Physiology Notes 1/4/17 Anatomy vs. Physiology Physiology= study of function of living organisms i.e. how things work Anatomy= study of structure Form vs. function Constantly changing and influencing each other How might that happen? In many cases something's structure is related to its ability to function like red blood cells being flat and concave to allow for greater surface area for oxygen to attach to the iron on hemoglobin. Function of_ is due to its structure Levels or Methods of Study: (5) Cell Physiology (cytology): study of function of cells. Cells have their own particular functions in the body. Foundation for understanding larger processes like nervous system What happens to the cell happens to the bigger organism. Histology: study of body's tissues (groups of similar cells with a common function)
Don't forget about the age old question of What impact did the printing press have on the early modern west?
Organ physiology: study of function of two or more tissues that work together to perform a simple or complex function in the body; like the small intestine
System physiology: study of functions of groups of organs that work together to perform a complex function in the body
How our class is organized Organism physiology: study of function organ systems that interact to keep an organism alive Need to decompartmentalize; Interactions between the systems Basic Needs/ Functions of human Body (7) Functions: Maintaining boundaries; inside vs. outside; necessary to perform functions Movement-contractions and releases; movement in or out of a cell or within the body Responsiveness- ability of a cell to adjust to changes in its internal or external environment i.e. nervous system
We also discuss several other topics like What is the attitude accessibility theory?
Obtaining nutrients and oxygen- digestive system brings nutrients into the body and respiratory system
Metabolism- breakdown of food and energy; we will cover mainly the skeletal muscle aspect
Excretion: renal system, kidneys, remove waste
Reproduction: formation of new humans from parents; we will cover this on an organism level; male vs. female not the cell stuff
Don't forget about the age old question of What is the function of the amygdala?
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Nutrients, oxygen, water and the right temperature
Ability of the body to maintain stable internal conditions
Equilibrium or balance
3 fluid compartments:
1. Intracellular fluid-fluid within the cell makes up the most fluid in the body aka cytosol 2. Interstitial fluid- immediately surrounding cell; cell's “environment” 3. Plasma- liquid portion of blood
Interstitial and plasma together make up extracellular fluid because they are outside the cell If you want to learn more check out How are drugs excreted from the body?
I have needs because my individual cells have needs for oxygen, food, etc.
I must get my needs met from my environment (the fridge) so that the cell can get its needs met through its environment (digestive, cardiovascular system)
Cells make proteins to move around the body, etc. and make up body systems. They all work together. We also discuss several other topics like What is the first step in the scientific method?
Negative Feedback Mechanism Output of mechanism causes variable to change in a direction opposite of the initial change How we regulate the variables that an organism needs to live
Ex: room temperature. When the temperature drops the thermostat brings it back up to where it needs to be. Like blood pressure.
Positive Feedback Mechanism
Output of mechanism enhances the original stimulus
Fewer in the body
If it increases, it will keep increasing to a big event that will reset the whole system Example is labor: baby stretches the uterus. In response to the increased pressure the body releases oxytocin which creates more pressure and more contractions which eventually pushes the baby out. If you want to learn more check out Explain the line, "what does rough winds do shake the darling buds of may mean" from shakespeare's sonnet.
When a control mechanism fails
Initial problem is too much (not enough diet, exercise, etc.) so blood pressure will stay too high or out of balance
Physiology Notes 1/6/17 Generic Neuron = nerve cell (single cell) Neurons come in all different shapes and sizes but this is a generic one
Cell body is the soma; it has a nucleus, lysosomes, all the same contents of a normal cell.
Dendrites are the extensions of the cell body that receive signals from the environment and other cells; adds surface area
Communication of a cell is always only one direction Axon is the middle tube and axon terminal terminal is the end (output of cell signal) Schwann cells are cells wrapped around the axon that form myelin sheaths Myelin sheaths are on many cells but not all
They flatten their cytoplasm like a rubber band and wrap around the axon to form membrane layers that provide:
I do not conduct electrichy Carry electar -Insulation
- signals away from neuron 1. Protects the axon from damage
2. helps speed up signals down the axon which is called saltatory conduction. Multiple sclerosis destroys these myelin sheaths Nodes of Ranvier are gaps in the myelin sheath between adjacent Schwann cells Neuron vs. Nerve: difference A neuron is a single cell and is not visible A nerve is a ton of neurons all bundled together and it is visible; they are all bundled to provide a sort of map and sense of organization in the body Synaptic knob- a knob at the terminal end of the nerve that is next to the synapse. When the nerve impulse reaches it releases a neurotransmitter across the synapse which binds to the receptors of the next cell and initiates a new signal. from Synaptic vessicles Synaptic vesicles store the neurotransmitters and release them into the synapse to send signals between neurons. The release is regulated by a calcium voltage channel. they are constantly being recreated by the cell.
Neurotransmitters-chemicals that relay messenges across a synapse from one neuron to another
Membrane potential is also electrical potential (+/- like a battery) Common to ALL cells in the body but to nerve cells in particular
Potential means the difference of one side of the membrane compared to the other (inside vs. outside)
1. Always relative (even if there is no change)
Inside of a room could have a light on and still be considered dark compared to the outside
2. Refers to how the inside of the membrane compares to the outside of the membrane
The inside could be negative (and usually is) compared to the outside even if it only means there are fewer positive charges inside than there is outside
Measured in millivolts (mV) and a generic nerve cell has a membrane potential of -70mV
There are 2 Factors and 3 Players:
1. Membranes are selectively permeable (permeable meaning how easy it is for
something to slip through the membrane) 2. Sodium-potassium pump
There is a specific protein in the cell membrane that requires 1 ATP to exchange 3 Na ions out and 2 K ions in the cell (active transport). Its aim is to have lots of potassium and low concentration of sodium inside the cell for various bio processes
inside . (high concentration outside) It is constantly working but it can work overtime if there is lots of sodium inside.
1. Negatively charged molecules (can include a variety: organic, inorganic, proteins,
amino acids, ATP, etc.)
Not permeable because they are too big and are charged so they are stuck inside the cell
2. Sodium ions
Found everywhere in all types of cell fluid
High sodium concentration outside the cell because of the Na/K pump
Not permeable because of their charge (but if they were permeable would go in the cell b/c they move from high to low concentration down the concentration gradient)
need help to enter
Specific gated channels
3. Potassium ions
takes A TP to
High concentration inside the cell (Na/K pump)
Arush sodium out of - the cell but
Somewhat permeable because there are specific potassium protein channels called leak channels that are always open; they can go out by going down the concentration gradient; some but not a ton get out
There is always some sodium inside and some potassium outside. (This process slows down when the concentrations get too low)
Membrane potential is 0 when there is no difference between the inside and
outside of the cell
A flat line is resting membrane potential
The cell is polarized when one side is more positive or negative than the other
C at rest the cenas polarized Hyperpolarization- when the membrane potential (inside the cell) becomes more Restina Potential negative (graph moves down)
Out This is still considered an increase in membrane potential because it is a
difference between the two sides
-sodium levels increase outside the cell (so the inside becomes more negative) - more negative ions inside the cell -potassium moves outside the cell
Depolarization- when membrane potential (inside the cell) becomes more positive (graph moves up)
-potassium levels increase inside the cell -less sodium outside the cell -channel lets sodium inside the cell
Excitable tissue: nerve and muscle cells
Meaning they are designed to purposely change their membrane potential (this is how they generate electrical signals)
Nerve cells have gated channels which let them move ions around because they can open or close in response to different things
4 types of Gated Channels:
1. Chemically gated (ligand)
Usually closed at rest There is some spot there some chemical (ligand) is designed to bind which causes the gate to open and close once it is removed
2. Voltage gated
Opens or closes when the membrane potential changes Depends on if membrane potential goes up or down
3. Thermal gated
Changes with temperature
4. Mechanically gated
Responds to a when a cell membrane is physically being moved Think of pushing on a balloon and how it dimples
I feel things because there are nerve cells on my skin with mechanically gated channels that change membrane potential and send signals to my brain letting me know I've been touched.
Physiology Notes 1/9/17
Synapse is where one neuron communicates with another neuron Presynaptic cell- innervates/synapses with the next cell in 1 direction Post-synaptic cell- receives the signal Neural cells don't touch Voltage gated calcium channels allow calcium to pass through when the membrane potential changes.
Calcium is always in a high concentration outside the cell because it's very powerful inside the cell.
What are synaptic vesicles?
Membrane pockets inside the cell in the axon terminal. They are filled with neurotransmitter, a generic chemical (or ligand) that acts as a chemical messenger. Where are chemically-gated channels located?
There are sodium-specific and potassium-specific channels located only at the synapse in the nervous system underneath the presynaptic axon terminal in the synaptic gutter or cleft. (cell communication happens other places in the body like in glands and such but the synapse is the only place where membrane potential changes in the nervous system).
Where are the voltage-gated channels?
They are located everywhere else on the cell membrane except the synapse. These voltage-gated sodium-potassium channels have more sodium and potassium channels.
What is action potential? Signals that neurons generate
It is the opposite of resting potential; it controls all things we can make our body do consciously or unconsciously
It is a change in membrane potential. (How cell membrane A generates action potential on cell membrane B.) Originally cells get action potential from the environment but it is then passed along cell to cell in one direction. How does action potential work in nervous tissue?
1. Resting membrane potential membrane is polarized 2. Action potential reaches the axon terminal of the presynaptic neuron
-voltage-gated calcium channels open so calcium rushes into the cell -neurotransmitter released into the synaptic cleft -Neurotransmitter binds to the receptors on the channels of the postsynaptic membrane
chemical - sodium ion channels open (they are fast to open and fast to close) - sodium ion rushes in causing the membrane to depolarize 3. If the threshold is reached then the voltage-gated sodium ion channels open
-tons of sodium enters the cell. This is the depolarization phase. 4. sodium ion channels close and the potassium channels open (can't have both open at once)
5. tons of potassium ion rushes out of the cell. Repolarization phase.
6. potassium channels remain open longer (slow to open and slow to close)
-excess potassium ions leave the cell; hyperpolarization phase 7. The sodium potassium pump brings the ion concentration back to the normal resting state.
This entire process takes 3 milliseconds!
How does anatomy explain whợ'action potential is one direction?
There are chemically gated channels only at the synapse and the signal must generate along the axon terminal from the dendrites.
What are some properties of action potential?
What is that?
The amount of stimulus (neurotransmitter) released that is necessary to open voltage gated channels. -55mV
What is meant by the all in the all or none response?
It doesn't matter if “just enough” stimulus is present to just barely create the response (to open all the channels) or if you provide ten times as much stimulus; the resulting action potential is the same.
What does it imply?
The action potential for any one neuron is exactly the same. You can't tell the intensity of a stimulus from its action potential.
What happens if the stimulus is below the threshold?
There is still a change in membrane potential but the action potential stays in the synaptic cleft and dies out before going anywhere else.
2. Impulse propagation
How action potential travels down the cell from synapse to axon terminal
What are the two kinds of propagation for a neuron?
1. Transitory (local) current
The signals open up channels sequentially like a domino effect
2. Salutatory conduction
For myelinated axons these insulated areas on the axon from the Schwann cells
notace don't have ion channels because they are covered by the myelin sheath causing the positive charge to be further out and not as negative. Thus when sodium ions enter they are able to move along the axon much more quickly (because there isn't as much negative charge to hinder it)
Pre-synaptic cell .. [cate]
Symaptic cleft DAL Post asynaptic cell
study so channels
Physiology Notes 1/11/17
Saltatory conduction speeds up depolarization and the signal 3. Graded potentials Csee notes on 1/13/17
Presynaptic neuron releases neurotransmitter so some sodium enters the cell but not enough to reach threshold. Then potassium opens.
In what two ways are graded potentials different than action potentials?
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Unlike action potential graded potentials can be in different sizes/ intensities. Also no hyperpolarization happens (it does in action potentials because it is caused by potassium channel staying open too long).
Happens only at the synapse; no traveling to other parts of the neuron because the signal dies.
at Synapse An example of chemically gated channels being most necessary to repolarize the membrane. Voltage gated channels are key in action potential. Voltage gated
Graded potentials are added to get greater amount of product
1. Temporal summation
Increase the frequency of stimulation from 1 synaptic neuron (A sends signal to B at a faster and faster rate)
Method of getting a graded potential from Multiple signals from one neuron over time
Related to time; if time is long enough and frequency of increase in potential is enough then 1 rise starts before the other one ends
Can possibly reach threshold but not always
Example: it takes not 1 drop of water on your head to fix the faucet but 20 or more. Also with vision, if enough time elapses and enough frequency of flashes of light the more likely you are to be able to see the visual stimuli.
2. Spatial summation
Method of getting a graded potential from Multiple signals from multiple neurons at the same time
Summation=always talking about graded potentials
Multiple presynaptic inputs sum their graded potentials together
Each individual neuron has its own graded potential but because they are transmitting their signals from different locations to the same space at the same time their potentials are summed. Not mutually exclusive. Can be a temporal summation followed by a spatial summation (can get both).
Only actually see the sum effect.
5. Types of Synapses
1. Excitatory synapse
The kind we have discussed with a neurotransmitter sent from presynaptic neuron to receptors and channels on postsynaptic cell
Causes an increase in sodium permeability (opens sodium channels)
Causes depolarization (toward the threshold); can be graded or action potential as long as it moves toward the threshold
Called an excitatory post synaptic potential or EPSP
2. Inhibitory synapse
Makes a postsynaptic neuron less likely to generate a graded or action potential
Takes membrane potential further away from the threshold so it's harder to get an action potential
Combination of neurons being released and receptors binding which causes an increase in potassium permeability (more potassium can go outside the cell)
Sometimes increased permeability for chloride ions; chlorine goes where the sodium does to make NaCl
"inhibitory post synaptic potential” or IPSP
What two factors determine what type of synapse will exist?
Depends on what neurotransmitters and what receptors are being used
Example: neurons stimulate muscles in the biceps and inhibit muscles in the triceps. Happens at same time
Inhibitory synapses can help with ability to focus by reducing stimuli
How many types of neurotransmitters can a neuron release?
Each neuron can release only one type of neurotransmitter. The receptors can also only be one type. Synapses also can't change. They are specialized. Always excitatory (+) or always inhibitory (-).
Can you have summation with inhibitory responses?
Yes! Or with temporal or spatial.
If you fire an equal amount of excitatory and inhibitory responses what will happen?
They cancel each other out and no response.
Why can one neurotransmitter do lots of different things?
Acetylcholine can simultaneously stimulate digestion and slow heart rate. There can be tons of synapses on a single neuron and even though each synapse has one neurotransmitter there are different receptors that cause different results (like acetylcholine).
6. Refractory Period
During and after action potential when another action potential cannot occur on the postsynaptic
The dy sou
Absolute refractory period: Generally, starts at the crest of the membrane potential l when the sodium channels close and the potassium channel opens. Ends when the membrane potential reaches resting.
closing Na nel responsible no excitation allowed in absolute refractory Relative refractory period:
- When sodium channel resets Cresting -70) End of the absolute refractory period. Starts at the resting membrane potential and ends after hyperpolarization when the membrane potential reaches resting again.
. neuron can only be excited by a larger than normal stimulus during What causes these refractory periods? relative refractory perioda this is bic of the
I resetting sodlum channels The sodium and potassium channels. It is their structure that influences it (how they open and close)
A (resting potential): sodium ion channels have one gate open (chemical) and one gate closed(voltage). The voltage gate opens when threshold is reached.
B rising potential: More and more voltage gates open allowing more sodium in. Potass open yet.
C peak of potential: sodium ion channel gates close. They are locked until the cell repolarizes. Potassium channel gate opens. It's the chemical gate. The cell potential decreases
D: The sodium channels reset when the membrane potential reaches -70. The potassium channel is still open because it is slow to close. Hyperpolarization. The cell potential can't depolarize to resting so it requires a larger than normal stimulus to get back to resting potential.
Why is a refractory period necessary? butter to bowls
WWave of repearaattia It insures the action potential travels only one way and doesn't reverb. W hent
tant fer 7. Neural wiring
1. Cclosed channels
- the refularentin Convergence- many presynaptic inputs to 1 postsynaptic cell
To combine signals
- from behind
Divergence- one presynaptic cell synapsing with multiple post synaptic cells
To amplify signals
Tocked sodium channels potass unchannels open evol
sodium / Voltage gate
Physiology Notes 1/13/17
Why do thicker neurons conduct signals more quickly?
There is more surface area on thicker neurons so there are more sodium channels. This allows depolarization to happen more quickly.
How does a decrease in temperature slow down speed of signal transmission?
Simple diffusion. Temperature affects the rate which sodium diffuses into the cell. Higher temperature makes it diffuse faster.
Compare and Contrast Graded potential and action potential:
Graded potentials can be depolarizing or hyperpolarizing depending on the type of synapse. Action potential always starts with depolarizing and ends with hyperpolarization at the end (both are involved).
Action potential is all or none there is no intensity for the stimulus. Graded potential has an amplitude proportional to the strength of the stimulus
Action potential relies only on voltage-gated potassium and sodium channels (not chemical) whereas graded potentials use lots of different kinds of channels (chemically-gated is the main difference because it is what is needed to repolarize the membrane) Action potential uses just sodium and potassium ions but graded potential uses sodium, potassium and chlorine
Action potentials have a refractory period graded potentials do not Graded potentials can be summed over time and action potentials cannot (all or none) Graded potentials can passively spread to neighbors on the membrane but action potentials have to generate a new action potential every time they spread Amplitude diminishes along the way for graded potentials. It does not diminish for action potential.
Graded potentials are lead to the depolarization to threshold in an action potential (the start of every action potential is graded. Graded potentials are started by a neurotransmitter or an external stimulus (from a sensory neuron). Graded potentials for neurons occur only in synapses in lots of different tissues (the post-synaptic cell) because their signal dies (doesn't reach sodium and potassium voltage gated channels though calcium voltage-gated channels are still involved). Action potentials occur in excitable tissues (nervous system and muscular system) where there are large concentrations of voltage-gated potassium and sodium channels
Excitatory and inhibitory describe graded potentials that make an action potential more or less likely (excitatory or inhibitory postsynaptic potential IPSP or EPSP). What happens if EPSP isn't large enough to trigger an action potential? Repolarizes back to resting potential
Sensory Neurons also called afferent neurons
Nerve cell that Send signals from external environment to the central nervous system (brain) which generates internal electrical impulses. Cell body is outside the brain and the axon terminal is inside the brain
Nerve cell that is completely inside the central nervous system; information processing with impulses from sensory neurons to motor neurons. Very complicated wiring; divergence and convergence of signals is what is complex.
Motor neurons also called efferent neurons
Nerve cell that sends signals from the central nervous system to muscles or glands. Makes the body do an action
Cell body inside the central nervous system axon terminal outside the brain
Everything you do always starts from a sensory input. We can't just "decide” something. Involuntary movements like twitching are caused by an imbalance of some kind.
Parts of the Nervous System:
Central nervous system: includes the brain and spinal cord with all of their interneurons
Peripheral nervous system: all nerves in the body carrying axons and nervous tissue outside of the central nervous system.
What are the two divisions of the peripheral nervous system?
Afferent and efferent
Afferent (sensory) division
Includes all the nerves sending information to the central nervous system Has two divisions sending different types of signals from different locations
1. Somatic afferent division
Sensory neurons scattered around the body that respond to stimuli from the environment. Includes pain, touch, cold, sight, hearing, taste and all senses that one is consciously aware of. I will be aware of somatic afferent signals so long as the stimulus is large enough to generate an action potential.
2. Visceral afferent division
Specialized neurons that monitor the internal environment of the body and detect deficiencies in nutrients or blood pressure (but not necessarily hunger). Visceral afferent neurons don't send signals I consciously perceive because these signals are sent to different areas of the brain.
What is the one exception to the visceral afferent division not detecting sensation?
The wiring for pain signals of the visceral afferent division is different such that one can be aware of them.
Efferent (motor) division
Nerves that transmit impulses from the central nervous system to glands and muscles based on need. These are neurons that make the body do something.
1. Somatic efferent division
Neurons that are in charge of voluntary control of skeletal muscles
2. Autonomic nervous system (it's such a big division it's a system)
Neurons that control all internal organs to maintain homeostasis; all involuntary
1. Sympathetic nervous system
“fight or flight” response; designed to get the body ready for action
Parasympathetic nervous system “rest and digest” response; maintaining normal upkeep of the body at rest. An example is sitting in class.
These two systems are counter regulatory meaning they can be simultaneous (like in anxiety) but work against each other. Whichever one wins gets the response.
Example: the sympathetic nervous system overrides the parasympathetic when the fire alarm goes off. Once you realize there is no danger the parasympathetic takes over again.