Brain & Behaviour

Lectures 13, 14, 15

Why do Psychologists study the brain?
• Psychology is the study of behaviour and
mental processes.
• We need to know the BIOLOGICAL processes
that underlie COGNITION.
• Cognition refers to all aspects of intellectual
functions & processes: perception, thought,
imagination, intelligence, how we acquire knowledge,
memory, judgment, reasoning, problem solving, decision
making, comprehension, production of language etc.
Biological Organisation of Life
Atom
Molecule
Organelles
Cell
Tissue
Organ
Organ Systems
Organism
Population
Community
Ecosystem
Biome
Biosphere
 The Nervous System
• 2 main divisions: Central (brain and spinal cord) &
Peripheral (somatic and autonomic nervous systems)
Main functions:
• Relaying messages
(from the senses to and from the brain, making decisions, bodily
coordination & movements)

• Adapting and accommodating to changes in

both internal and external environments
 The Neuron
• Cells are the basic unit of living organisms.
• Our organ tissues are made up of different types of cells, and thus
they vary structurally (muscle tissue can be distinguished from bone
tissue for example).
• Neurons are the fundamental units of the nervous system designed
to transmit information throughout the body.
• Human babies are born w approximately 100 billion neurons.
Neurons do not multiply or regenerate. We start losing neurons
from the age of 25yrs onwards. In other organs, old cells get
destroyed and new ones are generated.
• Neurons are not connected to each other but their main function is
to communicate with each other.
• Information is passed from cell to cell via electrochemical signals.
Structure of the neuron
• https://media.geeksforgeeks.org/wp-
content/uploads/20230417135450/N
euron-structure.jpg
The structure of the neuron
Functions of the soma & dendrites
• Soma: This is the neuronal cell body containing the
nucleus and other organelles, e.g., Golgi body,
mitochondria, endoplasmic reticulum etc. These
organelles are responsible for protein synthesis and the
production of energy essential for the cell to function.

• Dendrites: The branching extensions of the soma are

dendrites. Dendrites receive information from other neurons
through electrochemical signals and allow their transmission
to the cell body.
 Functions of the axon & synapse
• Axon: The axon is the tube like structure that carries
electrical impulses from the soma to the axon terminals from
where chemical neurotransmitters are released into the
synapse that the next neuron picks up. Most axons are
covered with a protective fatty layer known as Myelin Sheath
which increases the speed of neuronal transmission.

• Synapse: The space between two neurons, the terminal of

1 neuron and the dendrites of the next neuron is the synapse.
Some synapses pick up electrical impulses others are designed
to pick up chemical signals.
Neuron types

• Sensory neurons
• Motor neurons
• Interneurons
 Neurotransmitters
• Chemical messengers that determine our body’s
functions. Everything we do or feel is determined
by the firing of these chemicals.
• Neurotransmitters can be passed from 1 neuron
to other neurons, or to muscles or glands.
• An individual can have 30-100 active
neurotransmitters but 95% behaviours are
controlled by approximately 5-6.
• Dopamine, serotonin, acetylcholine, GABA,
epinephrine-norepinephrine, histamine.
 The Nervous System in 2 parts
1. The Central Nervous System CNS
– Brain
– Spinal Cord ((thoracic, cervical, lumbar, sacral, coccygeal
regions)

2. The Peripheral Nervous System PNS

– The Somatic Nervous System (connects distal parts of
the body to the spinal cord)
– The Autonomic Nervous System (regulates
autonomic body functions, eg, heart rate, breathing)
https://pin.it/6XfixoH
 CNS
• Brain and Spinal Cord
• Anatomically centrally located
• Also functionally central as the site of INFORMATION
INTEGRATION
• Where we make sense of all incoming information from both
the external and internal environment
• The CNS makes decisions and sends messages out to the
muscles, tissues, glands etc. in order to react to incoming
stimuli
 The Brain’s protective layers
• Cranium - the strong bony structure encasing the brain.

• Between the cranium and brain are 3 meningeal layers

– The softest layer that adheres to the brain, resembling tissue paper, is
the PIA Mater.
– The middle layer has small projections down to the Pia Mater and it
looks like a spider’s web, this is called the ARACHNOID Mater.
– CEREBROSPINAL FLUID flows through below the Arachnoid mater and
above the Pia Mater.
– The toughest layer, the DURA Mater sits above the Arachnoid Mater. It
is as thick as a paper bag.
– Inflammation or infection in any of these layers is called meningitis.
Brain divisions

• The CEREBRUM
• The CEREBELLUM
• The BRAIN STEM
 Cerebrum (PL.: cerebra)
• The topmost part of the human brain.
• Two-thirds of the brain’s mass
• Contains the cerebral cortex and subcortical structures.
• The most developed and evolved part of the human brain.
• White and gray matter –
Gray matter consists of the soma and dendrites of cortical neorons.
This is where neurons conduct most of their functions.
White matter consists of the axons coming out of those neurons. It
appears white because of the fatty layer of Myelin sheath covering
axons.
 The Cerebral Cortex
The folded brain tissue we see when the
cranium is removed. This is known as the
cerebral cortex.

• Sulci and gyri

 Little brain and the brain stem
• The cerebellum is known as the “little brain”
and it is involved in reflexive & autonomous
actions.
• The brain stem consists of the pons (taken
from the Latin word meaning bridge),
midbrain & medulla oblongata.
• These areas are the more primitive structures
of the brain.
 The 2 cerebral hemispheres
• Broadly the brain is divided along the longitudinal fissure
into the left and right hemispheres.
• The hemispheres on each side control the opposite side of
the body (information from the senses is passed contra-
laterally to the opposite hemisphere).
• They largely mirror each other other than for certain
language centres of the brain.
• Broca’s and Wernicke’s areas are located according to an
individual’s dominant side determined by their
handedness.
• The hemispheres are connected by a thick band of neural
fibres called the corpus callosum. In severe epilepsy, some
doctors opt to create lesions in the corpus callosum.
The 4 lobes of the cerebral cortex
• Frontal lobe

• Parietal lobe

• Temporal lobe

• Occipital lobe
 Phineas Gage: Frontal Lobe damage
• https://www.verywellmind.com/phineas-gage-2795244
• The story of Phineas Gage (1823-1860) is one of the first scientifically
documented and published case studies (Dr John M. Harlow, 1948) linking
a capacity of higher thinking, such as problem solving, and personality
characteristics, such as emotional control, and the prefrontal cortex, the
foremost part of the frontal lobe.
• Initial studies of brain neurobiology were all w patients who had incurred
damages to different areas of the brain and linking those areas with the
loss of certain abilities that characterised these patients prior to the
accident.
• Later in the last century lab based animal studies (mostly w rats and
monkeys) involved creating lesions in the brain and watching for changes
in the animal’s behaviour. At the turn of the 20th century and currently
brain imaging techniques (fMRI, CT scans, EEG etc) are also used to
discover the functions and connections between brain areas.
 The temporal lobe
• The lateral sulcus (groove or canyon) separates the
temporal from the frontal n parietal lobes. Viewed laterally
(from the side) the temporal lobe is right behind the ear.
• We have two temporal lobes, 1 in each hemisphere. The
right temporal lobe processes all sound information coming
in via the left ear.
• When sound waves enter the ear, they travel down the ear
canal and reach a snail like structure inside the ear called
the cochlea.
• The cochlea converts the sound vibrations (physical energy)
into electrical impulses through a process called
transduction.
Main function of the temporal lobe
• Hearing
– Taking in and interpreting raw data coming in as electrical impulses.
– Electrical impulses from sound waves are taken by the auditory nerve via the brain stem and the
hypothalamus to the temporal lobe on the counter-lateral side of the cerebral cortex.
– Eventually this will reach the AUDITORY CORTEX (the upper part of the lobe). The auditory cortex
recognises PITCH, FREQUENCY and sound localisation.
– In order to understand what is being said, the information is sent to the Wernicke’s Area (named
after the neurologist Carl Wernicke) located behind the auditory cortex. Wernicke’s area’s main
function is to interpret what it is we are hearing.
– The visual cortex in the occipital lobe also looks at the facial expression that accompanies the sound
impulses. This will communicate with the auditory cortex to add to our comprehension. (Example of
someone saying OK, we not only have to recognise the sound but also interpret its meaning by the
pitch, facial expression etc.)
– Wernicke’s area then communicates with Broca’s area (named after a physician called Paul Broca)
located in the frontal lobe that controls the muscles of the mouth and allows us to speak.
– Damages to the Wernicke’s and Broca’s areas lead to Wernicke’s aphasia and Broca’s aphasia where
our speech and comprehension are affected.
 Functions: temporal lobe
• Memory and emotion

• Object identification
 Language centres of the brain
• Broca’s and Wernicke’s areas together are known as the language
centres of the brain.
• Their location is determined by the dominant hemisphere of the
brain. The dominant side can be identified by ‘handedness’.
• Most people are right-handed, indicating their left hemisphere is
the dominant side of their brain. In their case Wernicke’s and
Broca’s areas are located in the left temporal and frontal lobes.
• Other brain structures are present in both sides of the brain but
structures associated w language comprehension and production
are located unilaterally on the dominant side of the brain.
• Left-handedness is culturally discouraged in our country and even if
a child is allowed to use their left hands to write with, they are
almost always made to use their right hands to eat with. There is a
greater likelihood that left-handed people will be ambidextrous.
 The Limbic System
• Seat of our emotions. Often referred to as the
“emotional nervous system”.
• Also supports behaviour, motivation, long-term memory
and olfaction (the sense of smell).
• The limbic system is a set of structures located below the
cerebrum, includes part of the cerebrum’s subcortical
layers, the midbrain and diencephalon.
• The brain stem relays all incoming sensory information to
the limbic system where its various parts communicate
with each other, passing information among themselves
and then, depending on their stored memories, they
decide which parts of the brain or glands need to be
activated for an appropriate response.
 Parts of the Limbic System
5 important areas in the limbic system that play a role
in cognitive functioning:
– Thalamus – Works like a filter and relay station where all incoming
information coming from the are 1st sorted and sent to the relevant
centres for processing.
– Hypothalamus –
– Hippocampus – Helps to form memories by first storing
information.
– Amygdala – Fear, anxiety and feelings of threat. Also joy and
reward.
– The Pituitary Gland – The master gland that sends messages
to all other glands telling them to secrete relevant hormones.
 CNS: The Spinal Cord
31 pairs of nerves that enter & exit through
regions of the spinal column
• Cervical
• Thoracic
• Lumbar
• Sacral
• Coccygeal