NeuroscienceChapter 2

Parts of the BrainA. The Lobes – divide the brain into 4 major sections by

fissures1. Frontal Lobe – area of the brain associated with higher

mental abilities, movement, personality and the sense of smell

Contains the Motor Strip – portion of the brain that controls body movement – can be stimulated through electrical impulse Importance to the body denotes designation of space in the MS

Frontal Association Area Interprets & evaluates your environment – what is going on, what

to feel, makes sense of things going on around you Size reflects intelligence Damage to this portion can create serious problems with a persons

personality (inappropriate emotions, socially unacceptable behavior, fewer inhibitions, failure to make long-term plans, easily distracted, difficulty understanding a string of facts or events)

The Lobes Cont.1. Parietal Lobe – Portion of the brain where

body sensations register (touch, temperature, pressure etc)

Contains the Sensory Strip – provides and registers sensation

2. Occipital Lobes – responsible for processing and interpreting visual information

When damaged it effects what and how well a person can see

3. Temporal Lobe – contains centers for hearing and some language functions

The Hemispheres• Hemispheres – The sides of the brain divided by a

large lengthwise fissure, both hemispheres work together on most tasks

• Corpus Callosum – connects and allows for communication between the right and left hemisphere▫When this is cut most communication between the 2

halves is cut off• Dominance – this is the side of the brain that is

preferred over the other▫The hemisphere that is dominant controls most

actions and fine motor skills▫ If you are left handed you are right brain dominant

etc

Hemispheres cont.• Left Hemisphere Tasks – local view

▫ Handles verbal and speech material, like encoding and syntax some logic and writing, superior at judging time, math, rhythm & coordinating complex movements like those associated with speech

▫ Mainly involved in analysis and processing information sequentially

• Right Hemisphere Tasks – global view▫ Can produce only basic speech and numbers▫ Deals with objects in space, recognizing patterns, faces,

and melodies, putting together a puzzle and drawing a picture, some mathematical reasoning

▫ Helps express emotions and detect emotions of others▫ Chances are these people will be better at nonverbal

activities, specializes in imagery▫ Processes material simultaneously and holistically

The Cerebrum and the Cerebral Cortex1. The outermost layer of the brain – the gray matter2. Includes hemispheres, lobes and the frontal

association area 3. Controls very high-level thought and takes up

2/3rds of the brains nerve cells (100 billion)4. Responsible for voluntary movements, sensations,

learning, remembering, consciousness etc.5. Corticalization – the increase in the size and

wrinkles of the brain▫small correlation between brain size and

intelligence (not between humans & humans but humans and other animals)

The Lower Brain

1. The Lower Brain - communicates back and forth with the cerebral cortex for non-automatic human responses

2. The Thalamus – acts as a sensory relay station sending and receiving information to other parts of the brain (vision, hearing, taste & touch) damage can cause blindness, deafness, etc (not smell)

3. The Cerebellum – primarily regulates posture, muscle tone & muscular coordination

▫ Stores memories related to skills and habits (class schedules, driving directions)

▫ Damage – walking, running, playing catch are impossible, area of the brain where degenerative diseases effect coordinated motor function

The Lower Brain Cont.4. The Hypothalamus – control center for emotions and

basic motives - helps control rage, pleasure, hunger and sexual desire, temperature control

5. Reticular Activating System – works to catch nerve impulses from the brain to the body and back

▫Affects your alertness, sorts & prioritizes nerve impulses, controls reflexes involved in breathing, sneezing, coughing, and vomiting, and affects muscle tone, posture, and movement of the head, eyes, face & body

▫Bombards the cortex with stimulation keeping it active and alert

Brain Communication

A. Neuron – the nerve cell of the brain1. Dendrite – short fibers that act as

receptors, receiving messages from other nerve cells

2. Axon – Long single extension of a neuron, covered with myelin sheath to insulate and speed up messages through neurons.

B. Synapse – space between the axon of one neuron and the dendrite of another neuron

3. Vesicle – bubble like containers that hold chemical molecules called neurotransmitters

Communication Demo

http://youtu.be/FR4S1BqdFG4

Action Potential

A neural impulse. A brief electrical charge that

travels down an axon and is generated by the

movement of positively charged atoms in and out of channels in the axon’s

membrane.

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Depolarization & Hyperpolarization

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Depolarization: Depolarization occurs when positive ions enter the neuron,

making it more prone to firing an action potential. Hyperpolarization occurs when negative ions enter the neuron, making it

less prone to firing an action potential.

Threshold

Threshold: Each neuron receives depolarizing and hyperpolarizing

currents from many neurons. When the depolarizing current (positive ions) minus

the hyperpolarizing current (negative ions) exceed minimum intensity

(threshold) the neuron fires an action potential.

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Action Potential Properties

All-or-None Response: When the depolarizing current exceeds the

threshold, a neuron will fire. If the depolarizing current fails to exceed the

threshold, a neuron will not fire.

Intensity of an action potential remains the same throughout the length of the

axon.

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Synapse

Synapse [SIN-aps] a junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving

neuron. This tiny gap is called the synaptic gap or cleft.

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Neurotransmitters

Neurotransmitters (chemicals) released

from the sending neuron travel across the synapse and bind to receptor sites on

the receiving neuron, thereby influencing it to

generate an action potential.

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Reuptake

Neurotransmitters in the synapse are

reabsorbed into the sending neurons

through the process of

reuptake. This process applies the

brakes on neurotransmitter

action.19

Lock & Key Mechanism

Neurotransmitters bind to the receptors of the receiving neuron in a key-lock

mechanism.

Agonists

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Antagonists

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Neurotransmitters

The Spinal Cord

1. The neurons in the spinal cord are short, direct and powerful.

2. Has fewer synapses – shorter time for information to be received and an action to occur

3. Reflex – activation of the muscle(s) before the message is received by the brain (dropping a baby)

The Endocrine System

• The Pituitary Gland – small bean shaped gland attached to and controlled by the hypothalamus▫ Responsible for sending messages to other glands to activate

them▫ Responsible for determining the height of the person▫ The gland creates a growth hormone which appears in the

body’s system sporadically resulting in on and off growth spurts

▫ Can be effected by the environment and diet of the individual

• Thyroid Gland – located in the neck this gland controls a persons metabolism▫ This affects the rate a which a person’s body operate, inactive

thyroid = a sluggish person, a overactive thyroid = jumpy and hyper person

• The Adrenal Gland – located on the right and left side of the body above the kidneys▫Responsible for putting adrenaline in to the

bloodstream Affects us by increasing breathing, blood pressure,

muscles tension & energy level▫Will also release a chemical that allows for the

faster clotting of blood▫This happens during testing or any other high

anxiety time (fight or flight reaction) TIP: to decrease test anxiety force yourself to take slow

deep breaths, this will stimulate brain activity instead of shutting it down to prepare for an emergency

The Endocrine System cont.

• The Gonads – sex glands located in the testis in males and the ovaries in females▫Androgen – the male hormone that stimulates the

growth of hair, the deepening of the voice and the production of sperm Starts the sex drive of both males and females Sex drive is taken over by the cortex which allows us to

associate other emotions like love and caring with the act of intercourse

▫Estrogen – the female hormone that causes the production of eggs the enlargement of the mammary glands and the menstrual cycle to begin Both of these hormones are produced in the gonads and

released during the middle teenage years

The Endocrine System cont.

The Nervous System

•The nervous system is our body’s electro-chemical information network (interstate highway)▫Central Nervous system – includes our

brain and spinal cord▫Peripheral Nervous system – links the

CNS with the body’s sense receptors, muscles and glands. (Broken down further)

Types of Neurons

•Axons – are grouped & bundled as cables that shoot messages back and forth along our nerves▫Sensory neurons - gather and send info

to the CNS

▫Motor Neurons – sends messages from the CNS to the body’s tissues and muscles

▫Inter Neurons – communicate between the sensory neurons and motor neurons

Peripheral Nervous System

•Somatic Nervous System – controls voluntary skeletal muscles

•Autonomatic Nervous System – controls involuntary glands and muscles, like those associated with our internal organs▫Sympathetic – arouses, alarms, enrages or

challenges you (Fight or Flight) accelerates your blood pressure, heart rate, slows digestion, raises blood sugar, creates persperation

▫Parasympathetic – conserves or calms the body, (Rest & Digest) decreases HR, BP, BS, etc

The Brain’s Plasticity

The brain is sculpted by our genes but also by our experiences.

Plasticity refers to the brain’s ability to modify itself after some type of injury or

illness.

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Our Divided BrainOur brain is divided into two

hemispheres. The left hemisphere processes reading,

writing, speaking, mathematics, and comprehension skills. In the 1960s, it was

termed as the dominant brain.

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Splitting the BrainA procedure in which the two hemispheres of the brain are isolated by cutting the connecting fibers

(mainly those of the corpus callosum) between them.

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Corpus Callosum

Ma

rtin M

. Ro

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Courtesy of Terence W

illiams, U

niversity of Iowa

Split Brain Patients

With the corpus callosum severed, objects (apple) presented in the right visual field can be named. Objects (pencil) in the left

visual field cannot.

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Divided Consciousness

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Try This!

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Try drawing one shape with your left hand and one with your right hand,

simultaneously.B

BC

Non-Split Brains

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People with intact brains also show left-right hemispheric differences in mental

abilities.

A number of brain scan studies show normal individuals engage their right

brain when completing a perceptual task and their left brain when carrying out a

linguistic task.

Now Try This!

1. Rotate your dominate hand in 1 direction and at the same time rotate the opposite foot in the other direction.a. How difficult was that task? (scale of 1-5)

2. Next rotate your dominate hand in 1 direction while rotating the foot on the same side of your body in the other direction.a. How difficult was that task? (scale of 1-5)

3. Tap you right index finger rapidly while turning to a partner to recite the alphabet backwards.

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Hemispheric Processing

•When people are asked to name the large compositive letter, the H, there is more activity in the right hemisphere (holistic perception).

•On the other hand, when asked to name the small component letters, there is more activity in the left hemisphere.

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D DD DD DD DDDDDDDD DD DD DD D

Which Face is Happier?

• Most people choose the face on the left.

• Information from the left side of the picture goes to the right hemisphere which is dominant for interpreting emotional expressions.

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Brain Organization & Handedness

Is handedness inherited? Yes. Archival and historic studies, as well as modern

medical studies, show that the right hand is preferred. This suggests genes and/or prenatal factors influence handedness.

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Is it Alright to be Left Handed?

The percentage of left-handed individuals decreases sharply in samples of older

people (Coren, 1993).

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