The brain and behaviour

human nervous system

Complex combinations of neurons

• enables the brain to obtain information about what is going on inside and outside the body and to respond appropriately.

• Can be organised into different branches or divisions on the basis of the main functions carried out by each branch.

•Central NS includes

the brain and the spinal cord

•Peripheral NS includes

everything outside of the CNS

The CNS:

The brain and the spinal cord

Spinal cord runs from the base of the brain to the lower middle sections of the spine

• Enables the brain to communicate with the rest of the body by conveying messages from the brain to the PNS

Spinal cord is segmented

Upper - brain and upper parts of the body

• Lower section - lower parts of body such as legs, toes and feet

The Peripheral Nervous System

• Has 2 functions

• Sends information to the brain and spinal cord (CNS) – like temperature, pain, or how your body feels inside and out.

• Carries instructions from the brain and spinal cord to the body – telling your muscles to move or your organs to work.

The Peripheral Nervous System
Divided into

Somatic and Autonomic nervous systems

The Somatic Nervous System

Responsible for voluntary movement of skeletal muscles

Also responsible for carrying Sensory information to the brain (CNS)

Remember SAME

• sensory neurons are afferent and transmit information to the brain

• motor neurons are efferent and transmit information from the brain

Autonomic branch

Connects the CNS to the internal organs and glands. It is automatic/ self regulating.

Autonomic branch
Controls the function of internal organs through:

• Visceral Muscles

• In the skin

• Around blood vessels

• In the eyes

• In the stomach

• Of the heart

• Liver
• Glands

• Pancreas

• Sweat gland

The Autonomic Nervous System
Branches

Sympathetic branch
Parasympathetic nervous system

Sympathetic Nervous System

• Prepares the body for action by activating the fight-flight response.

• Increases physiological arousal & provides a sudden burst of energy.

When the sympathetic nervous system is activated,

a number of physiological changes take place including:

• pupils dilate

• heart rate increases

• breathing rate increases

• digestion is inhibited

• Salivation decreases

Parasympathetic Nervous System

Counterbalances the effects of the Sympathetic NS.

• Restores the body to a state of calm once the threat has passed.

• Keeps bodily systems functioning efficiently by maintaining homeostasis

(a steady internal body environment)

The Neuron
A neuron has many specialised parts:

Dendrites
Cell body (soma)
Axon
Myelin Sheath
Axon Terminal

Dendrites

receive information from other neurons.

The soma

is the largest part of the neuron and is the cell body.

The axon

is a nerve fibre that carries information (a neural impulse) away from the soma down the axon.

Myelin

insulates and protects the axon to enable fast and effective neural transmission.

The end of each axon has terminal buttons which release a chemical called

a neurotransmitter whenever electrical impulses are sent.

Between neurons is a

synapse (gap)

When the neural impulse reaches the end of each axon, the

terminal buttons releases chemicals called neurotransmitters into the synaptic gap.

Neurotransmitters pass across the

synapse and fit into receptor sites on the dendrites of the post synaptic neuron.

• When the electrical charge is great enough in the post-synaptic neuron

a neural impulse will travel down the axon of that neuron.

Types of Neurons in the Nervous System

Sensory Neurons
Interneurons
Motor Neurons

Sensory Neurons

Neurons that transmit information about the body’s sensations from the PNS to the CNS

Interneurons

Neurons that transfer impulses between sensory and motor neurons

Motor Neurons

Neurons that transmit information about voluntary movement from the CNS to the PNS

The brain

is the control centre for all behaviour

• Specific parts of the brain control specific behaviours

The cerebral cortex

is the upper most layer of the brain which is 2-4mm thick
It is involved with information processing and complex mental function

The brain is divided

into 2 hemispheres
each hemisphere contains four lobes

The Human Brain

• Made up of approximately 86 billion neurons

• 10,000 connections for each neuron

neural networks in the cerebral cortex enables

• Memory

• Attention

• Problem solving

• Movement

• Sensation

Left hemisphere controls movement and receives

sensation from/for the

right side of the body

Right hemisphere controls movement and receives

sensation from/for the

left side of the body

The three functional areas of the Cerebral Cortex

Sensory areas - Receives and processes sensory information i.e. smell, touch, etc.

Association areas - Integrate sensory information, motor and other information from other brain areas; enabling higher order mental processes such as language, thinking, problem solving, etc.

Motor areas - Processes and sends information about voluntary movement.

Motor movement - Basal ganglia

• Plays an important role in communicating motor messages to and from the cerebral cortex.

• It also works with the cerebellum to plan and manage smooth motor movement.

• Dysfunctions of the basal ganglia can cause movement problems linked to serious disorders such as cerebral palsy and Parkinson’s disease.

Cerebellum:

plays a vital role in coordinated movement, maintaining posture and balance

Contralateral:

left side of cortex controls movement/receives sensory information from right side of body and vice versa.

Top part of cortex controls/receives

sensory information from lower body parts and vice versa

language centres

In the left hemisphere for 95% of people

Broca’s area

LEFT frontal lobe ONLY*

• Production of clear and fluent speech

• Controls the muscles required for speech (next to Primary Motor Cortex)

Wernicke’s area

• LEFT temporal lobe ONLY*

• Involved in the interpretation of speech, referred to as the language comprehension center

• Vital for locating appropriate words from memory to express meaning

Aphasia

• Refers to a language impairment due to brain damage

• May include problems speaking, hearing language, and reading language

Broca’s Aphasia

• Trouble with speech production

• Sentences lack function words and grammatical endings (the, and, a, ing)

• Speech is meaningful but slow & deliberate

• Speech consists of very short and simple sentences, mainly verbs and nouns (non-fluent aphasia)
• Reading and writing not as affected (can be in some cases though)

• Victim aware and frustrated

Wernicke’s Aphasia

• Difficulty understanding spoken and/or written word

• Cannot produce meaningful sentences, can string words together but what they say is nonsensical (word salad).

• Difficulty finding the correct word to name an object or express an idea (temporal lobe being the memory).

• Blissfully unaware that what they say doesn’t make sense or that they have not understood what others are saying.

Hemispheric specialisation

• Refers to the idea that one hemisphere has specialised functions or exerts greater control over a particular function

• But they work together to coordinate almost all our behaviour

• Both hemispheres share much of their information by passing it back and forth (quickly) through the Corpus Callosum

Split Brain Surgery

• Involves severing the corpus callosum – which results in no impairment of brain functions

• Used to treat severe epilepsy

• Disables communication between the left and right hemispheres

Information from left visual field

is processed in the right hemisphere

Information from the right visual field is processed

in the left hemisphere

Information from the left visual field is received by the right

half of each retina and processed in the right hemisphere & vice versa.

Object in right visual field (processed in left hemisphere)

• Can name object

• Can pick correct object up with the right hand

• Conclusion – language

Object presented to left visual field (processed in right hemisphere)

• Cannot name object

• Can pick correct object up with the left hand

Broca’s Aphasia

Site of damage

Fluency of speech

Meaning of speech

Awareness

Left frontal lobe

Affected

Not affected
Aware – frustrated

Wernicke’s Aphasia

Site of damage

Fluency of speech

Meaning of speech

Awareness

Left temporal lobe

Not affected

Affected
Often not aware of their problem

Frontal lobe: areas of lobe

Primary motor cortex
Broca’s area

Association area of the frontal lobe

Executive functions such as thinking, feeling and behaving

Planning & problem solving

Personality

Regulation of emotions

Primary motor cortex

Voluntary movement of the skeletal muscles

Parts that we are able to move with great precision take up more

cortical space eg. Hands & fingers, lips

Parietal lobe

Primary Somatosensory Cortex

Association area of the parietal lobe

Spatial navigation

Spatial awareness

Primary Somatosensory Cortex

Receives information from sensory receptors (touch, pressure, temperature)

Amount of cortex devoted depends on sensitivity and amount of use of the body part

Occipital lobe

Primary visual cortex

Primary visual cortex

Receives and processes visual information from the eyes

Association area of the occipital lobe

Integrates information from other parts of the cerebral cortex to organise & interpret visual information in a meaningful way

Temporal lobe

Primary auditory cortex
Wernicke’s area

Primary auditory cortex

Receives sound information from the ears
Hearing

Association area of the temporal lobe

Object and facial recognition

Memory

Neural plasticity refers

to the ability of the cerebral cortex to change its structure and relocate function throughout the lifespan as a result of experience (learning).

There are two types of neural plasticity:

• Adaptive plasticity

• Developmental plasticity

There are three circumstances under

which plasticity can occur:

1. At the beginning of life when the brain organizes itself (developmental plasticity)

2. Throughout life, whenever something new is learned and memorised

3. In case of a brain injury to compensate for lost functions or maximize remaining function.

Neural plasticity: How does the cerebral cortex change?

There is a change in the internal structure of neurons (sensitivity of synaptic connections)

•The existing neural connections becomes stronger due to:

> Strengthening of synapse between two neurons

> Increase in the number of synapses between two neurons

•Creation of new connections with other nearby neurons

Adaptive plasticity

Can occur at any stage during the lifespan and refers to our ability to reorganise neural pathways in response to new experiences as well as enabling the brain to compensate for lost functionality due to brain damage.

Adaptive plasticity explains why:

A violinist has more significant cortical areas in their right motor cortex as their brain has been ‘adapted’ in response to the stimulation of developing their craft.

Adaptive plasticity occurs across the lifespan;

• The brain recovers faster in childhood than in adulthood or old age because children have more neurons.

• So, if a child has a brain injury, they are more likely to recover better and regain abilities than an adult.

• Sometimes, the brain can move functions from the damaged part to a healthy part, like the opposite side of the brain.

The focus of rehabilitation is always on repeated practice

to encourage rerouting and sprouting of neural connections.

The brain compensates for damage by

reorganizing and forming new connections with intact neurons.

Rerouting

is the process of forming new connections with active neurons around damaged areas.

Sprouting –

involves the growth of axons from undamaged neurons to reconnect neurons whose links were injured or severed.

Developmental plasticity

refers to changes in neural connections during development, which result from environmental interactions and learning experiences.

From the foetal stage of development through to adolescence

developmental plasticity will also occur.

Key stages of developmental plasticity

include:

1. Cell production

2. Cell migration

3. Cell elaboration

4. Synaptic pruning

5. Myelination

Cell production

cells divide and multiply to create the neurons required to receive, process and transmit information.

Cell migration

newly formed neurons determine what their function will be by traveling to their final location in the nervous system.

A young brain has greater plasticity because

it is packed with a greater number of neurons.

Cell elaboration

neurons connect with other neurons to form synapses so the transmission of information can take place.

Synaptic pruning

refers to a neurological process in which the overall number of synaptic connections is reduced to enable more efficient networks, resulting in more efficient brain functioning.

Happens in different times for different parts of the brain

We actually have significantly less synaptic connections in adulthood than when in early childhood –

the number of connections peaking at around three years of age

Myelination

starts during foetal development and continues through to adolescence. This is a process of insulating neurons to aid the transmission of neural impulses from one neuron to the next.

Intelligence is

not fixed

Your brain is physically growing and changing every time

you learn something.

This means that when people repeatedly practice an activity or access a memory,

their neural networks -- groups of neurons that fire together, creating electrochemical pathways -- shape themselves according to that activity or memory.

Acquired brain injury (ABI)

Brain damage that occurs as a result of injury or physical trauma to the brain and results in some form of dysfunction:

• Stroke

• Traumatic Brain Injury (TBI)

• Substance abuse

• Infection

• Degenerative neurological conditions

(Alzheimer’s disease, Parkinson’s disease, Multiple Sclerosis, etc.).

some facts about ABI

• Type or degree of dysfunction will be determined by the area affected and the severity of damage

• Occur most frequently in young men, < 25 years old

• Cognitive, physical, emotional, or social dysfunction

• Temporary or permanent, partial or total dysfunction

Frontal Lobe Damage

The Largest and most complex lobe
Cognitive Dysfunction:

• Planning

• Problem-solving

• Logical thinking

• Forming memories

• Accessing memories

Frontal Lobe Damaged
Emotional Control and Personality:

● Mood swings

● Apathy

● Impulsive

● Risky behaviour

Frontal Lobe Damaged

Control of Voluntary Movement:

• Plan and execute a voluntary movement

• Ranging from involuntary motor spasms to total paralysis of a body part

• Difficulty expressing emotion through facial expressions

• Broca’s aphasia

Temporal Lobe Damage

• Difficulties processing auditory information

• Wernicke’s aphasia

• Short-term or long-term memory loss

• Difficulty attending to what they see and hear

Parietal Lobe Damage

• Somatosensory cortex damage - loss of sensation

• Poor body awareness

• Poor spatial awareness

Parietal lobe damaged
Spatial neglect

Most often, arises from right parietal damage
Patient neglects the opposite side of space, usually the left side, as well as the opposite side of their own body
Often unaware that anything is wrong!