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BIO 231 Anatomy OIT > Lecture Quiz 7 > Flashcards

Lecture Quiz 7 Flashcards

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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
What is the second way neurotransmitter is removed from the synaptic cleft?
diffusion of the synapse | glial cells may facilitate this process
26
What is the third way neurotransmitter is removed from the synapse?
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
27
What type of neurotransmitter is acetylcholine and where is it produced in the neuron?
excitatory or inhibitory main skeletal muscle excitatory neurotransmitter produced in axon terminal Acetyl CoA + choline -> Ach + CoA
28
Where is acetylcholine found?
CNS - basal nuclei and motor cortex | PNS - efferent somatic NS, parasympathetic NS (entirely), parts of sympathetic (preganglionic)
29
What happens if a patient has low Ach?
basal nuclei are destroyed | Alzheimer's disease
30
What are catecholamines?
chemically related group of neurotransmitters | synthesized from a common precursor, amino acid tyrosine
31
Describe norepinephrine
excites or inhibits | reuptaken then degraded by monoamine oxidase (MAO) in the presynaptic neuron
32
Where is norepinephrine found?
CNS | PNS - sympathetic nervous system between the neuron and effector organ
33
What do most antidepressants use and why?
``` monoamine oxidase (MAO) slows down the destruction of epinephrine ```
34
Describe dopamine
excites but also inhibits | in the brain, it affects mood, sleep, attention and learning
35
What do abnormal levels of dopamine do to a patient?
low - parkinson's | high - schizophrenia
36
Describe serotonin
indolamine synthesized from tryptophan mostly inhibitory important transmitter in control of sleep
37
What happens to the body when LSD is taken?
binds to serotonin receptors blocks inhibitory effect leads to hallucinations
38
Describe GABA
gamma amino butyric acid | main inhibitory neurotransmitter in CNS
39
What happens when there is a loss of GABA in the cortex?
hyperactivity in the neurons such that is seen in epilepsy
40
Describe glutamate
main excitatory neurotransmitter in CNS
41
Describe endorphins
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
What is a neuronal pool?
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
How is the strength of a stimulus received in a neuronal pool?
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
Describe how an input fiber enters a neuronal pool
it branches and synapses with numerous neurons
45
What happens in the discharge zone of a neuronal pool?
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
What happens in the facilitated zone of a neuronal pool?
neurons form single or few synapses with presynaptic neuron | action potential will result only after multiple stimulations from the presynaptic neuron
47
Define neurotransmitter
special chemicals that transmit impulse between two neurons or neuron and effector cell
48
What is neural integration?
different parts of nervous systems have to be working together they are integrated into one system
49
Describe diverging (amplifying) circuits
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
Describe converging circuits
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
Describe reverberating (oscillating) circuits
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
Describe parallel after-discharge circuits
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
What is serial processing?
exemplified by spinal reflexes involves sequential stimulation of the neurons in a circuit response is predictable ex: reflex arc
54
What is parallel processing?
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
What do exocrine glands do (brief)?
produce and release substances via ducts onto the surface or the organ's lumen
56
What do autocrine glands do (brief)?
produce chemicals that are released into the extracellular space and affect the same cells that produced them
57
What do paracrine cells do?
affect cells in the immediate proximity of the secreting cells
58
What do endocrine glands do?
ductless produce hormones and release them into the blood stream hormones affect target cells located elsewhere in the body
59
What are the first and second most controlling systems in the human body?
1. nervous | 2. endocrin
60
Where are only endocrine glands found?
``` pituitary thyroid parathyroid adrenal pineal thymus ```
61
Where are end/exocrine glands found?
pancreas ovaries testes
62
Where are neural/endocrine glands found?
hypothalamus
63
What organs have a small endocrine component in the body?
``` adipose tissue intestinal wall stomach kidneys heart ```
64
What are hormones?
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
How are hormones found in the blood?
low concentration | the transduction of the signal to the target cells is amplified at every step
66
At what rate are hormones produced?
not constant, but rather in a pulsatile manner
67
How long do effects last on target cells?
prolonged | can be first observed in seconds to days
68
What does hormone metabolism include?
clearance by the liver and kidneys | intracellular degradation
69
Describe amino acid and protein hormones
produced from amino acids and are usually hydrophillic (exception: thyroid hormone) examples: insulin, glucagon, growth hormone, thyroxin, epinephrine
70
Describe steroid hormones
synthesized from cholesterol hydrophobic examples: glucocorticoids, mineralocorticoids, sex hormones these require a transporter
71
Describe eicosanoid hormones
synthesized from arachidonic acid act only as local hormones (para/autocrine) ex: leukotrienes, prostaglandins, thromboxanes
72
How does polarity affect hormone-cell interaction?
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
What do hormones interact with on target cells?
cell receptor | very specific and have a high affinity to the hormone
74
What are the five different ways hormonal receptor stimulation can change normal processes in target cells?
``` 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
What are the two major types of hormone receptors?
surface receptors | cytoplasmic/nuclear receptors
76
Describe the tyrosine kinase hormonal mechanism of action
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
What are some of the major properties of hormones?
``` low concentrations signal amplification pulsatile secretion have lag times prolonged effects transport metabolism - clearance by liver and kidneys ```
78
Describe the mechanism of action via 2nd messenger
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
Describe the mechanism of action via 3rd messenger
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
Describe the gene activation mechanism aka stimulation of intracellular receptors
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
What is significant about thyroid hormone?
It is the only hydrophobic amino acid hormone | also binds to receptors in the nucleus as opposed to the cytoplasm like other hormones
82
The physiologic effects of hormones on the target cells depend largely on what two factors?
sensitivity and number of receptors on the target cells | hormone concentration in the blood and extracellular fluid
83
How is the concentration of hormones regulated by rate of production?
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
What is negative feedback?
seen when the output of a pathway inhibits input to the pathway (most common)
85
what is positive feedback?
when the output of a pathway stimulates the input to the pathway
86
How is rate of delivery of hormones controlled?
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
What can a decreased number of hormone receptors do to cells?
influences the effects that hormones exhibit on the target cell
88
How are hormones regulated by rate of elimination?
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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