bio

• Endocrine System


  Regulates the activity of other organ systems to maintain homeostasis
• Homeostasis


  Bounded internal conditions in face of large environmental variation
• Homeostatic control


  Requires systems that can make adjustments based on changing environment
• Hormone


  Chemical messengers secreted by endocrine glands, responsible for specific regulatory effects on certain cells, tissues, or organs
• Synaptic Transmission


  • Presynaptic neurons
  • Postsynaptic neurons
  • Synaptic vesicles
  • Neurotransmitters
  • Inhibitory vs excitatory
  • Summation

  
• Hormones


  • Most circulate in blood and act at a distance by binding to specific receptors on target cells
  • Some act locally on cells without entering blood
  • Prostaglandins in semen stimulates uterine contractions
  • Inactivated in liver and excreted by kidneys
• Skeletal muscle contraction


  • Actin
  • Myosin
  • Muscle fibers
  • Sarcomere
• Hormone signaling


  • Target cells have receptors - protein molecules that recognize and bind to specific hormones
  • Cells other than target cells lack the correct receptors and are unaffected by the hormone
• Water-soluble hormones


  Function as cell surface signaling molecules
• Skeletal muscle contraction


  1. Nerve impulse arrival

  2. Calcium ions flow into muscle cell

  3. Myosin binds to actin

  4. Myosin swivels and pulls thin filaments
• Lipid-soluble hormones


  Function as intracellular signaling molecules
• Water soluble hormones


  Action is RAPID
• Skeletal muscle relaxation


  1. Calcium channels close

  2. Calcium pumps remove calcium

  3. Troponin-tropomyosin complex slides back
• Mechanism of action for water soluble hormones

  1. Hormone (1st messenger) binds to receptor on surface of target cells

  2. Inside cell: ATP -> cyclic AMP (cAMP) (2nd messenger)

  3. 2nd messenger activates a cascade-like series of enzymatic reactions

  4. Enzymes role in metabolic reactions changes activity of the target cell
• Central Nervous System (CNS)

  • Composed of brain and spinal cord
  • Receives sensory input
  • Transmits effector response
• Water soluble hormones


  • Modified amino acid hormones: epinephrine
  • Peptide hormones: oxytocin, insulin
• Lipid soluble hormones


  Action is SLOW but lasts longer
• Structures protecting the CNS

  • Scalp
  • Skull and vertebrae
  • Meninges
  • Cerebrospinal fluid
  • Blood-brain barrier
• Mechanism of action for lipid soluble hormones

  1. Hormone moves from blood and diffuses into target cell

  2. Hormone binds to and activates nuclear receptor: triggers a change in gene expression (i.e., binds to DNA to turn gene on or off)

  3. DNA -> mRNA leaves nucleus -> protein (enzyme)
• Spinal cord


  • Two-way conduction pathway
  • Center for reflexes
  • Begins at medulla oblongata
  • Exits at foramen magnum
  • Same meningeal coverings as brain
  • Entry/exit points for spinal nerves
• Lipid soluble hormones


  • Steroid hormones: Testosterone, Estrogen
  • Thyroid hormones T3 and T4
• Endocrine structures


  • Pituitary and Hypothalamus
  • Thyroid
  • Parathyroid
  • Adrenal
  • Other structures
• White matter


  Tracts of myelinated axons communicating PNS with brain

  
• Pituitary gland


  Initially called "master" gland, secretes hormones that control other glands. However, the pituitary gland is controlled by hypothalamus!
• Grey matter


  • Composed of cell bodies and axons devoid of myelin
  • Involved in reflexes
• Posterior pituitary


  Made of nervous tissue extending from the hypothalamus, stores and secretes hormones made by the hypothalamus
• Hormones secreted by posterior pituitary

  • Antidiuretic hormone (ADH): Decreases urine volume, decreases perspiration, increases blood pressure
  • Oxytocin: Secreted during and after childbirth, increases uterine contractions, stimulates milk "let-down"
• Meninges


  • Soft coverings that protect the brain
  • 3 connective tissue membranes: Dura mater, Arachnoid mater, Pia mater
• Anterior pituitary


  Not made of nervous tissue, but glandular tissue (makes its own hormones)
• Hormones secreted by anterior pituitary

  • Thyroid stimulating hormone (TSH)
  • Adrenocorticotropic hormone (ACTH)
  • Prolactin (PRL)
  • Growth hormone (GH)
  • Follicle stimulating hormone (FSH)
  • Luteinizing hormone (LH)
• CSF (Cerebrospinal fluid) is involved in meningitis
• Targets of anterior pituitary hormones

  • Thyroid (stimulated by TSH)
  • Adrenal cortex (stimulated by ACTH)
  • Mammary glands (stimulated by Prolactin)
  • Bones and tissues (stimulated by GH)
  • Ovaries and testis (stimulated by FSH and LH)
• Brain functions


  • Homeostasis: Breathing, temperature, heartbeat
  • Higher mental functions: Consciousness, Language, Memory
• Growth hormone


  • Metabolic effects: Mobilizes fat stores and conserves glucose
  • Growth effects: Indirect, through insulin-like growth factors, stimulates nutrient uptake, formation of proteins, and deposition of bone matrix, targets bone and skeletal muscle, increased cartilage formation and skeletal growth, increased muscle mass
• Prolactin


  Stimulates milk production in breasts, structurally similar to GH
• Brain structures


  • Brain stem: Midbrain, Pons, Medulla oblongata
  • Diencephalon: Thalamus, Hypothalamus
  • Cerebellum
  • Cerebrum
• Thyroid gland


  Largest purely endocrine organ in the body, found at the base of the throat, consists of two lobes connected by the isthmus
• Midbrain


  • Responsible for relay between cerebrum and spinal cord or cerebellum
  • Loss of neurons associated with Parkinson's disease
  • Controls sleep and alertness (Reticular Activating System)

  
• Hormones produced by thyroid gland

  • Thyroid hormone
  • Calcitonin
• Reticular Activating System (RAS) filters important information from the surrounding environment