Task 7 body and behavior
What is homeostasis?
Homeostasis
Homeo = similar (not specific number but a range)
Stasis = condition
Homeostasis = tendency of organism to maintain a physiological and
psychological stability – to regulate internal balance
Negative feedback = process whereby the effect produced by an action
reduces or stops that action
almost all homeostatic control mechanisms are negative feedback
systems
Mammals are endotherms: generate heat internally through metabolism
and muscle activity.
Endothermy allows wider activity and survival compared to ectotherms,
which rely on environmental heat.
Homeostatic systems
Negative feedback:
1. System variable = variable controlled by a regulatory system (e.g.
temperature)
2. Set point/zone = the optimal value/range in the system (e.g. 21
degrees) (usually a range instead of a specific number)
3. Sensor = mechanism that signals when the system variable deviates
form the setpoint (e.g. thermostat)
4. Correctional device/effector = mechanism that changes the system
variable (e.g. radiator)
negative feedback: e.g. heat
* Source: lecture
What controls thirst?
a. Brain areas
b. Why we shouldn’t drink urine and salt water
Drinking and Thirst
Thirst is controlled by physiological regulatory mechanisms that monitor
changes in fluid balance.
Body fluid
Body water/fluid (70%):
- intracellular fluid (67%) = fluid inside the body cells (cytoplasm)
- extracellular fluid (33%) = fluid outside the body cells
, Intravascular fluid: fluid inside blood vessels; blood plasma
Cerebrospinal fluid: fluid that surrounds brain and spinal cord
Interstitial fluid: fluid that surrounds the cells
The volume of two of the fluid compartments of the body must be kept
within precise limits: the intracellular fluid and the intravascular fluid (de
twee systemin waarover je het hieronder hebt!).
Water-dependent systems:
- blood pressure
- chemical reactions
- stimulates digestion
- lubrication of joints
water is crucial for our bodies
Osmosis
How to maintain the equilibrium (state of balance) of water level inside
and outside or cells:
Osmosis = movement of solvent (water) across a semi-permeable
membrane in response to a solute (salt) concentration gradient
- Solvent: particles do the work
- Movement: low high concentration of solute
- Equal concentrations stop
Osmotic pressure = the pressure that would have to be applied to a pure
solvent to prevent it from passing into a given solution by osmosis (often
used to express the concentration of the solution).
, Tonicity:
- Isotonic (equilibrium): solutes is equal in the intracellular and
extracellular compartments cells stays the same
Isotonic drink matches extracellular solute concentration (because
it contains electrolytes), so water is absorbed without moving
excessively in or out of cells, keeping cells stable and well hydrated
2 solutions to gain equilibrium:
- hypertonic: solute is higher outside (extracellular) than in the cell
(intracellular) cells shrink
- hypotonic: solute is lower outside (extracellular) than in the cell
(intracellular) cells swell
Mechanisms to help maintain equilibrium:
- High extracellular solute concentration Mechanisms to loose water:
sweating
respiration
urination
Types of thirst
Two types of thirst are described:
- Osmometric Thirst = a desire to ingest fluids, resulting from a high
extracellular SOLUT CONCENTRATION
Triggered by increased solute concentration in bodily fluids (by
increase in salt (e.g. after salty food) or by water loss)
o higher solute concentration in extracellular fluid (hypertonic)
increased osmotic pressure osmosis: water moves
outside of the cell reduction in cell volume triggers a
change in firing rate signals thirst.
Detected mainly by osmoreceptors in the OVLT and subfornical
organ (SFO).
o These circumventricular organs lack a blood–brain barrier and
directly sense blood chemistry.
What is homeostasis?
Homeostasis
Homeo = similar (not specific number but a range)
Stasis = condition
Homeostasis = tendency of organism to maintain a physiological and
psychological stability – to regulate internal balance
Negative feedback = process whereby the effect produced by an action
reduces or stops that action
almost all homeostatic control mechanisms are negative feedback
systems
Mammals are endotherms: generate heat internally through metabolism
and muscle activity.
Endothermy allows wider activity and survival compared to ectotherms,
which rely on environmental heat.
Homeostatic systems
Negative feedback:
1. System variable = variable controlled by a regulatory system (e.g.
temperature)
2. Set point/zone = the optimal value/range in the system (e.g. 21
degrees) (usually a range instead of a specific number)
3. Sensor = mechanism that signals when the system variable deviates
form the setpoint (e.g. thermostat)
4. Correctional device/effector = mechanism that changes the system
variable (e.g. radiator)
negative feedback: e.g. heat
* Source: lecture
What controls thirst?
a. Brain areas
b. Why we shouldn’t drink urine and salt water
Drinking and Thirst
Thirst is controlled by physiological regulatory mechanisms that monitor
changes in fluid balance.
Body fluid
Body water/fluid (70%):
- intracellular fluid (67%) = fluid inside the body cells (cytoplasm)
- extracellular fluid (33%) = fluid outside the body cells
, Intravascular fluid: fluid inside blood vessels; blood plasma
Cerebrospinal fluid: fluid that surrounds brain and spinal cord
Interstitial fluid: fluid that surrounds the cells
The volume of two of the fluid compartments of the body must be kept
within precise limits: the intracellular fluid and the intravascular fluid (de
twee systemin waarover je het hieronder hebt!).
Water-dependent systems:
- blood pressure
- chemical reactions
- stimulates digestion
- lubrication of joints
water is crucial for our bodies
Osmosis
How to maintain the equilibrium (state of balance) of water level inside
and outside or cells:
Osmosis = movement of solvent (water) across a semi-permeable
membrane in response to a solute (salt) concentration gradient
- Solvent: particles do the work
- Movement: low high concentration of solute
- Equal concentrations stop
Osmotic pressure = the pressure that would have to be applied to a pure
solvent to prevent it from passing into a given solution by osmosis (often
used to express the concentration of the solution).
, Tonicity:
- Isotonic (equilibrium): solutes is equal in the intracellular and
extracellular compartments cells stays the same
Isotonic drink matches extracellular solute concentration (because
it contains electrolytes), so water is absorbed without moving
excessively in or out of cells, keeping cells stable and well hydrated
2 solutions to gain equilibrium:
- hypertonic: solute is higher outside (extracellular) than in the cell
(intracellular) cells shrink
- hypotonic: solute is lower outside (extracellular) than in the cell
(intracellular) cells swell
Mechanisms to help maintain equilibrium:
- High extracellular solute concentration Mechanisms to loose water:
sweating
respiration
urination
Types of thirst
Two types of thirst are described:
- Osmometric Thirst = a desire to ingest fluids, resulting from a high
extracellular SOLUT CONCENTRATION
Triggered by increased solute concentration in bodily fluids (by
increase in salt (e.g. after salty food) or by water loss)
o higher solute concentration in extracellular fluid (hypertonic)
increased osmotic pressure osmosis: water moves
outside of the cell reduction in cell volume triggers a
change in firing rate signals thirst.
Detected mainly by osmoreceptors in the OVLT and subfornical
organ (SFO).
o These circumventricular organs lack a blood–brain barrier and
directly sense blood chemistry.
