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Neurophysiology exam > Neurophysiology exam > Flashcards

Neurophysiology exam Flashcards

1
Q

what does the CNS consist of?

A

brainstem, spinal cord, cerebellum, subcortical nuclei, cerebral cortex

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2
Q

soma

A

cell body, contains nucleus and nucleolus, and cytoplasm around nucleus

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3
Q

processes on neurons

A

axons and dendrites

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4
Q

dendrite

A

net electrical impulse travels TO cell body

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5
Q

axon

A

net electrical impulse is AWAY from cell body. Often myelinated.

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6
Q

fiber

A

process plus sheath (axon and myelin)

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7
Q

synaptic terminal

A

where presynaptic neuron connects with postsynaptic one

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8
Q

what determines the postsynaptic neuron response

A

citation or inhibition depends on the chemical released at the synaptic terminal

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9
Q

what must the post synaptic cell express in order for “communication” at the synaptic terminal to be successful

A

receptors

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10
Q

What does the PNS consist of?

A

dendrites and cell bodies of primary sensory neurons, axons of motor neurons from spinal cord & brain stem that terminate on muscle cells, and major parts of autonomic nervous system

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11
Q

autonomic nervous system

A

part of CNS and PNS, responsible for unconscious regulation of body functions, divided into sympathetic and parasympathetic

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12
Q

what do the sympathetic and parasympathetic nervous systems have in common?

A

both have a 2-neuron connection (pre-ganglionic and post-ganglionic neurons) from the CNS to the target tissue

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13
Q

where do most organs and glands receive fibers from?

A

both the sympathetic and parasympathetic nervous system (except adrenal medulla, some sweat glands, and arrector pili muscles)

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14
Q

does the ANS receive sensory input?

A

yes, influenced by higher brain centers- hypothalamus

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15
Q

Can CNS neurons regenerate?

A

NO in mammals
- no mitotic organelles

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16
Q

Can PNS neurons regenerate?

A

YES
under certain circumstances

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17
Q

1st layer of protection for brain and spinal cord

A

skull and vertebrae

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18
Q

3 layers that cover the CNS

A

known collectively as meninges
1. dura mater - external most & toughest
2. arachnoid membrane - more delicate
3. pia mater - more delicate

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19
Q

glial cells

A

supporting cells within nervous system

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20
Q

four classes of glia in the CNS

A

microglia, ependymal cells, astrocytes, oligodendrocytes

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21
Q

glial cells in PNS

A

satellite cells and neurolemmocytes (Schwann cells)

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22
Q

Schwann cells

A

IN PNS, wrap nerve processes with myelin

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23
Q

oligodendrocytes

A

IN CNS, produces myelin for several nerve processes. also surround neurons in CNS

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24
Q

astrocytes

A

in CNS, cover surface of CNS capillaries to form blood-brain barrier
also protect connections zone between neurons referred to as synapses

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25
Q

in the PNS, what is analogous to astrocytes?

A

satellite cells, they surround cell bodies of sensory neurons

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26
Q

microglia

A

macrophages of CNS

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27
Q

ependymal cells

A

line CSF filled passageways and form barrier between CSF and ventricles and the neuronal/glial layers of CNS

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28
Q

what “environment” do neurons operate in?

A

an aqueous medium that is part of extracellular space within the brain, spinal cord, and PNS
- “salt-water bath”
filled with + charged ions Na, K and CA & negatively charged ions Cl

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29
Q

what influences charged particles like ions

A

concentration gradients and electrical gradients
these two things generate an electrochemical homeostasis

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30
Q

ion channels

A

complexes of proteins that have 2+ structurally similar subunits that form a channel by lining
- can be opened of closed, controlling the flow of specific ions in/out of cell along their concentration gradient
- also act as receptors for various ligands such as NT’s

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31
Q

ion channel features

A

can be selective or non-selective as determined by the molecular structure of the channel
- pore size
- ion filters (highly selective for binding of distinct ions)
- channel gates: gated channels require opening of a gate for ions to go through while closed gates prevents ion passage
(non-gated channels are generally open whereby diffusion of ions though the channels is mostly determined by concentration gradient (& pore size))

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32
Q

What are the characteristics of gated channels that allow changes between open and closed states?

A
  1. kinetics of voltage-dependent (voltage gated) channels is determined by how fast or how slow the gate portion of the channel opens and closes
  2. concentration gradient for an ion
  3. current running through a channel can dictate how rapidly ions move through (current is influenced by membrane voltage)
  4. concentration of a ligand for a gated channel can influence how rapidly the channel is activated or inactivated/ how long it remains open or closed
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33
Q

How are gated ion channels activated?

A
  1. changes in membrane potential
  2. chemical, extracellular, and intracellular ligand
  3. mechanical deformation of their structure (mechanoreceptors)
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34
Q

resting membrane potential

A

-70 mV
electrical potential at which activity within a neuron is at equilibrium
- concentration of ions inside/outside of cell are key determinants

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35
Q

what is open/closed at resting membrane potential

A

K and Cl are OPEN
Na and Ca are CLOSED

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36
Q

what equation allows for calculation of the charge differences established between inside and outside of neurons across membrane

A

nernst equation
- * the larger the gradient = the larger the equilibrium potential

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37
Q

what is the problem with membranes during RMP?

A

To keep equilibrium at RMP, channels must be closed to Na, BUT membranes are leaky to Na. As Na slowly leaks in, it changes electrical potential for K and K is pushed out. So therefore slightly less negative RMP than K+ potential (-70 vs -96)

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38
Q

Due to leakiness & buildup Na IN and K OUT what happens?

A

must be balanced out, Na/K pump maintains Na and K gradients for RMP by actively pumping 3 Na OUT and 2 K IN
- constantly active
- is an ATPase- hydrolyzes ATP to ADP for energy

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39
Q

depolarization

A

membrane potential becomes more positive (relative to -70 mV)

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40
Q

hyperpolarization

A

membrane potential moves from -70 to more negative (closer to K @ 96)

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41
Q

repolarization

A

movement of membrane potential from either depolarized or hyperpolarized back to RMP

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42
Q

what defines a graded potential

A

when the membrane is depolarized up to -40, or more negative than -70
(if depolarized more + than -40 = AP)
small potentials and subthreshold

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43
Q

what are the characteristics of graded potentials

A
  • generated by sub-threshold stimuli and small potentials that result in depolarization of the membrane up to -40 mv (hyper-polarizing currents)
  • can be caused by a small local change in membrane permeability to ions
  • either depolarizing or hyper polarizing depending on charge of the ions being moved in and out of the affected neuron
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44
Q

How would the following affect a graded potential:
opening of Na channels

A

results in movement of Na into cell and down its concentration gradient and electrical gradient resulting in DEPOLARIZING graded potential

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45
Q

How would the following affect a graded potential:
opening of K channels

A

results in movement of K OUT of cell and down its concentration gradient (towards equilibrium) resulting in HYPERPOLARIZING graded potential

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46
Q

An important characteristics of graded potentials are ability to be added together, what are these 2 types?

A

temporally = 2 + of the same stimuli at slightly different times
spatially = 2 + of different stimuli at different location but applied at same times

both instances result in a larger potential
- receive signal from pre-synaptic neuron, summate, AP if great enough

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47
Q

what does decremental mean in terms of graded potentials?

A

graded potentials decrease in size a short distance from the site of the stimulus
therefore graded potentials are generally used for local signaling within small regions of a neurons membrane

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48
Q

how does a graded potential propagate down a membrane?

A

so any change in membrane permeability will result in ion flow in/out of cell, which will cause a change in membrane potential. the potential difference causes local current flow (direction of movement of positive charges). the influx of positive charge (Na= depolarizing potential), repels positive charges and attracts negative charges. this causes positive charged to move in both directions away from the point of ion entry

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49
Q

graded potentials

A
  • local currents
  • die out quickly
  • within short distance from point of stimulus
  • ions diffuse passively and re-equibrilate across membrane
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50
Q

what type of receptor neurons can only produce graded potentials

A

rods and cones in retina

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51
Q

T/F: most neurons use graded potentials for generating action potentials

A

true

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52
Q

ligand gated channels

A

channel where activation is mediated through binding of chemical, extracellular, and intracellular ligands
- cation permeable Ach receptor

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53
Q

how are graded potentials generated?

A

By means of ion channels opening and closing
are propagated by means of ion channels opening and closing due to changes in electrical potential in adjacent areas of the membrane

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54
Q

how can a graded potential lead to action potentials

A

summation of subthreshhold graded potentials (largely due to Na) leads to the all or none activation of an AP

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55
Q

what are some key characteristics of action potentials?

A

AP don’t diminish
rapid/shortlived - msecs
all or none
magnitude always the same
cannot be summated
frequency can be increased or decreased to reflect magnitude of signal

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56
Q

what determines where in neuron and how AP are generated?

A

differential sub cellular concentration and distribution of voltage-gated Na channels

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57
Q

where are the most voltage gated Na channels in a neuron

A

axon hillocks
result in area being very sensitive to summated graded potentials and the generation of action potentials

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58
Q

where in the neuron does summation occur

A

dendrite

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59
Q

sub threshold graded potentials

A

stimuli underlying an action potential
usually due to opening of ligand-gates or non-gated Na channels

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60
Q

what does summation on graded potentials in the dendrite lead to

A

all or none activation of AP at axon hillock via activation of Na channels

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61
Q

at what mV does the neuronal membrane reach for an action potential to be generated

A

-40 mV

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62
Q

what determine/ influence the threshold for an action potential

A
  1. increase N and outward K currents before reaching threshold, results in increase in membrane potential away from rest. Na conductance is unstable when nearing AP threshold and so a minor increase in Na ions causes AN EXPLOSION of inward Na current which causes an AP (evolution)
  2. changes in RMP can increase or decrease the threshold, hyper polarization will require more Na ions to reach threshold. depolarization will require less Na ions
  3. Ca++ outside cell can influence because of its effects on charged particles on cell surface . Can also BLOCK Na and K channels thereby making changes in membrane potential more difficult. Increase extracellular Ca++ will increase threshold and decreases in Ca++ extracellularly will decrease threshold
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63
Q

what is responsible for the RISING PHASE of the action potential

A

Na channels are activated rapidly and the sudden flow of Na inward

  1. open Na channels
  2. increased permeability of Na
  3. increased Na flow
  4. depolarization
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64
Q

falling phase of action potential

A

relative slow responsiveness of K channels to impulses is the underlying mechanism for the outward flow of + charge and the depolarization of the membrane

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65
Q

action potential sequence of events

A
  • summated graded potentials move the membrane potential towards -40 mV
  • large number of voltage gated Na channels are active rapidly and sudden inward flow of Na is responsible for rising phase (AP)
  • at peak (+59) voltage gated K are activated very slowly and flow of Na slows down and the outward efflux of K results in outward flow of + charge and repolarization of membrane potential
  • special gating by Na channels inhibits consecutive initiation of AP, this secondary-gating blocks Na influx by keeping Na channels in an inactive state for a latent period. this is basis of refractory period and uni-directional propagation of AP
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66
Q

Na equilibrium potential

A

+59

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67
Q

what is the basis of unidirectional propagation of AP

A

special gating by Na channel inhibits consecutive initiation of AP. keeps Na channels in an inactive state for a latent period

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68
Q

myelin

A

80% lipid and 20% protein substance that insulated axons
- in CNS oligodendrocytes myelinate axons
- in PNS Schwann cells myelinate axons; also more elegant and allows for rapid propagation

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69
Q

lipid component of myelin

A

mostly a glycolipid called galactocerbroside

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70
Q

protein component of myelin

A

myelin basic protein (MBP)
myelin oligodendrocyte glycoprotein (MOG)
proteolipid protein (PLP)

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71
Q

how does conduction velocity relate to diameter of axonal fiber

A

conduction velocity increases with increasing diameter of axonal fiber
- fastest = larger diameter & myelinated
- slowest = smallest diameter & unmyelinated

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72
Q

how does an action potential work in unmyelinated nerves?

A

AP at site of stimulus sets up local current flow to adjacent parts of the cell membrane, this causes depolarization of the adjacent membrane to threshold, giving rise to AP at adjacent site. inward Na and outward K keeps occurring at adjacent parts of membrane and thus AP propagates through ionic conductance
even if local current flow is in reverse direction, AP cannot be conducted in reverse direction because the membrane is in refractory period
all or none

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73
Q

microscopic unmyelinated regions between successive myelin wrappings of the axon

A

interfiber nodes
“nodes of ranvier”

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74
Q

What is the function of myelin

A

forms an insulating layer around the axon which prevents leakage or diffusion at all points.

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75
Q

why do action potentials travel much faster in myelinated neurons vs unmyelinated neurons

A

within interferer nodes (where no myelin), there is a high concentration of Na channels which allow for generation of AP’s. Charge rapidly distributes to next interferer node and so AP travel down myelinated axon very rapidly (in comparison to unmyelinated of same diameter and length)

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76
Q

when does myelination occur?

A

perinatal period
axon diameter and myelin sheaths grow during first 2 years of life
may not even be fully mature before adolescence

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77
Q

How does diet relate to the myelination process?

A

Myelination is a metabolically demanding process and therefore young animals need high fat diets

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78
Q

What can disruption of myelin lead to>

A

disorders regarding motor control, hyper excitability, uncontrolled shivering

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79
Q

Multiple sclerosis

A

autoimmune disorder resulting in degeneration of myelin on nerve fibers
results in progressive nerve paralysis

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80
Q

canine shaking pups disease

A

genetic myeline disease
results in decreased weight and size during first 10 days of life, most pups overcome

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81
Q

visna & k9 distemper

A

inflammatory diseases in dogs that affect myelination and nerve conductance
viral infection affects myelin indirectly
ataxia, hyperesthesia (+ sensitive), myoclonus (twitching), paresis (weak), depression

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82
Q

What type of drugs are Na channel blockers?

A
  1. local anesthetics
    - proCAINE, tetraCAINE, lidoCAINE, cocAINE
    act on unmyelinated pain fibers
    blocks AP of free nerve endings so pain is not communicated to CNS
  2. Tetrodotoxin- from puffer fish and some bacteria, block Na too (block multiple NA channels, result in paralysis)
  3. Saxitoxin- in butter clam, produced by cyanobacteria (block multiple NA channels, result in paralysis)
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83
Q

how can calcium levels cause seizures?

A

Ca is a stabilizer of membranes, keeps Na channels closed, so when Ca levels are too low, membrane have a high permeability to Na and nerves can become spontaneously excitable, can leads to muscle spasms and rigidity

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84
Q

synapse

A

specialized junction between 2 neurons by which electrical activity in one neuron influences the other through the secretion of NT at presynaptic axonal terminals and activation of of NT receptors at postsynaptic neurons
electrical signal in presynaptic neuron is converted into a chemical message

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85
Q

what are the most common type of synapses?

A

chemical

also rare examples of electrical synapses for extremely fast communication - cardiac muscle

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86
Q

How do chemical signals translate to electrical signals, and vice versa?

A

E signal @ Pre-syn neuron is converted into chemical message
chemical message affects postsynaptic membrane receptors
chemical message is converted to E signal in post synaptic neuron

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87
Q

what dictates if the outcome of a neurotransmission is excitatory or inhibitory?

A

depends on on NT and type of receptor activated

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88
Q

what does it mean for inputs to converge?

A

at the cellular level, synaptic inputs from multiple axons may converge on one dendrite
neuron may receive info from up to thousands of other neurons

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89
Q

what does it mean for synaptic input to diverge?

A

input can diverge from one neuron via branching of its axons and formation of synapses on multiple dendrites of many recipient neurons

90
Q

synaptic cleft

A

small space that separates the pre-synaptic axon terminal from the membrane of the post-synaptic neurons (dendrites or cell body)

91
Q

what does the entire process of neurotransmission depend on?

A

the specialized vesicles that are packaged with, carry, and secrete NT from presynaptic neuron at synaptic cleft

92
Q

where are NT synthesized?

A

depending on the size, either the soma (LARGE) or within the axonal terminals (SMALL)

93
Q

example of large NT

A

protein/ peptide NT

94
Q

example of small NT

A

glutamate, GABA, Ach, norepi

enzymes responsible for production are in nerve terminal

95
Q

vesicular life cycle

A
  1. NT synthesis & packaging
  2. Vesicular transport to packaging sites
  3. Packaging of NT vesicles - “maturation of vesicle”
  4. Formation of reserve pool of vesicles
  5. Ca++ entry in response to AP
  6. Vesicular mobilization to active site on terminal
  7. Docking on membrane, fusion, exocytosis of NT into synaptic cleft
  8. Endocytosis of vesicles and their recycling
96
Q

how is ATP involved in mobilization of vesicles

A

ATP is required for enzymatic activity of protein kinase Ca/calmodulin kinase II (CaMKII) & the myosin light chain kinase (MLCK). these 2 kinases will phophorylate the proteins that function as substrates for mobilization of synapses I and myosin II which prime the vesicle for correct transport in the active zone of the terminal membrane

97
Q

proteins required for fusion and exocytosis of vesicles at the synaptic terminal

A

SNARE proteins
- vesicles and membrane associated protein required for fusion of vesicles to the active zone of the terminal membrane
Ca++ dependent process!!!!

98
Q

Snare protein

A

vesicles and membrane associated protein required for fusion of vesicles to the active zone of the terminal membrane

99
Q

synaptic delay

A

time between the pre-synaptic release of NT and postsynaptic response
includes time taken for NT discharge from vesicles, NT diffusion across synaptic cleft, binding of NT to receptor, and rate of ion diffusion in response to nT

100
Q

Botulism toxin

A

cleaves SNARE proteins
therefore unable to fuse and secrete NT

101
Q

neuromuscular junction

A

specialized synaptic junction between a nerve and a muscle fiber
where the nerve axon terminal (non-myelinated) fits into a groove in the membrane of the muscle fiber forming MOTOR END PLATES, which is invaginated into the synaptic cleft

102
Q

motor neurons

A

large, myelinated neurons, with their cell bodies located in the spinal cord

103
Q

motor end plate

A

where the nerve axon terminal fits into groove in membrane of the muscle fiber, which is invaginated in the synaptic cleft

104
Q

what is the Nt always at the NMJ

A

acetylcholine (Ach)

105
Q

Describe an AP at the NMJ

A
  1. AP arrives at axon terminal causes voltage sensitive Ca channels to open and Ca enters axon terminal
  2. Ca causes Ach release from vesicles into synaptic cleft
  3. Ach binds to receptors on muscle and causes Ach gated Na/K channels to open
  4. Na causes depolarization & generation of end-plate potential (graded)
  5. local current flow generates AP in both directions along muscle membrane
  6. Ach diffuses into cleft and it metabolized by Acetylcholinesterase (AchE) (limits action of Ach in NMJ)
106
Q

Every action potential in a motor neuron will result in what?

A

An AP in a muscle cell

107
Q

What type of input is to the NMJ?

A

all excitatory

108
Q

curare

A
  • Ach Antagonist
  • poison on arrow tips by S. Americans
  • binds strongly to receptors and does not allow ion channels to open thereby preventing Ach from binding
  • not metabolized by AchE
  • leads to muscle paralysis, and death by asphyxiation

muscle relaxant at low doses
snake venom
from plants

109
Q

organophosphates- pesticides

A

AchE inhibitors
- excessive Ach therefore HYPER stimulates its receptors due to inability to breakdown Ach
- results in spasms and can result in laryngeal spasms and therefore suffocation

110
Q

botulism

A

prevents docking and secretion of Ach from nerve terminals at NMJ, can cause death by paralysis of breathing muscles
targets snare
0.0001 mg can kill a pig

111
Q

myasthenia gravis

A

muscle weakness, caused by decreased numbers of Ach receptors at NMJ, so therefore Ach is released but is ineffective b/c not binding. causes muscle paralysis
TX= blockers of acetylcholinesterase to provide relief of symptoms

112
Q

milk fever

A

low blood calcium after onset of lactation
muscle weakness is caused by failure to transmit nerve signals across NMJ

113
Q

skeletal muscle features

A

long & cylindrical
multinucleated
striated
voluntary

114
Q

cardiac muscle features

A

short & branched
uninucleate
striated
involuntary
intercalated disks

115
Q

smooth muscle features

A

spindle shaped
uninucleated
non-striated
involuntary

116
Q

What doe all skeletal movements rely on?

A

tension generated by muscle cells which ATP is required for (from aerobic and anaerobic metabolism)

117
Q

Major function of skeletal muscle

A

contraction and relaxation controls the movement of joints

118
Q

major function of smooth muscles

A

contraction and relaxation controls the constriction and dilation of numerous tubular organ systems

119
Q

major function of cardiac muscle

A

contraction and relaxation controls the rhythmic beating of the heart and consequently blood flow in the CV system

120
Q

what is skeletal muscle innervated by?

A

the somatic nervous system
voluntary & contractible
high force
easily fatigued

121
Q

Describe the structure of a skeletal muscle from largest to smallest

A

whole muscle
muscle facile
myofibrils in sarcoplasm (cytoplasm of a muscle cell)
myofilaments

122
Q

sarcomere

A

structures between 2 Z discs
H zone in between

123
Q

sarcoplasmic reticulum

A

surrounds myofibrils
tubules
longitudinal to myofibrils

124
Q

terminal cisternae

A

transverse muscle fibers, STORE CA

125
Q

what are the characteristics of white muscles

A

little myoglobin
mostly ANAEROBIC glycolysis
fast & forceful contraction
rapidly tiring

126
Q

what are the characteristic of red muscle

A

lots of myoglobin
AEROBIC glycolysis
slow, less forceful shortening of the muscle
high endurance

127
Q

white and red skeletal muscle cells can be further classified base don what?

A

their functional characteristics

128
Q

S fibers

A

SLOW
(group I, similar to red)

129
Q

FR fibers

A

FAST, FATIGUE-RESISTANT
group IIA, between red and white (medium exertion, aerobic & anaerobic)

130
Q

FF fibers

A

FAST, easily FATIGUABLE
IIB, like white

131
Q

Type I fibers

A

slow twitch
known as red or also slow

132
Q

Type II fibers

A

fast
IIA= red, fast oxidative, medium resistance to fatigue
IIB= white, fast glycolytic, least resistance to fatigue

133
Q

what controls smooth muscles

A

autonomic
involuntary contractile control
BP, GI contraction,

134
Q

Desnse bodies of smooth muscle

A

equivalent to Z plate of skeletal muscle
contain the actin filaments connected to the sarcolemma

135
Q

intermediate filaments

A

transfer force from myosin filaments to sarcolemma

136
Q

endoplasmic reticulum

A

Ca++ store in skeletal muscles and smooth muscles
Ca binding protein = troponin/tropomyosin in skeletal
Ca binding protein= calmodulin in smooth

137
Q

intercalated discs

A

cardiac muscle feature
stair-step fashion to connect muscle cells to each other

138
Q

gpa junctions in cardiac muscle

A

where transmission of cardiac muscle stimuli occur

139
Q

what is mechanical stability facilitated by in cardiac muscle?

A

maculae adherent and fasciae adherens

140
Q

striated muscle contraction at NMJ

A

ACh binds postsynaptic N2 receptors (Na/K channels), depolarization of muscle cell membrane is conducted inward via T tubules and initiates Ca++ release from sarcoplasmic reticulum

141
Q

what is the initial signal to the target muscle for contraction?

A

transmission of an AP from the CNS via motor neurons to the motor endplate

142
Q

once ACh is released by motor or autonomic neurons, what happens?

A

binds to nicotinic ACh recpeptors on postsynaptic muscle fibers
result sin NA influx via depolarization of sarcolemma = ENDPLATE POTENTIAL

143
Q

what happens after endplate potential triggers AP

A

diffusion to the entire sarcolemma as well as transverse tubules
Voltage gated and tension sensitive Ca channels activated
increase in release of Ca ions, and increase in Ca concentration around myofibrils
contraction trigger

144
Q

where does a VOLUNTARY triggered contraction stem from

A

cerebral motor cortex whose long axon transmits the electrical impulse to motor neurons in anterior horn of spinal cord

145
Q

Common neuromuscular blocking drugs

A

Atacurium and vecuronium
used to paralyze patients during surgery via blocking nicotinic ACh receptor

146
Q

drug used to TX myasthenia gravis

A

Pyridostigmine
cholinerase inhibitor so increased ACh in NMJ

147
Q

sarcoplasmic reticulum

A

specialized smooth ER
encircles myofibirls
always in pairs

148
Q

T tubules

A

invaginations of sarcolemma into cell interior
between paired terminal cisternae to from a triad
lumen is continuous with extracellular space within myofibrils , conduct AP into every sarcomere
ensures each sarcomere contracts simultaneously in response to depolarization of sarcolemma

149
Q

what happens when impulses are conducted via T tubules?

A

signal the opening of voltage gated Ca channels in membranes of terminal cisternae and Ca is released from adjacent paired terminal cisternae to the adjacent sarcomere

150
Q

T/F: sarcoplasmic reticulum regulated the intracellular sarcoplasmic Ca++ concentration, which rises and falls during contraction and relaxation of myofibrils

A

true

151
Q

motor unit

A

structure containing muscle fibers of a common branch, which are innervated by a single alpha-motor neuron (from anterior horn of spinal cord). the AP of a single alpha-motor neuron is responsible for simultaneous contraction of all muscle cells of a motor unit

152
Q

electrochemical coupling

A

the process of transforming an electrical impulse into a muscle contraction

153
Q

Z disc of sarcomere

A

proteins perpendicular to axis of myofibril, the lateral bounds of a sarcomere
thin filaments of actin are anchored to the z bands
actin filaments extend inwards from each z disc to the middle of the sarcomere
actin filaments partially overlap the thick myosin filaments

154
Q

I band of sarcomere

A

thin actin filaments ONLY, encompass Z disc

155
Q

A band of sarcomere

A

overlapping thin actin and myosin heads and thick filaments
encompass the H zone and the M line

156
Q

H zone of sarcomere

A

thick MYSOSIN HEADS ONLY

157
Q

M line of sarcomere

A

thick filaments linked to myosin which hold the myosin in place

158
Q

sliding filament theory

A

describes the interaction of the actin filaments with the myosin filaments, leading to muscle contraction
no change in length of myofilaments during a contraction but rather only shortening of the sarcomere through the sliding of the myofilaments

159
Q

how is the myosin head activated?

A

It has ATPase activity and can split TAP and store the energy

160
Q

cross-bridge

A

short-term chemical bond between actin and myosin molecules occurs when troponin/tropomyosin complex binds CA ions released by the intracellular stores

161
Q

how does the sarcomere shorten

A

myosin head tilts 45 degrees which pulls the bound actin filament to the middle of the sarcomere

162
Q

what happens to allows the myosin head to disconnect from the actin filaments

A

a new ATP can be bound following the positional change of the myosin head, a new cross bridge cycle can begin

163
Q

how does a muscle contraction end

A

by lowering the intracellular Ca++ level in response to cessation of AP in motor unit

164
Q

where is energy derived from during short, intensive efforts, like sprinting?

A

ATP synthesis from existing creatinine phosphate and anaerobic glycolysis of glucose from muscle glycogen with lactate release

165
Q

where is energy derived from during long, lasting efforts?

A

glucose breakdown from muscle glycogen through aerobic glycolysis and ATP recovery through oxidative phosphorylation

166
Q

where is energy derived from during bodily exertion for hours?

A

glucose breakdown from muscle and liver glycogen and triaglycerol

167
Q

isotonic contraction

A

tension overcomes load
all jumping and throwing activities involved both type of isotonic
help stabilize joints and maintain posture while other joints move
muscle shortens, and tension remains constant
TWO TYPES
1. concentric
2. eccentric

168
Q

concentric contraction (isotonic)

A

tension develops as there muscle shortens

169
Q

eccentric contraction (isotonic)

A

tension develops while the muscle lengthens
(quads stretch and develop tension eccentrically to counteract gravity and control descent)

170
Q

isometric contraction

A

load exceeds muscle peak tension developing capability
muscle develops maximum tension and does nit shorten

171
Q

is work performed during an isometric contraction?

A

no
work is computed by considering product of muscle shortening and load
invested energy for isometric is transformed into heat

172
Q

how do red muscle fibers increase muscle performance

A

increase myoglobin content, number of mitochondria. and capillary formation

173
Q

how do white muscle fibers increase muscle performance

A

increase number of myofibrils and glycogen storage to increase muscle diameter — muscle hypertrophy

174
Q

length tension curve

A

the longer a muscle is in a state of strain the more force has to be exerted

clinically: in cases of excessive strain. muscle fibers are damaged, known as a muscle tear

175
Q

what determines the classification of smooth muscles

A

different contraction behaviors

176
Q

single unit smooth muscles

A

coupled by gap junctions therefore work as one coherent functional unit - muscles contract together
found predominantly along organ walls and blood vessels

177
Q

multi unit smooth muscles

A

capable of contracting independently of one another due to the predominantly autonomic innervation
few gap junctions
electric coupling occurs via basal-membrane like layer
NT are distributed by varicosities
in iris and in the arrector pili muscles

178
Q

special features of smooth muscle contraction

A

spontaneous autonomous contraction
affected by NT: ACh AND norepinephrine (on adrenergic receptors)
predominant share of Ca is from extracellular space
SR much less developed
no T tubules
no troponin site for Ca
MLCK activates myosin ATPase
cross bridging occurs very easily since myosin binding sites are always exposed

179
Q

smooth muscle contraction steps:

A
  1. Ca binds to calmodulin
  2. MLCK activate through CA- calmodulin complex
  3. phosphorylation of the light chain of the myosin head through MLCK, using TAO
  4. contraction via cross-bridge formation
  5. separation of remaining phosphate from the light chain of the myosin head through myosin light chain phosphatase (MLCP) causes dissolution of the actin myosin bond
180
Q

How can selective control of smooth muscle contraction be obtained?

A

the use of adrenergic drugs
albuterol is a brochodilater
acts on beta-2 adrenergic receptors to relax the bronchial smooth muscles and dilate them

181
Q

how are electrical impulses transmitted through the heart

A

transmitted via gap junctions to the cardiac muscle and later to the working myocardium

182
Q

divisions of specialized cardiac muscle cells

A

electrical impulse formation and conduction systems

183
Q

features of the systems of specialized cardiac muscle cells (electrical impulse formation and conduction system)

A
  1. SA and AV nodes
  2. Bundles of His
  3. Bundle branches
  4. purkinje fibers
  5. working myocardium, (ventricular and atria cardiac muscles)= cells connected by gap junctions to from a syncytium- where conduction of impulses can occur rapidly
184
Q

what isolated syncytia

A

through annulus fibrous (valve connective tissue)

185
Q

what is responsible for mechanical work in the heart

A

working myocardium

186
Q

How does stimulation cause cardiac contraction

A

stimulation transmitted from SA node (impulse formation system) to syncytium to AV node
to bundle of HIs
to branches of Purkinje fibers (rapidly spread impulse to apex of heart and papillary muscles of heart valves)

187
Q

reflex arc

A

populations of ins neurons that respond to specific chemical or physical stimuli via the sensory components of the somatic and visceral sensory fibers that enter the CNS. sensory info is integrated in CNS where appropriate actions are recruited to address a homeostatic issue. Action is relayed via somatic and/or visceral motor fibers out of CNS, to target muscle and organ systems altering the physiology to resolve the homeostatic issue

188
Q

Is the following a feature of the parasympathetic or sympathetic nervous system?
preganglionic neuronal cell bodies are in cranial nuclei of brain stem and motor fibers exist at the level of the brainstem or sacral spinal cord

A

parasympathetic

189
Q

Is the following a feature of the parasympathetic or sympathetic nervous system?
preganglionic neuronal cell bodies are in the thoracolumbar spinal cord

A

sympathetic

190
Q

Is the following a feature of the parasympathetic or sympathetic nervous system?
peripheral ganglia are near to target organ

A

parasympathetic

191
Q

Is the following a feature of the parasympathetic or sympathetic nervous system?
peripheral ganglia are distant to target organ, in chain ganglia outside spinal cord

A

sympathetic

192
Q

Is the following a feature of the parasympathetic or sympathetic nervous system?
small ratio of postganglionic to preganglionic neurons

A

parasympathetic

193
Q

Is the following a feature of the parasympathetic or sympathetic nervous system?
large ratio of postganglionic to preganglionic neurons

A

sympathetic

194
Q

Is the following a feature of the parasympathetic or sympathetic nervous system?
the preganglionic NT = ACh
the postganglionic NT= ACh

A

parasympthetic

195
Q

Is the following a feature of the parasympathetic or sympathetic nervous system?
the preganglionic NT = ACh
the postganglionic NT= NE

A

sympathetic

196
Q

How does a somatic reflex arc difference from autonomic reflex arcs?

A

all of the generic components of somatic are also in autonomic
but somatic efferents are myelinated motor axons that synapse on skeletal muscle- conduct AP directly and rapidly to their target skeletal muscle
whereas
autonomic motor fibers (efferent) always consist of at least 2 neurons separated by peripheral ganglion

197
Q

peripheral ganglion contents

A

axon terminals of preganglionic neurons that synapse onto dendrites of postganglionic neurons in the autonomic motor pathway

198
Q

where are the cell bodies of preganglionic neurons

A

CNS within various nuclei or the brainstem and lateral horns or the T, L, and, S spinal cord segments

199
Q

where are the cell bodies of postganglionic neurons

A

in the autonomic ganglia and their axons will innervate the target organs

200
Q

where do parasympathetic branches come from

A

from the brainstem and caudal aspects of the spinal cord (lower lumbar and sacral levels)

201
Q

where do sympathetic branches come form

A

exit the spinal cord at the thoracic an lumbar levels

202
Q

cholinergic neurons

A

ACh producing
PARASYMPATHETIC

203
Q

noradrenergic neurons

A

NOR–EPI producing
SYMPATHETIC

204
Q

what features can distinguish the parasympathetic from the sympathetic nervous system

A

location of cell bodies of preganglionic neurons
distance between ganglion and effector organ
ratio of post ganglionic neurons to preganglionic neurons in the efferent pathway

205
Q

how does the relationship of having a SMALL number of POSTganglionic neurons for each preganglionic neurons effect the response?

A

parasympathetic
discrete control
not highly distributed responses

206
Q

how does the relationship of having a LARGE number of POSTganglionic neurons for each preganglionic neurons effect the response?

A

sympathetic
widely distributed responses

207
Q

parasympathetic

A

rest and digest
conservation of metabolic energy

208
Q

sympathetic system

A

during exercise or physical or emotional stress
flight or flight
energy consuming

209
Q

ANS innervation

A

synaptic vesicles containing NT are contained in numerous varicosities along terminal portion of the nerve fiber
so occurs throughout muscle vs at distinct location

210
Q

somatic innervation

A

precise innervation of individual striated muscles by individual motor axons

211
Q

baroreceptor reflex

A

baroreceptors in carotid sinus and aortic arch are stretch by high B, so sensory neurons in these regions are activated resulting in a signal that is transducer to the brainstem
brainstem cardiac centers are recruited, leads to reduction of sympathetic feedback and lowering HR aswell as dilation of blood vessels- which will decrease BP

212
Q

catecholamines

A

epinephrine and norepinephrine
directly releases as hormones into blood stream for broad physiologic effects
secreted by mature adrenal medullary cells

213
Q

what initiates the release of adrenal medullary hormones

A

cholinergic neurotransmission

214
Q

what are the type of receptors for ACh

A

cholinergic

215
Q

what are the type of receptors for NE and epi

A

adrenergic

216
Q

what type of receptors are cholinergic neurotransmission in all autonomic ganglia and at the adrenal medulla through?

A

nicotinic (N) cholinergic receptors

217
Q

what type of receptors are the cholinergic receptors at all parasympathetic final effector sites

A

muscarinic

218
Q

divisions of adrenergic receptors present in cell membranes of tissues innervated by postganglionic sympathetic neurons

A

alpha and beta
further subdivided into a1, a2, b1, b2, b3

219
Q

alpha adrenergic receptors

A

a1 and a2
g-protein coupled receptors
muscarininc in autonomic
effector target stimulated by postganglionicn neuron in sympathetic division
a1= smooth muscle contraction
a2= inhibition of transmitter release

220
Q

beta adrenergic receptors

A

effector targets are stimulated bay postganglionic neuron in sympathetic division
B1 and B2
coupled receptor
B1= heart muscle contraction
B2= smooth muscle relaxation

221
Q

muscarinic receptors

A

M1
M2
M3
M4
M5

Neurophysiology exam (1 decks)

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