anatomy lecture 10 seph

• nervous system:

  • rapid communication using electrical signals
  • releases neurotransmitters into synapses (few targets)
  • produce shorter-term effects
• endocrine system:

  • slower communication though the blood
  • multiple distant targets
  • produce longer-term effects on physiology of the target
• Endocrine sytem:

  
• functions of the endocrine system:

  • hormone control within cells
  • reproduction - estrogen and testosterone
  • growth and development - insulin and growth hormone
  • mobilization of body defenses - thymus hormone works with T cells
  • maintenance of homeostasis
  • regulation of metabolism - thyroid - growth and development, and cortisol = long-term stress hormone
• receptor specificity:

  • ability for a cell to respond to the fit of a hormone
  • lock and key concept
• receptor affinity:

  • strength or tightness of the binding between a cell and hormone
  • (how tight the fit is)
• hormone agonist:

  • allows chain of events to occur in the cell (from the hormone entering and doing random shit)
• hormone antagonist:

  • oppose or reverses the effects of another hormone
  • example: inulin and glucose
• synergistic effect:

  • 1 + 1 = 32
  • 2 hormones with similar effects amplify the effects
  • example = epi and glucagon in fight or flight
• hormone control:

  • down-regulation: decreased number of receptors on a cell, for example, prolonged effects of increased insulin levels will decrease sensitivity of cells
  • up-regulation: increase the number of receptors for a hormone on the surface of a target cells - to enhance cellular response to a particular hormone, example: towards the end of pregnancy, the body will increase the number of receptors for oxytocin for labour
• permissiveness:

  • one hormone being mandatory for other hormones to work
  • example: thyroid hormone for reproduction hormone to function properly
• Gland type:

  • endocrine glands - ductless glands that empty hormonal products directly into the blood
  • exocrine glands - glands that have ducts and deliver secretions to a body's surface
  • mixed glands - glands or organ that secretes products both into the blood stream and onto a body surface
• types of signaling:

  • short = across jap junctions, connected neighboring cells example = paracrine signaling
  • long = endocrine into blood/ extracellular fluid, spreading though blood in limbic system
• hormone action:

  • receptors present on cells' plasma membrane or present in the anterior
  • target cells = must have specific protein receptors
  • hormones circulate to all tissues, and will active with target cells
• chemistry of hormones - classified as:

  • amino acid based = second messengers, protein-based, not able to get though plasma membrane (hydrophilic) so they use second messengers
  • steroids = lipid-based, so can get through theplasma membrane,,
  • prostaglandins = lipid-based, can get through plasma membrane, local hormones produced by all cell in the body, response to local chemical stimuli, blah blah blah
• steroid based = lipid soluble, can pass through plasma membranes easily, hydrophobic
• prostaglandins:

  • inhibit platelet aggregation
  • can dilate, constrict bronchioles
  • local vasodilation
  • can promote pain response
  • produced on the site they are needed
• hormone action cellular:

  • change membrane permeability - by opening ion channels, from the help of aldosterone, insulin, epi
  • activate/ inactivate enzymes - insulin, breaking down glycogen
  • stimulate/ inhibit cell division - growth hormone
  • promote/ inhibit secretion - tropic hormones, hormones promote the thyroid to bind certain hormones
  • turn on off gene transcription - erythropoietin - turn off on for protein synthesis
• hormone action: - hormones imitate their effects by:

  • direct gene activation - steroids and prostaglandins
  • second - messenger - amino acid hormones
• direct gene activation steps:

  1. diffused through plasma membrane of target cells
  2. binds to specific hormone receptor
  3. hormone - receptor complex binds to specific sites on cells DNA
  4. specific genes activated to create messenger RNA
  5. mRNA is translated in the cytoplasm
  6. new proteins are synthesized
• second messenger activated:

  1. hormone (first messenger) binds to a receptor protein plasma membrane
  2. activated receptor initiates reactions that activate an enzyme
  3. enzyme catalyzes a reaction that produces a second messenger molecule (such as cyclic AMP)
  4. seconds messenger molecule is involved in additional charges promoting desired response
• hormone level regulation:

  • regulated by negative feedback, example - rising blood sugar levels
• hormone release regulation

  • hormonal - hormones releasing hormones - low shit, = stimulus = hypothalamus stimulates anterior pituitray gland = to secrete hormones = shit becomes high = homeostasis
  • humoral - local monitoring/ response to blood stuff levels -
  • neural - direct neural communication - preganglionic sympathetic fiber stimulus activates medulla cells - to secrete catecholamines (epi/ NE)
• what does the posterior pituitary gland release?

  • oxytocin - released during childbirth and nursing
  • antidiuretic hormone - released during decreased h2o concentration of blood, and low blood volume or pressure (to increase blood pressure)
• anterior pituitary gland hormones

  • growth hormone - (GH) bones and hormones
  • prolactin - (PRL) - mammary glands
  • follicle-stimulating hormone (FSH) - testes and ovaries - gonadotropic hormone
  • luteinizing hormone - testes and ovaries - gonadotropic hormone
  • thyrotropic hormone - (TH) - thyroid hormones that regulate BP, body temp, HR, metabolism, and the reaction of the body to other hormones
  • adrenocorticotropic hormone - (ACTH)
• pineal glands - hangs from 3rd ventricle of the brain where the CSF fluid is and the plexus, also part of the epithalamus

  • melatonin secretion
• thyroid gland

  • inferior to epiglottis and superior to trachea
  • the hormones are thyroxine and triiodothyronine T3, T4
  • regulated by thyroid-stimulating hormone
  • thyroid can store up to 3-4 months of t3, and t4
  • also has calcitonin
• calcitonin - the hormone in the thyroid gland to helps regulate calcium levels in the blood by decreasing it

  • decreases calcium levels in the blood
  • but increases calcium levels in bones
  • slows osteoclasts and and releases osteoblasts
• parathyroid glands:

  • parathyroid hormone (PTH) released
  • antagonist gland to calcitonin
  • increases calcium absorption in the blood, therefore less calcium in the bones therefore less bone making therefore less osteoblasts (bone-making cells), and therefore more osteoclasts.
• Bone remodeling:

  • adult one undergoes remodeling
  • osteoclasts remove old damaged bone and osteoblasts lay new bone in response to blood ca+ levels
  • controlled by: growth hormone, thyroid hormone, estrogen, testosterone, some stress hormones
• thymus: a lymphoid organ situated in the neck of vertebrates that produces T-lymphocytes for the immune system. The human thymus becomes much smaller at the approach of puberty.

  • releases thymosin
  • above heart
  • kids learn to fight sickness and then one trick ponies (t cells) are there when need to refight sickness
• adrenal glands: consists of adrenal medulla, and adrenal cortex

  1. adrenal cortex: on the outside

  • produces: steroid hormones such as cortisol, aldosterone, and androgens
  • cortisol - plays a role in regulating metabolism, reducing inflammation, and controlling sleep-wake cycles
  • aldosterone helps regulate blood pressure and electrolyte balance
  • androgens are sex hormones that contribute to the development of the male and female characteristics

  2. adrenal medulla: inside

  • produces non- steroid hormones called catecholamines, including adrenaline (epi) and NE
  • involved in fight or flight
• adrenal medulla - epi short-term stress response

  • increases heart rate
  • increased blood pressure
  • liver converts glycogen to glucose and releases glucose to the blood
  • dilation of bronchioles
  • changes in blood flow patterns leading to increased alertness and decreased digestive and kidney activity
  • increased metabolic rate
• adrenal medulla - NE - short term stress response primary constrictor of smooth muscles

  • increased heart rate
  • increased blood pressure
  • The liver converts glycogen to glucose and releases glucose into blood
  • ....................... same as other slide on EPI
• adrenal cortex- outside

  1. zona glomerulosa (outermost layer)

  • mineralocorticoids such as the hormone aldosterone - changes on minerals - sodium, potassium, chloride, calcium,

  2. zona fasciculata (middle layer)

  • glucocorticoids such as the hormone cortisol - affect blood glucose levels and visibility

  3. zona reticularis (inner layer of cortex)

  • sex hormones such as androgens - estrogen and testosterone
• adrenal gland layers:

  
• aldosterone secretion: reduces in response to high blood potassium

  • regulates the reabsorption of sodium and excretion of potassium
  • renin-angiotensin in zona glomerosa (the crusty exterior )
  • ANP - inhibits zona glomersula - promoting aldosterone
• RAAS: aldosterone

  • renin is secreted by JGA
  • renin + angiotensinogen = angiotensin 1
  • angiotensin 1 + angiotensin converting enzyme (ACE) = angiotensin 2
  • angiotensin 2 stimulates the release of aldosterone and vasoconstriction
  • angiotensin 2 increases sodium chloride and water reabsorption at the kidney, and causes the adrenal cortex to release aldosterone
• adrenal cortex glucocorticoids:

  example of hormone: cortisol

  • essential for survival, stress hormones synergistic with catecholamines cleared by liver, excreted by kidneys

  
• adrenal cortex - glucocorticoids

  example: cortisol and cortisone

  • long term stress
  • na and h2o water retention
  • increased blood volume and BP
  • gluconeogenesis
  • increased blood glucose
  • immunosuppression - because cortisol has a potent anti-inflammatory and immunosuppressive effect (short-term immunosuppressant is good to help with inflammation decrease during stress but prolonged can have risks)