Biology 102 Notes for Exam 4
The Immune System
B-cells make antibodies (Ab) also called immunoglobins
Adaptive - tertiary level of protection
Invasion by pathogens → specific defense mechanisms → the part of the immune system unique to vertebrates → cell mediated adaptive immunity. T cells act against specific intracellular pathogens and cancer (intra=inside)
Two Types of T-Cells
- Helper T-Cells: secrete proteins to stimulate more B cells and both types of T cells to be formed
- Cytotoxic T-cells: act directly on cells infected by pathogens or cancer cells. Release enzymes that cause cell death of target.
The adaptive immune system is - antigen specific - able to recognize self vs nonself and act accordingly (people whose bodies have problems with this recognition may have autoimmune diseases such as lupus, arthritis, MS, Crohn's disease) - made of cells for now and cells for later. B and T cells may be effector cells (act now) or memory cells (wait around to act later). Naive B or T cell → first exposure to antigen → primary immune response → effector cells act now, memory cells wait around for later → Another exposure to the same antigen provokes secondary response. Secondary response is faster and stronger (advantage of having memory cells) → secondary immune response → memory cells divide and make effector cells and more memory cells.
Vaccination (immunization) named after the vaccinia virus: caused cowpox and led to immunity against smallpox. Made from inactivated toxin or virus, dead bacteria, or just their antigens. Success relies on immune system’s memory cells. Polio, measles, whooping cough, all very rare (and smallpox has been eradicated). Great public health success, but some diseases are making a comeback due to anti-vaxxers.
HPV - human papillomavirus, an STD that causes genital warts (and may cause cervical cancer in women). Affects both men and women- spread easily by sexual contact, even if no obvious symptoms. If you want to learn more check out What is a mass fatality incident?
We also discuss several other topics like What are some key characteristics of human developmen?
Being vaccinated against HPV can prevent initial infection, but it’s not a cure (and the vaccine only targets the 4 strains of HPV that cause most of the associated cancers). So far, Gardasil has been marketed for women ages 9-11 but they are starting to recommend it for young men too.
Immune system cells move through the lymphatic system where memory cells live. Lymph node--contains white blood cells of all types and filters pathogens out of lymph. Thymus sits on top of the heart. Tonsils are lymph nodes, spleen is part of the immune system, too. We also discuss several other topics like What are the factors that drive the evolution of territoriality?
Humans have evolved from a common ancestor like all animals. Within the mammalian subclass of placental mammals is the order primates with 2 suborders.
1. Suborder Prosimians = older primates = lemurs, tarsiers
2. Suborder Anthropoid = monkeys, apes, humans
Rely more on sight and less on smell than prosimians. Monkeys have tails, apes do not have tails.
Hominin - modern humans and extinct human-like species who were bipedal. There are anatomical changes associated with bipedalism in hominins - musculature, backbone curve, skull placement.
Bipedalism has some drawbacks -- lower back supports more weight, gets more injuries. More pressure and weight on knees. Upright pelvis, larger brain = more difficult labor. Don't forget about the age old question of Anthropology is a study of what?
Two early groups of hominins
1. Homo erectus = evolved about 1-8 mya, skilled tool maker. Hunted large prey in groups, built fires. Homo sapiens eventually evolved from this lineage by 195,000 years ago. 2. Homo neanderthalensis - existed 230,000 to 33,000 years ago (also evolved from H. erectus, but separate branch).
Larger rear brain than modern H. sapiens but smaller frontal lobe (controls intelligence). Cared for their injured and buried their dead. Considered to be evolutionary dead ends. Possibly some H. sapiens and H. neanderthalensis interaction?
Several species of hominins many of which lived at the same time and overlapped. Modern homo sapiens is the only surviving branch of the hominin tree.
Humans did not evolve from chimpanzees. Human evolution is not like a ladder(anagenesis). Bipedalism did not coevolve with intelligence. Bipedalism is a very old trait that far predates intelligence. The ability to speak (both intellectually as well as anatomically) took a lot of time to evolve.
Common misconceptions about human evolution
1. Humans did not evolve from apes or chimps. Apes and hominins diverged from a common ancestor about 7 million years ago.
2. There were often 2 hominin species at the same time, not a nice linear progression ending in modern humans.
Humans: domain eukarya, kingdom animalia, phylum chordata, subphylum vertebrata, class mammalia, subclass eutheria (placental mammals), order primates, suborder anthropoidea, family hominidae, genus homo, species sapiens.
Modern humans are the only living species in the hominidae family. If you want to learn more check out What components in our atmosphere have offset the effects of a less bright sun toward maintaining liquid water at our surface over most of earth's history?
Intellectual characteristics that separate modern humans from other hominins - sophisticated tools - complex social organization - conceptual thought - language skills - symbolic (written ) language
Milestones of Human Evolution
1. Upright bipedal posture
2. Brain frontal lobe enlargement (intelligence)
3. Prolonged childhood period because or longer and more intense parental care (our bodies are biologically ready to reproduce when puberty starts but most wait). Long subadult period and post reproductive years, rare in the animal kingdom.
4. Culture. The accumulated knowledge, customs, beliefs, arts, etc. that are passed onto future generations. Cave paintings in Lascaux, France are 17,000 years old.
Global population of humans is over 7 billion. Earth has a limited size and limited resources. Growth and sustainability of populations (humans and other organisms) are subject to certain rules. Ecology = study of how organisms interact with each other and the natural world. What are the rules?
Instead of developing evolutionarily in response to the environment, modern humans have learned to control their environments. Buildings, habitat/climate control, agriculture, cooking using heat (less susceptible to illness/parasites), domesticated animals/plants, save food/preserve food, extraction and manipulation of resources and energy, disease control/medicine We also discuss several other topics like What are the different types of discrimination?
Nature Limits Population Growth
There is always a limiting factor - an essential resource in short supply (space, food, refuge, clean air or water) that organisms must compete for. Carrying capacity - the maximum number of individuals that an environment can sustain.
Overcrowding leads to density - dependent controls: predators, pathogens, or parasites that bring the number down. Density independent controls: natural disasters, hurricanes, floods, volcanic eruptions.
Ecologists study the rules of different ecosystems.
Hormones are secreted internally by the endocrine system (special organs, glands, and cells) Hormones = chemical signals that coordinate the different parts of a multicellular organism. Synthesized in one part of the body and transported to another part where they act. Effective in minute amounts. Response is very specific.
Parts of the endocrine system: Hypothalamus (brain), pineal gland (brain), Pituitary gland (brain), thyroid gland (neck), parathyroid glands (on the thyroid, four of them), adrenal glands (one pair on top of kidneys, make adrenaline, also called epinephrine), Pancreatic islets (alpha and beta cells), ovaries (one pair of female gonads), testes (one pair of male gonads). Not part of the endocrine system but does make hormones for the immune system: Thymus (on top of heart) - makes hormones to help T-cells
Hypothalamus and pituitary gland: control much of the endocrine system. The pineal gland: secretes melatonin, controls biological rhythms (day and night cycles, jet lag, SAD). It works by secreting melatonin when dark is detected. The thyroid produces 2 iodine-containing hormones (salt). These stimulate metabolism and influence development and maturation. Hypothyroidism - too little; hyperthyroidism - too much. The pancreas: the parts that function in the endocrine system are islets (little clusters) of alpha and beta cells.
a. stimulus - blood glucose increases after a meal.
b. This stimulates beta cells of pancreas to release insulin.
c. Insulin causes liver to use and store excess glucose as glycogen
d. Insulin causes muscle cells to take up glucose and use it as an instant energy source or store it as glycogen
e. Blood glucose level declines to a set point, so stimulus calling for insulin diminishes. f. Blood glucose is used between meals
g. Alpha cells of pancreas release glucagon into blood. Glucagon hormone, glycogen is the stored form of sugar.
h. Liver responds to glucagon and converts glycogen (storage form of glucose) back to glucose.
i. Blood glucose level increases to a set point, so stimulus calling for glucagon diminishes. Insulin reduces blood glucose levels. Glucagon increases blood glucose levels (antagonistic hormones).
Diabetes mellitus, an endocrine disorder, is a disruption of this.
Type I --juvenile onset = caused by autoimmune disorder; beta cells in pancreas are killed by white blood cells, so insulin is not made. Not usually preventable.
Type II -- adult onset = target cells in other areas of the body lose their ability to respond to insulin; eventually beta cells wear out, often preventable.
With diabetes Types I and II, proper control of blood sugar is key. Side effects if it is not controlled - blindness, amputations, kidney failure. If your blood sugar is under 70, it is illegal to drive because judgement can be impaired. Type II is seen more and more in children now.
Human Reproductive System
Female Reproductive System
2 ovaries, 2 oviduct (fallopian tubes), uterus (lots of muscles), endometrial lining (this is shed during a period), cervix, vagina.
Male Reproductive system
Prostate gland - right below the bladder. Testis (testicle), seminiferous tubule - tubes within testis, where sperm are made. Sperm travel from there to the epididymis where they are stored when they are mature. Long tube--vas deferens, long tube that leads to seminal vesicles on the bottom of the bladder. Move through prostate on the bottom of the bladder, and bulbourethral gland. Semen travels through urethra. It takes about 100 days for sperm to mature, and about 100 million sperm mature every day.
Both males and females can get breast cancer. Prostate cancer - second leading cause of cancer death among men. Can be detected by physical exam or detected by blood tests by looking for PSA (prostate specific antigen). Prostate can sometimes be enlarged and press on the bladder. Testicular cancer - often detected by self exam.
Hormonal control of the Male Reproductive System
GnRH (from the hypothalamus) - gonadotropin releasing hormone → controls release of FSH and LH (from the pituitary). FSH: follicle stimulating hormone. LH: Luteinizing hormone → LH
stimulates testosterone production in the testes. Testosterone is responsible for primary (external genitalia) and secondary (deeper voice, body hair, growth spurt) sex characteristics. FSH promotes spermatogenesis (in the testes).