ch 4 Flashcards
The Central Nervous System
Brain
Spinal Cord
A collection of neurons and supportive tissue
running from the base of the brain down the centre
of the back.
Protected by spinal column
Peripheral Nervous System:
Carries information to and from the central nervous system. 43 pairs of nerves. 31 spinal nerves enter the spine. 12 cranial nerves enter the brain.
peripheral nervous system divides into 2
somatic: controls skeletal muscles
autonomic: regulates glands, blood vessels, internal organs
autonomic nervous systems divides into 2
sympathetic: mobilizes body for action, energy output
Parasympathetic: conserves energy, maintains quiet state
Communication in the Nervous System
Neuron
Conducts electrochemical signals; the basic unit of the nervous system
Glia
Cells that support, nurture and insulate neurons, remove debris when
neurons die, enhance the formation and maintenance of neural
connections, and modify neuronal functioning
The Structure of Neurons
Dendrites Branches of the neuron that receive information from other neurons and transmit it towards the cell body Cell Bdy The part of the neuron that keeps it alive and determines whether or not it will fire Axon The neuron’s extending fibre that conducts impulses away from the cell body and transmits them to other neurons
Dendrites
Branches of the neuron that receive
information from other neurons and
transmit it towards the cell body
Cell Bdy
The part of the neuron that keeps it
alive and determines whether or not it
will fire
Axon
The neuron’s extending fibre that
conducts impulses away from the cell
body and transmits them to other
neurons
Myelin Sheath
A fatty insulation that
may surround the axon
of a neuron
Stem cells
Immature cells that renew themselves and have the potential to
develop into mature cells; stem cells from early embryos can
develop into any type of cells
Controversial as most stem cells come from embryos which are
only a few days old
How Neuron Communicate
Neurons communicate over synapses Communicate by brief changes in electrical voltages called an action potential which produces an electrical current or impulse Neural “messages” are sent via a chemical substance called a neurotransmitter
Neurotransmitters
Neurotrasmitters can be either excitatory or inhibitory
Several types of neurotransmitters
- Serotonin
Involved in sleep, appetite, sensory perception, tempurature
regulation, pain suppression and mood - Dopamine
Involved in volentary movement, learning, memory, emotion,
pleasure or reward and response to novelty - Acetylcholine
Involved in muscle action, cognitive functioning, memory and
emotion - Norepinephrine
Involved in increased heart rate and slowing of intestinal activity
during stress, memory, learning, dreaming waking from sleep and
emotion - GABA
Major inhbitory transmitter in the brain - Glutamate
Major excitatory transmitter; released by about 90% of the brain’s
neurons
Endorphins Chemical substances in the nervous system that are similar in structure and action to opiates; involved in pain reduction and pleasure Hormones Chemical substances secreted by glands that affect the functioning of other organs include: 1. Melatonin 2. Oxytocin 3. Adrenal Hormones 4. Sex Hormones
Brain Mapping
Two Approaches Patients with Damage or Lesions Look for changes when an area is damaged Remove an area of the brain in animals and observe effects Imaging Electrical and magnetic detection Scanning the brain
Mapping the Brain
Lesioning
the function of a part of the brain can be inferred after that
part is damaged or removed
this can be done intentionally with animals, or we can also
study accidental lesions in humans
these accidental lesions can be caused by physical trauma
or disease
brain lesions are much more common in some groups than
others
Electrical and Magnetic Detection
Brain can be probed using electrodes
Electrodes detect electrical activity of
neurons
Translates activity in patterns (Brainwaves)
- Electroencephalogram (EEG)
Brainwave recoding referred to as EEG Method is imprecise due to “noise” Can be made more accurate using “needle electrodes” and “microelectrodes”
- Transcranial magnetic stimulation (TMS)
Involves delivering a large magnetic disturbance
current through a wire coil on a person’s head
Acts as a temporary, “virtual” lesion
Also used to:
produce motor responses
temporarily inactivate an area of the brain
treat depression
Scanning the Brain
1. Positron Emission Tomography (PET)
A method for analyzing biochemical activity in the
brain, using injections of a glucose-like substance
containing a radioactive element.
Active areas have increased blood flow
Sensors detect radioactivity
Different tasks show distinct activity
patterns
Magnetic Resonance Imaging (MRI)
Method for studying body and brain tissue.
Magnetic fields align certain ions and
compounds.
When field is removed, these molecules
release energy as radio waves.
Computer calculates tissue density from
radio waves.
Provides clear, 3D images.
Both a structural and functional type of
image is possible.
Functional Magnetic Resonance Imaging
Uses the same equipment as a structural MRI.
Oxygen-rich blood has different magnetic properties than oxygen-depleted
blood.
Can measure which parts of the brain are receiving an increase in blood flow.
Image can be placed on top of a structural MRI image.
The Brain Stem
Pons Involved in sleeping, waking and dreaming. v Medulla Ø Responsible for certain autonomic functions such as breathing and heart rate. v Reticular activating system (or formation) Ø Arouses cortex and screens incoming information.
Pons
Involved in sleeping, waking and
dreaming.
v Medulla
Ø Responsible for certain autonomic
functions such as breathing and
heart rate.
v Reticular activating system (or formation)
Ø Arouses cortex and screens incoming
information
The Cerebellum
Regulates movement and balance. Involved in remembering simple skills and acquired reflexes. Plays a part in: Analyzing sensory information Solving problems Understanding words
The Thalamus
Relays sensory messages to the cerebral cortex. Includes all sensory messages except those from olfactory bulb.
Hypothalamus and Pituitary Gland
Involved in emotions and drives vital to survival.
fear, hunger, thirst, and reproduction.
Regulates autonomic nervous system
Pituitary gland
Small endocrine gland which releases
hormones and regulates other endocrine
glands.
The Amygdala
Responsible for: Arousal Regulation of emotion The initial emotional response to sensory information. Plays important role in Mediating anxiety and depression Emotional memory
The Hippocampus
Responsible for: Storage of new information in memory. Comparing sensory information with what the brain expects about the world. Enabling us to form spatial memories for navigating the environment.
The Cerebral Cortex
Largest brain structure This upper part of the brain is divided into two cerebral hemispheres that are connected by the corpus callosum. In charge of most sensory, motor and cognitive processes. Surrounded by cerebral cortex, a collection of several thin layers of cells (grey matter).
Lobes of the Cerebral Cortex
Occipital lobes (visual cortex) Parietal lobes (somatosensory cortex) Temporal lobes Memory, perception, emotion and auditory cortex Left lobe, Wernicke’s area Frontal lobes Emotion, planning, creative thinking and motor cortex Left lobe, Broca’s area
Culture’s Impact on Brain Structure
Bilinguals may use different brain regions for retrieval in different
languages
Literacy shapes the distribution of white matter and grey matter in
the brain
Technological literacy may affect brain activity
Phineas Gage
Gage was a railroad construction foreman An 1848 explosion forced a steel tamping rod through his head Others said he was “…no longer Gage…” Lost his job and worked as a sideshow exhibit
The Two hemispheres of the Brain
A house divided Evidence from: 1. People with lateralized brain damage. 2. People with the two halves of the brain disconnected 3. People with normal, intact brains
Knowing your Lefts and Rights
Knowing your Lefts and Rights The Greek physician Hippocrates discovered that injuries to one side of the head led to the opposite side of the body becoming paralyzed or seizing. The left side of the brain controls the right side of the body. The right side of the brain controls the left side of the body.
Functional Differences Between the
Hemispheres
Basic sensory and motor functions are the same. Higher association areas have functional differences between the hemispheres. Subject to individual variation, such as left- or right-handedness.
The Corpus Callosum
Millions of myelinated axons connecting the brain’s hemispheres. • Provides a pathway for communication between hemispheres. • If surgically severed to treat epilepsy, hemispheres cannot communicate directly.
Damage to the Right Hemisphere
results in:
results in: - Impairments in facial recognition - Lack of emotion in spoken language - Poor perception of emotion in language - Disorganization of movement - Less likely to result in depression than LH damage
Evidence from Lateralized Brain Damage
- Problems with language
- Right side hemiparesis
- Depression
- Impairment on tasks requiring
“logical ordering”
Split-Brain Experiments
Can selectively expose one half of the brain to visual or tactile Stimulation. Normally, this information would be “shared” between the two Hemispheres.
The Two Hemispheres: Allies or Opposites?
Research on split-brain patients shows us:
Nearly all right-handed and the majority of left-handed individuals
process language mainly in the left hemisphere.
Many researchers believe in left-hemisphere dominance.
Others insist the right-hemisphere is important for spatial visual
problem-solving, comprehending non-verbal sounds, and some
language abilities.
Sex Difference in the Brain
After analyzing 49 studies of sex differences in brain anatomy,
researchers found small differences between the two groups and larger
differences within groups.
There do appear to be sex differences in lateralization of language.
Males show left-hemisphere activation only; females, left and right.
There also appear to be differences in amounts of grey matter: females
have more.
What do “Differences” Mean for Behaviour?
These supposed differences are stereotypes.
A brain difference does not necessarily explain behaviour or performance.
Sex differences in the brain could be the result rather than the cause of
behavioural differences.
Use your critical thinking skills to evaluate all of the research!
