Reflex actions

Question 1

Describe the neural interactions between the CVS and RS

Answer 1

• respiratory/ abdominal pump
• increases VR to RV (EBV)
• increased SV (starlings law)

Question 2

outline neural interactions at play (central nervous mechanism)

Answer 2

• increased inspiration —> increased HR
• mechanism known as respiratory sinus arrhythmia
• decreased HR during expiration
• modulation of vagal efferent to SAN
• decreased activity of vagal efferent during inspiration
• inhibited via CID
• excitatory efferents via phrenic nerve to diaphragm

Question 3

outline the reflex mechanism involved in neural interactions (hering-Breuer reflex)

Answer 3

• CID —> inspiratory Mn
• inspiration
• widening of airways (due to negative external pressure)
• slowly adapting stretch receptors activated
• pulmonary stretch R
• increased stimulation (stretch mediated)
• afferents (Vagal) sent to the NTS of the medulla
• excitatory influence on NTS
• further synapses —> NA
• inhibitory action on NA
• reduced vagal tone

Question 4

increase in rate and depth of breathing leads to what?

Answer 4

• decrease in vagal tone leading to an increase in HR
• SNS innervation dominates
• increased resp frequency and increased TV leads to a further reduction in vagal efferent activity

Question 5

What are the receptors involved in the diving reflex ?

Answer 5

• evoked via trigeminal receptors
• cold water on the face/nose , nasal mucosa
• mediated via sensory afferents of the opthalmic, maxillary and mandibular nerves

Question 6

what is the significance of the diving reflex?

Answer 6

• protection and survival mechanism
• babies have evolved profound reflex
• decreases with age
• very strong bradycardia
• preservation and protection of cardiac muscle by reducing energy consumption
• blood flow to the brain is preserved and maintained

Question 7

explain the mechanism of the diving reflex

Answer 7

• inhibition of CIN
• expiratory apnoea (breathing out and holding breath) during Immersion
• reduced HR and increased vagal activity via increased action of the Nucleus ambiguous
• VC (increased SNS activity via RVLM) - except for the brain
• breathing out increases buoyancy
• essentially removal of influence that increased HR has during RSA increasing vagal tone

Question 8

list some mechanical and chemical stimuli that can evoke the diving reflex

Answer 8

• sinus washing
• irritant vapours
• intubation, bronchoscopy
• lumps of food caught in pharynx
• quadriplegics during mucous aspiration
• strong response can cause expiratory apnoea
• cardiac arrest = steak house death

Question 9

what can stop supra ventricular tachycardia?

Answer 9

• ice bag on the face = provokes the diving reflex by stimulation of trigeminal receptors
• reduces HR
• breaks the tachycardia

Question 10

how to stop a diving reflex?

Answer 10

• mouth- mouth respiration or ventilating thorax
• lung inflation
• PSR stimulated
• restortes rthyhmic respn HR