RS Lec 7 Flashcards
rhythm of breathing is established by
CNS
breathing is initiated in (general) and by
medulla by specialized neurons
breathing is modified by (general)
- higher structures of CNS
- signals from central & peripheral chemoreceptors & mechanoreceptors in lung and chest wall
neural networks establish
automatic rhythm of muscle contraction
groups of respiratory neurons in brainstem (3)
- pqntine respiratory group
- dorsal respiratory group
- ventral respiratory group (VRG)
in VRG, PreBotC generate
excitatory inspiratory rhythmic activity that excite inspiratory muscles via polysynaptic pathway
PreBot C stands for
prebotzinger complex
PreBotC is in
ventral respiratory group
in VRG, pFRG generate
active excitatory expiratory rhythmic activity that excite expiratory muscles via polysynaptic pathway
pFRG stands for
parafacial respiratory group
pRFG is in
ventral respiratory group
Neuronal networks adjust rhythm of breathing to accommodate changes in (4)
- metabolic demands
- varying mechanical conditions (e.g., changing posture)
- non-ventilatory behaviors (e.g., speaking, sniffing, eating)
- pulmonary and non-pulmonary diseases
VRG creates
rhythm of breathing
PreBötC and pFRG neurons drive activity in … that excites
premotor neurons, which excites motoneurons that activate respiratory muscles
neuro-respiratory pathway for diaphragm & ext. intercostal muscles (insp.)
– preBötC→INS premotoneuron (ROSTRAL VRG)→
phrenic & thoracic inspiratory motoneurons (in cervical & thoracic spinal cord)→
DIAPHRAGM (phrenic) & EXT. INTERCOSTAL muscles (thoracic)
neuro-respiratory pathway for tongue & upper airway muscles (insp.)
preBötC→
INS premotoneuron (ROSTRAL VRG & parahypoglossal
region, pXII)→
cranial motoneurons (in medulla)→TONGUE & UPPER
AIRWAY MUSCLES
neuro-respiratory pathway for int. intercostal & abdominal muscles (active exp.)
pFRG→ EXP premotoneurons (caudal VRG)→
thoracic & lumbar expiratory motoneurons (in spinal cord)→
INT. INTERCOSTAL (thoracic) & ABDOMINAL MUSCLES (lumbar)
activity of preBötC neurons may be depressed by (2)
- drugs
ex. anesthetics (propofol) - pain killers (opioids-fentanyl).
Depression of preBötC neurons activity leads to
- respiratory depression
- eventually death for respiratory arrest.
Naloxone does what?
reverse opioids effects
Hypoxia
low PO2
hypercapnia
high PCO2
acidosis
low pH in blood
Chemoreceptors are
- specialized structures that sense changes in
PO2,PCO2 and pH
two types of chemoreceptors
-peripheral and central chemoreceptors
carotid + aortic bodies are
peripheral chemoreceptors
carotid + aortic sinuses are
baroreceptors
Carotid and aortic bodies sense
HYPOXIA (low arterial PO2) but are also sensitive to pH
carotid bodies summary (5)
- extremely small
- chemosensitive
- highly vascularized
- high metabolic rate
- neuron like qualities
PO2, PCO2, and pH in the carotid body capillaries
the same as in the systemic arteries
two types of cells in carotid bodies
- type I/ glomus cells.
- type II/ sustentacular cells
Type II/sustentacular cells
-act as support in the CB
type I/glomus cells
chemosensitive cells of CB
neuron-like characteristics
- Glomus cells have voltage-gated ion channels.
• Depolarization triggers action potentials (their firing rate
increases).
• Glomus cells have numerous intracellular vesicles containing neurotransmitters— acetylcholine, dopamine, norepinephrine, substance P, and met-enkephalin.
• Stimulation causes the release of these neurotransmitters and
controls the firing of the sensory nerve endings.
A decrease in arterial PO2 is the primary stimulus for
the peripheral chemoreceptors
Glomus cells display an increase in firing rate with
lowering of PO2
Glomus cells are also sensitive to changes in
- PCO2 and pH (increase response to hypoxia)
Stimulation of peripheral chemoreceptors occurs at arterial PO2 values below
60mmHg
Peripheral chemoreceptors activate
dorsal and ventral respiratory group neurons in the medulla
– ↑respiratory rate
– ↑ tidal volume
Central chemoreceptors are
specialized neurons located close to the ventral surface of the medulla (close contact with blood vessels and cerebrospinal fluid).
•Other chemosensitive sites are in
the medullary raphe, hypothalamus
Central chemoreceptors are responsible for
70% of response to hypercapnia by changes at the level of
dorsal and ventral respiratory groups that change ventilation
H+ stimulates
mostly peripheral chemoreceptors because H+ does not
cross easily blood brain barrier (as CO2 does)
