Lecture 1: Cells of the nervous system and neuromuscular junction

Question 1

What are the highly convoluted surface of ridges on the brain called?

Answer 1

Gyri

Question 2

What are the valleys in the brain called?

Answer 2

Sulci

Question 3

What are the 4 functional regions of the brain?

Answer 3

• frontal
• parietal
• temporal
• occipital

Question 4

What does the brainstem consist of?

Answer 4

• midbrain
• pons
• medulla
  NOTE: descending disorder

Question 5

What is the cerebellum?

Answer 5

Hindbrain structure attached to brainstem, important in motor coordination, fine movement, balance and posture

Question 6

What is the function of the spinal cord?

Answer 6

• conduit for neural transmission

- coordinates some reflex actions

Question 7

Where does the spinal cord extend down from?

Answer 7

The medulla

Question 8

What is a unipolar neuron?

Answer 8

1 axonal projection

Question 9

What is a pseudo-unipolar neuron?

Answer 9

single axonal projection that divides into 2

Question 10

What is a bipolar neuron?

Answer 10

2 projections from cell body but still only 1 axon

Question 11

What is a multipolar neuron?

Answer 11

numerous projections from cell body but still only 1 axon

Question 12

What are the different types of multipolar neurons?

Answer 12

• pyramidal: ‘pyramid’ shaped cell body
• purkinje cells: GABA neurons found in cerebellum
• Golgi cells: GABA neurons found in cerebellum

Question 13

What are the shared common features of neurons?

Answer 13

• Soma (cell body, perikaryon)
• Axon
• Dendrites

Question 14

What is the soma of a neuron?

Answer 14

Cell body that contains nucleus and ribosomes.

Neurofilaments for structure and support

Question 15

What is the axon of a neuron?

Answer 15

• long process (a.k.a nerve fibre) - originates from soma at axon hillock
• can branch off into ‘collaterals’
• usually covered in myelin

Question 16

What is the dendrite of a neuron?

Answer 16

• highly branched cell body, not covered in myelin

- branches receive signals from other neurons

Question 17

What is the most abundant cell type within the CNS?

Answer 17

Astrocytes

Question 18

What are astrocytes?

Answer 18

• able to proliferate
• structural cells: blood-brain barrier, keeping neurones in place
• cell repair: synthesis of neurotrophic factors, growth + maintenance
• homeostasis: neurotransmitter removal and reuptake

Question 19

What are oligodendrocytes?

Answer 19

• myelin-producing cells for CNS
• numerous projections that form internodes of myelin
• variable morphology and function

Question 20

How many axons can one oligodendrocyte myelinate?

Answer 20

Many axons

Question 21

What is a Schwann cell?

Answer 21

• myelin-producing cell for peripheral nerves

Question 22

How many axons can 1 Schwann cell myelinate?

Answer 22

1 cell myelinates one axon segment only

Question 23

What are microglial cells?

Answer 23

• specialised cell, similar to macrophages

- immune cells of CNS, perform immune functions

Question 24

What are ependymal cells?

Answer 24

• epithelial cells lining fluid-filled ventricles

- regulate production and movement of cerebrospinal fluid (CSF)

Question 25

What are glial cells?

Answer 25

The glial cells surround neurons and provide support for and insulation between them

Question 26

What cells are included within glial cells?

Answer 26

- astrocytes - oligodendrocytes - microglia - ependymal

Question 27

What are the 4 major physiological ions?

Answer 27

- potassium (K+) - sodium (Na+) - chloride (Cl-) - calcium (Ca2+)

Question 28

How is transportation of important ions regulated?

Answer 28

By channels and pumps because cell membrane is impermeable to these ions

Question 29

Which ions have a high extracellular concentration?

Answer 29

Na+ and Cl-

Question 30

Which ion has a low extracellular but high intracellular concentration?

Answer 30

K+

Question 31

Which ion has a high concentration gradient across the cell membrane?

Answer 31

Ca2+

Question 32

What creates the potential difference across the cell membrane?

Answer 32

the difference in ion concentrations

Question 33

What charge do neuronal cells have inside?

Answer 33

negative compared to outside

Question 34

What is the range of the resting membrane potential?

Answer 34

-40 to -90mV

Question 35

Where are the positive and negative charges concentrated?

Answer 35

Around the membrane

Question 36

What is the state of the ion channels at RMP?

Answer 36

voltage-gated Na+ and voltage -gated K+ channels are closed

Question 37

What happens at membrane depolarisation?

Answer 37

voltage-gated sodium channels open which leads to an influx of Na+ and further depolarisation

Question 38

What happens at membrane repolarisation?

Answer 38

voltage-gated potassium channels open at a slower rate and cause efflux of K+ from cell

Question 39

What does an action potential leave?

Answer 39

a sodium and potassium imbalance

Question 40

How is the Na+ and K+ imbalance restored?

Answer 40

Using Na+-K+-ATPase pump to restore ion gradients

Question 41

What is the resting configuration of Na+-K+-ATPase?

Answer 41

Na+ enters vestibule and upon phosphorylation ions are transported through protein

Question 42

What is the active configuration of Na+-K+-ATPase?

Answer 42

Na+ removed from cell, K+ enters vestibule

Question 43

What happens when the pump returns to resting configuration?

Answer 43

K+ is transported back into the cell

Question 44

What is saltatory conduction?

Answer 44

action potential jumps between nodes of Ranvier to speed up transmission

Question 45

How does myelin prevent action potential from spreading?

Answer 45

It has high resistance and low capacitance

Question 46

What are the nodes of Ranvier?

Answer 46

small gaps of myelin intermittently along axon

Question 47

Outline how a synapse works. (4 steps)

Answer 47

1) Propagation of the action potential (AP) - Na+ influx, AP moves along neuron, K+ efflux for repolarisation 2) Neurotransmitter release - AP opens voltage-gated Ca2+ channels at presynaptic terminal, Ca2+ influx leads to vesicle exocytosis 3) Activation of postsynaptic receptors - NT binds to receptors on post-synaptic membrane, receptors modulate post-synaptic activity 4) Neurotransmitter reuptake - NT dissociates from receptor and can be metabolised by enzymes in synaptic cleft or recycled y transporter proteins

Question 48

What type of communication occurs between nerve cells?

Answer 48

Autocrine and paracrine via neurotransmitter release

Question 49

What is an axodendritic synapse?

Answer 49

connection between presynaptic terminal to neuronal dendrite

Question 50

What is an axosomatic synapse?

Answer 50

connection between presynaptic terminal to neuronal soma

Question 51

What is an axoaxonic synapse?

Answer 51

connection between presynaptic terminal to neuronal axon

Question 52

What is the neuromuscular junction?

Answer 52

Specialised structure incorporating axon terminal and muscle membrane allowing unidirectional chemical communication between peripheral nerve and muscle

Question 53

What type of communication occurs between nerve and effector cells?

Answer 53

paracrine via neurotransmitter release

Question 54

What 4 steps happen at the neuromuscular junction?

Answer 54

1) AP propagated along axon --> Ca2+ entry at presynaptic terminal 2) Ca2+ entry leads to acetylcholine (ACh) release into synapse 3) ACh binds to nicotinic ACh receptors (nAChR) on skeletal muscle --> change in end plate potential (EPP) 4) 1 ACh vesicle (quantal ACh release) results in mini EPP so need summation of lots of mini EPPS for transmission

Question 55

What is the sarcolemma?

Answer 55

skeletal muscle membrane with nAChR receptors which when activated lead to depolarisation and so an action potential

Question 56

What are the T-tubules?

Answer 56

tubes that are continuous with sarcolemma & closely connected to sarcoplasmic reticulum

Question 57

Where does the AP travel through in skeletal muscle?

Answer 57

T-tubules

Question 58

Where is the sarcoplasmic reticulum?

Answer 58

surrounds myofibrils - contractile units of muscle

Question 59

What is the function of the sarcoplasmic reticulum?

Answer 59

Ca2+ storage - Ca2+ is released following sarcolemma depolarisation

Question 60

What is the effect of Ca2+ in skeletal muscle?

Answer 60

causes myofibril contraction and muscle contraction

Question 61

What are some disorders of the neuromuscular junction?

Answer 61

- botulism (botulinum toxin irreversibly disrupts stimulation-induced ACh release) - myasthenia gravis (MG): antibodies directed against ACh receptor, autoimmune - Lambert-eaton myastenic syndrome (LEMS): antibodies against VGCC, autoimmune