Chapter 13- Neural Tissue Flashcards Preview

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Flashcards in Chapter 13- Neural Tissue Deck (80)
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1

nervous system

coordinate all body systems
-accomplished by the transmission of signals
-body parts to CNS
-CNS to body parts
-Electrochemical signaling

2

endocrine system

slower scale
-uses chemicals in the blood stream called hormones

3

general makeup of NS

-many organs, each composed of several tissue
-connective tissue
-blood vessels
-neurons
-neuroglia

4

2 groups of NS

CNS
-brain and spinal chord
PNS
-cranial and spinal nerves (ganglia)

5

CNS makeup

brain and spinal chord
-covered by meninges (house fluid)
-starts as a hollow tube
-bathed in cerebrospinal fluid
-integration center

6

PNS makeup

consists of cranial and spinal nerves that contain both sensory and motor fibers
-connects CNS to muscles, glands, and all receptors
-brings info to and from CNS
(only sensory OR motor neurons)

7

PNS: 2 types

Afferent division= sensory
Efferent division= motor
--somatic (conscious control)
--autonomic (unconscious)

8

Receptors

detect stimuli

9

sensory

afferent PNS

10

integrative

CNS

11

motor

efferent PNS

12

effector

muscle/gland

13

Nervous tissue

neurons
-structural and functional units
-excitable
-amitotic (unrepairable)
Neuroglia cells
-accessory cells
-act like connective tissue

14

3 major structures of neurons

soma
dendrites
axon

15

soma

cell body
-mononucleate

16

soma consists of

nissi bodies: ribosomes clusters, give gray color
axon hillock: connects soma to axon
perikaryon: region around the nucleus
neuronfibrils: cytoskeleton that extend into dendrites/axons; gives shape

17

dendrites

-respond to neurotransmitters
-short, branched, unmyelinated
-specialized for contact with other neurons
-conducts impulses towards the cell body

18

axon

-only one cell
-conducts nerve impulses away from soma
-can give off collaterals (branches at end)
-end in synaptic terminals
-produce neuraltransmitters
-may contact one of three things: another neuron, muscle fibers, gland

19

myelin sheath

glial cells that may wrap around the axon

20

axonal transport (axoplasmic flow)

movement of cellular materials (NOT signals) through axon

21

anterograde

away form soma; neurotransmitters, organelles, nutrients

22

retrograde

toward soma; degraded materials to be recycled and extracellular substances

23

axoplasma

-cytoplasm of an axon
-consists of
-few organelles
-cytoskeletal proteins
--form cytoskeleton
--maintain shape
-generate axonal transport

24

axolemma

-plasma membrane of an axon
consists of:
-collaterals: side branches
-telodendria: terminal extensions
-synaptic terminal: contains synaptic vesicles; where neuron contacts pstsynaptic cell

25

structural classification of neurons

anaxonic
bipolar
unipolar
multipolar

26

anaxonic

small neurons
axons can not be distinguished from dendrites
-CNS, especially interneurons that coordinate special senses
no axon

27

bipolar

-several small dendrites converge onto one (one really long dendrite, looks like axon)
-dendrite and axon separated by soma
-unmyelinated
-sensory neurons of special sensory organs

28

unipolar

-pseuod-unipolar
-several small dendrites converge onto one large one
-dendrite and axon continuous
-usually myelinated
-majority of sensory neurons in PNS

29

multipolar

-many dendrites extend from soma
-long axon
-myelinated
-majority of motor neurons in PNS
-spinal interneurons in CNS

30

Afferent Neuons

Have sensory function
-cell body usually are outside CNS
-have receptor ends on dendrites or are associated with receptor cells in sense organs
-carry impulses from peripheral body parts to brain or spinal cord

31

afferent neruon receptors

exteroceptors: touch, temperature, pressure, light, chemicals
proprioceptors: monitor muscle and skeleton position
interoceptors: monitor internal systems (digestion, respiration, urinary)

32

Interneurons

-only in CNS
-classified based on effects
--excitatory
--inhibitory
-most abundant
--link 2 or more neurons

33

efferent neurons

have motor function
-cell body usually are inside CNS
-carry impulses from the brain or spinal cord to peripheral body parts

34

somatic efferent neurons

controls skeletal muscle

35

autonomic/visceral efferent neurons

smooth muscle/glands

36

neuroglial cells in PNS

satellite
schwan cell

37

neuroglial cells in CNS

astrocytes
oligodendrocytes
ependymal cells
microglia

38

Astrocytes

largest and most common
star shaped
functions:
-structure and repair
-metabolism
-regulate ions and nutrition
-guide neurons to targets
-form blood-brain barrier

39

oligodendrocytes

like astrocytes but smaller
functions
-form myelin in CNS
-sequester debris

40

Microglia

-smallest and least common
-derived from myeloid cells
functions:
-help support neurons
-phagocytosis
-increase in number during injury or disease

41

ependymal

-columnar/cuboidal
-microvilli on luminal surface
-joined by gap junctions
functions:
-help produce cerebrospinal fluid
-form porous layer
-monitor CSF composition

42

satellite

associated with soma
assist with exchange of nutrients
isolates neuron from extraneous stimuli

43

schwann cells

produce myelin in PNS
encloses axons of longer peripheral nerves
functions:
-support neurons
-prevent contact
-myelinate large PNS axons (myelin sheath)

44

unmyelinated axons

-appear gray
-many axons associate with a single schwann cell
-CNS: no glial cells

45

myelinated

-appear white
-CNS: oligodendrocytes myelinate part of several axons
-PNS: schwann cell myelinates part of one axon

46

myelin structure

-myelin
-neurilemma
-nodes of ranvier

47

myelin

plasma membrane of schwann cell wrapped around axon

48

neurilemma

part of schwann cell that contains cytoplasm

49

nodes of ranvier

gaps in myelin sheath

50

myelination process

starts at week 14 and completed by age 2-3 years

51

myelin functions

isolate axons
increase rate of action potential

52

regeneration of nerve fibers: PNS

can regenerate a fraction of axons
-schwann cells participate in process
-called wallerian degeneration

53

wallerian degeneration

regeneration of PNS axons

54

steps of nerve regeneration

1. injury separates axon from cell body
-distal portion of axon will deteriorate along with myelin sheath
2.macrophages clean up
-some schwann cells remain
-get thin basement membrane and layer of CT around schwann cells
3. forms hollow tube leading to original connection of axon
-proximal end sprouts
-sprout may grow into tube
4. remaining schwann cells produce new myelin around growing axon
-new axon grows 3-4mm/day

55

repair in CNS

more limited
-degeneration occurs after injury
-oligodendrocytes do not proliferate
-proximal end sprouts but has no tube to follow
-astrocytes produce scar tissue and chemicals blocking regrowth
-generally results in paralysis

56

irritability

ability to respond to stimuli

57

excitability

ability to transport and impulse

58

action potential

an electrical impulse changing the permeability of a membrane

59

nerve impulse

AP moving down an axon
-impulse travels faster when:
--axon is myelinated
--has a larger diameter

60

synapse characteristics

functions as control/transmission point
site of communication between
-sensory structure and neuron
-neuron and effector
-2 neurons
-any two cells with gap junctions

61

electrical synapse

-gap junctions cause the exchange of charged ions between two cells
-communicating charge through ions

62

chemical synapse: definition

chemicals are released by one cell and travel to another

63

chemical synapses: about

-synaptic vesicles house neurotransmitter
-only exist in the presynaptic cell
-release neurotransmitter into the synaptic cleft
-receptors on post-synaptic membrane register the neurotransmitter
-proliferates AP from one cell to the next
-communication in one direction only
-only axons have synaptic vesicles

64

steps at chemical synapse

1. AP reaches synaptic knob of presynaptic neuron
2. neurotransmitter released
3. neurotransmitter crosses cleft and binds to receptors in post-synaptic membrane
-change in permeability results, can be excitatory or inhibitory
4. neurotransmitter is then removed from synaptic cleft
-permeability returns to original state

65

neuronal pools

-receive impulses from afferent fibers (input)
-impulses carried away on efferent fibers (output)
-afferent fibers can branch manny times as they enter a pool

66

types of neuronal pools

convergence
divergence
serial processing
parallel processing
reverberation

67

serial processing

one neuron to another in series

68

divergence

when impulse leaves a pool, it may spread into several output fibers
-allows impulse to be amplified

69

convergence

single nerve in pool may receive impulses from 2 or more incoming fibers
-if lead to same nerve they are said to converge
-allows summation of impulses from different sources

70

parallel processing

processing information from several neurons at once

71

reverbration

positive feedback continues activity of circuit
-enhances signal so happens repeatedly
-promote a behavior, keep responding same way

72

facilitation: threshold

-one neuron may receive either excitatory and inhibitory stimuli from multiple neurons
-the net effect of all this input results in a net charge. if this charge is positive enough it will result in AP
-this point where AP can be produced is known as threshold

73

facilitaiton: facilitated

if a neuron is excited, but still below threshold:
-no impulse, but nerve is more excitable to next impulse
-nerve is said to be facilitated
whole system allows for multiple sources to manage nervous system

74

CNS structures

nuclei
center
tracts

75

nuclei

collection of neuron cell bodies

76

center

collection of neuron cell bodies working together

77

tracts

bundles of axons

78

PNS structures

ganglia
nerves

79

ganglia

collection of neuron cell bodies

80

nerves

bundles of axons