P3 and P4

• The hypothalamic region regulates food intake

  Where the ventrolateral nuclues (feeding) stimulated by hunger and hyperphasia and the ventromedial nuclues for satiety stimulated by fullness
• Anorexia causes damage to ventrolateral nuclues while hyperphagia causes damage to ventromedial nuclues
• When the stomach extends the impulse is carried by the vagus nerve to nuclues tractus soliatrius (fullness) then the food is in duodenum ( CCK and peptide yy) are released sending an excitaroty signal to vagus nerve
• concentration of glucose amino acids and fatty acids in the blood sends signals to VMN in hypothalamus
• When fasting ghrelin is secreted VLN is stimulated - hunger
• If youre fat, adipose tissue produce lectin which inhibits ghrelin
• Fluid intake is regulated in the the thirst centre which is located in the anterolateral region of the hypothalamus - thirst feeling when there is an increase in the plasma osmolality (hypothalamic osmoreceptor) decreased salivation (oropharyngeal osmoreceptor) and decrease in blood volume
• 2 muscles that open the mouth temporalis and lateral pterygoid
• 2 muscles that close the jaw masseter and medial pterygoid
• Automatic pharyngeal muscle contraction,

  1. soft palate up to prevent the reflux of food to nasopharynx
  2. Palatopharyngeal folds are pulled medially to approximate each other forming a sggital slit
  3. Vocal cords are tensed
  4. Larynx is pulled upward and anteriorly by neck muscles
  5. Epiglottis swings backward over the opening or larynx
• The upper esophageal sphincter is made from 2 muscles

  1. inferior pharyngeal constrctor muscle
  2. Cricopharyngeus muscle
• UES and swallowing

  Resting - high vagal tone UES is closed

  Swallowing - low to none vagal tone UES is open
• Esophagus upper 1/3 - straited muscle

  the motor supply is nuclues ambigous > vagal nerve > axon terminus > Ach > Nictonic receptors > contraction only
• Esophagus lower 2/3 - smooth muscle

  pathway: Dorsal motor nuclues > myenteric plexus >

  1. Inhibitory > NO and VIP
  2. Excitatory >Ach and Substance P
• LES opens up by NO and VIP
• Secondary preistalsis clears esophagus when there is residual

  1. upper >vagovagal reflex
  2. lower > peristaltic reflex
• Achlasia is a dilated esophagus since the LES isnt relaxing for the bolus to go through giving a birds beak apperaence

  No actual cause but theory is that its an autoimmune disorder of the enteric system
• Factors that contirbute to LES competence / Tone

  1. Tonic contraction (Ach and Substance P) of circular muscle fibres
  2. Oblique gastro-esophageal angle forms mucosal flap- valve emchanism
  3. Crura of th diaphgram forms pinch-cock mechanism
  4. Positive intra-abdominal pressure
• To increase LES tone

  Increase Intraabdominal pressure

  Decrease intrathoracic pressure

  Cough/sneezing > chronic cases > damage

  Gastrin, motilin, alpha-adrenergic stimulation
• To decrease LES tone

  Secretin, glucagon, VIP, GIP, progestrone
• Parotid gland gives off serous fluid (protein, water and electrolytes)
• Sub- lingual and mandibular gives off viscous fluid which has mucins in serous secretions
• In the acini saliva is isotonic because its the site of production but when it enters the striated duct it becomes hypotonic as Na+ and Cl- are absorbed and K+ and HCO3- are secreted
• Channels in straited duct:

  1. Na+ is aborbed back into the blood via Na+/K+ pump
  2. Cl- aborbed and HCO3- secreted via exchanged fueled by CFTR
  3. HCO3- enters using HCO3- Na+ cotransporter
  4. K+ is secreted where more Na+ Cl- absorbed than K+ HCO3- secreted
• Stimulants to glands

  1. Mainly parasympathetic - Ach > water and salts > where parotid is supplied by glossopharyngeal and the subs is by facial nerve
  2. Sympathetic - norepinepherine in the superior cervical ganglion T1 to T3 through cAMP > exocytosis of music and amalyase
• Enzymes found in saliva

  alpha-amylase  - initiates starch digestion – ≤ 5 % carbohydrate digestion

       lingual lipase - initiation of lipid digestion – more important in newborn infants
• Antimicrobials found in saliva

       lactoferrin – binds iron – deprives microorga­nisms of nutrient iron

       lysozyme - hydrolyzes the components of  bacterial cell wall – destroys them

       lactoperoxidase – oxidizes various substrates by H2 O2 - potent bactericidal activity
• Mucin - primary determinant of salivary viscosity – adheres to food particles - lubrication
• Miscellaneous in Saliva

       haptocorrin – binds to dietary vitamin B12 – prevents its degradation in stomach

       growth factors - stimulate epithelial cell proliferation and differentiation, and promote wound healing
• Atropine stops Ach effect