Lecture 2 Flashcards
What mediates heart rate under normal conditions?
Vagal tone - parasympathetic innervation
Do sympathetic nerves increase or decrease heart rate?
Increase heart rate and contractility
What neurotransmitters do sympathetic nerves use to get from the CNS to the organs?
ACh then NA
How do sympathetic signals from the CNS reach the organs?
presynaptic sympathetic fibres from the brain travel inferiorly within the spinal cord tracts and then exit the spinal cord between T1- L2/3 spinal nerves (thoracolumbar) and then:
- go into ganglion of that level and synapse
- travel superiorly in the sympathetic chain to another ganglion and synapse
Where do nerves destined for the heart synapse?
cervical sympathetic ganglia and upper thoracic sympathetic ganglia as the cardiopulmonary splanchnic nerves
Where is the cardiac plexus and what does it contain?
Between the arch of the aorta and the pulmonary trunk ad contains sympathetic fibres, parasympathetic fibres and visceral afferent fibres
What neurotransmitters do parasympathetic nerves use to get from the CNS to the organs?
ACh on both the pre- and postsynaptic fibres
Which cranial nerves contain parasympathetic fibres?
3, 7, 9 and 10
Do the pelvic splanchnic nerves contain sympathetic or parasypathetic fibres?
parasympathetic fibres
What do the pelvic splanchnic nerves supply?
organs of the lower abdomen, pelvis and perineum
What are visceral afferent nerve ending stimulated by?
Chemical and infarcted tissue
Where do you find visceral afferent nerve endings?
inner aortic arch pulmonary trunk around the SA node outflow tracts of both ventricles papillary muscles vena cavae
What is pain in anatomical/ physiological terms?
- stimulation of sensory receptor
- afferent action potential reaches brain
- we “feel” the pain according to the part of the brain that is stimulated by the action potential
How does somatic pain present?
Sharp, stabbing, well localised
How does visceral pain present?
dull, aching, nauseating and poorly localised
Where do pain sensations reach in the brain?
cerebral cortex
What reaches the postcentral gyrus of the parietal lobe?
somatosensory - APs reaching here will bring body wall (somatic) sensations into consciousness
What reaches the precentral gyrus of the frontal lobe?
somatomotor - APs reaching here will bring about contractions of body wall (somatic) skeletal muscle
Give some examples of sharp central chest pain sources.
Herpes zoster pec major muscle strain dislocated costochondral joint slipped thoracic intervertebral disc pericarditis
Give some examples of dull (visceral) central chest pain sources.
oesophagitis MI and angina pancreatitis cholecystitis ruptured aneurysm of aortic arch
Which tubular structure does the vagus nerve run on?
trachea
Where is the left phrenic nerve in relation to the left lung hilum?
anterior
Which side of the body is the thoracic duct?
right
How do pain signals from organs reach the brain?
Travel into sympathetic chain at cervical and T1-5 level, then into the spinal cord and up to the brain bilaterally
Is pain is coming from a somatic structure, where is the radiation?
Along the affected dermatome(s)
How does referred pain come about?
Afferent (sensory) fibres from soma and afferent (sensory) fibres from viscera enter the spinal cord at the same levels
What percent of patients show a right dominant pattern?
~70%
What percent of patients show a left dominant pattern?
Up to 35%
Which coronary artery is more likely to be affected by atherosclerosis?
LAD branch of LCA (40-50%)
RCA (30-40%)
Circumflex branch of LCA (15-20%)
Left main stem coronary artery
What supplies the SA and AV nodes?
SA nodal branch of RCA (60%)
AV nodal branch of RCA (80%)
What supplies the interventricular septum?
LAD and posterior interventricular artery
How do electrical signals flow through the heart?
SA –> AV –> Bundle of His –> R & L bundle of His –> Purkinje fibres
