Psychology 1100- Chapter 3 (The Brain)

What is a neuron?

Nervous system cell that processes thoughts, feelings, and behaviours by communicating with other neurons.

How did scientists discover the structure of neurons?

Santiago Ramón y Cajal used the Golgi stain (potassium dichromate + silver nitrate) to visualize neurons

Neuron structure and function

Structure	Function
Soma (cell body)	Coordinates processing, protein synthesis, metabolism, energy production, keeps cell alive
Dendrites	Receive information from other neurons and relays to soma
Axon	Sends information to neurons, muscles, glands
Synapse	Junction between axon of none neuron and dendrites/soma of another
Myelin sheath	Fatty insulation around axon
Glial cells	Support nervous system cells
Nodes of Ranvier	"Recharge stations" that speed action potential transmission

What are the different types of neurons and their functions?

Sensory: carry external sensory info to CNS (light, sound, touch, taste, smell)

Motor: carry signals from spinal cord to muscles to produce movement

Interneurons: connect sensory, motor and other inter neurons (majority of neurons)

What are the specialized neurons?

Purkinje: interneuron; carries info from cerebellum to brain/ spinal cord (dense dendrite structure)

Pyramidal: cerebral cortex (triangles shape)

Bipolar: sensory neuron found in retinas; one axon and dendrite

How do neurons communicate?

Electrochemical signalling

Electrical signals conducted within neurons, from dendrites to cell body then down axon

Chemical signals transmitted between neurons across synapses

What are two driving forces for ion movement?

Electrical: opposite charges attract

Concentration: ions move from high to low

What is resting potential?

Difference in electrical charge between the inside and outside of neurons cell membrane (-70 mV)

Gated channels for Na and K ions are closed

What is action potential?

Electrical signal conducted along length of axon to synapse

Needs to reach certain threshold for neuron to fire (peaks at 40 mv)

Electric stimulation of neuron opens the Na channels, allowing Na to flow in and increase positive charge inside the axon relative to the outside

Action potential sequence

Stimulus reaches threshold

Na channels open, Na enters (+ cell charge)

Membrane depolarizers to 40 my

Na channels inactivate

K channels open, K exits (returning cell charge to -)

Membrane repolarizes

Sodium’s potassium pump restores ion balance

What happens when action potential reaches its maximum?

Na channels become inactive, K channels open and K ions rush out of the neuron, returning charge of cell from + to -

What are neurotransmitters?

Chemicals that transmit info across the synapse

Neurotransmitter	Main Functions
Dopamine	Movement, motivation, pleasure, learning, emotion
Glutamate	Major excitatory neurotransmitter, stimulates nerve cells to transmit messages
GABA	Major inhibitory neurotransmitter; fear regulation, sleep, reduces neuronal excitability
Norepinephrine	States of vigilance; Alertness, attention, arousal, ↑ heart rate, constricts blood vessels
Serotonin	Mood, sleep and wakefulness, digestion, aggression, sexual desire
Endorphins	Natural pain relief, mood enhancement (inhibits GABA-excess dopamine production)

What are the two categories that drugs fall into?

Agonists: increase neurotransmitter action

Antagonists: block neurotransmitter action

What is the nervous system and its two divisions?

Network of neurons transmitting electrochemical information

Central and peripheral nervous system

Central nervous system

Brain: supports perception, motor function, emotion, cognition

Spinal cord: branches down from brain

Spinal cord

Processes sensory information and motor commands, relays to body

Responsible for spinal reflexes (reflex arc)

Regions: cervical, thoracic, lumbar, sacral

Peripheral nervous system and its divisions

Connects CNS to body’s organs and muscles

Somatic NS: conveys info to skeletal muscles and CNS

Autonomic NS: carries involuntary and automatic commands that control blood vessels, oranges and glands

What are the parts of the autonomic nervous system?

Sympathetic: prepares body for action in threatening situations

Parasympathetic: helps body return to normal resting state

Hindbrain

Function: basic life functions and motor coordination

Structure	Function
Medulla	Breathing, heart rate, circulation
Reticular Formation	Sleep, wakefulness, arousal
Cerebellum	Fine motor control
Pons	Connects cerebellum and brain

Midbrain

Function: movement and orientation

Structure	Function
Tectum	Uses sensory information to orient body
Tegmentum	Movement and orientation

Forebrain

Functions: cognitions, emotion, sensation, movement

Cerebral cortex: outermost layer (left and right hemispheres)

Subcortical structures:

Structure	Function
Thalamus	Sensory relay station (except smell), filter/prioritizes info like computer server)
Hypothalamus	Homeostasis: hunger, thirst, temperature, sexual behaviour
Pituitary Gland	Produces hormones to control growth, metabolism, reproduction, stress response
Hippocampus	Formation of new memories and integrating them into larger network for storage
Amygdala	Emotional processing and emotional memories
Basal Ganglia	Movement control
Striatum	Posture and movement

Limbic system

Emotion, motivation, behaviour, memory

Includes hippocampus, amygdala, hypothalamus, thalamus

What is the amygdala high jack?

Fast emotional reaction before rational thinking intense; response to stress in which amygdala takes over

Activates fight or flight and can trigger fear, anxiety, panic, anger, sensitivity to startling

What is the endocrine system?

Network of glands that produce and secrete chemical messengers into the bloodstream

Hypothalamus sends signals to pituitary gland, which sends signals to other glands to control stress, digestive activities and reproductive processes

Cerebral cortex

Controls perception, emotion, movement and thought.

Wrinkled surface increases surface area

gyri = smooth parts

Sulci = crevasses

Left and right hemispheres

Contralateral control: right hemisphere perceives stimuli and controls movement on left side of body, and left hemisphere does same for the right.

Connected by commissures: bundle of axons, corpus callosum allows for communication across hemispheres

What are the different lobes?

Lobe	Function
Occipital	Vision
Parietal	Touch/sensory processing
Temporal	Hearing and language
Frontal	Movement, planning, memory, judgement, abstract thinking

Somatosensory cortex: skin areas in the contralateral surface of the body

What is brain plasticity?

Brains ability to reorganize itself by forming new neural connections

Examples:

Cortical remapping after injury: losing a finger and it being unresponsive by becoming responsive overtime due to stimulation from adjacent fingers

Phantom limb syndrome: following limb amputation, patients continue to feel sensations of where it was

Practice dependent expansion of cortical representation

What is heritability and what do its degrees represent?

Measure of variability of behavioural traits among individuals that can be attributed to genetic factors

Heritability of 0: genes do not contribute to individual differences

Heritability of 1: genders are only reason for individual differences

What is epigenetics and how can it influence gene expression?

Environment alters gene expression without changing DNA sequence

Influenced by high stress environments, generational trauma and early childhood experiences

Studying people with brain damage

Used to discover:

Frontal lobe emotional functions

Broca’s area (speech production)

Wernicke’s area (language comprehension)

Hemispheric specialization (split brain procedure)

Studying the brain electrical activity

Electroencephalograph (EEG) used to: record electrical activity in the brain to determine the amount of brain activity during different experiences and states of consciousness (sleep studies)

Structural brain imaging

Method	Purpose
CT	Shows brain densities, detects tumours and lesions
MRI	Detailed brain structure and volume; used to find damage
DTI (diffusion tensor imaging)	Maps white matter connections

Using brain imagery: functional brain imaging

Method	Purpose
PET (positron emission tomography)	Radiation detectors record radioactivity levels in brain regions
fMRI (functional magnetic resonance imaging)	Detects difference in oxygenated and deoxygenated hemoglobin to assess brain activity levels
Resting-State Connectivity	Measures temporal connection of spontaneous activity connections while at rest

What are the advances of using PET

Doesn’t require exposure to radioactive substance

localized changes in brain activity

more useful to analyze quickly occurring psychological processes

What can be used to mimic brain damage?

Trans cranial magnetic stimulation (TMS) methods: temporarily deactivate neurons in cerebral cortex, can be combined with fMRI and be used or manipulate state of brain and provide casual explanations