Physiology Flashcards
Define ‘homeostasis’…
Maintenance of steady states within our bodies by coordinated physiological mechanisms
Main type of homeostatic control in the body…
Negative feedback
What are the components of a phospholipid?
Hydrophobic tail + hydrophilic head
Bonds between phospholipids are strong. True/False?
False
Bonds are weak - explains the fluid nature of the membrane
Cholesterol contributes to which two aspects of the membrane?
Fluidity and stability
What are the 3 main types of proteins found on the membrane?
Integral (receptors)
Transmembrane (channels, transporters)
Peripheral (enzymes)
The glycocalyx layer is formed by…
Short carbohydrate chains bound to proteins and lipids
What are desmosomes?
Adhering junctions that anchor cells together
What are tight junctions?
Join lateral edges of epithelial cells near their apical membranes
What are gap junctions?
Communicating junctions that allow movement of charge between adjacent cells
2 main factors that influence whether a particle can passively permeate the membrane
Lipid solubility (non-polar pass easily) Size
Diffusion is movement from ___ to ___ concn
High to low
Fick’s law of diffusion describes the rate of net diffusion and is made up of…
Magnitude of concn gradient
SA available for diffusion
Lipid solubility and size/weight of substance
Distance over which diffusion must occur
Osmolarity is defined as…
The number of osmotically active particles present in a solution
How is osmolarity calculated?
Using molar concn (mM) and number of osmotically active particles (n)
150mM NaCl has osmolarity = ?
150 x 2 (Na+ and Cl-) = 300mOsm
A hypotonic solution will ____ in cell volume
A hypertonic solution will ____ in cell volume
A isotonic solution will ____ in cell volume
Increase (needs mOre water)
Decrease (needs lEss water)
Have no change
Facilitated diffusion requires energy. True/False?
False
Active transport transfers a substance from high to low concn. True/False?
False
Low to high
_ Na+ out for every _ K+ in with regards to Na-K pump
3, 2
Secondary active transport occurs by which 2 mechanisms? Define them
Primary active transport uses…
Utilises conc. gradient and ion movement:
Symport (co-transport): solute and ion move in same direction
Antiport: solute and ion move in opposite directions
ATP directly for energy
Membrane potential (Em) arises due to…
Separation of opposite charges across the membrane
At resting potential, the membrane is 100x more permeable to sodium than potassium. True/False?
False 100x more permeable to K+ than Na+
Em for K+ is approx…
-90mV
Em for Na+ is approx…
+60mV
Nernst equation
Eion = 61log[ion]o / [ion]i
extracellular/intracellular conc.
Membrane potential is much closer to the potential of Na+ ions. True/False?
False
Much closer to Ek+ due to greater permeablity of K+
Em for a typical nerve cell at rest = ?
-70mV
GHK equation (used to calculate membrane resting potential)
Em = 61log x PK+[K+]o + PNa+[Na+]o /
PK+[K+]i + PNa+[Na+]i
Normal blood glucose level
Around 5 mmol/l
In the absorptive + post-absorptive states, which hormones control [glucose]p
Insulin and glucagon
In emergencies, which hormone control [glucose]p
What is it released by?
Adrenaline
Released by adrenal gland
In starvation, which hormones control [glucose]p
What are they released by?
Cortisol - Released by adrenal gland,
GH - Released by anterior lobe of the pituitary
In pancreatic islet cells, _ cells release glucagon, _ cells release insulin and _ cells release somatostatin
alpha, beta, delta
Insulin lowers [glucose]p by…
Stimulating uptake of glucose by muscle and fat cells Activating liver enzymes to convert glucose into glycogen
HARMONE OF FED STATE
Diabetics can increase GLUT4 expression by doing what?
Exercising
Glucagon increases [glucose]p by…
Increasing glycogenolysis/inhibiting glycogen synthesis
HARMONE OF HUNGRY STATE
Cortisol increases [glucose]p by…
Stimulating protein catabolism, lypolysis and gluconeogenesis
Which receptors control mean arterial BP? Where are the receptors, control centre + effectors located?
Baroreceptors, located in aortic arch + carotid sinus Control centre: CN IX + X to medulla oblongata
Effectors: heart + blood vessels
Normal range for MAP?
Average arterial BP during single cardiac cycle
70-105 mmHg
Formulae for calculating MAP?
MAP = [(2x diastolic) + systolic]/3 MAP = diastolic + [systolic - diastolic]/3 MAP = CO x TPR
MAP of at least __ mmHg is needed to perfuse coronary arteries, brain and kidneys
60 mmHg
Firing rate in baroreceptors ____ when MAP increases
Increases (sensitive to stretch: when you stretch them, firing increases)
What is meant by BP, systolic and diastolic?
Outwards hydrostatic pressure exerted by blood on BV walls
- when heart contracts
- when heart relaxes
Normal arterial BP
<140 systolic, <90 diastolic
Cardiac output (CO) is…
The volume of blood pumped out by each ventricle per minute (SV x HR)
Stroke Volume (SV) is…
Volume of blood pumped out by each ventricle per heart beat
Increasing contractile strength of the heart causes stroke volume to ____
Increase
What is meant by ‘autorhythmicity’?
Heart can beat rhythmically in abscence of external stimuli
Influence of sympathetic and parasympathetic systems on HR and force of contraction…
Increase - NR on B1 receptors, Increase
Decrease - Ach on M receptors, No effect
Main resistance vessels are…
Arterioles
What is ‘total peripheral resistance’ and what is it controlled by?
Sum of all resistance of all peripheral vasculature in systemic circulation
Vascular SM especially arterioles - vasoconstriction (increase), vasodilatation (decrease)
Vasomotor tone is described as…
Caused by?
Vascular smooth muscle being constricted at rest
Tonic discharge of sympathetic nerves
Core body temperature is about…
37.8’C
Basal metabolic rate is defined as…
The minimum amount of energy required to sustain body functions
Which receptors monitor body heat? Where are they, the control centre and effectors located?
Thermoreceptors, located in the hypothalamus (CORE TEMP) and skin (PERIPHERAL TEMP)
Control centre: hypothalamus
Effectors: skeletal muscles, skin arterioles, sweat glands
Mechanisms of heat gain…
Radiation
Convection
Conduction
Mechanisms of heat loss…
Radiation
Convection
Conduction
Evaporation
What contributes to half of total heat loss in the body?
Radiation - emission of energy as electromagnetic waves from a surface
What term is used to describe ‘transfer of heat between objects in contact’?
Conduction
What is convection?
Transfer of heat energy by air/water currents that carry heat away from the body
What term is used to describe ‘the energy required to convert water in skin/ respiratory tract into vapour’
Evaporation
What is the body’s temperature control centre? What parts are activated by the cold and warmth?
Hypothalamus
Cold = Posterior
Warmth = Anterior
Fever is temperature between…
38-40’C
Hyperthermia is temperature…
> 40’C
Hypothermia is temperature below…
35’C
