PS1106 - Introduction to brain and behaviour

Biological psychology and its roots

• The study of the brain mechanisms that control and influence behaviour

• evolved from Philosophy, Physiology and Biology

• Modern psychology also includes social, developmental, cognitive, abnormal and individual differences

Dominant questions of ancient philosophers such as Buddha

• what and where is the mind?

• How does the mind interact with or influence the body?

• Can we reliably investigate the nature of the mind?

What organ was originally believed to be the “seat of the soul” and the location of memories

• The heart

• In ancient Egypt - however evidence of trepanning ( drilling holes in skulls) suggests an early recognition of the brains link to behaviour and health

Vital fluids (humours) believed to control body function and temperament

• blood - enthusiastic/social

• Yellow bile - independent/ ambitious

• Black bile - thoughtful/ introverted

• Phlegm - relaxed/quiet

Galen’s (129-200 AD) primary contributions to neuroscience

• identified fluid-filled spaces called ventricles in the brain

• Proposed that the cerebral cortex received sensations while the cerebellum controlled muscle movement

René Descartes’ (1596-1650) Hydraulic model

• proposed that nerves are hollow tubes that carry “animal spirits”

• Believed the pineal gland acted as a pump to inflate muscles with these spirits to produce movement

Concept of Dualism

• associated with Descartes

• The belief in the separation of the body and the mind

Phrenology

• developed by Franz Joseph Gall

• the theory that bumps on the skull reflected the brains surface and related to specific personality traits

• Scientifically Incorrect - however it introduced the important idea of localisation of function

Paul Broca and Karl Wernicke

• provided evidence for the localisation of specific functions by studying patients with brain lesions

• Broca identified a region for speech production while Wernicke identified an area for language deficits

Who proved that nerves use electrical mechanisms rather than hydraulics

• Luigi Galvani

• Demonstrated this by making a frogs leg muscle twitch using an electrical current

How did Flourens contribute to understanding brain areas

• Used animal studies to show that destroying specific brain areas affects specific functions

How did Gall contribute to understanding brain areas

• created phrenology - claimed bumps of the skull reflected personality traits

• Unscientific - introduced the concept of localisation of functui

What did Paul Broca discover about the left side of the brain

• identified a region for speech production after studying a patient with a brain liaison

What did Karl Wernicke discover about the left side of the brain

• described other language deficits linked to different left-brain area

What is a cyptoarchitechural map and who created it

• Korbinian Bridgman created a map that numbered cortical areas based on their cellular organisation

• Provided a physical link between brain structure an function

How did Luigi Galvani change or view of nerves

• used electricity to make a frog’s leg twitch, proving nerves use electrical mechanisms rather than hydraulics

• Noted nerve speed is slower than electricity in wires indicating a unique biological basis

What did stimulation studies prove about localisation

• Frisch and Hitzig used electricity on dogs to find motor/sensory cortices

• Robert Bartholow did the same with a human brain - this confirmed localisation of function without the need for phrenology bumps

What did Otto Loewi discover about the synapse

• using a frog heart experiment he proved that signal cross the junction between cells using chemicals called neurotransmitters

• By the 1950s it was established that most synaptic transmission is chemical

What are the benefits of MRI and PET scans in modern biology

• they allow researchers to visualise changes in activity in pectin brain regions during tasks

• These tools have confirmed and expanded findings from older studies on brain-damage patients

What are the basic cellular components a neuron shares with other cells

• neurons have a cell membrane, a nucleus containing DNA ad organelles for protein synthesis and energy production

Main specialised structural parts of a neuron

• dendrites - a dense tree of fine fibres specialised from receiving incoming signals

• Axon - an elongated projection specialised for rapid signal transmission over long distances

• Synapse - the junction or connection point between two neurons

Function of the Axon Hillock

• site where action potential is generated

Function of the myelination

• fatty sheath around the axon that helps with signal speed

What is the resting membrane potential of a neuron

• approximately - 70mV - means the inside of the cell is negatively charged to the outside due to an uneven distribution of ions

What main ions contribute to the membrane potential

• positively charged sodium (na+) and potassium (k+)

• Negatively charged chloride (cl-) and proteins (a)

Depolarisation

• the membrane potential becomes less negative (closer to 0m) often caused by an influx of sodium

Hyperpolarisation

• the membrane potential becomes more negative often caused by an influx of chloride

EPSP

• excitatory post-synaptic potential - caused by depolarisation (increased Na+ permeability) - it moves closer from firing

IPSP

• inhibitory post-synaptic potential

• Caused by hyper-polarisation - increased CL permeability - I moves the neurone further from firing

How does a neuron perform signal integration

• through summation

• Spatial summation - adding together polarising events occurring within a localised area of the membrane

• Temporal summation - adding together events that occur close together in time

Key rules of action potential

• it is an all-or-none phenomenon - it is always the same size it does not decay over distance

• It involves a rapid reversal of membrane polarity mediate by sodium and potassium

Does the speed of a signal conduction vary in different axons

• yes, different classes of axons have different conduction velocities for example a-alpha fibres are much faster than C fibres

Sequence of synaptic transmission

1. Action potential arrives at the terminal

2. Neurotransmitters are released from the vesicles into the synaptic cleft \

3. Neurotransmitters bind to receptors on the postsynaptic membrane

4. This causes a change in membrane potential (signal propagation)

5. Neurotransmitters are cleared via reuptake or metabolic breakdown

Major neurotransmitters and their primary actions

• Glutamate - primary excitatory amino acid

• GABA - primary inhibitory amino acid

• Dopamine, Serotonin, Noradrenaline, Acetylcholine - can be excitatory or inhibitory depending on the receptor subtype they bind to

Difference between a repertory agonist and antagonist

• agonist - binds to a receptor and evokes the same response as the native neurotransmitter

• Antagonist - binds to a receptor but evokes no reinsertion effectively blocking the neurotransmitter from binding

Drugs that affect neurotransmisson

• L-DOPA - enhances dopamine synthesis

• SSRIs - block serotonin reuptake

• Tetrodotoxin - prevents action potentials

Main types of movement the body performs

• locomotion - walking, running

• Posture - standing, balancing

• Sensory orientation - turning your head

• Species-specific patterns - grooming, gestures

• Acquired skills - driving, painting

• Simple reflexes - knee jerk

Primary motor cortex

• main brain area responsible for sending signals to your muscles

• The starting point for the pyramidal tract which is the highway of nerves leading to the spinal cord

Supplementary cortex

• helps with thinking about and starting a movement

Premotor cortex

• important for coordination - like staying steady while walking

Role of the cerebellum

• acts like a computer for “programs” that handle skilled movements

• If it is damaged movements become decomposed meaning they re jerky and no longer smooth or automatic

basal ganglia

• a group of structures in the brain that modulates or fine-tunes patterns of motor activity - it is heavily involved in the extrapyramidal system which runs parallel to the main motor highway

Apraxia

• the inability to carry out a movement when asked to do so even tho the person isn’t paralyzed and understands the command - it usually happens when the planning parts of the brain are disconnected from the doing parts

what causes parkinson’s disease

• caused by the loss of dopamine in the brain - this leads to symptoms like resting tremors, muscle stiffness and difficulty starting movements it is often treated with L-DOPA which helps the brain make more dopamine

Huntington’s Disease

• a genetic disease caused by a single dominant gene - causes the brain to lose it’s ability to stop movements leading to uncontrollable muscle jerks all over the body - there is currently no effective treatment to stop it

what causes Paralysis

• happens when motor neurons or the primary motor cortex are damaged by things like viruses, injury ot toxins

• damage to one side of the motor cortex usually paralyzes the opposite side of the body