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42 Cards in this Set
- Front
- Back
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What do efferent neurons do? |
Carry information away from the CNS. |
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What do afferent neurons do? |
Carry information into the CNS from the PNS. |
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What are the two types of efferent neurons and what parts of the body do they target? |
Autonomic - smooth muscle of organs |
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What are the types of afferent neurons? |
Sensory neurons & sensory receptors |
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What do interneurons do and where are they located? |
integrate information between neurons --> located within CNS. |
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What is a synapse? |
A region of contact between two neurons or one neuron and a muscle. |
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Presynaptic neurons... |
Sends a signal |
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Postsynaptic neurons... |
Receives a signal |
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Sensory neurons can be divided into what two morphological classifications? |
Bipolar & psuedounipolar --> SBP (sensory, bipolar, pseudounipolor) |
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Interneurons can be divided into what morphological classifications? |
Anaxonic and multipolar (IMA --> interneurons, multipolar, anaxonic) |
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The CNS is composed of... |
The brain and spinal cord |
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The PNS is composed of... |
Neurons that lie outside (or partially lie) outside the CNS |
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True/ False: there are more neurons than glial cells |
False - Glial cells outnumber neurons by 10-50:1 |
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What do all glial cells do? |
Communicate with and support neurons. |
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What are the glial cells of the PNS and what function do they serve? |
Schwarn cells - form myelin sheath and release neurotrophic factors |
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What are the glial cells of the CNS and what function do they serve? |
Oligodendrocytes - form myelin sheath Astrocytes - uptake of K+, form blood-brain barrier, support, secrete neurotrophic factorss |
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What do neurotophic factors do and give an example of one |
Promote development and survival of neuonrs. E.g. = nerve growth factor. |
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Taking up H2O and ions by astrocytes results in what? |
regulate ionic composition and volume of the ECF surrounding neurons. |
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Taking up neurotransmitters by astrocytes results in what? |
Prevention of continued action potentials |
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Astrocytes provide neurons with substances needed for ATP production |
True |
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In the PNS, each schwann cell myelinates approximately how much myelin by wrapping layers of it own membran earound the axon? |
1-1.5mm |
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True False? "Hundreds of Schwann cells may myelinate a single long axon.` |
True |
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Nerve impulses in axon myelination (PNS) are produced where? |
Nodes of ranvier |
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Can oligodendrocytes (CNS) myelinate one or several neuorons at one time? |
Several - process is similar to Schwann cell myelination but oligodendrocytes can myelinate several neurons at once (schwann cells only myelinate one cell) |
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What is white matter? |
areas of the CNS that contain high numbers of MYELINATED CELLS |
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What is grey matter? |
Areas of the CNA that contain a high number of cell bodies, dendrites and UNMYELINATED axons |
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What is a membrane potential? |
Electrical potential difference across a cell membrane i.e. difference in electrical charge inside/outside cell |
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What does membrane potential depend on? |
1) Ion permeability 2) [+ve] & [-ve] ions on each side of the membrane (electrochemical force) |
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What is hyperpolarisation? |
Membrane potential becoming more negative |
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What is depolarisation? |
Membrane potential becoming more positive |
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Channels may be... (explain each one) |
a) voltage-gated - Opens/closes in repsonse to membrane potential (selective for particular ions) c) mechanically-gated - Opens/closes in response to physical forces (vibrations, stretches etc.) |
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The size of hyperpolarisation/depolarisation is directly proportional to what in graded potentials? |
Stiumulus strength |
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Where do graded potentials occur and what happens to the potential a it travels (and why)? |
Occurs at dendrites and cell body. They lose strength with distance from site of initiation due to current leak across non-insulated membrane and resistance from cytoplasm to current leak |
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(Graded potentials) - "Two potentials arriving close together in time..." |
May sum to produce a larger response |
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(graded potentials) When are action potentials only generated? |
When the graded potentials are large enough (suprathreshold) |
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(Action potentials) - "All or none" Describe why action potentials are desribed as this. |
Either occur (if stimulus reaches threshold) or do not (if stimulus is subthrehold) |
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(Action potentials) - What affects the strength and duration of a stimulus? |
Frequency of action potentials (no. per unit of time). |
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(Action potential) - Where do they occur and what happens to it as it travels? |
Axon hillock - no reduction in strength with distance from site of initiation |
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(action potentials) - does summation occur and if so/not why? |
No - due to refratory period |
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Draw a graph of an action potential and label/describe all the ponits (1-9) |
1- Resting membrane potential 2- Depolarising event occurs 3-Na+ channels open s due to depolarisation of membrane 4- Na+ enters = depolarisation 5-Na+ channel closes; K+ open 6-K+ leaves cell 7-cell hyperpolarises due to loss of K+ 8-K+ close 9- Resting membrane potential restored |
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A refractory period prevents... |
backward conduction |
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What two factors affect speed of conduction |
Axon diameter and myelination |
