The nervous system includes allthe nervous tissue in the body + the sensory organs (such as the eyes and ears).
Nervous tissue is composed of 2 kinds of cells:
neurons which transmit nervous system messages
glial cells which support neurons and modify their signaling.
There are 2 major divisions of the human nervous system:
the central nervous system (CNS) which consists of the brain and spinal cord
the peripheral nervous system (PNS) which includes all the neural tissue outside the CNS plus the sensory organs.
The PNS has 2 divisions:
afferent division which brings sensory information to the CNS
efferent division which carries action (motor) commands away from the CNS to the body’s ‘effectors’ (muscles and glands).
Within the PNS’s efferent division are 2 subsystems:
the somatic nervous system which provides voluntarycontrol over skeletal muscles.
the autonomic nervous system which provides involuntary regulation of smooth muscle, cardiac muscle and glands.
The autonomic system is further divided into:
sympathetic division (or 'fight or flight’ response) which generally has stimulatory effects (like adrenaline).
parasympathetic division (or 'rest and digest’) which generally facilitates routine maintenance activities (like digestion).
There are 3 types of neurons (cells):
sensory neurons. Sensory neurons sense conditions both inside and outside the body. They convey information relating to said conditions to neurons inside the CNS.
interneurons. Interneurons are located entirely within the CNS and interconnect other neurons.
motor neurons. Motor neuronscarry instructions from the CNS to effectors (e.g. muscles or glands).
Each neuron has multipledendrites (through which signals travel to the neuron cell body) and a singleaxon (that carries signals away from the cell body to the synaptic terminals).
Glial cells produce the fat-richmyelin, which can surround neural axons and increase the speed of neural signals.
A nerve is a bundle of axons in the PNS that transmits information to/from the CNS.
Nervous system communication can be conceptualized as working through a 2-step process.
signal movement goes down a neuron’s axons
signal movement (from said axon) goes to a second cell across a structure known as a synapse.
A nerve signal moves from one neuron to another across a synapse. Synapse includes:
a 'sending’ neuron
a 'receiving’ neuron
a synaptic cleft - a tiny gap between the two cells
A chemical called a neurotransmitterdiffuses across the synaptic cleft from the sending neuron to the receiving neuron. It binds with receptors on the receiving neuron, keeping the signal going.
The spinal cord can receive input from sensory neurons (and instruct motor neurons to respond) with no input from the brain. The spinal cord also channels sensory impulses to the brain.
The spinal cord has a darker (gray matter) H-shaped central area composed mostly of the cell bodies of neurons. The lighter (white matter) peripheral area is mostly composed of axons.
The central canal of the spinal cordis filled with cerebrospinal fluid that provides the spinal cord with nutrients. Spinal nerves extend from the spinal cord to the majority of areas of the body.
Sensory neurons, which transmit information to the spinal cord, have their cell bodies outside the spinal cord (in the dorsal root ganglia).
Spinal cord motor neurons have cell bodies that lie within (the gray matter of) the spinal cord. The axons of these neurons leave the spinal cord through its ventral roots.
The dorsal and ventral roots come together (like fibers being joined in a cable) to form a spinal nerve.
Reflexes are automatic nervous system responses (triggered by specific stimuli) that help us avoid danger or preserve a stable physical state (physical equilibrium).
The neural wiring of a single reflex (called a reflex arc) start with a sensory receptor that’s run through the spinal cord to a motor neuron. This proceeds back out to an effector (once again, a muscle or gland). The brain is not involved in the reflex arc.
The sympathetic division of the autonomic nervous system is often called the fight-or-flight system because it generally prepares the body to deal with emergencies.
What does it do?
accelerates the heart
stimulates the release of glucose
secretes adrenaline and noradrenaline
relaxes the bladder
inhibits sex organs
The parasympathetic division is often called the rest-and-digest system because it conserves energy and promotes digestive activities.
What does it do?
slows the heart
stimulates the gallbladder
contracts the bladder
stimulates sex organs
Most organs receive input from both systems.
There are 7 major regions in the adult brain:
The cerebrum has a thin outer layer of gray matter - the cerebral cortex - that surrounds a much larger area of cerebral white matter.
Differing portions of the cerebral cortex play a central role in processing sensory information and in carrying out almost all of our conscious mental activities.
2. Cerebellum. Thecerebellumrefines bodily movement and balance,based on sensory inputs.
3. Thalamus. The thalamus receives most of the body’s sensory information and then transfers it to different regions of the cerebral cortex (for processing).
4. Hypothalamus. The hypothalamus is integral to regulating drives and maintaining homeostasis - partly through its regulation of hormonal release.
The brainstem is a collective term containing:
5. Midbrain. The midbrain helps maintain muscle tone and posture.
6. Pons. The pons primarily relays messages between the cerebrum and the cerebellum.
7. Medulla oblongata. The medulla oblongata helps regulate involuntary functions such as breathing and digestion. When people are ‘braindead’, only their medulla oblongata is left functioning.
All human senses operate through cells called sensory receptors. Sensory receptors respond to stimuli (changes in the cells environment).
The sensory receptors transform the responses into stimuli - electrical signals - that travel through action potentials.
Signals from every sense (except smell!) are routed through the brain’s thalamus and then to specific areas of the cerebral cortex.
The sense of touch works through a variety of sensory receptors that distinguish qualities such as light or heavy pressure, new or ongoing contact, texture, etc.
In some sensory cells, the stretching of their outer membrane prompts an influx of ions that results in the initiation of a nerve signal.
Our sense of smell (or olfaction) works through a set of sensory receptors whose dendrites extend into the nasal passages.
Odorants - which are molecules that have identifiable smells - bind with hair-like extensions (cilia) of dendrites, resulting in a nerve signal to the brain.
The higher processing centers of the brain distinguish these odorants by sensing unique groups of neurons that fire in connection with given odorants.
humans have 340 - 380 different receptors.
dogs have about 1000 different receptors.
rats have about 1, 500 different receptors.
Our sense of taste works through a group of taste cells, located in taste buds near the surface of the tongue. The taste cells have receptors that bind to ‘tastants’ or molecules of food that elicit different tastes.
A given taste cell can respond through any 4 to 6 chemical signaling routes that correspond to the basic tastes of sweet, sour, salty, bitter and the possible fifth and sixth tastes of umami and calcium.
The neurons that receive input from taste cells vary in their response to different tastants. The brain makes sense of the pattern of input it gets from these neurons, thus yielding the large number of tastes we experience.
Our sense of hearing is based on the fact that vibrations result in 'waves’ of air molecules that are more (and less) compressed than the ambient air around them.
These waves of compression bump up against our eardrums (or tympanic membranes) which in turn vibrate; this initiates a chain of vibrations that ends in the fluid-filled cochlea of the inner ear.
'Hair cells’ in the cochlea have ion channels that open and close in response to this vibration, resulting in nerve signals to the brain.
In vision, light enters the eye through the cornea and then passes through the lens on its way to the retina (at the back of the eye).
Light is bent (or refracted) by the cornea and the lens in such a way that it ends up as a tiny, sharply focused image on the retina.
Light signals are converted to nervous system signals by cells in the retina called photoreceptors, which come in 2 varieties:
Rods function in dim light but are not sensitive to color.
Cones function best in bright light but are sensitive to color.
These photoreceptors have pigments embedded in membranes within them.
Vision signals travel from photoreceptors through two sets of adjoining cells (the latter of which have axons that come together to form the body’s optic nerves).
When light strikes a pigment, it changes the pigment shape in a way that prompts a cascade of chemical reactions that result in neurotransmitter release being inhibited between the rod or cone and its adjoining connecting cell. The lack of release sends the signal: ‘photoreceptor stimulated here’.
The brain doesn’t passively record visual information; it constructs images as much as it records them.
The visual perception operates through a series of genetically based 'rules’ that allow us to quickly make sense of what we perceive.
‘Love is a drug,’ it is said,
making Cupid a pusher too young to be prosecuted.
I believe it, for I’ve felt the tsunami
strike of chemicals flood my brain:
adrenaline quickening my pulse,
and stealing the oxygen so I could inhale only you;
dopamine causing every efferent nerve fibre
to tingle at your proximity;
and serotonin leaving me with no taste for food -
I was sated by constant thoughts of you.
Even if it is a drug, it feels pure,
and somehow right to wallow in it,
let it consume us,
and want for these feelings to never stop.
But they also say:
‘It’s all fun and games until somebody gets hurt’.
What else can we expect from a little boy
wielding a bow and arrow
who was never taught to play gently?
Because after the high of initial infatuation
we have to come down,
and are left depleted and bereft.
Our bodies scream out for another dose of our beloveds,
and we want more, more, more,
until they can no longer satisfy our cravings.
So we leave in search of something different,
all to dull the pain of a thousand unspoken heartaches.
Now, I’ve both had love, and been without.
And what I want to know is, if love is a drug
why haven’t chemists discovered
a way to pop it, sniff it, or mainline it?
Because I need another hit.
THESE MOTHER EFFERS RIGHT HERE ARE THE NAPKINS OF THE GODS. I HAD A FRIEND RECOMMEND THEM TO ME AND LET ME TELL YOU WHAT, THEY CHANGED MY LIFE FOREVER. THESE THINGS ARE BLACK MAGIC PADS. THEY ARE SO THIN IT FEELS LIKE YOUR GOING COMMANDO IN YOUR PANTIES, THEY HAVE A SKINNIER FRONT AND A WIDER BACK TO COVER FOR THE NATURAL CHANNEL YOUR BUTTCRACK CREATES WHEN YOURE ON YOUR PERIOD. AND THEY DONT GIVE YOU AN UNWANTED WAGGING TAIL IN YOUR UNDERWEAR EITHER. I BLEED LIKE A STUCK PIG AND IVE ALWAYS USED SUPER HUGE THICK PADS WITH HAMSTER BEDDING FLUFF IN THEM AND THEY ALWAYS GOT NASTY AND FILLED UP AND WET AND I GOT PAD WEDGIES WHEN I GOT HOT AND SWEATY BECAUSE MOTHER NATURE DOES NOT STOP WHEN SUMMER COMES AROUND. THESE INFINITY THINGS ARE MIND BLOWING. IF YOU HAVE A HEAVY FLOW LIKE ME YOU KNOW THE FEELING OF YANKING YOUR PANTS DOWN WHEN YOU GO PEEPEE AND HAVING THE WHOLE TOP LAYER OF YOUR PAD FLOWING WITH THE RED RIVER AND EVEN THOUGH YOU JUST CHANGED IT YOU GON HAVE TO CHANGE IT AGAIN BECAUSE YOU CANT LIVE LIKE THIS. BUT THESE MOTHER EFFERS RIGHT HERE, NO NO NO NOT TODAY. I DONT KNOW WHERE THE BLOOD GOES BUT THESE THINGS ARE THE PORTAL TO NARNIA BECAUSE WHEN YOU GO TO THE BATHROOM EVEN IF YOUVE BEEN WEARING THIS SUCKER FOR 5 HOURS IN THE MIDDLE OF YOUR PERIOD, THERE IS ONE SMALLISH PATCH OF BLOOD THATS MANAGED TO GASP ITS WAY UP FROM NARNIA. THATS ALLYOU SEE. ONE FRIGGIN PATCH AND LO AND BEHJOLD WHEN YOU TURN THAT PUPPY OVER YOU CAN SEE THE SHADOW OF WHERE THE REST OF YOUR UTERUS HAS BEEN SOAKED INTO THE ENTIRE REST OF THE PAD BUT THERES ONLY THAT ONE SPOT OF NASTINESS THATS BEEN TOUCHING YOU. THE REST HAS BEEN LOCKED AWAY IN PERIOD JAIL. I DONT KNOW HOW THEY DID IT (obviously someone sold their soul to crowley) BUT THESE THINGS ARE AMAZING AND THE SAME PRICE FOR THE SAME AMOUNT OF PADS YOUD USE ANYWAYS. AND IF YOU GET THEM SOON YOU EVEN GET A FREE NIFTY LITTLE PAD POCKET THINGIE. GO AND GET THESE THINGS. IM SERIOUS YOU WONT REGRET IT.
First we must define the above terms. The efferent stance refers to reading and taking the direct meaning from it. Examples would be directions to follow, conclusions to be retained, information to be retained or acted upon after reading the text. Aesthetic stance on the other hand is when you pay attention to the feelings, images, emotions, sounds, or rhymes of words or tensions of the text.
Literature and Life
I try to relate the above two not just to literature, but also to life in general. You carry away with you what you learn but actually understanding and knowing why is a complete whole step. That’s why the efferent stance is unchanged (unless you take nothing from an experience) and the aesthetic stance is ever changing. Most things fall between efferent and aesthetics. But bringing your past and present feelings, ideas, beliefs, etc. will make your self expression better.
Reconsider Your Aesthetic Stance
Always know that your aesthetic stance is ever changing and I hope things will occur to challenge it. It can remain the same or it can broaden or narrow. Just know that it will reflect onto others. So when things don’t seem quite like you would want them, acknowledge your efferent stance but reconsider your aesthetic stance.
If you’ve got time to spare, check out the book “The Giver”.
I liveeeeeeeeee… again. It’s been a while since my last post, and I’m just going to openly admit that I’m a lazy mother effer. Sorry.
Anyway, my brain FINALLY squeezed out some creativity and this is what resulted from that.
“Happy Tuesday, everyone, and thanks for clicking on this new video. I promise this week’s video will be worth the click,” You stated, making a very long introduction to your weekly upload. “…because I’ll be playing the ‘What’s in my Mouth’ challenge with the one and only Jack Maynard, aka The Pretty Face, aka my boyfriend.”
“Well that was quite the intro,” Jack commented, draping an arm around the back of your chair. “And yes, note that I’m only doing this because I was promised a head massage.”
“See, once you start dating them ladies and gents, collaborating suddenly becomes a source of bribery,” You rolled your eyes. “And to think you told me you would do it because you love me…”
Jack grinned, “I do love you,” He leaned close to quickly kiss your cheek. “Somedays I just love your massages more.”
“And with that comment, don’t take any personal offense to anything that may happen in the next few minutes,” You remarked, lightly shoving him away. “Now let’s stop sickening my viewers with our disgusting couple crap and get on with the challenge!”
jvlevins: I was trying to move through the crush of people and no one would let me by. I saw a couple of little guys getting through so I grabbed one guys shirt and said “don’t stop you little effer” He didn’t. No wonder Peta wins the Hunger Games. #sorryjoshhutcherson #bunbury2015
Its that time of year where those of us who are in the upper-level courses have the massive 1 week review in every class of all the biology that has come before. I have a few tricks that help me remember the most simple concepts in Bio, that will hopefully help you guys save time too. Some of these I actually came up with, others I have learned from professors and such, but above all, I’m sure 10000 other pre-meds have thought of these before so feel free to steal them!
What bases pair and how many bonds?
How many Na and K go in and out of the pump?
Na+ has 3 characters, so 3 Na go out, and K+ has two, so two K come in.
Which is afferent and efferent?
“A” comes before “E”, so afferent receives the signal before the brain can send a response back through the efferent pathway.
How do I remember Symporter vs Antiporter?
If the two molecules are going in the Syme direction its Symporter opposite directions=anti.
How do I keep tendons and ligaments separate?
1st think of your Achilles Tendon. If that doesn’t work I used to use: Ligate the bones (ligate means to tie something up in surgery).
Okay, thats about all I got. Like I said, there are only a few and they’re kinda cheesy but they work for me. Let me know if they help you!
I was trying to get gas at the pumps, but I was having a hard time pulling that effer out of its holder, and so I kind of spastically ripped it free. When I turned around I noted a man was staring at me and I was a little embarrassed so I went to say, ‘yah I know, I’m a fucking retard’, but I got tongue tied so instead I looked him dead in the eye and said.