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Z YEAR 1 BRS > Cells of Nervous System and Neuromuscular Junction > Flashcards

Cells of Nervous System and Neuromuscular Junction Flashcards

1
Q

What are the surfaces on the cerebral hemispheres?

A

Highly convoluted surface of ridges -> gyri & valleys -> sulci

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2
Q

What are the 4 functional regions in the cerebral hemispheres?

A

frontal, parietal, temporal and occipital

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3
Q

What does the brainstem consist of?

A

-midbrain, pons and medulla -Target or source of all cranial nerves and has numerous important functions

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4
Q

Describe the cerebellum

A

•Hindbrain structure attached to brainstem •Important role in motor coordination, balance & posture

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5
Q

What is the spinal cord?

A
  • Extends down from medulla:
  • Conduit for neural transmission
  • Co-ordinates some reflex actions
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6
Q

What are the different neurones? Describe them

A
  1. Unipolar: 1 axonal projection
  2. Psuedo-unipolar: Single axonal projection that divides into two
  3. Bipolar: 2 projections from cell body
  4. Multipolar: Numerous projections from cell body 
•Pyramidal cells: ‘pyramid’ shaped cell body

•Purkinje cells: GABA neurons found in the cerebellum •Golgi cells: GABA neurons found in the cerebellum

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7
Q

Describe neurones

A
  • Excitable cells of CNS
  • Heterogeneous morphology
  • Non-dividing cells
  • Share common features:
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8
Q

Describe the Soma (cell body, perikaryon) of the neurone

A
  • Contains nucleus & ribosomes
  • Neurofilaments -> structure & transport
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9
Q

Describe the axon

A
  • Long process (aka nerve fibre) - originates from soma at axon hillock
  • Can branch off into ‘collaterals’
  • Usually covered in myelin
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10
Q

Describe dendrites

A

•Highly branched cell body - NOT covered in myelin •Receive signals from other neurons

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11
Q

Describe astrocytes

A
  • Most abundant cell type within CNS
  • Able to proliferate
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12
Q

What is the fucntion of astrocytes?

A
  • Structural cells: blood-brain barrier
  • Cell repair: synthesise neurotrophic factors
  • Homeostasis: neurotransmitter removal & reuptake
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13
Q

Describe oligodenocyte

A
  • Variable morphology & function
  • Numerous projections that form internodes of myelin
  • One oligodendrocyte to myelinates many axons
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14
Q

Descrieb Shwaan cells

A
  • Produce myelin for peripheral nerves
  • One Schwann cell to myelinates one axon segment
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15
Q

What are microglial cells?

A
  • Specialised cells - similar to macrophages
  • Perform immune functions in CNS
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16
Q

What are ependymal cell?

A
  • Epithelial cells - line fluid filled ventricles
  • Regulate production & movement of cerebrospinal fluid (CSF)
17
Q

Summarise the other cells in the CNS Anatomy

A

1.Neuron

  • Excitable cells of CNS
  • Responsible for electrical transmission

2.Oligodendrocyte

•Glial cell - produces myelin

3.Astrocyte

•Most abundant cell type in CNS

4.Microglia

•Neuronal macrophages

18
Q

What are the 4 major physciological ions in RMP?

A

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

19
Q

What is the distributioin of ions in the cell like and what does this cause?

A
  • Cell membranes - impermeable to these ions -> transportation regulated by channels & pumps
  • This causes an uneven ion distribution:
  • High extracellular - Na+ & Cl-
  • Low extracellular - K+
  • High concentration gradient for Ca2+
  • Difference in concentration -> creates a potential difference across the membrane
20
Q

What is the charge like the neuronal cells?

A
  • Neuronal cells -
  • Negative charge inside compared to outside
  • RMP of between -40 to -90mV

•Positive and negative charges are concentrated around the membrane

21
Q

What happens at RMP?

A

•Voltage-gated Na+ channels (VGSCs) & voltage-gated K+ channels (VGKCs) are closed

1) Membrane depolarisation - opening of VGSC to Na+ influx to further depolarisation
2) VGKCs opens at a slower rate and causes tp efflux of K+ from cell to membrane repolarisation

22
Q

What happens during an action potential?

A

•AP leaves Na+ & K+ imbalance to need to be restored
•Na+-K+-ATPase (pump) restores the ion gradients
1)Resting configuration - Na+ enters vestibule & upon phosphorylation to ions are transported through protein
2)Active configuration - Na+ removed from cell to K+ enters the vestibule
3)Pump returns to resting configuration to K+ is transported back into the cell

23
Q

Describe salatory conduction

A
  • AP spreads along the axon by ‘cable transmission’
  • Myelin prevents AP spreading because it has - high resistance & low capacitance
  • Nodes of Ranvier - Small gaps of myelin intermittently along axon:
  • AP ‘jumps’ between nodes - saltatory conduction
  • AP is unable to ‘jump’ across the gap at the axon termina
24
Q

What if the first step in the neurotransmission in a synapse?

A

1.Propagation of the action potential (AP)

  • AP is propagated by VGSCs opening
  • Na+ influx -> membrane depolarisation -> AP ‘moves along’ neuron
  • VGKC opening -> K+ efflux -> repolarisation
25
Q

What is the second step in neurotranmission in a synapse?

A

2.Neurotransmitter (NT) release from vesicles
•AP opens voltage-gated Ca2+ channels at presynaptic terminal
•Ca2+ influx -> vesicle exocytosis

26
Q

What is the third step in neurotranmission in a synapse?

A

3.Activation of postsynaptic receptors
•NT binds to receptors on post-synaptic membrane
•Receptors modulate post-synaptic activity

27
Q

What is the fourth step of neurotransmission in a synpase?

A

4.Neurotransmitter reuptake
•NT dissociates from receptor and can be:
•Metabolised by enzymes in synaptic cleft
•Recycled by transporter proteins

28
Q

What are the different types of communication in nerve cells in post-synpatic cell?

A

Communication between nerve cells
•Autocrine & paracrine: neurotransmitter release

29
Q

What are the different types of synpatic organisation in post-synaptic cell?

A

A.Axodendritic synapse: connection between presynaptic terminal -> neuronal dendrite
B.Axosomatic synapse: connection between presynaptic terminal -> neuronal soma
C.Axoaxonic synapse: connection between presynaptic terminal -> neuronal axon

30
Q

Whta is a neuromusculasr junction?

A

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

31
Q

What is the communcation like between nerve and effector cells?

A

•Paracrine: neurotransmitter release

32
Q

What happens at neuromusuclar junction?

A
  • Action potential propagated along axon (Na+ & K+) -> Ca2+ entry at presynaptic terminal
  • Ca2+ entry -> acetylcholine (ACh) release into synpase
  • ACh binds to nicotinic ACh receptors (nAChR) on skeletal muscle -> change in end-plate potential (EPP)
  • Miniature EPP: quantal ACh release
33
Q

Describe the sarcolemma

A
  • The skeletal muscle membrane: nAChR activation -> depolarisation – action potential (AP)
  • T-tubules: continuous with sarcolemma & closely connected to sarcoplasmic reticulum
  • AP travels through T-tubules
34
Q

Describe the sarcoplasmic reticulum

A
  • Location: surrounds myofibrils – contractile units of muscle
  • Function: Ca2+ storage -> Ca2+ release following sarcolemma depolarisation
  • Effect: Ca2+ -> myofibril contraction & muscle contraction
35
Q

What is botulism (disorder of neuromuscular junction)?

A

•Botulinum toxin (BTx): irreversible disrupts stimulation-induced ACh release from presynaptic nerve terminal

36
Q

What is Myasthenia Gravis (disorder of neuromusuclar junction)?

A
  • Autoimmune disorder: antibodies directed against ACh receptor
  • Cause fatigable weakness (i.e. becomes more pronounced with repetitive use)
37
Q

What is Lambert-Eaton myastenic syndrome (LEMS) (disorder of neuromsuuclar junction)?

A

•Autoimmune disorder: antibodies directed against VGCC

Z YEAR 1 BRS (9 decks)

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