4.1.2 NERVES
0.0 / 5
- Created by: upsidedown1004
- Created on: 02-06-16 11:27
What does the nervous system consist of?
neurons and glial (supporting cells)
1 of 39
What are sensory receptors?
transducers - convert different forms of energy into nerve impulses
2 of 39
Give some examples of sensory receptors
light sensitive cells in the retina// olfactory cells in the retina detect presence of volatile chemicals// tastebuds detect presence of soluble chems/ pressure receptors
3 of 39
What do sensory neurons do?
transmit impulses from receptors to the CNS
4 of 39
What does the Central nervous system consist of?
brain and spinal cord
5 of 39
What do motor neurones do?
transmit impulses from the CNS to effectors, such as muscles and glands
6 of 39
Describe the structure of motor neurones
a cell body at end with a large nucleus with lots of rough ER and golgi / many short dendrites that carry impulses to body/ long axon that carries impulse
7 of 39
Why do motor neurones have such large nuclei?
lots of Rough ER and golgi to synthesise proteins involved in impulse transmission
8 of 39
How is a potential difference established across a membrane?
result of an unequal distribution of ions// more anions being within the cell// Sodium-potassium pump actively transports 3Na+ ions out for every 2K+ in// axon contains organic ions which the mem is impermeable to (to Na+)
9 of 39
When not conducting an impulse, what is the value of the resting potential?
-60mV
10 of 39
How to neurones transmit nerve impulses over one distances?
uses reversals of the potential difference to 'boost' current flow
11 of 39
what is the difference between sodium and potassium channel proteins?
sodium channel proteins are much more sensitive to changes in pd
12 of 39
Where do action potentials occur?
along all unmyelinated neurones
13 of 39
What is meant by a myelinated neurone?
sensory and motor neurones are protected by schwann cells, makes up myelin which acts as an insulator// here AP transmission must occur in the Nodes of Ranvier
14 of 39
What is a myelin sheath?
insulating layer of fatty material which Na and K ions cannot pass through
15 of 39
How is an action potential transmitted in myelinated neurones?
myelin contains voltage gated K and Na ion channels// the action potential jumps from one node of ranvier to the next// myelinated neurones have a much faster transmission time than unmyelinated
16 of 39
What is a signal?
many successive impulses form a group called a volley - a group of volleys is a signal
17 of 39
What is the refractory period?
the time that must elapse after an initial stimulus has been set up an AP before a second stimulus can set up a second AP
18 of 39
describe the difference between refractory periods in myelinated and non-myelinated neurones
myelinated neurones the RF period is much smaller than that of a non// this allows a wide range of responses to be controlled
19 of 39
What is a threshold potential?
the p.d. across a membrane which if met or exceeded will trigger an AP
20 of 39
What is a generator potential?
caused by a slight depolarisation in the membrane from a small stimuli
21 of 39
what is an action potential?
depolarisation of the Smem where the inside is more positive than the outside, transmitted along a neurone
22 of 39
What is a resting potential?
the state of a neurone when it is not transmitting an AP// but is still actively transporting Na+ and K+ ions to maintain the p.d. of around -60mv
23 of 39
What is the transmission of an action potential called on myelinated neurones>
saltatory conduction - jumps from one to the next
24 of 39
Where are non-myelinated neurones used in the body?
coordinated body functions over short distances - less need for rapid transmission i.e. digestive system
25 of 39
what happens if a stimulus is too small?
threshold frequency will not be met - no AP
26 of 39
How can you determine the intensity of a stimulus?
by the frequency of the APs arriving - more APs generated
27 of 39
What is a Cholinergic synapse?
junction between two or more neurones// acetylcholine is the neurotransmitter
28 of 39
What is the function of a synapse?
allows neurones to communicate with each other
29 of 39
What is a presynaptic neurone?
ends in a synaptic knob // specialised bulge in a neurone
30 of 39
Describe the function and characteristics of the presynaptic neurone
contains many mitochondria for ATP // smooth ER /// vesicles containing acetylcholine // voltage gated Ca2+ ions in the presynaptic mem
31 of 39
What is the purpose of a postsynaptic neurone?
found on a neurone or effector - to either transmit another AP or bring about a response
32 of 39
Describe the characteristics of the postsynaptic neurone
specialist Na+ ion channels // channels with receptor to Ach, open when binds // only on postsynaptic to APs can only be in one direction
33 of 39
What is the purpose of several presynaptic neurones converging to one postsynaptic neurone?
signals from different parts of the nervous system converge for one response // danger
34 of 39
What is the purpose of one presynaptic neurone diverging to several postsynaptic neurones?
produces several responses // i.e. in a reflex when one neurone informs effector and the other the brain
35 of 39
How are low level signal filtered out?
several generator potentials required for an AP// if only a few arrive at the synapse less likely to be transmitted because its likely to be unimportant
36 of 39
What is summation?
persistent low level signals are amplified by adding together the many postsynaptic generator potentials to produce one full AP
37 of 39
What is acclimatisation?
synapse may run out of Ach if there is repeated stimulation // prevents potentially damaging an effector my overstimulation // persistent background noise not responded to after time
38 of 39
How do synapses and the brain work together?
synapses create specific pathways so that the brain knows where an AP originated
39 of 39
Other cards in this set
Card 2
Front
What are sensory receptors?
Back
transducers - convert different forms of energy into nerve impulses
Card 3
Front
Give some examples of sensory receptors
Back
Card 4
Front
What do sensory neurons do?
Back
Card 5
Front
What does the Central nervous system consist of?
Back
Related discussions on The Student Room
Similar Bengali resources:
1.0 / 5 based on 1 rating
1.0 / 5 based on 1 rating
5.0 / 5 based on 2 ratings
2.0 / 5 based on 1 rating
0.0 / 5
0.0 / 5
0.0 / 5
0.0 / 5
Comments
No comments have yet been made