Homeostasis Flashcards
HOMEOSTASIS
Existence of stable internal environment
Eg control : temperature, water content, co2, blood sugar and pressure
Homeostatic regulation means adjustment of physiological systems to preserve homeostasis.
Elements of homeostatic control system
Stimulus - produces change in body
Receptor - detects change
Input- information of change along sensory neurone to brain control centre
Control centre- Deals with the change
Output- information sent along efferent neurone with instructions for effector
Response- effector reduces effect of stimulus and homeostatic level returned to normal
Negative feedback
Most common homeostatic regulation
Maintains homeostatic levels in an optimal range rather than fixed value
Ranges vary in patients - influenced by gender, age, genetics, environment , nutrition and general health
95% people fit in accepted ranges and 5% do not
Positive feedback
Less common
Produces a change but enhancing its influence on the process which gives rise to it
Examples : oxytocin production in childbirth and haemostasis (platelets phase)
Haemostasis positive feedback
Break in vessel wall so positive feedback initiated
Platelets adhere to injury site
Release chemicals
Attracts more platelets
Platelet plug formed and cycle ends once blood clot seals off blood flow
Temperature control in negative feedback
Thalamus detects high or low temperatures of blood
If cold - heating mechanisms activated like shivering
If hot- cooling mechanisms like sweating and redistribution of blood
Eg-
stimulus is body is too hot
Receptors detect you are too hot
Information travels up afferent neurone to thalamus
Thalamus is control centre and deals with the high temp
Output then sent down efferent neurone to effectors
Effectors are blood vessels that redistribute blood flow and sweat gland to cool you down
Systems integrate
System integration
Body overheats
Sweat to reduce heat
Dehydration as fluid loss
Blood volume loss due to dehydration
The heart works harder and kidneys retain more fluid
Only notice this if an issue=
Heart failure patient does not want to sweat as it puts heart under strain
Kidney disease doesn’t want to sweat as can’t cope with retaining fluid
2 regulation mechanisms
AUTOREGULATION
intrinsic response is automatic response of cells, tissues and organs to adjust to environment changes
Eg, if decreased oxygen to an area, release of chemicals means blood vessels vasodilate there.
EXTRINSIC REGULATION
Nervous system or endocrine system making changes to enable pos / neg feedback
Nervous system and endocrine system
Fast and short lived
Crisis management
Eg, in exercise - NS messages to the heart to increase HR and to the blood vessels to redistribute blood to working muscles away from digestive system
Endocrine system is longer to react but longer lasting
Autonomic nervous system
Dynamic balance between sympathetic and parasympathetic systems
Sympathetic speeds things up- fight or flight
Parasympathetic slows- rest and digest
Damage to homeostasis
Injury, infection and genetic abnormalities cause homeostatic issues
Injury and infection are temporary
Genetic is long term
Haemophilia
Genetic
Some clotting factors are not produced .
Positive feedback of haemostasis interfered
Bleed profusely in injury and clotting does not happen
Huge swellings with blood pooling
Treatment : missing clotting factor through injections or tablets
Vulnerable
Newborn babies
Immaturity of systems means vulnerable to altered homeostasis
- immature immune system
- renal function poor
Endocrine system
Thermoregulation
Prone to infections and can’t produce antibodies
Up to 6-9 months, they cannot thermoregulate - can’t shiver or sweat , as muscle bulk too low and sweat glands not formed
If temperature too high = febrile convulsions
Elderly:
More degeneration than regeneration
Produce less hormones / less responsive to hormones
Decreased heart and circulation efficiency
Loss of neurones and transmitters
Blood PH
Blood PH is homeostatic control
In exercise , produce more co2 which is removed from body
Somebody with COPD has more c02 as gas exchange doesn’t happen and exercise makes co2 even higher
So homeostasis tells them to breathe harder to remove co2, lung tissue is damaged and cannot do that
Homeostasis basis
Norm altered Detected by receptors (either excessive or deficient) so would want to increase or decrease Control centre Effector response Norm restored
