- Net diffusion of water down its concentration gradient - conc. of osmotically active particles in a solution - aquaporins are water channels

Physiology Flashcards by Sarah Black

what is the hydrophilic bilayer composed of

hydrophilic heads

- hydrophobic tails

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what is the role of cholesterol in the cell membrane

contributes to fluidity and stability

- stiffens membrane

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what are the 3 possible locations of proteins in/around cell membrane

integral (embedded within)
peripheral (don’t penetrate membrane)
transmembrane (extend through membrane)

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what is the location of carbohydrates in relation to the cell membrane and what types are there

small amount located on outer surface

- glycoproteins, glycolipids

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what are the 3 functions of the lipid bilayer

basic structure of membrane
hydrophobic interior acts as barrier
responsible for membrane fluidity

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The glycocalyx layer is formed by…

Short carbohydrate chains bound to proteins and lipids

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what are the main functions of proteins

water filled, selective ion channels
carrier/transport proteins
docking/marker acceptors
receptors or enzymes
cell adhesion molecules

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what are the 2 types of cell adhesion molecules

Cadherins (hold cells within tissues together)

- Integrins (span membrane to link intra and extracellular environments)

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what are occlusion/tight junctions

join neighbouring cells together to prevent diffusion

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what are anchoring/desmosome junctions

they provide mechanical support, anchor cells together

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what are communicating/gap junctions

they create pores to allow the movement of molecules between 2 cells

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what are the 2 types of passive transport

diffusion

- electrical gradient

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during passive transport where do cations move to

cations move towards -vely charged areas

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what does Fick’s Law of diffusion relate to

size of concentration gradient
surface area of membrane
lipid solubility
molecular weight
distance for diffusion

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what is an electrochemical gradient

Where an electrical and a chemical concentration gradient may be acting on a particular ion at the same time

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define osmosis

Net diffusion of water down its concentration gradient
conc. of osmotically active particles in a solution
aquaporins are water channels

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how is osmolarity calculated

Using molar concn (mM) and number of osmotically active particles (n)

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150mM NaCl has osmolarity = ?

150 x 2 (Na+ and Cl-) = 300mOsm

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define tonicity

effect a solution has on cell volume

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what effect does a hypotonic solution have on cell volume

increases cell volume

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what effect does a hypertonic solution have on cell volume

decreases cell volume

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what happens during carrier-mediated transport

substance binds to specific carrier and changes its conformation to transport it

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what effects carrier-mediated transport

specificity
saturation
competition

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what is facilitated diffusion

no energy required
carrier-mediated
from high to low conc.

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what is active transport

- energy required | - from low to high conc.

what is primary active transport

energy directly required

what is secondary active transport

- energy required but not used directly | - energy stored in form of ION CONC. GRADIENT (usually Na+)

what are the mechanisms of secondary active transport

- symport (same direction) | - antiport (opposite direction)

what is vesicular transport

- energy for vesicle formation | - endocytosis or exocytosis

what type of active transport is is NaKATPase pump

- primary active transport

_ Na+ out for every _ K+ in with regards to Na-K pump

3, 2

3 roles of NAKATPase pump

- Establish Na and K concentration gradients across - regulate cell volume - energy source

what is the membrane potential (Em)

- separation of charges across membrane | - units are mV

what are the direction of Na and K ion movements

- K moves outwards | - Na moves inwards

at resting potential the membrane is 100x more permeable to what

more permeable to K than Na

describe movement of K+ ions

- K+ move down con gradient out of cell - still negative anions inside cell - results in electrical gradient moving K+ back into cell

describe movement of Na+ ions

- Na+ move down conc gradient into cell - still negative anions outside cell - results in electrical gradient moving Na+ out of cell

what is the membrane potential of Ek

-90mV

what is the membrane potential of Ena

+61mV

what does the Nernst equation calculate

membrane potential of a single ion

what does the Goldman - Hodgkin - Katz equation calculate

overall membrane potential

what is the resting membrane potential of a typical nerve cell

- 70mV

is the resting membrane potential nearer to Ek or Ena

- Ek | - not exactly the same due to slight inward leak of Na

Na channels are... | K channels are....

``` Na = depolarisation K = repolarisation ```

define action potentials

brief electrical signals in which the membrane polarity is momentarily reversed - spread along with constant size and velocity

glucose is a...

metabolic fuel

hormones controlling glucose in absorptive and post absorptive states are..

insulin and glucagon | pancreas

hormones controlling glucose in emergencies are...

adrenaline | adrenal gland

hormones controlling glucose in starvation are...

cortisol (adrenal) and growth hormone (pituitary gland)

name the pancreatic islets of Langerhans (endocrine cells)

- alpha cells = glucagon - beta cells = insulin - delta cells = somatostatin

What are the absorptive states

- increased glucose levels - insulin rises - glucagon falls

what does insulin favour and what does it do

- favours anabolism | - converts glucose > glycogen

insulin is a hormone of what state

the fed state

diabetes mellitus type 1 has what properties

- early onset - no insulin secretion - defect in beta cells - insulin injections required

diabetes mellitus type 2 has what properties

- adult onset - insulin secretion may be normal - defect in insulin sensitivity - diet/exercise/oral drugs

Diabetics can increase GLUT4 expression by doing what?

exercise

the pulse pressure is the difference between what

systolic and diastolic BP's

what is the normal MAP range

70-105

how do you calculate MAP

``` MAP = [(2x diastolic) + systolic]/3 MAP = diastolic + [systolic - diastolic]/3 MAP = CO x SVR ```

Which receptors control mean arterial BP and where are the receptors

Baroreceptors, located in aortic arch + carotid sinus

what is the control centre used by baroceptosr and what are the effectors

control centre = medulla | effectors = heart and blood vessels

MAP of at least __ is needed to perfuse heart, brain, kidneys

60mmHg

MAP needs to be low enough so that it doesn't...

damage blood vessels

what happens to the firing rate in baroreceptors when MAP increases

firing rate also increases

Cardiac Output is

- The volume of blood pumped out by each ventricle per minute - (SV x HR)

Stroke Volume is

- the volume of blood pumped out by each ventricle per heart beat

Increasing contractile strength of the heart causes stroke volume to ____

increase

Vasomotor tone is described as what

Vascular smooth muscle being constricted at rest

define homeostasis

maintenance of a stable internal environment

to maintain homeostasis you must be able to do what

- sense deviations from normal - integrate this information - make appropriate adjustments to restore variable

what are intrinsic controls

within organ

what are extrinsic controls

- outside organ | - use nerves and hormones

define feedforward

responses made in anticipation of change

define feedback

responses made after change has occurred

define negative feedback

- opposes initial change | - eg controlling body temp.

define positive feedback

- amplifies initial change | - eg uterus contractions become stronger until birth

what is the core body temperature

37.8 degrees

what is normothermia

when body temperature varies during day (lowest in early morning)

define basal metabolic rate

minimum energy required to sustain body functions

how can the basal metabolic rate be increased

- hormones eg adrenaline | - muscle activity/shivering

what are the 4 methods of heat gain

- metabolic heat - radiation - convection - conduction

what are the 4 methods of heat loss

- convection - conduction - radiation - evaporation

pOsterior hypothalamus is activated by what

cOld

Anterior hypothalamus is activated by what

wArmth

Which receptors monitor body heat? Where are they, the control centre and effectors located?

- Thermoreceptors - located in the hypothalamus and skin - Control centre: hypothalamus - Effectors: skeletal muscles, skin arterioles, sweat glands

a fever is a temperature between what

38-40 degrees

hyperthermia is a temperature between what

>40 degrees

hypothermia is a temperature between what

35 or below degrees