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BMS101 > The Nervous System > Flashcards

The Nervous System Flashcards

1
Q

2 structural subdivisions of the nervous system

A
  1. Central nervous system (brain & spinal cord)

2. Peripheral nervous system (cranial nerves, spinal nerves and ganglia)

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2
Q

Sensory Nervous system

  • AKA
  • what it does
  • 2 components
A

-aka afferent nervous system
-Receives sensory info from receptors in PNS & transmits to CNS
2 components;
1. Somatic sensory
-general senses such as touch, pain, pressure, vibration & proprioception
-special senses such as taste, vision, balance, hearing and smell
2. Visceral sensory:
-impulses from viscera (generally temp & stretch)

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3
Q

Motor Nervous System

  • AKA
  • what it does
  • 2 components
A
  • AKA efferent nervous system
  • sends impulses from CNS to muscles & glands
  • 2 components;
    1. Somatic motor (Voluntary)
    • impulses from CNS that cause contraction of skeletal muscles
      1. Autonomic motor (Involuntary)
    • impulses from CNS that regulate smooth & cardiac muscles (as well as glands)
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4
Q

2 cell types w/in nervous system

A
  1. Neurons (nerve cells)
    • electrically excitable cells that initiate, transmit & receive nerve impulses
    • approx. 35-100 billion neurons
  2. Glial cells (support cells)
    • Nonexcitable cells that support and protect neurons -> provide an organized, supporting framework for all nervous tissue
    • 100 billion - 1 trillion glial cells
    • capable of mitosis (neurons can’t)
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5
Q

Neurons

-3 characteristics

A

-Basic structural unit of nervous system
-Conduct nerve impulses from one part of the body to another
CHARACTERISTICS;
-High metabolic rate (needs lots of O2, glucose)
-Extreme longevity (stay in body for whole life)
-Nonmitotic

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6
Q

Neuron structure

-3 main structural regions

A
  • 3 main structural regions;
    • Cell body
    • Dendrites
    • Axon
  • Sends electrical impulses unidirectionally
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7
Q

Neuron; Cell body

A
  • contains typical organs such as Nucleus, nucleolus, mitochondria, free ribosomes & rough ER.
  • aka soma
  • is control centre
  • responsible for receiving, integrating & sending nerve impulses
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8
Q

Neuron; Dendrites

A
  • Input
  • short processes that branch from cell body
  • Receive nerve impulses & carry them to cell body
  • more dendrites = more impulses that can be received
    • many also have dendrite spines to increase SA
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9
Q

Neuron; Axons

  • what they do
  • axon hillock
  • synaptic knobs
  • Myelin
A
  • Output
  • Transmit nerve impulses away from cell body & transmit info to other cells
  • axon hillock = region where axon connects to the cell body
  • neurons have 1 or no axons
  • Synaptic knobs = end of axons that transmit impulse to effector cells
  • Often covered in Myelin (insulating concentric layers that allow for faster nerve impulses)
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10
Q

Neuron Classification (Structurally; 3 types)

A

3 types depending on number of cell processes emanating directly from cell body;

  • Unipolar: Single, short process that branches like a T (most sensory neurons of PNS)
  • Bipolar: Two processes, one dendrite & one axon (relatively uncommon in humans -> primarily linked w/ special senses)
  • Multipolar: many dendrites and a single axon (most common neuron e.g. motor neuron)
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11
Q

Neuron Classification (Functionally; 3 types)

-what they do

A
  • Sensory (Afferent): transmit impulses from sensory receptors to CNS
  • Motor (Efferent): transmit impulses from CNS to muscles or glands
  • Interneurons: Facilitate communication between sensory and motor neurons
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12
Q

Glial Cells

  • aka
  • where found
  • features
A
  • aka neuroglia
  • Found in both CNS & PNS
  • Smaller than neurons & capable of mitosis
  • Physically protect & nourish neurons
  • more numerous than neurons
  • Brain tumors more likely to be derived from glial cells than neurons
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13
Q

Glial Cells of the CNS (4 types)

A
  • Astrocytes (most common)
  • Ependymal cells
  • Microglial cells
  • Oligodendrocytes (same structure in PNS but have another name)
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14
Q

Glial Cell of CNS; Astrocytes

-Functions

A 
-Most abundant
FUNCTIONS
-Helping form Blood-brain barrier (protects brain from toxins)
-regulating tissue fluid composition
-helping regulate synaptic transmission
-forming structural network (aids in forming framework in brain)
-replacing damage neurons
-Assisting neuronal development

*hugs the capillary

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15
Q

Glial cells of CNS; Ependymal cells

-functions

A
  • ciliated cuboidal epithelial cells that line ventricles of brain & central canal of spinal cord
  • In conjunction w/ other glial cells, the ependymal cells produce cerebral spinal fluid (CSF) & form choroid plexus
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16
Q

Glial Cells of CNS; Microglial cells

-Function

A
  • Small cells that are motile
  • wander through the CNS & exhibit phagocytic activity, removing cellular debris from dead or dying cells
    • aid in pathogen removal/detection
17
Q

Glial cells of CNS; Oligodendrocytes

  • where found
  • what they do
A
  • Associated w/ CNS axons only
  • wrap themselves around axons like electrical tape
  • produce myelin - is an insulator of electrical activity (allows faster electrical impulses along axon)
18
Q

Glial Cells of PNS

  • 2 types
  • functions
A

2 types;

  1. Satellite cells: flattened cells arranged around neuronal cell bodies in ganglia
  2. Neurolemmocytes: aka Schwann cells - associated w/ PNS axons only
    • wrap themselves around axons like electrical tape, produce myelin which is an insulator of electrical activity
    • same structure & function as oligodendrocytes
19
Q

Myelination of Axons

A
  • Affects ability of neurons to conduct nerve impulses, also called action potentials
  • Formed by neurolemmocytes in PNS and oligodendrocytes in CNS
    • serves as insulation
20
Q

Axon regeneration

A
  • Damaged axons can regenerate if cell body is intact and critical amount of neurilemma remains
  • depends on extent and site of damage
  • neurolemmocytes play important role in process
21
Q

Wallerian Degeneration

A
  • Trauma severs axons
  • Proximal portion of each severed axon seals off and swells - distal portion disintegrate
  • neurileema and endoneurium form regeneration tube
  • axon regenerates and remyelination occurs
  • innervation to effector is restored
22
Q

Nerves
-what they are

-3 layers

A
  • Cablelike bundle of parallel axons
  • Surrounded by three CT wrappings;
    1. Endoneurium (within): around each individual axon
    2. Perineurium (around): around individual fascicles
    3. Epineurium (upon): around the entire nerve

*between fasicles = blood vessels

23
Q

Synapses

  • what they are
  • 3 things a typical neuron consists of
A 
-Specialized junctions b/w one axon and another neuron, muscle cell or gland cell
Typical neuron;
-Presynaptic neuron
-Postsynaptic neuron
-Synaptic cleft

*can be electrical or chemical

24
Q

Autonomic Nervous system

-what it is

A
  • is a complex system of nerves that govern involuntary actions
  • works constantly w/ somatic nervous system to regulate body organs and maintain normal internal functions
  • ANS and SNS both part of central nervous system & peripheral nervous system
  • SNS operates under our conscious/voluntary control
  • ANS operates under involuntary contraol - usu unaware of them
25
Q

Comparison of Somatic & Autonomic Nervous system

A
  • Both use sensory & motor neurons
  • SNS: somatic motor neurons innverate skeletal muscle fibres, causing conscious voluntary movement
    • Single lower motor neuron axon extends uninterrupted from spinal cord to one or more muscle fibers
  • ANS motor neurons innervate smooth muscle fibers, cardiac muscle fibers or glands
  • ANS motor neurons can either excite or inhibit cells in viscera
    • two-neuron chain innervates muscles and glands
26
Q

Two-neuron chain in ANS

A
  • First neuron in ANS pathway is preganglionic neuron
    • cell body in brain or spinal cord
  • preganglionic axon extends to second cell body housed w/in autonomic ganglion in peripheral nervous system
  • second neuron in pathway called ganglionic neuron
  • a postganglionic axon extends from its cell body to effector cells
  • two neuron chain vastly increases communication & control of ANS
27
Q

ANS Subdivisions & what they do

A
  • Sympathetic:
    • mobilises body during extreme situations -> preparation of body for emergencies (fight or flight)
  • Parasympathetic:
    - maintenance activities and conserves body energy
    - conservation of energy and replenishment of nutrient stores (rest and digest)

*two divisions counterbalance each other

28
Q

Role of Sympathetic Division

A
  • Fight or flight system
  • E activities; Exercise, excitement, emergency & embarrassment
  • promotes adjustment during exercise -> blood flow to organs is reduced

-e.g. HR increases, breathing rapid and deep, skin cold and sweaty and pupils dilate

29
Q

Role of Parasympathetic Divison

A
  • concerned w/ keeping body energy use low
  • D activities; Digestion, defection and diuresis
  • e.g. blood pressure, HR and respiratory rates low
    • GI tract activity high
    • skin is warm and pupils constricted
30
Q

Autonomic nervous system

A
  • Two systems of ANS service same visceral organs but work in opposition to each other (antagonistic)
  • balanced to keep ourselves in a state of dynamic balance

BMS101 (30 decks)

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