Paper 2B Part 1 Flashcards
What is the general outline for how bodies respond to change?
Stimulus receptor central nervous system (brain or spinal cord) effector (muscle for nervous response, gland for hormonal response) response
What two types of response can our bodies have?
hormonal and nervous
Define stimulus
Detectable change in the internal or external environment
Define receptors
Any structure able to respond to a change
Define co-ordinator (CNS)
The ‘switchboard’ connecting information from the receptor to the appropriate effector
Define effector
Causes a response (muscle or gland)
Define response
The output/change in behaviour
With heat on the hand as the stimulus, what happens in the rest of the system?
Heat on hand nerves on hand detect heat message sent to CNS message sent to muscles in arm move hand
Organisms react to stimuli in their environment in different ways, what are the main diffrences?
• The whole organism or only part of it could move in response• The movement could be directional or non-directional
What does an organisms reaction to its environment enable it to do?
to be better adapted to its environment
What are the types of response?
Kinesis, taxes, and trophisms
What is kinesis / kinetic response?
• Whole organisms• Alteration in the rate of movement• In response to a change in the intensity of a stimulus• Non-directional (not determined by the stimulus)
What is taxes / Tactic Response?
• Movement of the entire organism or cell• In response to and directed by the stimulus• Phototaxis = light, Chemotaxis = chemical• Positive taxis (towards + ) or negative taxis (away from - )
What is tropisms / trophic response?
• Movement of part of a plant• Directed by the stimulus• Geotropism, phototropism, hydrotropism• Growth response
Which responses affect the whole organsim?
tactic and kinetic
Which responses affect part of an organism?
tropic
Describe the processes involved in the transport of sugars in plant stems (5 marks)
At the source, sucrose is actively transported into the phloem via the companion cells. This lowers the water potential in the phloem and water enters by osmosis. This produces a high hydrostatic pressure, causing a mass flow towards roots. At roots, sugars are removed and used in respiration.
What Plant Responses are there?
- Phototropism: response to light2. Hydrotropism: response to water3. Geotropism: response to gravity
Where is IAA produced?
.IAA produced at the apical meristem, at the top of the plant
.Plants do not have a nervous system therefore they use what?
specific growth factors (auxins)
plant growth factors are more descriptive, why?
- Affect growth- Are made by cells located throughout the plant (not organs)- Produced in small quantities- Affect tissues close by and sometimes tissues they released from
What is the main growth factor in plants?
.The hormone indoleacetic acid (IAA) – growth factor causing cell elongation
What is scientific research?
- Observe and try to explain it using prior knowledge2. Formulate a hypothesis that can be tested experimentally
Darwin’s Evidence for Tropisms: obersvation, hypothesis, and experiment
- Observation: Grasses grown always tilted towards the window2. Hypothesis: Light (stimuli) is detected by the tip of the shoot, leads to tilting response3. Experiment: 5 plants in different conditions, one normal, one with the tip removed, one with the tip covered by an opaque cap, one with the tip covered by a transparent cap, one with base covered by opaque shield, light faced them all in same direction. Only the normal, tip covered by transparent cap and base covered by opaque shield plants bent towards the light. Also the control plant showed smaller cells on the illuminated side and longer ones on the shaded side. This suggested that light affected the tip, causing it to bend towards the light by growing the shaded cells.
Some scientists went on to hypothesis that the response that darwin found in the plants phototropism was a result of:
a. A chemical produced in the tipb. A electrical signal in the tip
What did boysen-jensen do?
Used two different materials to suggest whether phototropisms used a chemical or electrical signalThey took three plants, with the first they placed a thin barrier of mica on the illuminated side, with the second they placed a thin barrier of mica on the shaded side, and with the third they removed the tip and put a gelatin lock on top then put the tip on top of that. The first plant bent towards the light, he second didn’t, but the third did. This suggested it was chemicals on the shaded side coming from the tip which allowed the growth towards the light.
WHat is Mica?
an electrical conductor that does not allow chemical to diffuse through it
What is gelatin?
conducts chemicals but not electricity
What was Arpad Paal’s experiment?
The tips of two plants were removed then placed back on, but displaced to the side (one each way). It was found that the shoots bend towards the side where no tip is present.
There are two main divisions of the nervous system, what are they?
Central nervous system and peripheral nervous system
What makes up the CNS?
.Brain.Spinal cord
What makes up the PNS?
.Pairs of nerves from the CNS travelling to limbs and organs – sensory neuron, motor neuron
How are the CNS and PNS similar?
- Both carry electrical message
WHat is the PNS and what does it do?
.Pairs of nerves from the CNS travelling to limbs and organs.Relays messages from the CNS to the effector
What are the two main divisions of the PNS?
somatic, autonomic
WHat is somatic?
(voluntary) nervous system, conscious and involves the brain
What is autonomic?
(involuntary) nervous system, subconscious – reflex arc
What are reflexes?
Involuntary responses to a stimuli
The importance of reflexes?
.Safety/protection.Immediate (fast).Innate (not learnt).Prevent the brain from being overworked by not involving the conscious part.Automatic (unconscious)
Why are reflexes good?
.The brain can focus on complex behaviours.Escape predators, gain food or mates
what are Reflex Arcs?
The pathway of neurons involved in a reflex action
Key structures of reflex arc
.Stimuli.Sensory neuron.Motor neuron.Effector.Relay/intermediate neuron.Spinal cord.Receptor
Define the key structures of the reflex arc
Stimuli The external or internal environmental changeSensory neuron The neuron which carries the signal from the receptor to the intermediate neuronMotor neuron The neuron which carries the signal from the spinal cord to the effectorEffector The muscle or gland which is stimulated to respondRelay/intermediate neuron Links the message between the sensory and motor neuronsSpinal cord The part of the CNSReceptor Receives the stimuli
What is a receptor?
.Any structure able to respond to a change
Key points about receptors
- Receive information and pass it to the CNS- Are specific in what they detect- Two main components for receiving information
What are the receptors two main components for receiving information?
o Sensory reception gathers information (sense organs)o Sensory perception is making sense of this information (function of the brain)
What happens to information after it has been gathered by receptors?
.Sensory information must be converted into information that the body understands.This is done by transducers (converts energy forms) .Sensory information nerve impulses.E.g. (a form of energy like heat, light or sound to action or potential)
Examples of receptors
.Pacinian corpuscle (skin).Rod and cone cells (eyes)
What does the Pacinian corpuscle respond to?
.Only responds to mechanical pressure
Where is the pacinian corpuscle found?
.Found deep in the skin:- Soles of feet- Fingers- External genitalia- Ligaments/tendons
As well as a receptor, what does the pacinian corpuscle act as?
a transducer
Describe the pacinian corpuscle
.The sensory neurone leads to a neurone ending.The neurone ending is surrounded by layers of connective tissue.This connective tissue contains blood capillaries and viscous gel, and is surrounded by a capsule
Why does the pacinian corpuscle need blood capillaries?
.It needs blood capillaries to supply it with oxygen and glucose so it can respire and produce ATP to survive, and remove CO2
Why does the pacinian corpuscle need a sensory neurone?
.It needs a sensory neurone to transport the signal to the intermediate neurone or CNS
Why does the pacinian corpuscle need a neurone ending?
.It needs a neurone ending to sense when change occurs and so send a signal, it’s in the middle so that even pressure is felt evenly at all angles
Describe how the nerve membrane in the pacinian corpuscle works
.When the nerve membrane is at rest, the stretch mediated sodium channels are very tight and do not allow the passage of molecules – this doesn’t allow the diffusion of Na+ into the cell from the outside.When pressure is applied the membrane of the nerve ending becomes stretched, this causes the stretch mediated sodium channels to open and so allow the passage of molecules – this allows the diffusion of Na+ into the cell from outside
How does the pacinian corpuscle work?
.Sensory neurone has sodium channel in its plasma membrane called stretch-mediated sodium channel.Permeability to sodium ions changes when they change shape.Pressure on skin = pressure on lamellae = pressure on neuron = stretch mediated channels open = sodium influx = generator potential (nerve impulse) occurs
What is the pacinian corpuscle like when no pressure is applied?
.Stretch-mediated sodium channels are narrow.Sodium ions cannot/few pass through.A generator potential is not established
Describe how our sight works, how does light turn into an image in our brain?
.Light passes through the cornea which bends it.Light goes through the pupil and is focused further by the lens.An image is formed on the light sensitive cells in the retina.Retina sends an impulses along the sensory neurones in the optic nerve.The brain converts impulses into pictures
What is the retina?
Innermost part of the eye where light receptors are found
What are the light receptor cells?
The eye has two types of photoreceptors, found primarily at the retina:1. Rod cells2. Cone cells
How are rod and cone cells similar?
Both act as transducers.Both convert light energy into the electrical energy of a nerve impulse.Both are specific to different stimuli
How do red and cone cells work?
- Contain a specific pigment- Pigment is broken down by a specific wavelength of light- If broken down a message is sent to the brain
What is there more of, rod or cone cells?
rod cells (20:1)
What pigment is present in rod cells?
Rhodopsin
What pigment is present in cone cells?
3 different pigments of iodopsin
Do rod cells see colour or black and white?
Black and white
Do cone cells see colour or black and white?
Colour
Where are rod cells found?
Top and bottom of eye
Where are cone cells found?
Fovea
Which light intensity is required to break down rod cells?
Broken down at low light intensities
Which light intensity is required to break down cone cells?
Broken down at high light intensity
Visual acuity of rod cell
low
Visual acuity of cone cell
high
Neural connections of rod cell
Often share a single sensory neurone (retinal convergence)
Neural connections of cone cell
Own bipolar cell connected to a sensory neurone
To create generator potential the pigment (rhodopsin) inside the rod cells must be broken down, but:
- Threshold value must be exceeded- Shared neurone ensures an additive effect of each lower light intensity
Describe how blood moves through the heart
Deoxygenated blood vena cavaright atriumatrioventricular valveright ventriclepulmonary artery (out the semi-lunar valve)lungsoxygenatedpulmonary veinleft atriumtricuspid valveleft ventricleaorta (and the semi-lunar valve)rest of the body.
Name the parts of the heart (not valves or nodes)
- Right atrium2. Right ventricle3. Left atrium4. Left ventricle5. Pulmonary artery6. Aorta7. Vena Cava8. Pulmonary vein
Two nodes control the heart beat, together they initiate the cardiac cycle, what are they?
.Sinoatrial node (SAN) – the natural pacemaker.Atrioventricular node (AV)
Describe how the heart is made to beat?
- SAN sends an electrical impulse across the atria, the atria contracts2. The AVN is non-conductive and stops the impulse travelling to the ventricles3. The electrical activity travels to the AVN4. After a pause, the AVN sends an impulse down the bundle of his5. The bundle of his conducts the impulse through the purkinje fibres6. This causes the contraction of the left and right ventricles from the bottom up
Why is the SAN considered the natural pacemaker?
as it sets the electrical output, and so makes the heart pump
Why are the purkinje fibres important?
as they make sure the electrical signal is sent to all the muscle cells so that the heart contracts fully
Where does the ventricle contract from?
The apex
What is the medulla oblongata?
.A cone shaped neuronal mass.Responsible for involuntary functions.Contains the cardiac, respiratory and vomiting centres.Controls breathing, heart rate and blood pressure
What two centres are in the cardiac centre of the medulla oblongata? How are they linked to the SAN?
- Increases HRo Linked to SAN by the sympathetic nervous system- Decreases HRo Linked to SAN by the parasympathetic nervous system
What types of receptors are responsible for rate of heart beat?
- Chemical changes in the bloodo (chemoreceptors in the carotid arteries)- Pressure changes in the bloodo (Pressure receptors in the carotid arteries and aorta)
How does the body respond when blood pressure is high?
- Nerve impulse is sent to the centre in the medulla2. The centre sends an impulse via the parasympathetic nervous system to the SAN3. This decreases the rate at which the heart beats
How does the body respond when blood pressure is low?
- Nerve impulse is sent to the centre in the medulla2. The centre sends an impulse via the sympathetic nervous system to the SAN3. This increases the rate at which the heart beats
Describe what chemoreceptors are and where they are?
.Found in the walls of the carotid arteries (serve the brain).Detect pH changes in the blood
What are changes in the pH of blood caused by?
- Carbon dioxide in the blood
How does the Medulla Oblongata control blood pH? (6 marks)
.High respiratory rate.Releasing a lot of carbon dioxide into the blood.Carbon dioxide in blood decreases the pH.The change in pH is picked up by the chemoreceptors in the walls of the carotid arties.A nerve impulse is sent to the cardiac centre in the medulla oblongata.The centre sends an impulse via the sympathetic nervous system to the SAN.This increases the rate at which the heart beats.This means more blood is being pumped round the body, to pick up the extra CO2 and resultantly increase the pH of the blood back to normal levels
What is homeostasis?
The maintenance of a constant internal environment.
What does homeostasis control?
- Water level (osmoregulation)- Tissue fluid- Oxygen levels- Temperature (thermoregulation)- Composition of blood- Blood sugar levels
5 main stages of feedback mechanisms
Stimuli (change in the internal or external environment) receptor (detects variation) control unit (co-ordinates the response) effector (returns the body to set point) output (returns body to set point) feedback loop (tells receptor about change) stimuli etc.
WHat is thermoregulation?
The control of internal body temperature
What is the difference between an ectotherm and an andotherm?
Ectotherm – maintains a proportion of their heat from sources outside of their bodies (lizards and snakes)Endotherm – derive heat from sources metabolic activities inside of their bodies (mammals and birds)
What is the hypothalmus?
- The control unit for most responses- Link the nervous system and the endocrine system via the pituitary gland- Responsible for the production of hormoneso Temperature regulation, thirst, hunger, sleep, mood, and the release of other hormones within the body
Finish the stages of the feedback mechanism of an increase in temperature
Stimuli (increase in temperature) receptor (skin senses the increase in temperature and sends a signal to the control unit) control unit (hypothalamus) effector (sweat, vasodilation, pilorelaxation) output (reduced body temperature) stimuli (reduced body temperature) etc.
Finish the stages of the feedback mechanism of a decrease in temperature
Stimuli (decrease in temperature) receptor (skin senses the decrease in temperature and sends a signal to the control unit) control unit (hypothalamus) effector (vasoconstriction, shiver, piloerection) output (increased body temperature) stimuli (increased body temperature) etc.
Why is it good that the body has several different receptors?
- Changes can be detected by several different receptors- The brain has a better picture of what is being altered- Allows a more informed response to be made
What are the two forms of feedback?
- Positive feedback- Negative feedback
- Changes can be detected by several different receptors, meaning that …. menaing that ….
- Meaning that the brain has a better picture of what is being altered- Meaning that a more informed response is made
What is positive feedback?
A deviation from normal conditions is amplified, leading to a further deviationThis increases any change
Examples of positive feedback
- Blood clotting- Oxytocin causes more contractions- Adrenaline levels
What is negative feedback?
Initiating corrective mechanism whenever the internal environment deviates from its normal or acceptable levelReturns conditions to the normReverses any change
Where does glucose in our bodies come from?
diet (carbohydrate break down) and liver (glycogenolysis, glycogenesis, and gluconeogenesis)
What is glycogenolysis?
o Glycogenolysis – the breakdown of glycogen into glucose
What is glycogenesis?
o Glycogenesis – formation of glycogen by converting excess glucose
What is gluconeogenesis?
o Gluconeogenesis – production of glucose from glycerol and amino acids (liver)
Why is the pancreas important?
The pancreas produces:- Digestive enzymeso Proteaseo Amylaseo Lipase- Production of hormoneso Insulin Decreases blood sugar levelso Glucagon Increases blood sugar levels
What are hormones?
- Chemical messengers- Secreted from endocrine glands
What do hormones work on?
- Act on target cellso Cells that have complementary hormone receptors
The second messenger model of hormone actions is used by what type of hormones?
Non-lipid soluble hormones
Where does the second messenger model of hormone actions initiate a response?
inside of cells
Describe how adrenaline works within its second messenger model
- Adrenaline binds to a transmembrane protein receptor within the cell-surface membrane of a liver cell2. The binding of adrenaline causes the protein to change shape on the inside of the membrane3. The change of protein shape leads to the activation of an enzyme called adenyl cyclase, the activated adenyl cyclase converts ATP to cyclic AMP4. The cAMP acts as a second messenger which binds to protein kinase enzyme, changing its shape and therefore activating it5. The active protein kinas enzyme catalyzes the conversion of glycogen to glucose which moves out of the liver cell by facilitated diffusion and into the blood, through channel proteins
What are the islets of Langerhans?
- Hormone producing cellso α cells – glucagon (larger)o β cells – insulin (smaller)
Cyclic AMP activates Kinase which converts what?
glycogen to glucose
Insulin and glucagon work in what way?
Antagonistically
Descibbe the negative feedback for Increase in Blood Glucose Concentration –
- Beta cells detect increase in blood glucose concentration2. Secretes insulin3. Binds to glycoprotein receptors4. Activates enzyme inside cell5. Changes tertiary structure of glucose transport protein channel6. Channels open7. More glucose is absorbed by their liver and muscle cell8. Glucose is converted to glycogen and fat9. Blood sugar concentrations decrease
Describe the negative feedback for decerase in blood glucose concentration
- Alpha cells detect decrease in blood glucose concentration2. Secretes glucagon into blood plasma3. Binds to glucagon receptors4. Only liver cells have glucagon receptors so only they respond5. Glucagon binds to target cells6. Activates kinase enzyme inside cell which convert glycogen to glucose (glycogenolysis)7. Gluconeogenesis also occurs, the synthesis of glucose from glycerol and amino acids8. Glucose is released into the blood sugar9. Blood sugar concentrations increase`
What is diabetes?
- Diabetes mellitus / sugar diabetes- Chronic disease- Cannot metabolise carbohydrates/glucose effectively
What does Chronic disease mean?
o Persistent or long lastingo Oro A disease that comes with time
What are the two forms of diabetes?
o Type 1 Insulin dependento Type 2 Insulin independent
Describe type 1 diabetes
Insulin dependentChildhood onsetTreat with insulin injections, biosensor, exercise, and dietCannot produce insulin25% of diabetics are type 1Can be caused by an autoimmune disease, immune system attacks beta cellQuick developing
Describe type 2 diabetes
Insulin independentDevelops in adulthood (40+)Treat with carbohydrate intake and exercise, occasionally insulin prescribed, some drugs also slow down glucose absorptionMostly developed from obesity and poor dietGlycoprotein receptors lose their responsiveness to insulin or reduced supply of insulin from pancreasSlow developingCan go unnoticed as symptoms less severe
What are the symptoms of diabetes?
Very tired, high blood glucose levels, glucose in urine, thirst and hunger, urinate freuqnlty, weigh loss, blurred vision caused by the lends of you eye changin shape
How does doabetes cause tiredness?
o Less glucose intake, less glucose for respiration, less respiration, less energy
How does doabetes cause high blood glucose levels?
o Less glucose intake, it stays in blood fluid
How does doabetes cause glucose in urine?
o High concentrations of urine, it is removed from the body as waste in urine
How does doabetes cause thirst and hunger?
o High concentrations of glucose in blood causes low water potentials and thirsto Lots of digested carbohydrates removed from body so hungry
How does doabetes cause frequent urination?
o Lower water potential in blood so water moves in by osmosis and removed in urine
