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neural tissue Flashcards

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1
Q

what are the anatomical divisions of the nervous system?

A

the CNS and the PNS

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2
Q

what are the functional divisions of the PNS?

A

the afferent division brings sensory information to the CNS from receptors in peripheral tissues and organs

the efferent division carries motor commands from the CNS to muscles, glands & adipose tissue (effectors)

SAME

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3
Q

what are the components of the efferent division of the PNS and what effectors do they regulate?

A

the SNS (controls both voluntary and involuntary contractions of the skeletal muscles) and the ANS (regulates smooth muscle, cardiac muscle, glandular secretions and adipose tissue at the subconscious level)

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4
Q

how is the ANS divided?

A

into the sympathetic and parasympathetic divisions

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5
Q

name the effectors of the ANS

A

smooth muscle
cardiac muscle
glands
adipose tissue

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6
Q

name the structural components of a typical neuron

A

the cell body, the dendrites and the axon

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7
Q

compare presynaptic and postsynaptic cells

A

a presynaptic cell is usually a neuron

a postsynaptic cell can be a neuron or another type of cell such as a skeletal muscle fibre or gland

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8
Q

what are the functional classifications of neurons? what are the functions of each type?

A

sensory neurons transmit impulses from peripheral receptors to CNS

motor neurons transmit impulses (commands) from CNS to peripheral effectors

interneurons analyse sensory inputs and coordinate motor outputs

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9
Q

what is a ganglion?

A

a collection of neuron cell bodies in the PNS

it’s a little bulge, it’s where the synapses are

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10
Q

what are the three types of sensory receptors?

A

interoceptors
proprioceptors
exteroceptors

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11
Q

name the glial cells of the CNS

A

ependymal cells
microglia
astrocytes
oligodendrocytes

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12
Q

which neuroglia appear in increased numbers in a person with a brain infection?

A

microglia - they are small mobile cells that remove cellular debris, wastes and pathogens by phagocytosis

they’re related to macrophages and monocytes

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13
Q

describe the function of ependymal cells

A

they form an epithelium known as the ependyma which lines a fluid filled passageway in the CNS

it’s known as the central canal in the spinal cord and the ventricles in the brain

the cavity is filled with CSF; ependymal cells help to produce, monitor and circulate the CSF

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14
Q

which glial cell protects the CNS from chemicals and hormones circulating in the blood?

A

astrocytes maintain the blood-brain barrier as well as creating a 3D framework for the CNS and regulating the interstitial environment

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15
Q

contrast the white matter and grey matter in the CNS

A

white matter dominated by myelinated axons

grey matter is areas dominated by cell bodies, dendrites, unmyelinated axons

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16
Q

what are the neuroglia of the peripheral nervous system? what are their roles?

A

satellite cells - surround neuron cell bodies in ganglia and regulate the environment (like astrocytes in the CNS)

Schwann cells - myelinate peripheral axons or else wrap around an axon to protect it without myelinating it

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17
Q

what type of compounds can easily cross the blood-brain barrier?

A

lipid soluble compounds (oxygen, carbon dioxide, lipids, ammonia)

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18
Q

define nerve fibre

A

the axon of a neuron

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19
Q

why is a CNS neuron not usually replaced after it is injured?

A

most CNS neurons lack centrioles and cannot divide

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20
Q

is the grey matter on the outside or the inside of the brain?

A

the outside

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21
Q

where are most interneurons found?

A

in the CNS

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22
Q

define soma

A

neuron cell bodies

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23
Q

what percentage of neurons do inerneurons make up?

A

about 99% of all neurons

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24
Q

what does grey matter do?

A

processes information

grey matter = computer
white matter = cables

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25
Q

what are the major components of the CNS?

A

the brain and spinal cord

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26
Q

what is the role of interneurons?

A

they’re responsible for the analysis of sensory inputs and coordination of motor outputs

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27
Q

what is a sensory neuron also known as?

A

an afferent neuron

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28
Q

in which part of the nervous system does Wallerian degeneration occur and what does it involve?

A

the PNS

involves the repair of damaged nerves but often fails to restore full function

limited regeneration can also occur in the CNS but it’s more complicated there

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29
Q

describe the difference between an action potential and a graded potential

A

action potentials are changes in the transmembrane potential that propagate along the membrane

graded potentials are changes in the transmembrane potential that cannot spread far from the initial site

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30
Q

define membrane potential

A

the unequal charge distribution between the inner and outer surfaces of the plasma membrane

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31
Q

what is another name for a graded potential?

A

a local potential

32
Q

what is the simplest form of information processing in the nervous system?

A

the integration of stimuli by an individual cell

33
Q

what is the resting membrane potential?

A

the resting membrane potential is the membrane potential of a normal, unstimulated cell

34
Q

what units are the electrical potential measured in?

A

volts (mV for cells) (millivolts)

35
Q

what happens at the sodium-potassium exchange pump?

A

three sodium out/ two potassium in to maintain a stable resting membrane potential

36
Q

what is the resting membrane potential of a neuron?

A

-70 mV

37
Q

what effect would decreasing the concentration of extracellular potassium ions have on the resting membrane potential of a neuron?

A

it would cause more potassium to leave the cell via leak channels, making the transmembrane potential of the nerve more negative

38
Q

list the three types of gated ion channels found in neurons

A

chemically gated ion channels

voltage gated ion channels

mechanically gated ion channels

39
Q

under what conditions do each of the gated ion channels found in neurons work?

A

chemically gated channels operate when they bind to specific chemicals eg ACh receptors at the neuromuscular junction

voltage-gated channels open or close in response to changes in the membrane potential

mechanically gate channels operate in response to mechanical stimuli that physically distort the neuron’s membrane surface - important in many sensory receptors

40
Q

define gated ion channels

A

active channels in the plasma membrane that open or close in response to specific stimuli

41
Q

define graded potential

A

a change in the membrane potential that cannot spread far from the site of stimulation

42
Q

what kinds of channels do resting membrane potential, graded potential and action potential depend on?

A

resting membrane potential depends on leak channels

graded potential depends on chemically gated ion channels

action potential depends on voltage-gated ion channels

43
Q

describe the all-or-none principle in membrane potential

A

a given stimulus triggers either a typical action potential or no action potential at all - action potentials are always identical

44
Q

what factor accounts for the local currents associated with action potentials?

A

movement of sodium ions parallel to the inner and outer surfaces of the plasma membrane when chemically gated sodium channels have opened

45
Q

are the positive ions on the inside or outside of the cell at resting potential?

A

Negative on the iNside

pOsitive on the Outside

46
Q

do potassium ions freely diffuse out of the neural cell?

A

no

they pass through leak channels or are transported via the sodium-potassium pump (Na/K pump)

47
Q

which positively charged ions are found more on the outside of a neuron at rest?

A

sodium

48
Q

which positively charged ions are found more on the inside of a neural cell when it’s at rest?

A

potassium

49
Q

do sodium ions freely diffuse into the neural cell?

A

no

via leak channels and the sodium/potassium pump

50
Q

what makes a neuron negatively charged compared to the ECF?

A

negatively charged proteins on the inside

the sodium/potassium pump helps to maintain the balance

51
Q

what is the threshold for an action potential?

A

-55 mV

52
Q

define repolarisation

A

the return of the transmembrane potential to the resting potential after the cell has been depolarised

53
Q

name the types of cells that are capable of producing action potentials

A

excitable cells

  • neurons
  • muscle cells

(only in the axons of neurons)

54
Q

define what is meant by depolarisation

A

a shift from the resting membrane potential towards a more positive potential

55
Q

list the events involved in the generation and propagation of an action potential

A
  1. depolarisation to threshold
  2. activation of sodium channels and rapid depolarisation
  3. inactivation on sodium channels and activation of potassium channels
  4. closing of potassium channels
56
Q

compare the absolute refactory period with the relative refractory period

A

the refractory period is the time between the initiation of an action potential and the restoration of the normal resting potential

absolute refractory period: the membrane cannot respond to further stimulation, no matter how strong

relative refractory period: membrane can only respond to larger-than-normal stimulus

57
Q

define continuous propagation and saltatory propagation

A

continuous propagation happens along an unmyelinated axon; action potential affects every portion of membrane surface

saltatory propagation: relatively rapid propagation between successive nodes of a myelinated axon

58
Q

what’s the relationship between myelin and the propagation speed of action potentials

A

myelin greatly increases propagation speed

59
Q

what is a synapse?

A

a specialised site where the neuron communicates with another cell

60
Q

describe the components of a synapse

A

presynaptic cell

postsynaptic cell

neurotransmitters

synaptic cleft

61
Q

what are the chemical messengers released at the synapse called?

A

neurotransmitters

but penguin professor refers to them as neurocrines (any chemical secreted by a neuron); the term neurocrines includes NTs but also neurohormones and amino acids

62
Q

what is the stimulus for the exocytosis of a neurotransmitter into the synaptic cleft?

A

an influx of calcium ions into the presynaptic nob

63
Q

contrast an electrical synapse with a chemical synapse

A

in a chemical synapse, a neurotransmitter crosses the synaptic cleft

electrical synapse: membranes of pre and postsynaptic cells are joined together by gap junctions

64
Q

define excitatory postsynaptic potential and inhibitory postsynaptic potential

A

EPSP - graded depolarisation of a postsynaptic membrane by a NT released by a presynaptic cell

IPSP - graded hyperpolarisation of a postsynaptic membrane after the arrival of a NT

65
Q

define hyperpolarisation

A

a shift from the resting potential in which the transmembrane potential becomes more negative

66
Q

what is the term for the point in an action potential when the membrane is at its most polarised? what is its voltage then?

A

peak action potential

+30 mV

67
Q

what happens during hyperpolarisation?

A

transmembrane potential drops below -70 mV because potassium channels are slow to close

neuron can only respond to extra strong stimulus

68
Q

what happens during repolarisation?

why does membrane potential change?

A

move back towards PMP

sodium channels are inactivated
potassium channels are activated.

69
Q

what is a reflex?

A

a rapid, automatic response triggered by specific stimuli

70
Q

define spinal reflex

A

spinal reflexes are controlled in the spinal cord and can function without any input from the brain

71
Q

how many pairs of nerves does a typical spinal cord have?

A

31

72
Q

where does the spinal cord end?

A

between vertebrae L1 and L2 (cord is not as long as the vertebral column)

73
Q

describe the gross anatomical features of a cross section of the spinal cord

A
  1. the anterior median fissure - a deep groove along the anterior surface
  2. the posterior median sulcus - a shallow longitudinal groove
  3. white matter - dominated by myelinated axons
  4. grey matter - cells bodies of neurons, neuroglia, unmyelinated axons (deep to the white matter)
  5. the central canal (containing CSF)
  6. a posterior root of each spinal nerve (contains the axons of sensory neurons)
  7. the anterior root of each spinal nerve (contains the axons of motor neurons)
  8. posterior root ganglia (contains cell bodies of sensory neurons)
  9. spinal nerves (containing the axons of sensory and motor neurons)
74
Q

where do sensory and motor neurons become a single nerve?

A

distal to each dorsal root ganglion

75
Q

via which root does the motor nerve exit the spinal cord?

A

ventral or anterior root (at the front)

76
Q

where are most of the cell bodies of most motor neurons found?

A

in the CNS

77
Q

via which root does sensory information enter the spinal cord?

A

the dorsal (posterior) root

nursing cards (13 decks)

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