foundations of medicine Flashcards
A body fluid refers to just the solvent or the solvent and solute?
Both Solvent and solute.
Is blood a bodily fluid?
No, just plasma.
What is the main function of bodily fluids?
Major site of biological reactions.
Whats the percentage water content of a young person compared to an older person? Why?
40 - 50% in the elderly
70 % in the young
Due to the water content of different tissues, Fat (20%), Muscle (60%)
Signs of mild dehydration?
Thirst / dry tongue,
Low urine output,
Dark urine.
Signs of severe dehydration?
Loss of skin turgor (elasticity)
Sunken eyeballs
Confusion
Decreased capillary refill (fingers stay white longer when pressed)
Postural drop in blood pressure. (when you get up too quickly).
What’s a sex difference and what’s a gender difference?
Sex is biological.
Gender is sociological.
What is osmolarity?
The measure of the number of particles of a solute in solution per litre of water. e.g. a high osmolarity would have a high solute concentration.
What is molarity?
Measure of number of molecules in solution.
What’s the difference in osmolarity and molarity?
Osmolarity measures individual particles and molarity measures molecules so a saline solution has double the osmolarity because NaCl dissociates but a normal molarity.
How do you make a one molar solution?
You dissolve the weight in grams of the RMM of the solute and make that up to 1 litre in water.
What is Osmolality?
Number of osmotically active particles per kg of water.
Difference in osmolarity and osmolality?
osmolality is measures in kg osmolarity in litres, the amount of litres of water is dependent on temperature whereas the weight in kg is not.
What is the definition of osmotic pressure?
The pressure required to prevent the flow of a solvent through a membrane, (to stop osmosis or diffusion)
What is hydrostatic pressure and oncotic pressure?
Hydrostatic - the effect of gravity
Oncotic - the pressure exerted by proteins.
What is tonicity?
The effective osmolality, so the concentration of particles that can exert an osmotic force, referring to the cell.
Three types of tonicity with explanations?
Isotonic solution: Concentration equal to the inside of the cell so no net movment.
Hypertonic Solution: concentration of solute greater than the inside of the cell so net movement of solvent out of the cell.
Hypotonic solution: concentration of solute less than the inside of the cell so movement of solvent to the inside of the cell.
What is the total plasma osmolality?
285 mOsm/kg
How is the ion charge distribution between the ICF and the ECF maintained?
Maintained by the Na+/K+ pump.
Example of an excitable cell and a non-excitable cell?
Muscle and nerve cells - Excitable
Red cell and Adipose cell - Non-Excitable.
What contributes to maintaining the ekectrical gradient in the cell?
Fixed anions,
Na+/K+ ATPase
Selectively permeable membrane.
What is the equilibrium potential?
The membrane potential when the electrical and chemical gradients are exactly balanced
Three different scales of cell to cell communication?
Autocrine - within the same cell.
Paracrine - communication with neighbouring cells.
Endocrine - communication with distant cells.
If a receptor is ionotrophic what effect will it activate in the cell?
An electrical change in the cell.
If a receptor is metabotrophic what effects will it cause in a cell?
A rage of effects including electrical effects.
What is an EPSP?
Excitatory post-synaptic potential. it makes the generation of an action potential more likely.
What is an IPSP?
Inhibitory post-synaptic potential. Makes the generation of an action potential less likely.
Opening of what type of ion channel would result in an EPSP?
Na+ channel.
Opening of what type of ion channel would result in an IPSP?
Cl-
What is summation? two types?
When an action potential is morelikely to be generated due to multiple impulses being recieved.
Spatial - from several neurones
Temporal - when impulses arrive from the same neuron and make an action potential more likely to be generated.
What is a Gap junction and what type of sugnals pass through them?
A paracrine cell to cell junction allowing both chemical and electrical signals to pass through them.
What is mass discharge of the Sympathetic NS? When does this occur?
When the Sympathetic NS undergoes mass stimulation, where almost all portions of the Sympathetic NS discharge simultaneous as a complete unit, preparing the body for activity.
Occurs in the ‘fight or flight’ response.
Does the Parasympathetic nervous system have mass discharge?
No, usually specific local responses are activated.
An example of complementary effects of both the parasympathetic and sympathetic system? (when they both increase something)
Salivary secretion.
In the eye what does the sympathetic and parasympathetic nervous system do?
Para - pupil dilation.
Sym - focusing of lens.
What is sympathetic and parasympathetic tone?
The level of stimulation in either system, the basal level of tone in blood vessels is partial constriction (this means theat a SINGLE nervous system can either increase or decrease activity - by changing tone)
Give an example of a time when the SNS and ANS interact to produce a response?
During micturation.
How do the ANS and SNS interact in the micturation reflex?
The ANS detects bladder filling through visceral afferents.
The spinal cord (SNS) sends signals back down to the external sphincter which then opens (this is when the person has voluntarily allowed themselves to do so)
Parasympathetic NS also contracts the smooth detrusor muscle.
Sympathetic NS also decreases excitability of detrusor and controls contraction of the internal sphincter (less control than the parasympathetic)
Flow receptors (ANS) monitor the flow.
Equation for mean arterial blood pressure?
Cardiac output X total peripheral resistance
Summarise the baroreceptor reflex, or Autonomic control of the cardiovascular system, use the eaxmple ofthe bodies response to arterial bp dropping.
Arterial bp drops
Monitored by baroreceptors
central control by the hypothalamus or medulla
Sympathetic outflow increases - this increases Vasoconstriction (increasing peripheral vascular resistance) it also increases heart rate and the force of cardiac contractions leading to increased cardiac output.
Parasympathetic outflow decreases - this increases cardiac output also increasing cardiac output.
What is a normal pulse rate range?
60 - 100 bpm
What is the pulse rate without any parasympathetic interaction?
110-120 bpm
What is a neurogenic bladder?
When there is damage to the somatic ervous system so no inhibitory signals are passing to the bladder, so even small amounts of urine cause uncontrollable micturation.
What is an atonic bladder?
When there are no afferent fibres and so bladder filling nerevr reaches the somatic nervous system and bladder can overflow.
An automatic bladder is when there is no control over when micturation happens, what is going on?
Sacral reflexes are still in tact - there is damage above the sacral region. this means micturation is not controlled by the brain but bladder emptying occors due to the sacral reflex when the level of urine reaches threshold.
Common ANS problems in diabetes? What is this called?
Tachycardia, postural hypotension, loss of sweating, inadequate bladder emptying, sexual problems.
Autonomic neuropathy.
Possible mechanisms for autonomic neuropathy in diabetes?
Hyperosmolar bodily fluids
Toxic products of metabolism e.g. sorbitol/fructose accumulation, decreased sodium pump activity
Decreased NO production.
What is homers syndrome?
INterruption to the sympathetic nervous supply to the head and the trunk.
Clinical signs of homers syndrome?
Constriction of pupil
ptosis
loss of sweating
vasodilation
What is hirshprungs defect?
Congenital defect of the ANS, no parasympathetic supply to the large intestine, causes a distended bowel e.g. megacolon.
An example of an infection caused defect of the ANS, what are the effects?
Chagas disease it is a trypanosome infection.
carried by beetles
affects nerev plexuses in wall of gut.
What happens to the ANS during ageing? causes?
Becomes less effective and takes longer to respond.
Less adrenoreceptors
Causes problems in:
Temp control, micturation, postral hypotension.
Definition of stem cell?
Highly specialized cells that are categorized by the capacity for self renewal by cell mutiplication, whilst maintaining their undifferentiated state they can differentiate into a variety of different mature cell types.
What is symmetric self renewal, assymetric self-renewal and symmetric differentiation in regards to stem cells
symmetric self renewal - stem cell produces two undifferentiated copies of itself.
Assymetric self renewal - stem cell produces one undifferentiated stem cell and one differentited cell
Symmetric differentiation - stem cell produces two differentiated cells
What is an adult stem cell?
A multipotent stem cell, can give rise to all the mature cell types of the tissue it is found in.
What is a stem cell niche?
anatomic location where stem cells are maintained in a quiescent state (period of inactivity) prior to proliferation.
What causes cross-striations in muscles?
Overlap of actin and myosin filaments.
What are the steps of ‘the power stroke’ of muscle contraction? (4)
- ATP binds to the myosin head, dissocociating it from the actin.
- ATP is hydrolysed by myosin head into ADP and Pi, altering the angle of the myosin head to the ‘cocked position’
- The myosin binds to the actin again.
- Pi is released and the myosin head returns to it’s original structure pulling actin with it = the power stroke.
Back to 1.
What is the actin filament the ‘thin filament’ composed of?
actin, tropomyosin and troponin.
What is the role of Ca2+ in muscle contraction? Where is it released from?
Binds to troponin and allows the myosin head to bind to the actin filament.
released from the sarcoplasmic reticulum.
Two types of smooth muscle?
Visceral or single-unit smooth muscle.
Multi-unit smooth muscle.
Features of single-unit smooth muscle?
Commonly and widely distributed.
Many cells acting as a ‘single unit’ due to electrical signalling (gap junctions e.t.c.)
Generates a continuous irregular tone (contractions)
Features of Multi-unit smooth muscle?
Not as common as single unit
Each myocyte has it’s own nerve supply allowing for independent behaviour
An example of single and multi-unit smooth muscle?
Single - circular muscle in the GI tract (peristalsis)
Multi - Piloerector muscles of the skin, or muscles of the iris.
Key features of smooth muscle?
Under involuntary control
form long spindle shaped, single nucleated cells.
No striations
no troponin complex.
What replaces troponin in smooth muscle cells? What does it have in common with troponin?
Calmodulin - also a ubiquitous Ca2+ binding protein.
Why is smooth muscle not striated?
Different arrangement of actin and myosin.
What is the differences and similarities in the contraction mechanism of striated muscle and smooth muscle?
Similarities - It has cross bridge formation between actin and myosin and a powerstroke.
Differences - Ca2+ binds to calmodulin and this leads to the activation of MLCK (myosin light chain kinase)
Where does Ca2+ come from in smooth muscle contraction?
The intersitial fluid.
Details on the two ways in which smooth muscle can be stimulated?
Electrical depolaristation of the membrane:
Opening of voltage-gated Ca2+ channels causes more calcium to be released from intracellular stores. Calcium induced Ca2+ release (CICR). this activates MLCK
Receptor activation: (neuronal or humoural)
Agonist induced opening of ligand gated Ca2+ channels OR the IP3 pathway. No changes in the membrane potential.
Two factors that enable smooth muscle reaxation?
How are they accomplished? (4)
Dephosphorylation of myosin and removal of Ca2+
Myosin:
Dephorylated enzymatically
Ca2+:
- Pumped across the membrane through Ca2+ ATPase.
- Pumped across the membrane through Na+/Ca2+ ion exchanger.
- Actively pumped into intracellular stores through Ca2+ ATPase.
Differences and similarities in contraction between striated and smooth muscle?
Smooth muscle has slower contraction and relaxation.
Same tension created.
Lower energy expenditure in smooth muscle.
What is noiception?
A response to noxious stimuli.
What is somatic pain and visceral pain, what are the differences between them?
Somatic:
Well localised
Higher concentration of noicereceptors.
Visceral;
Poorly localised
Unpleasent, often with nausea
Pain can also refer to somatic structures.
Two main types afferent sensory nerve fibres that transmit pain, the pain they transmit, and their features?
A fibres - fast myelinated.
A beta fibres - mechanical - mechanoceptors (usually involved in chronic pain)
A delta fibres - sharp pricking pain
C fibres - slow unmyelinated.
Aching, buring pain.
What part of the grey matter will apin fibres enter?
Dorsal horn.
What is peripheral sensitization and what causes it?
Increased excitability of a noicereceptor by the mechanism of lowered threshold voltage through changes to proteins and ion channels.
Caused by damage to tissue and repeated activation of noicereceptors, cuasing the prolonged release of inflammatory mediators and neuropeptides.
increased peripheral sensitization can result in what two things?
Allodynia - pain from a stimulus that is not normally painful
Hyperalgesia - increased sensitivity to pain:
Primary - at the site of injury.
Secondary - around the site of injury.
After a pain transmission has been recieved by the CNS in the dorsal horn of the spinal cord how is it transmitted?
Leaves the dorsal horn through ascending pathways (second order neurones) through the spinothalamic tract till it synapses in the thalamus.
Third order neurones project from the thalamus to the cortex or the limbic system (complex system to do with emotion and memory).
What is neuropathic pain?
Pain caused by a legion to a nerve itself.
What are silent noicereceptors?
Receptors that can only be activated in response to chronic inflammation.
What changes in the dorsal root ganglia are caused by peripheral sensitization?
More:
Receptors.
Ion channels.
Transmitters.
structural proteins.
What neurotransmiiter is released from fast acting A-delta fibres and which from C-fibres?
Glutamate (fast acting) from A-delta fibres and C fibres.
C-fibres also release substance P (slow acting).
What role do glial cells play in sensitization?
Release cytokines and other substances which sensitises post-synaptic receptors and increases the release of neurotransmitters from presynaptic neurones.
What is central sensitization? How is this caused in both A beta fibres and C fibres? (4)
Increased response to pain stinuli.
Can occur through:
More post-synaptic receptors, resulting in an increased response to neurotransmitters.
Increased release of neurotransmitters
Sprouting of a new terminal button
Decreased post-synaptic resistance.
What is central modulation in terms of noiceception?
The fact that the CNS in the dorsal horn and other levels of the spinal cord modulate (change) the strength of noiceception sensory inputs.
Can also occur in the descending pathways of the spinothalamic tract.
What is the gate control theory?
The theory that the presence of inhibitory interneurones between mechanoreceptors and noiceceptors inhibits the pain response when the mechanoreceptor is stimulated, and the noiceceptor is being stimulated.
What neurotransmitters are involved in the descending pain inhibition pathways? (4)
5 - HT
Endorphins
Enkephalins
Noradrenaline
Two ways in which pain can be inhibited - through central modulation?
Inhibitory descending pathways of the spinothalamic tract.
Stimulation of A - Beta fibres
A delta and C fibres synapse with what, and where? before synapsing with second order neurones and ascending to the thalamus in the brain?
an interneurone in the dorsal horn
What is mean body temp?
36.7, normal variation shows 36.3 - 37.1 is 95% of the population.
What can cause variation in body temperature?
Normal variation, Circadian rhythm, Ovulation.
How do humans mostly control body temperature?
Blood vessels.
What is the difference in warm fibres and cold fibres in thermoregulation?
Cold fibres send impulses at lower temperatures, warm at higher temperatures, warm emits with much higher frequency.
What are the two main classes of temperature receptors by location?
Skin receptors and central receptors.
Where are 90% of the temperature receptors based? what is the main function of the other 10%?
90% are central receptors, the other 10% is in the skin and fuction in an anticipatory manner.
What are the 4 main routes for heat loss? What one functions as the main route forheat loss?
Evaporation
Radiation (main route)
Convection
Conduction
What are the main ways the body responds to low temperatures?
Vasoconstriction
Shivering thermogenesis
Non-shivering thermogenesis
Piloerection
Behavioural responses.
What are the main ways the body responds to high temperatures?
Vasodilation
Sweating
Decrease in heat production
Behavioural responses.
What is the nervous system division, neurotransmitter and receptor activity change in vasodilation?
Sympathetic nervous system impulses decreased, NA is decreased less synapsing with a1-adrenoceptors.
What is the nervous system division, neurotransmitter and receptor activity, and effector activity change in sweating?
Sympathetic nervous system activity increased, leading to increased release of acetylcholine and increase stimulation of muscarinic receptors on eccrine sweat glands.
What is the nervous system division, neurotransmitter and receptor activity change in piloerection?
Increase in sympathetic activity leading to an increase in the release of acetylcholine acting on muscarinic receptors on piloerector muscles.
What is the nervous system division, neurotransmitter and receptor activity change in shivering?
Increase in somatic activity causing increased release of acetylcholine acting on type 1 nicotinic receptors on skeletal muscle.
What are smooth muscle cells surrounded by?
A network of collagen and elastin.
What accumulates in lethally injured cells?
Calcium.
Are synapses found in the dorsal root ganglia?
no.
Net direction of forces of Na+ K+ Ca2+ Cl- ?
Na+ inside the cell
K+ Outside of the cell
Ca2+ Inside the cell
Cl- Outside the cell
What ions is the cell permeable to at rest?
K+ and Cl-
Difference in a relative and an absolute refractory period?
Relative - can have an action potential generated
Absolute - no action potential can be generated
What are the effects of hyper and hypokalemia on the resting cell membrane potential?
Hyper - causes depolarisation, more positive
Hypo - causes hyperpolarisation more negative
