Chapter 1: Brain Basics

CHAPTER 1 START

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"Nerve Center of the Body"

Brain

The brain contains roughly how many neurons

86 billion

Why can the brain multitask

It is split into many different specialized regions

Largest part of the brain

Cerebrum

The cerebrum is divided into two large, separate ______________________

Hemispheres

The surface of the cerebrum is a __________ __________ layer of ____________ _____________ called the _____________________ ________________

Cerebral Cortex

The deepest divisions of the cerebrum are used to identify separate _____________________

Lobes

What are lobes

Distinct regions that have characteristic functions

Location of the frontal lobes

Front of the brain, immediately above the eyes

What do the frontal lobes control? (7)

Voluntary Movements
Speech
(Short-term) Memory
Emotion
Planning
Problem-solving/logic
Personality

Location of the parietal lobes

Top of the brain, immediately behind the frontal lobes

What do the parietal lobes control? (3)

Integrate sensory signals from the skin
Process taste
Process some types of visual information

Location of the occipital lobes

Back of the brain

What do the occipital lobes control? (2)

Process visual information
Recognize colors and shapes integrate them into complex visual understanding

Location of the temporal lobes

On the sides of the brain, at and below the level of the eyes, behind the temples, roughly above the ears

What do the temporal lobes control? (2)

Some visual processing
Interpret auditory information

What is the hippocampus?

A region of the temporal lobes (beneath the cerebral cortex) that encodes new memories

What is the amygdala?

Deep structure within the temporal lobes that integrates memory and emotion

The hippocampus and amygdala are part of the _______________ system

Limbic

What is the limbic system?

A group of structures deep within the brain that help regulate emotion and motivation

Parts of the limbic system

hippocampus, amygdala, thalamus, hypothalamus

Integrates sensory information and relays it to other parts of the brain

Thalamus

Sends hormonal signals to the body through the pituitary gland

Hypothalamus

Forebrain (prosencephalon)

Limbic System structures + Cerebral Cortex

Midbrain location

Sits beneath the thalamus

midbrain (mesencephalon) functions (3)

Distinct groups of neurons that coordinate eye movements like blinking and focusing, trigger reflexes to sounds (sensorimotor reflexes)

Inhibit unwanted body movements

Help coordinate sensory input and motor output to manage fine motor control, ex. writing with a pen, playing an instrument

basal ganglia

collection of structures in the forebrain and midbrain that help to control complex body movements

Hindbrain function (3)

Plays roles in glucose regulation

Plays roles in sleep

Includes several regions that help control movement

Cerebellum location

Tucked under the occipital lobe, at the very back of the brain

Second-largest part of the brain in volume, contains over ________________ the brain's neurons

Cerebellum, 1/2

The cerebellum is __________ ______________, divided into ________ _______________

deeply folded, two hemispheres

Cerebellum functions (3)

Coordinates voluntary movements

Helps the brain learn new motor skills

Has roles in spatial and temporal perception

Pons location

Below the cerebellum

Pons function (2)

Influences breathing and posture

Medulla function

Carries nerve pathways connecting the brain to the spinal cord
Swallowing
Heart rate
Breathing

Structures of the hindbrain

Medulla, pons, cerebellum

Structures of the brainstem

Midbrain, pons, medulla oblongata

Primitive brain (wide spot in the hollow nerve cord) found in early invertebrates such as

the modern lancelet, Amphioxus

Commonalities between human brains and early ancestor brains (2)

Both began as a simple tube

Both contain specialized regions/divisions where neurons process specific kinds of information

In early vertebrates, the "brain" end of the nerve cord developed _____________ distinct bulges which became the __________________

3, forebrain, midbrain, hindbrain

in the forebrain, the region able to detect chemicals expanded to form the _________________, and light sensing regions expanded and began processing more _______________________ _____________________ _______________________

olfactory bulbs, complex visual signals

The ________________ appeared as the hindbrain and expanded the regions that control _________________ movements and orient the body in space

cerebellum, escape

What led to the formation of the two cerebral hemispheres

New types of neurons and regions that could rapidly process visual and auditory information caused the forebrain to balloon out

In early mammals, __________________ tissues in the cerebrum and cerebellum expanded and packed neurons into layers, generating more complex tissues with increased processing power

cortical

Information moves from one region of the brain to another via _______________________

chains of neurons that can transmit signals over long distances

Nerve fibers of region-spanning neurons that form distinct neurons are called _________________ __________________

nerve tract

corpus callosum

Major nerve tract, connects left and right cerebral hemispheres

smaller anterior commissure

Major nerve tract, transmits signals between the left and right temporal lobes

A group of nerve tracts connecting a series of regions in the brain is called a _______________ ______________

Neural network

Neural networks route signals through the brain along a ______________ pathway, analyzing and organizing different types of information within ____________________

linear, fractions of a second

cells in the retina that trigger electrical signals in response to specific wavelengths of light

photoreceptors

in which lobe is the primary visual cortex

occipital lobe

What is a thalamocortical loop?

a two-way circuit that connects the thalamus with parts of the cortex and back. As neuronal signals loop through the thalamus and cortex, they produce rhythmic, oscillating, electrical patterns

Electrical patterns produced by looping neuronal signals can be detected by an _____________

Electroencephalograph (EEG)

The patterns detected by an EEG are commonly called

brain waves

How many distinct types of brain waves are found?

4

Your awake brain typically produces _______________ and _______________ waves

Alpha, beta

Alpha waves originate mainly in the _______ and _________ lobes when your brain is ___________ and eyes are ______________

parietal, occipital
relaxed, closed

Alpha wave frequency range

between 8 and 13 Hz

Beta waves are typically produced by the ____________ and ___________ regions of your brain when it ___________________ or _____________________

frontal, parietal
processes sensory input, concentrates on a task

Beta wave frequency range

between 14 and 30 Hz

Theta waves and delta waves are typical of _______

sleep

Theta wave frequency range

4 to 7 Hz

Delta wave frequency range

less than 3.5 Hz

Delta waves occur during

Deep (NREM) sleep

Alpha and delta waves are typically ____________________ than beta or theta waves

of higher amplitude

When measured with electrodes, alpha and delta wave signals are in the range ______________

20-200 μV

When measured with electrodes, beta and theta wave signals are in the range ______________

5-10 μV

Spinal tracts

chains of neurons that pass signals through the brainstem and the spinal cord

Signals in the spinal tracts either travel upward from ____________________ to the __________ and parts of the cortex that interpret touch and pressure; or they travel downward from brain regions that induce __________, passing through the _____________ and spinal cord before projecting to the body's muscles.

sensory receptors in skin and muscles, thalamus
movement, medulla

For example, the brain's _________ _________ are part of a feedback loop that takes information from cortical areas that elicit movement and produces signals that feed back to the cortex to excite or inhibit specific movements. This is an example of the integration of _____________ and ____________ signals

basal ganglia
sensory, motor

Loops that connect the ______________ to the _____________ influence the timing and strength of motor signals

brainstem, cerebellum

Networks that loop the hippocampus into sensory cortex pathways help your brain analyze whether environmental signals are ___________________________________________

familiar or are part of a new situation

Networks linking the hippocampus to the thalamus and hypothalamus allow your memory to influence _____________________________________________

conscious behavior as well as unconscious physiological responses.

Reflex loops are circuits _____________________________________________

eliciting actions well before thoughts

Reflex actions are controlled locally by information going in and out of the ______________________ or _________________ regions of the brain, and never __________________________

spinal cord, subcortical regions
reach the cortex

Neural circuits are arranged in ____________, as each neuron forms connections with cells in the layers above and below.

columns

The neurons in a column form a _____________ __________, and signals that enter the circuit travel down that _____ from one neuron to the next. Each time the signal is fed forward, it is ____________ in some way, building outputs that encode ________ information

single chain, chain
transformed, complex

Neuroscientists think each column in the cortex is dedicated to ________________________________________________

One very specific processing task

Neurons in a circuit have other connections to neurons in ____________________. Since every neuron behaves like a microprocessor, summing all the signals it receives before sending one of its own, the strength of signals from neighboring circuits can ____________________________. This dynamic organization may help the brain _______________________________

neighboring columns
dynamically shift a neuron's response
react flexibly to different situations.

Individual neurons are either ______________ or ______________

excitatory, inhibitory

about ____% of neurons are excitatory and ____% are inhibitory

80, 20

Excitatory neurons fire signals that _________________________________

push their neighbors toward firing

The most common type of excitatory neuron in the cerebral cortex is the _________________________________

pyramidal cell

Each pyramidal cell has ________ sets of branched dendrites that collect signals from neurons in every layer of the cortex.

2

The __________________________ axon of a pyramidal cell sends a single electrical signal to multiple destinations.

multi-branched

Inhibitory neurons fire signals that _____________________________________

suppress the activity of neighboring neurons and regulate the activity of a circuit

True or false: Every neural circuit contains both excitatory and inhibitory neurons

True

Neurons that pass signals forward through a circuit and eventually send outputs to other parts of the brain tend to be (i/e), while (i/e) neurons are typically local and often loop their responses back to earlier segments of a circuit.

excitatory, inhibitory

Seizure disorders like epilepsy could be caused by ____________________________________________

imbalances in the activity of excitatory and inhibitory neurons

Feed-forward inhibitory circuit:

Inhibitory interneurons connect neighboring neural circuits in such a way that excitatory signals in one column simultaneously send inhibitory signals to adjacent columns, reducing their activity.

Feedback inhibition:

Neurons send signals to their downstream excitatory neighbors and to interneurons that reach back and inhibit preceding layers of the same circuit.

Networks where neurons inside interconnected circuits send feedback signals to one another

Recurrent neural networks

Neuron

The functional unit of neural circuits, transmits electrical signals to other nerve cells, muscles, or glands

All neurons have the following major components (3):

Dendrites
Soma/cell body
Axon

Cell body (soma)

contains the neuron's nucleus and most of its cytoplasm, along with molecular machinery for building and transporting proteins critical to the cell's function.

Dendrites

Branched projections that extend from the cell body and collect incoming signals from other neurons.

Axon

Extension from the cell body that the neuron's electrical signal travels down; may branch before ending in axon terminals, where the signal is passed across a synapse to other cells.

Axons can range from ________________________ long to _______________________

Fractions of a centimeter, more than a meter