PHTY251 (PHYSIOLOGY test 1)

definition of homeostasis

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

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

controlled variable

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

sensor

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

integration center

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

effector

acts to restore the controlled variable to the set point value

negative feedback

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

positive feedback

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

accelerated

the change in the variable with positive feedback

reduced

the change in the variable with negative feedback

physiological and behavioural

feedforward adjustments can be...

features that need to be regulated

homeostatic variables are

15

Na+ in ICF

150

K+ in ICF

7

Cl- in ICF

7.1

pH in ICF

10

bicarbonate conc ICF

275-300

osmolality norm \=

10^-4

conc of free Ca2+ in ICF

145

Na+ in ECF

5

K+ in ECF

100

Cl- in ECF

7.4

pH in ECF

24

Bicarbonate conc in ECF

1

conc of free Ca2+ in ECF

60%

% of TBW for males

55%

% of TBW for females

1/3

ECF TBW

2/3

ICF TBW

1/5 of ECF

plasma

4/5 of ECF

interstitial fluid

K+

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

higher

is Na+ conc higher or lower in the ECF

lower

Is Na+ conc higher or lower in ICF

higher

is K+ conc higher or lower in ICF

lower

Is K+ conc higher or lower in ECF

higher

is Cl- conc higher or lower in ECF

lower

Is Cl- conc higher or lower in ICF

ECF

is there more free Ca2+ in the ICF or ECF

pinocytosis, phagocytosis, receptor-mediated endocytosis

three forms of endocytosis

pinocytosis

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

phagocytosis

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

receptor-mediated endocytosis

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

Exocytosis

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

integral memrbane proteins

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

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

phospholipid bilayer

the plasma membrane is composed of

proteins and cholesterol

things embedded in the phospholipid bilayer

water soluble substances

the plasma membrane restricts the movement of...

diffusion

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

the amount of substance crossing given surface area per unit time

flux definition

concentration, electrical or osmotic gradient

types of gradients to allow simple diffusion

concentration gradient

in simple diffusion flux only is limited by

facilitated diffusion

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

requires energy

active transport

primary active transport

Active transport that relies directly on the hydrolysis of ATP.

secondary active transport

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

Osmosis

Diffusion of water through a selectively permeable membrane

the sum of all the solute particles dissolved in the solution

osmolarity

hyposmotic

solution with a lesser concentration of solute

hyperosmotic

solution with a greater concentration of solute

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

tonicity

shrink

a hypertonic solution will cause the cell to

swell

a hypotonic solution will cause the cell to

haemolysis

bursting of red blood cells

a bundle of fascicles

a whole nerve is

Epineurium

surrounds the entire nerve

perineurium

surrounds each fascicle

Endoneurium

surrounds each nerve fiber

multipolar neuron

multiple inputs at soma (motor neurons, CNS)

unipolar neuron

dendrites further from the cell body (sensory neurons)

anaxonic neuron

many dendrites but no axon (CNS neurons)

Neurotransmitters

chemical messengers that cross the synaptic gaps between neurons

motor unit

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

1 motor unit

each muscle fiber is under the control of

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?

back into SR

what happens to Calcium during relaxation of muscle cells

The myosin head to become cocked

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

Ca2+ and ATP

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

troponin

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

tropomyosin

covers myosin binding sites on the actin molecules

schwann cells

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

Autrophy

a muscle fiber that will no longer be innervated will

Axonal sprouting

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

hyperresponsiveness

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

hyporesponsiveness

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

long term potentiation

gradual strengthening of the connections among neurons from repetitive stimulation

long term depression

the long-lasting decrease in the strength of synaptic transmission

growth cone

the growing tip of an axon

filopodia

very fine, tubular outgrowths from the growth cone

recruitment

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

motor unit

A motor neuron and all of the muscle fibers it innervates

less precise control

A motor neuron controlling perhaps MANY muscle fibers has

isometric contraction

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

isotonic contraction

there is a change in the muscle length during contraction

muscle shortens

concentric contraction

muscle lengthens

eccentric contraction

twitch

single stimulus-contraction-relaxation sequence in a muscle fiber

summation

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

incomplete tetanus

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