Nerves, Hormones & Homeostasis Reproduction,

The Endocrine System A stimulus is received and processed. Hormones are secreted directly into the blood. They are carried to the target tissues (the place of intended action). The action of the hormone changes the condition of the tissue. This change in monitored through feedback. Most hormonal change results in negative feedback. Key endocrine glands: 1.Pineal glandPineal gland 2.Pituitary glandPituitary gland 3.Thyroid glandThyroid gland 4.ThymusThymus 5.Adrenal glandAdrenal gland 6.PancreasPancreas 7.Ovary (female)Ovary (female) 8.Testes (male)Testes (male) Endocrine glands from:

More hormones in IB Biology Thyroxin regulates metabolic rate and controls body temperature Leptin inhibits appetite Melatonin controls circadian rhythms

Thyroxin Secreted by thyroid Contains four molecules of iodine Iodine deficient diets prevents thyroxin synthesis Regulates metabolic rate so acts on all cells in body. Liver, muscle and brain are main targets

Thyroxin regulates body temperature High metabolic rate supports protein synthesis, growth and generation of body heat Body cooling triggers thyroxin production, stimulating heat production

Thyroxin deficiency Lack of energy, fatigue Forgetfulness, depression Weight gain w/ loss of appetite Constant feeling of being cold Constipation Impaired brain development in children

Leptin Protein hormone secreted by adipose (fat storage) cells Leptin in blood is controlled by food intake and adipose tissue in blood Targets cells in hypothalamus that control appetite If adipose tissue increases, blood leptin concentrations rise, inhibition of long-term appetite, reduced food intake

Melatonin Secreted by pineal gland Circadian rythym- behavioral rhythms, controlled by an internal system, that fit a 24- hour cycle C.R. depend upon cells in hypothalamus called suprachiasmatic muclei (SCN) SCN cells secrete the hormone melatonin by the pineal gland

melatonin Secretion increases in the evening and drops to a low level at dawn Hormone is removed from blood by liver, causing blood concentrations to rise and fall rapidly Sleep/wake cycle High level promote sleep & drop core body temperature possibly decreased urine output

Jet Lag & melatonin Cells in retina detect light and pass signal to cells in SCN indicating timing of dusk/ dawn & signals melatonin secretion/ decreased production. SCN and pineal gland are adjusted to day/night at departure location Lasts a few days Ganglia in retina send signals of light to SCN and it eventually adapts to new timings of dawn/dusk Oral melatonin at the normal bed time can help reduce jet lag

The Reproductive System The gonads, (the primary sex organs) are the testes in males and the ovaries in females. The reproductive role of the male is to manufacture sperm and deliver them to the female reproductive tract. The reproductive role of the female is to produce ova (egg cells) and (after fertilization) to protect and provide nutrients for the growing fetus. Click on him or her to see tutorials.

Image: sperm and egg Male Reproductive System Click on the interactive above to label the male reproductive system: _reproductive.html

LA Male Reproductive System Bladder Sperm duct (vas deferens) Urethra Epididymis Glans penis Scrotal sac Testis Prostate gland Seminal vesicle

6.6.1 Draw and label a diagram of the adult male reproductive system.

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Sex determination in males SRY gene located on Y chromosome SRY gene codes for DNA-binding protein called TDF (testis determining factor) TDF simulates other genes that cause testis development If SRY gene is not present (X,X) then TDF is not produced: embryonic gonads develop as ovaries

Testosterone Testes develop around 8 th week of pregnancy Testes develop testosterone-secreting cells and produce testosterone until 15 th week of pregnancy, resulting in formation of male genetalia

LA Female Reproductive System Bladder Urethra Pubis (pubic bone) Clitoris Labia Vagina Anus Cervix Spine Colon Ovary Fallopian tubeUterus Sagittal section through female abdomen

6.6.1 Draw and label a diagram of the adult female reproductive system.

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Sex determination in females No SRY gene: embryonic gonads develop as ovaries Testosterone not secreted Estrogen & progesterone are present in all pregnancies Absence of testosterone and maternal estrogen and progesterone result in formation of female reproductive organs.

puberty Secretion of estrogen and progesterone increases Result: development of secondary sexual characteristics – Enlargement of breasts – Pubic hair & underarm hair – Widening of pelvis

An oocyte is the precursor to an egg cell. All oocytes have been in place since before birth. At the onset of puberty, they start to be matured and released on a cycle. Egg cells develop in follicles. This micrograph shows an oocyte developing into a mature ovum, inside a follicle in an ovary. Follicle stimulating hormone (FSH) triggers the development of the follicle and oocyte.

Menstrual cycle Occurs from puberty until menopause Each cycles allows for possibility of pregnancy 1 st half of cycle: follicular phase – follicles develop in ovaries – Lining of uterus repaired& thickens – Most developed follicle ruptures, releasing egg into oviduct – Other follicles degenerate

Second half: luteal phase – Walls of follicle that released egg becomes a body called corpus luteum.

Click on the animation above to go to watch the graph form (APBI Schools.org.uk)

A B C D menstruation

Video and doctors’ advice from NHS UK: More Menstrual Cycle Animations Simple animation, no graphs: How the contraceptive pill work?  this site has a good comparison of the regular menstrual cycle and the cycle with the influence of contraceptive pills.

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