homeostasis Flashcards
what is homeostasis
is the state of steady internal, physical, and chemical conditions maintained by living systems
The process by which the body reacts to changes in order to keep conditions inside the body, for example temperature, the same
what is the
homeostatic range
the condition of optimal
functioning for the organism
and includes many variables,
such as body temperature and
fluid balance, being kept within
certain pre-set limits- the
homeostatic range
factors homeostatically regulated
conc of nutrient molecules, CO2 O2, waste products, water, salt, other electrolytes
Volumes and pressure
Temperature
pH
Homeostatic control System definition
is a functionally interconnected network of body components that operate to maintain a given physical/ chemical factor in the internal environment relatively constant around an optimal level
how can homeostatic control systems be classified
intrinsic + Extrinsic
- inherent compensatory responses of an organ to a change
- responses of an organ that are triggered by factors external to the organ by the nervous/endocrine systems
what principles do the types of homeostatic controls generally operate on
Negative/ Positive/Feed forward mechanism
what is positive feedback
the output is continually enhanced/amplified so that the controlled variable continues to be moved in the direction of the initial change or a pathway in which the response reinforces the stimulus
Negative feedback
homeostatic control factor triggers a response that seeks to restore the factor to normal by moving the factor in the opposite direction of its initial change or it is a pathway where the response opposes or removes the the signal.
what does the Negative feedback loop require
sensor, set point and effector
if sensor does not equal set point = error signal = restore variable to desired level
limitations of negative feedback
initiated after variable has been disturbed
Amount of correction to be applied assessed by magnitude of
error signal –> incomplete correction
Overcorrection –> oscillations in controlled variable
how the negative feedback disadvantages overcome
Disadvantages overcome by multiple regulatory mechanisms
What is the multiple regulatory mechanisms:
involuntary (paracrine, endocrine, ANS and CNS)
voluntary (CNS)
positive feedback for labour
onset of labour, oxytocin released from hypothalamus, increased uterine contractions, Baby’s head pushed through cervix, stretch of cervix, more oxytocin released, interested uterine contractions
rising phase of action potential process and is it an example of positive or negative feedback
positive feedback example
depolarisation, opens Na channels, Na entry, Further depolarisation, UNTIL STOP when Na channels inactive
Feedforward Mechanism
It brings about compensatory response in anticipation of a change in regulated variable
example of feedforward mechanism
increased production of saliva and gastric secretions at smell and sight of food
example of feed forward and anticipatory change - renal
Changes in renal function in preparation for changes brought on
by food intake resulting in changes in concentration of ions in the
plasma that will need to be controlled within physiological range
what does the ER do
Synthesis and transport of
membrane proteins and lipids
what does golgi apparatus do
Synthesis and packaging of secretory
molecules; membrane protein
targeting
what does the plasma membrane contain
contains membrane proteins which transport
water, ions and hydrophilic
molecules
differences between the transport capacity of channel & carrier proteins
CH: high capacity for transport (10^8 ions/second)
CA: Lower transport capacity than channels (102-103
molecules/second
which protein carries ions and which molecules
CH: ions
CA: molecules
what kind of proteins are Channel proteins compared to carrier
CH : lipoproteins
CA : Glycoproteins
what is the examples of simple diffusion/ Facilitated diffusion/ active transport
CO2, O2
GLUT transporter
Na+/K+ pump
difference between simple diffusion, facilitated diffusion and active transport
SD & FD: down conc. gradient, no ATP required
AT: against conc. gradient, ATP required
ion composition of intra vs extracellular fluid: describe direction of movement of these ions across the cell membrane K+, Na+, Ca2+, Cl-
K+ 150 –> 5 moves out
Na+ 15 –> 150 moves in
Ca2+ 0.001 –> 1 moves in
Cl- 10 –>110 moves in
what are the 2 types of ion channels
gated channels and open channels
what are the types of gated channels
what are mechanically gated, voltage gated and ligand gated channels
characteristics of open channels
known as leak channels or pores
Usually open
Allow ions to move back and forth across the membrane
what is a important example of an open channel
K+ channels
difference between all the gated channels
MG: response to physical force e.g. temp, pressure
e.g. TRAAK channels
VG: response to changes in membrane potential
e.g. voltage-gated Na+
channels
LG: response to binding of a
of a ligand (hormone,
neurotransmitter)
e.g. nicotinic
acetylcholine receptors
classification of carrier proteins
Uniport carriers
Symport carriers
Antiport carriers
what is a uniport carrier
Transports one type of
substrate
* e.g. GLUT transporter
what is a symport carrier
Transports two or more
substrates in the same
direction
* e.g. sodium-glucose
linked transporter (SGLT)
what is an antiport carrier
Transports substrates in
different directions
* e.g. Na+/K+ pump
what is an SGLT inhibitor
- SGLT inhibitors block glucose reabsorption in
the proximal tubule of the kidneys - Glucose excreted in urine
- Reduces hyperglycaemia
how are SGLT inhibitors used within industry
Widely used in the treatment of type II
diabetes
what is the The Na+/K+ ATPase
Antiport carrier
Maintains of low intracellular [Na+]
and high [K+], within in all mammalian cells, electrogenic
what does electrogenic mean
makes inside of cell
more negative
different Role of transport proteins in cellular homeostasis
Involved in:
* Ionic composition of intracellular fluid → osmolarity
* Cell volume
* Intracellular pH
* Intracellular [Ca2+]
* Membrane potential
what does osmolarity describe
the number of particles in solution
what determines extra/intracellular osmolarity
Extracellular osmolarity → inorganic ions (Na+, K+, Cl-)
* Intracellular osmolarity → inorganic ions, membrane impermeant molecules
(e.g. proteins, ATP)
what is increased intracellular osmolarity & Decreased intracellular osmolarity called
I: osmotic influx of water → cell swelling
D: osmotic efflux of water → cell shrinking
what would occur without transporters
lysis due to accumulation of ions
what is the average intracellular/ Extracellular pH
Intracellular pH ~ 7.0-7.2
Extracellular pH ~ 7.4
what type of processes are used to decrease intracellular pH
Metabolic processes produce acidic byproducts → decrease intracellular pH
what are the principle regulatory mechanisms used to maintain intracellular pH
- Na+/H+ exchange
- Na+-HCO3- co-transport
- Cl-/HCO3- exchange
why is there a regulation of intracellular calcium
as it is used as trigger for many cellular processes, maintained very low → regulatory mechanisms
process of regulation of intracellular calcium
- Plasma membrane Ca2+ ATPase pumps Ca2+ out of cell
- Na+/Ca2+ exchanger transports Ca2+ out of cell across plasma membrane
in exchange for Na+ coming into cell (down electrochemical gradient
generated by Na+/K+ ATPase) - Ca2+ ATPase pumps Ca2+ into intracellular stores (ER and mitochondria)
- Stored Ca2+ released in response to signals from plasma membrane
how is the resting membrane potential achieved
K+ continually leaks out down its concentration
gradient (established by the Na+/K+ pump) which builds
up an electrical gradient
an equilibrium will be reached where the electrical
gradient is exactly equal and opposite to the
concentration gradient
which part of the cell is usually negative
inside of the cell -70mV, dominated by K+
