Muscles Flashcards
1
Q
Functions of Muscle Tissue
A
- Produce body movements
- Stabilize body positions
- Store and mobilize substances within the body
- Generate heat
2
Q
Key properties of muscles
A
- Electrical excitability
- contractility
- extensibility
- elasticity
3
Q
Electrical excitability
A
Muscles take on ions changing the electrical potential of the cell membrane thus produce an electrical current along the cell.
Action potential is used to trigger multiple chemical reactions to create a muscle contraction
4
Q
Contractility
A
Action potential generated causes proteins found in muscle called contractile proteins to generate tension and pull on attachment points. This will cause muscle to shorten in length
5
Q
Extensibility
A
Due to the connective tissue present within the muscle, the miracle has a range of motion in which it can stretch out and move without tearing
6
Q
Elasticity
A
Ability of a muscle to return back to its original length after either contraction or extensibility
7
Q
Skeletal muscle
A
- voluntary
- attached to bones and skin of the skeleton
- move bones as well as the skin of the face
8
Q
Cardiac muscle
A
- involuntary
- found only in the heart
- pump blood from the heart into the blood vessels
9
Q
Smooth muscle
A
- involuntary
- found in various organs of the body (mostly hollow organs or organs that have an opening in the center through which other substances travel)
- moves substances within the tube
10
Q
Characteristics of skeletal muscle
A
- long
- thin
- cylindrical in shape
- multinucleated
- striated
- attached via tendons to bones
11
Q
Characteristics of cardiac muscle
A
- short
- fat
- branched
- uninucleated
- striated
- attached to intercalated discs
12
Q
Characteristics of smooth muscle
A
- uninucleated
- no striations
- contain intermediate filaments
- connected to one another via gap junctions
13
Q
Organization of skeletal muscles
A
Myoblasts join together forming immature muscle fiber (cell). Cell will then mature and become mature muscle fiber.
Fusion of multiple myoblasts accts for the mature muscle fiber having multiple nuclei
14
Q
What is the organization of muscle tissue from smallest to largest?
A
- filament
- myofibril
- fiber
- fascicle
- skeletal muscle
15
Q
What connects muscle to bone?
A
Tendons
16
Q
What are the components of connective tissue from smallest (deepest) to largest (most superficial)?
A
- endomysium
- perimysium
- epimysium
17
Q
Wheat is endomysium?
A
Separates individual muscle fibers from one another
18
Q
What is perimysium?
A
Surrounding 10-100 muscle fibers separating them into bundles called fascicles
19
Q
What is epimysium?
A
Outer layer encircling the entire muscle
20
Q
What is a sarcomere?
A
Skeletal muscle fiber is divided into smaller functional units known as a sarcomere
21
Q
Notable components of the sarcomere
A
- sarcolemma
- sarcoplasmic reticulum
- sarcomere
- transverse (T) tubule
- thick filament (myosin)
- thin filament (actin)
- troponin and tropomyosin
- titan filament (elastic)
22
Q
What is a sarcolemma?
A
The plasma membrane of a muscle cell
23
Q
What is a sarcoplasmic reticulum?
A
Stores calcium for the cell
24
Q
What is a sarcomere?
A
Contractile unit from one z-disc to another z-disc
25
What is a transverse (T) tubule?
Unfolding that penetrates all the way through the cell.
Will allow the action potential to penetrate into the inside of the cell
26
What is a thick filament (myosin)?
A contractile protein unit that is shaped like the head of a golf club. The myosin will join to the actin and create the contraction of a muscle fiber.
27
What is a thin filament?
Actin. Contractile protein that resembles beads on a necklace. Actin has an active spot that allows for the binding with myosin to cause a contraction and shortening of the skeletal muscle fiber.
28
What is troponin and tropomyosin?
Regulatory proteins.
Cover up the binding site on the actin proteins. Actin and myosin are not able to join until these 2 regulatory proteins move out the way. The intro of calcium (Ca+) is what is used to move these regulatory proteins out the way
29
What is titan filament (elastic)?
Helps to return the sarcomere to its original shape after contraction has occurred
30
What are the different names structures of the sarcomere?
- A-band
- I-band
- H-zone
- Z-disc (line)
- M-line
31
What is the A-band?
From the beginning of one thick filament to the end of the same thick filament.
This is what creates the dark band.
32
What is the I-band?
From the end of one thick filament to the beginning of the next thick filament.
This is what creates the light band.
33
What is the H-zone?
From the end of one thin filament to the beginning of the next thin filament
34
What is the Z-disc (line)?
Provides the anchorage for the actin and titan filaments
35
What is the M-line?
The line found at the center of the thick filament.
| Provides an anchor for the thick filament.
36
How does the skeletal system play an important role in the contraction of a muscle?
Nervous system connects to muscle fibers through a group of neurons known as motor nerves. Motor neurons are considered efferent nerves as they leave the central nervous system to attach to a skeletal muscle. The motor neuron will carry with it an action potential that the muscle will use to depolarize and initiate its contraction. The signal reached the synapse of the neuron and the target cell muscle fiber, this area is referred to as the neuromuscular junction or motor end plate. At the NMJ the nervous signal will be converted into a chemical called a neurotransmitter, that will be released into the space between the synapse of the motor neuron and the sarcolemma of the muscle fiber.
37
What is the 1st events in the sequence of events that follows the neurotransmitter binding to the sarcolemma?
The synaptic vesicles containing the neurotransmitter (ACh-acetylcholine) will reach the membrane of the synapse and release the ACh into the space between the synapse and the sarcolemma (synaptic cleft)
38
What is the 2nd event in the sequence of events that follows the neurotransmitter binding to the sarcolemma?
The ACh will then bind to ACh receptor proteins present in the sarcolemma (ligand-gated channels)
39
What is the 3rd event in the sequence of events that follows the neurotransmitter binding to the sarcolemma?
When bound on each side of the protein with an ACh the ACh receptor proteins will open and allow an influx of Na+ ions into the muscle fiber
40
What is the 4th event in the sequence of events that follows the neurotransmitter binding to the sarcolemma?
This influx of Na+ ions into the muscle fiber will cause the muscle fiber to depolarize and generate its own action potential
41
What is the 5th event in the sequence of events that follows the neurotransmitter binding to the sarcolemma?
This newly generated action potential will then travel down the T-tubules and into the muscle fiber. As the signal travels down the T-tubule it will pass by the sarcoplasmic reticulum
42
What is the 6th event in the sequence of events that follows the neurotransmitter binding to the sarcolemma?
As the voltage generated by the action potential passes by the sarcoplasmic reticulum it will open up voltage-gated calcium channels. The SR will then release Ca2+ into the cystol of the cell. The Ca2+ will be used in the sliding filament theory to generate the contraction of the muscle
43
What does the sliding filament theory begin with?
Motor nerve
44
What is step 1 of the sliding filament theory?
Synaptic vesicles containing the neurotransmitter (ACh) will reach the membrane of the synapse and release the ACh into the space between the synapse and the sarcolemma (synaptic cleft)
45
What is step 2 of the sliding filament theory?
The ACh will then bind to ACh receptor proteins present on the sarcolemma (ligand-gated channels)
46
What is step 3 of the sliding filament theory?
When bound on each side of the protein with an ACh the ACh receptor proteins will open and allow an influx of Na+ ions into the muscle fiber
47
What is step 4 of the sliding filament theory?
This influx of Na+ ions into the muscle fiber will cause the muscle fiber to depolarize and generate its own action potential
48
What is step 5 of the sliding filament theory?
This newly generated action potential will then travel down the T tubules and into the muscle fiber. As the signal travels down the T tubule it will pass by the sarcoplasmic reticulum
49
What is step 6 of the sliding filament theory?
As the voltage generated by the action potential passes by the sarcoplasmic reticulum and open up voltage-gated calcium channels. The SR will then release Ca2+ into the cystol of the cell. The Ca2+ will be used in the sliding filament theory to generate the contraction of the muscle
50
What is the steps 1-6 of sliding filament theory known as?
Excitation-contraction coupling
51
What is step 7 of the sliding filament theory?
Once the SR releases the Ca2+ into the cystol of the cell, the Ca2+ will make its way to the sarcomere. In the sarcomere the Ca2+ will attach to the regulatory proteins and move them from the binding myosin binding spots on the actin filaments. In this actin has a specific binding spot. This is the only spot that the myosin can attach to and at normal times, it’s is covered by troponin and tropomyosin but in the presence of Ca2+, the troponin and tropomyosin will bind to the calcium instead and move away from the myosin binding spot
52
What is step 8 of the sliding filament theory?
In order for the actin and myosin to bind together, there must be ATP present. The ATP will be hydrolyzed by an enzyme Myosin ATPase and turned into ADP and a phosphate. This release of energy will be used to “cock” the myosin head
53
What is step 9 of the sliding filament theory?
This cocked myosin head will then bind to the actin forming a cross-bridge between the actin and myosin
54
What is step 10 of the sliding filament theory?
The myosin will then undergo a process known as a power stroke where it will release the energy stored and return to the bent, low energy, position
55
What is step 11 of the sliding filament theory?
The power stroke causes the actin to move or slide down the myosin filament
56
What is step 12 of the sliding filament theory?
If calcium remains present, a new cross bridge will be created and the events of 7-10 will repeat think of this like the hand over hand action of pulling on a rope to lift a heavy object. The actin and myosin cross bridging does not allow the progress created to be immediately undone but rather “holds” the proteins in place so the additional power strokes will continue to shorten the muscle and not have the progress immediately undone
57
What is step 13 of the sliding filament theory?
If the calcium is removed from the cystol, then the muscle will undergo a process known as relaxation
58
What is step 14 of the sliding filament theory?
In order for the muscle to stop contracting and begin the sequence of relaxation you have to start at the beginning. Since the muscle contraction began with a neuron, it must also end with a neuron. The first step of relaxation is the stopping of the ACh release
59
What is step 15 of the sliding filament theory?
The next step is the removal of the neurotransmitter from the neuromuscular junction. AChE breaks down the ACh that was previously released and present in the synapse. AChE breaks the ACh down into fragments that can no longer be used to stimulate the sarcolemma
60
What is step 16 of the sliding filament theory?
With ACh no longer present, the ligand-gated channels close and stop the influx of the Na+ ions
61
What is step 17 of the sliding filament theory?
Without the Na+ ions present, the sarcolemma no longer has the electrical charge necessary to open the voltage-gated Ca2+ channels and the SR stops the release of calcium. Without the release of new calcium and having the continued reabsorption by the sarcoplasmic reticulum, the calcium no longer is present in the cystol of the skeletal muscle cell
62
What is step 18 of the sliding filament theory?
In the absence of Ca+ ions the troponin and tropomyosin move back onto the actin covering the myosin binding site. The actin and myosin can no longer bind together and the muscle fiber ceases to produce or maintain a muscle contraction
63
What is step 19 of the sliding filament theory?
In order to return to its original length, the structural protein titin will push apart the z-discs and return them to their original position
64
What does the sliding filament theory require to complete?
ATP
65
What are the 3 ways ATP in the skeletal muscle is created?
- creatine phosphate
- anaerobic glycolysis
- aerobic respiration
66
What is creatine phosphate?
It is one of the ways ATP is created in the skeletal muscle
The conversion of creatine phosphate into creatine helps to catalyze the conversion of ADP into ATP. The ATP generated from this chemical reaction creates around 15 seconds worth of energy giving only short term energy benefits
67
What is anaerobic glycolysis?
It is one of the ways ATP is created in skeletal muscle
During anaerobic glycolysis, glucose in the cystol of the skeletal muscle cell will be converted into pyrrhic acid and then lactic acid. The conversion of glucose into purification acid will generate 2 ATPs. This type of energy creation will give the muscle about 2 minutes of energy
68
What is aerobic respiration?
It is one of the ways ATP is created in skeletal muscle.
If sufficient oxygen is present, glucose can be converted by the cell into ATP through the use of cellular respiration. Aerobic respiration generates 30-32 ATP which is enough energy for several minutes to hours
69
When does muscle fatigue occur?
It happens when skeletal muscles that have been contracted for a prolonged period of time
Also a result of high-intensity, short duration exercise
70
What factors are involved in fatigue?
- Potassium accumulation
- ADP/Pi accumulation
- Fuel depletion
- Electrolyte loss
- Central fatigue
71
What is potassium accumulation?
With an accumulation of potassium in the cell, it makes the electrical potential further away from an action potential and thus further away from muscle contraction
72
What is ADP/Pi accumulation?
The free phosphate will inhibit the release of Ca2+ ions and thus prevent muscle contraction. The presence of ADP will slow the cross-bridge cycling of mechanisms of contraction
73
What is fuel depletion?
Declining levels of muscle glycogen leads to less ATP production
74
What is electrolyte loss?
The loss of electrolyte from sweating will cause a reduction in muscle excitability
75
What is central fatigue?
Muscles generate ammonia as a byproduct which is absorbed into the CNS and slowing motor function. Most of the reasons for central fatigue are still not quite understood
76
How does recovery happen?
Your skeletal muscle will use up oxygen to form ATP. As the muscle uses oxygen, the amount of available oxygen will become depleted. This will cause the RBC to deliver more oxygen to the skeletal muscle. As a result, the RBC will have less and less available oxygen and the oxygen-debt must be repaid before your heavy breathing will cease
77
What metabolic conditions are restored with oxygen pay back?
- convert lactic acid back into glycogen in the liver
- regenerate creatine phosphate and ATP in the muscle fiber
- replace the oxygen that was removed from the myoglobin
78
What is the demand in ATP in skeletal muscle?
Most skeletal muscle contractions are of short duration (few seconds to a few minutes) resulting in lower ATP demands
79
What is the demand for ATP in cardiac muscle?
Demands for ATP are much greater than in skeletal muscle because it must contract over and over until death.
80
How is the ATP in cardiac muscle made?
Most of the ATP created for the heart is done so through aerobic respiration
Without the use of anaerobic glycolysis the heart cannot keep up the demands of ATP without oxygen present
81
What is the demand for ATP in smooth muscle?
Smooth muscle has the lowest demands for ATP due to the ability of myosin to remain attached to actin without use of additional ATP (latch-bridge mechanism)
82
How is the ATP in smooth muscle created?
Make most of its ATP through aerobic respiration, due to the low demands of ATP, there are few mitochondria present
83
What is the primary function of skeletal muscle tissue?
Primarily responsible for moving skeleton and for thermoregulation (increases Jody temp when muscles contract)
84
What is the location of skeletal muscle tissue?
Attaches to bones or sometimes skin; forms external urethral and anal sphincters
85
What is the function of cardiac muscle?
Pumps blood through heart and blood vessels
86
What is the location of cardiac muscle tissue?
Heart wall (myocardium)
87
What is the function of smooth muscle tissue?
Moves and propels materials through internal organs; controls the size of the lumen
88
What is the location of smooth muscle tissue?
Walls of hollow internal organs, such as intestines, stomach, airways, urinary bladder, uterus, and blood vessels; iris of the eye
89
What are the 3 subdivisions of muscle fibers present in skeletal muscle fiber?
- slow oxidative fibers (red)
- fast oxidative-glycolytic fibers (pink)
- fast glycolytic fibers (white)
90
What is slow oxidative fibers (red)?
Lots of myoglobin resulting in the red color; high capacity for generating ATP so resistant to fatigue; ATP generated through aerobic respiration; used for maintaining posture and aerobic exercise
91
What is fast oxidative-glycolytic fibers (pink)?
Many capillaries resulting in pink color; intermediate capacity for creating ATP; creates ATP for through both aerobic and anaerobic respiration; intermediate resistance to fatigue; used for walking and sprinting
92
What is the fast glycolytic fibers (white)?
Few capillaries resulting in white color; low capacity for generating ATP so low resistance to fatigue; used for rapid/intense movements of short duration
93
What is the definition of contraction?
Ability of the muscle to shorten
94
What makes the muscle fibers stronger or more fine of movement?
The more muscle fibers we have the stronger or more fine of movement the muscle can produce
95
What makes a contraction last longer?
Having multiple motor units allows a muscle to alternate between motor unit giving the muscle the ability to sustain a contraction for longer
96
What is the Frank Starling Law?
The law states there is an optimal length to a muscle that creates an optimal tension and thus optimal force of contraction
97
What is the length-tension relationship?
There is a set relationship that can be seen between muscle length and muscle tension
98
What is muscle tone?
Is the ability of a muscle to maintain a partial state of contraction that maintains optimum muscle length for contraction
99
What is myogram?
Is a graphic representation of the timing and strength of a muscle contraction
100
How is a twitch generated?
A muscle twitch can be generated when we have a quick cycle of contraction and relaxation as a result of one single stimulus reaching or surpassing threshold
101
What is latent period?
When a stimulus is created, there will be a time of about 2 milliseconds from the onset of the stimulus to the onset of the twitch contraction
102
True or false. The latent period represents the time needed to allow sodium ions to enter the cell and open the voltage-gated calcium channels thus leading to a muscle contraction, known as the excitation-contraction coupling
True
103
What is contraction phase?
The resulting contraction of the muscle where length changes is known as contraction phase
104
What is relaxation phase?
The contraction phase is then followed by the relaxation phase, where calcium and sodium levels fall and the muscle returns to its original length
105
What is summation?
Muscle receiving multiple subthreshold stimuli that can be added together to create an above threshold (Supra threshold) signal. This adding together is known as summation
106
Central Nervous System
Location: Consists of brain and spinal cord.
Function: receiving the sensory info, processing and integrating it, and then mediating a response
107
Peripheral Nervous System
Rest of the nerve tissue including those in the periphery, as well as the cranial and spinal nerves
108
Afferent division
Direction is from sensory receptors to the control integration centers in the CNS
109
Efferent division
Consists of all motor pathways that will carry outgoing info exiting from the CNS upon integration towards the motor effectors which include muscles and glands; resulting in an effect or response
110
White matter
Consists of myelinated fibers
CNS: white matter is made of myelinated tracts
PNS: white matter is made of myelinated nerves
111
Gray matter
Made of unmyelinated fibers
CNS: gray matter in CNS known as nuclei
PNS: gray matter in PNS known as ganglia
112
What are nerves?
Nerves are bundles of peripheral nerve fibers that are bound together by three primary layer of connective tissue known as endoneurium, perineurium, epineurium
113
What is the endoneurium?
Surrounds each nerve fibers
114
What is the perineurium?
Surround each fascicle which is basically a bundle of nerve fibers which are individually wrapped with their own endoneurium
115
What is the epineurium?
Surrounds several fascicles along with the blood vessels that nourish them to form a complete nerve
116
What are tracts?
These are not surrounded/covered by the connective tissue that is normally found in the nerves
117
Neurons
Excitable cells that form the wiring of the nervous system and conduct information/impulses through
118
Glial cells
Not excitable as in the case of neurons, but rather are supportive cells. There are several types of glial cells in both the CNS and PNS. Glial cells are more abundant than neurons, by about 10 times more glial than neuron cells
119
What is the inner layer (in order from outer to inner) of protection composed of for the brain and spinal cord?
Three membrane are called meninges
1. Dura mater
2. Arachnoid mater
3. Pia mater
120
What is the dura mater?
Most superficial meninge of the 3. Composed of strong white fibrous tissue and is also the inner periosteum of the cranial bones
121
What is the arachnoid mater?
Spider web like layer that is found between Duda mater and pia mater
122
What is the pia mater?
Innermost layer of the 3 containing blood vessels, and attached to the surface of the brain and spinal
123
What is the main distinction between spinal cord and brain meninges?
Cranial dura mater has 2 layers while spinal dura mater has 1
124
What are the 2 layers of the cranial dura mater known as?
Periosteal layer, which is the outer layer that is equivalent to the periosteum in the cranial bones, and inner meninges layer
125
What is the meningeal layer?
One that continues and extends into the spinal cord
126
Meningeal layer of the dura that creates folds inward
Crates separation between the major parts of the brain from one another and poses limitations on the movement of the brain such as, someone goes through physical trauma
127
What is flax cerebri?
Creates a partition between the two cerebral hemispheres
128
What is the tentorium cerebelli?
Separates the cerebellum from the cerebellum
129
What is the falx cerebelli?
Separates the 2 halves of hemispheres of the cerebellum
130
What’s the the 3 spaces between the meninges?
1. Epidural space
2. Subdural space
3. Subarachnoid space
131
What is the epidural space?
This layer is on the dura and in the spinal cord it contains a cushion of fat that provides support, while in the brain there is normally no epidural space since the dura mater is co timeous with the periosteum on the inner surface of the skull bones
132
What is the subdural space?
Found beneath the dura in between the dura mater and the arachnoid mater, and it contains small amounts of a serous fluid that acts as a lubricant
133
What is the subarachnoid space?
This space is found below the arachnoid, but it is above the pia, and this space contains the CSF (cerebrospinal fluid)
134
What is the function of CSF?
- Cushion of fluid around the brain and spinal cord.
- Buoyancy for the brain
- protects against jolts
- provides chemical stability by monitoring changes in the internal chemical environment
135
How much CSF does the brain produce a day?
500ml
136
How much CSF can you find in the brain at a given time?
Fluid undergoes continuous reabsorption and one can only find between 100 and 160ml
137
How does CSF travel through the brain?
- flows through brain ventricles
- circulates in the subarachnoidal space
- ultimately will get tea sorbet by the arachnoid grandulations (arachnoid villi)
138
Structural classifications of neurons
- Multipolar neurons
- bipolar neurons
- unipolar neurons
139
What are multipolar neurons?
These neurons possess one axon and multiple dendrites. These are the most common types of neurons. They make up most of the neurons of the spinal cord and brain
140
What’s re the bipolar neurons?
These possess only one axon and one dendrite. These types of neurons are found in the olfactory cells of the nose, retina, and ear
141
What are the unipolar neurons?
These possess only one process that leads away from the soma. Another name that is associated with these types of neurons is pseudounipolar because they begin as bipolar neurons in the embryo but then 2 processes end up merging and fusing into one as the neuron matures.
Ex. Neurons that transmit signals to the spinal cord for senses such as touch and pain, and they always carry info towards the CNS
142
Functional classification of neurons
- sensory neurons (afferent neurons)
- motor neurons (efferent neurons)
- interneurons
143
Functional classification: what are sensory neurons?
Specialized to detect stimuli and transmit info and msgs regarding the stimuli including heat, pressure, chemicals, light among others to the CNS
144
Functional classification: what are motor neurons?
Specialized to carry msgs from the CNS to the effectors; muscles and glands
145
Functional classification: what are interneurons?
Located in the CNS, and they carry impulses/connect between the sensory neurons and the motor neurons, thus connecting both pathways together
146
Glial cells of the CNS
- astrocytes
- Oligodendrocytes
- microglial cells
- ependymal cells
147
What are astrocytes?
Most abundant of the glial cells. They create the blood brain barrier and perform many functions including secretion of nerve growth factors, promotion of synapse formation, regulation of composition of tissue fluid among many others
148
What are oligodendrocytes?
Create the myelin sheath in the CNS
149
What are microglial cells?
Have immune responsibilities and are small macrophages. They destroy foreign matter, pathogens and microorganisms, as well as dead nervous tissue
150
What are ependymal cells?
Create CSF (cerebrospinal fluid)
151
Glial cells of the PNS
- Schwann cells
| - satellite cells
152
What are Schwann cells?
Create the myelin sheath in the PNS
153
What are satellite cells?
Provide support for the nerves of the PNS
154
What is the function of the myelin sheath?
Insulation layer around the nerve fibers
155
What is the myelin sheath made up of?
20% protein and 80% lipid
156
What does the myelin sheath begin to form?
Process of formation of myelin sheath is called myelination, and it starts in the 14th weeks of fetal development
157
4 types of ion channels
- leak channels
- ligand-gated channels
- mechanically-gated channels
- voltage-gated channels
158
What are leak channels?
These are leakage channels that alternate between open and closed randomly. These are located in most of the cells including dendrites, cell bodies, and axons of all types of neurons
159
What are ligand-gated channels?
These will respond to chemical stimuli (whereby ligand/chemicals bind to receptors). They can be found in the dendrites of some sensory neurons such as pain receptors, and dendrites and cell bodies of interneurons and motor neurons
160
What are mechanically-gated channels?
These respond to mechanical vibration, pressure, touch, and stretching stimuli. They are located in the dendrites of some sensory neurons such as touch receptors, pressure receptors and pain receptors
161
What are voltage-gated channels?
These respond to direct changes in membrane potential. They are located in axons of all types of neurons
162
What is a rest membrane potential?
The membrane of a non-conducting neuron is positive outside and negative inside and is referred to as resting membrane potential
163
What are the processes that result from resting membrane potential?
Unequal distribution of ions/electrolytes between the intracellular fluid and extracellular fluid across the cell membrane with more positive ions being found on the outside
164
How do we get more positive ions outside?
- selective permeability of the neurons membrane to Na+ and K+ with low sodium permeability due to the presence of a small amount of sodium leak channels. These sodium permeability of the cell membrane means that it allows for some ions to live easier than others.
- anions not being able to leave the cell
- Na+/K+ pumps
165
What is a synapse?
Area of communication where signals are transmitted between the two neurons that are communicating
166
What is the presynaptic neuron?
One that releases the neurotransmitter
167
What are postsynaptic neurons?
Responds to the release of the neurotransmitter
168
What are the 2 types of synapses?
- Electrical synapse
| - chemical synapse
169
What are electrical synapses?
Occurs between neurons that are connected and joined through gap junctions that will allow for ions to diffuse freely from one cell to the next. This allows for faster communication, synchronization, and coordination since the action potentials conduct directly through the gap junctions. Here the cell membrane and the cytoplasm are functionally continuous. And as such the action potential can simply move along the postsynaptic plasma membrane as if it was part of the same cell. However the downside of this type of synapses is that doesn’t allow for integration of info and decision-making. This type of synapse is found between cardiac muscle cells, some types of smooth muscles and some regions of the brain
170
What are chemical synapses?
They release a chemical known as a neurotransmitter, which mediates the signaling from the presynaptic neuron to the postsynaptic, and unlike electrical impulses these will mediate learning and memory. They are also considered potential targets for numerous prescription drugs
171
The 3 main structures that make-up the chemical synapse
- synaptic knob
- synaptic cleft
- the cell membrane of the postsynaptic neuron
172
What is a synaptic knob?
Bulge that is found at the end of presynaptic neuron and contains many vesicles that will contain the neurotransmitter molecules
173
What is a synaptic cleft?
Small space that is filled with interstitial fluid, and is the site where the neurotransmitters will be released from the synaptic knob
174
What is the cell membrane of the postsynaptic membrane
Contains membrane proteins that will act as receptors, allowing the binding of the neurotransmitters an initiating the responses in the postsynaptic cell
175
What are the 2 types of neurotransmitter receptors?
- ionotropic
| - metabotropic
176
What is a ionotropic neurotransmitter receptor?
Neurotransmitter binding site and ion channel are parts of the same protein
177
What is a metabotropic neurotransmitter receptor?
Binding site and ion channel are parts of different proteins
178
5 main chemical classes
- acetylcholine (ACh)
- amines
- amino acids
- other small molecules
- neuropeptides
179
What is acetylcholine (ACh)?
Neuromuscular junctions, most synapses of autonomic nervous system, retina, and many parts of the brain; excites skeletal muscle, inhibits cardiac muscle, and has excitatory and inhibitory effects on smooth muscle and glands depending on location
180
What is glutamate?
Cerebral cortex and brain stem; accounts for about 75% of all excitatory synaptic transmission in the brain; involved in learning and memory
181
What is glycine?
Inhibitory neurons of the brain, spinal cord, and retina; most common inhibitory neurotransmitter in the spinal cord
182
What is GABA?
Thalamus, hypothalamus, cerebellum, occipital lobes of cerebrum, and retina; the most common inhibitory neurotransmitter in the brain
183
What is norepinephrine?
Sympathetic nervous system, cerebral cortex, hypothalamus, brain stem, cerebellum, and spinal cord; involved in dreaming, walking, and mood; excites cardiac muscle; can excite or inhibit smooth muscle and glands depending on location
184
What is epinephrine?
Hypothalamus, thalamus, spinal cord, and adrenal medulla; effects similar to those of norepinephrine
185
What is dopamine?
Hypothalamus, lambic system, cerebral cortex, and retina; highly concentrated in substantia nigra of midbrain; involved in elevation of mood and control of voluntary movement
186
What is serotonin?
Hypothalamus, lambic system, cerebellum, retina, and spinal cord; also secreted by blood platelets and intestinal cells; involved in sleepiness, alertness, thermoregulation, and mood
187
What is histamine?
Hypothalamus; also a potent vasodilator released by mast cells of connective tissue and basophils of the blood
188
What is cholecystokinin?
Cerebral cortex and small intestine; suppresses appetite
189
What is B-endorphin?
Digestive tract, spinal cord, and many parts of the brain; also secreted as a hormone by the pituitary; suppresses pain; secretion rises sharply during labor and delivery and in response to other pain situations
190
What are enkephalins?
Hypothalamus, limbic system, pituitary, pain pathways of spinal cord, and nerve endings of digestive tract; act as analgesics (pain relievers) by inhibiting substance P; inhibit intestinal motility; modulate immune responses
191
What is substance P?
Basal nuclei, midbrain, hypothalamus, cerebral cortex, small intestine, and pain-receptor neurons; mediates pain transmission
192
What’s re the 3 ways neurotransmitters can be removed?
- diffusion
- enzymatic degradation
- reuptake by cells
193
In removing a neurotransmitter what happens in diffusion?
Whereby some of the neurotransmitters will simply diffuse away from the synaptic cleft and away from the receptors so that it has no effect or impact
194
In removing a neurotransmitter what happens in enzymatic degradation?
Here enzymes will break down the neurotransmitter (ex. Acetylcholinesterase will break down ACh in the synaptic cleft)
195
In removing a neurotransmitter what happens in reuptake by cells?
Here the neurotransmitters are transported and reabsorbed back into the neuron that released them or to neighboring neuroglia cells through transport proteins
196
What’s the the 2 types of summation?
- spatial summation
| - temporal summation
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What is spatial summation?
Summation of postsynaptic potentials I
in response to stimuli that happen at different sites in the membrane of the postsynaptic cell at the same time. A single synapse may produce a weak signal but multiple synapses will act together and can achieve threshold
198
What is temporal summation?
Happens when an individual synapse produces EPSPs so fast that each one is generated prior to fading of the previous ones. This enables the EPSPs to add up overtime to fire up and result in an action potential
