Week 4 Flashcards
What is a receptor? Definition and properties
A receiving molecule (glycoprotein) that sends specific messages into cells once the appropriate ligand has been bound
N terminal generally the one being bound (in extracellular environment)
What is amplification?
Receptors amplify signals
They work at very low concentrations
Time scales different dependent on drug/receptor - from ms to days
Ligand-gated receptor/channel complexes - definition and example
Five subunits with pore in the middle, look like a flower from above
Each subunit has a binding site for a drug
Example: Nicotinic receptor
G-protein-coupled receptors - definition and example
one single protein that spans 7 transmembrane regions
N-terminal - ligand-binding site
C-terminal G-protein binding region
Examples: Muscarinic receptors
What is a G protein?
Guanine nucleotide (GTP/ GDP) binding proteins
3 subunits - alpha, beta, gamma
A G protein attached to GTP is active, or “on,” while a G protein that’s bound to GDP is inactive, or “off.”
What are the subtypes of alpha G-protein subunits?
Gs (stimulate), Gi (inhibit), Gq
Tyrosine kinase receptors - discussion and example
Ligand (such as insulin) binds to receptor which essentially allow glucose into fat cells to be stored / processed
Process - ligand binds, two channels move together, phosphate is added to the tyrosine on the receptor which allows the channel to open
1 protein subunit, 1 transmembrane
domain
Example - insulin
Intracellular (or nuclear) receptors
Found within the cell
Example - cortisol hormone receptor
What are other drug binding targets (other than receptors)? (3)
proteins, such as receptors, enzymes, transporters, ion channels or genetic material, such as DNA.
Why do we need to regulate level of breathing?
Adjusted to meet demand for O2 and production of CO2
In what circumstances does O2 requirements or Co2 production increase? 4 examples
Exercise, infection, injury, metabolic dysfunction
How do you increase amount of O2 transported?
Both ventilation AND increased cardiac output
Physiological process of breathing
Nerve signals sent from CNS to respiratory muscles (which are skeletal muscles) to tell them to relax and contract
Key respiratory muscles for inspiration and expiration
Inspiration - Diaphragm, external Intercostal muscles, pectorals, sterocleidomastoid, scalene
Expiration - elastic recoil of diaphragm, internal intercostals, abdominals
How does the brainstem dictate the basic breathing pattern?
Complex series of nueronal connections that interpret and determine the body’s need for oxygen
What factors determine the rate and depth of breathing?
Receptors in muscles and joints (direct rather than waiting for CO2 levels to go up)
Stretch receptors in lungs
Chemoreceptors
Central chemoreceptors - where, function, overview of mechanism
In medulla
Monitors changes in arterial CO2
Responds to changes in H in CSF but does NOT directly respond to changes in blood pH
Do not respond to changes in O2 levels
MECHANISM - negative feedback loop
Peripheral chemoreceptors - where, function, overview of mechanism
In carotid and aortic bodies
Activated by O2 levels, CO2 levels, and acidaemia (low pH)
Sends signal to respiratory centres in medulla via sensory nerves to increase ventilation
Negative feedback loop
What is the hypercapnic drive?
Predominant stimulus underlying urge to breathe
Ventilation is generally proportional to PaCO2 (because of the importance of pH to homeostsis)
What is hypoxic drive?
Occurs at VERY low PaO2
Low PaO2 stimulates increased ventilation (buth this drive only kicks in only at very low PaO2)
What steps are required for the initiation of breathing?
CNS sends message to inspiratory muscles to start breathing
Breathing feedback mechanisms overview (4 outlined)
Central chemoreceptors
Peripheral chemoreceptors
Muscles
Emotional stimuli
Irritant and stretch receptors in lungs
What is sleep apnoea?
Temporary cessation of breathing during sleep
More than 5 episodes per hour lasting more than 10 seconds
Causes tiredness, cardiovascular complications, obesity/diabetes
What test is used to diagnose sleep apnoea?
Polysomnography EOG EEG ECG MANY TESTS
What are the two types of sleep apnoea? (Two types with general causes)
Obstructive - airways blocked
Can be caused by obesity, alcohol/sedatives, smokers
Central - dysfunction in process that initiates breathing
Stroke, drugs such as opiods can suppress neuronal activity, altitude, neonates, central hypoventilation syndrome
What is cheyne-stokes respiration?
Cheyne–Stokes respiration is an abnormal pattern of breathing characterized by progressively deeper, and sometimes faster, breathing followed by a gradual decrease that results in temporary apnea.
Often happens at high altitudes
Back and forth between peripheral and central chemoreceptors
Peripheral increase breathing in response to low O2
Central decrease breathing to respond to low pH
What is consent? (three legal principles)
Voluntary agreement to treatment, examination
Permission to examine, investigate, treat
Waiving of right to bodily integrity
What are the key legal issues that doctors have? (three)
Battery, negligence (both civil) and assault/battery (criminal)
What are the three aspects of VALID consent?
Information, voluntariness, competence
Patients must also know they can change their mind
What are the four features of competence? (re consent)
- understand relevant information
- retain relevant information
- weight up relevant information
- communication decision
What information should you give when getting consent?
PARQ Procedure Alternatives Risks Questions
How much information is adequate? (three different legal models)
Professional practice standard - what complies with the practice standard?
Reasonable / prudent person standard - what does a hypothetical reasonable person want to know?
Subjective standard - what does this person want to know?
What is the significance of the Montgomery negligence case?
Diabetic woman had vaginal delivery and son had significant disabilities. She claimed she had not been fully informed of risks. Won £5 million
How did the law evolve following the Montgomery case?
Move away from the Bolam test to a model where they doctor is responsible to ensure the patients are aware of any material risks and alternatives - based either on a hypothetical reasonable patient or if possible, the patient themselves (if known well enough)
What is asthma?
a respiratory condition marked by attacks of spasm in the bronchi of the lungs, causing difficulty in breathing
Additional mucus caused by immune response
Common symptoms: wheeze, cough, dyspnoea (breathlessness)
What is the general mechanism of asthma? (5 steps)
CAUSE: allergen inhalation / exercise Immune system response Airway inflammation Impaired airway function RESULT: symptoms
What is the general mechanism of asthma? (5 steps)
CAUSE: allergen inhalation / exercise Immune system response Airway inflammation Impaired airway function RESULT: symptoms
What is the relationship between the radius of the airway and the resistance and airflow?
As airway radius DECREASES, resistance INCREASES and airflow DECREASES
What is the impact of asthma on the airway? Four factors
- contraction of smooth muscle
- excess mucus secretion
- oedema / swelling
- irritation of sensory neurons (cough)
What is normal vs asthmatic airflow?
Normal airflow - laminar flow
Asthmatic - Turbulent flow (produces wheezing)
Simple description of allergic response (two stages)
Sensitisation - allergen exposure - allergen processed by immune system - antibodies generated, immune system 'primed' Response - allergen exposure (same allergen) - allergen binds to antibodies w/ immune cell activation, inflammatory response - Symptoms
Simple description of allergic asthma response (two stages)
Sensitisation - allergen exposure - allergen processed by immune system - antibodies generated, immune system 'primed' Response - allergen exposure (same allergen) - allergen binds to antibodies w/ immune cell activation, inflammatory response - Symptoms
Describe the sensitisation process of allergy-induced asthma (6 steps)
- Allergen inhaled and enters airway tissue
- Antigen is engulfed by antigen-presenting cell (dendritic cell)
- Antigen presented to naive helper T cell
- T cell is activated and becomes Th2 cell
- The Th2 cell coordinates with other immune cells via cytokines (Eosinophils and B cells)
- B cells produce antibodies which bind to mast cells
List the cell types responsible in allergy-induced asthma response - name, role, inflammatory mediators involved
B cells - produce antibodies and IgE
Th2 cells - recruit eosinophils, activate B cells
Mast cells - Degranulate to cause inflammation, contraction, mucus
Eosinophils - Degranulate to cause inflammation, contraction, mucus
What happens during allergy-induced asthmatic response? (2 phases possible)
Primary
- Allergen enters airway and enters airway tissue
- Allergen binds receptor on mast cell, which degranulates
- Eosionphil degranulates
- Inflammation causes symptoms
Reoccurrence can be causes T CELL RESPONSE / LATE RESPONSE