Homestasis

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  • Created by: syaqub18
  • Created on: 12-05-15 13:44
What is the autonomic system divided in to?
Sympathetic and parasympathetic
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What is the role of the sympathetic nervous system?
“fight or flight” system gets body ready for action
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What is the role of the parasympathetic nervous system?
“rest and digest” calms the body down
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What receptors detect pressure change?
Baroreceptors
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Where are baroreceptors located?
In the aorta, vena cava and carotid arteries
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What receptors detect chemical change?
Chemoreceptors
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Where are chemoreceptors located?
Aorta, carotid arteries and medulla
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What controls heart rate?
Medulla
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What happens when blood pressure is too high?
Baroreceptors detect pressure change, send impulses along sensory neurone to medulla which sends impulses along parasympathetic neurones, secrete Ach which bind to receptors on SAN, heart slows down
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What happens when blood pressure is too low?
Baroreceptors detect pressure change, send impulses along sensory neurone to medulla which sends impulses along sympathetic neurones, secrete noradrenaline which bind to receptors on SAN, heart speeds up
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What happens when blood pH levels are high (high O2, low CO2)?
Chemoreceptors detect change, send impulses along sensory neurone to medulla which sends impulses along parasympathetic neurones, secrete Ach which bind to receptors on SAN, heart slows down
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What happens when blood pH levels are low (low O2, high CO2)?
Chemoreceptors detect change, send impulses along sensory neurone to medulla which sends impulses along sympathetic neurones, and secrete noradrenaline which bind to receptors on SAN, heart speeds up
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What is negative feedback?
Mechanism which returns the level back to normal
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What is the pathway of negative feedback?
Normal level---levels change---receptors detect change---communication via hormones or neurones---effectors respond---normal level
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What happens in extreme changes e.g. huge drop in body temperature?
Negative feedback mechanism may not be able to counteract change
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What is the purpose of having multiple negative feedback mechanisms?
To quicken response and give body more control
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What is positive feedback?
The mechanism which amplifies change away from the normal level
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What is the pathway of positive feedback?
Normal level---levels change---receptors detect change---communication via hormones or neurones---effectors respond---normal level changes (this loop continues)
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Why isn’t positive feedback involved in homeostasis?
Because it doesn’t keep internal environments constant
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How do ectotherms control body temperature?
They change their behaviour as they can’t change their body temperature internally
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What does the activity of ectotherms depends on?
They change their behaviour as they can’t change their body temperature internally
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How do endotherms control body temperature?
By homeostasis and by altering behaviour
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How do endotherms lose heat?
Sweat- evaporates and takes heat from body, Hairs lie flat- don’t trap insulating layer of air, Vasodilation- arterioles near skin dilate and are closer to skin surface heat lost by radiation
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How do endotherms produce heat?
Shivering- muscles contract in spasms, heat produced from increased respiration, Hormones- increase in adrenaline which increases metabolism
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How do endotherms conserve heat?
Less sweat, hairs stand up to trap insulting air, vasoconstriction
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What is the hypothalamus?
Part of brain which controls temperature
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What detects temperature change?
Thermoreceptors
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How are the blood glucose levels maintained by?
The pancreas
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Which system controls the blood glucose?
Hormonal system
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Which hormones control blood glucose?
Insulin and glucagon
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Where are the clusters of cells in the pancreas called?
The islets of Langerhans
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Where is insulin secreted from?
Beta cells
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Where is glucagon secreted from?
Alpha cells
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What happens in high blood glucose?
Insulin secreted from beta cells, it binds to receptors on cell membrane of liver and muscle cells, increases permeability to glucose so cells take it up, also activates enzymes which turn glucose in to glycogen by glycogenesis
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What happens in low blood glucose?
Glucagon secreted by alpha cells, binds to receptors on cell membrane of liver and muscle cells, activates enzymes that break down glycogen to glucose by glycogenolysis, promotes formation of glucose from glycerol/amino acids, decreases respiration
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What is adrenaline?
Hormone secreted from adrenal gland
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What does adrenaline do?
Increases glucose concentration by activating glycogenolysis, inhibits glycogenesis, activates glucagon secretion and prevents insulin secretion
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What is the second messenger model?
Binding of the hormone to cell receptors which activates and enzyme inside cell membrane, which produces chemical knowns as second messenger, this activates other enzymes in cell to bring about response
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How does the second messenger model work to activate glycogenolysis?
Adenraline and glucagon bind to receptors on cell membrane, causes adenylate cyclase to be activated in cell, this converts ATP to cyclic cAMP which is the second messenger, this causes chain reaction and promotes glycogenolysis
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What is the cause of type 1 diabetes?
When the beta cells in islets of Langerhans don’t produce any insulin
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What is the cause of type 2 diabetes?
When the beta cells in islets of Langerhans don’t produce enough insulin
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What is FSH (follicle stimulating hormone)?
Stimulates follicle to develop
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What is LH (Luteinising hormone)?
Stimulates ovulation and corpus luteum to develop
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What is oestrogen?
Stimulates uterus thickening
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What is progesterone?
Maintains the thick uterus lining ready for implantation of embryo
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Where are LH and FSH secreted from?
Anterior pituitary gland
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Where are oestrogen and progesterone secreted from?
Ovaries
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What are the stages of the menstruation cycle?
1.) High FSH concentration 2.) oestrogen concentration peaks and LH surges 3.) progesterone concentration rises
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What happens in stage one High FSH concentration?
High FSH concentration stimulates follicle development, follicle releases oestrogen, causes oestrogen to rise which causes uterus lining to thicken, Oestrogen rise inhibits FSH by negative feedback, prevent follicle development
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What happens in stage two oestrogen concentration peaks and LH surges?
Oestrogen concentration increase, when at a certain level it doesn’t inhibit FSH, it stimulates LH and FSH, Increase of LH increases release of Oestrogen this repeats and follicle ruptures, this is done by positive feedback
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What happens in stage three progesterone concentration rises?
Corpus luteum releases progesterone, progesterone inhibits LH and FSH, uterus lining maintained by progesterone, negative feedback makes sure no follicles develop
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Other cards in this set

Card 2

Front

What is the role of the sympathetic nervous system?

Back

“fight or flight” system gets body ready for action

Card 3

Front

What is the role of the parasympathetic nervous system?

Back

Preview of the front of card 3

Card 4

Front

What receptors detect pressure change?

Back

Preview of the front of card 4

Card 5

Front

Where are baroreceptors located?

Back

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