SciOly Prep- Life Science
1. Nervous System
a. Brain Regions & Functions
The cerebrum is responsible for thinking and sensory/motor functions.
The cerebellum controls coordination and balance.
The brainstem manages vital functions.
The limbic system is involved in emotion and memory.
b. Neural Impulses
Neuron anatomy includes structures like myelin and Schwann cells/oligodendrocytes.
An action potential is generated by the influx of sodium (Na+) and efflux of potassium (K+).
Neurotransmitters such as acetylcholine (ACh), dopamine, serotonin, and GABA are involved in neural communication.
c. Synapses
Synapses can be electrical or chemical.
They can also be excitatory or inhibitory.
Summation refers to the combined effect of multiple synaptic inputs.
d. Central Nervous System (CNS)
The CNS includes the spinal cord and cranial nerves (I–XII).
The CNS is also involved in sleep regulation.
e. Peripheral Nervous System (PNS)
The PNS consists of sensory neurons (carrying information to the CNS) and motor neurons (carrying information from the CNS).
Motor neurons are further divided into the somatic (voluntary control) and autonomic (involuntary control) nervous systems.
The autonomic nervous system includes the sympathetic (fight/flight) and parasympathetic (rest/digest) divisions.
Reflex arcs and proprioception (sense of body position) are also part of the PNS.
f. Nervous System Disorders
Common disorders include epilepsy, Alzheimer’s, Parkinson’s, Multiple Sclerosis (MS), Cerebral Palsy (CP), Amyotrophic Lateral Sclerosis (ALS), shingles, and stroke.
g. Drug Effects on the Nervous System
Alcohol acts as a depressant.
Caffeine is a stimulant that blocks adenosine receptors.
Nicotine stimulates acetylcholine receptors.
Marijuana acts as a CB1/CB2 receptor agonist.
h. Electroencephalograms (EEGs)
Alpha waves are associated with relaxation.
Beta waves indicate an alert state.
Delta waves are seen in deep sleep.
Theta waves are associated with light sleep or meditation.
2. Endocrine System
a. Hormone Classes
Steroid hormones are lipid-soluble and bind to nuclear receptors.
Peptide hormones are protein-based and bind to membrane receptors.
Amine hormones are derived from tyrosine, such as epinephrine and thyroxine.
b. Hormone Mechanisms
Nuclear mechanisms involve changes in gene transcription.
Cytoplasmic/membrane mechanisms utilize second messengers like cAMP, IP3, and Ca²⁺.
c. Major Glands and Hormones
The Pituitary gland secretes hormones like GH, TSH, ACTH, LH, FSH, ADH, and oxytocin.
The Thyroid gland produces T3/T4 (metabolism) and calcitonin (calcium regulation).
The Parathyroid glands secrete PTH to increase blood calcium levels.
The Pancreas produces insulin (lowers glucose) and glucagon (raises glucose).
The Adrenal glands include the cortex (cortisol, aldosterone) and medulla (epinephrine/norepinephrine).
The Gonads produce estrogen, progesterone, and testosterone.
d. Endocrine Disorders
Common disorders include diabetes, hypoglycemia, Graves' disease, Hashimoto's disease, goiter, and cretinism.
Advanced disorders include Cushing's syndrome, Addison's disease, myxedema, and acromegaly.
e. Endocrine Treatments
Treatments can include hormone replacement, surgery, and medications such as levothyroxine, insulin, and corticosteroids.
3. Sensory System
a. Sensory Receptors
Mechanoreceptors detect touch and pressure.
Thermoreceptors sense temperature.
Nociceptors detect pain.
Chemoreceptors are involved in taste and smell.
Photoreceptors detect light.
b. General Senses
These include touch, pressure, pain, temperature, itch, and proprioception.
c. Special Senses
Vision involves the retina (rods/cones), optic nerve, and lens accommodation.
Hearing relies on cochlear hair cells and the auditory nerve.
Balance is managed by the vestibule (static balance) and semicircular canals (dynamic balance).
Smell involves the olfactory bulb and receptors.
Taste receptors detect sweet, salty, sour, bitter, and umami.
d. Sensory Disorders
Eye disorders include myopia, hyperopia, presbyopia, nyctalopia, astigmatism, conjunctivitis, and color blindness.
Ear disorders include otitis media and conductive vs. sensorineural deafness.
Smell/taste disorders include anosmia/dysosmia and dysgeusia.
4. Genetics
a. Key Concepts in Inheritance
Monohybrid crosses involve one trait, while dihybrid crosses involve two traits.
Dominant alleles mask the effect of recessive alleles in heterozygotes.
Genotype refers to the genetic makeup (e.g., Aa), while phenotype is the physical expression (e.g., brown eyes).
b. Sex-Linked Traits
These traits are carried on the X chromosome, making them more common in males (XY).
Pedigrees are used to track inheritance patterns through generations.
c. Human Sex Determination
XX chromosomes determine female sex, while XY chromosomes determine male sex.
d. Allele Variations
More than two allele options can exist for a gene, as seen in ABO blood types (A, B, AB, O).
e. Practice Skill Targets
Students should be able to solve mono- and dihybrid crosses using Punnett squares.
They should also be able to analyze sex-linked inheritance in pedigrees and identify genotypes from phenotypes and vice versa.
f. DNA, Genes, and Proteins
Genes code for proteins.
DNA replication is a semi-conservative process involving A-T and C-G base pairing.
Mutations (substitution, deletion, insertion) can be silent, harmful, or helpful.
g. Mitosis vs. Meiosis
Mitosis produces two identical body cells.
Meiosis produces four unique sex cells (gametes).
Crossing over and independent assortment during meiosis generate genetic variety.
h. Karyotype Analysis
Karyotypes can detect nondisjunction, leading to extra or missing chromosomes (e.g., Trisomy 21 in Down syndrome).
i. Dominance Types
Incomplete dominance results in a blending of traits (e.g., pink flowers from red and white parents).
Co-dominance expresses both traits fully (e.g., AB blood type).
j. Abnormal Gametes and Aneuploidy
Abnormal gametes can be caused by nondisjunction during meiosis, leading to aneuploidy (abnormal chromosome number).
k. Trihybrid Crosses
For crosses involving three traits, probability rules are used instead of large Punnett squares.
l. Molecular Mutation Consequences
Mutations can change protein structure (e.g., sickle cell anemia) leading to loss of function, gain of function, or no effect.
m. Multifactorial Traits and Epistasis
Multifactorial traits are influenced by multiple genes and the environment.
Epistasis occurs when one gene masks the expression of another gene (e.g., coat color in Labrador retrievers).
n. Modern Genetic Tools
PCR (Polymerase Chain Reaction) is used to quickly copy DNA.
DNA sequencing determines the exact order of bases in a DNA molecule.
5. Disease Detectives
a. Epidemiology
Epidemiology is the study of the distribution and determinants of health-related events in populations, used to control health problems.
It differs from clinical health (individual treatment) by focusing on the public health of a population.
b. Natural History of Disease
The natural history of disease describes its progression in an individual from exposure to outcome.
c. Chain of Transmission
The chain of transmission outlines the steps for an infectious agent to move from source to host: infectious agent, reservoir, portal of exit, mode of transmission, portal of entry, and susceptible host.
d. Public Health Surveillance
Public health surveillance involves the systematic collection, analysis, interpretation, and dissemination of health data for planning and evaluation.
e. Observational and Experimental Studies
Observational studies include cohort studies (comparing exposed vs. unexposed) and case-control studies (comparing those with and without an outcome).
Experimental studies, such as Randomized Controlled Trials (RCTs), are considered the gold standard for testing interventions.