homeostasis Flashcards
what is homeostasis?
The relative constancy of the body
The maintenance of constant conditions in the body’s environment
What is compensation?
the return to homeostasis after being challenged
what is decompensation?
the failure to compensate, adapt, heal etc
How does the body respond to a change/imbalance?
1 Stimulus produces change in variable
- Change detected by receptor
- Input information sent along afferent pathway to control centre
- Output information sent along efferent pathway to effector
- Response of effector feeds back to influence magnitude of stimulus and returns variable to homeostasis
Is the autonomic nervous system voluntary or involuntary?
involuntary
What does the autonomic nervous system collaborate with?
endocrine system
List some functions of the autonomic nervous system
Innervates smooth muscle, cardiac muscle and glands
Two nerve fibres, connected by a synapse
Stimulates or inhibits a target cell
Regulates the internal environment
What is negative feedback?
- Change ininternal environment
- Detected by sensory cell
- Sensory nerve fiber → Central nervous system
- Comparison - what should it be
- Altered impulse frequency
- Motor nerve fiber (peripheral nervous system) →Effector
- Changed internal environment - back to normal
What is positive feedback?
e.g. oxytocin during child birth - increases away from normal, change increases change
examples of negative feedback
- temperature control
- water balance
- ph of blood
How does homeostasis relate to tissues and cells?
Homeostatic mechanisms are responsible for maintaining optimal tissue function and cellular turnover
What signals dermal blood vessels to dilate, and sweat glands to secrete, when body temperature rises above normal?
autonomic nervous system
What does body detect to regulate water in the body?
Osmolarity of plasma and interstitial fluid
What are the receptors called which detect plasma osmolarity?
Osmoreceptors (in hypothalamus)
Where are osmoreceptors?
hypothalamus
Describe what happens in homeostasis when an animal is dehydrated
- Stimulus disrupts osmo homeostasis
e.g sweating
- Osmolarity of plasma and interstitial fluid increased
- Detected by osmoreceptors of hypothalamus
- Nerve impulses to hypothalamus and posterior pituitary glands, releases more ADH
- ADH increases permeability to water of cells in distal convoluted tubule and collecting duct
- More water reabsorbed into blood
- Decreases plasma osmolarity
- Return to homeostasis when plasma osmolarity decreases to normal
How is homeostasis achieved when calcium levels in the blood are too high?
Thyroid gland releases calcitonin
Increases Ca deposition in bones
Decreases uptake in kidneys
How is homeostasis achieved when calcium levels in the blood are too low?
Parathyroid glands release parathyroid hormone
Increases Ca uptake in intestines - more Ca channels in gut lumen
Increases Ca uptake in kidney
Stimulates Ca release from bones
what are the 2 types of cell death?
- necrosis
- apoptosis
What is apoptosis?
Programmed cell death
What is necrosis?
Cell death in response to injury/illness
What does a cell undergoing necrosis look like?
swells
Is necrosis reversible?
yes, but it comes to a point where it then become irreversible
What happens to necrotic cell contents?
Once cell disintegrates, enzymes digest contents
