Biological Rhythms

Question 1

describe ultradian, circadian and infradian rhythms

Answer 1

• ultradian = < 1 day to complete a cycle
  
  • respiration, heart rate
• circadian = approx. 1 day to complete a cycle
  
  • sleep-wake cycle
• infradian = > 1 day to complete a cycle
  
  • menstrual cycle

Question 2

describe the pre-Botzinger complex

Answer 2

the pre-Botzinger complex located in the medulla is the respiratory rhythm generator and is the primary source of rhythmic inspiratory excitatory drive

the pre-Botzinger complex activates the rostral VRG which then activates the phrenic motor nucleus to cause diaphragm contraction

Question 3

describe the Botzinger complex

Answer 3

the Botzinger complex located in the medulla modulates expiration and activates the caudal VRG which contains expiratory neurons, which then goes to the intercostals

Question 4

describe the pneumotaxic center (pontine respiratory group)

Answer 4

located in the pons and is essential for maintaing normal breathing pattern; inhibits apneusitc center

Question 5

describe the apneustic center

Answer 5

the apneustic center is located in the lower pons; tonic facilitation of inspiration by excitatory input to pre-Botzinger complex

Question 6

contrast the dorsal respiratory group (DRG) and the pontine respiratory group (PRG)

Answer 6

• DRG
  
  • signals ventral respiratory group
  • integrates peripheral signals
  • receives visceral afferents
• PRG
  
  • signals ventral respiratory group
  • fine tunes breathing rhythm in sleep, speech and exercise

Question 7

describe hypothalamic control over respiration

Answer 7

• signals ventral respiratory group
• pain, strong emotion influence breathing rate and depth
• increased temp. increases breathing rate

Question 8

describe cortical control of respiration

Answer 8

• motor cortex bypasses medulla
• voluntary control of breath (but overriden by brainstem monitoring)

Question 9

describe where this lesion is and what the abnormal respiration is called

Answer 9

Question 10

describe where this lesion is and what the abnormal respiration is called

Answer 10

Question 11

describe where this lesion is and what the abnormal respiration is called

Answer 11

Question 12

describe where this lesion is and what the abnormal respiration is called

Answer 12

Question 13

explain what is occurring in this image

Answer 13

Question 14

describe the purpose of the suprachiasmatic nucleus

Answer 14

• daytime
  
  • light activates photo-sensitive cells in the retina
  • retino-hypothalamuc tract fibers synapse in the suprachiasmatic nulceus of the hypothalamus and reset the circadian clock
• nighttime
  
  • the suprachiasmatic nucleus provides neuronal output to the paraventricular nulceus of the hypothalamus
    
    • these fibers then innervate the pineal gland to produce melatonin

Question 15

explain the relationship between the suprachiasmatic nulceus to peripheral oscillators

Answer 15

• The SCN communicates with and synchronizes local clocks in other tissues, including peripheral tissues and extra-SCN regions of the brain
  
  • cardiovascular clocks - blood pressure, thrombogenesis
  • stomach/GI clocks - glucose tolerance, lipid metab.
  • adrenal clocks - glucocorticoid release

Question 16

describe jet lag (desynchronosis)

Answer 16

• transient disorder (after a flight crossing several time zones rapidly) associated with excessive daytime sleepiness, sleep onset insomnia and frequent arousals from sleep
• reflects mismatch between light/dark stimuli and the circadian clock
• SCN resets to local time in around one day based on light signals, but peripheral oscillators can take more than a week to adjust

Question 17

sleep-wake disorder frequently occur in ____ individuals whose circadian rhythm is free running due to the lack of ______

Answer 17

sleep-wake disorder frequently occur in blind individuals whose circadian rhythm is free running due to the lack of visual input (zeitgeber)