Body fluids, feedback mechanisms LO6, LO7

Question 1

Homeostasis

Answer 1

For cells to function properly, the conditions in the internal environment need to be carefully controlled
–> Homeostasis is a dynamic stable state = internal conditions can vary but they remain within narrow limits

Question 2

Conditions to keep in specific range

Answer 2

• temp
• pH
• waste production
• electrolyte concentration
• nutrient levels

Question 3

Variable outside homeostasis

Answer 3

A change in a variable outside the normal limits act as a
stimulus which causes an appropriate corrective response
1. stimulus, receptor (afferent pathway), control centre, (efferent pathway), effector, response

Question 4

Communication systems

Answer 4

Nervous System
- rapid
- electrical
short lived
- limited target range
has nerve reflex
Endocrine System
- Slow acting
- Chemical
- long lived
- wide target range

Question 5

Negative feedback

Answer 5

• A variable moves outside,
  of the pre-set, normal range and becomes a stimulus and stimulates a response
• the response reduces the effect of the stimulus and
  returns the variable to within the normal range
• response turns off

Question 6

Positive feedback

Answer 6

• the response enhances the effect of a stimulus,
  keeping the variable outside the normal range
• the response does not turn off but is continued or
  enhanced until the process is completed
  eg: childbirth, blood clotting

Question 7

Why two types of feedback?

Answer 7

Negative feedback - Provides stability and long-term control over internal conditions, Maintains the narrow range of body conditions required for optimal cell function
Positive feedback - Accelerates a process to completion, Occurs when a potentially dangerous situation or stressful process must be resolved/completed quickly