Week 10

Question 1

Define homeostasis

Answer 1

Maintenance of a relatively static or constant conditions in the internal environment

Question 2

Why is communication critical in Homeostasis

Answer 2

• coordinated body activity requires integration of many systems
• transmission of information between cells

Question 3

List the homeostatic control systems

Answer 3

• cardiovascular
• respiratory
• reproductive
• gastrointestinal
• renal, urinary
• endocrine
• neurophysiology

Question 4

Control system’s components

Answer 4

1. Some way to measure the regulated variable
2. Some way to alter (effect) the regulated variable
3. Something linking the two

Question 5

Feedback loop

Answer 5

1. Stimulus
2. Receptor
3. Afferent pathway
4. Integrating centre
5. Efferent pathway
6. Effector
7. Response
8. Feedback

Question 6

Control Concepts

Answer 6

1. Negative feedback
   
   • most common
2. Positive feedback
   
   • Rare - non-homeostatic (increases the instability)
   • blood clotting, action potentials (both part of -ve feedback systems), childbirth

• require an “error signal”
• system always playing “catch-up”

Question 7

Feed-Forward control

Answer 7

An “anticipatory” alteration of effectors - independent of feedback
- Parametric feed-forward (adaptive control)
- System ‘learns’ (adapts from previous failures)
- eg – ballistic control, ball throwing

• Predictive homeostasis (anticipatory control)
  - eg - Increasing cardiorespiratory function in anticipation of exertion
• Postural responses are triggered centrally before voluntary movements
• Exercise increases ventilation (Even though VA is controlled by PaCO2 negative feedback)

Question 8

Neural communication

Answer 8

• long distance
• really, really fast
• target cells = very specific (synapse), nerve, muscle and gland

Question 9

Endocrine Communication

Answer 9

• long distances - transport via bloodstream
• hormones secreted by glands
• target organs or cells - cells that have receptors for a hormone and can respond to it

Question 10

Differences between Nervous and Endocrine systems

Answer 10

Nervous system:
- SPEED + PERSISTENCE: fast (ms), stops just as fast
- ADAPTATION: adapts quickly (response declines)
- TARGET AREA: very specific (one organ)

Endocrine system:
- SPEED + PERSISTENCE: slow (s to days), continues
- ADAPTATION: persistent (adapts slowly)
- TARGET AREA: wide spread (many organ)

Question 11

Similarities between Nervous and Endocrine systems

Answer 11

• Several chemicals function as hormones and neurotransmitters
- Noradrenaline,dopamine,andantidiuretichormone(ADH)
• Both systems can have similar effects on target cells
- Noradrenalin and glucagon both cause glycogen hydrolysis in liver
• The two systems can regulate each other
- Neurotransmitters can affect glands, and hormones can affect neurons

Question 12

Neuroendocrine Communicaiton

Answer 12

• combines neural & endocrine signalling
• neuron secretes hormones into blood
• adrenal medulla (adrenaline) & posterior pituitary (ADH, oxytocin)

Question 13

Thermoregulation

Answer 13

1. Low body temperature
2. Thermoreceptors (skin and brain)
3. Sensory neurons
4. Brain
5. Motor neurons (ANS and Somatic)
6. Blood vessels, skeletal muscles, glands
7. Increase body temperature
8. Negative feedback

Question 14

Plasma Glucose control

Answer 14

1. Elevated blood glucose
2. β cells in pancreas
3. β cells in pancreas
4. Pancreases secretes insulin
5. Transport in blood
6. Liver, muscle, etc. Open up glucose channels
7. Reduced blood glucose
8. Negative feedback (low blood glucose)