Communication and Homeostasis - Module 5 Flashcards
cell signalling
the release of a chemical by one cell that is detected by another using a receptor
The 2nd cell carries out a response
This occours in the endocrine and nervous system
define Homeostasis
the maintenance of a constant internal environment
What has to be maintained theough homeostasis
-Body temp
-Blood glucose conc.
-Blood salt conc.
-Water potential of blood
-Blood pressure
-Carbon dioxide concentration
What in their environment to animals respond to
external + internal stimuli
E.g: Temp, glucose
What in their environment to plants respond to
external + internal stimuli
E.g: light intensity
stimuli =
internal + external changes in an environment
Receptors
-Detect stimuli
-specific to one particular stimulus
-Can be cells e.g: photoreceptors connected to nervous system or can be proteins on cells surface membranes
Effectors
Cells that bring about a response to a stimulus. Include muscles cells and cells found in glands
Negative feedback=
keeps things around normal level
a system reacts to a change in a way that pushes it back to its stable state
Process of negative feedback [mechanism]
-Receptors detect when a level (e.g glucose or temperature) is too high / low.
-This information is communicated by the nervous system or the hormonal system to effectors.
-The effecters respond to counteract the change, bringing the level down to normal
Positive feedback mechanism=
they react to a change in a way which amplifies it from a stable state
proces of positive feedback mechanism
-Receptors detect the change and the effectors respond by further increasing the level away from the normal level
is positive feedback involved in homeostasis
no as it doesn’t keep he internal environment at a constant
It is useful to rapidly activate bodily processes
2 examples of positive feedback and their basic description
1)Blood clotting- during formation of blood clot, platelets become active and release a chemical that triggers more platelets to be released
2) During childbirth - when head of baby presses against cervix, release of oxycotin is stimulated. Oxycotin stimulates uterus to contract, pushing the head of the baby harder towards the cervix, .: more oxycotin is released
what is an Ectotherm
Animals that can’t control their body temperature internally.
This means their body temperature depends on their surroundings.
They control their temperature by changing their behaviour
What is an Endotherm?
Animals that can control their body temperature internally by homeostasis
example of an endotherm
Mammals and birds
example of ecotherm
invertebrate, fish, reptiles, amphibians
Name 3 behavioural ways ecotherms warm up
Bask in sun
Conduction
exothermic metabolic activity
How do ecotherms bask in the sun
-orientate body so that max SA exposed to sun
Also extend areas of body- to absorb more radiation from the sun
eg: liards bask in sun long enough to be fast enough to catch prey
locusts spread wings
How do ecotherms use Conduction to warm up
Press body against warm ground
Example of ecotherm using exothermic metabolic activity to warm up
Galapagos Iguanas contract muscles to vibrate, increasing cellular metabolism
name 2 physiological ways ectotherms regulate temperature
-alter skin colour
-alter heart rate
advantages of being an ectotherm
Don’t need to use as much energy on regulating body temperature, so don’t ae to eat as much and can use energy for growth
Disadvantages of being an ectotherm
May be not capable of activity in winter so need to hibernate
How to Ectotherms cool down (behavioural)
-Shaellter from sun, sometimes using mud or water
-press body agains cold stones
-minimise SA to sun
-Minimise body movement
name 5 ways in which endotherms Cool down (physiologically)
-vasodilation
-Increased sweating
-large SA:V ratio
-Pilorelaxation (hair relax)
-Animals panting
name 5 ways in which endotherms Warm up (physiologically)
-vasoconstriction
-piloerection ( traps insulating layer of air)
-Shivering
-Raising feathers
- Release hormones such as adrenaline, require homeostatic system receptors to detect change
Bhehavioural responses to a change in temperature for endotherms
-Wear clothes
-live in house
disadvantage and a advantage of being an endotherm
(-) need more food
(+) Can survive without shelter
Endocrine Gland
gland that secretes hormones directly into the blood
Exocrine Gland
Gland that secretes substances into a duct which carries the molecule to where it is needed
Pathway of hormonal control
Stimulus - Receptors - Hormone - Effectors - Response
Different types of hormones
-Protein + peptide hormones (non-steroid)
-Steroid hormones
Steroid hormones
properties, examples,
-Lipid soluble
-Can pass through membrane into cells and act directly on the DNA
-Testosterone, oestrogen, Progesterone
Protein + peptide hormones (non-steroid)
properties, examples
-Derivatives of amino acids
-Not soluble so do not enter cell
-Adrenaline, insulin, glucagon, HGH, FSH, LH
Process of thermoregulation after a rise in core body temperature caused by external temperature or exercise
-This is detected by the thermoregulatory centre in the hypothalamus and the peripheral temperature receptors in the skin
-Hypothalamus sends impulses to effectors which respond by causing Vasodilation of arterioles , sweating or panting,
-Core body temperature returns to normal
what is a hormone
Molecule released by endocrine gland into the blood. Act as chemical messengers sending signals to a target/tissue cell
when is Adrenaline released and where from
-Secreted from Adrenal gland when theres a low concentration of glucose in the blood, when you’re stressed or when you’re exercising
how does Adrenaline cause a Response in Target tissue?
-Adrenaline = 1st messenger
-binds to specific receptors in cell membrane of many cells
-when adrenaline binds, it activates an enzyme in the membrane called adenylyl cyclase.
-Activated adenylyl cyclase catalyses production of secondary messenger = cyclic AMP (cAMP) from ATP
-cAMP activates a cascade of enzyme reactions
what does the cortex of the adrenal gland do
uses cholesterol to make steroid hormones =
-mineralocorticoids (ALDOSTERONE) control sodium + potassium in blood
-Glucocorticoids (CORTISOL) help control the metabolism of proteins + carbohydrates in the liver
What does the Adrenal medulla do
secretes Catecholamine hormones (modified amino acids) E.g: noradrenaline and adrenaline
Effects of Adrenaline and Noradrenaline
Make energy available in the short term:
-Increase heart rate + stroke volume
-general vasoconstriction to raise blood pressure
-dilation of pupils
-increased mental awareness
-inhibits gut action
-body hair stands on end
-relaxes smooth muscle in bronchioles
-Cause cells to break down glucagon into glucose
-constricts some blood vessels so that blood is diverted to the brain and muscles
\effects of cortisol and aldosterone
-Stimulates breakdown of fats and proteins into glucose
= increased energy available so brain and muscles can respond to situation
- Increased blood volume and pressure by increased uptake op sodium ions and water into kidney
-Supress immune system
What type of gland is the pancreas
acts as both an endocrine and exocrine gland
when does the pancreas act as an endocrine gland?
in the regulation of blood glucose concentration, makes insulin and glucagon and releases them into the bloodstream
when does the pancreas act as an exocrine gland?
in digestive system,
produces enzymes and releases them into the small intestines via a duct
Islets of Langerhans
areas of the pancreas that contains endocrine tissue. Found in clusters around blood capillaries -> secretes hormones directly into blood
properties of alpha cells and their role
-Secrete GlucAgon
-Larger and more numerous than Beta cells
what di Beta cells secrete
Insulin
what are the normal blood glucose levels
- 90mg 100cm^-3
- 4-6 mmol dm^-3
how do alpha and beta cells react to a rise in blood glucose concentration above the normal value
Beta cells detect this
-alpha cells stop secreting glucagon and the beta cells secrete insulin into the blood plasma
After insulin is secreted into the blood plasma, what does it bind to?
complementary receptors on the plasma membrane of hepatocytes and muscle cells
after insulin binds to receptors on cells , what happens
This activates adenylyl cyclase enzyme, causing ATP to be converted into cAMP, the second messenger.
This causes a series of enzyme controlled reactions to start taking place inside the cell
What enzyme controlled reactions to start taking place inside the cell due to Insulin ?
-higher uptake of glucose by the cells,
Due to glucose Channel proteins being inserted into the membrane
-glycogenesis (formation of glycogen)
-More glucose converted to fats
-more glucose used in respiration
how do beta and alpha cells react to a fall in blood glucose concentration below the normal value
-alpha cells start secreting glucagon
-beta cells stop secreting insulin into the blood plasma
After being secreted into the blood, what does Glucagon do?
binds to complementary receptors on plasma membrane of hepatocytes
after glucagon binds to receptors, what happens
Liver cells respond by activating :
-Gluconeogenesis (formation of glucose from fatty acids or amino acids)
-Glycogenolysis (Breakdown of glycogen into glucose)
-less respiration of glucose
name for diabetes
diabetes Mellitus
what does Type 1 diabetes cause
-unable to produce insulin
-B cells in the Islets of Langerhans do not produce insulin
what does type 2 diabetes cause
-Cannot effectively use insulin
either because:
-B cells don’t produce enough Insulin
-person’s body cells don’t respond properly to Insulin
when is type 1 diabetes usually developed, why
in childhood
possibly due to autoimmune response where white blood cells attack Beta cells
possibly a genetic link
Treatment of type one diabetes
-regular insulin injections
-test blood glucose levels (hyperglycemia = high blood sugar vs hypo)
-
where did and now where do we get insulin to treat diabetes
-From pigs and cows
-Now from GM bacteria
Cures for type 1 diabetes [Potential]
-pancreas transplant
-Injected totipotent stem cells, stimulated to create B cells
Explain why person with Diabetes type 2 not responding to Insulin
-usually glycoprotein insulin receptor on cell membrane not working properly
=Cells lose responsiveness to Insulin so glucose stays in bloodstream
Treatment for Diabetes type 2
-monitor diet, regulate carb and glucose levels
-Monitor exercise levels
If these don’t work:
-Metformin = usually first medicine to be perscribed,
-sulfonylureas
-Thiazolidinediones
what do the blood insulin and blood glucose levels of a diabetic person look like ?
B Insulin = very low
B glucose = very High
anticoagulant
medicines that help prevent blood clots.
