6.6 Homeostasis and Endocrine

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    • 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