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Histology: BMS 6031 > Muscle and Nerve > Flashcards

Muscle and Nerve Flashcards

1
Q

What are the muscle types?

A
  • Skeletal
  • Smooth
  • Cardiac
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2
Q

What are the characteristics of skeletal muscle?

A

Strong and quick response
Voluntary
Striated muscle: fibrils composed of sarcomeres
Large long fibers with many peripheral nuclei
Fibers individually innervated
Fibers composed fibrils

Site of somatic innervation

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3
Q

What are the characteristics of cardiac muscle?

A

Strong and quick response
Involuntary
Short, thick, branching cells
Typically mono-nucleate
Striated muscle cells, sarcomere structurally identical to skeletal muscle
Cells attached end-to-end by intercalated disks (arrows)
Appear as particularly dark cross-striations in cardiac muscle (arrows)
Myocytes not individually innervated, no somatic innervation

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4
Q

What are the characteristics of smooth muscle?

A

Weak and slow response
Involuntary
Non-striated muscle
Fusiform, mono-nucleated cells surrounded by an external lamina.
Located in walls of all hollow organs – digestive tract, blood vessels, urinary bladder, bronchial tree

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5
Q

Label the parts

A
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6
Q

What are myofibers made of?

A

Myofibrils

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7
Q

What are myofibrils made of?

A

Myofilaments

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8
Q

What are myofilaments made of?

A

Repeating functional units called sacromeres

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9
Q

Sacromeres contain what two filaments?

A

Thick filaments: Myosin II

Thin filaments: Actin

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10
Q

Label the parts

A
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11
Q

Label the parts

A

MF, myofiber
MNF, myofiber nuclei
N, nucleus
C, capillary

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12
Q

What lines define the sacromere?

A

The Z-Lines

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13
Q

What is the Z-Line made of?

A

α-actinin - it anchors actin filaments.

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14
Q

What is the I band made of?

A

Primarily thin filaments and titin, a large protein that prevents over-stretching of sarcomere.

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15
Q

Label the parts

A
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16
Q

What is the A band made of?

A

Thin filaments (actin) and thick filaments (myosin)

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17
Q

What is the H band made of?

A

Only thick filaments (myosin)

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18
Q

What does the M band do?

A

It is the anchor for the thick myosin filaments

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19
Q

Label the parts

A

My, myofibrils
M, myofibers
E, endomysium
N, nucleus

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20
Q

What two binding sites are on the Myosin head?

A

ATP and Actin

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21
Q

What is troponin?

A

A complex of three proteins that ar bound to the tropomyosin molecule.

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22
Q

What are the three proteins in the troponin complex and what do they do?

A

Troponin I, C, and T

Troponin C: binds Ca2+ and is found only in striated muscle
Troponin T: binds the complex to tropomyosin.
Troponin I: inhibits the binding of myosin to actin

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23
Q

What are the two main part of the nervous system?

A

CNS: Central Nervous System

PNS: Peripheral Nervous System

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24
Q

What makes up the CNS

A

Brain and Spinal Cord

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25
Q

What makes up the PNS?

A

Nerves (cranial and spinal)

Ganglia

Plexus (enteric)

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26
Q

What are the three functions of the nervous system?

A

Sensory: Afferent neurons and receptors

Integrative: Interneurons - neurons that connect other neurons.

Motor: Efferent motor nuerons (effect muscles)

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27
Q

What are the three parts of the PNS?

A

Somatic: sensory neurons as well as voluntary motor neurons.

Autonomic: sensory as well as involuntary motor neurons.

Enteric (“brain of the gut”): sensory neurons - associated with entire GI tract, motor neurons - effectors in GI tract (e.g., smooth muscle, glands). This regulates GI activies, independent of CNS

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28
Q

What are the two divisions of the autonomic PNS?

A

Sympathetic and Parasympathetic

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29
Q

What is a ganglion?

A

A group of nerve cell bodies outside of the CNS

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30
Q

What connects to a ganglion and what it is’t purpose?

A

A preganglionic fiber connects from the CNS to the ganglion and a post ganglionic fiber connects from the ganglion to the effector.

The ganglion functions as a junction box for connecting the two neuron ANS.

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31
Q

What type of ganglia are in the sympathetic ANS?

A

Chain ganglia and prevertebral ganglia

32
Q

What type of ganglia are in the parasympathetic ANS?

A

Parasympathetic ganglia

33
Q

What type of ganglia are in the gut region?

A

Enteric ganglia

34
Q

What is the difference between a neurotransmitter and a neurohormone?

A

Neurotransmitters are released into the synaptic cleft and neurohormones are released into the blood.

35
Q

What are the parts of a neuron cell body?

A

Cytoplasm - neurofilaments (extend into cell processes)
Organelles - nucleus, rER (Nissl bodies or substance)
Plasma membrane - spines (small projections)

36
Q

How many axons are there per cell body

A

One: Has an output function

37
Q

How many dendrites per cell body?

A

Many: Has an input function

38
Q

Label the parts

A
39
Q

What organelles does a neuron cell body contain?

A

All the usual eukaryotic cell organelles:

nucleus, Golgi, mitochondria, rER, sER, lysosomes, and lipofuscin.

40
Q

What is another name for rER in neurons?

A

Nissl substance or Nissl bodies

41
Q

What is another name for intermediete filaments in neurons?

A

Neurofilaments

42
Q

What is this?

A

Neuron rER

43
Q

What is this and what are the arrows pointing to?

A

Axon crosscut and longitudinal section.

MT = Microtubule

NF = Neurofilaments

44
Q

Label the parts

A
45
Q

What is anterograde transport

A

Moves cargo from soma (cell body) to periphery

(from MT- to MT+ end)

46
Q

What is retrograde transport?

A

Moves cargo from axon and dendrites (periphery) to soma

from MT+ end to MT- end

47
Q

There are two types of transport motors:

What are they called?

Which way do the transport cargo?

How do they get energy to transport?

A

Kinesin family (to + end)

Dynein family (to – end)

hydrolyse ATP

48
Q

What is slow transport?

A

Anterograde transport of cytoskeleton proteins

49
Q

What is fast transport?

A

Anterograde and retrograde transport of vesicles (neurotransmitters), mitochondria, other cargo along microtubules, requires ATP

50
Q

What are the support cells of the nervous system called?

A

Neuroglia

51
Q

What are the characteristics of the Neuroglia?

A

Much more numerous than neurons

Generally smaller cell size than neurons

Make up about half the volume of nervous tissue

Capable of cell division

Six main types of cells

52
Q

What are the types of neuralgia in the CNS and what do they do?

A

Astrocytes – large, numerous cells with multiple processes
Oligodendrocytes – smaller, less numerous cells with fewer processes
Microglia – small cells with thin processes with spikelike projections
Ependymal cell – cuboidal to columnar layer of cells with cilia and microvilli

53
Q

What are the types of neuralgia in the PNS and what do they do?

A

Schwann cells – cells that myelinate or enclose unmyelinated axons

Satellite cells – surround cell bodies in ganglia including enteric ganglia

54
Q

What type of junctions are in the epithelium of the blood / brain barrier?

A

tight junctions

55
Q

What kind of molecules can cross the blood / brain barrier?

A

Lipid soluble and gases - they cross by diffusion.

56
Q

How do other substances cross the blood / brain barrier epithelium?

A

My receptor mediated endocytosis.

57
Q

What is this?

A

An unmylenated axon crosscut

58
Q

What is the myelin sheath made of?

A

Multiple concentric layers of Schwann cell plasma membrane

59
Q

What about the schwann cell plasma membrane improves its insulator function?

A

It is 80% lipids

60
Q

What components does the schwann cell secrete?

A

External Basal Lamina

61
Q

What is this and what is labeled?

A

Cross section of a mylenated axon.

BL = Basal Lamina

Mit = Mitochondria

MT = Microtubules

62
Q

What are two types of afferent sensory receptors?

A

Pacinian corpuscle – Large (~1mm) pressure and vibration receptors associated with myelinated axon.

Meissner’s corpuscles are long (~150 µm), fine touch frequency receptors in dermal papillae that are associated with myelinated axons

63
Q

What is this?

A

A pacian corpuscle

64
Q

What is this?

A

Meissners Corpuscle

65
Q

What are the steps of motor innervation?

A
  1. Nerve impulse arrives at the neuromuscular junction
  2. Acetylcholine (ACh) released from nerve terminal binds to nicotinic ACh receptors on sarcolemma
  3. Opens Na+ channels, leading to depolarization of sarcolemma and initiation of action potential
  4. Action potentials spread across membrane and into T-tubules
  5. Activation of voltage-sensor proteins
  6. Ca2+ channels open in adjacent terminal cisternae of the sarcoplasmic reticulum
  7. Ca2+ is released from the sarcoplasmic reticulum
  8. Ca2+ binds to TnC of the troponin complex
  9. Contraction cycle is initiated and Ca2+ is returned to the sarcoplasmic reticulum
66
Q

What is the sacrolema?

A

The cell membrane of a muscle cell. Surrounds the muscle fiber made of myofilaments and myofibrils.

67
Q

What are the invaginations in the sacrolema of a muscle fiber (cell)?

A

They are called T-tubules TT

68
Q

What is the smooth reticulum called that abuts the TT?

A

It is called Sarcoplasmic reticulum.

69
Q

What is a triad made of?

A

1 TT and 2 SR

70
Q

How many triads per sacromere?

A

2

71
Q

What happens at each step?

A
72
Q

What are the events of striated muscle contraction?

A
  1. Nerve impulse travels down axon
  2. Acetylcholine released into synaptic cleft, depolarizing local sarcolemma
  3. Voltage gated Na+ channels open, Na+ enters muscle cell
  4. Depolarization spreads over entire sarcolemma and into T-tubule
  5. Voltage sensor proteins in T-tubules change conformation
  6. Ca2+ release channels in sarcoplasmic reticulum are activated by conformation change
  7. Ca2+ is rapidly released from sarcoplasmic reticulum into sarcoplasm
  8. Ca2+ binds to the TnC subunit of troponin (contraction cycle is initiated)
  • ATP binds to myosin releasing it from actin
  • Myosin heads break down ATP into ADP and Pi
  • Bending of the ADP-Pi-myosin head to an actin binding site that has been opened by Ca2+ binding to TnC
  • Release Pi to form bind stronger to the actin and allow the myosin to spring back to the unbent position
  • Power stroke is the return of the myosin head to its unbent position forcing movement of the thin filaments
  • ATP binds to myosin releasing it from actin to then repeat the cycle
  1. Ca2+ is sequestered into the sarcoplasmic reticulum
73
Q

What anchores thin filaments in smooth muscle?

A

Dense bodies

74
Q

What are the events of smooth muscle contraction?

A
  • Contraction can be initiated by mechanical, electrical, and chemical stimuli (all result in increased intracellular Ca2+ )
  • Increase in free intracellular calcium can result from either increased flux of calcium into the cell through calcium channels or by release of calcium from internal stores (e.g., sarcoplasmic reticulum).
  • Free Ca2+ binds to a special Ca2+ binding protein (calmodulin) … Ca2+ -calmodulin complex activates myosin light chain kinase (MLCK) that phosphorylates myosin light chains in the presence of ATP
  • Myosin light chain phosphorylation leads to cross-bridge formation between the myosin and the actin, leading to contraction
75
Q

Contrast smooth muscle and striated (cardiac / skeletal) muscle contraction.

A
  • Contraction of skeletal muscle is regulated by Ca2+ binding to TnC, which opens the myosin binding groove on actin.
  • Contraction of smooth muscle is regulated by Ca2+ binding to calmodulin, which activates MLCK

Histology: BMS 6031 (7 decks)

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