Ch #3: Internal Environment & Control Systems

Homeostasis

Maintenance of a relatively constant and "normal" internal environment at rest

Steady state

A constant/unchanging internal environment during stress/exercise, but not necessarily "normal" (balance between demands and the body's response)

Negative feedback (+example)

Response reverses or opposes the initial disturbance in homeostasis (most common control system mechanism)

Positive feedback (+example)

Response increases or reinforces the original stimulus (e.g., oxytocin during childbirth)

Adaptation

Change in the structure or function of a cell or organ system that results in an improved ability to maintain homeostasis (e.g., increased mitochondria from aerobic exercise)

Acclimation

Adaptation to environmental stressors (heat, cold, altitude), NOT exercise-based (e.g., heat stress adaptation in hot environments)

What is the average "normal" body temp at rest

~98.6°F or 37°C

How does arterial blood pressure behave around a set point

DYNAMIC constancy-oscillates (fluctuates) slightly above and below a set point

Goal of a biological control system

To regulate physiological variables at or near a constant value

Maintenance of stored nutrients, energy production, and protein breakdown & synthesis are all examples of what?

Intracellular control systems

3 interconnected components of a biological control system

1) Sensor/receptor, 2) Control center, 3) Effector

Sensor / Receptor (function)

Detects changes in the physiological variable

Control center (function)

Assesses incoming input and initiates an appropriate response

Effector (function)

Changes the internal environment back toward normal (corrects the disturbance)

Negative feedback vs. Positive feedback (key difference)

Negative feedback returns system toward set point by reversing stimulus; Positive feedback amplifies/increases the original stimulus

Pancreas's dual role in blood glucose regulation

Acts as BOTH the sensor (detects high/low glucose) and the effector (releases insulin/glucagon) without brain/CNS involvement

Failure of any component of a biological control system

Results in a disturbance of homeostasis (leads to disease/pathology)

Type 1 Diabetes (control system component failure)

Failure of the EFFECTOR (destruction of pancreatic beta cells prevents insulin release, resulting in hyperglycemia)

Under what conditions are control systems capable of maintaining steady state?

Submaximal exercise/effort (

What factors cause an inability to maintain steady state?

High exercise intensity, prolonged duration, and/or hot/humid environments

Intracrine signaling (Definition & Example)

Chemical messenger is produced inside the cell and triggers a signaling pathway within that same cell without leaving (e.g., muscle cell adaptation signals)

Juxtacrine signaling (Definition & Example)

Chemical messenger is passed directly between two connected, adjacent cells via gap junctions (e.g., cardiac muscle cells coordinating contractions)

Autocrine signaling (Definition & Example)

Chemical messenger is released into extracellular fluid and acts on the external surface of that same cell (e.g., muscle cell releasing IGF-1 during resistance training to promote its own growth)

Paracrine signaling (Definition & Example)

Chemical messenger is released to act locally on nearby target cells (e.g., immune cells coordinating local inflammation or vascular endothelial cells releasing nitric oxide to dilate nearby vascular smooth muscle)

Endocrine signaling (Definition & Example)

Chemical messengers (hormones) are released directly into the bloodstream to travel to target cells in remote tissues with specific receptors (e.g., insulin released by pancreas to target muscle/adipose tissue)

Name the 5 types of cell signaling

Intracrine, Juxtacrine, Autocrine, Paracrine, Endocrine