Week 10 Flashcards
Define homeostasis
Maintenance of a relatively static or constant conditions in the internal environment
Why is communication critical in Homeostasis
- coordinated body activity requires integration of many systems
- transmission of information between cells
List the homeostatic control systems
- cardiovascular
- respiratory
- reproductive
- gastrointestinal
- renal, urinary
- endocrine
- neurophysiology
Control system’s components
- Some way to measure the regulated variable
- Some way to alter (effect) the regulated variable
- Something linking the two
Feedback loop
- Stimulus
- Receptor
- Afferent pathway
- Integrating centre
- Efferent pathway
- Effector
- Response
- Feedback
Control Concepts
- Negative feedback
- most common
- 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”
Feed-Forward control
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)
Neural communication
- long distance
- really, really fast
- target cells = very specific (synapse), nerve, muscle and gland
Endocrine Communication
- 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
Differences between Nervous and Endocrine systems
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)
Similarities between Nervous and Endocrine systems
• 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
Neuroendocrine Communicaiton
- combines neural & endocrine signalling
- neuron secretes hormones into blood
- adrenal medulla (adrenaline) & posterior pituitary (ADH, oxytocin)
Thermoregulation
- Low body temperature
- Thermoreceptors (skin and brain)
- Sensory neurons
- Brain
- Motor neurons (ANS and Somatic)
- Blood vessels, skeletal muscles, glands
- Increase body temperature
- Negative feedback
Plasma Glucose control
- Elevated blood glucose
- β cells in pancreas
- β cells in pancreas
- Pancreases secretes insulin
- Transport in blood
- Liver, muscle, etc. Open up glucose channels
- Reduced blood glucose
- Negative feedback (low blood glucose)
