chapter 6 - neuro control of breathing

somatic versus autonomic

somatic: primarily voluntary, skeletal muscles, and conscious movement (respiratory skeletal muscles)

autonomic: involuntary, smooth muscle, cardiac muscle & glands, automatic body functions (airway smooth muscle + glands)

sympathetic nervous system

"fight or flight"

prepares the body for action - heart rate increases, pupils dilate, airways open, and secretions decrease

bronchodilation

parasympathetic nervous system

"rest and digest"

supports rest and routine function - heart rate decreases, pupils constrict, airways narrow, and secretions increase

bronchoconstriction

pulmonary plexus

network of nerves that innervates airway smooth muscle, pulmonary blood vessels, and airway glands

fibers of pulmonary plexus

sympathetic and parasympathetic

parasympathetic fibers originate from the vagus nerve

phrenic nerve

C3, 4, and 5 - motor and sensory

major respiratory target is diaphragm and main effect is diaphragm contraction - breathing muscle

neurotransmitters

chemical messengers of the nervous system

different receptors = different effects

route of neurotransmitters

neuron releases neurotransmitter, crosses the synaptic gap, binds to a receptor, and response occurs - receptor helps determine response

excitatory vs inhibitory signal

excitatory: the receiving cell is more likely to respond

inhibitory: less likely to carry out the signal

agonist vs antagonist

agonist: activates the receptor to produce a receptor response

antagonist: blocks the receptor to prevent/inhibit the receptor response

direct vs indirect

direct: acts as the receptor

indirect: changes the amount/activity of the neurotransmitter

adrenergic receptors

respond to sympathetic stimulation

types: alpha 1, beta 1 & 2

alpha 1

blood vessels

vasoconstriction, vascular resistance, increased BP

beta 1

heart

heart rate and contractility increases - involved in kidney / RAAS activity

beta 2

lungs and airways (star for RTs)

prominently on airway smooth muscle

activated beta 2

bronchial smooth muscle relaxes, airway diameter increases, bronchodilation

albuterol vs ipratropium

albuterol: beta 2 agonist. bronchodilation

ipratropium: muscarinic antagonist, reduces bronchoconstriction effect

cholinergic receptors

associated with the parasympathetic nervous system

primary: ACh (acetylcholine)

main types: muscarinic and nicotinic

muscarinic receptors

M2 & M3 receptors found in the tracheobronchial system

muscarinic pathway

parasympathetic stimulation, ACh released, ACh activates muscarinic receptors, bronchial smooth muscle contracts, bronchoconstriction

histamine

important inflammatory mediator - H1-4

released by mast cells

can cause bronchoconstriction, increased vascular permeability, and airway inflammation (H1)

airway narrowing

radius decreases, resistance increases, and airflow decreases

bronchospasm

type of airway narrowing

smooth muscle contracts

inflammation + edema

type of airway narrowing

airway wall thickens/swells

mucus

type of airway narrowing

secretions obstruct the lumen

inflammation

a protective response to injury, infections, irritation, and allergens

acute vs chronic inflammation

acute: short-term, protective, and helps eliminate the threat

chronic: persistent, can damage tissues, and may alter airway structure/function

allergic inflammation

allergen immune response

IgE/mast cells (allergen-driven and allergenic asthma)

eosinophilic inflammation

can migrate into airway tissue and release inflammatory mediators

commonly associated with type 2/eosinophilic asthma

IL-5 plays important role in activity

neutrophilic inflammation

release inflammatory enzymes + mediators

associated with COPD and chronic airway inflammation

significance of IgE

activates mast cells

airway remodeling

wall thickening, smooth muscle changes, increased mucus-producing structures

narrowing may become more persistent

genotype, phenotype, and endotype

geno: genetic makeup

pheno: observable characteristics

endo: specific biological mechanism/pathway

asthma

chronic, heterogenous airway disease characterized by airway inflammation, airway hyperresponsiveness, and variable airflow obstruction

different phenotypes of asthma

allergic, nonallergic, late-onset, persistent/fixed airflow limitation

COPD

characterized by persistent obstruction and chronic respiratory symptoms

often associated with tobacco smoke or noxious gases

COPD components

small airway disease / chronic bronchitis and alveoli emphysema

chronic bronchitis

airway problem, chronic inflammation, increased mucus, airway narrowing and airflow obstruction

emphysema

alveolar problem, alveolar wall destruction, decreased gas-exchange surface area, decreased elastic recoil, and air trapping/flow limitation

alpha-1 antitrypsin deficiency

an inherited risk for emphysema - serpina1 gene mutation

low AAT, alveolar destruction

diagnosed with blood testing