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homeostasis- physiology Cheat Sheet (DRAFT) by

a cheat sheet for physiology covering the topic of homeostasis

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Key Concepts

Homeos­tasis
- the mainte­nance of a stable internal enviro­nment despite external changes
 
Components of a homeos­tatic system
- Sensor (Recep­tor): Detects changes in the enviro­nment (e.g., thermo­rec­ept­ors).
 
-Integ­rator (Control Center): Compares the detected change to a set point (e.g., hypoth­ala­mus).
 
-Effector: Produces a response to correct deviations (e.g., sweat glands, muscles).
 
Negative Feedback loops
- Counte­racts changes from the set point.
 
- Example: Thermo­reg­ulation – if body temp rises, mechanisms lower it.
Positive Feedback Loops
- Amplify changes rather than reverse them.
 
- Example: Childb­irth, oxytocin increases contra­ctions.
Set Points
- Optimal values for physio­logical parameters (e.g., 98.6°F for body temper­ature).
 
- Can be influenced by circadian rhythms, age, or disease.

Intrinsic Control Systems

Intrinsic (local) control systems are “built in” to an organ or tissue.
e.g., Increased CO 2 production by exercising skeletal muscle leads to relaxation of smooth muscle and dilation of blood vessels, increased blood flow brings more O 2
 

Negative Feedback Loop

Positive feedback Loop

Extrinsic Control Systems

Extrinsic control systems are contained outside of an organ or system, permitting coordi­nated regulation of several organs
Example: Low blood pressure is detected by the nervous system, which causes an increase in heart rate and constr­iction of blood vessels
 
Example: high blood glucose is detected by the endocrine system which exerts hormonal control [insulin]

Fluid Exchange

In order to maintain homeos­tasis, cells exchange materials from the intrac­ellular fluid, with the inster­stitial fluid and blood (speci­fically plasma)
Plasma-
Makes up about 55% of total blood volume, holds the blood cells in suspen­sion.
 
Plasma is about 90–92% water, the rest includes:
 
- proteins
 
-elect­rolytes
 
-nutrients
 
-hormones
 
-waste products
 
-clotting factors
 

Physio­logical Parameters

Parameter
Normal Range
Regulated by
Body Temper­ature
~37°C (98.6°F)
Nervous + Integu­mentary
Blood pH
7.35–7.45
Respir­atory + Renal
Blood glucose
70–110 mg/dL
Endocrine
Blood Pressure
~120/80 mmHg
Cardio­vas­cular + Nervous
Plasma Osmalarity
~300 mOsm/L
Renal + Endocrine
Calcium
8.5–10.5 mg/dL
Parath­yroid hormone, Calcitonin

Ex. Cardio­cas­cular System

Thermo­reg­ulation
Receptors
Thermo­rec­eptors and Hypoth­alamus
Control Center
Preoptic area of hypoth­alamus
Effectors
Blood vessels, sweat glands, muscles.
 
Vasoco­nst­riction
→ heat retention.
 
Vasodi­lation
→ heat loss.

Defini­tions

Afferent Signal
Sends the inform­ation from the sensor to the control center / integrator (sometimes it is not needed if the sensor and control center are the same cell)
Efferent Signal
Used to send inform­ation from the control center to the effectors (cells­/or­gans) that need to perform an action to help restore homeos­tasis
Dynamic Equili­brium
The state of constant adjustment to maintain homeos­tasis, acknow­ledging that internal conditions fluctuate within a normal range.