Chapter 4: The Brain and Behaviour

Question 1

Define NEURONS:

Answer 1

• Neurons: specialised cells which are the basic building blocks of the nervous system
• Link together in circuits
• Can vary greatly in size and shape
• Function to receive, process and send messages
• Neurons generate electricity that creates nerve impulses
• Release chemicals that communicate to other neurons, muscles and glands

Question 2

What are the three main parts of the neurons?

Answer 2

1. Cell Body
2. Dendrites
3. Axon

Question 3

Explain the CELL BODY:

Answer 3

o Cell body

 Also “soma” contains biochemical structures needed to keep the neuron alive, nucleus carries genetic information that determines how the cell develops and functions

 Surface of cell body has receptor areas that can be directly stimulated by other neurons.

Question 4

Explain the DENDRITES

Answer 4

o Dendrites

 Emerge from the cell body in branch-­‐like fibres. They are specialised receiving units that collect messages from neighbouring neurons and send them on to the cell body where information is combined and processed.

Question 5

Explain the AXON:

Answer 5

 Conducts electrical impulses away from the cell body to other neurons, muscles or glands

 Branches out at its end to form axon terminals which may connect with dendrites from numerous neurons

Question 6

What are GLIAL CELLS?

Answer 6

Glial cells of the peripheral nervous system include SHWANN CELLS, which form the MYELIN SHEATH, and SATELLITE CELLS, which provide nutrients and structural support to neurons.

Question 7

GLIAL CELLS PURPOSE?

Answer 7

• Supported in function by glial cells (Greek roots for “glue”)
o Surround neurons and hold them in place
o Manufacture nutrient chemicals that neurons need
o Absorb toxins and waste that would damage/kill neurons
o Send out long fibres to guide newly developed neurons to targeted places during prenatal development, as new neurons are formed through cell division

Question 8

How do nerve impulses occur in 3 steps?

Answer 8

• How nerve impulses occur: (3 steps)

o 1. At rest, neuron has electrical resting potential due to – and + ions distributed inside/outside the neuron

o 2. Action potential or nerve impulse produced when stimulated – i.e. ions flow in and out through cell membrane and reverse electrical charge of resting potential

o 3. Original ionic balance is restored, neuron is again at rest

Question 9

What is the RESTING POTENTIAL?

Answer 9

• RESTING POTENTIAL:

o 1. Neurons surrounded by body fluids – separated by membrane

o 2. Membrane a sieve with ion channels which allow some substances in, limit others

o 3. Nerve impulse = flow of ions

• ***** Outside membrane Na+ and Cl-­‐, inside K+ and negatively charged protein ions
• ***** High Na+ concentration outside and high protein ion concentration inside
• ***** This creates a difference of 70mV and is the neurons resting potential

Question 10

What is ACTION POTENTIAL?

Answer 10

• ACTION POTENTIAL:

o 1. -­‐70mV to +40mV when the neuron is stimulated – action potential/nerve impulse

o 2. When neuron is stimulated, sodium channels open up

o 3. Sodium ions flood through channels attracted by negatively charged protein ions: creates state of depolarisation

o 4. Restores to resting potential when positively charged potassium ions flow out through channels

Question 11

What is ABSOLUTE REFRACTORY PERIOD?

Answer 11

o 1. Period once impulse has passed a point along the axon

o 2. When potassium ions are flowing out

o 3. Membrane not excitable, cannot discharge another impulse

Question 12

What is GRADED POTENTIALS?

Answer 12

graded potentials are when changes in the negative resting potential do not reach the -­‐50mV action potential threshold required, and thus do not create an action potential at all

Question 13

What is the MYELIN SHEATH?

• Structure and Purpose

Answer 13

• Myelin sheath: a whitish, fatty insulation layer derived from glial cells during development.

1. Covers many axons that transmit through brain and spinal cord
2. Interrupted at regular intervals by Nodes of Ranvier
3. Axons lacking myelin sheath – “fuse-­‐like” transfer of action potential
4. Myelinated axons – Nodes of Ranvier allow more frequent depolarisation and thus higher electrical conduction speeds

Question 14

How do neurons talk: STEP 1

Answer 14

Step 1
• Regulating ion flow in and out of the cell body and creates a resting membrane potential

• Meaning a voltage difference between the inside and outside of the neuron ****(-­‐75 millivolts)
• Meaning a teeny-­‐tiny battery

Question 15

How do neurons talk: STEP 2

Answer 15

Step 2:
• Excitatory and inhibitory messages from other neurons (via dendrites) change resting potential

• If enough excitatory messages are received, resting potential will excess a threshold ****(~-­‐55mv)

Question 16

How do neurons talk: STEP 3

Answer 16

Step 3:
• This initiates a rapid depolarization at the axon hillock which creates a current that moves down the axon
• This current is called an action potential

Action Potentials:
• Depolarization and repolarization occurs in less than ***0.02 seconds

• Depolarization “overshoots” and repolarization “undershoots”
• This slows down the action potential and leads to a refractory period of about **0.0015 seconds

Question 17

How do neurons talk: STEP 4 - The problem and Solution(s)

Answer 17

Step 4: the Problem
• For a number of reasons, the charge sent down the axon wouldn’t travel far enough or fast enough if not for some help

Step 4: The solution (PART I):
• One form of help comes form the oligodendrocytes (a type of glial cell) that form the myelin sheath
• The myelin sheath prevents the ions from escaping

Step 4: The solution (PART II):
• The Nodes of Ranvier act like the amplifiers that re-­‐generate the action potential

Question 18

How do neurons talk: STEP 5

Answer 18

Step 5:
• Ultimately, the current reaches the end of the axon

• While communication within the neuron is purely electrical this is not how it goes between neurons
• Arrival of action potential at ***presynaptic axon terminal triggers release of chemicals (neurotransmitters)

Question 19

How do neurons talk: STEP 6

Answer 19

Step 6:
• Neurotransmitters enter the synaptic cleft and float through cerebrospinal fluid

• Some then bind with receptors on dendrites of adjacent neurons

Question 20

How do neurons talk: STEP 7

Answer 20

Step 7:
• Depending on the neurotransmitter and the dendrite, two things can happen…

***** Excitatory post synaptic potential (ESSP): depolarizes postsynaptic neuron

**** Inhibitory post-­‐synaptic potential (ISSP): hyperpolarizes postsynaptic neuron

Question 21

What is the Synaptic Space

Answer 21

• Synaptic space: a tiny gap between the axon terminal and the next neuron

Question 22

What are NEUROTRANSMITTERS?

Answer 22

• Neurotransmitters: chemical substances that carry messages across the synaptic space to other neurons, muscles or glands

Question 23

5 STEPS in the PROCESS of CHEMICAL COMMUNICATION:

LIST

Answer 23

• 5 steps in this process of chemical communication:

1. Synthesis
2. Storage
3. Release
4. Binding
5. Deactivation

Question 24

Explain the 5 steps of CHEMICAL COMMUNICATIONS:

Answer 24

• 1. Synthesis: transmitter molecules formed inside neuron
• 2. Storage: molecules stored in synaptic vesicles, or chambers within axon terminals
• 3. Release: when action potential comes down axon, vesicles move to surface of axon terminal and molecules are released into fluid-­‐filled space between axon of presynaptic (sending) neuron and membrane of postsynaptic (receiving) neuron

• 4. Binding: molecules cross synaptic space and bind to receptor sites, large protein molecules embedded in the receiving neuron’s cell membrane. Transmitters will match only a particular receptor molecule in the postsynaptic membrane.
o Chemical reaction occurs during binding: two effects on receiving neuron
o Excitation or inhibition
 **Excitation: sodium channels open and depolarisation, creating a graded potential or action potential
. ***Inhibition: potassium ions or negative chloride ions flow, increasing neuron’s negative potential and making it harder to fire the neuron.

• 5. Deactivation: once a neurotransmitter molecule binds to its receptor, it continues to excite or inhibit the neuron until it is deactivated or shut off.
o **some are broke ndown by other chemicals

o **some are deactivated by reuptake, where transmitter molecules are taken back into the presynaptic axon terminals

Question 25

What are NEUROMODULATORS?

Answer 25

• Specialised neurotransmitters: neuromodulators

o circulate through the brain and increase or decrease sensitivity of neurons to their specific transmitters

 e.g. endorphins

Question 26

What re the 3 major neuron types:

Answer 26

• 3 major neuron types:

o Sensory neurons – carry input messages from sense organs to spinal cord and brain

o Motor neurons – transmit output impulses from the brain and spinal cord to body’s muscles and organs

o Interneurons – perform connective or associative functions within the nervous system

Question 27

Define Peripheral Nervous System:

Answer 27

• Peripheral nervous system:

contains all neural structures that lie outside of the brain and spinal cord. Neurons are interneurons.

Question 28

How can the Peripheral Nervous System be broken down?

Answer 28

PERIPHERAL NERVOUS SYSTEM

1. Somatic Nervous System
2. Autonomic Nervous System
   • — Sympathetic Nervous System
   • — Parasympathetic Nervous System

Question 29

Explain the Somatic Nervous System:

Answer 29

Somatic nervous system:

sensory neurons specialised to transmit messages from sensory receptors, and motor neurons. The axons of these nerves group together to form sensory nerves and motor nerves.
Specialises in voluntary muscle action

Question 30

Explain the Autonomic Nervous System:

Answer 30

 Autonomic nervous system: regulates body’s internal environment; controls involuntary functioning i.e. muscles forming the heart, blood vessels, lining of stomach and intestines, and glands. Thus it regulates respiration, circulation and digestion

***** CAN BE SEPARATED INTO 2 PARTS

1. Sympathetic nervous system
2. Parasympathetic nervous system

Question 31

Sympathetic vs Parasympathetic nervous system

Answer 31

Sympathetic nervous system (generally activates; speeds up)

Parasympathetic nervous system (generally inhibits; slows down)

(part of the autonomic nervous system)

Question 32

What is the CNS?

PARTS?

Answer 32

• Central nervous system (CNS):

connects most parts of the peripheral nervous system (PNS) with brain

SPINAL CORD AND BRAIN

Question 33

What is the Spinal Cord?

Answer 33

Spinal cord: where most nerves enter and leave central nervous system. Vertebrae (bones of the spine) protect the spinal cord’s neurons.

Spinal reflexes, or simple stimulus-­‐response sequences, can be triggered at the level of the spinal cord without any involvement of the brain.

This significantly reduces reaction time in quick situations, e.g. touching something hot.

Question 34

What is the Brain?

Answer 34

Brain: protein, fat and fluid. The primary control of the nervous system. It can be studied using neuropsychological testing, destruction and stimulation techniques (removal of brain portions or chemical stimulation of an area), electrical recording which stimulates and records brain activity (e.g. the electroencephalograph), and brain imaging (CT scans and MRIs for visualising brain structure, PET scans and fMRIs to view brain activity).

Question 35

What is the BRAIN PARTS?

Answer 35

1. HINDBRAIN
2. MINDBRAIN
3. FOREBRAIN

Question 36

What is the HINDBRAIN? PARTS?

Answer 36

Hindbrain: supports vital life functions -­‐ most primitive level.

• See: cerebellum, spinal cord, brain stem, medulla, pons (diagram)

Question 37

What is the MIDBRAIN? Parts?

Answer 37

Midbrain: contains clusters of sensory and motor neurons. Contains relay centres for visual and auditory systems.

• Constituted by reticular formation

Question 38

Whta is the Forebrain? Parts?

Answer 38

Forebrain: brains most advanced portion. Structures include:

1. thalamus
2. hypothalamus (connected with the endocrine system)
3. the limbic system (involved in memory, and coordinates behaviours to satisfy urges that arise in the hypothalamus – hippocampus, amygdala),
4. Cerebral cortex (outer layer of brain, cerebrum) which is divided into the frontal, parietal, occipital and temporal lobes; primary motor cortex, somatic sensory cortex, wernicke’s area, broca’s area, association cortex, frontal lobes, and the prefrontal cortex (see figures 4.14 and 4.15 on page 115)
   • *****Primary motor cortex: controls muscles involved in voluntary body movements. Each hemisphere governs movement on the opposite side of the body (nerve tracts from the motor cortex cross over at the level of the medulla)

• **Somatic sensory cortex: receives sensory input that gives rise to sensations of heat, touch and cold, and sense of balance and body movement.
• **Wernicke’s area: temporal lobe. Primarily involved in speech comprehension.
• **Broca’s area: in the frontal lobe. Involved in production of speech through connections with the motor cortex region that controls the muscles used in speech.
• **Association cortex: perception, language and thought – important mental functions. 75% human cerebral cortex. Agnosia, the inability to identify familiar objects, occurs with damage to his area.
• **Frontal lobes: 29% of cortex. Involved in emotional experience
 Prefrontal cortex: region of the frontal cortex. Seat of executive functions such as goal setting, judgement, strategic planning and impulse control (Phineas gage primary example of effects of damage to this area)

Question 39

Whta is CORPUS CALLOSUM?

Answer 39

• Corpus callosum: neural bridge consisting of white myelinated fibres that acts as a major communication link between the two hemispheres and allows them to function as a single unit.

Question 40

What is LATERALISATION?

Answer 40

• Lateralisation: relatively greater localisation of a function in one hemisphere or the other.

 Right hemisphere accounts for mental imagery, musical and artistic abilities and the ability to perceive and understand spatial relations
 Left… ?

• We have an optic chiasma over which the fibres of the optic nerve for each eye cross over and travel to the opposite brain hemisphere. This produces a unified image.

Question 41

What is NEURAL PLASTICITY?

Answer 41

• Neural plasticity: the ability of neurons to change in structure and function

• Brain loses some plasticity over time
*****greatest amount of brain synapses at birth

• Production of new neurons in nervous system is called neurogenesis.
• Stem cells may hold the key to countering the effects of aging on brain functioning – but further research is required.

Question 42

How experience influences brain development: examples - NEURAL PLASTICITY

Answer 42

1. Chronic alcoholism inhibits the production of new neural connections in the hippocampus – this impairs learning, memory and other cognitive functions
2. Life stress has a similar negative effect on neuron formation in the brain, thereby causing or maintaining clinical depression
3. Cultural factors – e.g. Chinese language based on pictures means less left-­‐hemisphere lateralisation of language amongst native Chinese speakers.

Question 43

What is Endocrine System?

Answer 43

• Endocrine system: consists of numerous hormone-­‐secreting glands distributed throughout the body
*****conveys messages using hormones, chemical messengers that are secreted from its glands into the bloodstream, rather than neurons

• hormones influence our development, capacities and behaviour before we’re born

Question 44

What is the ADRENAL GLANDS?

Answer 44

• Adrenal glands:
twin structures perched atop the kidneys that serve as hormone factories producing and secreting about 50 different hormones that regulate many metabolic processes within the brain and other parts of the body

****produce dopamine as well as several stress hormones

Question 45

SIZE OF THE BRAIN MATTER?

Answer 45

• There has been steady growth in the brain capacity and size of the brain cavity over the past 3 million years
• Ratio of the size of the brain relative to the size of the body; the smaller the ratio the more complex the organism

Question 46

What is GROSS STRUCTURE?

Answer 46

• Two asymmetric hemispheres connected by “corpus callosum”
• Sulcus are like guidelines, prominent valley that acts like a landmark in the same way that rivers separate countries
• The pre-­‐occipital notch works in the same way as a dent

Question 47

WHAT IS THE DETAILED STRUCTURE(S)

Answer 47

• Cytoarchitectonics: division of the brain based on differences in structure of stained tissue
• Korbinian Brodmann (1868-­‐1918)
• He we would stain the difference sections of the brain
• Making a map of the brain by dividing it up based upon how the cells look.
• The structure is different as the function is different

Question 48

Explain the BRAIN at CELLULAR STRUCTURE?

Answer 48

• The Brain: consists of glial cells and neurons

• Neurons: process information
 100 billion in adult brain
 100 trillion neuronal connections

• Neurons: Performs to process information quickly; have a lot of raw computational power
• Glial Cells: provide structure to the brain, carries off waste, protect the brain from foreign objects, the support crew

Question 49

Parts of the Brain and What does it do?

FRONTAL CORTEX

Answer 49

Frontal Cortex ‘Executive Function’ such as planning, inhibition, working memory

Question 50

Parts of the Brain and What does it do?

CORTEX: MOTOR

Answer 50

Cortex: Motor Contains 3 areas:

1. PRIMARY: planning
2. PRE-­‐MOTOR: selection of movements
3. SUPPLEMENTARY: bimanual coordination

Question 51

Parts of the Brain and What does it do?

CORTEX: SOMATOSENSORY

Answer 51

Cortex:
Somatosensory

Responsible for processing pressure, pain, temperature
Feedback about things happening to your body

Question 52

Parts of the Brain and What does it do?

CORTEX VISUAL

Answer 52

Cortex: Visual

Processes form, motion, orientation, color, object identification; Area 17
Lowest areas contain accurate spatial “map” of visual world

Question 53

Parts of the Brain and What does it do?

CORTEX AUDITORY

Answer 53

Cortex: Auditory

Processes sound frequency, location, music, prosody (the tone of language, the way we say
words), oral language  helps decipher intent and meaning

Question 54

Parts of the Brain and What does it do?

lLIMBIC SYSTEM

Answer 54

Limbic System

“Older mammalian brain”

Involved in key aspects of memory, reward and emotional processing

Question 55

Parts of the Brain and What does it do?

BASAL NUCLEI

Answer 55

INVOLVED IN

 Motor suppression
 Motor learning
 Motor response selection

Enacts the functions of the motor cortex and desire to move

Question 56

Parts of the Brain and What does it do?

CEREBELLUM

Answer 56

1. Coordinates complex movement
2. Stores procedural memories (motor learning)
3. Balance and posture; learned reflexes

Question 57

Parts of the Brain and What does it do?

BRAIN/HINDBRAIN

Answer 57

Regulates breathing, basic autonomic functioning; sleep/wakefulness

Question 58

What are traditional methods?

Answer 58

• 1. Lesions: brain tissue can be damaged by injury, stroke, disease or surgery
• 2. The Logic: “if area X does function Y, a lesion to X should impair function Y”
• 3. Problems:

a) Injury often extensive; i.e. it isn’t discrete
b) Impairment often extensive
c) “Compensatory” changes in other brain areas; the brain requires itself in response to injury, the brain becomes more adaptive to the lesion. The behaviour may be more a response to this rather than the lesion itself
d) Convenience sample

Question 59

What are modern methods?

Answer 59

Modern Methods:

• The logic: “to figure out what part of the brain does what, figure out where it’s active during a task”
• How to map activity:

a) Electrical activity (neurons)
b) Blood flow

Question 60

Define ELECTROENCEPHALOGRAM?

Answer 60

• Electroencephalogram: records electrical fields generated by groups of neurons firing action potentials

 Provides gross estimate of overall brain activity

Question 61

What is EVENT-RELATED POTENTIALS (ERPSs)

Answer 61

• Event-­‐related potentials (ERPs): Isolates activity due to a particular event from overall EEG

Question 62

FUNCTIONAL MAGENTIC RESONANCE IMAGING (fMRI):

Answer 62

Blood flow

• Functional Magnetic Resonance Imaging (fMRI): Imaging protons in hydrogen that are part of water molecules in the bloodstream; Resolution: ~ 1mm3

Question 63

How to isolate Activity?

Answer 63

How to isolate activity?
• FMRI measures whole-­‐brain activity. Which area is activated in response only to what I’m interested in?

Do activity of interest –> Measure blood flow Measure blood flow

Question 64

Explain Beyond Correlation:

Answer 64

Beyond Correlation:

• ERPs and FMRI are all correlative. How do we know activity causes behaviour
• Transcranial magnetic stimulation (TMS)

Question 65

How does TMS work?

Answer 65

How does TMS work? Electric current disrupts brain activity creating “virtual lesion”