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PHRM 100 – APPP > APPP 02: Gross Anatomy of the CNS – Gross Anatomy and Cellular Anatomy > Flashcards

APPP 02: Gross Anatomy of the CNS – Gross Anatomy and Cellular Anatomy Flashcards

1
Q

What are the major cell types of the CNS? (3)

A
  • neurons
  • glial cells
  • cells of the blood brain barrier (BBB)
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2
Q

What is the basic unit of the nervous system?

A

nerve cell (neuron)

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3
Q

Describe the structure of nerve cells (neurons).

A
  • cell body: contains nucleus and cytoplasm, site of transcription and translation
  • dendrites: (nerve fibre) branched extensions of cell body, function to conduct impulses towards the cell
  • axon: (nerve fibre) one elongated extension, functions to send messages as electrical impulses
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4
Q

What are oligodendrocytes?

A

myelinating glia of the central nervous system

  • extend dendritic processes and wrap around the axon of nerve fibres to create myelin sheaths
  • myelin is unique among plasma membrane equivalents in its usually high lipid content (around 70%)
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5
Q

What is the function of myelin?

A

insulates and supports CNS axons

  • insulation increases the speed of nerve conduction
  • results in the accumulation of voltage-gated Na+ channels at the nodes of Ranvier
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6
Q

What are nodes of Ranvier?

A

gaps on the axon in between the myelin sheaths

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7
Q

Defects in myelination and myelin structure have been observed in what population?

A

adults exposed to cocaine, cannabinoids, alcohol, methamphetamines

  • affects nerve conductivity
  • usually reversible, but depends on the length of drug use
  • high dose of cannabinoids deteriorates myelination (causes inflammation), but low dose supports myelination
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8
Q

What is multiple sclerosis (MS)?

A

immune-mediated destruction of myelin that results in interrupted electrical nerve signals

  • the most common demyelinating disease of the CNS
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9
Q

What are the symptoms of multiple sclerosis (MS)?

A
  • numbness
  • weakness
  • cognitive difficulties
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10
Q

What is the therapy for multiple sclerosis (MS)?

A

aimed at slowing disease progression and improving quality of life

  • high-dose corticosteroids are used to dampen inflammation
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11
Q

What are the 3 most common neuron structures?

A
  • multipolar neuron
  • bipolar neuron
  • pseudounipolar neuron
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12
Q

What are multipolar neurons?

A

characterized by one axon and many dendrites that can originate from different regions of the cell body

  • vary greatly in size, shape, and complexity of their dendritic tree
  • the most common type of neuron in the central nervous system – ie. motor neurons
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13
Q

What are bipolar neurons?

A

two processes – one axon, one dendrite

  • dendrite that receives signals usually from the periphery and an axon that propagates the signal to the central nervous system
  • found in sensory organs – ie. retina, olfactory epithelium, auditory system
  • least common type of neuron
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14
Q

What are pseudounipolar neurons?

A

variations of bipolar neurons – have two processes which fuse during their development into one short common axon

  • axon splits into one branch that terminates in the periphery while the second branch terminates in the spinal cord – this way, stimuli from the periphery bypass the cell body and reach the axon terminal without delay
  • found in sensory ganglion of cranial and spinal nerves
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15
Q

What are the 3 classifications of neurons?

A

(based on function)

  • sensory neurons
  • motor neurons
  • interneurons
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16
Q

What is the function of sensory neurons?

A

convey signals from sensory receptors to the CNS via afferent nerves

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17
Q

What is the function of motor neurons?

A

convey information from CNS or ganglia to effector cells via efferent nerves

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18
Q

What is the function of interneurons?

A

form a communicating network between sensory and motor neurons

  • make up > 99.9% of all neurons
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19
Q

Briefly describe the flow of information through neurons.

A

communication between neurons in the CNS occur through synapses

  • dendrites collect
  • cell body integrates
  • axon passes
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20
Q

What are the 3 main types of ion channels and receptors that control synaptic transmission?

A
  • voltage-gated ion channel
  • ligand-gated ion channel
  • metabotropic receptor
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21
Q

What are voltage-gated channels?

A
  • respond to changes in membrane potential
  • directly opens ion channels
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22
Q

What are ligand-gated channels?

A
  • respond to neurotransmitters
  • directly opens ion channels
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23
Q

What are metabotropic receptors?

A
  • respond to neurotransmitters
  • indirectly opens ion channels
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24
Q

Describe the membrane potential at resting state of a neuron.

A
  • all voltage-gated Na+ channels and most voltage-gated K+ channels closed
  • resting membrane potential: -70 mV
  • Na+/K+ transporter pumps K+ ions into the cell and Na+ ions out
  • inside net negative
  • outside net positive
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25
Q

How does an action potential get generated?

A
  • ligands bind receptors (ligand-gated ion channel or metabotropic receptor)
  • changes to membrane potential as channels open
  • when net charge increases to -55 mV, this sensitizes Na+ voltage-gated ion channels
  • concentration of Na+ channels at axon hillock initiates action potential
  • depolarization spreads down the axon, repolarization follows
  • depolarization of presynaptic terminal opens Ca2+ channels, resulting in neurotransmitter release
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26
Q

How do voltage-gated Na+ ion channels work?

A
  • open at -55 mV
  • inactivated at +40 mV
  • after inactivation, it takes time for the protein to return to resting state (unavailable for reactivation)
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27
Q

How do voltage-gated K+ ion channels work?

A
  • slow to open
  • once open, K+ flows out
  • causes hyperpolarization
  • occurs during repolarization stage
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28
Q

What do Na+/K+ pumps do?

A

active transport ions to maintain resting levels

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29
Q

How does synaptic transmission occur?

A
  • Ca2+ binds to specific proteins (SNARE proteins), which triggers the complete fusion of the vesicle with the target membrane
  • this results in neurotransmitter release from vesicles at the terminal bouton into the synaptic cleft, and either activation or inhibition of the neuron
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30
Q

How does vesicle loading (monoamine/amino acid) occur?

A
  • carrier vesicles containing membrane transporter proteins are moved along microtubules
  • small molecule (ie. acetylcholine) produced in the cell are taken into vesicles
  • loaded vesicles are store at the presynaptic membrane
  • depolarization leads to docking of vesicles and exocytosis into the synapse
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31
Q

What is orexin?

A

one of the many neuropeptides functioning in the CNS

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32
Q

Neurotransmitters

Dopamine

  • mechanism
  • type
A
  • mechanism: inhibitory or excitatory
  • type: monoamine
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33
Q

Neurotransmitters

Norepinephrine

  • mechanism
  • type
A
  • mechanism: inhibitory or excitatory
  • type: monoamine
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34
Q

Neurotransmitters

Serotonin

  • mechanism
  • type
A
  • mechanism: inhibitory or excitatory
  • type: monoamine
35
Q

Neurotransmitters

Acetylcholine

  • mechanism
  • type
A
  • mechanism: inhibitory or excitatory
  • type: amino acid
36
Q

Neurotransmitters

GABA

  • mechanism
  • type
A
  • mechanism: inhibitory
  • type: amino acid
37
Q

Neurotransmitters

Glutamate

  • mechanism
  • type
A
  • mechanism: excitatory
  • type: amino acid
38
Q

Neurotransmitters

Glycine

  • mechanism
  • type
A
  • mechanism: inhibitory
  • type: amino acid
39
Q

Neurotransmitters

Histamine

  • mechanism
  • type
A
  • mechanism: inhibitory or excitatory
  • type: monoamine
40
Q

Neurotransmitters

Orexin

  • mechanism
  • type
A
  • mechanism: excitatory
  • type: neuropeptide
41
Q

What is the cerebrum?

A

forms the bulk of the brain

42
Q

Describe the structure of the cerebrum.

A
  • gyri (bumps) and sulci (grooves)
  • large sucli called the fissure
  • these ridges increase surface area
  • top layer is the cortex (cerebral cortex) – made up of grey matter
  • 4 lobes
43
Q

What are the 4 lobes of the cerebrum?

A
  • frontal
  • parietal
  • occipital
  • temporal
44
Q

What are the functions of the cerebrum?

A
  • perception
  • higher motor functions
  • cognition
  • memory
  • emotion
45
Q

What is the frontal lobe?

A
  • contains motor areas
  • controls intellectual activities, such as the ability to organize
  • controls personality, behaviour, and emotional control
46
Q

What is the parietal lobe?

A
  • contains somatosensory areas
  • controls the ability to read, write, and understand spatial relationships
47
Q

What is the temporal lobe?

A
  • contains auditory areas
  • controls memory, speech, and comprehension
48
Q

What is the occipital lobe?

A
  • contains visual areas
  • controls sight
49
Q

Describe the left and right hemispheres of the brain.

A
  • information is constantly being transferred between the hemispheres
  • hemispheres are connected by the corpus callosum
50
Q

What is the corpus callosum?

A

thick bundle of nerve fibres that ensures both sides of the brain can communicate and send signals to each other

  • approximately 300 million axons (nerve fibres) in an average corpus callosum
51
Q

What is the limbic system?

A

involved in behavioural and emotional responses

52
Q

What are the 3 major components of the limbic system?

A
  • hippocampus
  • amygdala
  • thalamus and a portion of they hypothalamus (mammillary body)
53
Q

What is the amygdala?

A

region of the brain primarily associated with emotional processes

  • involves fear and other emotions related to aversive (unpleasant) stimuli, fight or flight
  • now known to be involved in positive emotions elicited by appetitive (rewarding) stimuli
54
Q

What is the hippocampus?

A
  • responsible for processing long term memory, spatial navigation, regulation of hypothalamic function, and emotional responses
  • also responsible for the memory of the location of objects or people
55
Q

What is the thalamus?

A

acts as a relay between a variety of subcortical areas and the cerebral cortex

  • processing sensory and motor signals relay to cerebral cortex
  • regulating consciousness, sleep, and alertness
  • every sensory system (with the exception of the olfactory system) has a thalamic nucleus that receives sensory signals and sends them to the associated primary cortical area
56
Q

What does the hypothalamus do?

A

coordinates hormonal and behavioural circadian rhythms, complex patterns of neuroendocrine outputs, and homeostatic mechanisms

57
Q

What is the brainstem?

A

connects the brain to the spinal cord and the rest of the body

58
Q

What are the 3 parts of the brainstem?

A
  • midbrain
  • pons
  • medulla
59
Q

What is the midbrain responsible for?

A
  • auditory and visual signals
  • arousal
  • human consciousness
60
Q

What is the pons responsible for?

A

carries signals that control basic functions – ie. sleep

61
Q

What is the medulla responsible for?

A

control of involuntary functions – ie. breathing and heart rate

62
Q

What is the neocortex?

A

top layer of the cerebrum is the cortex – 6 layer structure called the neocortex

63
Q

What does the amygdala comprised of?

A

group of nuclei, or clusters of neurons

64
Q

How does the amygdala work?

A

uses interconnections with limbic and sensory cortex to form associations (ie. good or bad) and trigger appropriate responses

65
Q

What is the lateral nucelus (LA)?

A

the sensory interface of the amygdala – key site of plasticity

66
Q

What is the central nucleus (CE)?

A

viewed as the output region

67
Q

Amygdala

Describe a normal physiological state.

A
  • balance between glutamate and GABA maintains emotional responses at the level appropriate to external stimuli
  • regulated by activation of either glutamatergic neurons or GABAergic neurons
68
Q

What is the amygdala essential for?

A

the acquisition and storage of a memory of a conditioned experience and the expressed response

69
Q

Amygdala

What is fear conditioning?

A

procedure in which an emotionally neutral conditioned stimulus (CS) is presented in association with an aversive unconditioned stimulus (US)

  • auditory thalamic and prefrontal input pathways onto the LA can lead to fear memory formation
70
Q

What happens in the event of amygdala dysfunction?

A
  • anxiety disorders – ie. generalized anxiety disorder, phobias, panic attacks, PTSD, more
  • seizures
  • pain conditions – ie. neuropathic pain
71
Q

What is the treatment for amygdala dysfunction?

A
  • benzodiazepines, sedative/anti-anxiety drugs (valium) – enhances GABA-mediated synaptic inhibition and increases inhibitory signals to balance activation
  • serotonin levels are low in patients with emotional disorders – enhanced glutamatergic activity in the lateral nucleus (LA) of the amygdala and potentiated fear behaviours
  • SSRI – decreases the amygdala response to fear and other aversive stimuli
72
Q

What is the entorhinal cortex (EC)?

A

the major input and output structure of the hippocampal formation

  • spatial information relays through the medial entorhinal cortex (MEC)
  • non-spatial information relays through lateral entorhinal cortex (LEC)
73
Q

What type of neurons does LEC and MEC have?

A

cholinergic (acetylcholine)

74
Q

What are the 4 sections/sub-structure of the hippocampus?

A
  • MEC and LEC project into the hippocampus dentate gyrus (DG) region
  • project into the CA3 region (cornu ammonis)
  • CA3 projects to the CA2 and CA1
  • CA1 projects back to the entorhinal cortex
75
Q

What neurotransmitters do hippocampal neurons mainly release?

A

glutamate or GABA

76
Q

What is Alzheimer disease?

A

progressive neurodegenerative disease most often associated with memory deficits and cognitive decline

  • related to hippocampus
  • damage to cholinergic neurons
  • LEC and MEC contain cholinergic neurons
  • progressive loss of neurons
  • progressive memory impairment and cognitive dysfunction
77
Q

What is the damage to cholinergic neurons caused by in Alzheimer disease?

A
  • Aβ plaques (generated from amyloid precursor protein cleavage)
  • Tau protein aggregates
78
Q

Clinical diagnosis of Alzheimer disease is based on what symptoms?

A
  • memory impairment
  • irritability
  • paranoia and delusional thinking
  • *loss of sense of smell is often an early indicator
79
Q

What is the treatment for Alzheimer disease?

A
  • cholinesterase inhibitors
  • agents that block the breakdown of acetylcholine
80
Q

What essential role does the thalamus and brainstem play?

A

a role in sleep-wake regulation and role

81
Q

What is one of the most important functions of the hypothalamus?

A

linking the nervous system to the endocrine system via the pituitary gland

82
Q

What are some other functions of the hypothalamus?

A
  • temperature regulation
  • appetite
  • sexual dimorphism (difference between males/females during gestation)
83
Q

What can disorders of the hypothalamus result in?

A

appetite, temperature, and sleep disorders

84
Q

What is hypothalamic obesity?

A

can develop from major hypothalamic injury/damage affecting the centers of appetite regulation and energy balance

PHRM 100 – APPP (22 decks)

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