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Anatomy > Nervous system > Flashcards

Nervous system Flashcards

1
Q

Functions of the Nervous System?

A

*Sensory input
- Sensory receptors monitor internal
and external stimuli
*Interpretation and integration of
sensory input
- Processes information from multiple
receptors and dictates a response
*Motor output
- Effector organs (muscles or glands) are
activated →response

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2
Q

What is the Flow of Impulses Through Nervous System? Example

A

*SENSORY INPUT→fly lands on arm and bends one or more hairs activating neurons wrapped around hair root
*INTEGRATION→activation of neurons processed by brain and/or spinal cord
*MOTOR RESPONSE→muscles of your other arm are activated so you can reach over and brush off fly
* Results in rapid communication throughout the
body and maintenance of homeostasis

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3
Q

What are the divisions of the Nervous System?

A

*Central Nervous System (CNS)
*Peripheral Nervous System (PNS)

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4
Q

What is the Central Nervous System (CNS)?

A

Central Nervous System (CNS)
* Integration and interpretation of sensory
input
* Dictates motor response
* Brain and spinal cord

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5
Q

What is the Peripheral Nervous System (PNS)?

A

Peripheral Nervous System (PNS)
* Neurons transport sensory input toward
CNS & motor output away from CNS
* Afferent (sensory) division
* Efferent (motor) division
* Includes cranial and spinal nerves

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6
Q

What are the Further Divisions of Sensory and Motor Components?

A

These divisions are associated with the body regions they serve
* Visceral functions: organs within body cavities
* Somatic functions: all other structures, esp. muscles and skin

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7
Q

What are the nervous tissue cell types?

A

Cell types:
* Neurons
* Neuroglia
*Cell body (soma)
*Dendrites
* Axon

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8
Q

What are neurons?

A
  • Neurons
  • Able to respond to a stimulus and carry and electrical impulse
  • Excitable cells
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9
Q

What are Neuroglia?

A

Neuroglia
* Help neurons function more efficiently
* Non-excitable cells
- Current research is disputing the generalized classification of glial cells as helpers for neurons
– Ex. Glial cells and pain modulation (see

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10
Q

What are Cell body (soma)?

A

Cell body (soma)
* Single nucleus and organelles

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11
Q

What are Dendrites?

A

Dendrites
* Receptive (input) regions
* Carry information toward cell body
* Number can vary dramatically

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12
Q

What are axons?

A

Axon
* Carries information away from cell
body
* One per neuron
* Can be very short or very long (4 feet)
* End at axon terminal →synapse
* Often surrounded by myelin sheaths

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13
Q

What are the classifications of neuron structure?

A

*Multipolar
*Bipolar
*Unipolar

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14
Q

What are Multipolar neurons?

A

Multipolar: many dendrites, single axon
* Most neurons in CNS
* Motor neurons and interneurons

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15
Q

What are bipoalr neurons?

A

Bipolar: single dendrite, one axon
attached to cell body
* Only found in a few locations
* Special sensory neurons
- Retina, olfactory mucosa

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16
Q

What are unipolar neurons?

A

*Unipolar: single axon connected via
short process to cell body
- Typical sensory neuron

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17
Q

Types Neurons Classified by Function (PNS)

A

*Sensory neuron = afferent neuron
*Motor neuron = efferent neuron
*Interneuron

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18
Q

What are the components of Sensory neuron?

A

Sensory neuron = afferent neuron
* Brings impulses to CNS
* Cell bodies are clustered in ganglia (outside of CNS) = Dorsal root ganglion
* Unipolar

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19
Q

What are the components of motor neurons?

A

Motor neuron = efferent neuron
* Takes impulse away from CNS
* Cell bodies are within CNS
* Multipolar

20
Q

What are the components of interneuron?

A

Interneuron
* Neurons within CNS
* Accounts for 99% of all neurons of body (all within CNS)
* Multipolar

21
Q

Neuroglia in CNS?

A

In CNS:
* Astrocytes
* Microglia
* Ependymal cells
* Oligodendrocytes

22
Q

Neuroglia in PNS?

A

In PNS
* Satellite cells
* Schwann cells

23
Q

What are the components of astrocytes?

A
  • Most abundant glial cell
  • Surround capillaries and neurons
  • Numerous functions
  • Forms the blood brain barrier (more later)
  • Regulate neurotransmitter levels
  • Increase blood flow to active brain regions
  • Produce BDNF (brain-derived trophic factor)
    which promotes neural growth
  • New research (FYI): Role in sleep cycles
24
Q

What are the components of Microglia?

A

*Smallest and least abundant glial cell in CNS
*Macrophages
- Consume microorganisms and dead neurons
- Originate in red bone marrow and migrate to CNS during fetal development

25
Q

What are the components of Ependymal Cells?

A

*Form simple epithelium that lines hollow portions of brain and spinal cord
- Ventricles of brain
- Central canal of spinal cord
*Have cilia that help circulate cerebrospinal fluid in CNS

26
Q

What are the components of Oligodendrocytes?

A

*Myelin sheaths are formed by oligodendrocytes in the CNS
*Oligodendrocytes have many processes that wrap around many different axons
*Result of myelination is increased speed of conduction of action potential

27
Q

What are the components of satellite cells?

A

*In PNS
*Surround cell bodies
*Prevent “crossover” when many cell bodies are crowded together
- Ganglia are full of cell bodies

28
Q

What are the components of Schwann Cells?

A

*Surround axon, form myelin sheaths in PNS
- Increase speed of action potential

29
Q

What is Myelin Sheaths in PNS?

A

*Myelin sheaths increase speed of action potential down axon
- Myelin sheaths are made of Schwann cell’s compacted plasma membranes (made o
phospholipids) →white in color
*Also insulate axons from each other (prevents action potential “cross talk”)

30
Q

What are the Myelinated Axons in the PNS?

A

*Schwann cell wraps around an axon
*One axon will have numerous
Schwann cells
- Schwann cells do not touch each other
- Gaps are left = nodes of Ranvier

31
Q

Purpose of Myelinated Axons?

A

*Action potentials jump over the myelin, jumping from node of Ranvier to node of Ranvier = Saltatory Conduction

32
Q

What are the NonMyelinated Axons in the PNS?

A

*Only thick, fast conducting axons are myelinated
- Thin, slower are not
*Unmyelinated axons have a Schwann cell partly enclose 15 or more unmyelinated axons
- Axons are separated
*Slower conduction

33
Q

What is Multiple Sclerosis?

A

*Autoimmune disease where myelin is
attacked in CNS
- Oligodendrocytes are destroyed
- Plaques develop when myelin is destroyed
- Inflammation develops and can damage
axons
*Overall: action potentials are disrupted
causing motor and sensory issues

34
Q

What are gliomas?

A

*In general, neurons have limited ability to regenerate or undergo mitosis
- As a result, most brain tumors are derived from glial cells = glioma

35
Q

Nerve versus Nerve Tract

A

Nerve
*In PNS, axons of sensory and
motor neurons
*Example
- Nerves off of spinal cord
Nerve Tract
*In CNS, axons of interneurons
*Example
- Corpus callosum of brain

36
Q

Are nerves mixed?

A

*Most nerves contain both sensory and motor neurons
- “Mixed” nerves are typical (ex. Spinal nerves)

37
Q

Are all nerves mixed?

A

*There are exceptions
- Ex. Some cranial nerves are sensory (optic nerve) or motor (hypoglossal nerve) only

38
Q

What is the structure of a nerve?

A

A nerve is an organ
* Cells (axons of neurons, Schwann cells)
* Connective tissue
- Epineurium (dense irregular CT)
- Perineurium (fibrous CT)
- Endoneurium (over myelin, thin reticular)
* Blood vessels

39
Q

What are Synapses?

A

*Synapse = site where neurons communicate
with each other or with other cell types

40
Q

Movement of nerve impulse?

A

Nerve impulse: from presynaptic axon terminal to postsynaptic dendrite

41
Q

What are the components of synapse?

A

*Presynaptic axons end at axon terminals
*Within axon terminals are synaptic vesicles containing
neurotransmitters
* Neurotransmitters are chemical messengers
* Ex. Acetylcholine, Norepinephrine
*Neurotransmitters are released into a synaptic cleft (space between
synapsing neurons)
*Receptors on postsynaptic cell (dendrite or cell body) bind the
neurotransmitters
* This initiates an impulse or response

42
Q

What are the Types of Synapses?

A

There are different types of neuron to
neuron synapses
* Axodendritic
- Presynaptic axon to postsynaptic dendrite
- Most common
* Axosomatic
- Presynaptic axon to postsynaptic cell body

43
Q

Electrical and chemical synapse?

A

*Some synapses are gap junctions between neurons (referred to as electrical synapse)
*Not as common as chemical synapse (more common in invertebrates)

44
Q

What happens when concentrations of some neurotransmitters are high?

A

Higher than normal concentrations of some neurotransmitters can be toxic and these toxic levels have been shown to play a role in the degeneration of neurons associated with conditions such as:
* Multiple sclerosis
* Alzheimer’s disease
* Amyotrophic lateral sclerosis (ALS)
* Parkinson’s disease

45
Q

What is Tic Douloureux?

A

*Means: “painful twitching”
*Also called Trigeminal Neuralgia
*Extremely painful chronic condition
- A blood vessel compresses the trigeminal nerve causing loss of myelination of sensory nerve fibers
- The lack of insulation allows touch and pain nerve fibers to cross-talk
- Touch is perceived pain by brain

46
Q

What is Neuronal Regeneration in PNS?

A

In the PNS
* If only axon is destroyed (not cell body), Schwann cells help axon sprout through a regeneration tube
* There can be partial recovery

47
Q

What is Neuronal Regeneration in CNS?

A

In the CNS
- Historically, there has been the “no-new-neuron doctrine”
– Once neurons die, they are not replaced by new neurons
- HOWEVER…recently, neural stem cells have been discovered in the brain
– In the hippocampus (memory center) and olfactory bulb (smell)
* The implication have profound potential for brain and spinal cord injuries
*And, that you actually can teach an old dog new tricks!

Anatomy (22 decks)

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