IB Bio Topic 6.6 - Hormones, Homeostasis, and Reproduction

Homeostasis

the process that keeps internal conditions (temperature, pH, CO2 concentrations) within certain limits.

Hormones

chemical messengers produced by glands and certain neurosecretory cells. They are released into the blood in low concentrations and rapidly spread throughout the body.

Neurosecretory Cells

neurons that make hormones and release them into the blood

Target Cells (Target Organs)

organs or cells with receptors that can bind to certain hormones

Islets of Langerhans

a structure in the pancreas that produces and secretes insulin (via its beta cells) and glucagon (via its alpha cells).

Insulin

A hormone that is released when the blood glucose level is higher than normal. It stimulates glucose uptake into muscle and liver cells, where it is converted into glycogen.

Glucagon

A hormone that is released when the blood glucose level is lower than normal. It stimulates glycogen hydrolysis in the liver, producing glucose which is released back into the blood.

Exocrine

term meaning associated with a duct. Also refers to the pancreas’ function of secreting enzymes that help with digestion.

Endocrine

term meaning ductless. Also refers to the pancreas’ secretion of insulin and glucagon to regulate blood sugar levels.

Diabetes

A disease characterized by consistently high blood glucose levels (as well as glucose levels in urine).

Type I Diabetes (Type 1 Diabetes)

failure to produce insulin, treated by insulin injections

Type II Diabetes (Type 2 Diabetes)

insulin resistance, treated by a mixture of a low carb diet, frequent small meals, strenuous exercise, and weight loss

Thyroxine (Thyroxin)

a hormone secreted by the thyroid gland. It regulates metabolism and body temperature by (generally) activating nuclear transcription for genes to produce enzymes, structural proteins, transport proteins, and other substances to improve metabolism

Adipose Tissue (Adipose Tissues)

fatty tissues mainly composed of fat cells (adipocytes) that are specialized in the synthesis and storage of fat globules

Leptin

A hormone produced and secreted by cells in adipose tissues. Its concentration is controlled by food intake and the amount of adipose tissues in the body.

Melatonin

a hormone, secreted from the pituitary gland, that is responsible for maintaining the circadian rhythm.

Pineal Gland

a small endocrine gland near the center of the brain. It is characterized by its reddish gray, pine-cone-like shape.

Jetlag (Jet lag)

the mismatch between melatonin production and the level of light exposure as a result of traveling across time zones.

Gonads

Term for a sex gland. In an embryo, this can differentiate into either ovaries (XX) or testes (XY)

Testis Determining Factor (TDF)

a DNA-binding protein that regulates the transcription of various genes to differentiate the embryonic gonads into testes

Testosterone

A hormone produced by the testes. It triggers the production of sperm.

Ovary (Ovaries)

Female genitalia, responsible for estrogen, progesterone and ovum (egg) production

Fallopian Tubes

These collect eggs from ovary and carries them to uterus

Uterus

Location for the gestation of the embryo and fetus

Cervix

This structrue blocks the entry to the uterus during pregnancy and dilates during birth

Vagina

A canal connecting cervix and outside of body: forms birth canal and is the receptacle for penis during heterosexual intercourse

Vulva

External parts for the protection of the internal reproductive system

Testis (Testes)

Male genitalia, responsible for sperm and testosterone production

Epididymis

Stores sperm until ejaculation

Sperm Duct

Transfers sperm during ejaculation

Seminal Vesicles

Produce an alkaline, sugar-rich fluid (fructose) that provides sperm with a source of energy to help them move

Prostate Gland

Produces an alkaline fluid, rich in proteins which together with seminal vesicles' secretion and sperm makes semen

Urethra

Transfers semen during ejaculation and is the passage of urine during urination

Penis

Becomes erect during sexual arousal: penetrates the vagina during heterosexual intercourse to deposit semen close to the cervix

Puberty

phase of adolescence when the individual reaches sexual maturity and becomes capable of reproducing. It is accompanied by maturation of the genital organs, development of secondary sexual characteristics and, in humans and some primates, by the first occurrence of menstruation in the female.

Menopause

the phase in a woman's life (around the age of 45–50) when her menstruation stops.

Menstrual Cycle

the cyclic and periodic change in ovarian and pituitary hormones that controls when a woman is fertile (can become pregnant)

Follicular Phase

First phase of the menstrual cycle, characterized by the formation of follicles in the ovaries

Ovulation

Second phase of the menstrual cycle, referring to the release of an ova (egg cell)

Luteal Phase

Third phase (and second half) of the menstrual cycle, characterized by the transformation of a follicle into a corpus luteum after ovulation

Menstruation

Final phase of the menstrual cycle, where the lining of the uterus is shed and bleeding starts

FSH (Follicle-stimulating Hormones)

A pituitary hormone. Its levels rise near the end of the cycle (menstruation) as it stimulates the development of follicles.

LH (Luteinizing hormones)

A pituitary hormone. It suddenly peaks near the end of the follicular phase and causes the follicle to rupture and release an egg (ovulation) that is filled with follicle cells to produce the corpus luteum.

Estrogen

An ovarial hormone. Its levels rise near the end of the follicular phase. It stimulates the thickening of the endometrium.

Progesterone

An ovarial hormone. Its levels rise at the start of the luteal phase. It stimulates the continued thickening of the endometrium.

In Vitro Fertilization (IVF)

an artificial form of fertilization in which sperm and egg are joined in a vitro (glass)

Superovulation

high production of ova (egg cells) as a result of high dose injections of LH and FSH

Corpus Luteum

temporary organ made from remainder of ruptured follicle filling with cells

Endometrium

where the fertilized ovum will implant to further develop during pregnancy

Follicle

A sac containing 1 egg during its development until ovulation