Neurons and Networks

Question 1

Physiological properties of low threshold spiking cells

Answer 1

• lower frequency firing pattern
• adaptation
• fires spikes at the start of the current pulse
• lower current stimulation required

Question 2

Physiological properties of fast spiking cells

Answer 2

• high frequency firing pattern
• no adaptation
• fires spikes at the end of the current pulse
• higher current stimulation required

Question 3

Similarities between LTS and FS cells

Answer 3

• occupy same layers in cortex
• both interneurons releasing GABA
• stimulation of one results in hyperpolarissation of the other
• electrically coupled (RS cells are not)

Question 4

FS cells innervate (release GABA) onto

Answer 4

• other FS cells
• RS cells
• LTS cells

Question 5

LTS cells innervate (release GABA) onto

Answer 5

• FS cells
• RS cells
• not LTS!!

Question 6

RS cells innervate (release glutamate) onto

Answer 6

• LTS cells
• RS cells
• FS cells

Question 7

Synchronicity of LTS cells

Answer 7

• ACPD stimulation activates LTS cells, causing synchronous IPSPs in FS cells
• measure synchrony via cross-correlations
• subthreshold depolarisations in LTS cells reflect synchronous IPSPs in FS cells
• consequently, all RS cells are inhibited synchronously

Question 8

Granule cells

Answer 8

• cerebellum
• release glutamate

Question 9

Purkinje cells

Answer 9

• cerebellar cortex
• release GABA

Question 10

Inferior Olivary cell

Answer 10

• medulla oblongata
• release glutamate

Question 11

Events necessary for sensation to arise

Answer 11

1. stimulation of sensory receptor
2. transduction of the stimulus
3. generation of nerve impulses
4. integration of sensory input

Question 12

Define receptor potentials

Answer 12

sensory receptors that are separate cells produce graded potentials

Question 13

Define generator potential

Answer 13

when large enough to reach threshold, it triggers one or more nerve impulses in the axon of a first-order sensory neuron

Question 14

Mechanoreceptors

Answer 14

sensitive to deformation

Question 15

Thermoreceptors

Answer 15

detect changes in temperature

Question 16

Nociceptors

Answer 16

respond to painful stimuli

Question 17

Photoreceptors

Answer 17

activated by photons of light

Question 18

Chemoreceptors

Answer 18

detect chemicals in mouth, nose and body fluids

Question 19

Osmoreceptors

Answer 19

detect the osmotic pressure of body fluids

Question 20

Sensory unit

Answer 20

primary sensory neuron with all recceptor endings or associated sensory receptor cells

Question 21

Receptive field

Answer 21

• area of the body surface in which a stimulus leads to activation of the sensory unit
• adding inhibitory interneurons into the circuit can reduce the size of the RF or complicate its response

Question 22

Two main functions of sensory system

Answer 22

• detection of a signal
• estimation (discrimination of aspects)

Question 23

What must be estimated from the input

Answer 23

• modality
• intensity
• duration/frequency
• location

Question 24

How is modality represented in the brain

Answer 24

the most basic mechanism for identifying the nature of a sensory input is via labelled lines

Question 25

Coding for stimulus duration

Answer 25

- coded by interspike interval - adaptation = decrease in frequency of APs with sustained stimulus

Question 26

Stimulus intensity

Answer 26

- larger receptor potential - activation of more sensory receptors of sensory unit - activation of sensory receptors on neighbouring sensory units - coded for by total response generated in sensory organ

Question 27

Stimulus localisation

Answer 27

topographic mapping -> points close together on the sensory surface are represented closer in the brain

Question 28

Lateral inhibition

Answer 28

- exaggerates the difference in stimulus intensity detected by adjacent neurons - aids with localisation - central neuron forms feed-forward inhibition - release of GABA inhibits lateral - signal is strongest at point of stimulus