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mcat biology > The nervous system > Flashcards

The nervous system Flashcards

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1
Q
  • Neurons
A
  • trasnsmit electrical impulses

- do not physically touch another cell

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2
Q

anatomy of neurons

A
  • soma (cell body): house nucleus and other organelles
    • dendrites: recieve incoming signals
    • Axon hillock: integrate incoming signal to axon
    • Axon
    • Myelin (optional)
    • snaptic knob: maximizes neurotransmission to next neuron. ensures proper release of signal
    • Synapse: presynaptic terminus + synaptic celft + postsynaptic membrane.
    • Tracts: bundle of axons at PNS
    • Nerve: bundle of axons at CNS
      • sensory, motor, or mixed types
    • nuclei: bundle of cell bodies PNS
    • Ganglia: bundle of cell bodies CNS
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3
Q

Purpose of Myelin

A
  • prevents signal loss or crossing of signals so to maintain a signal within one neuron.
    - Increases speed of conduction.
    - form nodes of Ranriver
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4
Q

what produces myelin sheath

A
  • produced by oligodendrocytes (CNS) or schwann cells (PNS)
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5
Q
  • Other cells in the nervous system
A
  • Glial / neuroglia:
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6
Q

types of Glial cells

A
  • Astrocytes:
    - Ependymal cells
    - Microglia
    - Oligodendrocytes and Schwann cells
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7
Q

Function of astrocytes

A
  • support cells for brain tissue
    - form blood-brain barrier
    - most abundant cell in the brain.
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8
Q

Function of Ependymal cells

A
  • produces cerebral spinal fluid (CSF)
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9
Q

Function of Microglia

A
  • phagocytizes waste products and pathogesn in CNS
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10
Q

actions potential facts

A
  • all or nothing messages

- cause release of neurotransmitters

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11
Q

what is resting potential

A

the electric difference across the cell membrane (neurons = 70mV)

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12
Q

what are the ions involved, concentrations, manner of movement across plasma membrane, and respective equilibrium potential

A
  • Potassium
    - 140mM inside vs 4mM outside
    - Leak channels facilitate movement out of cell
    - Leaking continually occurs toward negative potential
    - equilibrium potential: movement inside vs outside is balanced at -90mV ( the - value indicates movement out of cell)
    - Sodium
    - 12mM inside vs 145 mM outside
    - movement into cell
    - facilitated by leak channels
    - encouraged by negative value and lower concentration inside the cell.
    - Equilibirum potential: movement is balanced at +60mV (the + value indicates movement into the cell)
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13
Q

what is resting potential and why is that

A
  • Resting poteintial is -70mV because of more potassium leak channels than sodium ones.
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14
Q

Na/K ATPase facts

A
  • maintain resting potential
    - pumps sodium out of cell
    - pumps potassium into cell
    - utilizes ATP
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15
Q

importance of the axon Hillock

A
  • site of summation for multiple singals (excitatory and/or inhibitory)
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16
Q

Types of summation

A
  • Temporal
    - multiple signals close to each other in time. (time frame)
    - spatial
    - multiple signals close to each other in space. (space frame)
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17
Q

Basic function vs higher function of nervous system

A

Basic: associated with the senses, movement, and automatic function.

Complicated:associated with cognition, emotion, or consciousness

18
Q

upper motor neuron dysfunction

A

include hyperreflexia, clonus, hypertonia, and the babinski sign.

19
Q

lower motor neuron dysfunction

A

include atrophy, hypotonia, hyporeflexia, and skeletal muscle twitches.

20
Q

action potential

A

Neural information is coded for by the frequency and number of action potentials, not the size of the action potential.

21
Q

difference between nerves and tract

A

Nerves are collections of neurons in the peripheral nervous system and may contain multiple types of information (sensory or motor).
Tracts are collection of neurons in the central nervous system and contain only one type of information.
Neves may carry more than one type information; tracts can only carry one type of information,.

22
Q

If a chemist wants to make a drug that prevents GABA from binding to its receptor on the postsynaptic neuron. What should be true about this drug?

A

The drug should have LOWER Km than GABA and an ANTAGONIST for the receptor.

Terminology:

  • Antagonist = blocker
  • Agonist = activator.
23
Q

ependymal cells

A

line the ventricle of the brain
Produce CSF
form epithelial tissue called ependyma
cellular structure: simple cuboidal

24
Q

antagonists of voltage-gated potassium channels

A

Will render a neuron unable to repolarize.

Result in alot of neurotransmitter release.

25
Q

bypass the blood-brain barrier.

A

Since astrocytes form blood brain barrier. you would have to disrupt their tight junctions.

26
Q

Effect of demyelination

A

Results in slower transmission action potentials, delaying neurotransmitter release.

27
Q

Antagonist of potassium leak channels.

A

Results to decrease in potassium permeability therefore in PROGRESSIVE depolarization of the neuron as POSITIVE CHARGE builds up inside.

28
Q

Myelin’s role in terms of capacitance

A

To DECREASE capacitance by blocking the accumulation of oppositely charged molecules along the axonal membrane.

29
Q

piloerection (hair standing end)

A

result of SYMPATHETIC MOTOR NEURON.

30
Q
  • types of reflex arc:
A
  • Monosynaptic
    - No interneuron at CNS b/w sensory and motor neuron
    - i.e knee jerk reflex
    - polysnaptic
    - contains atleast one interneuron between sensory and motor neuron.
    - i.e withdrawal reflex
31
Q

subdivision of the Autonomic Nervous System

A
  • sympathetic
    - fight or flight
    - accelerate heart rate
    - inhibit digestion
    - releases epinephrine from adrenal medulla into blood stream ( these cells are derived from neural crest)
    - Originate in the middle of the spinal cord.
    - short axon to the synapse of another neuron. From there, there is a long axon to the target neuron.
    - parasympathetic
    - conserves energy
    - increase peristalsis and exocrine secretions
    - utilizes acetycholine (preganglionic and post ganglionic)
    - vagus nerve innervates thoracic and abdominal
    - originate in the brainstem or at the bottom of the spinal cord.
    - long axons to the synapse of another neuron, then a short axon to the target neuron.
32
Q
  • Peripheral Nervous System (somatic and autonomic)
A
  • includes 31 pairs spinal nerves and 10 cranial nerves

- connects CNS to rest of body

33
Q
  • Somatic
A
  • has sensory and motor fibers

- motor neuron goes directly from CNS to target tissue

34
Q
  • Autonomic
A
  • regulates
    - involuntary muscles (heartbeat, respiration, digestion and glandular secretions)
    - body temp
    - independent of conscious control
    - motor output has 2 neurons (preganglionic and postganglionic)
35
Q

supraspinal circuits

A 
- used during times when a stimuli requires cerebral cortex processing before a response to generated.
 other times (i.e patellar tendon reflex), sensory stimuli is immediately followed by motor signal
36
Q

3 ways to regulate the synapse

A
  • signal degradation (i.e acetycholinesterase
    - signal reuptake
    - lateral diffusion
37
Q
  • Impulse propagation
A
  • electrical movement of a signal down the axon followed by neurotransmitter release.
    - A one way direction.
    - speed factors
    - ⇡ axon length = ⇣ speed
    - ⇡ cross-sectional area = ⇡ speed
    - myelin = ⇡ speed
    - ⇡ stimulus intesity = ⇡ frequency
38
Q

Neurotransmitter pathway

A
  • calcium influx → fusion of vesicles to membrane → exocytosis → neurotransmitter bind receptors (ion channel or G-protein) → depolarization or hyperpolarization.
39
Q

Sodium ions

A
  • encouraged by negative value and lower concentration inside the cell.
    - Equilibirum potential: movement is balanced at +60mV (the + value indicates movement into the cell)
40
Q

potassium

A
  • Leaking continually occurs toward negative potential
    - equilibrium potential: movement inside vs outside is balanced at -90mV ( the - value indicates movement out of cell)
41
Q

Dorsal root Ganglion

A

afferent (sensory) neurons

contains pseudounipolar neurons

42
Q

Graded potential

A

they are decremental ( their amplitude diminishes as they travel away from the original site)

can also be hyperpolarizing or depolarizing, depending on the stimulus.

mcat biology (9 decks)

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