Neurotransmitters

Question 1

What is the magnitude that all action potentials have?

Answer 1

+40mV

Question 2

What is the main role of synapses?

Answer 2

connect 2 neurones together so that a signal can be passed from one to another, also perform other functions

Question 3

What is summation?

Answer 3

the way that several small potential changes can combine to produce one larger change in potential difference across the membrane

Question 4

What is useful when several different stimuli are warning us of danger?

Answer 4

several presynaptic neurones converge to one postsynaptic neurone, allow signals from different parts of the nervous system to create same response

Question 5

What does one presynaptic neurone diverging to several postsynaptic neurones allow?

Answer 5

one signal to be transmitted to several parts of nervous system, useful in reflex arc, one postsynaptic neurone elicits response while another informs brain

Question 6

How do synapses ensure that action potentials are only transmitted in correct direction?

Answer 6

only presynaptic knob contains vesicles of acetylcholine

Question 7

How do synapses filter out unwanted signals?

Answer 7

if low level stimulus creates an action potential in presynaptic neurone it is unlikely to pass across synapse to next neurone because several vesicles of acetylcholine must be released to create action potential in post synaptic neurone

Question 8

What is acclimatisation?

Answer 8

after repeated stimulation a synapse may run out of vesicles containing transmitter, synapse is fatigued, so nervous system no longer responds to stimulus

Question 9

How can low level signals be amplified?

Answer 9

by summation, if low level stimulus persistent will generate several successive action potentials in presynaptic neurone, release of many vesicles over short period enables postsynaptic generator potentials to combine = action potential

Question 10

What is the creation of specific pathways in the nervous system thought to be the basis of?

Answer 10

conscious thought and memory

Question 11

What are the differences between temporal and spatial summation?

Answer 11

temporal: several small action potentials from one presynaptic neurone, spatial: several presynaptic neurones contribute to action potential in postsynaptic neurone

Question 12

What happens when a stimulus is of higher intensity?

Answer 12

sensory receptor produces more generator potentials, cause more frequent action potentials in sensory neurone, then causes more vesicle release and higher AP frequency in postsynaptic neurone

Question 13

How does our brain determine the intensity of a stimulus?

Answer 13

frequency of signals, higher = more intense stimulus

Question 14

How many of the peripheral neurones in vertebrates are myelinated?

Answer 14

about 1/3

Question 15

What does the myelin sheath actually consist of?

Answer 15

cells wrapped around neurone, several layers of membrane and thin cytoplasm

Question 16

Where are the nodes of Ranvier?

Answer 16

at intervals of 1-3mm along neurone, each node is 2-3um long

Question 17

How are non-myelinated neurones associated with Schwann cells?

Answer 17

several neurones may be enshrouded in one loosely wrapped Schwann cell, action potential moves in wave not jumps

Question 18

How fast can non-myelinated neurones transmit action potentials?

Answer 18

2-20 ms-1

Question 19

Where do myelinated neurones carry signals?

Answer 19

from sensory receptors to CNS and from CNS to effectors, over long distances, longest in human can be 1m

Question 20

What are non-myelinated neurones used for in the body?

Answer 20

carry signals over short distance, coordinate body functions like breathing and action of digestive system (don’t need increased speed of transmission)