2564148
Description
Flashcards by Charlotte Lloyd, updated more than 1 year ago
|
Created by Charlotte Lloyd
over 9 years ago
|
|
| Question | Answer |
| What is a stimulus? | A detectable change in the internal or external environment of an organism that produces a response in the organism |
| What is a receptor? | Something which detects stimuli, They transform the energy from a stimulus into a form of energy that can be processed by an organism and leads to a response |
| What is an effector? | Soemthing (an organ) that carries out a response |
| What is a coordinator? | Links the receptor and effector, acts like a switchboard processing information from receptors to formulate a response on the effectors |
| What is meants by the term taxes? | When an organism responds directly to environmental changes by moving its whole body either towards a favourable stimuli or away from an unfavourable one |
| What is the difference between a positive or negative taxes? | Positive taxis is movement towards a stimulus Negative taxis is movement away from a stimulus |
| What is kinesis and what is its purpose? | A non-directional response; the more unpleasant the stimulus the more rapid the movement and direction change; response designed to bring an organism back into favourable conditions; important when stimulus is not directional |
| What is a trophic response? | Growth as a result of a directional stimulus |
| What is meant by the following terms: a) Positive phototropism; b) Negative phototropism; c) Negative hydrotropism; | a) plant grows towards the light b) plant grows away form the light c) plants (roots) grown towards water |
| What does the central nervous system compose of? | The brain and the spinal cord |
| What does the peripheral nervous system compose of? | Pairs of nerves that originate in either the brain or the spinal cord |
| What is the peripheral nervous system further divided into? | The somatic (voluntary) nervous system and the automatic nervous system |
| Which two types of neurones are involved in the peripheral nervous system? | Sensory and motor |
| What function do sensory neurones carry out? | Carry nerve impulses from receptors to the central nervous system (CNS) |
| What function do motor neurones carry out? | Carry nerve impulses away from the central nervous system (CNS) to the effector |
| What is the difference between the somatic (voluntary) and automatic nervous system? | The somatic (voluntary) nervous system carries impulses to body muscles under conscious control The automatic nervous system carries impulses to glands and smooth and cardiac muscles under subconscious control |
| Describe the sequence of a reflex arc, use the example of touching a hot object | 1. Stimulus: ie heat from the object 2. Receptor: ie temperature receptors 3. Sensory neurone to the spinal cord 4. Intermediate neurone, linking sensory and motor neurones to the spinal cord 5. Motor neurone to muscles in the arm 6. Effector: muscles contract 7. Response: pulling hand away |
| Describe the importance of a reflex arc | They are involuntary and so do not require decision, thus allowing the brain free to carry out complex thought; Protect from harmful stimuli; Fast as neurone pathways are short, with few impulses |
| What is the automatic nervous system divided into? | Sympathetic nervous system and the parasympathetic nervous system |
| Why are the parasympathetic and sympathetic nervous systems described as being antagonistic? | they oppose each other |
| Generally, what does the parasympathetic nervous system do? | Inhibits effects and so slows down activity; Controls activity under normal resting conditions |
| Generally, what does the sympathetic nervous system do? | Stimulates effectors and so speeds up activity; Helps cope with stressful situations by heightening awareness and preparing the body for activity (the fight or flight response) |
| What are changes in heart rate controlled by? | The medulla oblongata in the brain |
| Describe the medulla oblongata | Has two centres; One centre increase heart rate, the other decreases heart rate |
| What is the centre to increase heart rate (in the medulla oblongata) linked to the sinoatrial node by? | The sympathetic nervous system |
| What links the centre to decrease heart rate in the medulla oblongata to the sinoatrial node? | The parasympathetic nervous system |
| Which two things determine which centre in the medulla onlongata is stimulated? | Chemical changed in the blood, detected by chemoreceptors; Pressure changes in the blood, detected by pressure receptors |
| Where are chemorecptors found, and what are they receptive to? | Found in the wall of the carotid arteries; Sensitive to changes in blood pH as a result of changes in the concentration of carbon dioxide |
| Describe the process of events which occur when the blood has a higher than normal concentration of carbon dioxide, in order to return carbon dioxide concentration back to normal levels | Carbon dioxide is high, pH is lower; Chemoreceptors detect this; Increases frequency of nervous impulses to the centre that increases heart rate; Centre increases frequency of impulses via the sympathetic nervous system to the sinoatrial node; Increasing heart rate, more CO2 removed by the lungs so level returns to normal |
| Describe how blood pH is maintained at a normal level | Decreases in blood pH stimulates the centre to increase heart rate, which increases frequency of impulses (via sympathetic nervous system) to the SAN, increasing heart rate, more CO2 removed so pH returns to normal, chemoreceptors detect this, medulla oblongata decreases frequency of impulses to SAN so heart rate decreases |
| Where are the pressure receptors found? | Within the walls of the carotid arteries and the aorta |
| What happens when blood pressure is higher than normal? | Receptors transmit a nervous impulse to the centre of the medulla oblongata that decreases heart rate; centre sends impulses to the SAN (via parasympathetic nervous system); decreasing heart rate |
| What occurs when blood pressure is lower than normal? | Receptors transmit a nervous impulse to the centre in the medulla oblongata which increases heart rate; centre sends impulses (via sumpathetic nervous system) to the SAN; increasing heart rate |
| What is the pacinian corpuscle sensitive to? | Specific to mechanical pressure |
| What is meant when the pacinian corpuscle is described as a transducer? | It acts as a transducer by converting the information provided by the stimulus (mechanical pressure) into a form that can be understood by the body |
| Describe the structure of the pacinian corpuscle | At the centre is a neurone with a special type of stretch-mediated sodium channel, surrounding the neurone is layers of connective tissue with a viscous gel in between layers, on the outside is a blood capillary |
| Explain how a pacinian corpuscle functions | In its resting state the stretch-mediates sodium channels are too narrow to allow sodium through = resting potential; When pressure is applied the membrane becomes stretched, changing shape; Stretching widens the sodium channels allowing sodium to diffuse through; Influx of sodium depolarises the membrane = action potential |
| In what part of the eye are light receptors found? | The innermost layer of the eye: the cornea |
| What do receptors in the eye do? | Act as transducers, converting light energy into the electrical energy of a nerve impulse |
| Describe the structure of rod cells: | Many rode cells share a single sensory neurone via a bipolar cell; the end of the cell is shaped as a rectangular rod |
| Describe the structure of a cone cell: | Each cone cell has its own bipolar cell attached to a single sensory neurone; the end of the cell is triangular cone shaped |
| What type of vision do rod cells give, why? | Cannot distinguish between different wavelengths of light therefore give black and white vision |
| Why do rod cells give poor visual acuity? | Many rod cells have a single sensory neurone, therefore they cannot distinguish between multiple stimuli |
| What is retinal convergence and what does it allow? | Multiple rod cells are attached to one bipolar cell (and sensory neurone) meaning the threshold potential is more likely to be exceeded, thus allowing vision in low light intensity |
| In addition to retinal convergence what else allows rod cells to work in low light intensity? | The pigment rhodopsin must be broken down in order to produce a generator potential (action potential); Rhodopsin requires low energy to broken down |
| What must happen for a generator potential to be produced in rod cells? | The pigment rhodopsin must be broken down; the threshold potential must be exceeded to do this |
| What type of vision do cone cells give, why? | Allows full colour to be seen; three different types which each respond to different wavelengths of light |
| Compare the number of rod cells and cone cells: | Much fewer cone cells than rod cells |
| Where about in the cornea are rod cells and cone cells found? | Rod cells found in the peripheral; Cone cells found in the fovea |
| Why do cone cells give good visual acuity? | Each cone cell has its own bipolar cell (and sensory neurone) so information from multiple stimuli cannot be combines to exceed threshold potential; each stimulus produces its own generator potential if it exceeds threshold potential |
| Why do cone cells only work in high light intensity? | The pigment iodopsin requires high light intensity to break down and so produce a generator potential; Cone cells cannot combine to exceed the threshold potential |
Want to create your own Flashcards for free with GoConqr? Learn more.