6.6 Homeostasis and Endocrine

• Homeostasis is the maintenance of a constant internal environment within  physiological tolerance limits
• Regulator is An animal that is able to maintain a constant internal environment, enabling it to continue normal activities more or less whatever the external conditions
• Physiological processes are moderated by feedback loops
• Changed conditions are detected by a receptor
• • A corrective response is initiated by an effector (organ such as skin, liver and kidney)
• Homeostasis is maintained via negative feedback
• Feedback loops are involved in a number of homeostatic processes: thermoregulation, blood pH, and water balance.
• Negative Feedback

  A) stimulus

  B) sensor

  C) control

  D) effector

  
• Hormones are chemical messengers released from ductless or endocrine glands

  • They travel within the bloodstream to act on distant target cells
• 1. Hypoglycemia is a condition where the level of blood glucose is lower than normal (60mg per 100 cm3).
  2. An abnormally high concentration of blood glucose (hyperglycemia). 
• The Endocrine Gland of Insulin and Glucagon is the Pancreas
• The Endocrine Gland of Thyroxine is the Thyroid Gland
• The Endocrine Gland of Leptin is the Adipose tissues (fat cells)
• The Endocrine Gland of Melatonin is the Pineal Gland
• Melatonin is involved in regulating circadian rhythms
• Humans have 23 pairs of chromosomes in all diploid cells

  • 22 pairs of autosomes and the sex chromosomes (X + Y)
• The Y chromosome contains an SRY gene (Sex Region on Y)

  • The gene codes TDF protein (Testis Determining Factor)
• • Males (XY) develop testes and secrete testosterone
  • Females (XX) lack the SRY gene and develop ovaries
• The main male sex hormone is testosterone
•  Testes - Produces sperm and male sex hormones (testosterone)

  Epididymis
• Epididymis - Site where sperm matures and develops the capacity to swim
• Vas Deferens

  Carries sperm from the testes to the urethra
• Seminal Vesicle

  Secretes fructose (for sperm nutrition) and prostaglandins
• Prostate Gland

  Secretes an alkali fluid to neutralize vaginal acids
• Urethra

  Carries sperm to the outside of the body (via the penis)
• Estrogen & progesterone are female sex hormones
• Ovary - The reproductive organ where eggs (ova) are produced
• Fimbriae

  A fringe of tissue that sweeps an oocyte into the oviduct
• Oviduct

  The tube where an ovum passes to the uterus (fallopian tube)
• Uterus

  The organ where a fertilized egg will implant and develop
• Endometrium

  A mucous membrane lining the uterus (shed via menstruation)
• Vagina

  The passage leading to the uterus via which a penis can enter
• Reproductive systems function to produce the gametes for sexual reproduction
• In males, spermatozoa are produced continuously from the onset of puberty
• In females, mature eggs are produced according to a recurring menstrual cycle
• A menstrual cycle describes changes that occur within  the female reproductive system to enable pregnancy
• Menstrual Cycle is controlled by 2 hormones: pituitary hormone and ovarian hormone
• Pituitary Hormones (FSH and LH)Act on the ovaries to develop follicles (oocytes)
• Ovarian Hormones (Estrogen and progesterone) Act on the uterus to prepare for pregnancy
• 3 stages of menstrual cycle: follicular phase, ovulation, luteal phase