What is physiology? - ✔️✔️the study of normal functioning of a living organism and its component parts,
including all its chemical and physical processes
Physiology means "Knowledge of nature"
Cells - ✔️✔️smallest unit of structure capable of carrying out life processes
Tissue - ✔️✔️collection of cells carrying out related functions
Organ - ✔️✔️formation of tissues into a structural and functional unit
Organ system - ✔️✔️integrated groups of organs
Emergent properties - ✔️✔️Properties of complex systems can not be explained by the knowledge of all a
systems all individual parts. The interaction between all the parts and the structure give the system its
function. The reaction results from complex, nonlinear interactions.
Emergent properties examples - ✔️✔️The nervous system can not be explained by just studying the brain,
but the brain needs to be functioning with all its parts in order to perform and have functions like
emotion or intelligence.
The genome project: researchers believed that if we study every single gene, we will be able to cure all
diseases but every gene is made of up different amino acids, splicing and control but it does not work.
Integration between different body systems - ✔️✔️All the body systems and organs work together to
maintain homeostasis and other essential systems as they are related to one and other.
,Function vs. Mechanism in physiology - ✔️✔️Function is the why (teleological)
Mechanism is the how
Physiology is more concerned with mechanistic approach
Homeostasis - ✔️✔️home (like or similar) stasis (condition) is the ability to maintain a relatively stable
internal environment despite exposure to external variability.
Some researchers want to argue thats its homeodynamics because things are always moving around
that need to be maintained like bp, body temp etc
Homeostasis and disease - ✔️✔️External or internal change can affect the homeostasis which causes an
internal change and results in loss of homeostasis. If organism attempts to compensate, then it leads to
normal functioning again but if not, it leads to illness or disease
What external changes lead to a loss of homeostasis - ✔️✔️Toxic chemicals
Physical trauma
Foreign invaders (Bacteria or viruses)
What internal changes lead to a loss of homeostasis - ✔️✔️Abnormal cell growth (cancer or tumours)
Autoimune disorders
Genetic disorders
Pathophysiological state - ✔️✔️The changes that occur during a disease or illness process
Why do we need to maintain an internal balance? - ✔️✔️Constancy is important because most cells in the
body are delicate and cannot tolerate to changes in their environment
What is considered the internal environment? - ✔️✔️Extracellular fluid (ECF)
,Extracellular fluid (ECF) - ✔️✔️Fluid outside the cells that acts as a buffer between cells and the external
environment (includes blood plasma and interstitial fluid)
External environment --> Extracellular fluid --> Intracellular fluid - ✔️✔️There is dynamic movement
between all three all the time (back and forth)
What is the law of mass balance? - ✔️✔️if the amount of a substance in the body is to remain constant,
any gain must be offset by an equal loss. Homeostasis depends on mass balance.
Does homeostasis mean equilibrium? - ✔️✔️No, even at physiological homeostasis there will be Chemical
and Electrical Disequilibrium
Control systems and homeostasis - ✔️✔️To maintain homeostasis the body monitors certain key
functions/variables
Regulated variables kept within a normal range by control mechanisms
Control systems can be i. local or ii. reflex
Local control - ✔️✔️Restricted to a few cells or small tissues in a small area in the body. Local control
systems allow quick and precise adjustments to be made in the specific region.
Local control Example - ✔️✔️In a localized area of the body, there are highly active cells undergoing
intense metabolic processes, which result in a significant consumption of oxygen. This heightened
cellular activity leads to a drop in oxygen levels within that specific region. As a response to this reduced
oxygen concentration, the endothelial cells in the area detect the low oxygen levels and send local
signals.
Reflex control - ✔️✔️Changes widespread throughout the body (systemic) use more complex control
systems to maintain homeostasis, eg. Blood pressure
Any long-distance pathway that uses the nervous system, endocrine system, or both
Its broken down into two parts (Response loop and Feedback loop)
, It can be antagonistic (i.e heater and air conditioner)
Response loop - ✔️✔️The response alters the initial stimulus. Removes the negative stimulus thats driving
the homeostasis away but thats not always the case because we do have some positive reflex systems.
Ex:
When your body temperature rises, you may sweat to release heat; if too much heat escapes, you may
end up feeling too cold, which will cause your muscles to shiver in an effort to make you warmer
Feedback loop - ✔️✔️Regulate (modulate) the response loop and feeds back to ultimately influence the
input
Three types of Reflex control - ✔️✔️Negative feedback
Positive feedback
Feedforward control
Negative feedback loop - ✔️✔️A pathway in which the response opposes or removes the stimulus signal is
known as negative feedback. It can restore the initial state but cannot prevent the initial disturbance
(Insulin and liver example). It stabilizes a system (Homeostatic)
Negative feedback loops-blood glucose concentration - ✔️✔️When blood in glucose is increased, the
insulin recreates cells
If glucose in not available, glucagon goes in the liver and makes glucose
example of two antagonistic negative feedback loops to maintain variable within a narrow range
Positive feedback loop - ✔️✔️They are NOT homeostatic. Reinforce a stimulus to drive the system away
from a normal value rather than decreasing or removing it requires intervention or event outside the
loop to cease the response.
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