Psychology Unit 1A — Study Guide Definitions

1. Heredity (Nature)

Traits and characteristics inherited from your parents through genes.

2. Environment (Nurture)

The people, experiences, and surroundings that influence your development.

3. Dizygotic/Fraternal Twins

Twins who develop from two separate eggs and share about 50% of their DNA, like regular siblings.

4. Monozygotic/Identical Twins

Twins who develop when one fertilized egg splits into two and share nearly all their DNA.

5. Evolutionary Psychology

The study of how behaviors and mental processes developed through evolution.

6. Behavioral Genetics

The study of how genes and the environment influence behavior.

7. Natural Selection

The process where traits that help organisms survive and reproduce become more common over generations.

8. Epigenetics

The study of how environmental factors affect whether genes are turned on or off without changing the DNA sequence.

9. Eugenics

The discredited belief that humans can be improved by controlling who reproduces.

10. Heritability

A measure of how much genetic differences explain differences in a trait within a population.

11. Endocrine System

A system of glands that release hormones into the bloodstream.

12. Hormones

Chemical messengers that travel through the blood and affect body functions and behavior.

13. Pituitary Gland

A gland that releases hormones and helps control other endocrine glands.

14. Adrenaline

A hormone that prepares the body to respond to danger or stress.

15. Leptin

A hormone that signals fullness and helps regulate energy storage.

16. Ghrelin

A hormone that signals hunger and increases appetite.

17. Melatonin

A hormone that helps regulate the sleep-wake cycle.

18. Oxytocin

A hormone involved in bonding, childbirth, and breastfeeding.

19. Central Nervous System

The brain and spinal cord, which process information and coordinate responses.

20. Peripheral Nervous System

All the nerves outside the brain and spinal cord that connect them to the rest of the body.

21. Somatic Nervous System

The part of the nervous system that controls voluntary movements and carries sensory information.

22. Autonomic Nervous System

The part of the nervous system that controls automatic body functions, such as heartbeat and digestion.

23. Sympathetic Nervous System

Activates the fight-or-flight response during stress or danger.

24. Parasympathetic Nervous System

Helps the body rest, recover, and digest food.

25. Neurons

Nerve cells that receive and transmit information.

26. Sensory Neurons

Carry information from the senses toward the brain and spinal cord.

27. Motor Neurons

Carry commands from the brain and spinal cord to muscles and glands.

28. Interneurons

Connect neurons and process information within the brain and spinal cord.

29. Glial Cells

Cells that support, protect, and nourish neurons.

30. Dendrites

Receive messages from other neurons.

31. Soma (Cell Body)

Contains the nucleus and keeps the neuron functioning.

32. Axon

Carries electrical signals away from the cell body.

33. Myelin Sheath

A fatty covering around some axons that helps signals travel faster.

34. Terminal Branches/Buttons

The ends of a neuron that release neurotransmitters.

35. Receptor Sites

Places on a cell where specific neurotransmitters bind.

36. Synapses/Synaptic Gap

The tiny space between neurons where chemical messages travel from one cell to another.

37. All-or-Nothing Principle (AKA Response)

A neuron fires a complete action potential if the threshold is reached, or it does not fire.

38. Resting Potential

The electrical charge difference across a neuron's membrane when it is not firing.

39. Depolarization

A change in electrical charge that makes the inside of a neuron less negative.

40. Threshold

The minimum stimulation needed to trigger an action potential.

41. Action Potential

A brief electrical signal that travels down the axon.

42. Refractory Period

A short period after firing when a neuron resets before it can fire normally again.

43. Reuptake

The process in which the sending neuron takes neurotransmitters back in after releasing them.

44. Agonist (AKA Reuptake Inhibitor)

An agonist increases a neurotransmitter's effect. A reuptake inhibitor blocks its reabsorption, allowing it to remain in the synapse longer.

45. Antagonist

A substance that blocks or reduces a neurotransmitter's effect.

46. Spinal Reflexes/Reflex Arc

A rapid, automatic response to a stimulus that can occur through the spinal cord before the brain fully processes it.

47. Long-Term Potentiation (LTP)

A long-lasting strengthening of connections between neurons that helps with learning and memory.