PNB 2265 Study Guide - Midterm Guide: Peripheral Chemoreceptors, Reticular Formation, Ph
16 May 2018
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RESPIRATION FROM SLIDE 16
LOOK AT SLIDE 16
Left: Lungs
●Alveolar O2 [PO2 = 100]
●Blood enters pulmonary capillary [PO2 = 40]
●Gradient for O2 to move into the blood and dissolve
●But only some of it can be carried in that form
○As you push the PO2 of the plasma up to 100 you are pushing more and more O2 onto
hemoglobin to a point where it is almost 100% saturated
○Hemoglobin keeps sucking up O2 so you can carry more and more while maintaining the 100 PO2
of the blood - pO2 is derived from DISSOLVED oxygen
Right: Tissues
●Low PO2 in tissues [PO2 = 40 ]
●That’s what pulls O2 from the plasma into the tissues (low PO2); as you keep pulling O2 from the plasma it
lowers the PO2 until more and more comes off Hb until 75% saturated
Shfits:
●right shift = release of O2 = less saturated Hb
● Left shift = loading O2 = more saturated Hb
CO2 Transport
●Transported in 3 ways
1. Dissolved in plasma
2. Bound to HB
3. As HCo3-
a. CO2 + H2O → H2CO3 → H+ + HCO3-
Internal Resp vs External Resp
CO2 & Blood pH
●Hyperventilation: exhaling rapidly and not inhaling enough so a lot off CO2 is lost → more basic, increase
pH → resp. Alkalosis
●Hyperventilation: not exhaling enough so a lot of CO2 is kept → more acidic, decrease pH → resp.
Acidosis
Control Resp.
●Feedback loop regulates resp rate & depth
●Skeletal muscles control respiration
●Controller/Integration is brainstem
Sensors
●Peripheral sensors in aorta + carotids: monitor ARTERIAL blood conditions (PO2 and PCO2) esp monitor
CO2 and H ions
●Central chemoreceptors: pH sensors only, indirectly senses CO2
●Basic breathing pattern is set by neurons in reticular formation of the medulla and pons
○Reticular formation: a diffuse network of nerve pathways in the brainstem connecting the spinal
cord, cerebrum, and cerebellum, and mediating the overall level of consciousness.
○Medulla sets resp rhythm
●Neuron types: Inspiratory (I) & Experiatory (E)
Brainstem Resp. Centers
●Resp. rhythm generation
●Activitates I and E nerves and muscles
●Causes changes in alveolar ventilation due to changes in blood gas + partial pressures
Medulla Resp. Centers: VRG
●PACEMAKER neurons
●Ventral respiratory Group, produces inspiration
●Rhythm generating Pre-Botzinger Complex, sends excitatory
output to I neurons and inhibitory
output to E
neurons
○Resp rhythm due to “burst” properties of pacemakers AND the reciprocal innervation
●Both I and E neurons
●Receives sensory input from DRG
Medulla Resp. Centers: DRG
●Dorsal respiratory Group
●Recieves input from:
○Peripheral chemoreceptors
○Arterial chemoreceptors
○RTN ( ) lung stretch receptors and chemoreceptors in brainstem
○Baroreceptors
●Sends output to VRG & PRC (I neurons)
Pontine Resp. Centers
●Pneumotaxic Center fine tunes breathing rhythym and smooths out transitions between inhale and exhale
How to regulate breathing?
●Increase ventilation RATE & DEPTH
●Chemical factors of blood: Co2, pH, O2
●CO2 & pH are most important for regulating resp.
How to detect changes in chem. Factors?
●Peripheral chemoreceptors: carotid & aortic bodies
○Sensitive to PO2, PCO2, pH
●Central Chemoreceptors
○Sensitive to pH of CSF (Cerebrospinal fluid (CSF) is a clear, colorless body fluid found in the brain
and spinal cord)
Control by PO2
●Peripheral chemoreceptors stimulated by decrease of O2 in systemic blood (LARGE decrease)
○EFFECT: increased ventilation due to need for more O2
●Peripheral chemoreceptors sense CO2 & pH
●Central chemoreceptors sense only pH
●Exercise: increase in ventilation due to
○Reflex input from proprioceptors, input from motor cortex
DEFENSE I (NONSPECIFIC INNATE DEFENSE)
Functions
●Body fluid homeostasis
●Immune system
●Nonspecific (innate) immunity
●Specific (adaptive) immunity
●Role of Immune Responses
○Defend against infection, immune surveillance, eliminate damaged cells
○But - allergies, autoimmune diseases, transplant rejection
Lymphatic System
●Lymph
●Lymphatic vessels
○Blind ended
capillaries
Lymphoid tissues/organs
●Primary: Bone Marrow & Thymus
○Bone Marrow: produces ALL LYMPHOCYTES, matures B lymphocytes
○Thymus: matures T lymphocytes
●Secondary: Lymph nodes, spleen, peyer’s patches, tonsils
○Lymph nodes: fibrous capsule with partitions; contains both afferent & efferent lymphatic
vessals.
■Macrophages
■99% antigens removed & processed
■Filters
■Dendritic cells
○Lymphatic nodules: lymphocytes packed in the connective tissue, NO CAPSULE
■Found in CT beneath epithelium of resp., digestive, and urinary tracts
■Ex: Tonsils & Peyer’s patches
○Spleen: removes RBCS, stores Fe, can initiate immune responses
Cells Mediating Immune Responses
●Neutrophils: Inflammation, phagocytosis
●Basophils: Histamine, heparin
●Eosinophils: defend against parasitic worms
●Monocytes: become macrophages
●Lymphocytes: specific immunity
○ALL except NK cells participate in specific immune responses
●Other Cells
○Macrophages for phagocytosis
○Mast cells for histamine
○Plasma cells
●Dendritic Cells
○Highly motile, not macrophages but can phagocytose
○Found in almost all tissues esp ports of entry where internal and external environment meet
Other Defence Mechanisms
●Detoxification: liver, microsomal enzyme system
●Stress system: causes sympathetic nervous signals to adrenal medulla; fight or flight response
Nonspecific Defenses: no specific recognition, just identity foreign cell/matter, same response regardless of
stimulus, prevention first
1. First Line - physical & chemical barriers
a. Skin + mucous membranes = physical barrier
b. Protective chemicals
i. Skin acidity
ii. Gastric HCl, proteolytic enzymes
iii. Lysozyme of saliva
iv. Sticky mucous
c. Ciliated mucosa of resp. System
Document Summary
Blood enters pulmonary capillary [po2 = 40] Gradient for o2 to move into the blood and dissolve. But only some of it can be carried in that form. As you push the po2 of the plasma up to 100 you are pushing more and more o2 onto hemoglobin to a point where it is almost 100% saturated. Hemoglobin keeps sucking up o2 so you can carry more and more while maintaining the 100 po2 of the blood - po2 is derived from dissolved oxygen. Low po2 in tissues [po2 = 40 ] That"s what pulls o2 from the plasma into the tissues (low po2); as you keep pulling o2 from the plasma it lowers the po2 until more and more comes off hb until 75% saturated. Right shift = release of o2 = less saturated hb. Left shift = loading o2 = more saturated hb. Transported in 3 ways: dissolved in plasma, bound to hb, as hco3- a.
