Exam #1 Flashcards
(482 cards)
1
Q
what is physiology?
A
The study of normal functioning of a living organism and its component parts
- structure and function relationships
- includes chemical and physical interactions
- emergent properties (properties of a system that are a result of non-linear interaction between component parts
2
Q
what are the 4 things that characterize “living” things?
A
1) It is made up of one or more cells
2) Regulates its internal environment
3) Responds to stimuli (sensory systems to detect it)
4) Capable of reproduction (self replication)
- this excludes viruses as living things
3
Q
what are the 10 levels of organization of life
A
1) Biosphere
2) Ecosystem
3) Population
4) Organism
5) Organ system
6) Organ
7) Tissue
8) Cell
9) Molecule
10) atoms
4
Q
why is physiology important?
A
1) Leads to treatment of diseases in humans and other organisms (pathophysiology)
2) Helps us understand how organisms cope with environmental stressors
3) Foundation of understanding the philosophical question “what is life?”
4) Required credit for certain programs
5
Q
what are 5 themes in physiology?
A
1) Structure and function and how they’re closely related
2) Homeostasis and control systems
3) Information flow coordinates body function
4) Need for energy
5) evolution
6
Q
homeostasis
A
The ability to maintain a relatively constant internal environment even when the external environment is variable
7
Q
Give examples of what parameters of an animal must be regulated to within certain levels in order to support life
A
- temperature
- pH
- salinity
- oxygen, carbon dioxyde
- nutrients
8
Q
what is the role of a control system in regards to homeostasis?
A
A control system monitors and adjusts regulated variables (internal temp, pH, etc.)
9
Q
biomolecule
A
Organic molecule that is commonly associated with life
-carbohydrates, lipids, nucleic acids, protein
10
Q
what is the general formula of a carbohydrate?
A
C(n) H(2n) O(n)
11
Q
what are 3 properties of carbohydrates?
A
- most are hydrophilic (lipophobic)
- very abundant in nature (most common molecule)
- used for structure and energy
- almost all eukaryotic cells can use glucose for energy and can store some form of glucose (monomer or polymer) for energy
- Plants and arthropods use carbohydrates as structural molecule
- many proteins and lipids are modified by the addition of carbohydrates
12
Q
Simple sugars
-most common ones are building blocks of complex carbohydrates and have either 5 or 6 carbons (ribose and glucose)
A
monosaccharides
13
Q
Consists of glucose and another monosaccharide
Examples: sucrose, maltose, and lactose
A
disaccharide
14
Q
True or False?
Nucleotides are involved in energy metabolism and signaling
A
true
15
Q
nucleotide
A
Consists of one or more phosphate group, a 5 carbon sugar, and a nitrogenous base
16
Q
another word for nitrogenous base
A
“r” group
17
Q
The structure of the nitrogenous base determines whether the nucleotide is ________?
A
- adenosine
- cytosine
- guanosine
- thymidine
18
Q
adenosine triphosphate (ATP)
A
Basics molecule of energy storage in most organisms, including mammals
19
Q
guanosine triphosphate (GTP)
A
Energy source in many physiological chemical reactions
20
Q
Are lipids generally hydrophobic or hydrophilic?
A
hydrophobic (or have parts that are hydrophobic)
21
Q
what are the 5 groups of lipids?
A
1) Fatty acids
2) Glycerides
3) Phospholipids and sphingolipids
4) Steroids
5) Eicosanoids
22
Q
lipids are general comprised of what?
A
-contain mostly carbon and hydrogen, a few oxygen atoms, nitrogen, and phosphorus
23
Q
what are the 3 roles of lipids?
A
1) Structure of cells
- waterproof: keep insides in and outsides out
- pliable
2) Energy source
3) Communication (within and between cells)
24
Q
a fatty acid is comprised of what?
A
Long unbranched hydrocarbon chain with 8-28 carbons
-has carboxyl (=acidic) functional group
25
Saturated fats have _____ and unsaturated fats have ______
no double bonds, double bonds
26
The more double bonds an unsaturated fat has, the _____ likely it will be solid at room temperature
less
27
glycerides are a derivitive of _____
fatty acids
28
What is the most common fat molecule in your body?
triglycerides
29
What is the difference between monoglycerides, diglycerides, and triglycerides?
the number of fatty acid tails
30
Phospholipids are a derivative of _____
glycerides
31
What is the major component of cell membranes?
phospholipids
32
what are phospholipids comprised of?
A diglyceride, a phosphate group, and a variable "R" group
33
phospholipids are amphipathic molecules, what does this mean?
having both hydrophilic and hydrophobic parts
- they have polar heads and non-polar tails
- the "R" group is a variable polar group
34
Phospholipid bilayer:
Micelles are:
Liposomes have:
1) Forms a sheet
2) Droplets of phospholipids
3) An aqueous center
35
What is the difference between phospholipids and glycolipids?
glycolipids are decorated with a carbohydrate (glycophospholipid)
36
what are steroids?
- basic structure consists of 3 6-carbon rings plus one 5-carbon ring (17 carbons)
- different functional groups ("R" groups)
- play roles in communication and cell structure
37
eicosanoids
- main chain consists of 20 carbon atoms
- many are derived from the fatty acid arachadonic acid
- main function is communication within cells and between cells (inflammation, pain, platelet aggregation)
- primarily lipophilic (hydrophobic) but small [] can dissolve in
38
what are proteins?
- macromolecules
| - linear chains of amino acids
39
How many amino acids are encoded by the universal genetic code?
20
40
how many amino acids are essential? how can we obtain these?
-2 additional amino acids can be incorporated other than the 20, 9 are essential, we need to consume them because our body cannot synthesize them
41
A short chain of amino acids is called a _____
peptide
42
Longer chains of amino acids are called_____
proteins
43
Proteins have complex structures that are determined by _____
the sequence of amino acids that make them up, this sequence which is encoded in the genome
44
what is the primary structure of amino acids?
the sequence of amino acids
45
what is the secondary structure of amino acids?
Has to do with the interaction of amino acids
46
what is the tertiary structure of amino acids?
has to do with the way they react with eachother
47
what is the quaternary structure of amino acids?
interaction of multiple sub-units
48
proteins are the tools of the cell, explain what this means
- proteins are versatile, and carry out many different jobs
| - in every mammalian cell, there are 10,000-15,000 different proteins expressed
49
explain the differences between fibrous and globular proteins
```
Fibrous
-insoluble
-generally used for structure
Globular
-usually soluble
-7 different
```
50
name the 7 different kinds of soluble proteins
1) Enzymes
2) Membrane transporters
3) Signal molecules
4) Receptors
5) Binding proteins
6) Regulatory proteins
7) immunoglobulins
51
In order to do something a protein must interact or bind with _____
other proteins, molecules, or ions
52
A molecule that binds to a protein binding site is called a_____
ligand
53
An ______ ligand is something natural in your body: ex: hormone or neurotransmitter
A _______ may be a drug or a toxin
endogenous, non-endogenous
54
A protein binds a ligand with affinity, what does this mean?
high affinity means it will bind tightly, weak affinity means it will bind weakly
55
what is an agonist?
A ligand that binds to a protein binding site and alters the state of the protein, resulting in a biological response
-a hormone or neurotransmitter or a drug for example
56
what is an antagonist?
A ligand that reduces the action of an agonist (binds but causes no biological response)
57
what are the 2 different types of antagonists? what is the difference between the 2?
1) Competitive: act to block the agonist at its binding site
2) Allosteric: act to block the agonist by binding to the protein away from the binding site and inactivate the binding site
58
How do we measure the rate of a protein?
Protein activity has a measurable rate
- often depends on amount of protein and [ ] of ligand
- has a maximum rate (saturation)
59
The more protein present the ____ the rate of activity (when the ligand remains constant)
faster
60
If the amount of _____ is held constant, the reaction rate depends on the amount of ligand, up to the ______
-like an elevator, only room for so many people until max capacity is reached
binding protein, saturation point
61
what are 4 factors that can alter protein binding?
1) Isoforms (closely related proteins)
2) Activation (sometimes proteins need to be activated/altered somehow)
3) Physical factors (pH, temperature; these can cause structural changes, protein may become denatured)
4) Modulation
- covalent modification (phosphorylation, dephosphorylation, addition of lipid or carbohydrate)
- agonists, antagonists
62
what make up amino acids?
All amino acids have a carboxyl group (COOH), an amino group (NH2), and a hydrogen attached to the same carbon
-the 4th bond of the carbon attaches to a variable "R" group
63
what are the 4 functions of a cell membrane?
1) Physical barrier (separates ICF from ECF)
2) Gateway for exchange (movement of solutes, semipermeable)
3) Communication (home to receptors that detect physical and chemical stimuli and starts cascade of response to stimuli)
4) Cell structure (membrane proteins hold cytoskeleton proteins to give cell structure, may also form specialized junctions)
64
what is the cell membrane comprised of?
- made of mostly proteins and lipids
- ratio of protein to lipid is different for different cell types
- more active cells tend to have more proteins
65
what is the fluid mosaic model of the membrane structure?
- proteins area float on a sea of lipid
| - some proteins are anchored, some of them are free to diffuse around or "float" around on the sea of phospholipids
66
what kinds of lipids make up the structure of a cell membrane? what kinds of proteins?
Lipids: glycolipids, phospholipids, cholesterol, sphingolipids
Proteins: integral, peripheral, cytoskeletal, extracellular matrix
67
cell membranes: phospholipids
- mostly comprised of phospholipids
- several different varieties of these (R-group saturation)
- polar head groups towards aqueous side, non polar fatty acid tails inside
68
what alters a cell membranes fluidity?
cholesterol
69
cell membranes: cholesterol
- flat molecule, slips between fatty acids
- regulates membrane fluidity
- slows diffusion of molecules across membrane
70
cell membranes: sphingolipids
- have longer tails than phospholipids
- tend to aggregate together = lipid rafts
- rafts also have a high density of cholesterol
- some proteins associate ONLY with lipid rafts, leading to areas of specialization on cell membranes
- ex: some G-protein coupled receptors
- errors in lipid rafts composition is thought to play a role in development of some diseases such as Alzheimer's
71
cell membranes: proteins
- integral (has been modified)
- polytypic = transmembrane
- monotypic = permanently associated from one side
- peripheral (easy to separate)
72
cell membrane: integral proteins (transmembrane)
- permanently attached to the cell membrane
- integral polytypic = transmembrane proteins
- span the lipid bilayer once or several times
- approximately 20-25 hydrophobic amino acids to span the membrane
73
cell membrane: integral proteins (monotypic)
-permanently attached to the cell membrane
-monotypic proteins = permanently attached to membrane from one side
A) lipid anchored proteins
-modified by the addition of a fatty acid
-often associate with lipid rafts
B) may have strongly hydrophobic sections that allow it to associate with lipid portion of bilayer
74
_____ associate non-covalently with integral proteins, or polar heads of phospholipids
peripheral proteins
75
cell membranes: proteins
cytoskeleton
- not a membrane protein, but often interacts with membrane proteins
- flexible 3-d skeleton of fibrous proteins throughout the cytoplasm (contribute to cell shape)
76
cell membrane proteins
extracellular matrix
- membrane proteins and secreted protein found on the extracellular side of cell membranes
- forms a husk around cells
- highly variable glycosylation (modified by the addition of carbohydrates)
- contribute to cell strength (defines how far a cell can be stretched - ex: muscle cell)
77
muscular dystrophy
| look at required reading for more detail
- dystrophin provides a link between cytoskeleton and extracellular matrix
- in MD, this protein is missing (or non-functional)
- results in easily damaged muscles, in severe forms, repeated damage causes muscles to eventually waste away
78
diffusion
- the process of moving solute molecules away from an area of high concentration towards area of low concentration
- "down the concentration gradient"
- passive
- no external energy is needed, just kinetic energy of the molecules
- this process continues until equilibrium is reached
79
what things can affect the speed of diffusion?
Diffusion is fast over short distances and slow over long distances
- the time taken to get from A to B is a "distance squared" relationship: if distance doubles from 1 to 2, time increases from 1 to 4 (=2 to the power of 2)
- rate of diffusion is faster at high temp
- rate of diffusion is faster for small molecules
- rate of diffusion is slower across a membrane
80
simple diffusion
-no membrane, diffusion is fast
81
semipermeable membrane
-allows selected solutes to pass, but more slowly
82
Why does the type of molecule influence the diffusion across the cell membrane?
1) Could be because of the size
| 2) Could be polar or non-polar
83
Give examples of hydrophobic, non polar molecules that diffuse across a cell membrane
- O2, CO2
- lipids
- steroids
- fat soluble molecules
- these diffuse freely, almost unimpeded
84
can small uncharged molecules diffuse across the cell membrane?
- urea
- H20??
- there are channels in the cell membrane that allow water to move across, but can also diffuse freely
85
can large uncharged molecules diffuse across the cell membrane?
- glucose, proteins, amino acids
| - very big molecules and are not charged, do not diffuse across, interact with the aqueous environment
86
can charged molecules diffuse across the cell membrane?
- ions
| - cannot diffuse across, need transport proteins
87
what 5 things affect the diffusion of a molecule across the cell membrane?
1) The type of molecule
a. Size
b. Lipid solubility: polar or non-polar
2) Concentration gradient
3) Temperature
4) Surface area
a. More surface area, faster diffusion
5) Composition of membrane
a. Simple bilayer vs many proteins and extracellular matrix (simple bilayer relatively easy for molecules to diffuse across
b. Types of phospholipids and sphingolipids (if these have a lot of double bonds, all the molecules are more spaced apart
c. Presence of cholesterol (a lot of cholesterol is able to block molecules from diffusing between
88
what is fick's law of diffusion?
Rate of diffusion is proportional to the surface area x concentration gradient x membrane permeability
Membrane permeability is proportional to the lipid solubility divided by the molecular size
89
liposomal drug delivery
- some drugs may have low bioavailability due to poor solubility
- some drugs may be toxic at useful doses, and must be targeted to a specific cell type (may work well for some problems, but could be dangerous to other organs)
- liposomal drug delivery could be useful to fix these problems
90
how does liposomal drug delivery work?
- surface proteins to target liposome to specific location in the body
- surface sugars to prevent destruction by the immune system
- oil-soluble drugs in the lipid bilayer
91
intracellular fluid
-2/3 of the total body water volume. Material moving into and out of the intracellular fluid must cross the cell membrane
92
extracellular fluid
Includes all the fluid outside the cells. The ECF is 1/3 of the body fluid volume
- consists of:
- intersitital fluid, which lies between the circulatory system and the cells, is 75% of the ECF volume
- plasma, the liquid matric of blood, is 25% of the ECF volume
93
homeostasis is synonymous to equilibrium
True or False?
false
- there is chemical disequilibrium in homeostasis
- electrical disequilibrium
- there is osmotic equilibrium (no net movement of water)
94
osmosis
- the diffusion of water
- water can have a [] gradient
- water will diffuse down its [] gradient
95
_____ water has the highest concentration of water and ______ lower the concentration of water
pure, solutes
96
If you have 2 compartments that are separated by a membrane that is permeable to water but not to glucose, what will happen to the water?
Water moves by osmosis into the more concentrated solution
97
Pressure that is applied to oppose osmosis is called _____
osmotic pressure
98
What are the normal physiological concentrations of salts in the extracellular fluid?
```
K+ = 5 mM
Na+ = 145 mM
Cl- = 108 mM
Ca++ = 1mM
```
99
what are the normal physiological concentrations of salts in the intracellular fluid?
```
K+ = 150mM
Na+ = 15mM
Cl- = 5mM
Ca++ = 0.0001mM
```
100
What is the sum of the normal physiological concentrations of salt in the extra and intracellular fluid?
Around 290 mOsM (milliosmoles)
101
isosmotic
having the same osmotic pressure
102
hyperosmotic
when extracellular fluid osmolarity is greater than that of the intracellular fluid
103
hyposmotic
solution with a lesser concentration of solute
104
why is osmolarity important?
Changing osmolarity of the extracellular solution cause redistribution of water and some solutes in cells
-this causes cells to shrink or swell
105
The ability of a solution to shrink or swell its cells is its ______
tonicity
106
If a solution is hypertonic, cells _____
shrink
107
In a ______ solution, the solution has more solute, water moves down its concentration gradient and cells lose their water
hypertonic
108
In a ______ solution, extracellular solution has a lower concentration of solute and the water moves down its concentration gradient into the cell
hypotonic
109
what is the difference between osmolarity and tonicity?
Osmolarity:
- osmolarity describes only the number of solute molecules in a cell
- osmolarity can compare any 2 solutions
- does not tell if a cell swells or shrinks
Tonicity:
- tonicity is a comparative term that describes whether a cell changes volume
- tonicity compares a solution to a cell's intracellular solution
- specifically tells you if a cell swells or shrinks
110
_____ depends on the concentration of penetrating and non-penetrating solutes
tonicity
111
what is a penetrating solute?
- small polar, and non-polar molecules
- ex: urea, glycerol, ethanol
- these can move freely across a membrane
112
what is a non-penetrating solute
- ions and larger polar molecules
- ex: Na+. Glucose, amino acids
- these cannot move freely across a membrane
113
if the solute is ______, water will move inside the cell, if the solute is ______, the molecules will move from the higher to lower concentration gradient to reach a balance instead of the water
non-penetrating, penetrating
114
Hyposmotic solutions are always hypotonic
True or false?
true
115
intracellular solute are penetrating
True or False?
false
116
water will flow into the compartment with the highest concentration of ______ solutes
non-penetrating
117
channel protein
A channel protein is a water filled pore that can open to both sides of the membrane
Ex: water channels, ion channels
-some of these channels are open all the time (open channels) and some are gated channels that open and close with different stimuli (gated channels)
118
what do channel proteins look like?
The protein will fold and assemble around a central water-filled pore
-they are polytypic (having several variant forms)
119
what are the 3 types of carrier proteins?
Carrier proteins never form an open channel between the two sides of the membrane
- uniport carriers: only moving material in one direction
- symport carriers: allow more than one type of molecule to cross in one direction
- antiport carriers: allow more than one type of molecule to go both ways
120
how do carrier proteins work?
- the passage is open on one side (extracellular fluid) and the molecule to be transported enters the protein
- there is a conformational change when the molecule binds to the binding site and the protein closes both sides (transition state)
- there is another conformational change and the passage opens to the other side (inside) of the protein
121
In terms of energy requirements for carrier proteins, there are 3 categories. These categories are:
1) Facilitated diffusion
2) Primary active transport
3) Secondary active transport
122
facilitated diffusion
Defined as moving a molecule across a membrane via carrier protein
- does not require ATP
- also sometimes called passive transport
- cannot accumulate solute against a concentration gradient (chemical equilibrium inside and outside the cell)
- ex: glucose transporter (= GLUT proteins)
123
describe the facilitated diffusion of glucose, what happens to glucose once it enters the cell?
- glucose binds to the transporter
- moves from outside to inside of cell
- sometimes glucose is phosphorylated inside the cell
- it is no longer glucose inside the cell
- glucose can keep moving in by passive transport
- by phosphorylating them, the cell can take more glucose without upping the []
124
why does a cell phosphorylate glucose
- keeps the [] of glucose low inside the cell
| - if the cell actively accumulates glucose, you have lots of molecules inside the cell which ups the osmolarity
125
primary active transport
- uses ATP
- establishes gradients
- sometimes called pumps
- Na+, K+, ATPase is the most widely known example, but there are others
- Ca++ ATPase
- H+ ATPase
- H+/K+ ATPase
126
Na+/K+ ATPase
- primary active transport
- pumps 2 K+ ion into the cell, removes 3 Na+ ions
- hydrolyses ATP
- several conformational changes occur
127
The gradient in the normal physiological concentrations of salts is established by the ______.
-the difference in K+ and Na+ is crucial for many things: ex: it allows the nervous system to generate electrical signals
Na+/K+ ATPase
128
At rest, the human body produces about ____ watts, the Na+/K+ ATPase in the CNS accounts for ____ watts of that
100, 20
129
secondary active transport
- active transport
- does not directly utilize ATP as a source of energy
- uses the concentration gradient of one molecule/ion to move another against its gradient
- Na+ -glucose secondary active transporter is a good example
130
in secondary active transport, what represents the source of energy?
concentration gradient
131
secondary active transport
1) Na+ binds to carrier protein
a. The intracellular [Na+] is low, [glucose] is high, opposite in extracellular fluid
2) Na+ binding creates a site for glucose
3) Glucose binging changes the carrier conformation
a. Glucose follows Na+ against its [ ] gradient
4) Na+ released into cytosol, glucose follows
132
Epithelial transport utilizes
- facilitated diffusion
- primary active transport
- secondary active transport
True or False?
true
133
describe epithelial transport
1) Na+ K+ ATPase establishes and maintains a Na+ gradient, primary active transport
2) Using the Na+ gradient, glucose is transported into the cell via the Na+ glucose co-transporter, secondary active transport
3) Glucose is transported across the basal membrane by the GLUT transporter, facilitated diffusion
134
chapter 3 and 4 reading
- pages 166-191
| - pages 13-17
135
what is the importance of cellular signalling?
- economic
- humira = made 16 billion
- advair asthma inhaler = made 4.3 billion
- viagra (1.7 billion) and other ED = 5.1 billion
- cymbalta (1 billion) and SSRIs = 4 billion
- Beta blockers (bloodpressure) = 3 billion
- human
- quality of life
136
what are the 3 mechanisms for cell-to-cell signalling (local communication)
1) Gap-junction dependent communication
2) Contact dependent signals
3) Paracrine and autocrine
137
gap junction
1) Channels that connect adjacent cells
a. 2 adjacent cells express channel proteins called connexins
2) Water filled pore: allows small molecules and ions to diffuse from one cell to the next
3) Common in heart, smooth muscle and some neurons
4) Cells are connected by cytoplasmic bridges
138
___ connexons form a functional gap junction between 2 adjacent cells
-each connexon is made of ___ connexin monomers, this equals to ___ connexin proteins to form one gap junction
2, 6, 12
139
When cells are connected by gap junctions, they sit together about ___ - ___ nm apart
2, 4
140
contact dependent signalling
- a molecule (ligand) in the extracellular matrix of one cell binds to a receptor in the membrane of an adjacent cell
- immune system, development
- developing cells need to know who their neighbours are
141
local communication
- a signaling molecule is released
- paracrine: signaling to cells in the immediate vicinity
- autocrine: signaling to self
142
long distance communication: endocrine system
- endocrine system:
- secretes hormones:
- chemicals secreted into the blood that affect cells in other parts of the organism
- contacts almost every cell in the body, but only cells with the proper receptors will be affected
- endocrine refers to substance secreted in to blood, such as insulin
- exocrine refers to substances secreted into a duct, such as digestive enzymes from pancreas (into pancreatic duct, then digestive system)
143
long distance communication: neurotransmitters
- an electrical signal travels distance alone a nerve cell
- causes release of a chemical, the chemical travels across a small gap onto target
- this system is more targeted than the endocrine system
144
long distance communication: neurohormones (neuroendocrine)
- an electrical signal travels distance along a nerve cell
| - causes release of a chemical, the chemical is released into the blood, and acts at distant targets
145
______ are chemicals secreted by neurons that diffuse across a small gap to the target cell
______ are chemicals released by neurons into the blood for action at distant targets (ex: into the blood stream, cells with proper receptor will be affected)
neurotransmitters, neurohormones
146
Except for gap junction signaling, cell-to-cell signaling requires what 3 things?
1) Signal (ligand)
2) Receptor
3) Way to transduce the message (intracellular pathways)
147
The information from secreted signals is converted into what?
intracellular signal pathways or signal transduction pathway
148
what does a signal transduction pathway do?
- transforms one form of signal to another
- ex: iTunes library information has to be decoded and transferred to something that will process the sound (Broadcom chip) this is then converted into a Bluetooth signal, transformed into a mechanical audio signal (this conversion of the signal is called signal transduction
149
are signal transduction pathways ubiquitous?
- all cells have some pathways
| - only certain cells have specific pathways
150
why are signal transduction pathways important?
- they amplify signals
| - can start with a few ligand molecule and cause a massive reaction in a large number of cells
151
There are 2 main categories of ligand receptor interaction based on receptor location, what are they?
- intracellular receptors
| - cell membrane receptors
152
intracellular receptor
- ligands are usually lipophilic (hydrophobic)
- steroid hormones for example
- able to diffuse through cell membrane and bind to receptors in the nucleus or cytosol
- often after gene expression (slow but long-lasting)
153
cell membrane receptors
- &membrane bound organelles
- ligands are usually lipophobic (hydrophilic)
- insulin and other peptide hormones for example
- ligand does not diffuse through cell membrane (but there are exceptions)
- bind to membrane receptors, activates them and causes:
- intracellular cascade
- effects of this in general are quicker and shorter lasting
154
What are the 4 types of cell membrane receptors?
1) Receptor channel
2) Receptor-enzyme
3) G protein-coupled receptor (GPCR)
4) Integrin receptor
155
integrin receptor
-binding ligand stimulates changes in cytoskeleton
-cell movement, growth, wound healing
Integrin receptors binds signaling molecules in the matrix of adjacent cells
- changes the shape, and the motility of that cell
- important when cells are migrating, can tell cells to keep moving if they are not at their final target yet in the development stages
156
receptor channels
- multifunctional receptor
- often called
- ligand-gated ion channel
- neurotransmitter gated ion channel
- ionotropic receptors
- the ligand is often a neurotransmitter
- when the ligand binds, the channel opens, allows ions to enter and leave cell (synaptic transmission)
- allow Ca++ into cells (calcium is an important intracellular signal, changes in the [ ] can have important consequences (activation/inactivation of certain proteins)
157
which cell membrane receptor signal pathway is the fastest?
receptor channels
- this mechanism is fast (within milliseconds)
- going to cause a rapid change in that cell
- fastest out of all the pathways
158
receptor enzyme and GCPR
- both going to active an intracellular signaling pathway
- real example of amplification
- only takes a few ligand molecules to activate the cell
- amplification of the signal sometimes a million fold inside the cell
-both of these pathways do that because they are linked by an amplifier enzyme
159
Example of Receptor enzyme: tyrosine kinase receptor
- tyrosine kinase transfers phosphate group from ATP to a tyrosine residue (an amino acid) of a protein (phosphorylates tyrosine residues)
- this phosphorylated protein becomes activated and does other things inside the cell
160
Specific example of tyrosine kinase receptor: insulin receptor
1) Alpha subunit binds insulin (ligand)
2) Binding of insulin causes receptors to dimerize and autophosphorylate the beta subunit transmits a signal from the bound insulin to the cytoplasm
3) The dimerization and autophosphorylation activates kinase domain in the cytoplasm
4) Kinase domains on the receptor phosphorylate insulin receptor substrate, triggering other responses inside the cell
stages 1, 2, and 3 happen in the extracellular fluid and stage 4 happens in the intracellular matrix
161
G protein coupled receptor (GPCR)
- hundreds of known GPCR
- many have unknown functions (orphan receptors, many were discovered in the human genome project)
- also called:
- metabotropic receptors
- 7 transmembrane domain receptor (7TR)
- generate second messengers
162
why are they called G-proteins?
- because they bind to GDP and GTP
- inactive configuration: bind to GDP
- active configuration: exchange GDP for GTP
163
explain how a g-protein receptor works
- ligand binds to a membrane receptor
- activates signal transduction by G-proteins which activates an amplifier enzyme
- these generate second messenger molecules that can do 1 of 3 things:
- activate protein kinases, phosphorylate proteins
- increase intracellular Ca2+, calcium-binding proteins
- alter ion channels
164
GPCR example: andenylyl cyclase
1) Ligand binds to G-protein receptor
a. Activates the G-protein
b. 3 subunits (alpha, beta, y)
c. Once activated, the g protein can diffuse along the inside leaf of the membrane (lipid anchored protein)
d. Activated receptor can stimulate several G proteins
2) G protein diffuses along the inside of the membrane to activate amplifier enzyme adenylyl cyclase
a. Each g protein activates on adenylyl cyclase
3) Adenylyl cyclase converts several hundred ATP into cAMP
a. cAMP is the second messenger
b. They can diffuse throughout the cell
4) cAMP activates protein kinase A (PKA)
5) PKA diffuses within the cell to phosphorylate many other proteins
a. Many types of proteins can be phosphorylated, giving rise to complex cellular responses
165
PL-C
Phospholipase C
166
DAG
diacylglycerol
167
PK-C
protein kinase C
168
IP3
inositol triphosphate
169
ER
endoplasmic reticulum
170
GPCR example: phospholipase C
1) Ligand binds to and activates G protein receptor
2) G protein activated the phospholipase C (the amplifier enzyme)
3) PLC degrades membrane phospholipids into 2 2nd messengers: (Diacyglycerol and)Inositol tri-phosphate)
a. DAG stays associated with the lipid (it's a diglyceride)
b. IP3 is a small polar molecule that diffuses throughout the cytoplasm
4) DAG activates protein kinase C (PKC)
1. PKC diffuses within the cell, and phosphorylates other proteins
5) IP3 binds to the IP3 receptor on the endoplasmic reticulum
1. Activates IP3 receptor, allows store of Ca++ to be released into cytoplasm
2. This Ca++ becomes another second messenger***
171
what are 4 classic second messengers?
cAMP, cGMP, Ip3, DAG
172
name 3 novel second messengers
Ca++, gasses, lipids
173
calcium as a second messenger
1) Binds to the calcium binding protein calmodulin to activate other proteins
2) Binds to motor proteins and allows action of cytoskeleton and motor proteins
3) Binds to synaptic proteins to trigger exocytosis
4) Binds to ion channels to modulate their gating (Ca++ gated ion channels)
5) In fertilized eggs, initiates development
174
gases as second messengers
- soluble gasses are now being recognized as second messengers
- NO (nitric oxide)
- synthesized by NO-synthase
- NO has half-life of 2-30 seconds
- synthesized by endothelial cells of arteries, and diffuses into adjacent arterial smooth muscle
- activates guanylyl cyclase, production of cGMP leads to relaxation of smooth muscle
- CO (carbon monoxide)
- activated guanylyl cyclase (small amounts are generated within signaling pathways that produces cGMP)
- H2S (hydrogen sulfide)
175
GPCR example: arachadonic acid
- the arachadonic acid pathway is similar to the PL-C pathway
- g proteins activate phospholipase A2 (amplifier enzyme)
- PLA2 degrades phospholipids into arachadonic acid (an eicosanoid)
- arachadonic acid (and its eicosanoid metabolites)
- are themselves second messengers within a cell
- diffuse out of the cell and act as a ligand for GPCR cell membrane and adjacent cells
176
For years, physiologists were not able to explain why the hormone epinephrine caused some blood vessels to constrict and others to dilate, we know now that the reason for this is what?
the presence of receptor isoforms, these are linked to different pathways
beta2 receptor dilates, alpha receptor constricts
177
Some ligands can activate ______ receptors (epinephrine activates alpha and beta2 receptors), while some receptors are ______ (activated by more than one ligand) (alpha and beta2 receptors can be activated by epinephrine or norepinephrine)
multiple, promiscuous
178
the receptor numbers can be be upragulated or down regulated because of what 3 things?
- development (developing cells have different needs)
- homeostatic challenges
- disease states (sometimes the change in receptor expression might be the cause of the disease, or could be just one of the symptoms)
179
how can receptors be desensitized?
- phosphorylation of an alpha and beta2 receptor can cause them to have lower affinity for ligands
- mechanism of drug tolerance as a result continuous exposure to an agonist
180
control pathways: response and feedback loops
-control pathways are generally organized in this kind of manner
- integrating center has to do calculations and make changes
- that signal is carried away (efferent pathway)
- targets tissues and cells
- this generates a response
- this response is intended to generate a signal that will change the amplitude of that stimulus
- feedback loop (what happens between generating this response and the stimulus
181
negative feedback
- response is meant to decrease the magnitude of the stimulus and shut the loop off
- ex: circulating glucose, insulin becomes secreted and starts taking up glucose that lowers the circulating level of glucose, the response loop will shut off because it brings it back to the initial homeostatic state
182
positive feedback
- not a lot of examples
- start with a stimulus/response
- response changes some part of your system
- instead of acting to stay at set point, it goes past the set point
- only way it can be shut off is if an outside factor shuts it off
183
what are the differences between a negative feedback and a positive feedback?
Negative feedback:
- keeps a system near a setpoint
- response acts to negate the stimulus
- response can restore homeostasis, but cannot prevent the initial pertubation
Positive feedback:
- brings a system further from a setpoint
- response acts to reinforce the stimulus
- requires an outside factor to shut off
- non-homeostatic (but many people disagree)
184
feedforward control
- a small stimulus sets off a chain of events aimed at preventing a pertubation
- ex: fight or flight system
- requires a complex program
- mouth watering in anticipation of food is an often used example
- psychologists may disagree because of the influence of learning
- ex: controlled movement
185
Neural signaling is aimed ________, _____ acting, and ______ lived, while endocrine signaling is determined by only receptors, ______ acting, and _______
at a specific target, fast, short
| slower, lasts longer
186
electrochemical gradient
Combination of an electrical gradient and chemical gradient
- ions subjected to an electrochemical gradient will move
- when there's an electrical and chemical gradient, we consider them as together, not independent
187
membrane potential of a cell
- is due to electrical gradient across a cell membrane
- unequal distribution of charges (ions)
- established by ATPase transporters
- measured in mV (millivolts)
- not constant
- membrane potential can change due to movement of ions
188
resting membrane potential (RMP)
- special case of steady-state balance between active transport and leakage ions
- steady state, NOT equilibrium
- for most cells, it's between -20 mV and -90 mV
189
In depolarization of the membrane potential, the membrane potential difference ______, in hyperpolarization, the membrane potential difference ______
decreases, increases
190
In a hypothetical cell, the concentration of K+ is maintained over time. The system is at a steady state where the rate of leakage through leakage channels is exactly balanced by active transport
Is this equilibrium? Why or why not?
no because it requires a constant energy supply
191
Imagine a hypothetical cell where the K+ pump stops working and no more K+ is going inside the cell. K+ leaks due to the electrochemical gradient
Is this equilibrium?
yes
192
Imagine a hypothetical cell where the K+ pump stops working. How can we make K+ stay inside if we shut off the pump?
- make the inside negatively charged to attract K+ ions
- we say :"make the inside negative with respect to the outside"
- the amount of voltage necessary to keep the K+ inside is called the equilibrium potential (even though it's not really an equilibrium)
193
equilibrium potential
- the membrane potential that exactly opposes the steady state electrochemical gradient for an ion
- follows the convention "inside with respect to the outside"
194
We can calculate the equilibrium potential for any ion at 37 degrees Celsius, given a concentration gradient with the _____
nernst equation
Eion = 61/z x log ( [ion] out/ [ion] in)
-where z = valence of the ion in question (+1, +2, -1), and log has a base of 10
195
What is the equilibrium potential of K+ at physiological concentration?
-90 mV
196
The equilibrium potential for each ion is ______ of the concentration of the other ions
independent
197
If only one ion was ______, resting membrane potential would be the ______ for that ion
-ex: if K+ was the only permeant ion, RMP would be -90.1 mV
permeant, equilibrium potential
However, all real cells are permeable to Cl- K+ and Na+
198
For every 1 Na+ that leaks out of the membrane, ___ K+ and ___ Cl- will leak
50, 10
199
goldman equation
Predicts the resting membrane potential considering
1) Relative permeability of Na+, K+ and Cl-
2) The concentrations inside and outside the cell
200
why isn't calcium included in the goldman equation?
Calcium is not there, at rest, the permeability of Ca ++ is 0, if we did include it in this equation, it would immediately go to 0
-it's impermeable across a cell membrane
201
what is the correct way to write the goldman equation?
RMP = 61 x log (Pk x [K]out + Pna [Na]out + Pcl [Cl] in)
Pk [K]in + Pna [Na] in + Pcl [Cl] out
Cl- is switched because of its negative charge
"looks like 3 nernst equations"
202
The normal, healthy resting membrane potential for a cell is 78 mV let's say. If there was a kidney failure which resulted in elevated amounts of K+ outside the cell, what would happen to the membrane potential? (we call this hyperkalemic)
would become -67 mV (depolarization)
203
The normal, healthy resting membrane potential for a cell is 78 mV let's say. If someone had severe diarrhea, resulting in low concentrations of K+ outside the cell, what would happen to the resting membrane potential? (hypokalemic)
would become -89 mV (hyperpolarization)
204
The normal, healthy resting membrane potential for a cell is 78 mV let's say. If high levels of anti-diuretic hormones were given to someone (which causes you to retain water), what would happen to the resting membrane potential? (hyponatremic)
would become -79 mV (hyperpolarization)
205
What could cause a rapid increase in the permeability of Na+ in a cell?
Na+ permeability changes during an action potential
206
the movement of ions has no effect on the membrane potential of a cell
True or False?
false, the movement of ions does affect the membrane potential of a cell
207
Declare the relevant concentration inside, the equilibrium potential (physiological conditions), and the direction of movement when ion channels open of the following ions: K+, Na+, Ca++, Cl-
K+: high; -90 mV; out
Na+: low; +60 mV; in
Ca++: low; +122 mV; in
Cl-: low; -81 mV; in
208
concentration gradient is the only factor that determines the movement of ions
True or False?
you cannot always look at the [ ] gradient to decide which way ions move, because diseases or experimental situations can alter concentrations
-to understand why ions move the way they do, you need to consider both equilibrium potential and membrane potential of the cell
209
________ allow ions to diffuse across membranes down their electrochemical gradient
ion channels
210
when ion channels open, the ion always moves to make the membrane potential ______ to the equilibrium potential
equal
211
if the resting membrane potential of a cell is -78 mV and the equilibrium potential is -50 mV, in what direction will the Cl- move?
Cl- will move out of the cell
| against concentration gradient
212
if the resting membrane of a cell is -78 mV and the eqilibrium potential is +60 mV, which way will the Na+ move?
Na+ will move into the cell
213
if the resting membrane potential of a cell is -78 mV and the equilibrium potential is -80 mV, which way will the Cl- move?
inside the cell
214
peripheral nervous system
- sensory branch, gather info and sends it to CNS
| - efferent branch- controls things like muscle, autonomic functions
215
central nervous system
-sits in the middle, gather info from the sensory branch of PNS
216
what are the 2 main types of cell in the nervous system? what is their main role?
neurons and glia cells, they are specialized for communication
217
___ % of the literature regarding the nervous system is made up of neurons and ___ % is made up of glia cells
95, 5
**but, glia cells make up most of the body
218
neurons
- specialized to carry electrical signals and communicate with other cells
- they have a unique morphology (axons, dendrites, can communicate with distant targets)
- high density of ion channels
- special transport mechanisms to move materials from one end to the other (depends on cytoskeleton)
- secrete signaling molecules (neurotransmitters and neurohormones)
219
Part of the neuron where the cell body turns into the axon, the action potential is generated here and it has a high density of ion channels
Axon hillock
220
Part of the neuron that gathers information and where neurons make contact
dendrites
221
Cell that our neurons try to communicate with
post-synaptic cell
222
Pseudounipolar and bipolar neurons are what kind of neuron
sensory
223
what are the 4 types of glia cells in the CNS?
- oligodendrocytes: myelinate axons
- ependymal cells: line ventricles, make neural stem cells (replace injured neurons, forms waterproof barrier)
- microglia: no specific shape, derived from bone marrow; "immune cells"
- astrocytes: blood brain barrier, trophic factors (essential for neuron survival, allow neurons to sprout new dendrites, take up excess water and K+(causes change in the membrane potential), neural stem cells, pass lactate to neurons
224
what are the 2 types of glia cells in the ANS?
- satellite cells: trophic factors (similar to astrocytes)
| - schwann cells: myelinate axons
225
What 2 factors lead to the resting membrane potential (RMP)?
ion gradients and relative permeability
226
True or False?
Membrane potential will change if ion channels open and allow ions to move across cell membrane
true
227
Ion channels are classified according to what 3 things?
- the ions they carry
- where on the cells they are located
- gating mechanisms
228
neurons are one of the few places in the body that don't contain a high density of ion channels
True or False?
false, neurons contain a high density of ion channels
229
what are the 5 different gating mechanisms for ion channels?
1) voltage gated ion channel
2) receptor channels
3) phosphorylation gated
4) stretch gated
5) temperature gated
230
what is a voltage gated ion channel?
changes in the membrane potential open the channel
231
what are receptor channels?
(ligand gated ion channels)
- gate when they bind a ligand (neurotransmitter, cGMP, Ca++, etc.)
- can bind to the intracellular side as well as the extracellular side, if there's an increase in intracellular ion specified, the channels open (ex: Ca++)
232
what is a phosphorylation gated ion channel?
enzymes that phosphorylate other proteins, created a conformation change in the protein, causes the ion channels to open
233
what is a stretch gated ion channel?
gated by changes in the shape of the cells membrane
| -ex: ion channels in touch receptors, the depression of the touch receptors activate the ion channels
234
what is a temperature gated ion channel?
changes in temperature activate the channel
| -temperature can go up or down (there are warm sensitive and cold sensitive ion channels)
235
what is the basis of electrical signalling?
opening and closing of ion channels (thus changing the flow of ions) causes rapid changes in the membrane potential which is the basis of electrical signaling
236
graded potential
1) signals communicated from one neuron to the next are graded potentials: postsynaptic potentials
- a small 'subthreshold' change int he membrane potential does not usually cause an action potential
- can be depolarizing or hyperpolarizing
- passive
- proportional to the size of the stimulus
- caused by the flow of ions through a few ion channels
- gradually dissipate as they travel through a cell (lose power)
- can be summer
237
describe the strength of a graded potential as it moves further away from the source
- graded potential travels like a ripple on a pond
- moves outward from the source and degrades as it moves farther away
- take time to get from synapse to the axon hillock
- eventually degrades to nothing
238
why does the signal of a graded potential degrade?
- there is electrical resistance in the cytoplasm
| - the cell membrane is leaky to ions
239
action potential
wave of depolarization that propagates across neuronal membrane (= regenerative)
- "all or none"
- fast, only last a few milliseconds
- often called a spike action potential
- have a large amplitude, about 100 mV (from resting membrane potential to peak)
- ALWAYS depolarizing
- requires the membrane to be depolarized past a threshold
- there is a refractory period
- these CANNOT be summed
- in neurons, the site of AP generation is the axon hillock
240
explain the physiological process of an action potential in 9 steps
1) cell is at resting membrane potential (RMP)
2) cell is depolarized by the graded potential
3) membrane depolarized to the threshold (voltage gated Na+ channels open quickly, Na+ enters cell, voltage gated K+ channels begin to open, slowly)
4) rapid Na+ entry depolarizes cell
5) Na+ channels inactivate and slower K+ channels fully open (THESE DO NOT CLOSE THEY JUST INACTIVATE)
6) K+ leaves the cell (repolarize membrane)
7) K+ channels remain open and additional K+ leaves cell, hyperpolarizing it (afterhyperpolarization)
8) voltage gated K+ channels close, less K+ leaks out of the cell, Na+ channels begin to recover
9) cell returns to resting ion permeability and resting membrane potential, Na+ channels mostly recovered
241
when does the refractory period of an action potential start?
refractory period starts at the beginning of the action potential
242
absolute refractory period
no matter what, you cannot make the cell fire another action potential because all the sodium channels are already involved or are in a inactivated state
243
relative refractory period
enough Na+ ions have recovered, a stronger stimulus than normal will make the cell fire an action potential
244
tonic action potential
cell is constantly firing action potentials
245
single action potential
one action potential is fired
246
bursting action potential
cell fires action potentials in bursts
247
changes in extracellular K+ influence the transmission of action potentials
true or false?
true, K+ has a big influence on whether or not an action potential will be fired
248
hyperkalemia
- resting membrane potential is depolarized (elevated levels of extracellular K+)
- smaller stimulus will bring the cell to the threshold
249
hypokalemia
- resting membrane potential is hyperpolarized (lower levels of extracellular K+)
- requires a larger stimulus to bring the cell to the threshold
250
an action potential is conducted from the _____ to the _____ of an axon
soma, terminals
251
local current flow of an action potential
-when a section of axon depolarizes, positive charges move by local current flow into adjacent sections of the cytoplasm. ont eh extracellular surface, current flows toward the depolarized region
252
a cell at rest is ____ on the inside and ____ on the outside. during an action potential, the cell is _____ on the inside and _____ on the outside
negative, positive, positive, negative
253
what is the initial state of a neuron before an action potential is fired
normal ion gradients, RMP = approx. -80mV
- very high density of Na+ channels at the axon hillock (trigger zone)
- voltage gated Na+ and K+ channels distributed along the axon
254
in an action potential, some Na+ is attracted to the nearby areas (local current flow), why doesn't the action potential go "backwards" back towards to axon hillock?
the axon hillock would be in the refractory period and the action potential would keep moving down the axon going the other way, depolarizing nearby axons as it goes, making them reach their thresholds therefore putting them in refractory
255
what is myelin formed from?
concentric layers of glial cell membrane
- up to 200 layers
- almost no ion channels under the layers of myelin
256
what does the myelin do?
increase electrical efficiency of the axons
257
what is the purpose of the nodes of ranvier?
- one node will fire an action potential
- action potential jumps from one node to the next, rather than travelling as a wave: saltatory conduction
- Na+ channels are only found on the nodes (at high density), not on the myelin
258
what happens in demyelinating diseases?
- conduction slows when current leaks out of the previously insulated regions between the nodes
- failure of action potentials, leads to clinical symptoms
259
what are the 2 ways to speed up velocity of an action potential?
1) increase the axon diameter
- increases velocity because as the axon radius becomes larger, internal resistance decreases (inverse square relationship)
2) myelination
- increase velocity because insulated areas mean less leakage of Na+ and K+
- also means less ATP used
- myelination allows axons to be smaller, so you can fit more into a space
260
we have the axon of a squid that has a diameter from 50-1000 um that is not myelinated, we also have the axon of a cat that is 22 um in diameter and is myelinated. Which action potential will be faster?
the cat axon, with the shorter diameter and myelinated
-large diameter axons can really speed up axonal conduction of an action potential, but myelination allows even faster conduction in less space
261
multiple sclerosis
- autoimmune disease
- unknown cause: environment, virus, genetics, cerebral blood flow
- causes teh demyelination of CNS axons
- multiple patterns of progression: relapsing-remitting and several progressive phase to symptoms
262
what can be some of the symptoms of multiple sclerosis? what are some treatments?
- loss of balance, loss of speech, loss of vision, abnormal pupil reflexes, numbness, pain
- treatments include immunosuppressents, other drugs as indicated by symptoms
263
Guillain Barre syndrome
- demyelinating disease
- autoimmune, can appear days after seemingly minor GI or lung infection
- May also be associated with chrinic illness such as lupus, HIV
- demyelination of sensory, motor and autonomic axons (PNS)
- slowing and/or loss of action potential conduction
264
what are the symptoms of Guillain Barre syndrome? What are some treatments?
initial symptoms: tingling, weakness, pain in hands/feet
-symptoms may rapidly progress to inability to speak, paralysis, respiratory disease
- treatment may include plasmapheresis (to remove antibodies from blood) and immunoglobulin G (IGG) to inactivate circulating antobodies
- most people survive, recovery can take months to years
265
Fugu poison
- kills 30-100 people per year
- also called tetrodotoxin (TTX)
- comes from pufferfish and several other species
- very specific antagonist of voltage gated Na+ channels, prevents the entry of Na+ into cells (blocks ability of heart and diaphragm)
- prevents action potentials in neurons and muscle
- lidocaine, benzocaine, and other local anaesthetics also block Na+ channels
266
synapses
-connection between two neurons or a neuron and another cell that is specialized for the transfer of information
267
synapses can be classified based on what characteristics?
- based on function (electrical vs chemical)
| - can be classified based on location (axodendritic, axosomatic, axoaxonic)
268
_______ causes graded potentials in the postsynapctic cell
synaptic activity
269
a depolarizing synaptic potential is called an _______
excitatory postsynaptic potential (EPSP)
| -close to the threshold to fire an action potential
270
a hyperpolarizing synaptic potential is called an _____
inhibitory postsynaptic potential (IPSP)
| -further away from the threshold to fire an action potential
271
the grand sum of EPSP and IPSP at the axon hillock will determine if the threshold potential is exceeded and an action potential in stimulated
true or false?
true
272
electrical synapse
-ex: gap junction
electrical signal passes directly between two cells
-carried by the movement of ions
-usually bidirectional (if one cell depolarizes, the one connected to it by gap junction will depolarize as well
-FAST (0.2 ms)
-small molecules can travel through gap junctions (ATP, Ca++, some other 2nd messengers)
-allows cells to fire action potential synchronously
273
what is a gap junction?
- electrical synapses can travel through these
- 12 proteins in total will make the gap junction (6 on each side)
- each connexon in a gap junction is made of 6 connexin monomers
- two connexons for a functional gap junction
- gap junctions from two cells must align to form a functional channel
- the space of synaptic cleft is very close (2-4 nm)
274
chemical synapse
- specialized form of exocytosis
- release of neurotransmitter from presynaptic cells to influence electrical activity in postsynaptic cell (neurons communicate with eachother, neurons communicate with post-synaptic targets (muscle, glands))
- estimated 100-600 trillion synapses in the brain (0.5-1 billion per mm square in some areas of brain)
- electrical signal from one neuron is converted to a chemical signal to cross a synaptic cleft, then is often converted back to an electrical signal
275
what is the difference int eh synaptic cleft in a chemical synapse vs an electrical synapse?
chemical synapse: larger space (20-40 nM)
| -electrical synapse: smaller space (2-4 nM)
276
what is an example of a chemical synapse?
- presynaptic cell and a postsynaptic cell
| - axons terminal releases neurotransmitters onto postsynaptic receptors, which will then bind to correct area
277
what are the 3 classic neurotransmitters?
- acetylcholine
- amines (norepinephrine, dopamine, histamine, serotonin)
- amino acids (glutamate, GABA)
-we have known about these for the longest, they behave more predictably
278
what are the 4 novel neurotransmitters?
- peptides (oxytocin, melanocortin)
- purines (ATP)
- gases (nitric oxide)
- lipids (eicosanoids)
-widely recognized in the past 25+ years
279
explain the synaptic communication between a pre and a post-synaptic cell
1) action potential travels down axon, depolarizatio opens voltageg ated Ca++ channels
- allows Ca++ to enter presynaptic terminals
2) Ca++ entry causes some synaptic vesicles to fuse with presynaptic membrane and release their neurotransmitter contents into the synaptic cleft
3) neurotransmitter binds to postsynaptic receptors, some receptors are ion channels, some are GPCR. postsynaptic response depends on type of receptor
- time taken to diffuse across and cause postsynaptic response is called the synaptic delay (about 2ms) (**electrical synapses are 10x faster)
4) neurotransmitter is removed from the cleft
280
in synaptic communication, what are 4 ways neurotransmitters can be removed from the cleft?
1) destroyed in the synaptic cleft by a degradative enzyme
2) transported back into the terminal by active transport. recycled and repackaged back into vesicles
3) diffuses away from synapse
4) taken up into postsynaptic cell by endosytosis
281
in synaptic communication, why is it important to get rid of the neurotransmitter from the postsynaptic cleft?
- prevent desensitization, affinity could go down if too much neurotransmitter is always there
- if the neurotransmitter stays there, they would keep doing their job (ex: synapse between motor neuron and skeletal muscle cell)
282
what are the 4 steps of the synthesis and recycling of acetylcholine?
1) acetylcholine (ACh) is made from choline and acetyl CoA
2) in the synaptic cleft ACh is rapidly broken down into choling and acetic acid by the enzyme acetylcholinesterase
3) choline is transported back into the axon terminal by cotransport with Na+
4) recycled choline is used to make more ACh
283
acetylcholine
-neurotransmitter at a cholinergic synapse
- used by:
- motor neurons to cause excitation of skeletal muscle
- every pathway of the autonomic nervous system
- used diffusely throughout the central nervous system as a neuromodulator (modulate activity of other neurons)
- two main kinds of receptors for ACh:
- receptor channels (nicotinic receptor)
- GPCR (muscarinic receptor)
284
niotinic receptor
nicotine binds to these receptors and causes them to open
285
muscarinic receptor
- there's a drug that can be purified by mushrooms called muscarin
- causes receptors to activate
286
nicotinic receptors allow mostly ___ to move through, causing a _____ of the cell
Na+, depolarization (or EPSP)
287
the fast EPSP (excitatory post synaptic potential)
- binding of ACh to receptor channel causes:
- opening of channel
- entry of Na+ (and exit of a small amount of K+)
- movement of positive charge into cell causes depolarization
- postsynaptic depolarization is excitatory = EPSP
- FAST (happens after a delay of milliseconds (not as fast as electric synapse)
288
slow EPSP
binding of ACh to GPCR causes:
- generation of second messengers
- activation of kinases
- phosphorylation of proteins in the postsynaptic membrane
- some of the protein that get phosphorylated are phosphorylation gated ion channels
- phosphorylation can gate some ion channels open
- some can gate ion channels closed
- A common effect is closure of K+ leak channels
- causes depolarization
- the small postsynaptic depolarization is excitatory = EPSP
- SLOW (happens after a delay of seconds)
289
norepinephrine
- called an noradrenergic synapse
- neurotramsmitter used diffusely throughout the CNS and by the sympathetic branch of ANS
- several sybtypes of receptors (all are GPCR- alpha and beta receptors)
290
glutamate
- called a glutamatergic synapse
- main excitatory neurotransmitter used throughout the CNS
- 2 types of receptors:
1) receptor channels (ionotropic) - ion gated channels
- NMDA receptor
- AMPA receptor
- Kainate receptor (not as common)
2) GPCR (metabotropic glutamate receptors)
- several subtypes
291
AMPA receptor (ionotropic)
- glutamatergic receptor
- allows Na+ to pass (some K+)
- depolarizes cell (similar to nicotinic receptor)
292
NMDA receptor (ionotropic)
- glutamatergic receptor
- Allows Na+ and Ca++ to enter (some K+ leaves)
- inward movement of Na+ and Ca++ depolarizes cell
- is normally blocked by Mg++, Mg++ is ejected when membrane is depolarized
- so, binding of glutamate does not open the channel until it becomes depolarized
293
GABA
- called a GABAergic synapse
- main inhibitory neurotransmitter used throughout the CNS
2 kinds of receptors:
- one is a receptor channel (ligand gated ion channel)
- one is GPCR (metabotropic GABA receptor)
294
fast IPSP
binding of GABA to receptor channel causes:
- opening of channel
- negatively charged Cl-
- movement of negative charge into cell causes hyperpolarization
- small postsynaptic hyperpolarization is inhibitory = IPSP
- FAST (few ms)
295
which synaptic receptors, a receptor channel or GPCR, causes a faster postsynaptic response? why?
receptor channel is faster because as soon as it binds its ligand it allows ions to cross the membrane
-GPCR has a lot of second messengers, many enzymatic reactions need to occur before channel opens
296
______ create rapid, short-acting fast synaptic potentials; ______ create slow synaptic potentials and long-term effects
neurotransmitters, neuromodulators
297
chemical vs electrical synapse
-electrical synapse: fast and simple (0.2 ms) - connection from pre to post synaptic cell
Chemical synapse:
- relatively complex, slower (at least 2 ms, might take 20)
- electrical signal form one neuron is converted to a chemical signal to cross a synaptic cleft, then is often converted back to an electrical signal (allows excitatory signals to become inhibitory, allows modulation of signals, very efficient: a few molecules of neurotransmitter can have a large electrical effect)
- wide variety of receptors, even for a single neurotransmitter (Ex: serotonin has at least 20 different receptors
298
summarize the neurotransmitter and associated receptors
AChR: Na+ (and a llittle K+) = depolarization
NMDA: Na+, Ca++, K+ = depolarization
AMPA: Na+ (and a little K+) = depolarization
GABAa: Cl- = hyperpolarization
299
synaptic integration
refers to the idea that whether or not the postsynaptic neuron fires an action potential depends on the grand sum of synaptic activity acting on the cell
a number of factors will play important roles in how the synaptic info "add up"
1) AP frequency
2) divergence and convergence (if the cell is receiving a lot of synaptic input)
3) temporal and spatial summation
4) location of synapses on postsynaptic cell
300
the frequency of an action potential firing indicates the ______ of a stimulus. A ______ stimulus releases little neurotransmitter; a ______ stimulus causes more action potentials and releases more neurotransmitters
strength, weak, strong
301
______ of an action potential determines how much of a neurotransmitter will be released
frequency
302
in a ______ pathway, one presynaptic neuron branches to affect a larger number of postsynaptic c=neurons. In a ______ pathway, many presynaptic neurons provide inout to influence a smaller number of postsynaptic neurons
divergent, convergent
303
temporal summation
occurs when two graded potentials from one presynaptic neuron occur close together in time
-two subthreshold graded potentials will not initiate an action potential if they are far apart in time
304
spatial summation
occurs when the currents from neatly simultaneous graded potentials combine
ex: 3 excitatory neurons fire. their graded potentials separately are all below threshold; graded potentials arrive at trigger zone together and sum to create a suprathreshold signal; action potential is generated
ex: one inhibitory and 2 excitatory neurons fire; the summed potentials are below threshold, no action potential
305
axodendritic type of synapse
-synapse that's on the dendrite of a post synaptic cell
306
axosomatic type of synapse
synapse forming on the cell body of the post synaptic cell
307
axoaxonic type of synapse (on axon)
synapse on the axon of the post synaptic cell
| -this one is already on the trigger zone, will be more powerful, almost no distance to travel
308
axoaxonic type of synapse (on terminals)
- forms on synaptic terminals
- much more subtle affects
- synaptic facilitation: depolarizes the terminal by just a bit, not enough to make it release neurotransmitter but enough to increase Ca++
- increase in intracellular Ca++ = facilitate the release of neurotransmitter
- presynaptic inhibition: action potential might not reach the threshold because terminal has been hyperpolarized
- modulates which synapses are more powerful than other synapses
309
long term potentiation
- long term change in the strength of a synapse
- synaptic plasticity is the ability of neurons to change synaptic strength (potentiation & depression)
- long-term potentiation (LTP) and long term depression (LTD)
- LTP = stronger LTD = weaker
- happens in many kinds of neurons
- widely thought to underlie to process of learning
- best studied neurons that exhibit LTP in mammalian brain are in hippocampus
310
the hippocampus is in the area of the ____ lobe
temporal
311
there are several mechanisms of long term potentiation (LTP) what are they?
(specific example from notes)
- initiated by a period of high frequency action potentials in the presynaptic neurons. causes a long lasting potentiation of the EPSP (increase in depolarization casued by a single presynaptic AP)
- requires NMDA & AMPA receptors in post synaptic membrane
- metabotropic glutamate receptors also play a role
- ride in intracellular Ca++ is crucial
- pre and post synaptic changes
- changes in protein expression required for permanent change
312
name the 6 steps in long term potentiation of the example in the notes
1) glutamate binds to AMPA and NMDA channels
2) net Na+ entry through SMPA channels depolarizes the postsynaptic cell
3) depolarization ejects Mg2+ from NMDA receptor-channel and opens channel
4) Ca2+ enters cytoplasm through NMDA channel
5) Ca2+ activates second messenger pathways
6) paracrine from postsynaptic cell enhances glutamate release
313
the 3 types of glutamate receptors play a key role in long term potentiation, what are these?
1) metabotropic
2) AMPA (carries mostly Na+)
3) NMDA (carries Na+ and Ca++ CELL MUST BE DEPOLARIZED IN ORDER TO GATE OPEN
314
steps to induce long term potentiation
1) high frequency stimulation of presynaptic neuron, release of glutamate
2) activation of AMPA receptors leads to depolarization of the psot-synaptic neuron via EPSPs. depolarization releases block of the NMDA receptor (this allows the NMDA to conduct Ca++ into the cell)
3) continued synaptic activity also activates metabotropic receptors. activates a 2nd messenger pathway that releases intracellular stores of Ca++ ions
4) postsynaptic terminal experiences extremely large increase in intracellular Ca++ [ ]
5) increase Ca++ leads to activation of kinases
- phosphorylation of AMPA receptors, increasing affinity and conductance
- insertion of new AMPA receptors
- generation of retrograde messengers (carbon monoxide, nitric oxide) that facilitate release of vesicles
315
in order to create new memories, long term potentiation has to do what?
- create changes in gene expression
| - create new synapses
316
at the 3rd week of development, the human brain starts as a _____, by the 4th week it specializes in what?
hollow tube; the anterior end (forebrain, midbrain, hindbrain, spinal cord)
317
at 4-6 weeks, the forebrain develops into _____, the midbrain develops into _____, the hindbrain develops into_______
cerebrum & diencephalon; midbrain; ponds & cerebellum, medulla oblongata
318
describe the human brain at 11 weeks
- cerebrum (much bigger, a lot of cell division and reorganization)
- diencephalon
- midbrain
- pons
- cerebellum
- medulla oblongata
- spinal cord
319
the cerebrum contains the thalamus and the hypothalamus
true or false?
false, the diencephalon contains the thalamus and the hypothalamus
320
what are the derivatives of the cerebrum?
- cerebral hemispheres
- basal ganglia
- lateral and 3 ventricles
321
what are the derivatives of the midbrain?
- superior, inferior colliculi
| - substantia nigra
322
ventricles
fluid filled cavitites within the brain, remnants of the hollow tube from which the brain developed
323
central canal
hollow tube in the spinal cord; continuous with the ventricles
324
grey matter
unmyelinated cell bodies, axon terminals and dendrites. neuronal cell bodies are most often found clustered together in groups called nuclei, or on the outer surface of the brain as the cerebral cortex
325
white matter
myelinated axons
326
what things support and protect the CNS?
- bony skull and vertebral column
- wrapped by 3 protective and nourishing membrane called meninges
- cerebrospinal fluid
- blood-brain barrier
327
dura mater
important for blood circulation in CNS
328
pia mater
follows surface of the brain
329
arachnoid membrane
connected to pia pater by fine fibrous connections
330
arachnoid trabeculae
anchor arachnoid membranes to pia mater
331
dural sinus
vein draining blood from the brain, coming into dural sinus, carries blood away from the brain and through the skull
332
meningitis
is a contagious bacterial, viral or fungal infection of the meninges causing swelling and pressure on the brain
333
a traumatic head injury can cause:
- epidural bleeding (between skull and dura)
- subdural bleeding (between dura and arachnoid)
- subarachnoid bleeding (between the arachnoid membrane and pia mater)
brain bleeds are very difficult to repair
334
explain cerebrospinal fluid circulation
1) produced by the choroid plexus in the ventricles
2) exits brain through foramen of Magendie
3) some circulates around the spinal cord, some circulates into subarachnoid space
4) enter arachnoid granulations, and crosses into venous blood
335
why is CSF important?
- helps maintain proper solute concentrations in the interstitial fluid surrounding neurons
- helps remove waste
- provides a cushion for the brain
336
blood-brain barrier
- barrier between the interstitial fluid of the brain and the plasma
- due to the specialized anatomy of blood vessels in the CNS
- keeps unwanted materials out, keep wanted materials in
337
explain the endothelial cells in the circulation of the body versus the ones in the circulation in the CNS
endothelial cells are not connected and have pores connecting luminal to extraluminal side = ver leaky; endothelial cells are joined by tight junctions, surrounded by astrocyte endfeet - molecules need to be fat soluble to cross
338
what type of molecules can cross the blood-brain barrier?
- only lipophilic molecules can cross (steroids, ethanol, nicotine, benadryl)
- polar, hydrophilic molecules can only cross via transporters (insulin, glucose, Na+)
339
spinal cord
major pathway between the brain and skin, muscle, joints, and organs
340
what are the 4 levels of the spinal cord?
- cervical, thoracic, lumbar, sacral (also coccygeal)
- 31 pairs of spinal nerves in total
- after L1-L2, the SC consists of thick, elongated nerve roots called cauda equina
341
what are the 2 segments of the spinal cord?
- dorsal (sensory)
| - ventral (control/motor)
342
the spinal cord has its own internal ciruitry to mediate simple reflexes and generates complicated control programs, such as:
rhythmic patterns used for walking
343
which segment of the spinal cord has the enlargement filled with cell bodies?
dorsal root
344
what is the name of the nerve that carries efferent and afferent information?
spinal nerve
345
visceral sensory nuclei
collects info from internal organs
346
somatic sensory nuclei
cell bodies gather info from skeletal muscles and send it up the level of the spinal cord
347
autonomic efferent nuclei
gather information from organs (automatic functions)
348
somatic motor control nuclei
collect information from skeletal muscle (somatic motor control)
349
ascending tracts
- segmentation in the white matter
| - axons carrying information back to the brain
350
descending tracts
medial or ventral aspect of the brain, bringing information from the brain to different parts of the body
351
what is the oldest region of the brain?
brain stem
352
brainstem
- transition between brain and spinal cord
- consists of: midbrain, pons, medulla, NOT CEREBELLUM
- most of cranial nerves (10/12 oairs) arise from the brian stem:
- pairs of nerves emerging from CNS that carry sensory info from periphery to CNS, and/or carry efferent info to tarfet organs
- some fiber carry info to the brain (sensory), some away (motor), and some carry both
353
what do the neuronal clusters (nuclei) within the medulla control?
heart and blood vessel function, respiration, and many digestive functions
354
brainstem: reticular formation
- receives and integrate incoming sensory input. plays a critical role in arousal
- gives rise to groups of diffuse modulatory neurons
355
brainstem: pons
acts as a relay station for cerebellym and cerebrum: plays a role in regulating muscle refelxes involved in equilibrium and posture
356
brainstem: midbrain
- critical relay for visual and auditory info
- governs movement of the eyes
- gives rise to groups of diffuse modulatory neurons
357
brainstem: diffuse modulatory neurons
what are the 4 diffuse modulatory systems?
1) norepinephrine (hypothalamus, thalamus, cerebellum, locus coerculeus)
2) serotonin (basal nuclei, raphe nuclei)
3) dopamine (prefrontal cortex, ventral tegmental area, basal nuclei, substantia nigra)
4) acetylcholine (cingulate gyrus, fornix, pontine nuclei)
358
cerebellum
- processes sensory info from muscles, joints, vestibular system, eyes. integrates position and movement of body with intent to move body
- important in maintaining balance and controls eye movements
- enhances muscle tone and coordinates skilled, voluntary movements
- plays role in planning and initiating voluntary activity by providing input to cortical motor areas
- stores procedural memories
-also has a newly discovered function in cognition (could be the cause of autism)
359
diencephalon: thalamus
- main relay centre for most types of information, receives information from almost every area of the CNS, and send information to these same areas
- sensory, emotional, motor, arousal
360
diencephalone: hypothalamus
-brain area most involved in directly regulating internal environment
functions:
- controls body temperature
- controls thirst and urine output
- controls food intake
- controls anterior pituitary hormone secretion
- produces vasopressin & oxytocin
- controls uterine contractions and milk ejection
- serves as a major ANS coordinating center
- plays role in emotional and behavioural patterns, including reproduction, sexual orientation maybe?
361
hypothalamus and sexuality
- 1991, Simon LeVay published a paper indicating a morphological difference in a nucleus of the hypothalamus between gay and straight men, the area in gay men was more similar to females
- very controversial findings
- accused of being biased
362
cerebrum
- largest and most distinct part of human brain (makes up about 80% of total brain weight)
- folded, showing gyri and sulci. these are used as landmarks
- evolutionarily, the newest
several parts
- cortex
- white matter
- basal ganglia
- limbic system
363
cerebrum: cortex
- outer surface is highly convoluted cerebral cortex
- highest, most complex integrating area of the brain
- plays a key role in the most sophisticated neural functions
each half of cortex is divided into 5 major lobes
-occipital, temporal, parietal, frontal, insular*
364
frontal lobe function
-skeletal muscle movement
- primary motor cortex
- motor association area (premotor cortex) : neurons become activated when you're simply thinking about doing something
365
parietal lobe function
- primary somatic sensory cortex: first are of the cortex that's processing somatosensory information (touch, position of limbs)
- sensory association area: next level processing of that sensory information
- start processing that's required for you to for example deduct that you're touching a smooth surface
366
occipital lobe function
- visual association area: allows higher level processing (recognizing what an object is for example)
- visual cortex: first area to receive visual information
367
temporal lobe function
- auditory cortex
| - auditory association cortex: "who does this voice belong to, what is it telling me"
368
the area of the brain that is found under the frontal and temporal lobes is used for what?
taste (gustatory cortex) and smell (olfactory cortex)
369
the left hemisphere of the brain is associated with that functions?
- speech center
- writing
- auditory cortex (right ear)
- general interpretive center (language, math)
- visual cortex (right visual field)
370
the right hemisphere of the brain is associated with which functions?
- analysis by touch
- auditory cortex (left ear)
- spatial visualization and analysis
- visual cortex (left visual field)
371
what is lateralization in the cortex
- right handed people have a left side that is usually dominant, opposite for lefties
- especially with respect to motor control, language
- 95% of right handed people have left Brocas & Wernicke area
- 70% of left handed people have the above in the right
372
Wernicke's area
- responsible for connecting words with meaning
| - critical for understanding spoken language
373
Broca's area
-responsible for articulation of speech, not comprehension
374
cerebrum: basal ganglia
ganglia are collections of cell bodies (nuclei)
| -there are several components of the basal ganglia
375
what are the components of the basal ganglia?
- components of the basal ganglia form a complex circuit between the motor cortex, premotor cortex, cerebellum, thalamus, and other areas
- loss of any parts of the basal ganglia is devastating
376
parkinson's disease is associated with which region of the brain?
loss of dopaminergic neurons in the basal ganglia
| -causes tremors, loss of ability to move, cognitive deficits
377
huntington's disease is associated with which region of the brain?
loss of chilinergic neurons in the basal ganglia (this activates neurons that are lost in Parkinson's disease
-causes disease of uncontrolable movements (chorea; chorea = dance, jerky motions), loss of coordination, dementia
378
cerebrum: limbic system
- the phylogenetically oldest part of the cerebrum
- includes amygdala, hippocampus, cingulate gyrus
- strongly connected with other areas, such as the thalamus, hypothalamus, and parts of the midbrain
- limbic system links higher processing with primitive emotions, such as fear, aggression, reward, social and sexual behaviour
379
lobotomy
- in the 1930's-40's, lobotomy was a treatment for moodiness, schizophrenia, depression, and criminal aggression
- in the 40's, the "icepick lobotomy" revolutionized psychiatry: surgery involved inserting a long sharp instrument above the eye and into the cranium to lesion prefrontal cortex
- 2/3 of patients either died, were paralyzed, or has near total loss of personality (ex: Rosemary Kennedy)
380
diseases and lesions of the CNS: loss of the hippocampus
- int he 1950's, H.M. was one of several patients who had parts of the temporal lobe removed to control epilepsy, experienced severe anterograde amnesia (long term memories are stored in the hippocampus, H.M. had both of his removed
- he could clearly recall of the events of his earlier life, but he was unable to for new memories for experiences that occured after the surgery
- but he was able to learn new motor skills
- motor skills are learned via the cerebellum
381
why do we have senses? what do they accomplish?
- information about the environment
- food, temp, osmolarity, potential mates
- information about ourselves
- energy stores, temp, water/ion balance
382
what are the 5 special senses (conscious)
- vision
- hearing
- taste
- smell
- balance
-senses that require another cell type or organ in order to accomplish the sense
383
what are the 5 somatic senses (somatosensory) (conscious)
- touch
- temp
- pain
- itch
- proprioception
-most of these are accomplished simply by nerve endings or nerve endings with some sort of connective tissue at the end
384
what are the 2 somatic stimuli senses (unconscious)
- muscle tension
| - proprioception
385
what are the 6 visceral senses (unconscious)
- blood pressure
- GI distension
- glucose
- osmolarity
- oxygen/CO2 content of blood
- many others
386
what are the 5 general properties of sensory systems?
1) receptors are most sensitive to certain forms of energy or stimuli (modality)
2) sensory transduction converts stimuli to graded potentials
3) sensory neurons have receptive fields
4) the CNS integrates sensory information
5) coding and processing distinguish stimulus properties
387
property #1 of sensory systems: receptors are sensitive to only certain kinds of energy/stimuli (modality)
the word receptor has two meanings in neuroscience
- a protein that binds a ligand
- a structure that detects sensory info
modalities detected by 'receptors'
- chemoreceptor (activated by oxygen)
- mechanoreceptor (activated by touch)
- thermoreceptor (activated by change in temperature)
- photoreceptor (activated by photons of light)
388
special senses neurons have a specialized ______ cell that forms a synapse with sensory neuron
transducer
389
property #2 of sensory systems: the receptors transduce the sensory signal into graded potentials
- the transduction process involves changes in membrane potential of sensory neurons
- activation or inactivation of ion channels
- ligand gated channels or channels modulated through second messenger pathways
changing ion channel activity int he sensory receptor causes a graded potential called the receptor potential
- the adequate stimulus is the preferred type of stimulus for a receptor
- the intensity of the stimulus is encoded by the magnitude of the graded potential produced
- the minimum stimulus to activate a receptor is the receptor threshold
amplitude of graded potential is translated to frequency of action potentials in higher order neurons
390
property #3 of the sensory systems: each neuron has a receptive field
- defined as a region of space in which the presence of a stimulus will alter the firing of a sensory neuron
- primary sensory neurons converge onto secondary neurons, allows summation
- the more convergence of primary sensory neurons onto secondary neurons the larger the receptive field and lower the acuity
391
______ creates large receptive fields and less acuity
convergence
392
two stimuli that fall within the same _______ field are perceived as a single point, because only one signal goes to the brain, therefore there is no two-point discrimination
secondary receptive
393
if we have a compass with points separated by 20mm touch the surface of the skin where 2 different sensory pathways are activated, as opposed to activating one pathway within this distance, we can say that _____ is high and there is much higher _____ in the first situation
convergence, acuity
394
the more an area is represented on a somatic map, the greater the what?
the greater the acuity, areas of high acuity represent less convergence
395
property #4 of the sensory systems: integration of the CNS
- some sensory info may be processed at the level of the spinal cord/brainstem
- directly to brain stem via cranial nerves
- visceral reflexes integrated in brain stem or spinal cord usually do not reach conscious perception
-some sensory info processed in the cortex
- perceptual threshold: level of stimulus necessary to be aware of a particular sensation
- a stimulus may activate a sensory neuron, but may not have enough intensity to surpass perceptual threshold
396
olfactory pathways from the nose project through the olfactory ______ to the olfactory______
bulb, cortex
397
most sensory pathways project to the ______, the ______ modifies and relays information to cortical centers
thalamus, thalamus
398
equilibrium pathways project primarily to the ______
cerebellum
399
which of the following sensory pathways do not synapse in the thalamus?
a) equilibrium pathway
b) sound pathway
c) visual pathway
a) equilibrium pathway
400
property #5 of the sensory systems: coding and processing distinguish stimulus properties
-remember that all stimuli are converted to action potentials. how does the CNS determine the properties of each stimulus?
properties of stimulus
- modality
- location
- lateral inhibitoin
- intensity and duration
coding
-refers tot he properties of the action potentials in sensory neurons
401
modality
-remember that receptors have a preferred type of stimulus or adequate stimulus
-specific groups of neurons within the brain a
re associated with specific modalities (this happens early in development)
-perception of a stimulus depends on the neural pathway that brings it to the CNS, not the receptor that transduced the signal: label line processing
-each modality has its own wiring system, from the receptor to higher processing centre
402
explain 'location' in terms of the properties of the stimulus are determined by coding and processing
- the location of a stimulus is determined by what receptive fields are activated
- stimulus from adjacent areas of the body are most often processed in adjacent areas of the brain (somatotopic maps)
- ex: sensory info from fingers are processed in adjacent areas in the brain
403
why would someone, after an amputation, experience phantom limb syndrome?
- this is because of the location that things are processed in the brain
- secondary neurons in the spinal cord (that innervated amputated limb) may activate cortical neurons that processed info from old limb
404
lateral inhibition
enhances contrast and makes a stimulus easier to perceive
-the response of primary sensory neurons A, B and C are proportional to the intensity of the stimulus in each receptor field. secondary sensory neuron B inhibits secondary neuron A and C, creating greater contrast between B and its neighbours
405
______ receptors are slowly adapting receptors that respond for the duration of a stimulus; ______ receptors rapidly adapt to a constant stimulus and turn off
tonic, phasic
406
glabrous skin
doesn't have hair
407
skin mechanoreceptors: bare nerve ending
have a number of functions, main function: detect temperature, various forms of pressure - not myelinated
408
skin mechanoreceptors: meissner's corpuscle
detects light fluttering or stroking of the skin (does not take much to activate) - encapsulated with connective tissue
409
skin mechanoreceptors: merkel disc receptor
detects steady pressure - gives information about textures
| -tonic receptor
410
skin mechanoreceptors: pacinian corpuscle
sensitive to low frequency stimulation (requires more pressure to activate because they're so deep)
- detects things like vibrations
- rapidly adapted phasic receptors
411
skin mechanoreceptors: ruffini ending
enlarged nerve endings
- detects stretch of skin
- useful because a lot of these are found around joints, can help tell if your arms is flexed or extended
- tonic receptor
412
______ receptors are ion channels
temperature
413
what activates warm receptors?
capsaicin
414
skin temperature receptors
- all found on free nerve endings
- more cold receptors than warm receptors
- cold receptors are activated below body temp
- warm receptors are activated from 37-45 degrees celsius
- pain (nociceptors) are activated above 45 degrees
415
nociceptors (pain receptors)
- bare nerve endings
- activated by strong noxious stimuli that may damage tissue
- may be activated by extreme temperature (painful hot, painful cold)
- arachidonic acid and prostaglandins may activate GPCR and cause graded potentials in nociceptive neurons
416
3 different types of axons (= fibres) that carry pain info
- medium diameter myelinated (A-beta) = fast pain
- small myelinated (A-delta) = fast pain
- small unmyelinated (C-fibres) = slow pain
417
sensory pathway for fine touch vibration proprioception
- position of limbs, stretch of skeletal muscle
- sensory neuron enters dorsal root ganglion, sends info into brain stem, projects to thalamus, thalamic neuron send axon to cortex - processing starts to occur
418
sensory pathway for nociception temp
- sensory neuron (body in dorsal root)
- first synapse happens in the grey matter of the spinal cord
- this neuron sends axons across to other side of spinal cord into ascending tracts
- makes its way to thalamus
- thalamus sends projection to cortex
419
name the 6 types of nerve fibres (axons), and their size, whether or not they're myelinated, and their function
- A-alpha, large, myelinated, motor neurons/ muscle stretch
- A-beta, medium, myelinated, cutaneous mechano
- A-gamma, medium, myelinated, motor neurons
- A-delta, medium, myelinated, cold nicoceptors
- B, medium, myelinated, autonomic
- C, small, unmyelinated, nociceptors
420
mechanisms that help protect eyes from injury
- eyeball is sheltered by bony socket in which it is positioned
- eyelids - act like shutters to protect eye from environmental hazards
- eyelashes - trap fine, airborn debris such as dust before it can fall into eye
- tears - continuously produced by lacrimal glands, lubricate, cleanse, bactericidal
421
structure of the eye
look at diagram
422
first tissue layer of the eye: sclera/cornea
- sclera: tough outer layer of connective tissue; forms visible white part of the eye
- cornea: anterior, transparent outer layer, allows passage of light rays
423
second tissue layer of the eye: choroid/ciliary body/ iris
- choroid: middle layer underneath sclera which contains blood vessels that nourish retina
- contains melanin
- choroid layer forms ciliary body, suspensory ligaments and iris
424
third tissue layer of the eye: retina
innermost layer under choroid
| -consists of: outer pigment cells; rods and cones; axons of visual nerve fibres
425
the interior part of the eye consists of 2 fluid filled cavities separated by the lens. what are they?
1) posterior cavity
- between lens and retina
- vitreous humor (gelatinous)
2) anterior cavity
- between cornea and lens
- aqueous humor (similar to normal extracellular fluid)
426
iris
controls the amount of light entering the eye
- contains two sets of smoother muscle:
- circular (= constrictor)
- redial (= dilator)
427
pupil
opening through which light enters the eye
428
lens
focuses light in the eye
429
tapetum lucidym
- manu vertebrates have less melanin, but an additional reflective layer within the choroid, called a tapetum lucidum (humans don't have this
- reflects light back towards the retina
- improves sensitivity of vision under low light, but may cause some blurriness
430
what's the purpose of dilating/constricting the pupil
-changing pupil size controls the amount of light entering the eye
- changing pupil size also controls "depth of field"
- a small aperture gives large depth of field
- a large aperture reduces depth of field
-close objects viewed with constricted pupils, so if object moves short distance, still in focus
431
pupil size is controlled by the _____ nervous system
autonomic
432
circular muscles in the eye are activated by _______, whereas radial muscles are activated by _____
acetylcholine, norepinephrine
433
the contraction of the circular muscles in the eye are from _____ stimulation, whereas the radial muscles dilate from ______ stimulation
parasympathetic, sympathetic
434
when light is coming from a distant source, light rays pass through a flattened lens, and the focal point falls where?
on the retina
435
when light is coming from a close object, the light rays are no longer parallel, the lens and its focal length have no changed, but the object is seen out of focus. why is this?
because the light beam is not focused on the retina
436
what does the lens do in order to keep an object in focus as it moves closer?
it becomes more rounded
437
what is accommodation
- process of focusing
- change in the strength of the lens
- fast: takes only 350 ms to change focus from far to near
- accomplished by the action of the autonomic nervous system on the ciliary muscle
- the natural shape of the lens is strong and rounded
- the ciliary muscle pulls the lens to a flatter, weaker shape when it relaxes
438
the main action of accomodatio is via ______ enervous system
parasympathetic
439
which neurotransmitter causes contraction of the ciliary muscle?
acetylcholine
440
sympathetic nervous system plays a major role in the contractio of the ciliary muscle
true or false?
false
441
myopia
- near-sightedness (can't see far away)
- occurs when the focal point falls in front of the retina
- can be corrected with concave lens
442
hyperopia
- far sightedness (can't see up close)
- occurs when the focal point falls behind the retina
- can be corrected with a convex lens
443
accommodation of the ageing eye
- lens is made of thousands of layers of cells
- during development, their nucleus is destroyed, and the cells become clear
- through their life they get nutrient supply from aqueous humor
- as you get older, cells die and lens becomes stiff
- the ability of the lens to be shaped is lose
-presbyopia = requires bifocals
444
rods and cones: compare the 2
rods:
- we have more of them
- grayscale vision
- slightly larger than cones
- high sensitivity (night vision, low acuity)
- more convergence onto ganglion cells
- mainly located in peripheral retina
Cones:
- fewer
- color vision (at least 3 varieties)
- lower sensitivity (high acuity, day vision)
- less convergence
- mainly located in fovea
445
what is the area in the eye that has the highest density of photoreceptors? this area has no major blood vessels running through it, making the image clearer
macula
446
at the ______ light strikes the photoreceptors directly, becuase overlying neurons are pushed aside
fovea
447
the highest density of cones is found at the _____
fovea
448
there is very _______ convergence of sensory neurons at the fovea
little
449
phototransduction: in darkness
- rhodopsin is inactive
- levels of cGMP are high - cGMP is a cyclic nucleotide, similar to cAMP; intracellular second messenger
- cyclic nucleotide gated (CNG) Na+/Ca++ channe;s and K+ channels are open - cMGP binds to channels and causes them to open
- cells are constantly depolarized by entry of Na+ and Ca++: they tonically release transmitter onto bipolar cells
-dark = more neurotransmitter
450
phototransduction: in the light
a) light bleaches rhodopsin and activates it
b) activated rhodopsin activates transducin (a G-protein)
c) transduction activates phosphodiestrase (PD), enzyme that degrades cGMP
d) the decrease in cGMP (the ligand) causes CNG channels to close, hyperpolarizing the cell
e) this causes less transmitter to be release onto bipolar cells
light means less neurotransmitter **
451
what is the information flow in a visual pathway?
- photoreceptors
- bipolar cells
- optic nerve (ganglion cells)
- optic chiasm
- optic tract
- thalamus
- optic radiation
- occipital lobe
452
what is the binocular zone?
area of overlap in our visual fields where both eyes perceive the same information, this gives us our 3D vision
453
most of our visual information goes to the ______ then back to the visual cortex, but some information goes to the _____ (from the thalamus)
thalamus, midbrain
454
amblyopia: "lazy eye"
- normal development of visual cortex relies on synchronous input from both eyes
- for young children with amblyopia, proper development of visual cortex will not occur
455
how can you correct lazy eye?
- treatment is often to simply patch the good eye, forcing the brain to use the information from the weaker eye
- strengthen inputs from the weak eye and proper visual cortex development
456
hearing
-our brain's perception of sound energy
457
sound transduction
defined as conversion of mechanical energy of sound waves to electrical energy
458
pitch
interpretation of frequency
459
what is loudness
our perception of intensity or amplitude of sound waves
460
why is sound important?
processing of sound can tell us abut distance, direction, and movement
461
sttructure of the ear
look at diagram
462
external ear
- pinna (=auricle) - elastic cartilage covered with skin
- external auditory canal (meatus)
- tympanic membrane (eardrum)
463
middle ear
- eustrachian tube (drains your pharynx)
| - ossicles (malleus = against tympanic membrane; incus; stapes = against oval window - inner ear)
464
what is the function of the ossicles?
these bones connect the movement of the tympanic membrane to the apparatus in your ear
465
inner ear
- bony labyrinth (tunnels in temporal bone) which surrounds and protects the membranous labyrinth
- membranous labyrinth fluid filled organ
a) cochlear duct with organ of corti (inside cochlea)
b) 3 semicircular ducts (=canals) with 1 crista ampullaris in each
c) utricle/saccule (inside vestibular apparatus) with 1 macula in each (macula= sensory organ)
466
explain the physiological process of hearing
1) sound waves strike the tympanic membrane and become vibrations
2) the sound wave energy is transferred to the 3 bones of the middle ear, which vibrate
3) the stapes is attached to the membrane of the oval window. Vibrations of the oval window crate fluid waves within the cochlea
4) the fluid waves push on the flexible membranes of the cochlear duct. Hair cells bend and ion channels open, creating an electrical signal that alters neurotransmitter release
5) neurotransmitter release onto sensory neurons creates action potentials that travel through the cochlear nerve to the brain
6) energy from the waves transfers across the cochlear duct into the tympanic duct and is dissipated back into the middle ear at the round window
467
cochlea
- each coil has 3 ducts (sometimes called channels)
- vestibular duct and tympanic duct contain perilymph (essentially extracellular fluid or plasma)
- cochlear duct contains endolymph (secreted by epithelial cells, very high [ ] of K+)
- vestibular membrane separates cohclear duct from vestibular duct; and basilar membrane separates cochlear duct from tympanic duct
- tectorial membrane is a flap which covers hair cells or organ of corti
468
explain the function of the cochlea in the process of hearing
Pressure wave in the ear gets transduced into a pressure wave in the fluid; moves the tectorial membrane
-hair cells are rubbed by tectorial membrane, causes opening and closing of ions channels, results in the release of neurotransmitter onto nerve fibers
469
at rest, about ___% of the ion channels of the hair cells in the cochlea are open, and a tonic signal is sent by the sensory neuron
10
470
endolymph has a high concentration of which molecule?
K+
471
hair cells have villi, or _______. the tallest is the ______. These are connected by ______.
stereocilia, kinocilium, tiplinks
472
which part of the hair cell contains very special K+ channel proteins that are mechanically gated?
stereocilium
473
hearing: excitation
- when the hair cells bend in one direction, the cell depolarizes, which increases action potential frequency in the associated sensory neuron
- when channels are open, K+ moves into cell and causes the release of more neurotransmitters
474
hearing: inhibition
if the hair cells bend in the opposite direction, ion channels close, the cell hyperpolarizes, and sensory neuron signaling decreases
-stops releasing neurotransmitter, neuron signalling decreases
475
the _____ membrane has variable sensitivity to sound wave frequency along its length. The stiff region (near round window) specializes in ____ frequency sounds anf the flexible region (near helicotrema) specializes in ____ frequency sounds
basilar, high, low
476
the frequency of sounds waves determines the displacement of the _______. the location of active hair cells creates a code that the brain translates as information about the pitch of sound
basilar membrane
477
auditory pathways
- primary sensory neurons send axons via nerve to medulla oblongata
- secondary sensory neurons from medulla synapse in midbrain and cerebellum, then thalamus and then project into the auditory cortex
- the auditory cortex receives signal from both left and right eats due to pathways crossing along medulla
478
what are the 3 types of hearing loss?
- conductive (happens within cochlea, happens as you age)
- sensorineural (loss of neural cells)
- central (loss of axons or cell bodies anywhere after cochlea)
479
equilibrium and the vestibular apparatus
- otolith organs in the vestibular apparatus (saccule and utricle can detect linear acceleration and head position)
- semicircular canals are sensitive to rotational acceleration
480
crista ampullaris (crista) in semicircular canals
- movement of the endolymph pushes on the gelatinous cupula and activates the hair cells
- provide information about rotation of the head (rotational acceleration)
481
macula in saccule and utricle
otoliths move in response to gravity or acceleration, gives information about linear acceleration and head position
-the otolith move with gravity to either open or close the channels, depolarizing or hyperpolarizing the cell
482
equilibrium pathway
hair cells synapse with neurons of the vestibular nerve. these synapse with cerebellum directly, or project to vestibular nucleus, then the midbrain, then the thalamus, then the cortex
-cerebellum and vestibular nuclei also project to areas controlling eye movement
