Cells of the neuromuscular junction

Question 1

• What are the 4 different possible morphologies of neurons?

Answer 1

Unipolar

Psuedo-unipolar

Bipolar

Multipolar

     - Pyramidal cells
     - Purkinje cells (GABA neurones found in the cerebellum)
     - Golgi cells (GABA neurones found in the cerebellum)

Question 2

• What is the most abundant cell type in the CNS?

- What is an astrocyte and what is its function?

Answer 2

Astrocyte

structural cell, play a role in cell repair, synapse formation, neuronal maturation and plasticity

Question 3

• What are the functions of Oligodendrocytes and Schwann cells?
• What is the difference between Oligodendrocytes and Schwann cell?

Answer 3

Myelin producing cells

Oligodendrocytes work in CNS

Schwann cells work in the PNS

Each Oligodendrocyte is capable of myelinating a number of axons

A Schwann cell only myelinates a single axon segment

Question 4

• What is a Microglial cell?

- What is an Ependymal cell?

Answer 4

Neuronal macrophages- Performs immune functions in CNS

Epithelial cells that line the fluid-filled ventricles regulating the production and movement of cerebrospinal fluid

Question 5

what is a neuron?

what are glial cells?

Answer 5

excitable cells of the CNS
responsible for receiving and transmitting information in the form of electrical signals

group of cells that provide physical and metabolic support to neurons- eg astrocyte, ependyma, microglia, oligodendrocyte

Question 6

• Explain how the ions are involved in the generation of an action potential?
• Explain how the ions are involved in the restoration of the resting membrane potential?

Answer 6

Influx of Na+ via voltage gated sodium ion channels (VGSC) leads to further depolarisation

Voltage gated potassium ion channels (VGKC) opens at slower rate, leading to efflux of K+ from cell which repolarises the membrane

Question 7

• How does the Na+/K+ ATPase involved in restoring the ion gradients? (two stages)

Answer 7

Resting configuration - Na+ enters vestibule & upon phosphorylation, ions are transported through the protein against conc. gradient

Active configuration - Na+ removed from cell and K+ enters the vestibule against conc. gradient. The pump returns to resting configuration and K+ is transported back into cell

Question 8

• What is the process by which AP spreads along the axon also known as?
• What is meant by saltatory conduction?

Answer 8

Cable transmission

AP 'jumps' between nodes to get to pre-synaptic terminal faster

Question 9

• What is the function of Myelin in the travelling of the AP?
• What are the Nodes of Ranvier?

Answer 9

Prevents AP spreading because it has high resistance and low capacitance

Small gaps of no myelin intermittently along the axon

Question 10

• Where is the sarcoplasmic reticulum in relation to the myofibrils?
• What is the function of the sarcoplasmic reticulum and what effect does it have?

Answer 10

Surrounding myofibrils

Ca2+ storage → Ca2+ release following sarcolemma depolarisation

Ca2+ → myofibril contraction & muscle contraction

Question 11

• What is Myasthenia Gravis and what does it cause?

Answer 11

Autoimmune disorder: antibodies directed against ACh receptor

Causes fatigable weakness (becomes more pronounced with repetitive use)

Question 12

what does passive propagation result from

Answer 12

Passive (graded) propagation results from a local change in ionic conductance (e.g. synaptic or sensory that produces a local current) that spreads along a stretch of membrane becoming exponentially smaller- charge leaks from the neuron