Nerve Conduction and excit

Question 1

describe the five factors in nervous communication

Answer 1

Sensor (Receptor/transducer for a specific stimulus); Stimulus (exceeds minimum threshold/energy); Conduction (Fast transmission of electrically isolated signal); Processing (interneurons enhance modify and relate signals); Contextual perception (signal reaches consciousness is moderated by context)

Question 2

what are the function units of communication in the nervous system?

Answer 2

Neurones

Question 3

Neurons at rest:

Answer 3

Have negative resting membrane potential; receive inputs which summate to change membrane potential transiently

Question 4

Neurons in action:

Answer 4

Have sufficient summated input to change membrane potential to more positive threshold levels; this triggers OUTPUT (the action potential)

Question 5

how to ions move across neuron membranes? Is it Active or passive?

Answer 5

Specific Transporter proteins (both active and passive; move ions Against their gradients); Ion channel proteins (always passive; allow ions to move with gradients

Question 6

Resting membrane potential is due to what enzyme? It is largely determined by what ion?

Answer 6

Na+-K+ ATPase pump; K+

Question 7

inputs to the neurons summate making it?

Answer 7

Inputs to neurons summate; making it MORE or LESS likely to produce an ACTION POTENTIAL

Question 8

Excitatory synaptic potentials ________ the resting membrane potential pushing the neuron ________ to the threshold

Answer 8

Excitatory synaptic potentials depolarize the resting membrane potential pushing the neuron closer to the threshold

Question 9

Inhibitory synaptic potentials ________ the resting membrane potential pushing the neuron ________ to the threshold

Answer 9

Inhibitory synaptic potentials hyperpolarize the resting membrane potential pushing the neuron away from the threshold

Question 10

Depolarizing the resting membrane potential occurs by?

Answer 10

Opening ion channels permeable to ions with Nernst potential +ve to Em

Question 11

Hyperpolarizing the resting membrane potential occurs by?

Answer 11

Opening ion channels permeable to ions with Nernst potential ?ve to Em

Question 12

ion channels can be opened by?

Answer 12

Membrane potential or direct electrical stimulation; Neurotransmitters; Mechanical/chemical forces

Question 13

What is the order of channels that open in an action positional?

Answer 13

once the threshold has been reached; voltage-sensitive Na+ ion channels rapidly open this leads to a strongly depolarizing the resting membrane positional; This channels automatically close; then the voltage-sensitive K+ channels slowly open strongly Hyperpolarizing the resting membrane positional

Question 14

describe the flow of an action potential

Answer 14

AP normally travel from soma to synaptic terminals at the end of the axon; this triggers the synaptic release of neurotransmitters which generate PSPs in target neurons or tissues

Question 15

what does the conduction velocity of an AP depend on?

Answer 15

Dependent on axon diameter and degree of myelination

Question 16

regular breaks in myelin allow what kind of conduction? What are these breaks called?

Answer 16

Saltatory Conduction of nerve impulse from node to node; Node of Ranvier

Question 17

myelin insulation allows?

Answer 17

Rapid passive spread of current within axon cytoplasm rather than leaking across axon membrane

Question 18

describe what happens to an AP as it spreads from a Node of Ranvier

Answer 18

Ap depolarization generated at single node spreads passively to adjacent membrane and decreases with distance from node

Question 19

Rate of spread depends on?

Answer 19

Rate of spread depends on axon diameter

Question 20

Voltage gated Na+ channels are concentrated where?

Answer 20

At the Axon Hillock

Question 21

how does the international association for the study of pain define pain?

Answer 21

an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage

Question 22

how did Margo (No Suggestions) describe pain?

Answer 22

Pain is whatever the experiencing person says it is existing whenever s/he says it does

Question 23

Describe Acute Pain

Answer 23

useful protective warning of external/internal environmental change which can harm body leading to adaptive avoidance behaviour

Question 24

Describe Chronic Pain

Answer 24

Maladaptive signal which can lead to long-term withdrawal and environmental indifference

Question 25

what are the four steps in sensing pain

Answer 25

Transduction (painful tissue stimuli transduced into electrical neural activity by peripheral nociceptors); Transmission (nociceptor afferents transmit pain signals to spinal cord and brain); Perception (pain perception involves central processing of nociceptor signals in spinal cord/brainstem/thalamus and cortex); Modulation (descending inhibitory and facilitator input from higher brain centres influences nociceptive transmission in spinal cord)

Question 26

what do Nociceptors respond to?

Answer 26

Nociceptors response to stimuli which damage tissue or could potentially damage tissue; this may be due to a direct response from a stimuli or factors released by the stimuli

Question 27

Where do nociceptors synapses? Where is the cell body

Answer 27

Axon synapses in the dorsal horn of the spinal cord or brainstem sensory nuclei; Cell body is in the Dorsal root or cranial nerve ganglia

Question 28

what are the four types of nociceptors? What do they respond to?

Answer 28

Noxious Mechanoreceptors: Respond only with strong mechanical stimulation and most effectively with sharp objects; Heat Nociceptors: Respond only when temp > 45 deg C; Polymodal nociceptors: respond equally to all mechanical temperature and chemical noxious stimuli; “Sleeping” nociceptors: Normally unresponsive unless tissue is inflamed or injured then show Polymodal responses

Question 29

Activation of nociceptive transducer receptor/ion channel complexes causes?

Answer 29

Generator potential: graded membrane depolarization with increasing intensity of noxious stimuli

Question 30

Nociceptor afferent firing rate is lower or higher than non-nociceptor sensory afferent firing rate?

Answer 30

Lower

Question 31

Many nociceptors show what kind of firing rate with prolonged noxious stimulus? This is know as?

Answer 31

Many nociceptors show slowing firing rate with prolonged noxious stimulus; know as adaptation

Question 32

Aps are due what ion channel in Nociceptors?

Answer 32

NA+

Question 33

spinal cord and cranial sensory nuclei exhibit layering these are know as what?

Answer 33

Laminae in the gray mater

Question 34

how do Nociceptors and somatosensory project into the grey matter?

Answer 34

Nociceptors and somatosensory receptors project into different Laminae

Question 35

where do fast pain nociceptors project to? What neurotransmitter do they use? What type of fibres are these?

Answer 35

Project into the Laminae I and they release Glutamate; these fibres are Alpha-alpha or type III fibres

Question 36

where do slow pain nociceptors project to? What neurotransmitter do they use? What type of fibres are these?

Answer 36

Project into the Laminae II and III and they release Glutamate and Substance p; these fibres are C fibres or type IV

Question 37

where do somatosensory receptors project to?

Answer 37

Project into the Laminae III and IV

Question 38

Describe the general flow of information once a painful stimulus is presented

Answer 38

Nociceptors in the affected area triggers the spinothalamic tract ->brainstem->midbrain-> Thalamus -> Limbic system and Cingulate cortex and Somatosensory cortex

Question 39

The descending pathways from the periaqueductal gray can?

Answer 39

Descending pathways from the periaqueductal gray and brainstem can inhibit spinal projection neurons receiving pain signals (Modulating the pain)

Question 40

what neurotransmitter do the descending pain pathways utilise to modulate pain? What type neuron is used? What other substance utilises this system?

Answer 40

Interneurons release enkephalin which reduces or blocks synaptic neurotransmitter release evoked by pain; Exogenous opiates

Question 41

Rank the nerve fibres in terms of Conduction velocity and Axon Diameter: are they the same and why?

Answer 41

Alpha-alpha > Alpha-Beta > Alpha-Gamma > Alpha-Delta > Beta > C; same with axon diameter because speed is directly related to diameter