Intro To Biological Psych Notes

How are memories stored?

Repetition memory ‘Use it or lose it’

Action Potential = electric signal conducted along the axon synapse

Inside/outside neuron = different voltage electric gradient

Resting Potential

• Na⁺ and K⁺ AT out of axon by Na⁺/K⁺ pump

• AT of Na⁺ > K⁺ 3:2 pd across membrane

• Most Na⁺ gates shut / K⁺ gates open

• Axon membrane 100x more permeable to K⁺ which diffuse out

• Further pd

• Axon –ve due to K⁺ > Na⁺ -70mV

• Outside +ve due to Na⁺ > K⁺

Action Potential

= temporary wave of depolarisation Domino effect

• At RP inside = -70mV - some K⁺ channels are open, all Na⁺ ch close

• E of stimulus causes some K⁺ ch to close and Na⁺ ch to open

• Na⁺ diffuses into axon and starts an AP

• +ve feedback Na⁺ –membrane depolarises

• When action potential reaches +40mV - Na⁺ close, K⁺ opens

• +ve feedback K⁺– membrane repolarises - reverses electrical gradient

• Chemical pump reverses ion balance by moving Na+ out and K+ in to generate another AP

• AP only occur when a threshold is met: all or none principle

Critical properties of AP:

• All or none

• AP do not vary in strength

• Slow speed

• Takes time to recover max FR = 150Hz

What starts an AP?

• Sensory receptors

• Environmental change

• Chemical signalling from nearby neurons

How does an organism perceive stimuli?

1. Number impulses in a given time

2. Neurons with different thresholds which neurons and how frequent = interpret strength

Refractory Period return back to normal voltage – Na⁺ closed

• Ensures AP in only 1 direction

• Ensures AP are separated

• Limits number of AP

AP = needs oxygen and E from blood

AP measured as blood flow/oxyHb/gl levels

PET = uses radioactive markers o measure blood flow and glucose levels

fMRI = changes in O₂ and OxyHb levels

Spatial resolution = how closely recordings tell you how neurons are firing

Temporal resolution = how well you can determine when the activity happened

Hyper-polarisation

• Overshoot K⁺ moving out of axon

• Axon inside = -ve

• K⁺ close

• Refractory period

Saltatory conduction = conduction passes down myelinated axon and jumps from 1 Node of Ranvier to the next

Depolarise = excite -70mV +40mV

EPSP = excitatory increase chance AP – depolarise neuron

IPSP = inhibitory decrease chance AP – hyperpolarise neuron

IPSPs can spread and counteract EPSPs

Summation = SUM of many voltage changes exceeds threshold

Spatial Summation = many presynaptic neurons together releases enough NT to exceed threshold

Temporal Summation = single pre-synaptic neurons together release enough T to exceed threshold

Recording AP – v fine in membrane or coarse electrode in extracellular space

EEG = multi-electrode – record times from 1 part of brain to another

Extracellular Unit Recording = record electrical disturbance created each time an adjacent neuron fires

Intracellular Unit Recording = record membrane potential form 1 neuron as it fires

Recording EPSPs/IPSPs: large electrode inside and on surface of cortex and scalp

Measured EEG activity = combined IPSPs/EPSPs in 1000s cells

Brain stimulation

Can induce AP by creating voltage difference with electrodes

Intracellular AP

Extracellular EPSPs

Synaptic transmission

AP down axon

release of NT from vesicles

NT synapse binds with receptor sites AP

NT cleared out by:

• Reuptake

• Enzyme break down in synapse

• Binds to auto receptors

NT	Chemicals that transmit info synapse to next neuron Released when membrane depolairses due to AP Allows Ca2+ axon terminal
Glial cell	Physically support neurons supply nutrients and increase neural communication 85 billion
Cell body	Info-processing tasks Protein synthesis, E prod, metabolism
Synapse	Junction between axons 100-500 trillion
Interneurons	Connects sensory/motor neurons
Purkinje cells	Interneurons carrying info from cerebellum rest of brain/spinal cord
Pyramidal cells	Triangular cell bodies and single long dendrite among small ones
Bipolar cells	Sensory neurons in eye retina with single axon and a few dendrites
Terminal bouton	Bulbous – NT released

Vesicle fuse with axon terminal on cell membrane

Releases NT synaptic cleft

NT binds with receptors changes electrical permeability

Each NT has its own receptor

Ach	Regulates motor control attention, learning, memory, sleep
Dopamine	Mvt, motivation, arousal, pleasure
Glutamate	Learning and memory
GABA	Primary inhibitory NT
Noradrenaline	Mood and arousal
Serotonin	Hunger, sleep, arousal, aggression
Endorphins	Pain and emotion

Drug Action:

Agonists = increase NT action

Antagonists = decrease NT action

• Modify NT synthesis

• Facilitate NT release

• Mimic NT

• Block NT reuptake

• Block enzymes

• Mimic NT at auto receptor

Dopamine and movement

• Difficulty moving

• L-Dopa = dopamine

• Nigro-spatial dopamine pathway

NEURAL CODING

Neurons signal specific values of specific properties eg brightness, orientation, Gma

Muller’s Law of Specific Nerve Energies:

1 stimulus can affect all sensory organs all sensitive

BUT react differently

Eg 1 neuron perceives as light, sound, pain, smell etc

Labelled Lines Principle:

Activity in 1 neuron stands for 1 property

1 neuron signals 1 property = simple

eg cells only respond to stimuli in 1 part visual field/certain pitches

Encoding Intensity:

Rate of AP = 1 value

FR = stimulus intensity

Lord Adrian: stretch receptor frog

Rate coding = FR increases as stimulus intensity increases – nonlinear rel

FR shows how closely a stimulus property matches a value

FR limited by refractory period

Constraints on rate coding:

Refractory period = 2-5ms max FR=200 AP/second

Rate = Log(Intensity)

Intensity not directly prop to FR

Encoded logarithmically

greater range of intensities can be encoded

tells intensity of property of labelled line – higher FR = stronger

Population Coding:

= combing individual neuron activity weighted/vector mean

Use FR of multiple neurons to code value

Allows intermediate values to be coded

Rep of simple properties:

Strength of individual neuron rep how well the stimulus matches their individually preferred stimulus

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