Cell membrane I
I. Physiological Control Systems
The primary objective of physiological control systems is the maintenance of homeostasis.
These systems are categorized based on their scope and complexity.
A. Local vs. Reflex Control
● Local Control: This response is restricted to a small, specific region of the body and
does not require widespread systemic communication.
● Reflex Control: This involves systemic responses that are widespread throughout
the body. Reflex pathways typically involve the nervous and/or endocrine systems
and consist of several components:
● Sensor: Detects the initial change or stimulus.
● Control Center (Integrator): Processes the incoming information.
● Target (Effector): Produces the final physiological response.
B. Feedback and Feedforward Mechanisms
● Negative Feedback: Functions to stabilize a system and maintain homeostasis (
back to normal value ).
● Positive Feedback: These loops are not homeostatic. Instead of returning a
variable to a setpoint, they reinforce a stimulus to drive the system further away from
the normal value. This creates an amplifying cycle that requires an external
intervention or event to cease ( away from actual stimulus).
● Example: During childbirth, cervical stretch stimulates oxytocin release,
which causes uterine contractions, further pushing the baby against the
cervix and increasing the stretch until delivery stops the cycle.
● Feedforward Control: This allows the body to anticipate a change and respond
before the major disturbance occurs.
● Example: Ventilation increases rapidly at the very beginning of exercise
because the body predicts the upcoming demand for oxygen and the
production of O2.
C. Biological Rhythms and Setpoints
Variables are regulated within a normal range around a setpoint, which is not a static number
and can vary based on genetics, time of day, or long-term environmental exposure, constant
exposure.
● Biorhythms: These are predictable, repeating patterns of change (e.g., body
temperature peaking in the late afternoon and reaching a nadir in the early morning).
They exist to create a anticipatory response.
● Circadian Rhythm: A specific biological rhythm with a cycle of approximately 24
hours. These rhythms allow for anticipatory physiological responses to predictable
environmental changes.
II. Cellular Compartmentation
The body is organized into various compartments that are separated by biological membranes.
, ● Anatomical Compartments: These include the cranial, thoracic (pleural and
pericardial sacs), and abdominopelvic (abdominal and pelvic) cavities.
● Functional Fluid Compartments:
● Extracellular Fluid (ECF): Fluid located outside the cells, including blood
plasma (fluid inside blood vessels) and interstitial fluid (surrounds most
cells).
● Intracellular Fluid (ICF): Fluid located inside the cells.
I. Physiological Control Systems
The primary objective of physiological control systems is the maintenance of homeostasis.
These systems are categorized based on their scope and complexity.
A. Local vs. Reflex Control
● Local Control: This response is restricted to a small, specific region of the body and
does not require widespread systemic communication.
● Reflex Control: This involves systemic responses that are widespread throughout
the body. Reflex pathways typically involve the nervous and/or endocrine systems
and consist of several components:
● Sensor: Detects the initial change or stimulus.
● Control Center (Integrator): Processes the incoming information.
● Target (Effector): Produces the final physiological response.
B. Feedback and Feedforward Mechanisms
● Negative Feedback: Functions to stabilize a system and maintain homeostasis (
back to normal value ).
● Positive Feedback: These loops are not homeostatic. Instead of returning a
variable to a setpoint, they reinforce a stimulus to drive the system further away from
the normal value. This creates an amplifying cycle that requires an external
intervention or event to cease ( away from actual stimulus).
● Example: During childbirth, cervical stretch stimulates oxytocin release,
which causes uterine contractions, further pushing the baby against the
cervix and increasing the stretch until delivery stops the cycle.
● Feedforward Control: This allows the body to anticipate a change and respond
before the major disturbance occurs.
● Example: Ventilation increases rapidly at the very beginning of exercise
because the body predicts the upcoming demand for oxygen and the
production of O2.
C. Biological Rhythms and Setpoints
Variables are regulated within a normal range around a setpoint, which is not a static number
and can vary based on genetics, time of day, or long-term environmental exposure, constant
exposure.
● Biorhythms: These are predictable, repeating patterns of change (e.g., body
temperature peaking in the late afternoon and reaching a nadir in the early morning).
They exist to create a anticipatory response.
● Circadian Rhythm: A specific biological rhythm with a cycle of approximately 24
hours. These rhythms allow for anticipatory physiological responses to predictable
environmental changes.
II. Cellular Compartmentation
The body is organized into various compartments that are separated by biological membranes.
, ● Anatomical Compartments: These include the cranial, thoracic (pleural and
pericardial sacs), and abdominopelvic (abdominal and pelvic) cavities.
● Functional Fluid Compartments:
● Extracellular Fluid (ECF): Fluid located outside the cells, including blood
plasma (fluid inside blood vessels) and interstitial fluid (surrounds most
cells).
● Intracellular Fluid (ICF): Fluid located inside the cells.
