5315639
Description
Flashcards by Elena Cade, updated more than 1 year ago
|
|
Created by Elena Cade
over 8 years ago
|
|
| Question | Answer |
| The organisation of the nervous system: | |
| What do cell mediators 'Histamines' do? | Stored in white blood cells called mast cells. Released following tissue damage or bacterial infection or in response to an allergen like pollen. Causes swelling, redness and itching. Allows phagocytic white blood cells to move into tissue fluid and destroy bacteria. |
| What is myelination: | Schwann cells form a lipid-rich insulating layer around the axon called a myelin sheath. Gaps between the Schwann cells are called Nodes of Ranvier and are important in transmitting nerve impulses. |
| Diagram of a Motor Neuron: | |
| Function of the Cell body: | - Contains a nucleus and large amounts of Rough ER associated with the production of neurotransmitters. |
| Function of the Dendrons and Dendrites: | -Carry nerve impulses towards the cell body. |
| Function of the Axon: | -Single long fibre that carries nerve impulses away from the cell body |
| Function of Schwann Cells: | -Surrounds the axon protecting it and providing electrical insulation |
| Function of the Myelin Sheath: | -Made up of membranes of Schwann cells which are rich in the lipid Myelin |
| Function of the Node of Ranvier: | Gaps between Schwann Cells where there is no Myelin Sheath. |
| What does it mean for a membrane to be Polarised? | A membrane is said to be polarised if a potential difference is maintained across it with the inside being negative with respect to the outside |
| What does Resting Potential mean? | The resting potential is the potential difference which exists across the axon membrane when the neurone is not conducting an impulse The inside of the membrane is negative compared to the outside (-65mV) |
| The distribution of charges across the axon membrane: | |
| Explain what these proteins are used for: | Sodium ions moved out by sodium potassium pump; potassium ions moved in Potassium ions diffuse out through open potassium channel proteins Fewer sodium ions diffuse in through open sodium channel proteins |
| Resting Potential across an axon membrane: | |
| and another diagram: | |
| What is an Action Potential: | The change that occurs in the electrical charge across the membrane on an axon when it is stimulated and a nerve impulse passes |
| The active neruone: | The sodium-gated channels open and sodium ions rush into the neurone along their electrical and concentration gradients The sodium ions are positively charged and make the inside of the axon positive compared to the outside Eventually the potential difference across the membrane is reversed from -65 mV to about +40 mV. This is called the ACTION POTENTIAL and the nerve has become DEPOLARISED. |
| Recovery/Repolarisation: | The sodium-gated channels close so the membrane becomes less permeable to sodium ions The potassium-gated channels open and potassium ions diffuse out of the axon along a concentration and electrical gradient The membrane becomes positive outside compared to inside. It is said to be REPOLARISED, with a resting potential of -65 mV For a brief time the membrane becomes HYPERPOLARISED – it is more negative than the usual resting potential due to the potassium-gated channels staying open. The potassium gates close. The sodium-potassium pump restores the normal concentration of sodium and potassium ions across the axon membrane |
| Diagram of the Action Potential: | |
| The Sodium-Potassium Pump uses Active Transport to move... | 3 Sodium Ions out and 2 potassium ions into the cell |
| During Resting Potential: | Na+ - K+ pump working 2 k+ ions move into axon inside of the axon has a negative charge of -70mV 3 Na+ ions move out of axon outside the axon has a positive charge |
| When a Stimulus reaches a resting neurone (causing an action potential and depolarisation): | Na+ - K+ pump stops working Na+ gated channels open Na+ ions diffuse into the axon inside the axon has a positive charge of +40mV an outside the axon has a negative charge |
| What happens during Repolarisation: | Na+ gated channels close and K+ gated channels open K+ ions diffuse out of axon |
| When Resting Potential occurs again: | Na+ - K+ pump working again 2 K+ move into axon 3 Na+ move out of axon Inside the axon has a positive charge of -70mV Outside the axon has a positive charge |
| What is meant by potential difference? | unequal distribution of positively charged ions on each side of the cell membrane |
| How large is the potential difference across a membrane? | -65 |
| Which side of the membrane has the largest number of positive ions? | Tissue fluid outside axon (outside) |
| Which is found in the highest concentration on the outside of the membrane at rest? | sodium |
| Where do sodium ions go through the Gated-Channel proteins? | into the axon membrane |
| Where do potassium ions go through the Gated-Channel proteins? | out of the axon membrane |
| The arrival of an Action Potential at the end of the presynaptic neurone causes: | Calcium ion channels to open and calcium ions to enter the synaptic knobs. |
| What does the influx of calcium ions into the presynaptic neurone cause? | synaptic vesicles to fuse with the presynaptic membrane, releasing the neurotransmitter acteylcholine into the synaptic cleft. |
| What does the neurotransmitter acteylcholine then do? | it diffuses across the synaptic cleft and binds with receptor sites on sodium ion channels in the membrane of the post synaptic neurone. |
| What do the sodium ions channels then do? | The sodium ion channels open allowing sodium ions to diffuse in rapidly along a concentration gradient. |
| What does the influx of sodium ions cause? | The influx of sodium ions generates a new action potential in the post synaptic neurone. |
| Acetylcholine is then broken down into choline and ethanoic acid (acetyl) by which enzyme? | Acetylcholinesterase |
| What then happens to the products of this reaction? | Choline and ethanoic acid diffuse back into the synaptic knobs and are re-synthesised into acteylcholine. ATP from the mitochondria is needed for this. |
| What then happens to the sodium ion channels in the absence of acetylcholine in the receptor sites: | They close |
| Synaptic Transmission diagram: | |
| What is summation? | a single nerve impulse arriving at a synapse may release only a small amount of neurotransmitter - not enough to generate an action potential. |
| What is spacial summation? | several presynaptic neurones converge onto a single postsynaptic neurone. If the all release neurotransmitter, enough may be produced to fire an impulse in the postsynaptic neurone. |
| What is temporal summation? | a single presynaptic bulb fires several times in quick succession and enough neurotransmitter builds up to generate an excitatory postsynaptic potential. |
| Action Potential - when a stimulus reaches a resting neurone, the following sequence occurs: 1: | during the resting potential, some of the potassium voltage-gated channels are permanently open. The sodium voltage gated channels are closed. |
| 2: | The energy of the stimulus causes some sodium voltage gated channels in the axon membrane to open and sodium ions rapidly diffuses in along their electro-chemical gradient. |
| 3: | As the sodium ions diffuse in, more sodium voltage-gated channels open allowing more sodium ions to diffuse in. The inner surface of the membrane now has a positive of +40mV. This change in potential difference is called depolarisation and depolarisation of a small section of a nerve fibre causes an action potential. |
| Sympathetic nervous system: | Stimulus effector Speeds up activity Preparation for stressful activity (fight or flight, exercise ect.) |
| Parasympathetic nervous system: | Inhibits effectors Slows down activity Controls activity at rest - conserves energy and replenishes body's reserves |
| Control of the heart rate: | Controlled by the CARDIO-REGULATORY CENTRE IN THE MEDULLA of the brain |
| The difference between myelinated and unmyelinated nerves: | If the axon is covered with myelin sheath, the nerve impulse is faster, whereas the unmyelinated nerve is slower. |
Want to create your own Flashcards for free with GoConqr? Learn more.