Biology Unit 4.1.3- Hormones

insulin regulations
1. Control of insulin regulations....
  1. 1. cell membrane of beta cell containes Ca2+ and K+ channels
  2. 2. K+ channels normally open, Ca2+ closed. K+ diffuse out of cell, inside is more -ve, at rest, potential difference is -70mV
  3. 3. glucose concentration higher outside, glucose diffuse into cells
  4. 4. glucose use metabolism to produce ATP
  5. 5. excess ATP causes K+ channels to close
  6. 6. K+ no longer diffuse out, aters potential difference across membrane (less negative inside
  7. 7. change in potential difference = Ca2+ channels to open
  8. 8. Ca2+ enter and cause secretion of insulin by making vesicles containing insulin and released exocytosisly
2. Diabetes Mellitus
  1. disease in which blood glucose concentrations cannot be controlled effectively
  2. hyperglycaemia- increased concentration of blood glucose
  3. hypoglycaemia- decreased concentrations of blood glucose
  4. Type 1 diabetes
    1. insulin dependent diabetes, starts in childhood
    2. autoimmune response- body immune system attacks own beta cells and destroys it
    3. viral attack
    4. cannot manufacture sufficient insulin and cant store excess glucose as glycogen
    5. Treatment
      1. insulin injections
      2. blood glucose concentration monitored for correct glucose concentration injections
  5. Type 2 diabetes
    1. Non insulin dependent diabetes
    2. can still produce insulin but as people age, responsiveness to insulin declines secretion of insulin via beta cells may decrease.
    3. obesity, diet, asian, African Caribbean, family
    4. Treatment
      1. controlled diet
      2. insulin injections- slow down absorption of glucose
Endocrine System
1. signaling by using hormones
  1. uses blood circulation to transmit signals
  2. hormones are signals released by the system- act as messengers
2. endocrine gland and exocrine gland
  1. endocrine- secretes hormones directly into blood, no ducts
  2. exocrine- gland that secretes molecules into a duct that carries the moecule to where that are sued- has ducts
3. Targeting the signal
  1. complementary receptors on target cells
  2. hormones can travel in blood without affecting any other cells because they have certain receptors
  3. target tissue- many similar cells together that have the same receptor on their plasma membrane
4. nature of hormones
  1. protein/peptide hormones (adrenaline, insulin, glucagon)- not soluble in phospholipid membrane so dont enter the cells
  2. steroid hormones- sex hormones: can go through membrane and can have a direct affect on the DNA/nucleus
5. Action of Adrenaline
  1. 1. adrenaline in blood binds to specific receptors on membranes (first messenger transmits signals around body
  2. 2. when binded, activates adenyl cyclase which is found on the inside of the membrane
  3. 3. adenyl cyclase converts ATP-> cyclic AMP (cAMP)
  4. 4. cAMP causes an affect on the inside and activates enzymes
6. Functions of adrena glands- found above kidneys, adrenal medula is the centre of the gland. adrenaline produced in response to stress and affects include:
  1. relax smooth muscle (bronchioles)
  2. increase stroke vol of heart
  3. vasoconstriction- raise BP
  4. stimulates glycogen -> glucose
  5. increase heart rate
  6. pupil dilation
  7. increase mental awareness
  8. erect body hairs
  9. Adrenal cortex (cholesterol to produce steroid hormones
    1. mineralocorticoids- cpncentration of Na+ and K+ in blood- aldosterone
    2. glucocorticoids- metabolism of carbs and proteins in liver
Regulation of blood glucose
1. Pancreas- small organ lying below the stomach- has both exocrine and endocrine functions
2. Secretion of enzymes
  1. digestive enzymes (exocrine function). cells are found in small groups surrounding tiny tubules into which they secrete the digestive enzyme
  2. Pancreatic duct- tubules join to create this. carries the fluid containing the enzymes into the first part of the small intestine. fluid consists of:
    1. Amylase (carbohydrates)
    2. Trypsinogen (inactive protease)
    3. lipase
    4. sodium hydrogen carbonate- make solution alkaline- neutralise contents of digestive system that have just left the acidic stomach
3. Secretion of hormones
  1. Islet of langerhans- small patches of tissue in the pancreas with an endocrine function. they contain different types of celll:
    1. a (alpha) cells- manufacture and secrete glucagon. glucagon causes blood glucose to rise.
    2. B (beta) cells- manufacture and secrete insulin. insulin causes blood glucose levels to drop
4. normal blood glucose concentration: 90mg100cm-3/ between 4 and 6 mmoldm-3
5. if rises too high
  1. target cells = liver cells (hepatocytes), muscle cells, brain. these possess specific membrane bound receptors.
  2. effects of insulin...
    1. more glucose channels, therefore more can enter the cell
    2. glucose to glycogen (glycogenesis) for storage
    3. glucose to fats
    4. glucose used in respiration
    5. lowers blood glucose concentration
6. If drops too low
  1. target cells- liver cells (hepatocytes)- has specific receptors fro glucagon
  2. effects of glucagon...
    1. glycogen to glucuse (glycogenolysis)
    2. use of fatty acids in respiration
    3. glycogenesis- production of glucose by converting amino acids and fats
control of hear rates in humans
1. The human heart- cell metabolism- result of all the chemical reactions taking place in the cytoplasm
2. how the heart adapts to supply more oxygen and glucose
  1. heart increases strength of contractions
  2. increase volume of blood pumped per heart beat
  3. increased heart rates
3. control of heart rate
  1. myogenic- muscle tissue can initiate own contractions
  2. pacemaker//SAN- region of tissue that can initiate an action potential which travels as excitation over atria walls through AVN and down purkyne tissue to ventricles
  3. Medulla oblongata- found at the base of the brain. co ordinates unconscious functions of body like breathing and heart rate
    1. connected to SAN
    2. affects frequency of contractions
4. interactions between control mechanisms
  1. at rest- heart rate controlled by SAN (60-80 bmp)
  2. cardiovascular centre- specific region in medulla oblongata that receives sensory inputs about levels of activity, carbon dioxide concentrations and blood pressure. sends nerve impulses to SAN to alter frequency
5. Factors that affect hear rate
  1. movement of limbs detected by stretch receptors in muscles, increase heart rate sends impulses to cardiovascular centre
  2. change in pH detected by chemoreceptors send impulses. increase heart rate
  3. CO2 reduces activity of accelerator pathway, decreases pathway
  4. Adrenaline secreted in response to stress, shock, anticipation or excitement. presence increases heart rate

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Biology Unit 4.1.3- Hormones

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