Human development

Endocrine System:

Homeostasis-

• Maintaining internal balance in body

  • organism must keep internal conditions stable even if environment changes

  • also called “dynamic equilibrium

• example: body temperature

  • humans

    • too cold = shiver

    • too hot = sweat

  • lizard

    • too cold = bask in sun

    • too hot = hide in shade

Regulation-

• How we maintain homeostasis:

  • nervous system

    • nerve signals control body functions

  • endocrine system

  • hormones

  • chemical signals control body functions

Hormones-

• Why are hormones needed?

  • chemical messages from one body part to cells in other parts of body

  • communication needed to coordinate with whole body

  • maintaining homeostasis

Endocrine system-

• Endocrine system releases hormones

  • glands which secrete chemical signals into blood

    • chemicals cause changes in other parts of body

      • growth hormones

      • sex hormones

      • response hormones

      • metabolism hormones

      • and more…

Responding to hormones-

• Lock and key system

• hormone fits receptor on “target” cell

Glands-

• Pineal

  • melatonin

• pituitary

  • many hormones: master gland

• thyroid

  • thyroxine

• adrenal

  • adrenaline

• pancreas

  • insulin, glucagon

• ovary

  • estrogen

• testes

  • testosterone

Negative feedback-

• Response to changed body condition

  • if body is high or low from normal level

    • signal tells body to make changes that will bring body back to normal level

  • once body is back to normal level signal is turned off

Development:

Sex and growth hormones-

• Large scale body changes

  • how do they work

    • turn genes on

    • start new processes in the body by turning genes on that were lying “dormant”

Reproductive hormones-

• Testosterone

  • from testes

  • sperm production and secondary sexual characteristics

• estrogen

  • from ovaries

  • egg production, preparing uterus for fertilized egg and secondary sexual characteristics

Male reproductive system-

• Sperm production

  • over 100 million produced per day

  • about 2.5 million released per drop

• testes and epididymis

  • sperm production and maturation

• glands

  • seminal vesicles, prostate, bulbourethral

  • produce seminal fluid

    • nutrient rich

• testicles

  • produces sperm and hormones

• scrotum

  • sac that holds testicles outside of body

• epididymis

  • Where sperm mature

• vas deferens

  • tubes for sperm to travel from testes to penis

• prostate, seminal vesicles, Cowper’s (bulbourethral) glands

  • nutrient rich fluid to feed and protect sperm

Female reproductive system-

• Ovaries

  • produces eggs and hormones

• uterus

  • nurtures fetus; lining builds up each month

• fallopian tubes

  • tubes for eggs to travel from ovaries to uterus

• cervix

  • opening to uterus, dilated 10 cm for birthing baby

• vagina

  • birth canal for birthing baby

Menstrual cycle-

• Controlled by interaction of 4 hormones

  • FSH and LH

  • estrogen

  • progesterone

Female hormones-

• FSH and LH

  • released from pituitary

  • stimulates egg development and hormone release

  • peak release = release of egg (ovulation)

• estrogen

  • released from ovary cells around developing egg

  • stimulates growth of lining of uterus

  • decreasing levels cause menstruation

• Progesterone

  • released from “corpus luteum” in ovaries

    • cells that used to take care of developing egg

  • stimulates blood supply to lining of uterus

  • decreasing levels cause menstruation