Homeostasis Flashcards
Homeostasis
The tendency of the body to seek/maintain a condition of balance/equilibrium within its internal environment, even when faced with external changes
What 3 Systems Does it Effect?
Nervous System - vasodilation, vasoconstriction, shivering, sweating Endocrine - adrenaline, cortisol, thyroxine Behavioural - clothes change
What Happens when Fluids are too High?
- Osmoreceptors send signal to hypothalamus
- Hypothalamus tells pituitary gland to release less ADH
- Less ADH means kidney (effector) so less urine output
Baroreceptor
sensory neurones detecting pressure changes found in the blood vessels
Definition of Blood Pressure
The Force exerted as it presses against the walls of the blood vessels
Oncotic Pressure
the pulling force which draws fluid into the capillaries from surrounding tissue
Hydrostatic Pressure
the pushing force exerted on the walls of the capillaries out onto the surrounding tissue
Negative Feedback System
- Change detected by specialised receptors
- Receptor informs control centre
- Control centre sends signal to effector
- Effector Initiates response
- Response reinstates normal physiological range
Positive Feedback System
body continues to move away from optimum range, less common. Eg. Hormone production in birth
Temperature Regulation
- Thermoreceptors in skin, aorta, arteries detect change
- Signal sent to hypothalamus (control centre) in brain
- Hypothalamus sends signal to effectors
- Effector informs control centre when to stop
What Causes Temperature Change?
Conduction ie lying on cold concrete, convection ie jumping into sea, metabolic changes, environment
What Happens if Blood Sugar is too High?
beta cells detect ‘hyperglycaemia’ so pancreas releases insulin
What Happens if Blood Sugar is too Low?
Alpha cells detect ‘hypoglycaemia’ so pancreas releases glucagon
How Does Insulin and Glucagon Raise/Lower Blood Sugar Lvl’s?
Insulin converts glucose -> glycogen stored in the liver Glucagon is broken down to glucose for blood to cells
Hypoglycaemic Event
Blood Sugar >4mmol/L. Assess LOC. Glucogel = 40%. Glucose = 10%. IV, Glucagon1M, when alert make them eat carbs
Hyperglycaemic Event
IV Fluids to dilute conc. DKA/HONK fluids, rapid transfer
Blood Pressure Negative Feedback
- Baroreceptors detect change in blood pressure
- Send impulse to medulla oblongata (control centre)
- Medulla oblongata sends correct signal to effectors
How the Endocrine System Works as an Effector in BP?
Epinephrine is released which increases heart rate & contractility causing vasoconstriction, increasing BP OR ADH released stimulating H2O retention, so blood is less diluted, so BP is increased
The Renin-Angiotensin-Aldosterone System (R.A.A.S)
- Liver regurlary secretes a pre-enzyme Angiotensinogen into the blood
- In response to lowered blood pressure, the juxtaglomerular cells in the Kidney secrete the ‘Renin’ enzyme
- Renin converts Angiotensinogen -> Angiotnesin 1 before being converted to Angiotensin 2 by Angiotensis Converting Enzyme (ACE) as it passes through the lungs
- Angiotensin 2 actis upon the adrenal gland, to release Aldosterone (steroid hormone) which reduces H2O retention
- Angiotensin 2 also does vasoconstriction, reducing vol of blood to kidney, so reducing the potential to excrete H2O
Difference between intracellular/extracellular fluid
intracellular fluid is found within cells and extracellular is found outside of cells in various places throughout the body
5 Places where extracellular fluid is found
ECF - Fluid outside cells
ECF in Blood- plasma
ECF in lymph vessels - lymph
ECF in spinal/brain - CSF cerebrospinal fluid
ECF in eye - aqueous humour
What Effects Fluid Composition?
Composition changes when going into/out cells eg drops of glucose and picks up waste products Exercise, temp, electrolyte conc
Osmoregulation Negative Feedback System
- Osmoreceptors detect change, sends signal to hypothalamus
- Hypothalamus tells pituitary gland to release more ADH
- Effectors secrete ADH, makes kidney retain H2O, lowering urine output
- Hypothalamus also triggers ‘thirst’ signal
