Exam 2 Flashcards
(254 cards)
1
Q
What are animal signal forms?
A
Sounds, scents, and visual cues
2
Q
what is within animal signal forms?
A
chemical and electrical
3
Q
what are the most types of signals (aka systems)?
A
the nervous and endocrine system
4
Q
What does the complexity of animal physiology and behavior require?
A
diversity of signaling mechanisms
5
Q
What causes cell signaling?
A
environmental trigger- need a cue for the production
6
Q
Cell signaling Steps (3):
A
- produciton of a signal in one cell
- transport of that signal (chemical messenger) to a target cell
- the messenger binds to a receptor to transduce signal into the target cell to cause a response
7
Q
What are the different types of direct signaling?
A
gap junctions and connexins
8
Q
what are the different types of indirect signaling?
A
autocrine, paracrine, endocrine, neural, exocrine
9
Q
Direct Signaling’s local communicaiton is
A
contact-dependent
10
Q
the chemical messengers pass through what in direct signaling
A
gap junctions or specialized membrane junctions or even directly
11
Q
what type of messengers are in direct signaling
A
ions, small molecules, and water
12
Q
is direct signaling an active diffusion?
A
no passive: opened and closed to regulate the communication of substances between cells
13
Q
steps for indirect cell signaling (3):
A
- release of a chemical messenger from signaling cell into the environment
- transport of chemical messenger through environment to target cell
- communication of signal to target cell by receptor binding
14
Q
Indirect signaling’s local communication is
A
contact independent and endocrine signaling
15
Q
Autocrine Signaling
A
messenger affects the signaling cell
itself
16
Q
Paracrine Signaling
A
messenger affects nearby cells
17
Q
How does distance affect the diffusion of the messengers in indirect signaling?
A
limits the rate of diffusion
diffusion is insufficient to carry signals to distant target cells
18
Q
is there a high chance of the messenger getting to a farther location regarding diffusion
A
the longer the distance= the lower chance the messenger gets to its target cell
19
Q
what are the messengers for endocrine signaling
A
hormones
20
Q
Glands
A
secretory cells of the exocrine and endocrine tissues are often grouped together into structures
21
Q
What system carries the hormones from the signaling cell to the target cell?
A
circulatory system
22
Q
What is the messenger for Neural signaling?
A
neurohormones
23
Q
does a electrical signal travel long or short distances?
A
long
24
Q
neurotransmitter
A
reaches terminus trigger release of a chemical messenger
25
Once reaching the target cells the neurohormone binds to what structure
receptor
26
Can all neurons secrete neurotransmitters directly into the circulatory system
no, some!
27
do neurohormones act like hormones
yes!
28
the most important distinction among the different indirect signaling systems is
distance messenger travels
speed of communication
29
speed of communication for autocrine and paracrine
milliseconds to seconds
30
speed of communication for nervous
milliseconds
31
speed of communication for endocrine
seconds to minutes
32
do endocrine signaling last longer
longer-lived
33
exocrine signaling
pheromone
34
What affects the way signaling is accomplished?
structure of the messenger
35
Hydrophobic Messengers
can diffuse freely across cell membrane
36
what holds hydrophobic messengers in a solution
protein carriers
37
hydrophilic messengers
cannot diffuse acorss the cell membrane
38
what process do they (hydrophilic messengers) do to exit cell
exocytosis
39
do hydrophilic messengers have carriers to travel to target cell?
no, they have to dissolve to transport to target cell
40
Ligands
a molecule that binds to another molecule called a receptor to send signals within or between cells.
41
What are the main classes of chemicals known to participate in cell signaling in animals?
Peptide messengers (hydrophilic)
Steriod Messengers (hydrophobic)
Biogenic Amine Messengers
Lipid Messengers (hydrophobic)
Purine Messengers
Gass messengers (ex: CO)
42
Peptide Messengers
Amino Acid residues
- hydrophilic or hydrophobic
- act as neurotransmitters
43
Peptides < 50 amino acids chains
Hydrophilic
44
Proteins > 50 amino acids chain
Hydrophilic
45
Where and how are peptide messengers synthesized?
ribosomes on the rough ER;
synthesized as large inactive polypeptides
46
Preprohormones
large inactive polypeptides
47
What do peptide messengers possess that target the polypeptide for secretion?
signal sequence
48
Prohormone (inactive)
prior to being packaged into secretory vesicles, signal sequence is cleaved from the preprohormone
49
Biogenic Amine Messengers: aka....
Small Water Soluble Hormones
50
Why do biogenic amine messengers require specific receptors?
- cannot cross plasma membrane
- too large
- carry a charge at physiological pH
51
Where are biogenic amine messengers to be stimulated?
vascular system
52
biogenic amine messengers are carried _____ to needed site
freely
53
examples of biogenic amine messengers:
- Epinephrine (Adrenaline)
- Norepinephrine (Noradrenaline)
- Serotonin
- Histamine
54
What receptors typically recognize hormones?
intracellular receptors (not cell surface receptors)
55
Where are hormones synthesized and secreted from?
Synthesized from cholesterols (hydrophobic); endocrine cells to act on distinct target sites in the human body
56
Examples of Steroid Hormones
estrogen, progesterone, testosterone
57
examples of thyriod hormones
thyroxin, retinoids (vitamin A), cortisol and vitamin D
57
What happens if there is no receptor for a signal?
cell will never be able to detect it
57
What is cell signaling?
- Extracellular signaling molecule (1st Messenger)
recognized by the receptor.
* Leads to the production of small transient signaling
inside the cell (2nd Messenger)
* Leads to alter the activity of the next component of
the transduction pathway.
* Formation of chains of molecules (cascades), where
each molecule passes the message to the next.
* Until the final signal causes the desired cell event.
57
What are the four criteria that must be met by a functioning receptor?
1) Has to have specificity
2) Binding affinity must be high
enough to detect ligands in
concentration found in
vicinity of cell
3) Must be able to transmit
message into the cell.
4) Needs to be turned off once
the message is received and
acted on
57
Agonist:
A ligand that binds to a receptor and it activates
the receptor.
58
Roles of receptors: Signal Detection
- The location of receptors can
vary.
- Receptor dysfunction
can/will lead to disease.
- Capacity of a cell to recognize
a signal will not be constant;
receptors change over time.
59
Antagonist:
A ligand that binds to a receptor and it does not
activate the receptor
60
If the ligand can bind to multiple receptors, the target's cell receptor _____ response
Specificity
61
One ligand can have one or multiple receptors
multiple
62
Example of a ligand that can bind to multiple receptors
epinephrine (adrenaline) - sympathetic nervous system
63
breakdown of epinephrine receptors
α-Receptors on
intestinal blood
vessels will cause
vasoconstriction
* β2
-Receptors on some
skeletal muscle
vessels will cause
vasodilation
64
can receptors become saturated? Why?
yes
- the receptor activity reaches a maximum rate due to the limited number of receptors on cell membrane
- Allowing for flexibility to vary responses based on extracellular conditions and internal needs
65
Down-regulation (desensitization)
decrease receptor number to desensitize cell response
Sustained Agonist Activity -> Endocytosis -> Recycling or Degradation -> Synthesis of New Protein -> Incorporation into Membrane
66
Up-regulation:
increase receptor number to sensitive cell response
Receptor Downregulation -> Increase total number of receptors -> decrease down-regulation -> withdrawal of antagonist -> elevated number of receptors can produce exaggerated response
67
High-Affinity Ligand Binding
results from greater
intermolecular force between the ligand and its receptor
68
High-affinity binding involves a __ ___ ___ for the ligand at its receptor binding site
longer residence time
69
What type of energy can be used to cause a conformational change in a receptor regarding high-affinity ligand binding?
physiologically important binding energy
70
Low-affinity ligand binding
results from lesser
intermolecular force between the ligand and its receptor.
71
Low-affinity binding involves a __ ___ __ for the
ligand at its receptor binding site
lesser residence time
72
What is the general sequence that ligand binding will initiate?
1) Binding causes a conformational change in the
outer domain of receptor.
2) Change is transmitted through membrane to
induce conformational change in the intracellular
domain of receptor.
3) Change will either activate or inhibit receptors
intrinsic activity to interact with intracellular
proteins
73
What are the five main classes of receptors?
1) G protein-coupled receptors
(GPCRs)
2)Ion channel linked receptors
3)Intrinsic enzymatic receptors
4) Tyrosine kinase-linked receptors
5)Intracellular receptors
74
Where are G protein-coupled receptors found?
only in eukaryotes, yeast, and animals (maybe in plants....)
75
Large diversity of receptors and intracellular effectors
involved in many diseases
GPCRs
76
Receptors are coupled to ____ G proteins and function as ___ exchange factors to transduce signal
trimeric; guanine
77
GPCRs target ___ of all modern medicinal drugs
40%
78
G PROTEIN-COUPLED RECEPTOR-LIGAND BINDING
Activation Cycle include:....
* GEF- Guanine nucleotide exchange Factor
* RGS- Regulator of G Protein
Signaling
* GAPs- GTPase accelerating
Proteins.
79
Membrane-bound receptors
Ligand-gated channels
80
Transient event
The ion channels open for a short time,
after which the ligand dissociates from the receptor and
the receptor is available once again for a new ligand to
bind.
81
Ligand-gated channels are involved in the detection of _____ and __ ___ used in synaptic signaling on electrically excitable cells
neurotransmitters; peptide hormones
82
What does the conformational change affect in ligand-gated channels?
Alters the ion permeability and charge across the plasma
membrane.
83
What undergoes a conformational change when a ligand binds forming a "water tunnel" allowing passage of specific molecules, such as sodium (Na+) or potassium (K+)?
Ligand-gated channels
84
Ligand-gated ion channel : Clinical Relevance
Likely to be the major site at which anesthetic
agents and ethanol have their effects, GABA.
* Drugs such as barbiturates used to treat insomnia,
depression and anxiety have been linked to
receptors.
* Diseases include schizophrenia, Parkinson’s
disease, Alzheimer’s disease, epilepsy and autism
have been linked, in part, to receptor defects.
85
Snake venom ( - α
neurotoxins)- antagonists
* Bind tightly and
noncovalently to nAChRs of
skeletal muscles
* Block the action of ACh at
the postsynaptic membrane,
inhibiting ion flow
* Leading to paralysis and
death
85
nAChRs normal vs agonist binding
Normally: nAChRs may exist in different interconvertible
conformational states.
Agonist binding: Stabilizes the receptor in the open
* allowing positively charged ions to move across it
* It will remain open until the agonist diffuses away.
* Usually takes about 1 millisecond
86
Nicotinic Acetylcholine
Receptor (nAChRs)
* Function:
– When acetylcholine is
bound, alter the receptor's
configuration and cause an
internal pore to open.
– Pore allows Na+
ions to flow
into the cell.
– Inward flow Na+
ions
depolarizes the
postsynaptic membrane
sufficiently to initiate an
action potential.
87
Commonalities of Intraceullar Receptors
- small and hydrophobic
- allows for free passage into the cell
- insoluble in aqueous fluids
87
Intracellular receptors
- Steroid hormones
– Thyroid hormones
– Retinoids
– Fatty acids
– Prostaglandins
– Leukotrienes
88
Cytosolic and Nuclear Receptor are all
transcription factors
89
Depending upon the intracellular steroid hormone Cytosolic and Nuclear Receptor bind, having two modes of action
– Located in the cytosol and move to the cell nucleus upon
activation
– Located in the nucleus waiting for the steroid hormone
to enter and activate them
– Covered up by heat shock proteins (HSP) which binds
the receptor until the hormone is present
90
Cytosolic-
Hormone binding causes receptor
conformational change, freeing the receptor from
HSP and the receptor-hormone complex enter the
nucleus to act affect changes in transcription
91
Nuclear-
Hormone binding causes receptor
conformational change, freeing the receptor from
HSP and the receptor-hormone complex can act
upon transcription factor
92
Regulation of Cell Signaling
- sensor (regulated variable)
- integrating center
- effector
- negative and positive feedback
93
Feedback Regulation: local vs long distance
local level: paracrine and autocrine
long distance: nervous and endocrine
94
Step 1 in a Response Loop for Feedback Regulation
Stimulus: Change in a variable that sets the pathway in motion
95
Step 2 in a Response Loop for Feedback Regulation
* Sensor or Receptor: Monitors environment for changes in variable; must reach
Threshold: Minimum stimulus needed to start reflex response
96
Step 3 in a Response Loop for Feedback Regulation
* Afferent Pathway: Sends input signal to Integrating Center
97
Step 4 in a Response Loop for Feedback Regulation
* Integrating Center: Compares variable with set point to determine if it is out of range. If so, initiates output signal
98
Step 5 in a Response Loop for Feedback Regulation
* Efferent Pathway: Electrical or chemical signal that travels to target
99
Step 6 in a Response Loop for Feedback Regulation
* Target or Effector: Cell or tissue that carries out the appropriate Response to bring variable back to homeostasis
100
direct feedback loop
- Endocrine system only: No
CNS/PNS integrating center
* Endocrine cell itself senses
a change in the extracellular
environment and releases a
chemical messenger that
acts on target cells
elsewhere in the body.
* The endocrine cell acts as
the integrating center that
interprets the change in the
stimulus variable
101
First-Order Feeback Loop
Direct feedback loop but nervous
system becomes involved
* A sensory organ perceives a
stimulus and sends a signal via the
nervous system to an integrating
center (brain) that interprets the
signal.
* Neurons then transmit the signal
(neurotransmitter or neurohormone) to a specific target organ,
causing a response.
* Only a single step links the
integrating center and the response
102
Second-Order Feedback Loop
Second order feedback loops:
* There are 2 steps that link integrating
center and the response.
* Sense organ perceives a stimulus and
sends a signal to the integrating center
* Integrating center will then sends a
signal by a neuron telling the neuron to
secrete either a neurohormone or a
neurotransmitter
* Act on an endocrine glands will secrete
a hormone into the blood
* Travel to the target cell to cause a
response
103
104
105
Third-Order Loop
3 steps link integrating center and response
* Every step in a response loop may act as a
control point over the pathway
* Provide the most sophisticated and tightly
regulated feedback
* Sense organ perceives a stimulus and sends a
signal to the integrating center
* Sends a signal by a neuron telling the neuron
to secrete either a neurohormone or a
neurotransmitter
* Act on an endocrine glands to secrete a
hormone into the blood
* Travel to the target cell of second endocrine
gland, which will then induce a response.
106
Endocrine can refer to
a class of glands (exocrine & endocrine)
type of hormonal action (chemical signaling)
107
exocrine glands
secrete products externally (ex: sweat, salivary, sebaceous, mucous glands)
108
endocrine glands
secrete products internally (ex: pituitary, thyroid, pancreas, adrenal glands)
109
Chemical signaling can be
autocrine, paracrine, or endocrine
ectocrine & intracrine signaling
110
hormones are responsible for
long-term, on-going functions of body
111
Hormone functions of the body are
growth and development
metabolism
regulation of the internal environment
reproduction
112
what makes a chemical a hormone?
1. Secreted by a discrete and identifiable cell or group of cells derived from epithelial cell lineage
2. Secreted into the blood
3. Transported to a distant target and bind to target receptor
4. Exert their effect at very low concentrations (sometimes femtomolar)
112
the root word of hormones
to excite
113
3 Basic ways hormones act on target cells
By controlling rates of enzymatic reactions
By controlling the transport of ions or molecules across cell membranes
By controlling gene expression and synthesis of proteins
114
Four main classes of hormones
1. Peptide/Protein Hormones
2. Steroid Hormones (cholesterol derived hormones)
3. Amino Acid Derived
4. Miscellaneous (immune hormones)
114
Hormone release follows the basic pattern of a reflex
- stimulus
- sensor by receptor
- signal input
- signal integration
- signal output
- response
115
The endocrine cell is a sensor
simplest reflex control pathway
cell directly senses stimulus and responds by secreting hormone
cell acts as both a sensor and an integrating center
the output signal is the hormone released
negative feedback turns off reflex
116
Peptide Hormone Mechanism
acts through cAMP second messenger system of signaling cascade
117
example of peptide hormone
insulin (pancreas)
118
Cholesterol Dervied Hormones are ___ and can ___ diffuse through cell membranes
lipophilic; passively
119
Cholesterol Derived Hormones aka
Steroid Hormones
120
Cholesterol Derived Hormones are ___ soluble in plasma; bind to ___ protein (either ___ or ___)
not; carrier; globulin; albumin
121
Bound steroid is protected from degradation; meaning
extends hormone half-life, but blocks cell entry (must be unbound to act)
122
Low-Density Lipoprotein-
a wide array of sizes and densities; stays in circulation longer and more easily enter arterial walls
123
which one is bad cholesterol ?
low density lipoprotein
124
Why is lipoprotein considered bad cholesterol?
can create plaques, stay in the stream pretty long
125
High-Density Lipoprotein
smaller than LDLs; transport cholesterol from peripheral tissues to the liver. The liver can convert to bile acids and secreted in the bile
126
Why is high-density lipoprotein considered "good cholesterol"?
it removes excess cholesterol
127
Cholesterol is translocated into the mitochondria via consecutive actions of __ __ ___ ___ and the __ __ __ ___
steroid acute regulatory protein (StAR); 18 kDa translocator protein (TSPO)
128
cholesterol metabolized to pregnenolone by ____ and further metabolized in the __ ___
P450scc; smooth ER
129
Classic (Transcription) Steroid Hormone Receptors
- direct interaction with intracellular nuclear receptors
- takes longer to produce biological effect (minutes to days)
129
Steroid Hormone Receptors two general categories:
classical; non-traditional
130
Non-traditional Steroid Hormone Receptors
- Non-nuclear actions that alter nuclear receptor activation or cell signal transduction
- Rapid production of biological effect (seconds to minutes)
131
Examples of ligand: receptor complexes:
*Progesterone:Progestin Receptor
*Estradiol:Estrogen Receptor
*Testosterone:Androgen Receptor
*Cortisol:Glucocorticoid Receptor
132
In the resting state, some ___ ____ ___ are tethered in the cytosol, some are always nuclear, and some shuttle back and forth
nuclear steroid receptors
133
Biogenic Amines: Two Families from Tyrosine
Catecholamines and Thyroid Hormones
134
Catecholamines
Epinephrine (Adrenaline)
Norepinephrine (Noradrenaline)
Dopamine
135
Neurohormones: 3 major groups
1. Catecholamines – tyrosine-derived neurohormones (Dopamine, Epinephrine, Norepinephrine)
2. Hypothalamic neurohormones secreted from the posterior pituitary
3. Hypothalamic neurohormones that control hormone release from the anterior pituitary
135
Thyroid Hormones (T3,T4)
Behave like steroids and have intracellular receptors
136
Anterior Pituitary Gland
- true endocrine gland
- hormones are adenohyophyseal secretions
- second-order feedback loop system
137
Median eminence
functional connection between the hypothalamus and the pituitary gland
138
6 Anterior Pituitary Neurohormones (tropic hormone controls secretion of other hormones)
1. Prolactin (PRL)- Milk production
2. Thyrotropin (TSH)- Thyroid stimulating hormone
3. Adrenocorticotropin (ACTH)- Adrenal cortex hormone synthesis and secretion
4. Growth hormone (GH)- Somatotrophin- affects cellular metabolism
5. Follicle-stimulating hormone (FSH)-Gonadotrophin; females and males
6. Luteinizing hormone (LH)- Gonadotrophin hormone; females and males
139
Posterior Pituitary Gland
- false endocrine gland, extension of neural tissue in the brain
- hormones made in the hypothalamus and neurphypophyseal secretions
- Third-order feedback loop system
140
Posterior Pituitary Neurohormones
Vasopressin (Antidiuretic Hormone-ADH) and Oxytocin
141
Vasopressin acts on the ___ ___ in the kidney nephrons to ____ ____ in the body
collecting ducts; retain water
141
why is vasopressin released?
released in response to low blood volume
142
Vasopressin ___ blood vessels
constrict
142
What does the decreased release or decreased sensitivity of vasopressin lead to?
diabetes insipidus, hypernatremia (increased blood sodium concentration), polyuria (excess urine production), and polydipsia(thirst)
143
High levels of vasopressin might lead to
hyponatremia (low sodium levels) and hypervolemia (high fluid volume)
143
what does oxytocin play an important role in?
neuroanatomy of social trust, intimacy/sexual reproduction
144
what does oxytocin do during childbirth?
by it being released in large amounts, it causes the distension of the cervix and uterus
145
does oxytocin use positive or negative feedback mechanisms
positve feedback mechansims
145
after childbirth, what does oxytocin do?
facilitates maternal bonding, and lactation and milk ejection
146
oxytocin greek
"quick birth" to to refer to agents from Claviceps purpurea ("rye ergot fungus")- Ergometrine
147
Oxyoticin is the first ____ ____ to be sequenced and synthesized (du Vigneaud et al. in 1953)
polyphenol peptide
148
what is the slowest negative feedback loop?
long feedback loop; taking days
148
Negative feedback loop types
short, fast, long
149
the release of what promotes the anterior pituitary release of ACTH
CRH
149
what activates hypothalamic secretion of CRH
stress
150
what activates adrenal cortisol production
release of ACTH
150
Cortisol acts back on the hypothalamus to ___ ___ release and its own production
terminate CRH
151
What is also stimulated by stress other than hypothalamic secretion of CRH?
gonadal steriod production
152
Similar to ____ steroids, gonadal steroids act back on the brain at the level of the pituitary to ___ ___/____ release, which stops their own production
adrenal; terminate LH/FSH
153
Clinical Estrogen/Progestogen Drug Targets:
Ant. Pit.: Inhibition of negative feedback for oral contraception
Ovary: Inhibition of ovarian function for oral contraception
Aromatase: Inhibition of estradiol formation for cancer
Receptor: Antagonism of ER in ER+ cancers; Agonism for HRT
154
sex hormone-binding globin (SHBG)
vacuums testosterone that is circulating
155
Clinical Androgen Drug Targets
Hypothalamus: Inhibition of GnRH feedback for prostate cancer; agonism for HRT
Testis: Inhibition of testicular function for Cushing’s or refractory prostate cancer
5α-reductase: Inhibition of DHT formation for benign prostatic hyperplasia
Receptor: Antagonism for prostate cancer; agonism for HRT
156
Cell types of CNS
neurons and neuroglia
157
support cells of the neuroglia
oligodendrocytes, microglia, astrocytes
158
parts of neuronal signaling
Neuronal Zones
* Dendritic Signaling
* Synapse
159
Neurons
functional unit of the nervous system
communicates and transports signals
160
neuroglia
highly vasculature, tons of energy used; maintains privileged environment; blood-brain barrier
161
oligodendrocytes
forms myelin sheaths around neurons
(important for regulating action potential)
162
Microglia
immune cells of the brain; least abundant; inactive/active phenotypes; macrophage-like (engulfing the bad things)
163
Myelin
lipoprotein that surrounds thicker axons
164
astrocytes
most abundant; major support cell of the brain; essential for brain homeostasis
165
Oligodendrocytes function
an insulating layer that prevents leakage of electrical current; increases speed of impulse conduction along axon; energy efficient; enhances electrical impulse jumping (leaping down the axon )
166
What are the three phenotypes of microglia?
Resting
M1 (pro-inflammatory)
M 2 (anti-inflammatory)
167
Function of Microglia
- cellular debris clearance
- phagocytic of living/dying/dead cells
- release diffusible factors (pro/anti- inflammatory cytokines)
168
Astrocytes are major support cell of brain ___ ___ ____
especially for neurons
169
Astrocytes maintains
pH, brain homeostasis, and elicits signals
170
Astrocytes are the ____ between the neurons and environment (signals within the blood)
communicator
171
Astrocytes prove ____ _____ and sweep up extra ______
necessary materials (parents); neurotransmitters
171
Astrocytes modulate _____ ______ and _____ uptake/conversion
synapse formation; glutamate
172
Unipolar neuron
the cell body is on one end (no dendrites) -> myelin-> axon terminal
172
What are the commonalities between the multiple types of neurons?
cell body
axon
dendrite
173
Multiple types of neurons
unipolar
bipolar
pseudounipolar
multipolar
174
bipolar neuron
cell body is between sensory receptor (bottom) and axon terminal (end)
175
pseudounipolar neuron
no myelin and is more common
sensory receptors at end
cell body is hanging off?
176
Multipolar neuron
dendrite (multiple sources) on cell body -> myelinated axon -> axon terminal
177
The cell body of a neuron
enlarged part of cell
that contains the nucleus and
organelles
178
Axon Transport Types
slow and fast
179
the axon of a neuron
long cytoplasmic extension;
specialized for signal transduction
179
the dendrites of a neuron
cytoplasmic extensions from the cell body; receive incoming signals
180
Slow axonal transport
cell components are transferred from the cell body to axon
terminal
* *used for materials not consumed rapidly by the cell; e.g., enzymes and cytoskeleton proteins)
181
Fast axonal transport
transported vesicles “walk” with the aid of attached foot-like
motor proteins with the use of stationary molecules (microtubules) as tracks
* mitochondria, lipids, synaptic vesicles, proteins, and other organelles
* Neuroinvasive Viruses (i.e., Rabies and West Nile Viruse) uses retrograde fast axonal transport to
infect the CNS
182
Types of fast axonal transport
anterograde and retrograde
183
Anterograde
“forward” cell body to axon terminal
184
Retrograde
“backward” axon terminal to cell body
185
Signal reception zone
dendrites and the cell body: receiving incoming signals
186
Singal integration zone
axon hillock: where the cell body meets the axon; if there is a large enough
stimulus, the stimuli is converted to an electrical signal (change in
membrane potential) that is sent down the axon
187
Signal Conduction Zone
axon: nerve fiber that conducts electrical signals
188
signal transmission zone
collaterals (axon terminals): swelling at axon terminus where comes in close contact with the
target cell; does not touch
* electrical signal is converted to a chemical signal
(neurotransmitter)
189
what is the importance of surface area for synapses within the dendrites?
wide range of communication between a microenvironment
189
Boutons (Pre) and Spines (Post)
convert chemical signal to electrical signal
ion channels opening or closing
alter membrane potential
190
In the signal reception zone:
* Terminal _____ and ______
* Synaptic _____-_____ ____ between cells where chemical
communication/transmission occurs
* Changes in ______ ______ elicit chemical release from the presynaptic cell
boutons and synapse
cleft-small gap
membrane potential
191
function of the axon
transmit outgoing electrical signals from the integrating center to the target cells at the end of the axon
191
axon hillock is where the summation of signals are from the
boutons
191
physiology of the axon
axon extends from the axon hillock
length (2uM -1m)
192
What does the electrical signals from the integrating center cause?
neurotransmitters
192
Resting Membrane potential
the separation of intracellular potassium ions from anions across the cell membrane of the cell; concentration gradient of potassium ions must be set up
193
What pump is used in the resting membrane potential?
Sodium-Potassium Pump (Na+/K+-ATPase)
194
is Na+ mostly found in the intraceullar or extracellular
extracellular
195
is K+ found mostly in the intracellular or extracellular
intracellular
196
A resting (unstimulated) cell and membrane has
the potential to conduct
electrical signal or action
potential
197
Sodium Potassium Pump
* 3 sodium ions pumped out of the cell
* 2 potassium ions pumped into the cell
* Creates a deficit of positive ions on the inside
of the cell
* So inside is more negative than the outside
198
The resting membrane potential is not an ____ potential, meaning it requires ATP
equilibirum
199
3 important factors to establish a membrane potential
1. The distribution of ions across the
plasma membrane (at rest)
2. The permeability of the membrane
to these ions (highly permeable to
a certain ion)
3. Charge on the ions that are moving
200
Goldman Equation -
describe the effects these factors have on the
membrane potential; predicts the equilibrium potential for certain ions
201
If the membrane is ______ _______ to an ion, the ion _______ ______ ______to the membrane potential
not permeable; does not contribute
202
If the membrane is _____ _____ to an ion, that ion ______ ___ _____ ________ to the membrane potential
highly permeable; makes a large contribution
203
Excitable cells selectively alter the permeability of their membranes to ions
* By opening and closing gated ion channels in the membrane.
* Changing ion permeability alters the membrane potential and generates
electrical signals
204
Potassium has the highest permeability since
they have leak charges that allow for the movement of potassium across the membrane to achieve equilibrium potential
204
Goldman Equation: Sodium and Potassium
sodium: +60 mV
potassium: -90 mV
205
Most membrane potentials are around this range
Vm= -70 mV
206
If you increase the extracellular sodium,
it would make the membrane potential less negative and more positive.
207
Inside of the cell membrane is more ____ charged than outside
negatively
208
Defined as a relativly stable, groud value of ____ ____ in animal and plant cells regarding resting membrane potential
transmembrane voltage
209
Stimulus of resting membrane potential
positive ions influx
210
Steps of Action Potentials:
threshold, depolarization, depolarization, hyper-polarization
210
What voltage does threshold potential need to reach to be excitatory potentials?
-55 mV
210
What are some possible inhibitors?
too sub-threshold potentials
too supra-threshold potentials
211
Threshold Potential
are graded potentials need to be reached for action potential to "fire"
212
so what happens at -55 mV?
voltage-gated Na+ channels on the membrane open allowing an influx of Na+ cations
213
Depolarization
membrane potential becomes less negative either through more positive charged ions entering cell or more negative charged ions leave the cell
214
Depolarzaiotn what type of channels ?
sodium/potassium leaky channels; very leaky to potassium not so leaky to sodium (potassium leaks out of the cell)
215
what does the sodium/potassium leaky channels do?
stop the cell from reaching threshold potential
216
Repolarization
cell returns to the normal resting membrane potential though negative charged ions entering or postive charged ions leave the cell
217
what reestablishes the resting membrane potential (repolarization)
Na+/K+ ATPase pump
218
Hyperpolarizartion
cell becomes more negative either through negative charged ions entering the cell or positive charged cells leaving (this reestablished resting membrane potential)
219
which of the discussed mechanisms restores resting potential?
leaky channels
220
Integration of Graded Signals: Two types
spatial and temporal summation
221
spatial summation
Interaction
of graded potentials from
different receptors will “meet” at
the axon hillock
* add together to fire an AP
* different sites
222
Temporal Summation
Interaction of graded potentials
that occur at slightly different
times at the axon hillock
* add together to fire an AP
* different times
223
Regulating excitability types
Excitatory Post-Synaptic Potentials and
Inhibitory Post-Synaptic Potentials
224
EPSPs (Excitatory Post-Synaptic Potentials)
change in membrane
potential following influx of
positively charged ions (e.g. Na+).
225
IPSPs (Inhibitory Post-Synaptic Potentials)
-change in membrane
potential following influx of
negatively charged ions (e.g. Cl-)
226
More narrow the dendrite, the _____ the propagation
faster
226
Farther away, ___ the signal to AIS
weaker
