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BIO 240 Anatomy and Physiology I > Nervous Tissue > Flashcards

Nervous Tissue Flashcards

1
Q

What are the broad functions of nervous tissue?

A

Body’s control center and communication network

3 Broad Functions:

  1. Sense change in environment
  2. Integrates and interprets
  3. Responds if necessary
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2
Q

What are the divisions of the nervous system?

A

Central Nervous System

-Brain and Spinal Cord

Peripheral Nervous System

  • Somatic
  • Autonomic Nervous Systems

→Sympathetic and Parasympathetic Nervous systems

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3
Q

What are neuroglia and what are some examples?

A

Support cells for neurons within nervous tissue

Examples

  1. Oligodendrocytes = CNS
  2. Astrocytes = CNS
  3. Microglia = CNS
  4. Ependymal cells = CNS
  5. Schwann Cells = PNS
  6. Satelite Cells = CNS and PNS
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4
Q

What are the parts of the neuron pictured?

A

Cell Body

  • nucleus
  • nucleolus
  • nissl substance

Dendrites

Axon

  • axon hillock
  • trigger zone
  • axon collateral
  • telodendrion
  • synaptic knobs
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5
Q

What kinds of cells myelinate neurons in the CNS vs PNS? How does the myelin sheath differ?

A

CNS

  • Oligodendrocytes
  • each oligodendrocyte myelinates several nerve fibers inwards with centripetal myelination

PNS

  • Neurolemmocytes
  • schwann cells spiral repeatedly around single nerve fiber outwards with centrifugal myelination

Outer most layer of myelin sheath is neurilemma and surrounded by connective tissue calle endoneurium

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6
Q

What are the different types of neuron structures?

A

Unipolar Neurons (pseudounipolar)

  • single process leading away from cell body
  • carry signals to spinal cord for senses like touch and pain

Bipolar Neurons

  • have one axon and one dendrite
  • accessory sensory neurons including olfactory cells of nose

Multipolar Neurons

  • most common
  • most neurons of the brain and spinal cord
  • motor neurons
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7
Q

How do impulses flow in neurons?

A

Dendrites carry infor to cell body

and

Axons carry info away from cell body

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8
Q

What are the different functional classifications of neurons?

A

Sensory Neurons

  • also known as afferent (arriving)
  • unipolar neurons
  • from PNS to CNS

Association Neurons

  • also known as interneurons
  • interconnect incoming sensory pathways and outgoing motor pathways and amke decisions about information
  • multipolar neurons and bipolar neurons in special sense pathways

Motor Neurons

  • also known as efferent (exiting) neurons
  • carry information primarily to muscle/gland cells, the effectors
  • from CNS to PNS
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9
Q

What is a nerve fiber?

A

one process from one neuron

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10
Q

What is a nerve vs tract?

A

Nerve

-bundle of nerve fibers travelling through PNS

Tract

-bundle of nerve fibers travelling through CNS

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11
Q

What is a ganglion vs nucleus?

A

Ganglion

-collections of cell bodies in PNS

Nucleus

-collections of cell bodies in CNS

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12
Q

What is the difference between gray matter vs white matter?

A

Gray matter

-don’t travel far so unmyelinated

White matter

-myelinated fibers so faster and travel farther distances

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13
Q

What properties does communication by neurons depend on?

A

1. Electrical voltage, called resting membrane potential, across the cell membrane

  • requires energy, ATP, to maintain
  • Na+/positive outside and K+/negative inside

2. Neuronal cell membranes contain different ion channels that may be open or closed

-ion channels don’t require energy, facilitated diffusion

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14
Q

What is the resting membrane potential?

A

Buildup of ions on each side of the cell membrane

  • creates a polarized membrane
  • separation of charges creates potential energy
  • resting membrane potential is -70mV
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15
Q

What factors contribute to the resting membrane potential?

A

1. Distribution of ions on either side of cell membrane

  • extracellular fluid rich in Na+ and Cl-
  • intracellular fluid rich in K+ and anions like negatively charged proteins

2. Relative permeability of cell membrane to the ions

  • K+ and Cl- slightly more permeable than Na+
  • impermeable to intracellular proteins
  • There is a slow K+ leak w/not much of a Na+ leak
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16
Q

What are gated ion channels and what are the types?

A

Gated channels that open in response to specific stimulus

1. Chemically gated ion channel

  • require ligand to bind to open/close channel
  • normally found on dendrites of multipolar neurons

2. Voltage gated ion channel

  • change in cell membrane potential open/close channel
  • usually ligand gated channel starts voltage change

3. Mechanically and light gated channels

-mechanical stress or light opens/closes

17
Q

What is the threshold stimulus?

A

Minimum change in resting membrane potential to initate action potential

-70mV to -55mV

18
Q

What are the steps of an action potential?

A
  1. Depolarization
  2. Repolarization
  3. Refractory period
19
Q

What is depolarization?

A

First step of action potential

  1. Threshold stimulus is reached
  2. Voltage gated Na+ channels open at site of stimulus
  3. Na+ influx through channel (-70 to +30mV)
  4. Positive feedback opens adjacent voltage gated Na+ channels
20
Q

What is repolarization?

A

Second step of action potential

  1. Voltage gated K+ channels open
  2. K+ efflux from cell (+30 to -90mV)
  3. Hyperpolarization
  4. Na-K ATPase pumps restore ions to proper concentrations on either side of the membrane
21
Q

What is the refractory period?

A

Time after action potential where another AP either can’t happen or is much more difficult to occur

1. Absolute refractory period

  • voltage gated channels either opening/closing
  • CANNOT have 2nd AP

2. Relative refractory period

  • hyperpolarized membrane at -90mV
  • AP CAN occur but need Suprathreshold stimulus
22
Q

Explain the action potential.

A
23
Q

Go through the positive feedback mechanism of an action potential.

A
24
Q

What are the two types of conduction?

A

Continuous Conduction

  • trigger zone to synapse
  • propagation of the message
  • one direction only
  • 0.5 meters/sec

Saltatory Conduction

  • myelin sheath
  • nodes of ranvier
  • 130 meters/sec
  • conserves energy b/c only maintain membrane potential at nodes of ranvier
25
Q

What is a synapse

A

A junction between two nerve cells

  • integrate and filter information
  • point where signals are either transmitted or inhibited
  • there are presynaptic and postsynaptic neurons
26
Q

How does a chemical synapse work?

A
  1. Arrival of action potential
  2. Voltage gated Ca2+ open = influx and signal neurotransmitter vesicles to fuse
  3. Synaptic vesicles rupture
  4. Neurotransmitter released
  5. Neurotransmitter diffusion
  6. Neurotransmitter binds receptor
  7. Postsynaptic potential created
27
Q

What are the types of post synaptic potentials?

A

Inhibitory (IPSP) - hyperpolarizes postsynaptic membrane

-open Cl- channel to make cell more negative

Excitatory (EPSP) - facilitates postsynaptic membrane

28
Q

What are the net effects of postsynaptic potentials?

A

1. Facilitation: bring closer to threshold but not reach

2. Summation (action potential): reach AP threshold

  • Spatial: multiple neurons signaling one
  • Temporal: one neuron signaling another one multiple times

3. Hyperpolarization (inhibition): make threshold harder to reach

29
Q

How can neurotransmitters work?

A

Can be excitatory and/or inhibitory

-eg. epinephrine inhibits digestion but stimulates breathing

30
Q

How are neurotransmitters removed from synaptic cleft so that its effects on the postsynaptic cell is limited?

A
  1. Diffusion away from the synapse
  2. Enzymatic degradation within the synapse
  3. Reuptake into the presynaptic neuron
31
Q

What are the types of neuronal circuits?

A
  1. Simple series
  2. Diverging
  3. Converging
  4. Reverberating
  5. Parallel after-discharge

BIO 240 Anatomy and Physiology I (19 decks)

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