Cells and communication in the nervous system

Question 1

What are the functions of the nervous system?

Answer 1

Sensation, integration and activation

Question 2

What is sensation?

Answer 2

Receptors in skin and organs respond to changes in the internal or external environment and provide information to the central nervous system (CNS)§

Question 3

What is integration?

Answer 3

Input from the internal and external environment is processed and integrated by the CNS. Decisions are made and appropriate responses formulated

Question 4

What is activation?

Answer 4

Appropriate response forwarded to the appropriate muscles and glands (muscle contractions and secretions)

Question 5

Give some mechanisms for nervous system dysfunction

Answer 5

• Damage by trauma or disease
• Neurons lose ability to produce transmitters
• Neurons over- or under-produce transmitters
• Neurons fail to recognise transmitters
• Effector organs fail to respond

Question 6

How can dysfunction of the nervous system manifest as?

Answer 6

• Loss: of sensation or function
• Gain: appearance of new feature
• Change: alteration in behaviour/personality or perception

Question 7

What are the 2 types of neurons?

Answer 7

Principal cells and interneurons

Question 8

Name the 5 types of glial cells

Answer 8

Astrocytes, ependymal cells, microglia, oligodendroglia, Schwann cells. A E I O (and Schwann) Vowel frequency in each cell type to help remember.

Question 9

What are astrocytes?

Answer 9

star-shaped cells which form a bridge between the neuron and blood vessels​

Question 10

What are ependymal cells?

Answer 10

simple, ciliated, cuboidal cells that form the lining of the ventricular system

Question 11

What are microglia?

Answer 11

small glial cells, activated by trauma​. Immune response.

Question 12

What are oligodendroglia?

Answer 12

myelin producing cells, found in the CNS. Feet project and wrap many neurons

Question 13

What are Schwann cells?

Answer 13

myelin producing cells, found in the PNS. One cell wraps one neuron.​

Question 14

What is the purpose of myelination?

Answer 14

Insulation, development (Not complete at birth), speeds communication, saltatory conduction

Question 15

Name some disorders of myelination

Answer 15

Multiple Sclerosis (affects CNS); Guillain Barre (affects PNS)

Question 16

Describe a chemical synapse

Answer 16

• Fast transmission (slower cell-cell, but can cope with higher. frequency of activity)
• Vesicles released from presynaptic terminal
• Act on receptors in postsynaptic terminal
• Major drug target

Question 17

Describe an electrical synapse

Answer 17

• Slower transmission (faster cell-cell, but more effective at lower frequencies)
• Gap junctions
• Small molecules and current
• ‘low-pass filter’
• Synchrony
• Up and coming drug target

Question 18

Describe communication at the neuromuscular junction

Answer 18

• Action potentials trigger the exocytosis of acetylcholine (ACh) from the synaptic terminal​
• ACh crosses the cleft​
• Acts on (nicotinic) cholinergic receptors in the motor end plate​
• Initiates muscle contraction​
• Impulse carried through muscle via T-tubules and sarcoplasmic reticulum

Question 19

What is myasthenia gravis?

Answer 19

autoimmune disease affecting the NMJ. Circulating antibodies block Ach receptors, slowing muscle activity and reducing tone.

Question 20

Describe the role of neurotransmitters

Answer 20

Used by neurons for rapid cell-cell communication​

• Stored in vesicles in the presynaptic terminal​
• Released when the terminal is depolarised during an AP​
• Pass across the synaptic cleft​
• Activate receptors on the postsynaptic terminal​
• Binds to receptor

Question 21

Describe neuromodulators

Answer 21

• Found in vesicles (or not), co-localised with NT​
• Act on receptors or membranes to indirectly alter neuronal activity​
• Changing sensitivity or kinetics of NT receptor ​
• Also act on glial cells

Question 22

What are inotropic receptors?

Answer 22

Linked to ion channels

Question 23

What are metabotropic receptors?

Answer 23

GPCRs

Question 24

What are specialised receptors?

Answer 24

General sensation and sensory organs. Developed to respond to particular stimuli. Transduce physical to electrical activity.

Question 25

What are the 4 main types of cutaneous specialised receptors?

Answer 25

• Mechanoceptors – detect tactile sensation (touch, pressure)​
• Thermoceptors – detect temperature changes​
• Nociceptors – detect painful/noxious stimuli​
• Proprioceptors – detect changes in head and body position

Question 26

What is the major excitatory transmitter? What is the major inhibitory neurotransmitter?

Answer 26

Excitatory - Glutamate

Inhibitory - GABA

Question 27

What is direct inhibition?

Answer 27

Excitatory neurons have regular firing in absence of inhibition​. Inhibitory input sculpts this firing producing patterns of activity (coding). Coding carries the information and can be read by the brain, like morse code. Some drugs that increase firing can lead to loss of coding, and psychological side effects

Question 28

What is lateral inhibition?

Answer 28

Activation of excitatory cells also activates associated inhibitory cells​.
Inhibition acts on neighbouring cells to reduce activity – allows brain to pinpoint where signal is coming from​.
Strengthens response of cell directly stimulated​.
Seen in sensory pathways:​
Vision​, touch​, olfaction

Question 29

What is disinhibition?

Answer 29

Two negative make a positive. Activation of inhibitory circuit leads to excitation. Important in basal ganglia.

Question 30

What is synchrony?

Answer 30

Co-ordinates activity. cell-cell via gap junctions. Pacemaker cells, like heart. Investigated using electroencephalography (EEG).
Synchrony changes strength at network level!

Question 31

What is plasticity?

Answer 31

Up- or down-regulation of synaptic strength. LTP and LTD. Synaptic morphology. Metabolic changes. Subunit changes.
Plasticity changes strength at neuronal level!