Chapter 3 - Biology and Behavior

Cells

The smallest unit of life. Have a membrane and a nucleus

Chromosomes

Structures in the nucleus of the cell body that are made up of DNA; 46 in humans (23 pairs). Transmit genetic material

Genes

Segments of chromosomes that are the basic unit of heredity in all living beings; in the thousands. Transmit genetic material

Genotype

The genetic material we inherit from our parents. Same genetic material is inside the nucleus of every cell of our body

Phenotype

The observable expression of the genotype, including bodily characteristics and behavior

Environment

Every aspect of the individuals and their surroundings (including prenatal experience), other than the genes

Epigenetics

How much a gene is expressed, depending on environment

Regulator genes

Control the activity of other genes

Alleles

Variations of genes. 1/3 of genes have two or more forms

Homozygous

Both alleles for a gene are the same

Heterozygous

The two alleles for a gene are different

Dominant Allele

Determines phenotype whenever it is present in either parent

Recessive allele

Determines phenotype only when it is matched with a similar allele from the other parent

Polygenic

Involves many genes. Most inheritance is this way

Central Nervous System (CNS)

Brain and spinal cord

Peripheral Nervous System (PNS)

All other nerve cells in the body that ARE NOT the brain and spinal cord

Neurons

Process and communicate information - give rise to mental representations. One of the two main types of cells that make up the nervous system

Glial cells (glia)

Protect and nourish the neurons - play mostly supportive role. One of the two main types of cells that make up the nervous system

Dendrite

Detects chemical signals from neighboring neurons

Cell body

Collects and integrates information (contains the nucleus)

Axon

Transmits electrical impulses

Myelin sheath

Encases & insulates long axons. Produced by glia

Terminal boutons

Release chemicals

Synapse

The junction between the terminal boutons of a “sending“ neuron and the dendrites of a “receiving“ neuron - the site at which chemical communication occurs between neurons

Chemical signals

How neurons communicate with each other

Resting membrane potential

Electrical charge of membrane while the neuron is inactive

Action potential

Neural impulse that is generated at the cell body, propagates down the axon, and causes release of chemicals from terminal boutons

All-or-none property

A neuron will either fire an action potential or not (like a gun will either fire a whole bullet or none)

Refractory period

Ensures that APs will only travel in one direction (~2/1000 of a second)

Neurotransmitter (NT)

Chemical substance that carries signals from one neuron to another. Stored in small sacs called vesicles

Receptors

Specialized protein molecules mostly found on dendrites of postsynaptic neurons. Fits like a key in a lock

Step 1 of Chemical Message

Action Potentials (APs) cause neurotransmitter (NT) to be released by the presynaptic neuron

Step 2 of Chemical Message

NT travels across the synapse

Step 3 of Chemical Message

NT molecules bind to specific receptors on the postsynaptic neuron’s dendrites

Step 4 of Chemical Message

NT continues to have an effect until somehow deactivated

Excitatory effect

Postsynaptic neuron more likely to fire an AP

Inhibitory effect

Postsynaptic n. is silenced (blocked from firing AP)

Serotonin

Emotional states and impulsiveness. Plays an important role in our experience of different moods.

Dopamine

Reward and motivation. Plays an important role in our experience of reward and in motor control

Sensory (afferent) neurons

These neurons detect information from the physical world and pass that information to the brain

Motor (efferent) neurons

These neurons direct muscles to contract or relax, thereby producing movement

Other neurons

Most neurons in the CNS are processing and communicating information without a specific sensory or motor function

Spinal Cord

Coordination of some reflexes; carries sensory information to the brain and motor signals away from the brain

Gray matter

Consists of neurons’ cell bodies (aka DNA)

White matter

Consists mostly of axons and the fatty myelin sheaths that surround them

Brainstem

Extension of spinal cord (vital controls)

Cerebellum

Essential for coordinated movement and balance

Cerebral Cortex

The most “human” part of the brain

Occipital lobe

Vision

Temporal lobe

Hearing, memory

Parietal lobe

Touch, spatial relations

Frontal lobe

Thought, planning, movement

Corpus callosum

Connects right and left hemispheres and allows information to flow between them

Somatic nervous system

Transmits sensory and motor signals to and from the central nervous system

Autonomic nervous system (ANS)

regulates body’s internal environment. Carries signals from glands and organs to central nervous system

Sympathetic division

Prepares the body for action (fight or flight)

Parasympathetic division

Returns the body to its resting state (rest and digest)

Plasticity

The capacity of the brain to be modified by experience (or by development)

Neurogenesis

The birth of new neurons

Critical (or sensitive) period

Time during which particular experiences must occur for development to proceed normally