Transcript Unit IX: Animal Structure and Function, Part III

Unit IX: Animal Structure and
Function, Part III
Hormones and Reproduction
Regulatory Systems
Nervous system and Endocrine System
• structurally, chemically, and functionally related
+ nervous system: conveys high speed messages via impulses
+ endocrine system: slower means of communication via hormones
- hormone: chemical signal secreted into body fluids to
communicate regulatory messages within the body
- neurosecretory cells: nerve cells that secrete hormones
• regulation of several physiological processes involves overlap
+ each system affects the output of the other
- invertebrate regulatory system
+ molting (see Fig. 45.2)
- ecdysone (molting hormone)
- brain hormone (BH)
- juvenile hormone (JH)
Chemical Signals and their
Modes of Action
How do hormones work?
• Hormones elicit responses by binding to target cells
+ local regulation
- nitric oxide (NO)
+ kills cancer cells and bacteria
+ dilation of blood vessels
- growth factors (peptides/proteins)
+ regulate cell behavior in developing tissues and organs
- prostaglandins (PGs)
+ modified fatty acids
+ induce muscle contraction of uterine wall
+ induce fever/inflammation; intensify pain
• affect only target cells; other cell types ignore the message
How Cells Communicate
• chemical signals bind to
receptor proteins on or within
target cell
+ most chemical signals
are unable to pass through
plasma membrane
+ triggers chemical events
within cell that result in a
change in its behavior
- signal -transduction
pathways
Steroid Hormones
Steroids are lipids
• can pass through cell
membrane
+ bind to receptor protein
+ complex enters the
nucleus
+ binds to regulatory site
+ stimulates transcription
+ specific protein made
Endocrine System
Endocrine Glands
• pineal gland
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+ secretes melatonin
hypothalamus
+ controls pituitary gland
pituitary gland
+ multiple hormones
thyroid gland
+ T3, T4, and calcitonin
parathyroid glands
+ parathyroid hormone
thymus
+ thymosin
adrenal glands
+ epinephrine/norepinephrine and
other steroids
pancreas
+ insulin and glucagon
The Hypothalamus
• recieves info from nerves and
other parts of brain, then initiates
endocrine response
+ neurosecretory cells
- ADH, oxytocin
+ stored in posterior pituitary
Anterior Pituitary
Thyroid Hormones
T3 and T4
• T3: triiodothyronine
• T4: thyroxine
+ 3 vs. 4 iodine atoms
- regulate metabolism
+ T4 secreted and is
converted to T3 in targets
Calcitonin
• lowers blood calcium level
+ prevents decomposition
of bone
- osteoporosis
+ caused by hyperparathyroidism
Parathryroid Hormone
Pancreas
Diabetes
Type I diabetes mellitus
• insulin-dependent diabetes
+ autoimmune disorder
- immune system mounts attack on pancreatic cells
+ require insulin injections
Type II diabetes mellitus
• non-insulin-dependent diabetes
+ adult diabetes (more common- 90% of diabetics)
- deficiency of insulin or reduced response of target cells
+ managed by exercise and dietary control
Gonads
Male Reproductive Structures
Female Reproductive Structures
Testes
• testosterone (androgen)
+ male secondary sex characteristics
Ovaries
• estradiol (estrogen)
+ female secondary sex characteristics
• progesterone (progestin)
+ prepare uterus for embryo implantation; maintain pregnancy
All three found in both males/females, but in different proportions.
Sexual Reproduction
Mechanisms of Sexual Reproduction
• Internal fertilization
+ requires cooperative behavior
+ requires sophisticated reproductive equipment
+ usually produces fewer zygotes
+ provide more parental protection
• External fertilization
+ requires moist environment
+ timing is more important
- courtship behavior or pheromones
Mammalian Reproduction
Male Reproductive System
Reproductive Anatomy of the Human Male
• testes (sing. testis)
+ male gonads; highly coiled tubes
- seminiferous tubules
• scrotum
+ fold of the body wall that holds the testes
- must be kept 2° below normal body temp.
• epididymis
+ 6 meter long tubule extending from seminiferous tubules
• vas deferens
+ vasectomy
• ejaculatory duct
+ joins the two vas deferens
• urethra
+ tube that drains both the excretory/reproductive systems
• accessory glands
+ seminal vesicles, prostate, bulbourethral glands
Mammalian Reproduction
Female Reproductive System
Reproductive Anatomy of the Human Female
• ovaries
+ female gonads; follicles and corpus luteum
- all eggs formed before birth
• oviduct
+ fallopian tubes
• uterus
+ womb
- thick, muscular organ
• cervix
+ neck of the uterus; opens to the vagina
• vagina
+ thin-walled chamber
- birth canal; repository for sperm during copulation
• labia
+ labia minora/majora
- slender skin folds/ridges that enclose and protect vestibule
Human Sexual Response
Four Phases
1. Excitement
+ preparation of vagina/penis for coitus
- vasocongestion and myotonia
+ filling of a tissue with blood and increased muscle tension
2. Plateau
+ continues excitement responses
- female vagina and uterus creates depression
- breathing/heart rate increase
3. Orgasm
+ rhythmic, involuntary contractions of the reproductive structures
- emission/ejaculation
- uterus and vagina contract
4. Resolution
+ reverses the responses of earlier stages
Sperm
Spermatogenesis
Meiosis
• reductive division
+ reduce the number
of chromosomes
+ two successive div.
• Primordial germ cell
+ divide to form
spermatogonia
• Spermatogonia
+ precursors of sperm
+ undergo mitosis
+ mature into primary
spermatocytes
- secondary spermatocytes,
spermatids, sperm
Oogenesis
Conception to Birth
Conception
• fertilization of the egg by a sperm cell
+ usually occurs in the oviduct
- fertilized egg (zygote) makes it way down to uterus
Embryonic Development
Trimesters
• 1st: organogenesis
+ human chorionic gonadotropin (HCG)
- maintains secretion of progesterone/estrogen
Egg Activation
Fertilization
1. Sperm binds to
receptors on egg surface
2. Migrates through zona
pellucida
3. Sperm reaches egg
membrane
4. Membranes fuse
5. Cortical reaction occurs
and egg blocks other
sperm from entering
Embryonic Development
Cleavage: succession of rapid
cell divisions
• blastomeres
• poles: animal/vegetal
+ vegetal has more yolk
• morula (mulberry)
+ blastocoel forms
- blastula
Patterning
• gastrulation
+ cells organize themselves in
layers/masses
- germ layers
+ ectoderm, mesoderm,
endoderm
Differentiation
• organogenesis
+ organ development
- folds, splits, clustering
+ notochord/neural tube
Growth
• mitosis
+ Morphing Embryo
Cellular and Molecular Basis