Chapter 3

Engage in discussions with at least two neighbors on the following topics:
- 1. The significance of your biology to your identity and existence.
- 2. Ponder the question: Without your body, are you truly yourself?
- 3. Explore the relationship between the first two questions and psychology.

Genetics: The scientific study of heredity and the variations in inherited characteristics.
- Composed of 46 chromosomes (23 pairs) which are long strings of DNA (deoxyribonucleic acid).
- Genes: Specific sequences of DNA that code for traits.
- Allele: A distinct version of a gene.
- Genotype: The genetic makeup of an individual, represented as combinations of alleles.
- Phenotype: The observable physical characteristics resulting from the genotype.
- Mutation: A sudden and permanent alteration in a gene.

Free earlobes (E) vs. Attached earlobes (e):
- Dominant allele: E (free earlobes).
- Recessive allele: e (attached earlobes).
- Homozygous: Having two identical alleles (EE or ee).
- Heterozygous: Having one of each allele (Ee), which is a carrier for the recessive trait.
- Example Punnett Square:
- Parent 1 (Ee) x Parent 2 (Ee) results in:
  - EE, Ee, Ee, ee.

Natural Selection: A process in which organisms that are better suited to their environment tend to survive and reproduce, passing on their genetic attributes.
Example: Sickle-cell anemia and its prevalence in people of African descent.
- Carriers (genotype Aa) exhibit immunity to malaria, which provides a health advantage in malaria-prone regions.
- Differences in prevalence of carriers can be noted between populations in North America vs. Africa.

Expression of Genes: A two-pronged approach discussing how, when, and in what combination our genes manifest in our characteristics.
- Range of Reaction: Genetic predispositions establish potential boundaries of development; the environment determines the realized position within that range.
- Genetic Environmental Correlation: Suggests that our genes not only influence our environment but that our environment can also affect gene expression.

Studies why the same genotype can lead to differing phenotypes under various conditions.
Twin Studies: Assess the likelihood of identical vs. fraternal twins sharing traits, thereby providing insights into genetic vs. environmental influences.
Adoption Studies: Examine the correlation of traits between biological relatives and adopted individuals, leading to further understanding of genetic factors in behavior.

Two main types of cells:
- Glial Cells: Support and maintenance providers for neurons. They:
- Facilitate neuronal connections for effective communication.
- Insulate neurons from one another.
- Transport nutrients and waste products.
- Mediate immune responses in the central nervous system.
- Neurons: Complex information processors connected to the body's electrochemical signaling system, forming the foundation for all communication within the body.
- Essential for all behaviors, thoughts, and emotions.

Dendrite: Receives input signals.
Soma: The cell body housing the nucleus and cellular machinery.
Axon: The elongated structure transmitting signals; includes:
- Myelin Sheath: Acts as insulation around the axon.
- Terminal Buttons: Contain chemical messengers known as neurotransmitters.

Synaptic Gap (Synapse): The minuscule space between two neurons where communication occurs.
Receptors: Particular proteins located on the cell surface that receive neurotransmitters.

Signals travel through the neuron and jump across the synapse to adjacent neurons.
- Membrane Potential: Refers to the charge difference across the neuronal membrane, essential for propagating signals.
- Key players in the action potential include sodium (Na+) and potassium (K+).

The neuron at rest is characterized by a net negative charge internally, facilitated by the action of the sodium-potassium pump (3 Na+ ions expelled from the cell for every 2 K+ ions imported).
Upon stimulation, Na+ channels open, leading to an influx of Na+ ions and making the interior of the cell more positive.
Threshold of Excitation: The critical point of depolarization needed to trigger an action potential.

An electrical impulse moves from the cell body through the axon to the axon terminals.
Triggered by a substantial influx of Na+ ions; follows an all-or-none principle in the conduction of the signal.

Neurotransmitters: Naturally occurring chemicals facilitating communication between neurons.
Agonist: Mimics the action of neurotransmitters; example seen in Parkinson's disease due to low dopamine levels.
Antagonist: Blocks or impedes neurotransmitter action; associated with schizophrenia and elevated dopamine levels.
Reuptake Inhibitors: Prevent the reabsorption of neurotransmitters, relevant in antidepressant treatments (e.g., for low serotonin levels).

Neurotransmitter	Involved In	Potential Effect on Behavior
Acetylcholine	Muscle action, memory	Increased arousal, enhanced cognition
Beta-endorphin	Pain, pleasure	Decreased anxiety, decreased tension
Dopamine	Mood, sleep, learning	Increased pleasure, suppressed appetite
Gamma-aminobutyric acid (GABA)	Brain function, sleep	Decreased anxiety, decreased tension
Glutamate	Memory, learning	Increased learning, enhanced memory
Norepinephrine	Heart, intestines, alertness	Increased arousal, suppressed appetite
Serotonin	Mood, sleep	Modulated mood, suppressed appetite

Central Nervous System (CNS):
- Comprises the brain and spinal cord; functions as the command center of the body.
Peripheral Nervous System (PNS):
- Encompasses all nerves located outside the CNS; divided into:
- Somatic Nervous System:
  - Involved in voluntary control and conscious awareness.
  - Motor Neurons: Carry commands from the CNS to muscles (Efferent pathways).
  - Sensory Neurons: Relay sensory information to the CNS (Afferent pathways).
- Autonomic Nervous System (ANS):
  - Operates involuntarily, influencing organs and glands.
  - Subdivided into:
  - Sympathetic Nervous System: Facilitates the fight-or-flight response.
  - Parasympathetic Nervous System: Promotes homeostasis and relaxation.

Upcoming topics will cover Chapter 3.4-3.5, focusing on Biopsychology, particularly the brain and spinal cord and the endocrine system.
Students are encouraged to consider the functions and roles of the various parts of the brain as preparation for the next class.