Nerves

HideShow resource information
What are sensory receptors
They are TRANSDUCERS. They detect stimuli and then convert the energy of the stimulus into another form of energy so that it can be transferred as a nerve impulse (electrical energy)
1 of 35
State what type of receptors detect light intensity and wave lengths
High sensitive cells (rods and cones) in retina of eye
2 of 35
State what type of receptors detect presence of volatile chemicals
Olfactory cells lining inner cavity of nose
3 of 35
State what type of receptors detect presence of soluble chemicals
Taste buds in tongue
4 of 35
State what type of receptors detect presence of pressure on skin
Pressure receptors on skin (PARCINIAN CORPUSCLES)
5 of 35
State what type of receptors detect vibrations in air
Sound receptors in the inner ear (cochlea)
6 of 35
State what type of receptor detects length of muscle fibres
Muscle spindles (PROPRIOCEPTORS)
7 of 35
Describe the role of the sodium potassium pumps
Actively transport Na+ ions & K+ ions into and out of neurone.
8 of 35
Describe the role of Na-K pumps in maintaining the resting potential
The pump actively transports 3Na+ ions out of the cell for every 2K+ ions into the cell. This makes inside of cell negatively charged. Channels impermeable to Na+ ions but K+ ion channels are semipermeable "leaky"
9 of 35
Briefly explain how a nerve impeller is created
Permeability of nerve cell membrane to sodium ions is increased changing potential difference across membrane. Inside of cell becomes less negative causing depolarisation
10 of 35
What determines whether an action potential is generated or not
The number of sodium ions that diffuse into the cell to reach the threshold potential. The size of the stimulus will decide how many Na+ ion channels open
11 of 35
Describe sensory neurone
Carries impulse from receptor to CNS. Cell body in the middle. Long dendron. Short axon
12 of 35
Describe motor neurone
Carries impulse from CNS to effector. Cell body at end. Long axon. Short dendrites extending from cell body
13 of 35
Describe schwann cells
They produce myelin which forms the myelin sheath. Insulates the axon which is carrying the impulse. Gaps called nodes of ranvier which enable saltatory conduction and a faster transmission of impulse as it jumps from node to node
14 of 35
What is the potential difference across the membrane at the resting potential
-60mV
15 of 35
What is the potential difference said to be during depolarisation
+40mV
16 of 35
Describe the ionic movements during depolarisation
Sodium ion channels open causing sodium ions to diffuse into neurone. This causes depolarisation and threshold value -50mV reached.Voltage gated Na ion channels open so more Na ions diffuse in +40mV. Na channels close K channels open.
17 of 35
What is the potential difference at the threshold value
-50mV
18 of 35
Describe ionic movement during Repolarisation
K ions diffuse out of cell so potential difference is more negative inside cel compared to outside
19 of 35
Describe ionic movement during hyper polarisation
Potential difference overshoots slightly
20 of 35
Describe refractory period
Concentration of sodium and potassium ions inside and outside of cell are restored. No action potential at this time allowing the cell to recover and ensuring action potentials are transmitted in only one direction
21 of 35
Briefly explain how are local currents generated
Opening of sodium ion channels at one point upsets the balance of sodium and potassium ions. So, sodium ion channels open further along membrane
22 of 35
Describe ionic movements of the formation of local currents
Na+ ion channels open at a particular point along neurone when action potential generated. Allows Na ions to diffuse from higher conc outside neurone into neurone.upsets balance created by Na/K pumps causing Na to diffuse sideways opening up Na chann
23 of 35
What is a synapse
The junction between two neurones
24 of 35
What 3 main features are their for the synaptic knob
Many mitochondria indicating that it is an active process needing ATP. Vesicles containing ACh. Voltage gated Ca2+ ion channels in membrane
25 of 35
What are the main features in a postsynaptic membrane
Contains specialised sodium ions channels consisting of 5 pp molecules. 2 polypeptides have special receptor site specific to ACh. Receptors complementary shape to ACh. When ACh binds into site Na ion channels open
26 of 35
How is an action potential transmitted up till it being released into synaptic cleft
AP arrives at synaptic knob. Voltage gated Ca2+ ion channels open. Ca2+ ions diffuse in causing vesicles to move and fuse with presynaptic membrane. ACh released by exo and diffuse across synaptic cleft.
27 of 35
Describe rest of passage of transmission across synapse from when ACh in synaptic cleft
ACh binds to receptors on Na+ ion channels. Na+ ion channels open causing Na+ to diffuse into PostSM. Generator potential created. If meet threshold potential then action potential created in POSTSM
28 of 35
What is the role of AChE
Enzyme found in synaptic cleft. Hydrolyses Ach into Acetyl and Choline. Stops transmission of signals so that synapse does not continue to produce action potentials in POSTSM. A and Ch reenter synaptic knob by diffusion and are recombined using ATP
29 of 35
List roles of synapses
Allows neurones to communicate.Ensures transmission in 1D only.Allows convergence from many neurones to be passed to one neurone. Divergence = opposite.Filters out low level stimuli
30 of 35
When a stimulus is at higher intensity the sensory receptor will produce more generator potential. What will this cause
More frequent action potentials i the sensory neurone. More vesicles will be released when action potentials arrive at synapse. Higher frequency of action potentials in postSM.
31 of 35
Describe the structure of a myelinated neurone
Neurone is insulated by an individual myeline sheath. Wrapped around like sausage role (axon = sausage and myeline sheath = pastry)
32 of 35
Describe the structure of an unmyelinated neurone
Still associated with schwann cells but several neurones enshrouded in one lonely wrapped scan cell meaning that the action potential moves along the neurone in a wave rather than jumping node to node
33 of 35
Where are non myelinated neurones used
Shorter and carry signals only over a short distance. Used in coordinating body functions e.g. breathing. Therefore increased rate of transmission not as important
34 of 35
Where are myelinated neurones used
Carry signals over long distances increasing speed of transmission means signal reaches end of the neurone more quickly enabling a more rapid response
35 of 35

Other cards in this set

Card 2

Front

State what type of receptors detect light intensity and wave lengths

Back

High sensitive cells (rods and cones) in retina of eye

Card 3

Front

State what type of receptors detect presence of volatile chemicals

Back

Preview of the front of card 3

Card 4

Front

State what type of receptors detect presence of soluble chemicals

Back

Preview of the front of card 4

Card 5

Front

State what type of receptors detect presence of pressure on skin

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Cellular processes and structure resources »