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BIO 231 Anatomy OIT > Lecture Quiz 7 > Flashcards

Lecture Quiz 7 Flashcards

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Biology 101 flashcards
1
Q

Define what a synapse is

A

a junction that mediates information transfer between neurons or between a neuron and an effector cell

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2
Q

What are electrical synapses?

A

cells that are closely bounded and electrical stimulus is passed directly from one cell to another
fast but rare in NS

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3
Q

Where are electrical synapses mostly found?

A

embryonic nervous system

cardiac muscle

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4
Q

What are chemical neurons?

A

not in direct contact

use chemical substance (neurotransmitter) to convey stimulus from one cell to another

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5
Q

What are the three types of chemical synapses and what do they connect?

A

axodendritic - axon to dendrite
axosomatic - axon to neuron body
axoaxonix - axon to axon

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6
Q

How does direction of impulse define the neuron?

A

neurons conducting impulses towards the synapse are presynaptic
neurons conducting impulses away from the synapse are postsynaptic

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7
Q

What do presynaptic neurons contain?

A

presynaptic membrane with voltage-gated Ca2+ channels

synaptic knob where vesicles of neurotransmitter are found

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8
Q

How do neurotransmitters end up in the axon terminal?

A

most neurotransmitters are made in the cell body of a presynaptic neuron and then transported down the axon via microtubules to the axon terminal
this process is called axonal transport

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9
Q

What is the synaptic cleft?

A

a small space between the neurons

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10
Q

what is found in the postsynaptic neuron?

A 
postsynaptic membrane (body or dendrite) has receptors to neurotransmitter
the receptors are connected to ion channels
ligand-gated channels are found here (ligand = neurotransmitter)
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11
Q

What do synapses provide?

A

the transduction of the electrical stimulus from cell to cell

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12
Q

Briefly describe the signal transduction between presynaptic and postsynaptic neurons

A

presynaptic neuron generates action potential that propagates along the axon to the synaptic knob
electrical impulse is converted into chemical and transmitted to the postsynaptic neuron

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13
Q

What happens when the action potential arrives at the synaptic knob?

A

a change in membrane polarity causes voltage-gated Ca2+ channels to open

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14
Q

What happens at synapse after Ca2+ channels open?

A

Ca2+ enters the cell down the concentration gradient and stimulates exocytosis of the neurotrasmitter vesicles into the synaptic cleft
done through facilitated diffusion which does not require ATP

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15
Q

What happens when the neurotransmitter is released from the synaptic knob?

A

neurotransmitter travels across the synaptic cleft and binds to receptors on the postsynaptic membrane
activation of the receptors causes chemically gated channels to open
chemical transmission requires diffusion

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16
Q

What is the rate-limiting step of neural transmission?

A

when the neurotransmitter is released and binds to postsynaptic membrane

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17
Q

What happens after ion channels open on postsynaptic membrane?

A

this allows ions to flow through the membrane

this generates a graded potential (postsynaptic potential) which is also an electrical impulse

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18
Q

What happens if the neurotransmitter activates sodium channels?

A

Na inflow results in depolarization on the postsynaptic membrane
excitatory postsynaptic potential (EPSP) results
neurotransmitter is considered excitatory neurotransmitter

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19
Q

What happens if the neurotransmitter activates potassium or chloride channels?

A

K+ outflow or Cl- inflow results in hyperpolarization on the postsynaptic membrane
inhibitory postsynaptic potential (IPSP) results
neurotransmitter is considered inhibitory

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20
Q

Describe postsynaptic potentials

A

graded potentials

decremental, vary in amplitude and duration, may be summed

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21
Q

What is temporal summation?

A

results from one presynaptic neuron firing repeatedly

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22
Q

What is spatial summation?

A

results from several presynaptic neurons firing simultaneously

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23
Q

How does the transmission of the impulse in the synapse end?

A

neurotransmitter is removed from the synaptic cleft

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24
Q

What is the first way neurotransmitter is removed from the synaptic cleft?

A

reuptake by the presynaptic membrane: the whole neurotransmitter molecule is taken back into the axon terminal that released it
this is commonly found with norepinephrine, dopamine, and serotonin

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25
Q

What is the second way neurotransmitter is removed from the synaptic cleft?

A

diffusion of the synapse

glial cells may facilitate this process

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26
Q

What is the third way neurotransmitter is removed from the synapse?

A

degradation by special enzymes
a specific enzyme changes the structure of the neurotransmitter so it is not recognized by the receptor
ex: cholinesterase breaks down Ach -> acetate + choline
presynaptic terminal reuptakes choline for Ach synthesis

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27
Q

What type of neurotransmitter is acetylcholine and where is it produced in the neuron?

A

excitatory or inhibitory
main skeletal muscle excitatory neurotransmitter
produced in axon terminal
Acetyl CoA + choline -> Ach + CoA

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28
Q

Where is acetylcholine found?

A

CNS - basal nuclei and motor cortex

PNS - efferent somatic NS, parasympathetic NS (entirely), parts of sympathetic (preganglionic)

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29
Q

What happens if a patient has low Ach?

A

basal nuclei are destroyed

Alzheimer’s disease

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30
Q

What are catecholamines?

A

chemically related group of neurotransmitters

synthesized from a common precursor, amino acid tyrosine

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31
Q

Describe norepinephrine

A

excites or inhibits

reuptaken then degraded by monoamine oxidase (MAO) in the presynaptic neuron

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32
Q

Where is norepinephrine found?

A

CNS

PNS - sympathetic nervous system between the neuron and effector organ

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33
Q

What do most antidepressants use and why?

A 
monoamine oxidase (MAO)
slows down the destruction of epinephrine
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34
Q

Describe dopamine

A

excites but also inhibits

in the brain, it affects mood, sleep, attention and learning

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35
Q

What do abnormal levels of dopamine do to a patient?

A

low - parkinson’s

high - schizophrenia

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36
Q

Describe serotonin

A

indolamine
synthesized from tryptophan
mostly inhibitory
important transmitter in control of sleep

37
Q

What happens to the body when LSD is taken?

A

binds to serotonin receptors
blocks inhibitory effect
leads to hallucinations

38
Q

Describe GABA

A

gamma amino butyric acid

main inhibitory neurotransmitter in CNS

39
Q

What happens when there is a loss of GABA in the cortex?

A

hyperactivity in the neurons such that is seen in epilepsy

40
Q

Describe glutamate

A

main excitatory neurotransmitter in CNS

41
Q

Describe endorphins

A

polypeptides
“natural pain killers” released in the brain
stimulate the opioid receptors in the CNS eliciting a pain-killing effect
produced in large amounts during labor

42
Q

What is a neuronal pool?

A

a functional circuit of the CNS
each pool integrates incoming information from receptors or other neuronal pools and relays the information to other areas

43
Q

How is the strength of a stimulus received in a neuronal pool?

A

it is assessed by the nervous system based on neural recruitment (what neurons are firing and how many neurons are firing) and the rate of action potentials

44
Q

Describe how an input fiber enters a neuronal pool

A

it branches and synapses with numerous neurons

45
Q

What happens in the discharge zone of a neuronal pool?

A

neurons form multiple synapses with the presynaptic neuron
all EPSPs will summate and generate action potential
a neuron will fire even when it receives a weak stimulus from the presynaptic neuron

46
Q

What happens in the facilitated zone of a neuronal pool?

A

neurons form single or few synapses with presynaptic neuron

action potential will result only after multiple stimulations from the presynaptic neuron

47
Q

Define neurotransmitter

A

special chemicals that transmit impulse between two neurons or neuron and effector cell

48
Q

What is neural integration?

A

different parts of nervous systems have to be working together
they are integrated into one system

49
Q

Describe diverging (amplifying) circuits

A

common in sensory (afferent) and motor (efferent) pathways
incoming fiber triggers a response from several neurons and the signal is amplified
they are characterized by an incoming fiber that triggers responses in an ever-increasing number of fibers along the circuit

50
Q

Describe converging circuits

A

common in sensory and motor pathways
characterized by the reception of input from many sources
funnels the sources to a given circuit, resulting in strong stimulation or inhibition

51
Q

Describe reverberating (oscillating) circuits

A

input signal travels through a chain of neurons, each sending axons to the following and previous neurons
signals travel through the circuit over and over again
involved in the control of rhythmic cycles (sleep-wake, breathing)

52
Q

Describe parallel after-discharge circuits

A

involved in complex activities
characterized by the stimulation of several neurons parallel to the stimulating neuron
input from one neuron is delivered to several neurons simultaneously
stimulate single output neuron
signal not delivered simultaneously providing multiple stimulations to the output neuron
involved in complex mental processing

53
Q

What is serial processing?

A

exemplified by spinal reflexes
involves sequential stimulation of the neurons in a circuit
response is predictable
ex: reflex arc

54
Q

What is parallel processing?

A

results in inputs stimulating many pathways simultaneously
vital to higher level mental functioning
not always predictable
ex: diff people have diff rxns to snakes

55
Q

What do exocrine glands do (brief)?

A

produce and release substances via ducts onto the surface or the organ’s lumen

56
Q

What do autocrine glands do (brief)?

A

produce chemicals that are released into the extracellular space and affect the same cells that produced them

57
Q

What do paracrine cells do?

A

affect cells in the immediate proximity of the secreting cells

58
Q

What do endocrine glands do?

A

ductless
produce hormones and release them into the blood stream
hormones affect target cells located elsewhere in the body

59
Q

What are the first and second most controlling systems in the human body?

A
  1. nervous

2. endocrin

60
Q

Where are only endocrine glands found?

A 
pituitary
thyroid
parathyroid
adrenal
pineal
thymus
61
Q

Where are end/exocrine glands found?

A

pancreas
ovaries
testes

62
Q

Where are neural/endocrine glands found?

A

hypothalamus

63
Q

What organs have a small endocrine component in the body?

A 
adipose tissue
intestinal wall
stomach
kidneys
heart
64
Q

What are hormones?

A

the agents which are released into the blood and elicit specific effects on cells which possess special receptors to recognize the hormone
specific cells are known as target cells

65
Q

How are hormones found in the blood?

A

low concentration

the transduction of the signal to the target cells is amplified at every step

66
Q

At what rate are hormones produced?

A

not constant, but rather in a pulsatile manner

67
Q

How long do effects last on target cells?

A

prolonged

can be first observed in seconds to days

68
Q

What does hormone metabolism include?

A

clearance by the liver and kidneys

intracellular degradation

69
Q

Describe amino acid and protein hormones

A

produced from amino acids and are usually hydrophillic (exception: thyroid hormone)
examples: insulin, glucagon, growth hormone, thyroxin, epinephrine

70
Q

Describe steroid hormones

A

synthesized from cholesterol
hydrophobic
examples: glucocorticoids, mineralocorticoids, sex hormones
these require a transporter

71
Q

Describe eicosanoid hormones

A

synthesized from arachidonic acid
act only as local hormones (para/autocrine)
ex: leukotrienes, prostaglandins, thromboxanes

72
Q

How does polarity affect hormone-cell interaction?

A

Cell membrane is hydrophobic
if hormone is hydrophilic, such as amino acid hormones, a hydrophilic target cell on the surface is necessary to attract these hormones

73
Q

What do hormones interact with on target cells?

A

cell receptor

very specific and have a high affinity to the hormone

74
Q

What are the five different ways hormonal receptor stimulation can change normal processes in target cells?

A 
change in membrane permeability
stimulation of protein synthesis
activation/deactivation of enzymes
change in the rate of secretion
change in the rate of cell division
75
Q

What are the two major types of hormone receptors?

A

surface receptors

cytoplasmic/nuclear receptors

76
Q

Describe the tyrosine kinase hormonal mechanism of action

A

receptor is an integral protein
tyrosine kinase is the intracellular domain of the receptor
hormone binds to the extracellular part
conformation changes cause activation (phosphorylation) of tyrosine kinase
tyrosine kinase activates intracellular enzymes
ex: insulin

77
Q

What are some of the major properties of hormones?

A 
low concentrations
signal amplification
pulsatile secretion
have lag times
prolonged effects
transport
metabolism - clearance by liver and kidneys
78
Q

Describe the mechanism of action via 2nd messenger

A

hormone binds to the receptor on the outer surface of the target cells
receptors conformation change activates relay protein (g-protein)
g-protein stimulates effector protein, adenylate cyclase
adenylate cyclase converts ATP into cyclic AMP which acts as a 2nd messenger
cAMP activates intracellular enzymes that trigger a cascade of reactions in the cytoplasm

79
Q

Describe the mechanism of action via 3rd messenger

A

hormone binds to receptor
conformation changes relay protein (g-protein)
g-protein stimulates effector protein, phospholipase C
phospholipase splits PIP2 into DAG and IP3, both act as 2nd messengers and activate intracellular enzymes
IP3 triggers release of Ca2+ from endoplasmic reticulum
Ca2+ (3rd messenger) also activates intracellular enzymes

80
Q

Describe the gene activation mechanism aka stimulation of intracellular receptors

A

hormones are hydrophobic and can diffuse into the cell, where they bind to intracellular receptors
hormone-receptor complex enters the nucleus and binds to the promoter protein on the DNA
gene is activated and transcription (mRNA synthesis) begins
mRNA travels to cytoplasm where its used to make a protein encoded by activated gene - translation

81
Q

What is significant about thyroid hormone?

A

It is the only hydrophobic amino acid hormone

also binds to receptors in the nucleus as opposed to the cytoplasm like other hormones

82
Q

The physiologic effects of hormones on the target cells depend largely on what two factors?

A

sensitivity and number of receptors on the target cells

hormone concentration in the blood and extracellular fluid

83
Q

How is the concentration of hormones regulated by rate of production?

A

hormonal stimulation - secretion of hormones in direct response to changing blood levels
neural stimulation - nervous system modifies the stimulation of endocrine glands and their negative feedback mechanisms
endocrine stimulation - endocrine glands can be stimulated by the hormones produced by other endocrine glands

84
Q

What is negative feedback?

A

seen when the output of a pathway inhibits input to the pathway (most common)

85
Q

what is positive feedback?

A

when the output of a pathway stimulates the input to the pathway

86
Q

How is rate of delivery of hormones controlled?

A

amino acid-derived hormones are easily dissolved in the plasm and do not require a carrier
steroid hormones are transported via binding protein
rate of delivery can be regulated via vascular system (vasoconstriction/dilation) and availability of carrier proteins

87
Q

What can a decreased number of hormone receptors do to cells?

A

influences the effects that hormones exhibit on the target cell

88
Q

How are hormones regulated by rate of elimination?

A

hormones are excreted by the liver and kidneys as well as destroyed by intracellular enzymes in the target cells

BIO 231 Anatomy OIT (9 decks)

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