Physiology + pharmacology Sympathetic Flashcards
- Outline the effects of the fear-fight-flight response on the body - Describe the effect of stimulating the sympathetic nervous system and different adrenoceptors involved in the heart, blood vessels, kidney, metabolism, GI tract, eye, lungs, and sweat glands - Describe adrenergic neurotransmission, and how drugs may alter release and termination of noradrenaline - Outline different adrenoreceptor subtypes and their associated intracellular pathways, and the effects of adrenoreceptor agonists a
Where are the pre-ganglionic sympathetic neurones located?
- Thoracolumbar region
What are the biological effects of the sympathetic nervous system on the body?
Initiates fear-fight-flight response
- Increased heart rate + contractility
- Increased cardiac output
- Increased vasoconstriction
- Increased blood pressure
- Increased air into lungs
- Increased oxygen uptake/carbon dioxide removal
- Dilation of pupils, increased light into eyes, better vision
- Increased fuel to muscles: breakdown glycogen/lipids
- Increased sweating: temperature regulation
- Decrease non-essential functions (decreased GI tract activity etc) - limits energy use
What organs does the sympathetic nervous system act on?
- Heart
- Blood vessels (arteries, veins etc)
- Kidney
- Metabolism
- Lungs
- Eye
- Sweat gland
- GI tract
Which receptor does noradrenaline and adrenaline act on in the heart?
Beta 1 adrenoceptors
Which receptor does noradrenaline and adrenaline act on in blood vessels?
Alpha 1 adrenoceptors
What is the effect of stimulation of the sympathetic nervous system on the heart?
- Noradrenaline and adrenaline act at B1 adrenoceptors on heart
- On SAN- increases generation of electrical acuity which increases heart rate- chronotropic effect
- On cardiac muscle cells- increases force of contraction of atria and ventricles, increases stroke volume
Define stroke volume
Volume of O2 pumped by heart’s left ventricle
How do you calculate cardiac output?
Stroke volume X heart rate
What is the effect of stimulation of the sympathetic nervous system on blood vessels?
- Noradrenaline and adrenaline act at alpha 1 -adrenoceptors on blood vessels
- Vasoconstriction (constriction of arterioles) - Increases blood vessel resistance (TPR - total peripheral resistance)
- Venoconstriction - constriction of veins, increases returns of blood to heart, increasing cardiac output
- Overall, all of this combines, then leads to an increase in blood pressure
How do you calculate blood pressure?
CO X TPR
What is the effect of stimulation of the sympathetic nervous system on the kidneys?
- Noradrenaline acts at B1- adrenoceptors (on afferent arterioles) to release renin from prorenin
- Renin causes production of angiotensin II (Ang II) from angiotensinogen
- Ang II increases blood pressure
What is the effect of the sympathetic nervous system on liver and skeletal muscle (metabolism)?
- Stimulation of alpha/beta adrenoceptors
- Breaks down glycogen into glucose (glycogenolysis)
- Promotes glucose synthesis (gluconeogenesis)
What is the effect of the sympathetic nervous system on the pancreas (metabolism)?
- Stimulation of alpha/beta adrenoceptors
- Decreased insulin response, which normally ‘stores glucose’
- Increased glucagon due to increased conversion of glycogen stores into free glucose
What is the effect of the sympathetic nervous system on Adipose tissue (metabolism)?
- Stimulation of Beta 3 adrenoceptors
- Increased lipolysis: triglycerides broken down into free fatty acids + glycerol
- Both increase ATP levels for energy
What is the effect of the sympathetic nervous system on GI tract?
- Stimulation of alpha and B2 adrenoceptors
- Activation of alpha 1 adrenoceptors evokes contraction of bladder shincter
- B2 adrenoceptors induces relaxation of smooth muscle allowing filling
- Bowel/bladder function non-essential during ‘fear-fight-flight’
What is the effect of the sympathetic nervous system on the lungs?
- Receive sympathetic innervation
- Bronchioles contain Beta 2 adrenoceptors which are activated by circulating adrenaline released from adrenal glands to produce bronchodilation
- Facilitates breathing
What is the effect of the sympathetic nervous system on the eyes?
- Stimulation of alpha1 adrenoceptors on dilator papillae (radial muscle of iris) dilates pupil- increase light on retina- more acute sight
What is the effect of the sympathetic nervous system on the sweat glands?
- Release of ACh and this binds to Mus receptors, induces sweating- temperature control
What is adrenergic transmission?
- Transmission of noradrenaline at a synapse or neuroeffector junction (post ganglionic synaptic terminals and CNS)
What type of receptors are adrenergic receptors?
GPCRs