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biology > THE NERVOUS SYSTEM > Flashcards

THE NERVOUS SYSTEM Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is the function of the nervous system

A

homeostasis and coordination. employs electrical and chemical means to send messages very quickly from cell to cell

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2
Q

What are the two major subdivisions of the nervous system

A

CNS and PNS

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3
Q

What does the CNS consist of

A

brain and spinal chord

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4
Q

what does the PNS consist of

A

ganglia and nerves

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5
Q

what is a neuron

A

a cell of the nervous system

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6
Q

what is a nerve

A

bundle of nerve fibres (axons) wrapped in fibrous connective tissue

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7
Q

what is the ganglion

A

a knotlike swelling in a nerve where the cell of bodies of neuron are concentrated

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8
Q

what are the subdivisions of the PNS

A
  1. sensory (afferent) division
    i. somatic sensory
    ii. visceral sensory
  2. motor (efferent)
    i. somatic motor
    ii. visceral motor
    a. sympathetic
    b. parasympathetic
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9
Q

what is the sensory (afferent) division

A

carries sensory signals from receptors (sense organs and simple sensory nerve endings) to the CNS

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10
Q

what is the somatic sensory division

A

signal from receptors in the skin, muscle, bones and joints

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11
Q

what is the visceral sensory division

A

signals from viscera of the thorax and abdominal cavities e.g. heart, lungs and stomach

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12
Q

what is the motor (efferent) division

A

carries signals from the CNS to the glands and muscle cells (effectors)

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13
Q

what is the somatic motor division

A

signals to skeletal muscle for voluntary contraction and involuntary somatic reflexes

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14
Q

what is the visceral motor division (autonomic nervous system)

A

signals to glands, cardiac muscle, smooth muscle; involuntary visceral reflects

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15
Q

what is the sympathetic division

A

tends to arouse the body for action e.g. increases heart and respiratory rates, but inhibits digestion
emergency response

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16
Q

what is the parasympathetic division

A

tends to have a calming effect e.g. slowing downtime heart rate, but stimulates digestion
normal everyday conditions

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17
Q

what are the properties of neuron

A
  1. excitability(stability)
  2. conductivity
  3. secretion
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18
Q

how are cells excitable

A

all cells are excitable e.g. they respond to stimuli, but neurons have developed this to the highest level

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19
Q

how are cells conductive

A

stimuli produce electrical signals in neurons that are conducted to other cells at distant locations

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20
Q

secretion of cells

A

electrical signals at the end of nerve fibres cause the release of chemical neurotransmitters

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21
Q

what are the type of neurons

A

sensory (afferent)
interneurons (association neurons)
motor (efferent)

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22
Q

what are sensory (afferent) neurons

A

detection of signals;

neurons conduct signals from receptors to CNS

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23
Q

what are interneurons

A

they lie in the CNS; process, store, retrieve information and make decision ; 90% of all neurons;
they are confined to CNS

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24
Q

what are motor (efferent) neurons

A

signals to muscle and glands;

neurons conduct signals from the CNS to effectors such as muscles and glands

25
Q

what is the structure of a neuron

A
  1. soma/neurosoma/cell body
    i. cytoskeleton-microtubules
    ii. nil bodies- dark staining RER
    iii. no mitosis after adolescence
    iv. inclusions
    v. dendrites
    vi. axon hillcock
26
Q

How big is the soma

A

5-135μm dia

27
Q

what is the cytoskeleton made of

A

neurofibrils (actin)

28
Q

what is inclusions

A

glycogen granules, lipid droplets, melanin, lipofuscion (golden brown pigment produced when liposomes digest worn out organelles, wear and tear granules)

29
Q

what are dendrites

A

receive stimulus and carries it impulses toward the cell body

30
Q

what is the axon hillcock

A

they give rise to the axon

31
Q

What is the structure of a neuron

A
  1. axon/ nerve fibre
    i. may be myelinated
    ii. may have collaterals
    iii. terminal arborisation ending in synaptic knob
    iv. substances are produced in the soma and transported along the axon (axonal transport)- movement from the to the axon is called anterograde transport and the reverse is called retrograde transport
32
Q

how big is the axon

A

1-20μm dia, few mm to 1m in length

33
Q

what is the axon

A

fibre which carries impulses away from cell body

rapid conduction of nerve signals; cyptoplasm= axoplasm; membrane = axolemma

34
Q

what are glue cells called

A

support cells neuroglia

35
Q

What are the neuroglia of CNS

A

oligodendrocytes
epdnymal cells
microglia
astrocytes

36
Q

what are the neuroglia of PNS

A

Schwann cells

satellite cells

37
Q

what is oligodendrocytes

A

form myelin in brain and spinal cord

38
Q

what is myelin

A

a mixture of proteins and phospholipids forming a whitish insulating sheath around many nerve fibres

39
Q

what is the epdnymal cells

A

line cavities of brain and spinal cord; secrete and circulate cerebrospinal fluid

40
Q

what is microglia

A

phagocytise and destroy microorganisms; foreign matter, and dead nervous tissue

41
Q

what are astrocytes

A

they cover brain surface and non synaptic regions of neurons; form supportive framework in CNS; induce formation of blood brain barrier; nourish neurons; produce growth factors that stimulate neurons; communicate electrically with neurons and may influence synaptic signalling; remove K+ and some neurotransmitters from ECF of brain and spinal cord; help to regulate composition of ECF; form scar tissue to replace damaged nervous tissue

42
Q

what are the neuroglia of PNS

A

Schwann cells and satellite cells

43
Q

What are the Schwann cells

A

they are cells which produce myelin or fat layer in PNS

form neurilemma around all PNS nerve fibres and myelin around most of them; aid in regeneration of damaged nerve fibres

44
Q

what are the satellite cells

A

surround somas of neurons in the ganglia; provide electrical insulation and regulate chemical environment of neurons

45
Q

what is myelination

A

it provides insulation along axons
it increases nerve conduction speed by approx an order of magnitude
•2-4μm dia fibre- 0.5 to 2m/s unmyelinated and 3 to 15m/s myelinated
•20μm fibre myelinated 120 spiral outwards
Schwann cells in PNS- spiral outwards
Oligodendrocytes in CNS- spiral outwards

46
Q

what is the resting membrane potential

A
  1. membrane potential = the pd between the ICF and ECF, about -70mV at rest= resting membrane potential
  2. origin of RMP
    i. membrane is most permeable to K+
    Imagine k+ only in ICF at start- this would diffuse out down concentration gradient
    Non diffusible anions in ICF attract K+ back
    At equilibrium K+ is 40 x more concentrated in ICF and ECF- this would give RMP at -90mV
    Na+ is 12 x more concentrated in ECF than ICF- this diffuses down concentrated gradient into cell and reduces negative charge in ICF
    Therefore K+ leaks out and Na+ leaks in
    Na+ K+ pump- this consumes 1 ATP to pump 3Na+ out and 2K+ in- contributes -3mV to RMP; accounts for 70% energy requirement of nervous system
    Net effect is RMP of -70mV
47
Q

what is local potential

A

typically beings at dendrite- stimulus causes the opening of Na+ channels; membrane potential becomes less negative- depolarisation; current traceless to the neuron’s trigger zone; can be inhibitory- hyperpolarisation

48
Q

what is action potential

A

it typically beings at trigger zone- produced by voltage regulated ion gates; high density go theses at trigger zone; strong local potentials can trigger that action potential

49
Q

how does the action potential work

A
  1. Na+ ions arrive at the axon hillock and cause a depolarisation
  2. the membrane potential rises above -55mV - the threshold potential
  3. voltage regulated Na+ gates open quickly and Na+ flows into cell to cause rapid depolarisation; slower K+ gates also open
  4. At 0mV, Na+ gates colse- maximum depolrisation is reached at +35mV
  5. Slow k+ gates are fully open and K+ moves out of cell to cause repolarisation
  6. More k+ leaves than na+ enters so hyper polarisation occurs
  7. membrane potential is restored to RMP
50
Q

what is the difference between depolarisation and repolarisation

A

The main difference between depolarization and repolarization is that the depolarization is the loss of resting membrane potential due to the alteration of the polarization of cell membrane whereas repolarization is the restoration of the resting membrane potential after each depolarization event.

51
Q

what is refractory period

A

period of restumulation

52
Q

myelinated axonal conduction

A
  1. APs ont at nodes of Ranvier
  2. AP appears to jump from node to node across the internodes- saltatory conduction
  3. Faster than unmyelinated conduction
53
Q

what is the myelin sheath

A

dense lipid layer which insulates the axon- makes the axon look gray

54
Q

what is the node of ranvier

A

gaps or nodes in the myelin sheath

55
Q

what is neurilemma

A

thin sheath around a nerve axon (including myelin where this is present)

56
Q

what is the somatic nervous system made up of

A

spinal nerves and peripheral nerves

57
Q

astrocytes

A

found in blood brain barrier; have a role in transferring nutrients from capillaries to deeper regions of brain

58
Q

what is depolarisation

A

when it becomes less negative

biology (9 decks)

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