E109 Final

  1. homeostasis
    the property of a system that regulates its internal environment and tends to maintain a stable, constant condition of properties
  2. componests of a control system
    • stimulus
    • sensor
    • integration center
    • set point
    • effector organ
  3. feed-forward control
    • a control system which has only feed-forward behavior responds to its control signal in a pre-defined way without responding to how the load reacts
    • characteristically, is fast and simple, and response is not modulated
  4. negative feedback control
    • a control system that acts when a gap between the actual value and a reference value of a system parameter is used to reduce the gap
    • characteristically, slow and complicated, and response is modulated
  5. postive feedback control
    • positive feedback is a process in which the effects of a small disturbance on a system can include an increase in the magnitude of the perturbation
    • characteristically, is very fast
    • requires an external shutoff
  6. thermoregulation - low body temperature
    • when body temperature gets below lower threshold, two paths are -
    • 1) detection by cutaneous thermoreceptors leads to shivering in skeletal muscles via somatic motor neuron from hypothalmus
    • 2) if blood gets too cold, detection by hypothalmic thermorecptors leads to vasocontriction of cutaneous blood vessels via sympathetic neurons
  7. thermoregulation - high body temperature
    • when body temperatur gets above higher threshold, two paths are-
    • 1) detection by cutaneous thermoreceptors leads to sweat release from sweat glands via sympathetic neurons
    • 2) if blood gets too hot, detection by hypothalmic thermoreceptors leads to vasodilation of cutaneous blood vessels via sympatheric neurons
  8. changing set points
    • set points can change throughout the day
    • for example, body temperature set point can rise during the day and lower at night
    • circadian rhythms are any biological process that displays an endogenous, entrainable oscillation of about 24 hours
  9. spinal cord anatomy
    • dorsal root ganglion
    • autonomic ganglion
    • dorsal and ventral horn
    • white and gray matter
  10. dorsal root ganglion
    the dorsal root houses the cell bodies of neurons in afferent spinal nerves of the PNS
  11. gray matter vs white matter
    • gray matter is unmylinated
    • white matter is mylinated
    • ascending and descending tracts run through white matter
  12. thalamus
    serves as the integrating center and relay station for sensory and motor signals
  13. hypothalamus
    serves as the integrating center for thermoregulation and homeostasis
  14. adrenal medulla
    • specialized endocrine tissue associated with the sympathetic nervous system
    • secretes primarily epinephrine which activates B1 and B2 receptors on target cells
  15. adreneric receptors - 3 types
    • adreneric receptors are a class of G protein-coupled receptors that are targets of catecholamines, especially norepinephrine and epinephrine
    • alpha
    • beta1
    • beta2
  16. sensitivity of adreneric receptors
    • alpha - norepinephrine
    • beta1 - norepinephrine and epinephrine
    • beta2 - epinephrine
  17. two divisions of nervous system
    • central nervous system - brain and spinal cord
    • peripheral nervous system - neurons outside the CNS
  18. divisions of the peripheral nervous system
    • two main divisions - somatic and autonomic
    • three divsions of the autonomic system -
    • 1) sympathetic
    • 2) adrenal sympathetic
    • 3) parasympathetic
  19. somatic efferent pathway (skeletal muscle)
    • interneuron runs from brain in white matter to motor neuron, synapsing at the ventral horn
    • motor neuron releases ACh at synapse with skeletal muscle, which has nicotinic receptors sensitive to ACh
  20. autonomic efferent pathway (smooth muscle)
    • interneuron runs from brain in white matter to another interneuron, synapsing at the ventral horn
    • ACh and nictotinic receptor activate interneuron at autonomic ganglion
    • interneuron innervates with smooth muscle, releasing norepinephrine which activates adreneric receptors (a type of G-protein coupled receptor)
  21. efferent pathways - overview
    • Image Upload 1both sympathetic and parasympathetic preganglionic neurons release ACh onto nicotinic receptors on the postganglionic cell
    • most postganglionic sympathetic neurons secrete NE onto adreneric receptors on target cell
    • most postganglionic parasympathetic neurons secrete ACh onto muscarinic receptors on target cell
  22. norepinephrine
    • released by postganglionic sympathetic neurons  
    • activates alpha and beta1 receptors
    • alpha receptors allow for localized response
  23. epinephrine
    • released by adrenal medulla
    • activates beta1 and beta2 receptors
    • beta2 receptors allow for systemic response
  24. parasympathetic efferent pathway
    • interneuron innervates with another interneuron in the autonomic ganglion, releasing ACh which activates nicotinic receptors
    • this interneuron innervates with smooth muscle, releasing ACh which activates muscarinic receptors, a type of cholinergic receptor
  25. sympathetic vs parasympathetic - effects on bodily functions
    • sympathetic -
    • 1) increase heart beat frequency and stroke volume
    • 2) increase or decrease arteriole diameter
    • 3) increase bronchiole diameter
    • 4) decrease GI motility
    • 5) decrease endocrine pancreas insulin secretion
    • 6) decrease exocrine pancreas enzyme secretion
    • 7) increase sweat secretion from sweat glands
    • 8) decrease urination from bladder
    • 9) responsible for ejaculation in males
    • parasympathetic -
    • 1) decrease heart beat frequency
    • 2) decrease bronchiole diameter
    • 3) increase GI motility
    • 4) increase endocrine pancreas insulin secretion
    • 5) increase exocrine pancrease enzyme secretion
    • 6) increase urination from bladder
    • 7) responsible for erection in males
  26. autonomic brain centers - functions
    • hypothalamus - thermoregulation, water balance, eating behavior
    • pons (upper brainstem) - bladder control, blood pressure control, respiratory control
    • medulla oblongata (lower brainstem) - respiratory control
  27. reflex
    an involuntary and rapid response to a stimulus
  28. patellar tendon reflex
    • part of somatic nervous system
    • example of a monosynaptic reflex
    • stimulus of hammer hitting knee causes a stretch in the patellar tendon
    • stretch is detected by muscle spindle organ
    • integration center at the spike initiating zone of the efferent neuron
    • efferent neuron innervates with two skeletal muscles, causing quad to contract and hamstring to relax
    • can still feel the stimulus because an interneuron sends a signal to the brain, in particular the somatic sensory cortex
    • example of feed-forward control since the efferent response does not vary with afferent input
  29. urination or micturition reflex
    • part of parasympathetic nervous system
    • example of polysynaptic reflex
    • as urine fills bladder, bladder walls increase in tension
    • increased tension is sensed by stretch receptors which and activates two interneurons in the dorsal horn
    • one interneuron activates a motor neuron and other activates a parasympathetic neuron
    • first internueron inhibits the motor neuron (which usually has a train of APs aka tonic activity via somatic pathway) that maintains tension in the external sphincter, a skeletal muscle; result is relaxation and opening of this sphincter
    • other interneuron activates parasympathetic neuron, which then activates smooth muscle of bladder, causing it to contract or squeeze
    • both micturition reflex pathways can be inhibited by descending signals from the brain, an ability that is undevelpoed in infant
    • sympathetic nervous system can also influence smooth muscle of bladder via N and NE (cannot influence external sphincter because it is skeletal muscle)
  30. change in stored energy - equation
    • change in stored energy = intake or production - excretion or metabolism
    • also be written as - change in stored energy = energy intake - energy used
  31. metabloic pathways for fats, carbs, and proteins
    Image Upload 2
  32. glucose metabolism
    • glucose -> G6P ->glycolysis ->pyruvate
    • if PO2 low, pyruvate goes into lactic acid cycle (anaerobic respiration)
    • if PO2 high, pyruvate goes converted into acetyl CoA within mitochondria (all of the above happens in the cytosol)
    • acetyl CoA -> citric acid cycle -> e- and H+ -> ETC
    • one glucose yields 30-32 ATP molecules in aerobic metabolism
    • fatty acids can enter chain as acetyl CoA
    • process requires O2 and produces CO2
  33. how body controls glucose levels
    • alpha and beta cells of the pancreas serve as sensors and integrating centers for energy balance
    • high plasma glucose activates beta cells, which promotes insulin secretion 
    • low plasma glucose activates alpha cells, which promotes glucagon secretion; low glucose also means beta cells are not stimulated
  34. insulin effects on liver
    • pathways happen via second messenger in the liver
    • glycogenesis - glucose transformed into glycogen
    • lipogenesis - glucose transformed into triglycerides
    • glycolysis - ATP production
    • glucose transport - increased permeability to glucose
    • glycogen and triglycerides can leave liver and circulate to cells and adipose tissue for storage
  35. glucagon effects on liver
    • pathways happen via second messenger in the liver
    • glycogenolysis - glycogen transformed into glucose
    • glyconeogenesis - amino acids transformed into glucose
  36. insulin effects on adipose and muscle
    • pathways happen via second messenger
    • can increase permeability of both to glucose
    • glycolysis and lipogenesis and in the adipose
    • glycolysis, glycogenesis, lipogenesis, and protein synthesis in the muscles
  37. regulating insultin and glucagon levels
    • after a meal (fed state), storage of glucose drops blood glucose levels, so that storage is downregulated in a negative feedback loop
    • without a meal in a while (feed state), release of glucose raises blood glucose, so that release is downregulated in a negative feedback loop  
  38. diabetes
    • type 1 - autoimmunse disease that destroys beta cells; resulting hyperglycemia damages kidneys, eyes, and nervous system
    • type 2 - systemic cells are less sensitive to insulin; also results in hyperglycemia
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E109 Final
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