Download The Nervous System

The Brain: Source of Mind and Self
Chapter 4 Central Nervous System (CNS) -­‐ brain -­‐ spinal cord
The Nervous System
PSYC 1110: Lecture 12 Dr. J. Nicol
Central Nervous System
• Nervous system gathers and processes, generates motor responses, and coordinates the operaJons of different cells • Divided into two main parts: the central nervous system and the peripheral nervous system Peripheral Nervous System (PNS) -­‐ 43 nerve pairs that transmit informaJon to and from CNS
• Central nervous system (CNS): • Receives, processes, interprets, and stores incoming sensory informaJon • Send messages to glands, muscles, and internal organs • Comprised of two parts: brain and spinal cord
Peripheral Nervous System
• Peripheral nervous system (PNS): handles the inputs and outputs of the CNS • Sensory nerves carry messages from receptors in the skin, muscles, and other internal and external sense organs to the spinal cord, which in turn forwards them along to the brain • Sensory nerves are criJcal because they put us in direct contact with the outside world and our own bodies • Motor nerves carry orders from the CNS to muscles, glands, and internal organs • Motor nerves permit us to conduct motor movements and are responsible for regulaJng the hormones released by our glands Peripheral Nervous System
• PNS is divided into two parts: the somaJc nervous system and the autonomic nervous system • SomaJc nervous system consists of nerves that are connected to sensory receptors • Autonomic nervous system regulates the funcJoning of blood vessels, glands, and internal (visceral) organs • Divided into two complementary parts: the sympatheJc nervous system (SNS) and the parasympatheJc nervous system (PNS)
Autonomic Nervous System
Cells in the Nervous System
• Nervous system is made up of cells called neurons (nerve cells) -­‐ brain contains approximately 100 billion • CommunicaJon to and from the CNS is done by neural acJvity • Neurons are held in place by gluey cells called glia (glial cells), which make up about 90% of brain cells • Glial cells are criJcal to the funcJoning of neurons: provide nutrients, insulate from toxins, housekeeping of dead cells • Glial cells also communicate with other glial cells and with neurons
How Neurons Communicate
• Neurons communicate electrically and chemically • When a neuron is sJmulated a change in the electrical potenJal occurs between the inside and outside of the nerve cell • PosiJvely charged sodium (Na+) ions flow into the cell and posiJvely charged potassium (K+) ions flow out of the cell • Results in a brief change in the electrical voltage, called an acJon potenJal, which produces a propagaJng electrical impulse (or current)
High concentraJon of posiJvely charged sodium (Na+) outside the neuron and high concentraJon of posiJvely charged potassium (K+) inside the neuron
Visual cortex activates in blind individuals read they read Braille with their fingers
Activation in visual cortex when blind individuals perform tactile discrimination task Activation
Sadato et al. (1996)
Sadato et al. (1996)
De-­‐activation in visual cortex when sighted individuals perform tactile discrimination task De-­‐activation
Sadato et al. (1996)
Merabet et al. (2008)
Neurotransmi_ers
Endorphins and Hormones
• Serotonin -­‐ sleep, appeJte, sensory percepJon, temperature regulaJon, pain suppression, and mood • Endorphins (or endogenous opioid pepJdes) are the body’s natural pain killer, and they also promote pleasure • Dopamine -­‐ voluntary movement, learning, memory, emoJon, pleasure and reward, response to novelty • Endorphin levels spike when we are in pain or afraid, and also when we are in contact with a loved one • Acetylcholine -­‐ muscle acJon, cogniJve funcJoning, memory, and emoJon • Norepinephrine -­‐ increased heart rate and the slowing of intesJnal acJvity during stress, and neurons involved in learning, memory, dreaming, waking from sleep, and emoJon • Some endorphins funcJon as neurotransmi_ers, but most act primarily by altering the effects of neurotransmi_ers • GABA -­‐ the main inhibitory neurotransmi_er in the brain • Hormones are produced by endocrine glands, and are released directly into the bloodstream, where they are carried to areas of the body where they have their respecJve effects • Glutamate -­‐ is the major excitatory neurotransmi_er in the brain, it is released by about 90% of the brain’s neurons
• Hormones promote bodily growth, aid digesJon, regulate the metabolism
Endorphins and Hormones
• Melatonin -­‐ secreted by pineal gland, and helps regulate daily biological cycles • Oxytocin -­‐ secreted by the pituitary gland, contributes to human a_achment and promoJon of trust • Adrenal hormones -­‐ produced by the adrenal glands, are involved in emoJon and stress. When released they acJvate the SNS and increase arousal and prepare you for acJon Areas of the Brain
PSYC 1110: Lecture 13 Dr. J. Nicol
• Sex hormones -­‐ secreted by Jssue in the testes and ovaries, include androgens, estrogens, and progesterone which contributes to growth and maintenance of the uterine lining
Methods for Studying the Brain • Surgical ablaJon and lesioning • Electroencephalography (EEG) and event-­‐related potenJals (ERPs) -­‐ electrodes on the scalp record the electrical acJvity of neurons when they fire and brain acJvity is represented as brain waves • Transcranial magneJc sJmulaJon (TMS) -­‐ a powerful magneJc pulse is delivered to a localized area of the brain using a hand held coil (e.g., virtual lesion method) • Positron emission tomography (PET) -­‐ radioacJve glucose-­‐like substance injected into blood and accumulates in areas of the brain that are acJve; the radiaJon is read by a scanner and superimposed on a picture of the brain • FuncJonal magneJc resonance imaging (fMRI) -­‐ blood oxygenated level dependent (BOLD) response reflects the fact that blood in more acJve areas of the brain has less oxygen than blood in less acJve areas of the brain, difference changes how magneJc the blood is in acJve compared to less acJve areas
PET scans during different mental activities
fMRI showing brain activation during limb movements
Interpret with CauJon!
• Brain scans do not tell us what is happening inside a person’s head • Shows us where things are happening, but does not tell us why or how things are happening in the brain • Neurons fire to produce excitatory or inhibitory responses, so acJvity might be inhibitory in nature • Each brain is unique: a unique geneJc package is present in each of us at birth, and your unique experiences and sensaJons are constantly altering your brain’s biochemistry and neural networks
Cerebral Cortex
• Where higher order thinking takes place, and the wiring of the brain is most complex • Divided into two halves: the lek and right hemispheres • Lek and right hemispheres are connected by the corpus callosum • Lek hemisphere controls the right side of body, and right hemisphere controls the lek side of the body • LateralizaJon: each hemisphere is also specialized to do things that the other is not
Cerebral Cortex
Prefrontal cortex
• Where higher-­‐order thinking takes place, and where the wiring of the brain is most complex • Divided into two halves: lek and right hemispheres • Hemispheres are connected by the corpus callosum • Lek hemisphere controls the right side of body and right hemisphere controls the lek side of the body • LateralizaJon: each hemisphere is also specialized to do things that the other is not
Hemispheres of the Brain
• Two hemispheres communicate across the corpus callosum • When the two hemispheres are disconnected one side of the brain does not know what the other side knows (Myers & Sperry, 1953) • In split-­‐brain paJents: personality, intelligence, and motor skills remains intact • But their percepJon and memory are negaJvely affected
Lek visual field of each eye projects to right visual cortex and right visual field of each eye projects to lek visual cortex
LVF
RVF
In split brain paJents, right visual cortex only sees LVF from right eye and lek visual cortex only sees RVF from lek eye
LVF
RVF
“With lek hand, point to the face that was presented”
“Tell me what face that was presented”
“The Boy”
Lek hand controlled by right hemisphere
Language is controlled by the lek hemisphere
LateralizaJon
Sex Differences in the Brain
• FuncJonal imaging confirms that language tasks are performed in the lek hemisphere • Many anatomical and biochemical sex differences have been found in human and animal brains • Lek hemisphere is more acJve in mathemaJcal and technical tasks involving logic • Women’s brains have on average 11% more cells in the auditory cortex • CogniJve tasks are primarily performed in the lek hemisphere, so suggested we have dominant in that hemisphere • Right hemisphere is superior in problems requiring visuospaJal ability, face and emoJon recogniJon, creaJon and appreciaJon of art and music • Frontal lobes and limbic system take up a larger proporJon of the brain in females compared to males • CogniJve style of right hemisphere is intuiJve and holisJc, while cogniJve style of lek hemisphere is raJonal and analyJc • Women have more corJcal folds in the frontal and parietal lobes • In most real-­‐life acJviJes, the two hemispheres cooperate with each making a valuable contribuJon
• Parietal cortex and amygdala are larger in men compared to women Men and women both show acJvaJon in lek temporal lobe, but women also show acJvity in right temporal lobe
Sex difference in lateralizaJon on language tasks -­‐ so sex differences in the brain do exist!