Biological Processes in the Brain Flashcards
(280 cards)
1
Q
What are neurons?
A
Specialized cells that transmit and process information from one part of the body to another
◦ They are the basic functional structural unit of the nervous system
2
Q
What are action potentials?
A
The information from neurons which take the form of electric chemical impulses
◦ The structure of neurons is highly specialized to transmit and process action potentials, which are the chemical signals of the nervous system
3
Q
What happens when an action potential reaches the end of an axon at a synapse?
A
The signal is transformed into chemical signal with the release of the neurotransmitter into the synaptic cleft, a process known as synaptic transmission
4
Q
What is synaptic transmission?
A
When an action potential reaches the end of an axon at a synapse, the signal is transformed into a chemical signal with the release of neurotransmitter into the synaptic cleft
5
Q
What is the structure of neurons?
A
◦ They have a central cell body called the stoma
◦ Lender projections called axons and dendrites, which extend from the cell body
◦ They will only have one axon, but can have many dendrites
◦ Axons can branch multiple times and terminate in synaptic knobs that form connections with target cells
◦ They have a nucleus within the cell body and an axon helix leading to the nodes of Ranveer that lead to synaptic knobs
6
Q
What is a Soma?
A
The central cell body of a neuron which contains the nucleus and is where most of the biosynthetic activity of the cell takes place
7
Q
What are axons?
A
Slender projections that extent from the cell body in a linear line
8
Q
What are dendrites?
A
Slender projections that extend from the cell body can be numerous
9
Q
How many axons can a neuron have and how many dendrites?
A
They will only have one axon, but can have many dendrites
10
Q
What are bipolar neurons?
A
Neuronss with only one dendrite
11
Q
What are multipolar neurons?
A
Neurons with many dendrites
12
Q
A
13
Q
How do neurons carry action potentials?
A
They generally carry action potential in one direction
14
Q
How are signals received and transmitted?
A
Dendrites receive signals and axons carry action potential away from the cell body
◦ When action potential travel down an axon and reach the synaptic knob, chemical messengers are released and travel across a very small gap called the synaptic cleft to the target cell
15
Q
Where do axons terminate?
A
In synaptic knobs
16
Q
What are synaptic knobs?
A
The termination of axons that form connections with target cells
17
Q
What is a synaptic cleft?
A
A small gap at the end of the synaptic knob between it and the target cell
18
Q
What is the difference between a neuron and a nerve?
A
◦ A neuron is a single cell
◦ A nerve is a large bundle of many different axons from different neurons
19
Q
What is the resting membrane potential?
A
And electrical potential across the plasma membrane of approximately -70 mV with the interior of the cell negatively charged with respect to the exterior of the cell
20
Q
What are the two primary membrane proteins that are required to establish the resting membrane potential?
A
◦ The Na+/K+ ATPase
◦ The potassium leak channels
21
Q
What is the function of the NA+/K+ ATPase?
A
It pumps, three sodium ions out of the cell and two potassium ions into the cell with the hydrolysis of one ATP molecule
◦ It creates a sodium gradient with high sodium outside the cell in a potassium gradient with high potassium inside the cell
22
Q
What are leak channels?
A
Channels that are openall the time, and it simply allow ions to “leak” across the membrane according to their gradient
23
Q
What are potassium leak channels?
A
They allow potassium, but no other ions, to flow down their gradient out of the cell
24
Q
What is the combined outcome of the NA+/K+ ATPase and the potassium leak channels?
A
A loss of many positive ions leaves the interior of the cell with a net negative charge
◦ Approximately -70 MV more negative than the exterior of the cell
◦ This difference is the resting membrane potential
25
What does the resting membrane potential establish?
A negative charge along the interior of axons making the cell polarized
26
What does it mean for a cell to be polarized?
Negative on the inside and positive on the outside
27
What does an action potential do to the membrane potential?
Drops the resting membrane potential and is a change from -70 mV to a less negative or even positive potential
28
What is depolarization?
Occurs in the plasma membrane that travels along an axon
◦ Is a change from -70 mV to a less negative or even positive potential
29
What occurs after depolarization?
Repolarization
30
What does repolarization do?
Returns the membrane potential to normal (from a positive value back to -70 mV)
31
During an action potential, how does the change in membrane potential occur?
It is caused by a movement of ions into an out of the neuron through ion channels
◦ It is therefore an electrochemical impulse
32
What are the steps to an action potential?
1. Resting membrane potential
2. Depolarization
3. Repolarization
4. Hyperpolarization (also called the refractory period)
5. Return to resting membrane potential.
33
What occurs during depolarization?
The voltage gated sodium channels located in the plasma membrane of an axon open to allow sodium ions to flow down their gradient into the cell and depolarize that section of the membrane
34
What has to happen for an action potential to occur?
The threshold potential has to be hit during depolarization
35
What happens once the threshold potential has been hit during depolarization?
The channels are open, fully and sodium flows into the cell, down its concentration gradient, depolarizing that section of the membrane to about +30 mV before inactivating
◦ The voltage gated sodium channel are opened, while the voltage gated potassium channels remain closed
36
What is repolarization?
The voltage gated sodium channels are inactivated in the voltage, gated potassium channels open
◦ Polarization reestablishes the original resting membrane potential
37
During repolarization, how long do the voltage gated sodium channels remain inactive?
Until the membrane potential near resting values again
38
During repolarization, what happens with the voltage gated potassium channels
The voltage gate of potassium channels open more slowly than the voltage, gated sodium channels and stay open longer
◦ They open in response to a membrane depolarization, and as potassium leaves the cell down its concentration gradient. The membrane potential returns to the negative values and overshoot resting potential by about 20 mV to about -90 mV
◦ at this point the voltage gated potassium channels close
39
What is myelin?
The insulating sheath that the axons of many neurons are wrapped in
40
What are Schwann cells?
A type of Galileo cell that exist in conjunction with neurons, wrapping layers of specialized membrane around the axons (called myelin)
41
Where are Schwann cells found?
In the peripheral nervous system
42
If one cells are only found in the peripheral nervous system, what happens in the central nervous system?
My nation of axons is accomplished via similar cells called oligo dangerous sites
43
What happens when an axonal membrane is covered with myelin?
No ions can enter or exit a neuron that is covered in myelin
◦ Therefore, there is no membrane depolarization and no voltage gated sodium channels in these regions
44
What are nodes of Ravier?
The periodic gaps in the Milan sheath
45
Where are the voltage gated, sodium potassium channels concentrated in myelinated axons?
In the periodic gaps that are not myelinated, called the nodes of Ravier
46
What is the purpose of the myelin sheath?
It dramatically speeds up the movement of action potential by forcing the action potential to jump from node to node
◦ This jumping conduction is called saltatory conduction
47
What does saltatory conduction?
The rapid jumping conduction of myelinated axons
48
What are Glial cells?
Specialized, non-neuronal cells, the typically provide structural and metabolic support to the neurons
49
Where are Schwann cells located?
PNS
50
Where are all dangerous sites located?
CNS
51
Where are astrocytes located?
CNS
52
Where are microglia located?
CNS
53
Where are ependymal cells located?
CNS
54
What is the primary function of Schwann cells?
Form myelin - which increase the speed of conduction of APs along axons
55
What is a primary function of oligodendrocytes?
Form myelin - which increase the speed of conduction of APs along axons
56
What is the primary functions of astrocytes?
◦ Guide neuronal development
◦ Regulate synaptic communication via regulation of neurotransmitter levels
57
What is the primary function of microglia?
Removed dead cells and debris
58
What is the primary function of Ependymal cells?
Produce and circulate cerebrospinal fluids
59
During the action potential, the movement of potassium and sodium ions across the membrane through voltage gated channels is…
Passive; driven by gradient
60
What is the equilibrium potential?
Is the membrane potential at which the driving force of the gradient does not exist
◦ There is no net movement of ions across the membrane
◦ The equilibrium potential is specific for a particular ion (and differs for sodium and potassium)
61
What is the equilibrium potential for sodium and potassium?
◦ Sodium: +50 mV (is positive)
◦ Potassium: -90 mV (is negative)
62
Why is the equilibrium potential of sodium positive?
Because that NA+/K+ ATPase pumps three sodium ions out of the cell and two potassium into the cell meaning, that the interior of the cell has less sodium than outside of it therefore, sodium ions are driven inward by their concentration gradient
63
What happens if the interior of the cell is too positive?
The positively charged ions are repelled and the electrical gradient would drive sodium out
64
Why is the potassium equilibrium gradient negative?
Because the NA+/K+ ATPase pumps, three sodium ions out of the cell and two potassium ions into the cell, meaning that the interior of the cell has more potassium than the exterior, and therefore potassium is driven out of the cell by its concentration gradient
65
What happens if the interior of the cell is two negative?
Positively charge ions cannot escape the attraction and the electrical gradient would drive potassium in
66
What equation is used to determine the equilibrium potential across a membrane?
The Nernst equation
Eion = (RT/zF)ln ([X]outside/[X]inside)
67
In the Nernst equation
◦ What does Eion mean?
◦ What does R mean?
◦ What does T mean?
◦ What does z mean?
◦ What does F mean?
◦ What does [X]inside mean?
◦ What does [X]outside mean?
◦ Eion is the equilibrium potential for the ion
◦ R is the universal gas constant
◦ T is the temperature in Kelvin
◦ z is the valence of the ion
◦ F is Faraday's constant
◦ [X]inside is the concentration of the ion on the inside of the membrane
◦ [X]outside is a concentration of ion on the outside of the membrane
68
What does a relative concentrations of ions on each side of the membrane create in the Nernst equation?
The chemical gradient
69
What does the valance help determine in the Nernst equation?
The valence (charge of the ion) helps determine the electrical gradient
70
What would happen if the cell were completely permeable to potassium?
The resting potential would be about -90 mV
71
What can be inferred from the resting potential being close to the potassium equilibrium potential?
That there are a large number of potassium leak channels in the membrane, and that the cell at rest is almost completely permeable to potassium
72
The resting potential being slightly more positive than -90 mV is indicative of what?
There are a few sodium leak channels, allowing sodium in
73
What limits how soon a neuron can conduct an action potential after another one has passed?
The period of refraction
74
What does refractory mean?
That the passage of one action potential makes the neuron non-responsive to membrane depolarization and unable to transmit another action potential for a short period of time
◦ There are two parts of the refractory period
75
What are the two periods of refractory?
◦ The absolute refractory period
◦ The relative refractory period
76
Differentiate between the absolute refractory period and the relative refractory period
◦ During the absolute refractory period, a neuron will not fire another action potential no matter how strong a membrane depolarization is induced. This is because the voltage gated sodium channels have been inactivated after depolarization and they will not be able to be opened again until the membrane potential reaches the resting potential, and the sodium channels have returned to their "closed" state
◦ During the relative refractory period, a neuron can be induced to transmit an action potential, but the depolarization required is greater than normal because the membrane is hyperpolarized. When polarization occurs, there is a brief period in which the membrane potential is more negative than the resting potential caused by the voltage gated potassium channels that have not yet closed. Because it is further from threshold, a greater stimulus is required to open the voltage, gated sodium channels to start an action potential
77
What does it mean for a membrane to be hyperpolarized?
The membrane potential is more negative than the rusty membrane potential because the voltage potassium channels have not yet closed
◦ If an stimulus occurs while it is in hyperpolarization, action potential can occur, but a greater stimulus is required to open the voltage gated at sodium channels to start an action potential
78
What is a synapse?
A junction between the axon terminus of a neuron and the dendrites, Soma, or axon of a second neuron
◦ It can also be a junction between the axon terminus of a neuron in an organ
◦ There are two types of synapsis: electrical and chemical
79
What are the two types of synapsis?
Electrical and chemical
80
Differentiate between an electrical synapse and a chemical synapse
◦ Electrical synapsis: occur when the cytoplasm of two cells are joined by gap junctions. If the two cells are joined by an electrical synapse, an action potential will spread directly from one cell to the other. Electrical synapses are not common in the nervous system although they are quite important and propagating action potential and smooth muscle and cardiac muscle
◦ Chemical synapses are found at the end of axons where they meet their target cell in the nervous system. An action potential is converted into a chemical signal. There are eight steps involved in the transmission of a signal across a chemical synapse in the nervous system, as well as at the junctions of neurons with other types of cells, such as skeletal cells.
81
What are the eight steps involved in the transmission of a signal across a chemical synapse?
1. In action potential reaches the end of an axon, the synaptic knob
2. Depolarization of the septic membrane, opens the voltage, gated calcium channels
3. Calcium influx into the presynaptic cell causes exocytosis of neurotransmitter stored in the secretary vesicles
4. Neurotransmitter molecules to diffuse across the narrow synaptic clef (space between cells)
5. Neurotransmitter binds to the receptor proteins in the postsynatpic membrane – these receptors are ligand-gated ions channels
6. The opening of these ion channels in the postsynaptic cell alters the membrane polarization
7. If the membrane depolarization of the postsynaptic cell reaches the threshold of voltage, gated, sodium channels, and action potential is initiated.
8. Neurotransmitter in the synaptic cleft is degraded and/or removed to terminate the signal.
82
What are the four steps that occur in a presynaptic neuron during an action potential?
1. Voltage-gated calcium channels open
2. Influx of calcium
3. Exocytosis of secretary vesicle
4. Release of neurotransmitter into the synaptic cleft
83
What are the three steps that occur in the postsynaptic neuron during an action potential?
1. Neurotransmitter binds to the ligated-gated ion channel
2. Ions enter postsynaptic cell
3. Membrane polarization is increased or decreased
84
What is the neuromuscular junction?
The space between neurons and skeletal muscle
◦ Usually, an example of a chemical synapse
85
What neurotransmitter is released at the neuromuscular junction?
Acetylcholine (ACh)
86
What role does the neurotransmitter of acetylcholine play at a chemical synapse?
◦ When an action potential reaches a synapse, acetylcholine is released into the synaptic cleft
◦ choline binds to the acetylcholine interceptor on the surface of the postsynaptic cell membrane
◦ With acetylcholine binds to its receptor, their receptor opens it's associated sodium channel, allowing sodium to flow down gradient into the cell, depolarizing the post excel membrane
◦ Acetylene in the synaptic cleft is degraded by the enzyme acetylcholesterase (AChE)
87
What does it mean if a neurotransmitter is called excitatory?
If a neurotransmitter, such as acetylcholine, opens a channel that depolarizes the postsynaptic membrane
88
What does it mean if a neurotransmitter is called inhibitory
Any neurotransmitter that make the postsynaptic membrane potential more negative than the resting potential, or hyperpolarized
89
What determines the effect on the postsynaptic cell?
It is not the neurotransmitter, but the receptor for the neurotransmitter and it's associated ion channel
90
Are neurotransmitters always excited or inhibitory?
It depends on the situation, they can be excitatory in some cases and inhibitory and others
91
What is an actual potential in a neuron considered?
And all or nothing event
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93
What does it mean for an action potential to be considered an "all or nothing" event?
Once an action potential is initiated in a neuron, it will propagate to the end of the axon at a speed and magnitude depolarization that does not vary from one actual potential or another
◦
94
What factors influence, whether or not an action potential will fire?
◦ It depends on all of the effects on a neuron, both excitatory and inhibitory
◦ It can depend on two different types of summation: temporal summation and spatial summation
95
What is summation?
The addition of stimuli
◦ Can be temporal, summation, or spatial summation
96
What are excitatory postsynaptic potentials (EPSPs)
Excitatory neurotransmitters cause postsynaptic depolarization
97
What are inhibitory postsynaptic potentials (IPSPs)?
Inhibitory neurotransmitters inhibit postsynaptic depolarization
98
Differentiate between temporal summation and spatial summation
◦ Temporal summation occurs when a presynaptic neuron fires action potential so rapidly that the EPSP's or the IPSP's pile up on top of each other, and if the additive effect is enough, they might reach the threshold of depolarization
◦ Spatial summation is when the EPSP is in the IPSPs from all of the synapsis on the postsynaptic membrane or some that a given moment in time. If the total of them causes the synaptic membrane to reach the threshold voltage, action potential will .
99
What is a sensory function of the nervous system?
Receiving information, which is carried out by the peripheral nervous system
100
What is the integrative function of the nervous system?
Processing information, which is carried out by the central nervous system
101
What is the motor function of the nervous system?
Acting on information received, which is carried out by the peripheral nervous system
102
What are motor neurons?
They carry information from the nervous system towards organs, which can act upon the information, known as effectors
◦ Motors would carry information away from the central nervous system and nerve factors are called a efferent neurons
103
What are effectors?
Organs which can act upon information
104
What are sensory neurons?
Neurons which carry information towards the central nervous system, and are called afferent neurons
105
What is a reflex?
A direct motor response to a sensory input which occurs without conscious thought
◦ There are different examples, such as the muscle stretch reflex, and the monosynaptic arc reflex
106
What occur occurs with the muscle stretch reflex?
A sensory neuron detect stretching of a muscle
◦ The sensory neuron has a long dendrite and a long axon, which transmits an impulse to the motor neuron cell body in the spinal cord
◦ The motor neurons, long axon synapses with the muscle that was stretched and causes it to contract
◦ This is why the quadriceps muscle contracts when the patellar tendon is stretched by tapping with a reflex hammer
107
What is a monosynaptic archery reflex?
A reflex involving only two neurons and one synapse
108
What is an inhibitory interneuron?
A short neuron which forms an inhibitory synapse with a motor neuron innervating the hamstring muscle, for example
◦ When the sensory neuron is stimulated by stretch, it stimulates both the quadriceps motor neuron in the inhibitory neuron to the hamstring motor neuron
◦ As a result to the quadriceps contracts in the hamstring relaxes
109
What is a reciprocal inhibition?
Concurrent relaxation of the hamstring and contraction of the quadriceps
110
The peripheral nervous system can be subdivided into functional divisions, including what?
The somatic division and the autonomic division
111
What is the autonomic division of the peripheral nervous system?
It is concerned with digestion, metabolism, circulation, perspiration, and other involuntary processes
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What is the somatic division of the peripheral nervous system?
The portion concerned with conscious sensation and deliberate, voluntary movements of skeletal muscles
114
What do both of the somatic and the autonomic divisions of the peripheral nervous system include
afferent and efferent functions, although the sources of input in the target of efferent nerves are different
115
The affair portion of the autonomic division of the peripheral nervous system is further split into two subdivisions, what are they?
The sympathetic and the parasympathetic
116
Differentiate between what happens when the parasympathetic system is activated vs. the sympathetic system
◦ When the sympathetic system is activated, the bodies prepared for "fight or flight"
◦ Note that many sympathetic affects result from the release of epinephrin to the bloodstream by the adrenal medulla
◦ When the parasympathetic system is activated, the body is prepared to "rest and digest"
117
How do the effects of parasympathetic versus sympathetic differ on the digestive system, specifically the;
◦ Glands
◦ Motility
◦ Sphincters
For parasympathetic:
◦ Glands: stimulation
◦ Motility: stimulation (stimulates digestion)
◦ Sphincter: relaxation
For sympathetic:
◦ Glands: inhibition
◦ Motility: inhibition (inhibits digestion)
◦ Sphincters: contraction
118
How do the effects of parasympathetic and sympathetic differ on the urinary system, specifically the;
◦ Bladder
◦ Urethral sphincter
For parasympathetic:
◦ Bladder: contraction (stimulates urination)
◦ Urethral sphincter: relaxation (stimulates urination)
For sympathetic:
◦ Bladder: relaxation (inhibits urination)
◦ Urethral sphincter: contraction (inhibits urination)
119
How do the effects of the parasympathetic and sympathetic systems differ for Brook bronchial smooth muscle
For parasympathetic:
◦ Bronchial smooth muscle: contraction (closes airways)
For sympathetic:
◦ Bronchial smooth muscle: relaxation (opens airways)
120
How do the effects of parasympathetic and sympathetic differ for the cardiovascular system, specifically the;
◦ Heart rate in contractility
◦ Blood flow, skeletal muscle
For parasympathetic:
◦ Heart rate and contractility: decreased
◦ Blood flow of skeletal muscles: not impacted
For sympathetic:
◦ Heart rate and contractility: increased
◦ Blood flow to skeletal muscles: increased
121
How do the effects of the parasympathetic and the sympathetic systems differ for the skin?
For parasympathetic:
◦ Skin: not effected
For sympathetic:
◦ Skin: sweating and general, vasal constraction, and emotional vasodilation (blushing)
122
How do the effects of the parasympathetic and sympathetic systems differ for the eye, specifically the;
◦ Pupil
◦ Muscles controlling lenses
For the parasympathetic:
◦ Pupil: constriction
◦ Muscles controlling lenses: near visual accommodation
For sympathetic:
◦ Pupil: dilation
◦ Muscles controlling lenses: accommodation for far vision
123
How do the effects of the parasympathetic and sympathetic systems impact the adrenal medulla?
For parasympathetic:
◦ Adrenal medulla: not impacted
For sympathetic:
◦ Adrenal medulla: release of epinephrine
124
How did the effect effects for the parasympathetic and sympathetic systems differ for the genitals?
For parasympathetic:
◦ Genitals: erection/lubrication
For sympathetic:
◦ Genitals: ejaculation/orgasm
125
All neurons entering and exiting the central nervous system are carried by what?
◦ 12 pairs of cranial nerves
◦ 31 pairs of spinal nerves
126
What are cranial nerves?
They convey sensory and motor information to and from the brainstem
127
What are spinal nerves?
They convey sensory and motor information to and from the spinal cord
128
What is the vagus nerve?
An important example of a cranial nerve
◦ The effects of the nerve upon the heart and G.I. track are to decrease the heart rate and increase G.I. activity
◦ It is part of the parasympathetic division of the autonomic nervous system
◦ It is a bundle of axons that ending ganglia on the surface of the heart, stomach, and other visceral organs
◦ The many axons constituting the vagus nerve are pre-ganglionic and come from cell bodies, located in the CNS
129
What do all somatic motor neurons do?
They all;
◦ innervate skeletal muscle cells
◦ use ACh as their neurotransmitter
◦ have their cell bodies in the brain stem or the ventral (front) portion of the spinal cord
130
What do all somatic sensory neurons do?
They all have:
◦ A long dendrite, extending from a sensory receptor towards the Soma, which is located just outside the CNS in a dorsal root ganglion
◦ An axon extends from the somatic sensory neurons soma into the spinal cord
◦ The first synapse is in the CNS – depending on the type of sensory information conveyed, the axon, either synapsis in the cord, or stretches all the way up to the brain stem before it's for synapse
131
What is a dorsal root ganglion?
A bunch of somatic (and autonomic) sensory neuron cell bodies located just dorsal to (to the back of the spinal cord
◦ There is a pair of dorsal root ganglia for every segment of the spinal cord, and the dorsal root ganglia form a chain along the dorsal (back) aspect of the vertebra column
◦ They are protected within the vertebral column, but are outside the meninges and thus outside the CNS
132
What are the mininges?
Protective sheath of the brain and spinal cord
133
The efferents of the parasympathetic and sympathetic systems consist of two neurons
◦ The pre-ganglionic neuron
◦ The postganglionic neuron
134
Differentiate between the preganglionic neuron and the postganglionic neuron
◦ The pre-ganglionic neuron: has a cell body in the brain, stem or spinal cord. It sends an axon to an autonomic ganglion, located outside the spinal cord. In the ganglion, is axon synapsis with a postganglionic neuron.
◦ A postganglionic neuron: sends an axon to an effector (muscle or gland).
135
What do all parasympathetic postganglionic neurons release?
Acetylcholine
136
What do all autonomic preganglionic neurons release?
Acetylcholine as their neurotransmitter
137
Where do all sympathetic preganglionic efferent neurons have their cell bodies?
in the thoracic (chest) or lumbar (lower back) regions of the spinal cord
138
What do nearly all sympathetic postganglionic neurons release?
Norepinephrine (NE), also known as, noradrenaline, as their neurotransmitter
139
What is the sympathetic system also referred to as?
Thoracolumbar system
140
What is a parasympathetic system known as and why?
The craniosacral system
◦ Because all of its preganglionic neurons have cell bodies in the brainstem (which is in the head or cranium), or in the lower portion of the spinal cord, the sacral portion
141
In the sympathetic system, what is the length of the preganglionic axon and the number of ganglia?
◦ The preganglionic axon is relatively short
◦ There are only few ganglia which are quite large
142
What does a sympathetic postganglionic excel send to the effector?
A long axon
143
What does the parasympathetic preganglionic neuron send to the effector?
Send a long axon to small ganglion, which is close to the effect
144
What is the one exception for which the autonomic afferent (sensory) neurons are similar to the somatic afferent neurons?
The autonomic afferent neurons can synapse in the PNS (at the autonomic ganglia) with automatic efferent neurons in what is known as a "short reflex"
145
How does the general function of the sympathetic parasympathetic systems differ?
◦ The sympathetic system: fight or flight, mobilize energy
◦ The parasympathetic system: rest and digest, store energy
146
How does the location of preganglionic soma differ between the sympathetic and the parasympathetic systems?
◦ For the sympathetic system: thoracolumbar = thoracic and lumbar spinal cord
◦ For the parasympathetic system:
craniosacral = green stem ("cranial") and sacral spinal cord
147
How do the preganglionic axon (neurotransmitter equals acetylcholine (ACh)) between the sympathetic and the parasympathetic systems?
◦ For the sympathetic system: the preganglionic axon is short
◦ For the parasympathetic system: the preganglionic axon is long
148
How do the ganglia differ between the sympathetic and the parasympathetic systems?
◦ For the sympathetic system: the ganglia are close to the cord, far from the target
◦ For the parasympathetic system: the ganglia are far from the cord, close to the target
149
How do the postganglionic axon (usual neurotransmitter) differ between the sympathetic and the parasympathetic systems?
◦ For the sympathetic system: the postganglionic axon is long and is norepinephrine [NE]
◦ For the parasympathetic system: the postganglionic axon is short and is acetylcholine (ACh)
150
How was the adrenal gland named?
For its location
◦ "Ad-" connotes "above"
◦ "renal" refers to the kidney
151
How many adrenal glands are there there and where are they located?
◦ There are two adrenal glands, one above each kidney
151
Describe the adrenal glands
◦ The adrenal has an inner portion known as the medulla and an outer portion known as the cortex
152
What is the cortex?
The outer portion of the adrenal gland
◦ it is an important endocrine gland, secreting glucocorticoids (the main one being cortisol), mineralocorticoids (the main one being aldosterone) and some sex hormones
153
What is the main glucocorticoid?
Cortisol
154
What is the main mineralocorticoid?
Aldosterone
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What is the adrenal medulla part of?
The sympathetic nervous system
156
What happens to the adrenal gland upon activation of the sympathetic system?
Is stimulated to release epinephrine, also known as adrenaline
157
What is epinephrine?
A slightly modified version of norepinephrine, the neurotransmitter released by the sympathetic postganglionic neuron
◦ it is a hormone because it is released into the bloodstream by a ductless gland, but behaves like a neurotransmitter in many ways
◦ elicits it's effects very rapidly, and the effects are quite short lived
◦ epinephrine released from the adrenal medulla is what causes the sudden flushing and sweating one experiences when severely startled
158
What are the two major control systems of the body?
◦ The nervous system
◦ the endocrine system
159
Differentiate between the nervous system system and the endocrine system
◦ The nervous system is acting with relatively short term effects
◦ the endocrine system takes longer to communicate signals, but generally has longer lasting effects
160
How are the control systems of the nervous system and the endocrine system interconnected?
Because neurons can signal the release of hormones from the endocrine glands
161
What is the primary connection between the nervous system and the endocrine system?
The hypothalamic–pituitary axis
162
What does the nervous system regulate?
Cellular function from instant to instant
163
What does the endocrine system regulate?
Physiology, (especially metabolism) over a period of hours days
164
How does the nervous system communicate?
Via extremely rapid action potential
165
What is the signal of the endocrine system?
The hormone
166
What is a hormone?
A molecule which is secreted into the bloodstream by an endocrine gland, which has its affects upon distant target cells possessing the appropriate receptor
167
What is an endocrine gland?
Ductless gland, whose secretary products are picked up by capillaries supplying blood to the region
168
What is are exocrine glands?
They secrete their products into the external environment, by way of ducks, which empty into the gastrointestinal lumen or the external world
169
What is a hormone receptor?
A polypeptide that possesses a ligand-specific binding sight
170
What happens when a ligand (hormone) binds to a site?
Causes the receptor to modify target cell activity
171
What determines the tissue-specificity of hormone action?
By whether the cells of a tissue have the appropriate receptor
172
What is an autocrine signalling molecule?
A signalling molecule that modifies the activity of the cell which secreted them
173
What are the two group groups that hormones can be grouped into?
◦ Hydrophilic hormones
◦ hydrophobic hormones
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What are hydrophilic hormones?
Hormones, such as peptide and amino acid derivatives, must bind to the receptor on the cell surface
175
What are hydrophobic hormones?
Hormones such as steroid hormones that bind to receptors in the cellular interior
176
Where are peptide hormones synthesized?
In the rough ER and modified in the Golgi
177
Where are peptide hormones stored?
In vesicles until needed, when they were released by exocytosis
178
How are peptide hormones released?
By exocytosis
179
What happens to peptide hormones in the bloodstream?
They dissolve in the plasma, since they are hydrophilic
◦ their Hydro Felicity also means they cannot cross biological membranes, and thus are required to communicate with the interior of their target self by way, way the second messenger cascade
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What is the action mechanism of a peptide hormone?
Because it's hydrophilic and dissolves in the bloodstream, it has to utilize a second cascade
◦ the peptide hormone is a first messenger, which must bind to a cell surface receptor
◦ the receptor is a polypeptide with a domain on the inner surface of the plasma membrane that contains the ability to catalytically activate a second messenger
◦ the end result of second messenger activation is that the function of proteins in the cytoplasm is changed
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What is a key feature of second messenger cascades
Signal application, which allows a few activated receptors to change the activity of many enzymes in the cytoplasm
182
How quickly do peptide hormones take effect and how long do their effect last?
◦ Because peptide hormones, modify the activity of existing enzymes in the cytoplasm, their effects are exerted rapidly, minutes to hours from the time of secretion
◦ The duration of their effects is brief
183
What are the two subgroups within the peptide hormone category?
◦ Polypeptides
◦ Amino acid derivatives
184
What is an example of a polypeptide hormone?
Insulin
185
Describe insulin
◦ It is a polypeptide hormone
◦ it has a complex tertiary structure involving disulphide bridges
◦ it is secreted by the beta cells of the pancreatic islets of Langerhans in response to elevated blood glucose and binds to a cell surface receptor with a cytoplasmic domain possessing protein kinase activity.
186
What are amino acid derivatives?
◦ A type of peptide hormone
◦ are derived from single amino acids, and contain no peptide bonds
◦ an example is catecholamines (which include epinephrine), and the thyroid hormones, which are both derived from tyrosine
187
What do catecholamines act like?
Peptide hormones
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What do thyroid hormones act like?
Steroid hormones
189
How is epinephrin secreted and act?
It is a small cyclic molecule secreted by the adrenal medulla upon activation of the sympathetic nervous system
◦ It binds to cell surface receptors to trigger a cascade of events that produce is the second messenger cyclic adenine monophosphate (cAMP) and activates protein kinases in the cytoplasm
190
How do thyroid hormones work?
They incorporate iodine into their structure
◦ they enter cells, bind to DNA, and activate transcription of genes involved in early mobilization
191
What are steroids?
Hydrophobic molecules synthesized from cholesterol in a smooth endoplasmic reticulum
◦ due to their hydrophobicity, steroids freely diffuse through biological membranes
◦ they are not stored, but rather diffuse into the bloodstream as soon as they are made
◦ if a steroid hormone is not needed, it will not be made
◦ their hydrophobicity also means they cannot be dissolved in the plasma, and instead will journey through the bloodstream, stuck to proteins in the plasma, such as albumin
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How do steroid hormones work?
The small hydrophobic, steroid hormone exerts its affects upon target cells by diffusing through the plasma membrane bind with a receptor in the cytoplasm
◦ once it has bound it ligand, and, the steroid hormone-receptor complex is transported into the nucleus, where it acts as a sequence specific regulator of transcription
◦ because steroid hormones must modify transcription to change the amount and/or type of proteins in the cell, their Effexor exerted slowly, over periods of days, and persist for days two weeks
193
How long do the effects of steroid hormones last and why?
Because steroid hormones must modify transcription to change the amount and/or type of proteins in the cell, their effects are exerted slowly, over a period of days, and persist for days to weeks
194
Where are steroids regulating sexuality, reproduction and development, secreted?
They are secreted by the testes, ovaries, and placenta
195
Where are the steroids regulating water balance, and other processes secreted?
They are secreted by the adrenal cortex
196
What do the other endocrine glands (excluding the testes, ovaries, placenta, and the adrenal cortex) secrete?
Peptide hormones
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How does the structure differ between peptides and steroids?
◦ The structure of peptides is: hydrophilic, large (polypeptides) or small (amino acid derivatives)
◦ The structure of steroids is:
hydrophobic, small
198
How does the site of synthesis differ between peptides and steroids?
◦ The site of synthesis of peptides is:
the rough ER
◦ The site of synthesis of steroids is:
the smooth ER
199
How does transport in the blood bloodstream differ between peptides and steroids?
◦Peptides transport in the bloodstream is:
free
◦ Steroids transport in the bloodstream is:
stuck to protein carriers
200
How does the specificity differ between peptides and steroids?
◦ The specificity of peptides is:
only target cells have appropriate surface receptors (exception: thyroxine = cytoplasmic)
◦ The specificity of steroids is:
only target cells have appropriate cytoplasmic receptors
201
How does the mechanism of effort differ between peptides and steroids?
◦ The mechanism of effort for peptides is:
bind to receptors that generate second messengers, which result in modification of enzyme activity
◦ The mechanism of effort for steroids is:
Bind to receptors that alter gene expression by regulating DNA transcription
202
How does the timing of affect differ between peptides and steroids?
◦ The timing of effect for peptides is:
rapid, short-lived
◦ the time of affect for steroids is:
slow, long lasting
203
What are hormones essential for?
◦ Gamete synthesis
◦ ovulation
◦ pregnancy
◦ growth
◦ sexual development
◦ overall metabolic activity
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How are hormones regulated?
Hormone levels rise and fall, as dictated by physiological needs
◦ the amount of hormone secreted is controlled by the changes in the variable the hormone is responsible for controlling – it a feedback regulation
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What is a physiological endpoint?
a place which must be maintained at constant levels
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What is the role of endocrine system generally speaking?
To maintain homeostasis or physiological consistency
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What is a layer of regulation for the endocrine system?
A central control mechanism - is hormones that regulate hormones
◦ such Meta-regulators are known as tropic hormones
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What are tropic hormones?
hormones that have other endocrine glands as their target.
◦ Most tropic hormones are produced and secreted by the anterior pituitary.
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What is the result of hormone secretion?
It inhibits further secretion
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What is negative feedback or feedback inhibition?
When the secretion of something inhibits further secretion
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What portion of the brain controls much of the endocrine system?
the hypothalamus, which is located at the centre of the brain
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How does the hypothalamus control the endocrine system?
By releasing tropic hormones that regulate other tropic hormones, called releasing and inhibiting factors or releasing and inhibiting hormones
◦ The hypothalamus controls, the anterior pituitary and the interior pituitary controls most of the endocrine system
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What happens when there is damage to the connection between the hypothalamus and the anterior pituitary?
It is generally fatal unless daily hormone replacement therapy is given
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What is the hypothermic – pituitary control access
The connection between the hypothalamus and the anterior pituitary, which is a major point of control for the endocrine system
215
How is the hypothalamus exert its control of the pituitary and why is it unique?
By its hormones into the bloodstream, just like any other endocrine gland
◦ It's unique though, because there is a special miniature circulatory system provided for efficient transport of hypothalamic, releasing, and inhibiting factors to the anterior pituitary (called the hypothalamic–pituitary portal system)
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what is another name for the pituitary gland?
Hypophysis
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What happens to blood leaving the heart and its relation to the portal system?
Blood leaving the heart move through only one capillary bed before returning to the heart, since pressure drops substantially in capillaries
◦ a portal system, however, consists of two capillary beds and sequence, allowing for drug communication between nearby structures
◦ The two portal systems are: the hypothalamic–pituitary portal system, and hepatic portal system
218
What are the two portal systems?
◦ The hypothermic–pituitary portal system
◦ The hepatic portal system (in the gastrointestinal track to the liver)
219
Describe the pituitary gland
◦ It has two halves: the front (anterior) and the back (posterior)
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What is the anterior pituitary also called?
The adenohypophysis
221
What is the posterior pituitary also called?
The neurohypophysis
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What is the anterior pituitary and what is it controlled by?
◦ It is a normal endocrine gland
◦ It is controlled by hypothalamic release and inhibiting factors (essentially tropic hormones)
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What is the posterior pituitary composed of?
◦ The posterior pituitary is composed of axons which descend from the hypothalamus.
◦ These hypothalamic neurons that send axons down to the posterior pituitary or an example of neuroendocrine cells
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What are neuroendocrine cells?
Neurons which is hormones into the bloodstream
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What are hormones of the posterior pituitary?
◦ ADH (antidiuretic hormone or vasopressin)
◦ oxytocin
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What is the function of the hormone ADH and where is it produced?
◦ It causes the kidney to retain water during times of thirst
◦ it is produced in the posterior pituitary
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What is the function of oxytocin and where is it produced?
◦ It causes milk let-down for nursing, as well as uterine contractions during labour
◦ it is produced in the posterior pituitary
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What do thyroid hormone and cortisol have in common?
They both have brought effects on metabolism and energy use
229
How is thyroid hormone produced?
From the amino acid tyrosine in the thyroid gland and comes in two forms, with three or four iodine atoms for molecule
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How is the production of thyroid hormone increased?
By the thyroid stimulating hormone (TSH) from the anterior pituitary, which is regulated by the hypothalamus and the central nervous system
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What is the mechanism of action of the thyroid hormone? And what is the effect of this action?
To bind to a receptor in the cytoplasm of cells that then regulates transcription in the nucleus
◦ The effect of this regulation is to increase the overall metabolic rate and body temperature, and, and children, to stimulate growth
232
What can exposure to cold increase?
The production of thyroid hormone
233
How is cortisol secreted?
It is secreted by the adrenal cortex in response to ACTH from the pituitary
234
What do the effects of cortisol tend to help the body deal with?
Stress
◦ it also helps to mobilize glycogen and fat stores to provide energy during stress, and also increases the consumption of proteins for energy
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What happens to someone who has had their adrenal cortex removed, when they experience stress?
They could die
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What are the effects of long-term high levels of cortisol?
◦ Generally negative effects, including the suppression of the immune system
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What are the major endocrine glands?
◦ The pituitary gland
◦ The thyroid gland
◦ The thymus
◦ The adrenal glands
◦ The pancreas
◦ The testes and the ovaries
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What kind of hormone does the hypothalamus release?
◦ It releases, releasing and inhibiting factors (peptides)
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What kind of hormone does the anterior pituitary release?
It releases:
◦ growth hormones (GH) (peptide)
◦ Prolactin (peptide)
◦ Thyroid stimulating hormone (TSH) (peptide)
◦ Adrenocorticotropic hormone (ACTH) (peptide)
◦ luteinizing hormone (LH) (peptide)
◦ Follicle stimulating hormone (FSH) (peptide)
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What are tropic anterior pituitary hormones?
◦ thyroid stimulating hormone (TSH) (peptide)
◦ adrenocorticotropic hormone (ACTH) (peptide)
241
What are gonadotropic anterior pituitary hormones?
◦ luteinizing hormone (LH) (peptide)
◦ follicle stimulating hormone (FSH) (peptide)
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What is the target/effect of growth hormone and where is it released from?
◦ increased bond and muscle growth, increased cell turnover rate
◦ released from the anterior pituitary
243
◦ What is the target of/effect of prolactin?
◦ What is its effect?
◦ Where is it released from?
◦ It targets the mammary glands
◦ Its effects are milk production
◦ It is released from the anterior pituitary
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◦ What is the target of thyroid stimulating hormone?
◦ What is its effect?
◦ Where is it released from?
◦ It targets the thyroid
◦ It effects, an increased in synthesis and released of TH
◦ It is released from the tropic anterior pituitary
245
◦ What is the target of the releasing and inhibiting factors from the hypothalamus?
◦ What are their effects?
◦ They target the anterior pituitary
◦ Their efect is modifying activity
246
◦ What is the targets and effects of adrenocorticotropic hormone?
◦ Where is it released from?
◦ It's targets and effects are: increased growth and secretory activity of adrenal ctx
◦ It is released from the tropic anterior pituitary
247
◦ What is the target of luteinizing hormone?
◦ What is the effect of it?
◦ Where is it released from?
◦ It targets the ovaries or testes
◦ It effects, ovulation and testosterone synthesis
◦ It is released from the gonadotropic anterior pituitary
248
◦ What is the target of follicle stimulating hormone?
◦ What is its effect?
◦ Where is it released from?
◦ It targets the ovary or testes
◦ It effects follicle development and spermatogenesis
◦ It is released the gonadotropic anterior pituitary
249
What hormones does the posterior pituitary release?
◦ antidiuretic hormone (ADH, vasopressin) (peptide)
◦ oxytocin (peptide)
250
◦ What is the target of antidiuretic hormone?
◦ What is its effect?
◦ Where is it released from?
◦ It targets the kidneys
◦ It effects water retention
◦ It is released from the posterior pituitary
251
◦ What is the target of oxytocin?
◦ What are its effects?
◦ Where is it released from?
◦ It targets the brests and uterus
◦ Its effects are milk letdown and contractions (in the uterus)
◦ It is released from the posterior pituitary
252
What hormones are released from the thyroid?
◦ thyriod hormone (TH, thyroxine) (modified amino acid)
◦ calcitonin (peptide)
253
What hormones are released from the thyroid C cells?
calcitonin (peptide)
254
◦ What are the targets and effects of thyroid hormone in children?
◦ Where is it released from?
◦ In children, its targets and effects are, that it is necessary for physical and mental development
◦ It is released from the thyroid
255
◦ What are the targets and effects of thyroid hormone in adults?
◦ Where is it released from?
◦ In adults, its targets and effects are increased metabolic rate and temperature
◦ It is released from the thyroid
256
◦ What are the targets of calcitonin?
◦ What are its effects?
◦ Where is it released from?
◦ It targets bone and kidney
◦ Its effects are that it lowers serum [Ca2+]
◦ It is released from thyroid C cells
257
What hormones are released from the parathyroids?
Parathyroid hormone (PTH) (peptide)
258
◦ What are the targets of parathyroid hormone?
◦ What are its effects?
◦ Where is it released from?
◦ It targets, bone, kidney, and small intestine
◦ Its effects are that it raises serum [Ca2+]
◦ It is released from the parathyroids
259
What hormones are released from the thymus?
thymosin (children only) (peptide)
260
◦ What are the effects of thymosin?
◦ Where is it released from?
◦ It is involved in T cell development during childhood
◦ It is released from the thymus
261
What hormones are released from the adrenal medulla?
epinephrine (modified amino acid)
262
◦ What are the effects of epinephrine?
◦ Where is it released from?
◦ It is involved in sympathetic stress response (rapid)
◦ It is released from the adrenal medulla
263
What hormones are released from the adrenal cortex?
◦ cortisol ("glucocorticoid") (steroid)
◦ aldosterone ("mineralocorticoid") (steroid)
◦ sex steroids
264
◦ What is the effects of cortisol?
◦ Where is it released from?
Its effects are;
◦ longer-term stress response
◦ increased blood [glucose]
◦ increased protein catabolism
◦ decreased inflammation and immunity, etc.
◦ It is released from the adrenal cortex
265
◦ What is the target of aldosterone?
◦ What are its effects?
◦ Where is it released from?
◦ It targets the kidneys
◦ Its effects are, increased Na+ reabsorpotion to increase blood pressure
◦ It is released from the adrenal cortex
266
◦ What are the effects of sex steroids?
◦ Where is it released from?
◦ An adrenal tumor can overproduce sex steroids, causing masculinization or feminization
◦ It is released from the adrenal cortex
267
What hormones are released from the endocrine pancrease?
◦ insulin (beta cells secrete) (peptide) - absent or ineffective in diabetes mellitus
◦ glucagon (alpha cells secrete) (peptide)
◦ somatostatin (SS-gamma cells secrete) (peptide)
268
◦ What is the target of insulin?
◦ What are its effects?
◦ Where is it released from?
◦ It targets, decreased blood [glucose]
◦ It effects, increased glycogen and fat storage
◦ It is released from the endocrine pancrease (islets of Langerhans)
269
◦ What is the target of glucagon?
◦ What are its effects?
◦ Where is it released from?
◦ It targets, increased blood [glucose]
◦ It effects, decreased glycogen and fat storage
◦ It is released from the endocrine pancreas (islets of Langerhans)
270
◦ What are the effects of somatostatin?
◦ Where is it released from?
◦ It inhibits many digestive processes
◦ It is released from the endocrine pancreas (islets of Langerhans)
271
What hormones are released from the testes?
testosterone (steroid)
272
◦ What are the effects of testosterone?
◦ Where is it released from?
◦ Its effects are male characteristics and spermatogenesis
◦ It is released from testes
273
What hormones are released from the ovaries/placenta?
◦ estrogen (steroid)
◦ progesterone (steroid)
274
◦ What are effects of estrogen?
◦ Where is it released from?
◦ Its effects are female characteristics and endometrial growth
◦ It is released from the ovaries/placenta
275
◦ What are the effects of progesterone?
◦ Where is it released from?
◦ Its effects are, endometrial secretion and pregnancy
◦ It is released from the ovaries/placenta
276
What hormones are released from the heart?
atrial natriuretic factor (ANF) (peptide)
277
◦ What is the target of atrial natriuretic factor?
◦ Where are its effects?
◦ Where is it released from?
◦ It targets the kidney
◦ It increases urination to decrease blood pressure
◦ It is released from the heart
278
What hormones are released from the kidney?
erythropoietin (peptide)
279
◦ What is the target of erythropoietin?
◦ What is its effects?
◦ Where is it released from?
◦ It targets the bone marrow
◦ It effects increased RBC synthesis
◦ It is released from the kidney
