HOMEOSTASIS
Created Jun 1, 2019 414 PM
Tags
Updated Jun 1, 2019 438 PM
HOMEOSTASIS
~ What is homeostasis?
it is the maintenance of a stable internal environment, to maintain normal
healthy function of the body's cells
the body is in homeostasis when its needs are met and are functioning
properly
it does not involve keeping conditions static
it is keeping conditions within a tightly regulated physiological range
every organ system constributes to homeostasis
but endocrine and nervous systems are particularly important
a loss of homeostasis is reflected in ill health
~ Feedback Loop
homeostasis is often maintained through the principle of feedback
mechanism
is a control system that acts to maintain the level of some variable
within a given range following a disturbance
components of feedback loop:
sensor
afferent pathway
control centre
controller
sets the level of a variable (physiological range)
upper brain centres
HOMEOSTASIS 1
, comparator
compares the set level of a variable with the signal from receptor
output usually an opposite influence to the signal
except for some variables, eg. giving birth and micturition
effector (target organs)
efferent pathway
there is always continuous real-time communication between receptor,
control centre and effector
how the feedback loop works:
when the body is in homeostasis:
the set levels of all variables are within physiological range
there is a dynamic balance (no difference) between set level and
input at the comparator
when there is a different between the set level and input at comparator:
output to target organs will modulate the variable
there are two types of feedback loops
Negative feedback
the output (change) is in the opposite direction as the original
stimulus
reduces the output of a system
decrease in function in response to stimulus
variables are restored to the steady state
Positive feedback
the output (change) is in the same direction as the original stimulus
increases in function in response to stimulus
enhances the stimulus
~ Negative Feedback Loop
an external factor causes the input variable to decrease/increase
HOMEOSTASIS 2
, the sensor registers a decreased/increase signal and sends the information
to comparator
comparator output acts to increase/decrease the value of the variable to
the target organs
Example:
low blood pressure
arterial blood pressure is reduced
baroreceptors register the reduced signal
the sinus nerve sends signals to comparator in a reduced manner
the medullary cardiovascular centres send signals to increase blood
pressure
arterioles
SA node and myocardium (heart)
water balance
drinking 2 liters of water in 30 minutes
plasma osmolality is reduced
osmoreceptors register decreased plasma osmolality
hypothalamus receives reduced signals and send signals to kidney
decrease water reabsorption in collecting duct of kidneys
micturition of less concentrated urine
HOMEOSTASIS 3
, ELECTROLYTE AND FLUID
BALANCE
Created Jun 1, 2019 439 PM
Tags
Updated Jun 1, 2019 528 PM
ELECTROLYTE AND FLUID BALANCE
~ What is the human body composed of?
solid matter
tissue and bones
makes up 40% of total body weight
intracellular fluid
makes up 40% of total body weight
extracellular fluid
plasma, lymph, cerebrospinal fluid, fluid in GI tract, synovial fluid
makes up 20% of total body weight
~ Body Fluid Compartments
The total body water content is about 42 L 60% of total body weight)
Intracellular Fluid ICF - 2/3 Total Body Weight
the fluid within cells, also known as cytoplasm
28 L in a 70 kg young male
67% of total body water
Extracellular Fluid ECF - 1/3 Total Body Weight
the fluid found outside cells
14 L in a 70 kg young male
made up of 3 different fluid groups:
Plasma
ELECTROLYTE AND FLUID BALANCE 1
Created Jun 1, 2019 414 PM
Tags
Updated Jun 1, 2019 438 PM
HOMEOSTASIS
~ What is homeostasis?
it is the maintenance of a stable internal environment, to maintain normal
healthy function of the body's cells
the body is in homeostasis when its needs are met and are functioning
properly
it does not involve keeping conditions static
it is keeping conditions within a tightly regulated physiological range
every organ system constributes to homeostasis
but endocrine and nervous systems are particularly important
a loss of homeostasis is reflected in ill health
~ Feedback Loop
homeostasis is often maintained through the principle of feedback
mechanism
is a control system that acts to maintain the level of some variable
within a given range following a disturbance
components of feedback loop:
sensor
afferent pathway
control centre
controller
sets the level of a variable (physiological range)
upper brain centres
HOMEOSTASIS 1
, comparator
compares the set level of a variable with the signal from receptor
output usually an opposite influence to the signal
except for some variables, eg. giving birth and micturition
effector (target organs)
efferent pathway
there is always continuous real-time communication between receptor,
control centre and effector
how the feedback loop works:
when the body is in homeostasis:
the set levels of all variables are within physiological range
there is a dynamic balance (no difference) between set level and
input at the comparator
when there is a different between the set level and input at comparator:
output to target organs will modulate the variable
there are two types of feedback loops
Negative feedback
the output (change) is in the opposite direction as the original
stimulus
reduces the output of a system
decrease in function in response to stimulus
variables are restored to the steady state
Positive feedback
the output (change) is in the same direction as the original stimulus
increases in function in response to stimulus
enhances the stimulus
~ Negative Feedback Loop
an external factor causes the input variable to decrease/increase
HOMEOSTASIS 2
, the sensor registers a decreased/increase signal and sends the information
to comparator
comparator output acts to increase/decrease the value of the variable to
the target organs
Example:
low blood pressure
arterial blood pressure is reduced
baroreceptors register the reduced signal
the sinus nerve sends signals to comparator in a reduced manner
the medullary cardiovascular centres send signals to increase blood
pressure
arterioles
SA node and myocardium (heart)
water balance
drinking 2 liters of water in 30 minutes
plasma osmolality is reduced
osmoreceptors register decreased plasma osmolality
hypothalamus receives reduced signals and send signals to kidney
decrease water reabsorption in collecting duct of kidneys
micturition of less concentrated urine
HOMEOSTASIS 3
, ELECTROLYTE AND FLUID
BALANCE
Created Jun 1, 2019 439 PM
Tags
Updated Jun 1, 2019 528 PM
ELECTROLYTE AND FLUID BALANCE
~ What is the human body composed of?
solid matter
tissue and bones
makes up 40% of total body weight
intracellular fluid
makes up 40% of total body weight
extracellular fluid
plasma, lymph, cerebrospinal fluid, fluid in GI tract, synovial fluid
makes up 20% of total body weight
~ Body Fluid Compartments
The total body water content is about 42 L 60% of total body weight)
Intracellular Fluid ICF - 2/3 Total Body Weight
the fluid within cells, also known as cytoplasm
28 L in a 70 kg young male
67% of total body water
Extracellular Fluid ECF - 1/3 Total Body Weight
the fluid found outside cells
14 L in a 70 kg young male
made up of 3 different fluid groups:
Plasma
ELECTROLYTE AND FLUID BALANCE 1
