Aqa a level Biology - Topic 6 - survival and response questions and answers well illustrated.

Aqa a level Biology - Topic 6 - survival and response questions and answers well illustrated. What is a stimulus? - correct answer. A change in the environment of an organism What is a tactic response? - correct answer. Directional movement in response to a stimulus What is a kinetic response? - correct answer. Non directional random movement in response to a stimulus What is a positive and negative taxis? - correct answer. Positive taxis- organism moves towards stimulus Negative taxis - organism moves away from stimulus What Are receptors? - correct answer. Detect stimuli- can be cells or proteins on cell surface membrane , loads of different types What are effectors? - correct answer. Cells that bring about a response to a stimulus to provide an effect ( muscle cells, glands) Receptors communicate with effectors via the ....... - correct answer. Nervous or hormonal system or both What are the 3 types of neurones? - correct answer. Sensory neurones Motor neurones Relay neurones What do sensory neurons do? - correct answer. They carry impulses from receptors to the CNS. What do motor neurones do? - correct answer. Transmit electrical impulses from the central nervous system to the effectors What do relay neurones do? - correct answer. Transmit electrical impulses between sensory neurones and motor neurones What is the order of nervous communication including neurones - correct answer. Stimulus receptors sensory neurones CNS motor neurone effectors response Outline nervous communication - correct answer. - Stimulus detected by receptor cells and electrical impulse sent along sensory neurone - Electrical impulse reaches end of neurone ,neurotransmitters take info across synapse to the next neurone where another impulse is generated - the central nervous system processs info and sends impulses along motor neurones to effector Explain what neurotransmitters do - correct answer. They're chemical messengers secreted onto target cells creating a localised response which is rapid and short lived as they're quickly removed after they've done their job What is a simple reflex? - correct answer. Rapid involuntary response to a stimulus, goes through spinal cord but not conscious part of the brain - they're protective a fast What is the reflex arc? - correct answer. Pathway of neurones linking receptors to effectors What is a tropism? - correct answer. Response of a plant to a directional stimulus What is a positive tropism? - correct answer. Growth towards the stimulus What is a negative tropism? - correct answer. Growth away from stimulus What is a phototropism? - correct answer. Growth of a plant in response to light Shoots are .................. phototropic and grow .................. light - correct answer. Positively Towards Roots are ............... phototropic and grow .................. from the light - correct answer. Negatively Away What is gravitropism? ( aka geotropism) - correct answer. Growth of a plant in response to gravity Shoots are ..................... gravitropic and grow ................ roots are ............... gravitropic and grow .............. - correct answer. Negatively Upwards Positively Downwards What are growth factors? And where are they produced? - correct answer. Hormone like chemicals in plants that speed up or slow down plant growth Produced in Growing regions of plant and move to where needed What are auxins? - correct answer. plant hormones - growth factors How do auxins work? - correct answer. Produced in tips of shoots and diffuse backwards to stimulate the cell just behind the tips to elongate What is indoleacetic acid ( IAA) ? - correct answer. An auxin that is produced in the tips of shoots and roots Explain the movement and affects of indoleacetic acid in plants - correct answer. Moves around to control tropism- moves by diffusion and active transport over short distances and via the phloem in long distances. This results in different concentrations leading to uneven growth, Root growth is ..................... by high concentrations of IAA . Shoot growth is ................ by high concentrations of IAA - correct answer. Inhibited Promoted What is the resting potential? - correct answer. The potential difference ( or voltage) when a cell is at rest When a nervous system receptor is in its testing state, the inside is .................. charged compared to the outside - correct answer. Negatively What is a generator potential? - correct answer. The change in potential difference due to a stimulus A bigger stimulus excites the membrane more causing a bigger movement in ............ and a bigger change in ............... ................. so a bigger .................. ....................... is produced - correct answer. Ions Potential difference Generator potential What is an action potential? - correct answer. An electrical impulse along a neurone triggered if the generator potential is big enough An action potential is only triggered if the generator potential reaches a certain level called............ - correct answer. Threshold level Action potentials are all one size so the strength of the stimulus is measured by what? - correct answer. The frequency of action potentials What are pacinian corpuscles? - correct answer. Mechanoreceptors-detect mechanical stimuli such as pressure and vibrations What is a sensory nerve ending? - correct answer. End of a sensory neurone and is wrapped in loads of connective tissue called lamellae Explain what happens when a pacinian corpuscle is stimulated - correct answer. Lamellae are deformed and press on sensory nerve ending, this causes s the neurones cell membrane to stretch which deforms the stretch mediated ion channels, channels open and sodium ions diffuse into cell creating generator potential What are photoreceptors? - correct answer. Receptors in your eye that detect light Light enters the eye through the ................... - correct answer. Pupil The amount of light that enters the eye is controlled by the muscles of the ............. - correct answer. Iris Light rays are focused by the ............... onto the .................. which lines the inside of the eye - correct answer. Lens Retina Photoreceptor cells are found in the ...... - correct answer. Retina The ................ is an area of the retina where there are lots of photoreceptors - correct answer. Fovea Nerve impulses from the photoreceptor cells are carried from the retina to the brain by the .................. - correct answer. Optical nerve Where the optic nerve nerve leaves the eye is called the .................. there are no photoreceptors here - correct answer. Blind spot Outline how photoreceptors work ( 4 steps) - correct answer. 1. Light enters the eye, hits the photoreceptors and is absorbed by light sensitive optical pigments 2. Light bleaches pigments causing chemical change and altering membrane permeability to sodium ions 3. Generator potential is created and if it reaches threshold a nerve impulse is sent along a bipolar nerve 4. Bipolar neurones connect photoreceptors to the optic nerve which takes impulses to brain What are the 2 types of photoreceptors in the human eye - correct answer. Rods and cones Whereabouts in the eye are rods and cones found? - correct answer. Rods- peripheral parts of retina Cones- packed together in fovea Which photoreceptor give information in black and white? - correct answer. Rods Which photoreceptors give information in colour? - correct answer. Cones What are the 3 types of cones? - correct answer. Red sensitive Blue sensitive Green sensitive How are we able to see the colour yellow? - correct answer. The frequency of light which falls between red and green stimulates both red and green sensitive cones so the brain converts this as yellow Why are rods sensitive to light? - correct answer. Many rods join one bipolar neurone, so many weak generator potentials combine to reach threshold and trigger an action potential Why are cones less sensitive than rods? - correct answer. One cone joins one bipolar nerve , so it takes more light to reach the threshold and trigger an action potential What is visual activity? - correct answer. The ability to tell points apart that are close together Why do rods give low visual activity? - correct answer. Many rods join the same bipolar nerve which means light from 2 points close together can't be told apart Why do cones have high visual activity? - correct answer. Cones are close together and one cone joins one neurone so when light from two points hits two cones two action potentials go to the brain so you can distinguish between them as two separate points The nervous system is split into two different systems called..... - correct answer. The central nervous system The peripheral nervous system What is the central nervous system made up of? - correct answer. Brain and spinal cord What is the peripheral nervous system made up of? - correct answer. The neurones that connect the central nervous system to the rest of the body What are the 2 systems of the peripheral nervous system? - correct answer. Somatic nervous system Autonomic nervous system What does the somatic nervous system control? - correct answer. Conscious activities eg running What does the autonomic nervous system control and what 2 systems does it split into? - correct answer. Unconscious activities such a digestion Sympathetic and parasympathetic nervous systems What is the sympathetic nervous system? - correct answer. fight or flight gets you into action What is the parasympathetic system? - correct answer. Rest and digest system that calms the body down Which nervous system is involved in the control of the heart rate? - correct answer. The autonomic nervous system Explain what is meant by " cardiac muscle is myogenic" - correct answer. It can contract and relax without receiving signals from nerves What are the 4 main points in order in the route of waves of electrical activity in the heart? - correct answer. SAN (sinoatrial node) AVN (atrioventricular node) Bundle of His Purkyne fibres What does SAN stand for and what is it? - correct answer. Sino-atrial node - small mass of tissue in the wall of the right atrium which sets the rhythm of the heartbeat by sending out regular waves of electrical activity to the atrial walls What does AVN stand for and what is it? - correct answer. Atrioventricular node- responsible for passing the waves of electrical activity to the bundle of His , slight delay before it reacts to make sure the atria have emptied What is the bundle of His? - correct answer. Group of muscle fibres responsible for conducting the waves of electrical activity between the ventricles and apex of the heart. Splits into finer muscle fibres in left and right ventricle called purkyne tissue What is purkyne tissue? - correct answer. Muscle fibres from bundle of His which carries waves of electrical activity into the muscular walls of the left and right ventricle causing them to contract simultaneously from the bottom up The rate of which the SAN fires is .................... controlled by a part of the brain called the ..................... - correct answer. Unconsciously Medulla What are internal stimuli detected by? - correct answer. Pressure and chemical receptors Which pressure receptors are found in the aorta and carotid arteries that are stimulated by high and low blood pressure? - correct answer. Baroreceptors Which receptors are found in the aorta, carotid arteries and the medulla which monitor oxygen levels in the blood - correct answer. Chemoreceptors During high blood pressure, ....................... detect it, send impulses along sensory neurones to the .................., this then sends impulses along ...................... neurones, these secrete ................. which binds to receptors on the .................. and the heart rate slows down - correct answer. Baroreceptors Medulla Parasympathetic Acetylcholine SAN During low blood pressure, .......................... detect it and send impulses along sensory neurones to the .............. which sends impulses along ........................ neurones, which secrete ................ which binds to receptors on the .......... causing the heart rate to speed up - correct answer. Baroreceptors Medulla Sympathetic Noradrenaline SAN During high oxygen , low co2 or high ph levels, ....................... detect it , send impulses along sensory neurones to the .............. which sends impulses along .................... neurones which secrete ........................ this binds to receptors on the ........... and causes heart rate to ................ in order to return levels back to normal - correct answer. Chemoreceptors Medulla Parasympathetic Acetylcholine SAN Decrease