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Peripheral Nervous System
Everything but the brain and spinal cord
Central Nervous System
The spinal cord and brain
Conscious sense or movement. Involves the peripheral and CNS.
Special Senses
Centralized area of detection. Ex: ears and eyes and nose
In the gut. Controls mainly nonvoluntary functions in the stomach, bladder, and intestines. May also affect glands, heart rate, hormones, and blood pressure to some degree.
"brain of the gut" Entric plexuses (nerve network). Controls many nonvoluntary GI funtions.
Transmits electrical signals. All are one directional. Can be up to one meter long. Longer cells allow faster transmission. Synapses slow the action potential. Goal is to receive the action potential, make a decision, and send action potential.
Cell body of a neuron
projections that receive action potentials.
Axon Hillock
Starts new Action potentials
Transmits signals
Where the axon connects to dendrites from another neuron.
Nissl Body
Replaces the golgi body in neurons. Specialized to produce neurotransmitters, which are chemicals in synapses.
Myelin Sheath
Insulates some neurons. Allows for faster transmission of signals and less interference of outside information. Forms myelin rings and has white color. Allows for saltitory conduction.
Saltitory conduction
when the signal jumps from one myelin node to another instead of creeping along. Transmits signals much faster by skipping the space between them .
White Matter on neurons
Transmitting center that only surrounds axons
Grey Matter
Somas for processing information.
Sensory Neurons
Special dendrites for environment stimulus.
Motor Neurons
Dendrites connect to a muscle fiber instead of other neurons.
Support Cells (Glia)
These are part of the N.S., but don't tranfer any information. They may play a role in immune functions, build myelin sheaths, and clean up old neurotransmitters. Include oligodendrocytes and schwann cells.
Only in the central nervous system and produce a myelin sheath from wrapping of plasma membranes. 20% protein and 80% lipids (white).
Schwann cells
Produce myelin sheath in PNS.
Responsible for the blood/brain barrier. Keep pathogens out of the central nervous system. Seperates cerebral spinal fluid and blood. General support and housekeeping...
Action Potentials
Caused by a different ion concentration across the cell membrane. The membrane has ion channels and pumps that are selectively permeable to K and Na. Usually positive inside the cell and negative outside.
Resting potential
Na/K pumps maintain the resting potential, which is about -70 mv. The membrane potential of a neuron the is not transmitting signals.
Characteristics of action potential
All or none. Irreversible due to hyperpolarization. Non-decremental- same at the beginning and end.
Mechanical or Stretched-gated ion cells
Ex: Hair cells, cells that sense stretch and open when the membrane is mechanically deformed.
Ligand-gated ion channels
Open in response to chemical signals.
Voltage-gated ion channels
Open when membrane is depolarized.
The role of Voltage-gated ion channels in the generation of action potential
If a stimulus is strong enough it passes the threshold. The sodium channels then open to start the action potential. After the signal has fired, the sodium channels close and the potassium channels open. Positive ions flow in the opposite direction to repolarize the cell. Then hyperpolarization occurs which signals the potassium channels to close. Then the Na/K pumps restabilize the voltage to reach resting potential.
Multipolar Neurons
Have multiple dendrites and axon terminals. They can receive stimuli from multiple neurons and send info to multiple neurons. This is the most common form.
Bipolar Neurons
Only have one dendrite system. Much simpler. Sensory systems.
Have dendrites and axons, but the cell body is often to the side.
Chemical Synapse
Calcium flows in and stimulates vesicles with neurotransmitters to be released into the synapse. Then the neurotransmitters enter the ligand-gated channel and starts depolarization. The amount of neurotransmitters controls whether and AP occurs.
Excitatory Postsynaptic Potential
Depolarizations that bring the membrane potential closer to the threshold.
Inhibitory Postsynaptic Potentials
Hyperpolarizations that move the membrane potential farther from the threshold.
Excitatory Neurotransmitter. In both PNS and CNS. Nicotine interacts with Acet.
Can be either excitatory or inhibitory. CNS and PNS.
Generally excitatory but can be inhibitory, CNS and PNS.
Inhibitory, CNS.
Spatial Summation
Excitatory potentials produced simultaneously by different synapses that add together.
Temporal Summation
Two excitatory potentials occur in rapid succession at a single synapse, and the second may begin before the first has returned to the resting potential. These add together for temporal.
Neural Circuit Amplification
1 stimulus goes to three neurons, then four. This is important if the information needs to go to multiple places.
Neural Circuit reduction or summation
Multiple inputs then sent to fewer neurons. 4 stimuli sent to three neurons, then two, then one. Ex: nonspecific touch, like of the back of the neck.
Neural Circuit Storage or reverberating
Stimulus keeps going to neurons in a circle over and over.
Doesn't work through storage in particular cells. It is a pathway through a group of cells. Stimulating a circuit makes it more efficient.
Synaptic Plasticity
New synapses form into unique pathways. Long term memory has physical changes.
Synaptic Potentiation
A synapse get more efficient with use because it accumulates Ca , calcium accumulates around the synapse, allowing it to work faster and better.
Spinal Reflex
If you stick a tack in your thumb, it stimulates general receptors. Which starts an action potential that goes through the nerves to the spine. A decision is then made in the spine to withdraw hand. The signal is sent out to motor nerves, which stimulate the muscle fibers and you remove your hand. Some stimulus goes to the brain, so that you are consciously aware of the pain.
At the base of the brain, and in charge of coordination. Helps conscious perception match actual movement. It receives signals from muscles and joints to know what thebody looks like at all times. It also get information on what movement the brain wants. Itthen send excitatory or inhibitory info to correct or refine the movements. If you practice a movement, you get better at it because the pathways become more efficient.
The lower part of the brain where it connects to the spinal cord. Controls vital functions including heart rate and respiratory functions. It also relays information. Includes the pons, medulla oblongata, and midbrain.
Controls most higher thought and action.
Temperature control, biological clock, hunger, thirst. Just above the brainstem.
Visual reflexes. Farther down in the brain. As you go up, the more vital functions they perform.
Visual Association
In the back of the brain. Processes visual information.
Auditory Association Areas
Just before visual.
Speech Areas
Controls vocab. and how you put sentences together. Does not control movement of mouth.
Pre and Post central Gyrus and central Sulcus
Sulcus-runs left to right down the middle of the brain, indentation. Gyrus- bump. Precentral Gyrus- Controls all conscious movement. Postcentral- primary sensory reception.
Left side of gyrus. We can map specific regions to part of post-central gyrus.
Sensory/motor homonclus
Old idea that tiny people were contained in cells and controlling things.
Compound eyes
They have multiple lenses, example is insects.
In compound eyes, segment with own field of view. Has 6-8 receptors. The visual center of then brain recieves a mosaic image then the brain peices it together into a full image.
Single Lens
One lens. A single image is focused onto a bed of many photoreceptors. They then send signals to the visual center of the brain to process the information. Single lens eyes evolved at least twice. Cephalopods eyes evolved separately from ours.
Hypothesis of how eye formed
There was a layer of skin with pigment cells and nerve fibers responding to whether it is light or dark. Then there was a mutation or an indentation of skin layer. This allowed for determination of the direction light is coming from. This then filled in with water. this allows light to be refracted and picked up different kinds of light.
Controls light input by changing diameter.
The opening in the middle of the iris.
Convers the opening into the eye. clear skin layer derived from the epithelium. Everything behind the cornea is fluid filled.
Crystalline structure. Ligaments attach it to small muscles (cilliary bodies) that allow you to focus on things.
Fovea Centralis
Has the highest concentration of color receptors. Located in the middle of the retina. This is where we have the greatest visual activity. Outside of this there is a mixture of both rods and cones.
Optic nerve
Where nerve fibers are concentrated.
Optic disk
Where optic nerve connects to retina. No photoreceptors there. Called the blind spot. The brain fills in the image with what is thinks should be there.
Multiple layers. Has epithelial layers. Layer of nerve networks that play a part in processing images. Behind the nerves are rods and cones. Light hits photoreceptors and causes depolarization of nerve cell. This generates an action potential that travels out to nervous tissues. If light misses the photoreceptors it is stopped and absorbed. Light may get blocked by blood vessels, nerve cells, and epithelial tissues before reaching photoreceptors. Nerves from many rods are connected to one nerve (summation). Cones do not have summation. The dark pigmented tissue behind the retina absorbs extra light to reduce scatter and noise.
Tepetum Luadium
Reflective layer behind the retina. (cats-eyes glowing) Light comes in and has one chance to hit photoreceptors. If it doesn't, light bounces back for a second chance to hit photoreceptors. If it doesn't hit one this time it is reflected out of the eye. This is why some animals' eyes' glow. This causes a lot of noise and scatter, so there is a less accurate image, but they have twice the ability to detect low light.
Rods have photopigment rhodopsin, which shrinks and gets bleached when light hits it. When it shrinks, it opens ion channels which starts and action potential. Signals are always sent in the dark. This is called the dark current, which stops when rhodopsin shrinks. Dark currents release glutamic acid, which is an inhibitory neurotransmitter. This keeps bipolar neurons from firing. When the dark current stops, ion channels open and the bipolar cells fire. It takes up to ten minutes to go from bleached to unbleached. Cones recover from bleaching very fast, but need more light for stimulus.
Non-specific Immune System
General defenses against unknowns. Always there whether or not bad things are in the area. Includes internal and external.
External Non-specific defenses
Skin-barrier. Mucous membranes- on parts of the body where you can't have thick skin because you have to diffuse things. Mucous traps invaders and has anti-microbial properties. Ex: eyes and mouth. Secretions- Tears and earwax. STomach acid- very acidic. Destroys bacteria on food. Production of these may increase when you are sick.
Internal Non-specific defenses
These are there in case external defenses are breached. Phagocytic cells- white blood cells, neutrophils, and macrophages. Destory any foreign cells. Lysozymes- destructive enzymes that break down foreign cells. Mast cells and blood. The lymphatic system (inflammatory response).
Mast Cells
Are a internal non-specific response. They release histamine, which sinals the body that there is a problem in that region. May cause vasodialation, swelling of the blood vessels, which results in more heat, redness, and swelling. This draw phagocytic cells to the area. They squeeze between the cell junctions and go to area with inflammation. They then eat the foreign cells and more plasma goes to the area (lymph) which contains clotting elements. This may cause pus,, which is a lot of phagocytic cells, in the area.
Lymphatic System
Continually circulates lymph throughout the body. While blood is in the capillaries, plasma leaks out and surrounds the tissues. The blood eventually makes its way back to the lymphatic vessels. These carry the plasma to a lymph node, which then empties it back into the circulatory system.
Lymph Nodes
These are the area for the central response for specific immunity. Bacteria spread via the lymphatic system and eventually end up in lymph nodes. A specific response is there waiting to destroy them. Lymph nodes swell when you are sick because there is an accumulation of immune cells in them.
Specific Immune System
Targeted at one specific antigen.
Any foreign protein that triggers a specific response.
Specific receptor or binding site for a specific antigen. One B or T cell can only recognize one type of antigen, but it may have multiple receptors of the same type on each cell. A person may have as many as 100,000 different types of receptors in their body.
What happens when an invader gets in?
Once infected, the invader binds to a specific B or T cell. This activates the cell like a lock and key system. This activated cell signals the immune system that that particular type of antigen is in the system. The body then forms a specific response to the infection.
B cell
These are sometimes called plasma cells. Once activated, it clones itself in order to form memory B cells and plasma cells. The plasma cells produce tons of antibodie, which bind to antigens (agglutination). This disables the pathogen by sticking to it. Antibodies may also flag a cell for destruction by phagocytes, which is a non-specific response. The memory B cells that were formed go dormant and remain in the body, waiting for the return of the pathogen.
T cells
Sometimes called cytotoxic or killer cells. These perform cell to cell combat. When a dormant T cell is activated, it produces memory T cells and cytotoxic cells (a T-helper cell often activates B cells). The cytotoxic cells then destroy other cells, maybe even your own if they are flagged. Your cells get tricked by the virus into producing more viruses. This causes your cell to put out a flag. Cytotoxic cells then destroy your infected cell. It may do this by using perferin- punches in the cell membrane. The flag may activate a T-cell, which activates if to form killer T cells. Helper T cells then activate B cells.
Attempt to induce a specific response without the full infection. Most vaccines are virus parts or disabled bacteria. Many are just weakened viruses, not dead viruses.

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