General Biology II ; Midterm 2 Review

What is homeostasis 😮‍💨?

The ability to maintain a stable internal environment despite external changes.

What are the two types of feedback regulation in homeostasis?

• Negative feedback: Reduces stimulus (e.g. body temp, blood glucose).

• Positive feedback: Amplifies stimulus (e.g. childbirth, blood clotting).

Why are animals considered open systems?

They exchange matter and energy with the environment (e.g. gas exchange, nutrient uptake, waste elimination).

How does body structure affect exchange with the environment?

• Coelomates: Body cavity allows efficient internal transport.

• Acoelomates: Lack body cavity, simpler exchange mechanisms.

What adaptations help organisms with exchange?

Branching (lungs/gills), folding (intestines), and internal fluids (blood, interstitial fluid).

What are hormones?

Chemical messengers that regulate physiological responses.

How does endocrine signaling work?

Hormones are secreted into the bloodstream and affect only cells with the correct receptors.

What is receptor regulation?

• Down-regulation: Fewer receptor activity when hormone levels are high.

• Up-regulation: More receptor activity when hormone levels are low.

What is paracrine vs autocrine signaling?

• Paracrine: Targets nearby cells (e.g. histamine).

• Autocrine: Targets the same cell that secreted the signal (e.g. T cell cytokines).

What is synaptic signaling?

Neurons release neurotransmitters across synapses (e.g. acetylcholine → muscle contraction).

What is neuroendocrine signaling?

Neurons release hormones into the blood (e.g. adrenaline for fight/flight).

What is pheromone signaling?

Chemicals released into the environment to signal other individuals (e.g. mating signals in ants).

What are the 3 major hormone classes?

• Polypeptides (e.g. insulin): Water-soluble.

• Steroids (from cholesterol): Lipid-soluble.

• Amines: Some water-soluble, some lipid-soluble.

How do water-soluble hormones act?

• Cannot cross membranes; bind surface receptors.

• Trigger signal transduction → cytoplasmic response.

• Effects are rapid but short-lived.

Describe the signal pathway for water-soluble hormones.

1. Hormone secreted via exocytosis.

2. Travels freely in blood.

3. Binds to G-protein-coupled receptor on target cell.

4. Activates G-protein → activates adenylyl cyclase.

5. ATP → cAMP.

6. cAMP activates protein kinase → modifies protein function.

How do lipid-soluble hormones act?

• Can cross membranes but not dissolve in blood.

• Use transport proteins to travel.

• Enter target cell → affect gene expression → longer-lasting response.

Describe the lipid-soluble hormone pathway.

1. Hormone diffuses out of endocrine cell.

2. Binds to transport protein in blood.

3. Enters target cell → binds receptor.

4. Hormone-receptor complex enters nucleus OR binds DNA directly → gene expression changes.

How can one hormone have multiple effects?

Depending on receptor type and response proteins in the cell.

E.g. Epinephrine boosts blood flow to muscles but restricts it to digestive system.

What are endocrine glands?

Ductless glands that secrete hormones directly into bodily fluids; regulate metabolism and homeostasis.

What are exocrine glands?

Glands that secrete via ducts to specific locations (e.g. sweat, salivary, digestive glands).

What is negative feedback in endocrine regulation?

A process where rising hormone levels inhibit further secretion to maintain homeostasis.

What is positive feedback in hormone regulation?

A loop where the response amplifies the original stimulus (e.g., oxytocin during childbirth).

Describe a simple endocrine pathway.

Endocrine cells detect a stimulus → release hormone → hormone travels via bloodstream → binds target cells → response.

Example: Secretin release in response to acidic chyme.

What is a simple neuroendocrine pathway?

Stimulus → sensory neurons → neurosecretory cells → release neurohormones into blood → target response.

Example: Oxytocin release for milk ejection.

What is the role of the hypothalamus in endocrine control?

It's a neuroendocrine center linking the nervous & endocrine systems, connected to the pituitary via portal vessels.

How does the hypothalamus influence the anterior pituitary?

Via releasing/inhibiting hormones that travel through portal vessels to stimulate/inhibit AP hormone secretion.

How does the hypothalamus influence the posterior pituitary?

It produces neurohormones (ADH, oxytocin) that are transported down axons and stored in the posterior pituitary until release.

What does the posterior pituitary release, and where are these hormones made?

Releases ADH (water retention) and oxytocin (milk ejection, contractions, bonding); both made in the hypothalamus.

What is the anterior pituitary and how is it controlled?

An endocrine gland controlled by hypothalamic RH [releasing hormones] /IH [inhibiting hormones]; it releases hormones into the bloodstream.

Differentiate between tropic and non-tropic AP hormones.

Tropic: Stimulate other endocrine glands.

Non-tropic: Directly affect target tissues.

Describe the hormone-cascade pathway.

Hypothalamus → Anterior Pituitary → Endocrine Gland → Target Tissue → Physiological Response.

What are the functions of thyroid hormones (T3/T4)?

Increase metabolism, regulate BP, digestion, and reproduction.

How is thyroid hormone secretion regulated?

1. Hypothalamus → releases TRH [thyrotropin-releasing hormone; tropic]

2. Anterior Pituitary → releases TSH [thyroid stimulating hormone; tropic]

3. Thyroid gland → releases T3/T4 [thyroid hormone; non-tropic]

4. Target cells respond → increased metabolism.

- Negative feedback inhibits TRH & TSH when T3/T4 levels are high.

What causes hypothyroidism and what are its symptoms?

Cause: Iodine deficiency → low T3/T4.

Symptoms: Weight gain, fatigue, cold intolerance, goiter.

What is the cause and symptoms of hyperthyroidism?

Cause: Graves' disease (autoimmune).

Symptoms: Weight loss, high BP, irritability, sweating.

What happens when blood Ca²⁺ is too low?

• PTH released from parathyroid glands.

• Increases bone breakdown, kidney reabsorption, and vitamin D activation.

• Raises blood Ca²⁺ levels.

What happens when blood Ca²⁺ is too high?

• Calcitonin (from thyroid) is released.

• Inhibits bone calcium release, increases calcium excretion via kidneys.

• Lowers blood Ca²⁺.

How do PTH and calcitonin interact?

They are antagonistic: PTH raises, calcitonin lowers blood calcium.

What are the two parts of the adrenal gland and how do they differ?

• Adrenal medulla: Controlled by nerve signals; releases epinephrine/norepinephrine (short-term stress).

• Adrenal cortex: Controlled by hormones; releases corticosteroids (long-term stress).

What triggers adrenal medulla hormone release and what are the effects?

Triggered by nerve signals from the hypothalamus.

Effects: ↑ heart rate, ↑ breathing, ↑ glucose (via glycogen breakdown), blood redirected to muscles/brain.

Describe the adrenal cortex pathway and its hormones.

1. Hypothalamus releases CRF [corticotropin-releasing factor]

2. Anterior Pituitary releases ACTH [adrenocorticotropic hormone]

3. Adrenal Cortex releases corticosteroids:

• Glucocorticoids (cortisol): ↑ blood glucose, breaks down muscle, suppresses immune system.

• Mineralocorticoids (aldosterone): ↑ sodium reabsorption, water retention, stabilizes BP.

What is asexual reproduction?

Reproduction involving a single parent producing identical offspring without meiosis or gamete fusion.

Types of asexual reproduction?

• Budding

• Binary fission

• Regeneration/Fragmentation (e.g. starfish)

• Parthenogenesis (unfertilized egg develops into organism; in insects, amphibians, reptiles)

Pros and cons of asexual reproduction?

✔ Fast, no need to find a mate. ✘ No genetic variation.

What does sexual reproduction involve?

Fusion of gametes (sperm + egg) to form a genetically unique zygote.

Features of sperm vs. egg?

• Sperm: small, motile, has flagellum.

• Egg: large, non-motile, nutrient-rich.

Advantages of sexual reproduction?

✔ Increases genetic diversity, eliminates harmful alleles.

✘ Only half the population (females) can reproduce.

Two main functions of the male reproductive system?

Produce sperm & deliver it to the female reproductive tract.

What is the function of the testes ["Sperm factory"]?

Sperm production + hormone (testosterone) secretion.

What occurs in seminiferous tubules [long, hollow tubes]?

Spermatogenesis (sperm formation).

What do Leydig cells do?

Produce testosterone and other male sex hormones.

What is the function of the epididymis ["Sperm training center"]?

Transports, matures (adds motility), and stores sperm (~3 weeks).

Why are testes in the scrotum ["Climate control system"]?

It keeps them cooler than body temp, which is essential for sperm development. It also contains the testes & the epididymis.

Do all mammals have external scrotums?

No—some (e.g. whales, elephants) have internal scrotums.

What is the function of the penis ["Sperm delivery system"] in reproduction ?

Delivers sperm via the urethra.

What causes an erection?

Sexual stimulation → Nitric oxide release → smooth muscle relaxes → blood fills erectile tissue → veins compress → blood trapped = erection.

What is a hydrostatic skeleton in the penis?

Pressurized blood in erectile tissue supports the structure.

Where are most sensory nerves in the penis?

In the glans (tip).

What do the seminal vesicles ["Sperm-fueling station"] secrete?

Fructose (sperm energy) & prostaglandins (stimulate uterine contractions); ~60% of semen volume.

Why is seminal fluid forensically important?

It fluoresces under UV light.

What is the function of the prostate gland ["Activator gland"]?

Produces citrate and anticoagulants for sperm nourishment.

Why is the prostate clinically important?

Common site of cancer in men over 50; 50% over 40 have enlarged prostates.

What does the bulbourethral gland do?

2 small, round glands on either side of the urethra; releases mucus first during arousal to neutralize acidic urine; may carry sperm.

What is semen composed of?

Sperm + fluids from seminal vesicles, prostate, and bulbourethral glands.

What is the full path of sperm from production to ejaculation?

Testes → Epididymis → Vas deferens → Ejaculatory duct → Urethra → Penis

Function of the vas deferens?

Sperm ducts; 1 from epididymis; transports sperm from epididymis to urethra.

Where does the ejaculatory duct pass through?

The prostate gland; joins the urethra.

What is spermatogenesis?

Process of sperm production (~7 weeks, continuous).

Describe the stages of spermatogenesis.

1. Embryo: Primordial germ cells → spermatogonia

2. Puberty:

• Spermatogonia (2n) divide → 1º spermatocytes (2n)

• 1º spermatocytes → meiosis I → 2º spermatocytes (n)

• 2º spermatocytes → meiosis II → spermatids (n)

• Spermatids mature into sperm.

What are the parts of a mature sperm cell?

• Head: DNA + acrosome (enzymes)

• Midpiece: mitochondria

• Tail: flagellum for movement

What are androgens?

Male sex hormones (main one = testosterone).

What initiates hormone release in male reproduction?

Hypothalamus → GnRH → Anterior Pituitary → FSH + LH

What does testosterone trigger during puberty?

Development of primary (sex organs) & secondary (deep voice, body hair, muscle) sex characteristics.

What does LH [luteinizing hormone] do in males?

Stimulates Leydig cells → testosterone production → supports spermatogenesis.

What does FSH [follicle stimulating hormone] do in males?

• Stimulates seminiferous tubules.

• Stimulates Sertoli cells → release ABP [androgen binding protein] → maintains high testosterone in testes.

What do Sertoli cells secrete when sperm count is high?

Inhibin → inhibits FSH release.

What are the primary functions of the female reproductive system?

Produce ova, receive sperm, enable fertilization, house and nourish embryo, give birth, and lactate to feed offspring.

What are the functions of the ovaries?

Produce gametes (eggs) via oogenesis and secrete estradiol and progesterone.

What is the role of the oviducts (fallopian tubes)?

- Capture secondary oocyte post-ovulation, transport it to the uterus via cilia and smooth muscle contractions

- Serve as the site of fertilization.

What are the two main layers of the uterus and their functions?

- Myometrium: smooth muscle layer for childbirth contractions. - Endometrium: inner lining that thickens each month for potential implantation.

What happens to the endometrium with or without fertilization?

With fertilization: embryo implants.

Without: lining sheds during menstruation.

What are the cervix, vagina, and vulva responsible for?

Cervix: lower uterus, passageway and cancer site.

Vagina: receives penis/sperm, birth canal.

Vulva: protects vaginal opening.

Describe oogenesis BEFORE birth.

Primordial germ cells → mitosis → oogonia → mitosis → primary oocytes (arrested in Prophase I) — about 1-2 million at birth, ~200,000 by puberty.

What happens during oogenesis after puberty?

6-12 follicles begin maturing monthly; one primary oocyte completes Meiosis I → forms one secondary oocyte (n) and one polar body (n); secondary oocyte arrests in Metaphase II [ONLY completes meiosis II if pregnancy].

What triggers ovulation and what happens to the oocyte?

LH surge causes mature follicle to rupture, releasing the secondary oocyte into the oviduct.

What is the corpus luteum and its function?

It forms from the leftover follicle post-ovulation and secretes progesterone + estrogen to prepare the uterus. Disintegrates if no pregnancy.

What are the two major components of the menstrual cycle and their phases?

Ovarian cycle: Follicular (1-13), Ovulation (14), Luteal (15-28).

Uterine cycle: Menstrual (1-5), Proliferative (6-13), Secretory (15-28).

What are the key female sex hormones and where are they produced?

Estradiol: from follicles and corpus luteum; progesterone: mainly from corpus luteum.

What are the functions of estradiol?

Triggers puberty, secondary sex characteristics, and endometrial growth during each cycle.

What is the main function of progesterone?

Finalizes endometrial development and stimulates glands to secrete nutrients for embryo.

What is the hormone pathway controlling the female reproductive cycle?

Hypothalamus → GnRH → AP → FSH & LH → ovaries → estrogen & progesterone.

What happens during the early follicular phase hormonally?

Low estradiol → GnRH from hypothalamus → FSH & LH from AP → small follicles begin growing.

***Negative feedback: Low estradiol = slow FSH & LH production.

What changes occur in the late follicular phase?

Large follicle produces high estradiol → positive feedback → LH surge → ovulation.

What happens during the early luteal phase?

Corpus luteum secretes high progesterone + some estradiol → inhibits GnRH → prevents new follicles from maturing.

What happens during the late luteal phase if no pregnancy occurs?

Hormone levels drop → endometrium begins to break down → menstruation begins → GnRH restarts the cycle.

What happens during the menstrual flow phase (days 1-5)?

Endometrial lining is shed. New ovarian follicles begin to grow.

What occurs during the proliferative phase?

Coordinated w/ Follicular phase; Estradiol from follicles causes endometrial thickening; prepares uterus for possible embryo.

What occurs during the secretory phase?

Overlaps w/ Luteal phase; Progesterone and estradiol from the corpus luteum thicken and vascularize [develop blood vessels] the endometrium; endometrial glands grow [fill w/ nutrient-rich fluid] to support embryo.

What happens if there is NO pregnancy during the secretory phase?

Corpus luteum disintegrates → hormone levels drop → blood flow to endometrium stops [constricts]→ lining breaks down → menstruation begins.

What is development in biology?

All changes from zygote to adult—including embryonic development, growth, maturation.