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BISC276 > 2. Nervous System > Flashcards

2. Nervous System Flashcards

1
Q

What is the major function of the Nervous System?

A 
Control center (maintain homeostasis by coordination and communication)
e.g. collect information, process information, generate responses
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2
Q

What comprises the Central Nervous System (CNS)?

A

Brain, spinal cord

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3
Q

What comprises the Peripheral Nervous System (PNS)?

A

Composed of nerves that connect the brain or spinal cord with the body’s muscles, glands, and sense organs
e.g. cranial nerves, spinal nerves, ganglia

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4
Q

Organization: Afferent (sensory)

A

To CNS

e.g. somatic, visceral, special

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5
Q

Organization: Efferent (motor)

A

From CNS

  1. Somatic Nervous System
  2. Autonomic Nervous System
  3. Sympathetic Division
  4. Parasympathetic Division
    e. g. somatic motor, autonomic motor (sympathetic, parasympathetic, enteric)
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6
Q

What is the structure of a neuron?

A
  1. Cell body
  2. Dendrite
  3. Axon
  4. Initial segment
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7
Q

Myelinated axon

A
  • Schwann cell

- Node of Ranvier: speeds up the conduction velocity

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8
Q

What is the functional classification of neurons (3 classes)?

A
  1. Afferent neuron
  2. Efferent neuron
  3. Interneuron
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9
Q

What are the glial cells of CNS?

A
  1. Oligodendrocyte
  2. Astrocyte
  3. Microglia
  4. Ependymal cell
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10
Q

Neuron

A

The basic cell type of both systems; “nerve cells”

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11
Q

What the most numerous cells in the CNS?

A

Glial cells

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12
Q

Astrocytes

A

Support cells, control extracellular environment of neurons

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13
Q

Microglia

A

“Immune system” of CNS

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14
Q

Ependymal cells

A

Ciliated; involved with production of CSF and CSF movement

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15
Q

Oligodendrocytes

A

Form the myelin

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16
Q

What are examples of membrane potentials?

A
  1. Ohm’s Law
  2. Resting membrane potential
  3. Graded potentials
  4. Action potentials
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17
Q

What is Ohm’s Law?

A 
I = V/R
I = current: the movement of electrical charge
V = potential: voltage difference between two points
R = resistance: hindrance to movement through an opening or substance
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18
Q

How can electrical force increase?

A
  1. Increases with quantity of charge

2. Increases as distance of separation between charges decreases

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19
Q

What is the membrane potential?

A

An electrical “charge” (voltage difference) across the plasma membrane; charged positively outside in respect to inside of the cell

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20
Q

What is resting membrane potential?

A

The electrical “charge” (voltage difference) across the plasma membrane at resting (with no stimulus), which ranges from -40 to -90 mV

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21
Q

What is the Equilibrium Potential for K+?

A

The membrane potential at equilibrium due to K+ movement in a hypothetical situation
e.g. -90 mV

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22
Q

What is the Equilibrium Potential for Na+?

A

The membrane potential at equilibrium due to Na+ movement in a hypothetical situation
e.g. +60 mV

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23
Q

Why is the resting membrane potential close to EK+?

A

Because at resting, PK+ is high and PNa+ is low

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24
Q

Generation of Resting Membrane Potential

A
  1. Concentration difference (for Na+, K+) is set due to 3 Na+ to 2 K+ exchange ratio by sodium-potassium pump
  2. Permeability difference between Na+ and K+ (PK+ is much greater than PNa+)
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25
Q

If the K+ concentration in the extracellular fluid (ECF) is elevated, what would happen to the magnitude of the membrane potential?

A

Become less negative

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26
Q

If the membrane permeability to sodium ion (Na+) is elevated, what would happen to the magnitude of the membrane potential?

A

Become less negative

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27
Q

If a cell once viable is no longer able to generate ATPs (i.e. cell death), what would happen to the magnitude of the membrane potential?

A

Become less negative

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28
Q

What do some cells (nerve and muscle cells) have that are “gated” by signals?

A

Ion channels that are gated by signals

e.g. voltage current, chemicals, mechanical force (“excitability”)

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29
Q

What happens when these ion channels become “activated”/”excited”?

A

These ion channels open up, increasing the permeability of the membrane to a specific ion

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30
Q

After increasing membrane permeability, what will this ion movement result in?

A

Ion movement will result in a change in membrane potential

** Can be hyperpolarized (more negative) or depolarized (less negative), depending on the signal

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31
Q

Depolarization

A

The potential moving from RMP to less negative values

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32
Q

Repolarization

A

The potential moving back to RMP

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33
Q

Hyperpolarization

A

The potential moving away from RMP in a more negative direction

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34
Q

Graded Potential

A
  • Dissipates with distance
  • Either depolarized or hyperpolarized
  • Magnitude can vary (“graded”)
    e. g. receptor potential, pacemaker potential, synaptic potential
35
Q

Action Potential

A
  • A very large and rapid change in membrane potential that propagates along the full length of the axon
  • Has a threshold (all-or-none response)
  • Reversal of the polarity takes place
  • The mechanism the nervous system uses to communicate over long distances
36
Q

Explain the time course of an action potential (7 steps)

A
  1. Steady reasing membrane potential is near Ek, Pk is greater than PNa due to leak of K+ channels
  2. Local membrane is brought to threshold voltage by a depolarizing stimulus
  3. Current through opening voltage-gated Na+ channels rapidly depolarizes the membrane, causing more Na+ channels to open
  4. Inactivation of Na+ channels and delayed opening of voltage-gated K+ channels halts membrane depolarization
  5. Outward current through slowly closing voltage-gated K+ repolarizes the membrane back to a negative potential
  6. Persistent current through slowly closing voltage-gated K+ channel hyperpolarizes membrane toward Ek; Na+ channels return from inactivated state (without opening)
  7. Closure of voltage-gated K+ channels returns the membrane potential to its resting value
37
Q

Behavior of Voltage-Gated Ion Channels: Na+ Channel

A 
Fast responder (3 states)
e.g. closed, open, inactivated
38
Q

Behavior of Voltage-Gated Ion Channels: K+ Channel

A 
Slow responder (2 states)
e.g. closed open
39
Q

The sodium ion results in what state and why?

A

Influx of Na+ results in depolarization

40
Q

The potassium ion results in what state and why?

A

Efflux of K+ results in repolarization

41
Q

Refractory period

A

Refractoriness ensures the unidirectional transmission of active potential

42
Q

The mechanisms for “refractory” period are due to..

A

“Ion channel” behavior

43
Q

Why is saltatory conduction in myelinated axons have faster traveling of AP in comparison to unmyelinated axons?

A

Due to “jumping” effect from one node to the next which increases the direction of action potential propagation

44
Q

Graded Potential (overview)

A
  • Amplitude varies with size of initiating event
  • Can be summed
  • Has no threshold
  • Has no refractory period
  • Amplitude decreases with distance
  • Duration varies with initiating conditions
  • Can be a depolarization or hyperpolarization
  • Initiated by environmental stimulus (receptor) by neurotransmitter (synapse), or spontaneously
  • Mechanism depends on ligand-gated channels or other chemical or physical changes
45
Q

Action Potential (overview)

A
  • All-or-none: once membrane is depolarized to threshold, amplitude is independent of the size of the initiating event
  • Cannot be summed
  • Has a threshold that is usually about 15 mV depolarized relative to the resting potential
  • Has a refractory period
  • Is conducted without decrement; depolarization is amplified to a constant value at each point along the membrane
  • Duration is constant for a given cell type under constant conditions
  • Is only a depolarization
  • Initiated by a graded potential
  • Mechanism depends on voltage-gated channels
46
Q

How is the polarity across the membrane established? List the 3 main factors determining the polarity of cell membrane, and describe the role of each.

A
  1. Concentration difference for sodium and potassium across the membrane
  2. Greater flux of K+ out of the cell than Na+ into the cell due to a greater permeability to K+ than to Na+
  3. Na+/K+ -ATPase pump
47
Q

What is curare (alkaloid)?

A

A deadly arrowhead poison used by indigenous peoples of South America, causing death in human and animals by asphyxiation

48
Q

Explain the process of poisoning by curare.

A
  1. Curare binds to nicotinic ACh receptor
  2. Endogenous ACh fails to bind its own receptors
  3. The Na+ channels fail to open
  4. No depolarization takes place at the N-M junction
  5. Skeletal muscle fails to contract (e.g. diaphragm)
49
Q

What are the mechanisms of neurotransmitter release?

A
  1. Action potential reaches terminal
  2. Voltage-gated Ca2+ channels open
  3. Calcium enters axon terminal
  4. Neurotransmitter is released and diffuses into the cleft
  5. Neurotransmitter binds to postsynaptic receptors
  6. Neurotransmitter removed from synaptic cleft
50
Q

Postsynaptic Potential: Excitatory Postsynaptic Potential (EPSP)

A

Depolarizing graded potential

51
Q

Postsynaptic Potential: Inhibitory Postsynaptic Potential (IPSP)

A

Hyperpolarizing Graded Potential

52
Q

Temporal vs. Spatial Summation: How are they summated?

A

Temporal: Graded potentials are summated in time
Spatial: Graded potentials are summated in space

53
Q

Cholinergic (ACh)

A

Neurotransmitter; synthesized from the amino acid, tyrosine

e.g. dopamine (DA), norepinephrine (NE)

54
Q

What are the receptors for Cholinergic (ACh)?

A
  1. Nicotinic

2. Muscarinic

55
Q

What are the receptors for NE, Epi?

A
  1. Alpha-adrenergic

2. Beta-adrenergic

56
Q

What are 3 examples of neurotransmitters?

A
  1. Cholinergic (ACh)
  2. Dopaminergic (DA)
  3. Adrenergic (NE, Epi)
57
Q

How is the brain divided (3 divisions)?

A
  1. Forebrain (cerebrum, diencephalon)
  2. Brainstem (midbrain, pons, medulla oblongata)
  3. Cerebellum
    * cerebral ventricles (I, II, III, IV)
58
Q

Cerebrum: What are the motor areas?

A
  1. Primary motor cortex: precentral gyrus (frontal lobe)
  2. Premotor cortex (skilled motor activities)
  3. Broca’s area (motor speech area)
59
Q

Cerebrum: What are the sensory areas?

A
  1. Primary somatosensory cortex: postcentral gyrus or parietal lobe
  2. Somatosensory association area: comprehensive understanding of an object (e.g. size, texture)
  3. Visual cortex: occipital lobe
  4. Auditory cortex: temporal lobe
60
Q

Cerebrum: What are the association areas?

A
  1. Prefrontal cortex: intellect, cognition, recall, personality
  2. Language areas: Wenicke’s area (left hemisphere)
61
Q

Grey vs. White matter: What is its coloration and what does it mostly house?

A

Grey matter: grey coloration, houses mostly cell bodies

White matter: light coloration, houses mostly myelinated fiber tracts

62
Q

Cerebrum: Cerebral White Matter | What fibers are associated?

A

Deep to the gray matter of the cortex

  1. Commissural fibers (between hemispheres, corpus callosum)
  2. Association fibers (within a hemisphere)
  3. Projection fibers (from cerebral cortex to lower brain)
63
Q

Cerebrum: Subcortical Nuclei | What autoimmune disorder is associated?

A 
Basal ganglia (stopping, starting movement)
e.g. Parkinson's disease: depletion of dopamine in substantia nigra which terminates in basal ganglia (globus pallidus)
64
Q

Limbic System: What are its components?

A
  1. Frontal lobe
  2. Temporal lobe
  3. Hippocampus
  4. Hypothalamus (functional brain system)
65
Q

Limbic System: What are its functions?

A

Functions in learning, emotional experience and behavior (e.g. psychosomatic illness), long term memory (LTM)

66
Q

Diencephalon: Thalamus

A

Synaptic relay station from all sensory inputs, 12 nuclei

67
Q

Diencephalon: Hypothalamus

A

Main visceral control center, center for emotional responses and behavior; crucial to overall body homeostasis
e.g. regulates anterior pituitary gland function, water balance and thirst, food intake, reproductive system, circadian rhythms, and temperature; involved in control of ANS in brainstem,

68
Q

Diencephalon: Epithalamus

A
  1. Pineal gland: melatonin production (an output of the biological clock)
  2. Choroid plexus: CSF formation
69
Q

Brainstem: What does it consist of and what does it contain?

A
  • Consists of fiber tracks (ascending, descending)

- Contains “reticular formation” (RAS): controls arousal of the brain (sleep-wake cycle)

70
Q

Brainstem: Midbrain

A

Corpora quadrigemina

  1. Superior colliculi (visual reflex)
  2. Inferior colliculi (auditory reflex)
71
Q

Brainstem: Pons

A
  1. Pontine nuclei

2. Cell body for cranial nerves

72
Q

Brainstem: Medulla Oblongata

A
  • Cardiovascular center
  • Respiratory center
  • Other centers (vomiting, hiccuping, swallowing, coughing, sneezing)
73
Q

Cerebellum: What does it consist of and what is its function?

A
  • Consists of 2 hemispheres and vermis

- Function: coordination of movement, balance, posture, some types of learning

74
Q

What is the function of the spinal cord?

A

Major reflex center

75
Q

Spinal Cord: ventral view

A
  1. Gray matter (cell bodies)
  2. White matter (fiber tracts)
  3. Dorsal roots (sensory)
  4. Dorsal root ganglia
  5. Ventral roots (motor)
  6. Spinal nerves
76
Q

Spinal Cord: dorsal view

A
  1. Spinal cord trauma (e.g. paresthesias, paralysis)

e. g. of Paralysis: paraplegia (transection at T1-L1) vs. quadriplegia (transection at C1-8)

77
Q

How many pairs of cranial and spinal nerves are there in the PNS?

A

12 pairs of cranial nerves; 31 pairs of spinal nerves

78
Q

What is the functional division of PNS?

A
  1. Somatic division: consists of a single neuron between CNS and skeletal muscle cells, innervates skeletal muscle, can lead only to muscle excitation
  2. Autonomic division: has 2-neuron chain (connected by a synapse) between CNS and effector organ, innervates smooth and cardiac muscle, glands, and GI neurons, can be either excitatory or inhibitory
79
Q

What are the cranial nerves?

A
  1. Olfactory: from receptors in smell
  2. Optic: from receptors in eye
  3. Oculomotor: alters lens shape for near or far vision
  4. Trochlear: moves eyeball downward and laterally
  5. Trigeminal: chewing muscles
  6. Abducens: moves eyeball laterally
  7. Facial: facial expression
  8. Vestibulocochlear: from receptors in inner ear
  9. Glossopharyngeal: swallowing and parotid salivary gland
  10. Vagus: pharynx, larynx, smooth muscle
  11. Accessory: neck skeletal muscles
  12. Hypoglossal: tongue skeletal muscles
80
Q

Somatic vs. Autonomic Nervous System: Effector Organs

A

Somatic: skeletal muscle
Autonomic: smooth/cardiac muscles, glands, other cells

81
Q

Autonomic Nervous System: Sympathetic vs. Parasympathetic Division

A

Parasympathetic: “rest & digest”
Sympathetic: “fight-or-flight”

82
Q

Protection of the Brain: What are its components?

A
  1. Skull
  2. Meninges (dura mater, arachnoid mater, pia mater)
  3. Cerebrospinal fluid (CSF)
  4. Blood-brain-barrier (BBB)
83
Q

Cerebrospinal Fluid (CSF): How is it produced and what does space does it fill?

A
  • Produced by choroid plexus in ventricles

- Fills the subarachnoid space and circulates

84
Q

Blood-Brain Barrier (BBB)

A
  • Most impermeable capillaries in the body (tight junctions formed by astrocytes)
  • Highly selective transport system (for glucose, some essential amino acids)
  • Lipid-soluble molecules freely penetrate (O2, CO2, alcohol, nicotine, caffeine)

BISC276 (4 decks)

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