Chapter 1: The Mind's Machine 4th ed.

neurons

the basic unit of the nervous system, has four functional zones:

input - dendrites receive info. from other cells

integration - the cell body integrates the info. it receives

conduction - a single axon conducts output info. from the cell body as an electrical impulse

output - axon terminals at the end of the axon communicate activity to other cells

motor neurons

large, have long axons, and stimulate muscles

sensory neurons

have various shapes that best respond to specific environmental stimuli, such as light, odor, or touch

interneurons

have tiny axons and analyze input from one set of neurons and communicate with others

multipolar neuron

one axon, many dendrites; most common

bipolar neuron

one axon, one dendrite

unipolar neuron

a single extension branches in two directions, forming an input zone and output zone

neuronal cell body and dendrites receive info. across synapses

info. is transmitted from the presynaptic neuron to the postsynaptic neuron

three components of synapses

1. presynaptic membrane - on the axon terminal of the presynaptic neuron

2. postsynaptic membrane - on the dendrite or cell body of the postsynaptic neuron

3. synaptic cleft - the gap that separates the membranes

synaptic vesicle

small sphere in presynaptic axon terminals that contain a neurotransmitter, a specialized chemical; neurotransmitters are released in response to electrical activity in the axon

neurotransmitter receptors

in the postsynaptic membrane are specialized proteins that react to neurotransmitter molecules

neural plasticity

continual remodeling of neuronal connections

axon hillock

cone-shaped area of the cell body that gives rise to the axon

converts input into electrical signals that travel down the axon and innervate target cells

axon collateral

branch of an axon that also ends in terminals

axonal transpoty

bidirectional movement of materials within an axon

glial cells

assist neuronal activity by providing raw materials, chemical signals, and structure and also participate in information processing

two types (glial cells) wrap around axons to provide a fatty insulation layer called myelin

1. oligodendrocytes form the myelin sheaths in the brain and spinal cord

2. schwann cells provide myelin to neurons outside the brain and spinal cord

nodes of ranvier

gaps between sections of myelin where the axon is exposed

two other types of glial cells

1. astrocytes - star-shaped with many processes that stretch around and between neurons and, sometimes, blood vessels; secrete chemicals; help form the outer membrane around the brain

2. microglial cells or microglia - tiny mobile cells that remove debris from injured or dead cells

central nervous system

consists of the brain and spinal cord

peripheral nervous system

includes all other parts of the nervous system outside the brain and spinal cord

the peripheral nervous system consists of nerves, or bundles of axons:

motor nerves - transmit info. from the spinal cord and brain to muscles and glands

sensory nerves - convey info. from the body to the CNS

somatic nervous system

nerves that interconnect the brain and the major muscles and sensory systems of the body

autonomic nervous system

nerves that connect to the viscera (internal organs)

the nerves of the somatic nervous system form two anatomical groups:

1. cranial nerves - innervate the head, neck, and visceral organs directly from the brain

2. spinal nerves - connect to the spinal cord

cranial nerves - 12 pairs

three are exclusively sensory:

olfactory (1) - smell

optic (2) - vision

vestibulocochlear (8) - hearing and balance

five are motor pathways from the brain:

oculomotor (3) - eye movement

trochlear (4) - eye movement

abducens (6) - eye movement

spinal accessory (11) - eye movement

hypoglossal (12) tongue

four have sensory AND motor functions:

trigeminal (5) - facial sensation, chewing muscles

facial (7) - taste sensation, facial muscles

glossopahryngeal (9) - throat sensation, throat muscles

vagus (10) - innervates the heart, liver, and intestines

spinal nerves - 31 pairs

consists of a group of motor fibers that project from the spinal cord and a group of sensory fibers that enter the spinal cord

spinal nerves are named for the segment of spinal cord they are connected to:

cervical (neck) - 8 segments

thoracic (trunk) - 12 segments

lumbar (lower back) - 5 segments.

sacral (pelvic) - 5 segments

coccygeal (bottom) - 1 segment

autonomic nervous system is the main system for controlling the body's organs ... two major divisions:

sympathetic nervous system

parasympathetic nervous system

sympathetic nervous system

has axons that innervate the sympathetic ganglia - small clusters of neurons outside the CNS

sympathetic innervation prepares the body for action - the fight-or-flight response

parasympathetic nervous system

helps the body relax and recuperate

parasympathetic neurons extend longer distances from the CNS to the parasympathetic ganglia

parasympathetic ganglia are usually close to the organ they innervate

a nerve or pathway is afferent if

it carries info. into a region of interest

a nerve or pathway is efferent if

it carries info. away from a region of interest

two types of brain tissue:

gray matter - contains more cell bodies and dendrites, which lack myelin

white matter - consists mostly of axons with white myelin sheaths

the brain has two cerebral hemispheres

cerebral cortex - the outermost, convoluted layer of the brain. the cortex has gyri (ridged or raised portions) and sulci (furrows)

each cerebral hemisphere has four lobes:

frontal — most anterior region

parietal — lies between the frontal and occipital lobes

occipital — posterior region, visual processing

temporal — lateral region, auditory processing

boundaries between lobes:

sylvian fissure - boundary of the temporal lobe

central sulcus - divides the frontal lobe from the parietal lobe

corpus callosum

bundle of axons that connects the two cerebral hemispheres

postcentral gyrus

strip of cortex behind the central cortex, important for touch

precentral gyrus

in the frontal lobe, important for motor control

neural tube develops three divisions:

1. the forebrain

2. the midbrain

3. the hindbrain

forebrain develops into:

the telencephalon and diencephalon

brainstem refers to:

the midbrain, pons, and medulla combined

pyramidal cells are:

the most prominent neurons in cerebral cortex, layer 3 or 5

in some regions, cortical columns, perpendicular to the layers:

extend the full thickness of the cortex and serve as info. processing units

basal ganglia are:

important in motor control and consist mainly of the caudate nucleus, putamen, and globus pallidus

the limbic system includes:

structures important for emotion and learning; amygdala, hippocampus, cingulate gyrus, olfactory bulb

amygdala

emotional regulation and perception of odor

hippocampus and fornix

learning

cingulate gyrus

attention

olfactory bulb

sense of smell

limbic structure - thalamus

a cluster of nuclei that relay sensory info.

limbic structure - hypothalamus

contains nuclei with many functions; also controls the pituitary

Midbrain sensory systems of the tectum:

superior colliculi — visual processing

inferior colliculi — auditory processing

midbrain motor system:

substantia nigra - part of the basal ganglia

other midbrain systems:

reticular formation - involved with sleep and arousal

periaqueductal gray - pain perception

cerebellum

attached to the brainstem; crucial for motor coordination and control; participates in some types of learning

pons

contains sensory and motor nuclei; origin of some cranial nerves

medulla

marks transition from brain to spinal cord; drives essential processes such as respiration and heart rate; origin of some cranial nerves

the brain and spinal cord are surrounded by three protective membranes...

the meninges:

dura mater - tough outermost layer

pia mater - delicate innermost layer

arachnoid membrane - lies between other two; filled with cerebrospinal fluid

meningitis

an acute infection of the meninges

meningiomas

tumors formed in the meninges

ventricular system

series of chambers filled with cerebrospinal fluid

lateral ventricle

in each hemisphere extends into all four lobes and is lined with the choroid plexus, a membrane that produces cerebrospinal fluid

CSF flows into the ventricle

at the midline, then into the fourth ventricle where it exits to circulate over the brain and spinal cord

the brain has a glymphatic system

that drains waste in cerebrospinal fluid-derived fluids during sleep

besides cerebrospinal fluid, the brain depends on an ample supply of oxygenated blood from:

the cerebral arteries

stroke is caused by:

the rupture or blockage of blood vessels, leading to insufficient oxygen supply

common warning signs of stroke:

sudden numbness or weakness

altered vision

dizziness

severe headache

confusion or difficulty speaking

histology is the study of:

tissues

cell bodies can be visualized using:

Nissl stains

Golgi stains:

completely label only a few cells

autoradiography can reveal:

cells that exhibit a specific property

tract tracers help

visualize neural pathways

computerized axial tomography (CAT or CT)

a measure of X-ray absorption at several positions around the head

CT scans...

generate an anatomical map of the brain based on tissue density

magnetic resonance imaging (MRI)

higher resolution images, fewer damaging effects than CT

functional MRI (fMRI)

detects small changes in brain metabolism, such as oxygen use, in active brain areas

fMRI can show how networks of brain structures collaborate

positron emission tomography (PET)

gives images of brain activity

identifies which brain regions contribute to specific functions

magnetism can be used to study

brain activity

transcranial magnetic stimulation (TMS)

briefly stimulates discrete cortical regions. scientists can then record observed changes in behavior

magnetoencephalography (MEG)

measures the tiny magnetic fields given off by active neurons during cognitive processing

three types of studies are used to research the biological bases of behavior:

somatic intervention - manipulating the body may affect behavior

behavioral intervention - manipulating the behavior may affect the body (and the brain)

correlation - measure how closely the body and behavior measures covary

a control group

is identical to the experiment group except that they do experience any altercation or treatment

in a within-subjects experiment

the control group is the same set of subjects tested before alteration or treatment

in a between-subjects experiment

the experimental group is compared to a separate control group that has been treated identically except for the manipulation

somatic intervention

alteration or function to see how behavior is altered

independent variable

the structure or function that is being altered

dependent variable

the response that is measured, such as behavior

behavioral intervention

intervention of a behavior to see how structure or function is altered

behavior is the independent variable

body changes are dependent variables

correlation

compares how much a body measure varies with a behavioral measure

negative correlation

if one measure goes up while the other goes down

positive correlation

if both measures increase or decrease together

a correlation experiment may show an association between variables, but cannot prove

causality

reductionism

a method that breaks a system down into increasingly smaller parts in order to understand it

levels of analysis

the scope of an experimental approach, which ranges from social interaction down to the molecular level