (approximately 2s).