nervous system. nerves hold out your hand in front of you now wave at yourself now, tap your head...
TRANSCRIPT
Nervous System
Nerves
•Hold out your hand in front of you•Now wave at yourself•Now, tap your head
•Put your arms down•Say out loud to “Move Arm”…Just tell it to
move▫Did it move?▫Why not?
Nerves
•How does our arm know when you want it to move?
•Our experiment shows that your arm does not understand spoken commands.
•So what does it understand? •What tells it to move. If you think it is
your brain, you are correct.
Nerves
•But wait a moment. Your brain is clear up in your head, while your arm is clear down on your body.
•How does your brain talk to your arm? Somehow they must be connected.
•The connection between your brain and your arm, as well as every other part of your body is known as your nervous system.
Nervous System
•How are messages transmitted along your nervous system? Interestingly enough, messages travel from your brain to your various body parts via electricity, in much the same way cable television signals travel from the cable company to your house, or in the same way that this web page traveled from our web servers to your computer.
Are your Synapses Firing?
•Remember that the cells making up your nervous system are called neurons.
•Neurons are connected to other neurons, as well as to other tissues within the body via synapses.
•The location where a neuron connects to another cell is called a synapse.
Brain neurons firing• When a message is transferred
through a neuron it passes to the next neuron via an amazing fast chemical and electrical reaction.
• Because of its lightning speed, it is often said that a person’s synapses are firing when they are in deep thought.
• Regardless of whether you are solving a problem, or taking a nap, your synapses are always busy transporting messages.
The Central Nervous System (CNS)•The Central Nervous
System is made up of your brain, and your spinal cord.
• It is the main control center of your body, and the center of thought. Your Central Nervous System controls most of the actions within your body.
Peripheral Nervous System• 3 kinds of neurons
connect CNS to the body▫ sensory▫ motor▫ interneurons
• Motor - CNS to muscles and organs
• Sensory - sensory receptors to CNS
• Interneurons: Connections Within CNS
SpinalCord
Brain
Nerves
Peripheral Nervous System
Skeletal(Somatic)
Sympathetic Parasympathetic
Autonomic
Peripheral Nervous System
Neurons Generate Nerve Impulses•A nerve impulse travels along the axon
and dendrites as electrical current caused by ions moving in and out of the neuron through voltage-gated channels▫ these membrane channels open and close in
response to electrical voltage changes
•The impulse starts when pressure or other sensory inputs disturb a neuron’s plasma membrane, causing Na+ channels to open
Neurons Generate Nerve Impulses•When Na+ channels open, Na+ floods into
the neuron from the outside▫for a brief moment, the inside of the neuron
is “depolarized,” becoming more positive▫the open Na+ channels in the small patch of
depolarized membrane remain open for only a half a millisecond
▫if the voltage change of the depolarization is great enough, it causes nearby voltage-gated Na+ and K+ channels to open
Neurons Generate Nerve Impulses•The Na+ channels open first, which starts
a wave of depolarization moving down the neuron▫this moving local reversal of voltage is
called an action potential an action potential follows an all-or-none law:
a large enough depolarization produces either a full action potential or none at all
Neurons Generate Nerve Impulses•The K+ voltage-gated channels open after
a slight delay, causing K+ to flow out of the cell▫this makes the interior of the neuron more
negative, causing the voltage-gated Na+ channels to close
•The period of time after an action potential has passed but before the resting potential is restored is called the refractory period
Somatic System
• Nerves to/from spinal cord▫ control muscle
movements▫ somatosensory
inputs
• Both Voluntary and reflex movements
• Skeletal Reflexes▫ simplest is spinal
reflex arcMuscle
MotorNeuron
Interneuron
Skin receptors
SensoryNeuron
Brain
Autonomic System
•Two divisions: ▫ sympathetic▫ Parasympatheitic
•Control involuntary functions▫ heartbeat▫ blood pressure▫ respiration▫ perspiration▫ digestion
•Can be influenced by thought and emotion
Sympathetic
•“Fight or flight” response
•Release adrenaline and noradrenaline
• Increases heart rate and blood pressure
• Increases blood flow to skeletal muscles
• Inhibits digestive functions
CENTRAL NERVOUS SYSTEMBrain
Spinalcord
SYMPATHETIC
Dilates pupil
Stimulates salivation
Relaxes bronchi
Accelerates heartbeat
Inhibits activity
Stimulates glucose
Secretion of adrenaline,nonadrenaline
Relaxes bladder
Stimulates ejaculationin male
Sympatheticganglia
Salivaryglands
Lungs
Heart
Stomach
Pancreas
Liver
Adrenalgland
Kidney
Parasympathetic
•“Rest and digest” system
•Calms body to conserve and maintain energy
•Lowers heartbeat, breathing rate, blood pressure
CENTRAL NERVOUS SYSTEMBrain
PARASYMPATHETIC
Spinalcord
Stimulates salivation
Constricts bronchi
Slows heartbeat
Stimulates activity
Contracts bladder
Stimulates erectionof sex organs
Stimulates gallbladder
Gallbladder
Contracts pupil
Sensory Information sent to opposite hemisphere
•Principle is Contralateral Organization
•Sensory data crosses over in pathways leading to the cortex
•Visual Crossover▫ left visual field to right
hemisphere▫ right field to left
•Other senses similar
Left visualfield
Right visualfield
Opticnerves
CorpusCallosum
Left VisualCortex
Right VisualCortex
Brain
•Your mind is a powerful and amazing organ. Its ability to calculate, control and think exceeds that of every computer on Earth put together.
•Your brain has three main parts. ▫Cerebrum▫Cerebellum▫Brain Stem.
Cerebrum
•Largest portion of the brain•Your cerebrum is responsible for all the
voluntary processes that you do each day, including thought.
•Voluntary means that you want to do something, or that you decide to do something, like hold your hand in the air, wave to yourself, and tap yourself on the head.
Cerebrum
•As you do these actions, your cerebrum sends electrical messages out to your body using the neurons of your nervous system.
•When the message reaches your arm, your muscles obey, and do as they are instructed.
Cerebellum
•Your cerebellum aids your cerebrum in the task of moving your muscles.
•It helps to maintain balance, moving the muscles you don’t think to move, as you make your arm wiggle around. This allows you to move about smoothly, with little effort.
Brain Stem•Your brain stem sites at the
base of the brain, and connects it to the spinal cord.
•The brain stem controls the flow of information between the brain and the rest of the body, and also controls many of the involuntary movements that your body does, every single day.
Localization of function
Frontal
Parietal
Occipital
Temporal
Occipital Lobe
Input from Optic nerve
Contains primary visual cortex most is on surface
inside central fissure
Outputs to parietal and temporal lobes
OccipitalLobe
VisualLobe
Temporal Lobe
Inputs are auditory, visual patterns speech recognition face recognition word recognition memory formation
Outputs to limbic System, basal Ganglia, and brainstem
Contains primary auditory cortex
TemporalLobe
TemporalLobe
AuditoryCortex
ParietalLobe
Parietal Lobe Inputs from multiple
senses
contains primary somatosensory cortex
borders visual & auditory cortex
Outputs to Frontal lobe
hand-eye coordination
eye movements
attention
SomatosensoryCortex
FrontalLobe
Frontal Lobe Motor action/behavior Contains primary
motor cortex
MotorCortexMotorCortexBroca’s
Area
MotorCortex
WorkingMemory
No direct sensory input Important planning and
sequencing areas Broca’s area for
organization/speech
Prefrontal area for working memory
Frontal Lobe Disorders
Broca’s areaproductive aphasia--an acquired language
disorder affecting all modalities such as writing, reading, speaking, and listening and results from brain damage
Prefrontal arealose track of ongoing contextfail to inhibit inappropriate
responses
The Nervous System: Summary Major structures of the
nervous CNS, Somatic, Autonomic Two hemispheres & 4 lobes
Organization contralateral input & output primary sensory areas motor areas Commissure
Localization of functions Central Nervous System
Peripheral Nervous System
Corpus Callosum
•What happens when the corpus callosum is cut?
•Sensory inputs are still crossed•Motor outputs are still crossed•Hemispheres can’t exchange data
•Epileptic
The ‘Split Brain’ studies
•Surgery for epilepsy : cut the corpus callosum
•Roger Sperry, 1960’s
•Special apparatus▫ picture input to just one
side of brain▫ screen blocks objects on
table from view
Nonverbalrighthemisphere
Verballefthemisphere
Nonverbalrighthemisphere
Verballeft
hemisphere
??
“What didyou see?”
•Picture to left brain▫can name the object▫left hand cannot
identify by touch
Picture to right brain can’t name the object left hand can identify
by touch
“Using your left hand,Pick up what you saw.”
The ‘Split Brain’ studies
I saw anapple.
“What didyou see?”
Nonverbalrighthemisphere
Verballeft
hemisphere
Super Highway• Like a powerful broadband Internet connection,
your spinal cord can move a lot of data very quickly. Its job is to carry messages to and from the body to the brain.
• There are 32 different nerves that connect directly into the spinal cord, and that branch outward towards the rest of the body.
• Reflexes are processed directly in the spinal cord, allowing you to respond very quickly to danger, without wasting time thinking about what you should do.
Addictive Drugs Act on Chemical Synapses•Emotional states (mood, pleasure, pain,
etc.) are determined by particular groups of neurons that use special sets of neurotransmitters and neuromodulators▫many researchers think that depression
results from a shortage of serotonin▫Prozac, an anti-depressant, inhibits the
reabsorption of serotonin
Drugs alter transmission of impulses across the synapse
Addictive Drugs Act on Chemical Synapses•Nerve cells are particularly prone to the
loss of sensitivity when exposed to a chemical signal for a long time
▫if receptor proteins within synapses are exposed to high levels of neurotransmitters for prolonged periods, the nerve cell often responds by inserting fewer receptor proteins into the membrane
Addictive Drugs Act on Chemical Synapses•Cocaine acts a neuromodulator, causing
abnormal amounts of neurotransmitters to remain in the synapse for long periods▫it affect neurons in the brain’s pleasure
pathways these cells transmit pleasure messages using the
neurotransmitter dopamine
▫cocaine works by blocking transporter proteins on the presynaptic membrane that normally reabsorb dopamine because dopamine cannot bind to a transporter, it
remains in the synapse and continues to stimulate
Addictive Drugs Act on Chemical Synapses•When receptor proteins in the pleasure
pathways of the brain are exposed to high levels of dopamine due to cocaine, the nerve cells respond by lowering the number of receptor proteins▫with so few receptors, the drug user needs
the drug to maintain even normal nerve activity levels
▫this is addiction, the physiological adaptation of the nervous system due to drug abuse
How drug addiction works
Addictive Drugs Act on Chemical Synapses•Nicotine, also an addictive drug, binds to
postsynaptic receptors in the brain that normally bind to Ach
•The brain responds by▫making fewer receptors to which nicotine can
bind▫altering the pattern of activation of the nicotine
receptors (i.e., their sensitivity to neurotransmitters)
•This leads to profound changes in the patterns of release of many neurotransmitters, and addiction results
How the Brain Works
•The cerebrum is the center for thought and association and makes up about 85% of the weight of the brain▫the cerebrum is divided into right and left
halves, called cerebral hemispheres
•Much of the neural activity of the cerebrum occurs within a thin, gray outer layer called the cerebral cortex
Senses• We use our senses to get information about the
world around us into our brains. • There are five main senses that most of us use each
day. ▫Sight▫Hearing▫Touch▫Taste▫smell
• Without senses, your brain would have no way of knowing what was going on around you. Life would be a very lonely, dark, and quiet place.
Eyes•The human eye is an amazing
and powerful organ. As you read the words on this screen, your eyes see the shapes of the letters, and transmit the information back to your brain.
• Light travels from the computer screen to your eyes, entering them through a transparent layer of tissue called the cornea.
Eyes• The light of your computer screen then travels
onward through the lens. The lens of your eye focuses the light onto a special tissue called the retina.
• The retina is lined with special photoreceptors called rods and cones.
• Rods are more sensitive to light, but cannot distinguish between colors.
• While cones are less sensitive, but can differentiate the different colors, giving us color vision.
• Not all animals have cones. What does this mean? It means that many animals see in black and white.
Eyes
•As light lands on the rods and cones it is converted into electrical impulses and is transmitted to the brain, where it is interpreted as the beautiful images all around us.
Sensing Light: Vision
•Color blindness occurs when individuals are not able to perceive all three colors▫it typically occurs due to an inherited lack
of one or more types of cones▫it is a sex-linked trait, so men are more
likely to be colorblind than women
Test for color blindness
Sometimes your eyes can play tricks on you…
Optical Illusion•The brain also uses information learned in
the past to help it perceive the images that the eyes send
•the brain can have a tendency to “force” an image into something that the image is not, just so the image looks more familiar. These are called cognitive illusions
•optical illusion isn’t “real,” although the brain interprets the illusion as being true
Hearing
•How do we hear?•As objects move, or interact with other
objects, they cause the air to vibrate. Think of a swimming pool.
•What happens if you jump in? •First you make a big splash, followed by a
series of ripples. The harder you jump, the bigger your ripples will be.
Hearing
•The air of our atmosphere works in much the same way as a swimming pool.
•Even though we cannot see the ripples, every time, we move they go traveling through the air.
•Some of these ripples, or vibrations reach our ears. Inside of your ear is a thin tissue known as the tympanum, or eardrum.
Hearing
•The vibrations in the air cause your eardrum to begin vibrating.
•Behind your eardrum are three tiny bones called
•Hammer•Anvil•Stirrup
Hearing•As your eardrum begins to vibrate, so do
these tiny bones. •The last of these bones, the stirrup transmits
these vibrations into the fluid filled cochlea. •This causes tiny hairs within the cochlea to
vibrate. •The vibration of these hairs is converted into
electrical impulses, which are then transmitted to the brain for interpretation.
Taste and Smell
•The senses of taste and smell are interpreted from tiny objects on your tongue, and in your nose.
•Receptors within your nose detect and transmit smells to your brain, while your taste buds detect and transmit flavors to your brain
Taste and Smell
•Much of what we think we are tasting is actually smell.
•Try an experiment. Next time you are eating something, plug your nose. What happens?
•Much of the flavor disappears.
Touch
•The senses we have discussed so far have been located in one specific location, such as the eye, or nose.
•However, your sense of touch is not restricted to one small area, but covers your entire body.
•Your skin is sensitive to heat, to pressure, and to pain.
•Within your body, there are also many nerve endings that are sensitive to touch.
Things to keep your mind moving…•Leave your comfort zone. Getting good
at sudoku? Time to move on. Brain teasers don't form new neural connections once you've mastered them. So try something that's opposite your natural skills: If you like numbers, learn to draw. If you love language, try logic puzzles.
•Curry up. The active ingredient in Indian curry, turmeric, contains resveratrol, the same powerful antioxidant that makes red wine good for brain health. Eat curry once a week, or sprinkle it on salads, to protect brain cells from harmful free radicals.
•Redecorate and redesign your environment. Plant new flowers in front of your house. Redecorate the kitchen. Rearrange your closets and drawers. Replace the candles in your living room with some that have a different scent. Making such changes can alter motor pathways in the brain and encourage new cell growth.
•Sleep. Shut-eye isn't a luxury. It's when your brain consolidates memories. Poor sleep, caused by medical conditions, worry, depression, or insomnia, can interfere with your rest. So treat yourself to relaxing scents like vanilla before bed. They raise the chemical dopamine and reduce cortisol, a stress hormone.
•Play Games Whether you choose Risk, Pictionary, Scrabble, Sudouku, Wii, XBOX or Boggle, games are associated with a lower risk of developing dementia.
•They activate strategic, spatial, and memory parts of the brain, and require you to socialize, which can help form new neural pathways.
•Switch hands. It may be uncomfortable, but writing with your nondominant hand or operating a computer mouse with that hand can activate parts of the brain that aren't easily triggered otherwise.
•Anything that requires the brain to pay close attention to a formerly automatic behavior will stimulate brain-cell growth.