PHTY251 (PHYSIOLOGY test 1)

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definition of homeostasis

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347 Terms

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definition of homeostasis

the maintenance of a relatively constant and optimal environment for the normal functioning of the cells of the body

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homeostasis

the ability of an organism to maintain their internal environment within the limits required for the survival in the face of varying external environments

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controlled variable

the variable that the system tries to keep in a steady state

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sensor

detects changes in the controlled variable and sends this information to the integration centre

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integration center

compares the detected to the set point, transfers info between the components of the system

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effector

acts to restore the controlled variable to the set point value

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negative feedback

control system that acts to make the deviation from the set point SMALLER

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positive feedback

control system that acts to make the deviation of the variable BIGGER

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accelerated

the change in the variable with positive feedback

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reduced

the change in the variable with negative feedback

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physiological and behavioural

feedforward adjustments can be...

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features that need to be regulated

homeostatic variables are

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13

15

Na+ in ICF

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14

150

K+ in ICF

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15

7

Cl- in ICF

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16

7.1

pH in ICF

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17

10

bicarbonate conc ICF

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18

275-300

osmolality norm =

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19

10^-4

conc of free Ca2+ in ICF

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20

145

Na+ in ECF

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21

5

K+ in ECF

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22

100

Cl- in ECF

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23

7.4

pH in ECF

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24

24

Bicarbonate conc in ECF

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25

1

conc of free Ca2+ in ECF

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26

60%

% of TBW for males

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27

55%

% of TBW for females

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28

1/3

ECF TBW

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29

2/3

ICF TBW

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30

1/5 of ECF

plasma

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31

4/5 of ECF

interstitial fluid

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32

K+

Are cell membranes more permeable to Na+ or K+?

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33

higher

is Na+ conc higher or lower in the ECF

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34

lower

Is Na+ conc higher or lower in ICF

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35

higher

is K+ conc higher or lower in ICF

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36

lower

Is K+ conc higher or lower in ECF

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37

higher

is Cl- conc higher or lower in ECF

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lower

Is Cl- conc higher or lower in ICF

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39

ECF

is there more free Ca2+ in the ICF or ECF

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40

pinocytosis, phagocytosis, receptor-mediated endocytosis

three forms of endocytosis

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41

pinocytosis

solutes and water are non specifically brought into the cell from the ECF via vesicles

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phagocytosis

specialised cells form extensions around the membrane which engulf bacteria or debris. The vesicles then fuse with lysosomes that destroy the vesicle contents

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receptor-mediated endocytosis

specific process where the binding of an extracellular molecule to a receptor in the plasma membrane triggers the process

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Exocytosis

membrane bound vesicles fuse with the plasma membrane discharging their contents outside the cell

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integral memrbane proteins

form a selective channel or pore through which water soluble substances may pass into/out of the cell

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peripheral membrane proteins

proteins associated with one side of the membrane. often have an important role in anchoring the membrane to the cytoskeleton & to the extracellular environment

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phospholipid bilayer

the plasma membrane is composed of

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48

proteins and cholesterol

things embedded in the phospholipid bilayer

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water soluble substances

the plasma membrane restricts the movement of...

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50

diffusion

Movement of molecules from an area of higher concentration to an area of lower concentration.

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the amount of substance crossing given surface area per unit time

flux definition

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concentration, electrical or osmotic gradient

types of gradients to allow simple diffusion

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concentration gradient

in simple diffusion flux only is limited by

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facilitated diffusion

process of diffusion in which molecules pass across the membrane through cell membrane channels

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requires energy

active transport

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primary active transport

Active transport that relies directly on the hydrolysis of ATP.

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secondary active transport

transport is coupled to ion diffusion down a concentration gradient established active transport

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Osmosis

Diffusion of water through a selectively permeable membrane

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the sum of all the solute particles dissolved in the solution

osmolarity

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hyposmotic

solution with a lesser concentration of solute

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hyperosmotic

solution with a greater concentration of solute

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the ability of a surrounding solution to cause a cell to gain or lose water

tonicity

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shrink

a hypertonic solution will cause the cell to

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swell

a hypotonic solution will cause the cell to

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haemolysis

bursting of red blood cells

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a bundle of fascicles

a whole nerve is

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Epineurium

surrounds the entire nerve

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perineurium

surrounds each fascicle

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Endoneurium

surrounds each nerve fiber

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multipolar neuron

multiple inputs at soma (motor neurons, CNS)

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unipolar neuron

dendrites further from the cell body (sensory neurons)

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anaxonic neuron

many dendrites but no axon (CNS neurons)

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Neurotransmitters

chemical messengers that cross the synaptic gaps between neurons

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motor unit

a single motor neuron and the multiple muscle fibers it controls.

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1 motor unit

each muscle fiber is under the control of

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76

rotates which motor units are activated at any one time

how do muscles that have to contract for long periods of time, make use of recruitment to help them?

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back into SR

what happens to Calcium during relaxation of muscle cells

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The myosin head to become cocked

the energy being released by the ATP being split into ADP and P during cross-bridge cycling causes

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Ca2+ and ATP

the cross-bridge cycle requires both .... to continue

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troponin

Ca2+ binds to what when release from the SR during an AP

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tropomyosin

covers myosin binding sites on the actin molecules

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schwann cells

cells that play an important role in the support, maintenance & regeneration of nerve fibres after injury

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Autrophy

a muscle fiber that will no longer be innervated will

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Axonal sprouting

Undamaged axons grow new nerve endings to reconnect neurons whose links were injured or severed.

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hyperresponsiveness

stimulation that lasts hours to days causing long term potentiation (more sensitive)

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hyporesponsiveness

inhibition that lasts hours to days causing long term depression (less sensitive)

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long term potentiation

gradual strengthening of the connections among neurons from repetitive stimulation

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long term depression

the long-lasting decrease in the strength of synaptic transmission

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growth cone

the growing tip of an axon

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filopodia

very fine, tubular outgrowths from the growth cone

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recruitment

when the number of motor units activated at any one time can be varied to change the amount of force produced

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motor unit

A motor neuron and all of the muscle fibers it innervates

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less precise control

A motor neuron controlling perhaps MANY muscle fibers has

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94

isometric contraction

Muscle contracts but there is no movement, muscle stays the same length

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isotonic contraction

there is a change in the muscle length during contraction

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96

muscle shortens

concentric contraction

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97

muscle lengthens

eccentric contraction

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98

twitch

single stimulus-contraction-relaxation sequence in a muscle fiber

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99

summation

increased force of contraction by a skeletal muscle fiber when a twitch occurs before the previous twitch relaxes

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100

incomplete tetanus

a muscle fibre producing maximum tension during rapid cycles of contraction & relaxation

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