psych midterm 2

Neurobiology

Neurobiology of the mind is one of the fastest moving areas in psychology

Human nervous system can be divided into two

central nervous system, peripheral nervous system

Peripheral nervous system:

Includes both somatic and autonomic systems

Somatic nervous system:

Transmits signals to central nervous system from muscles, joints and skin via nerves. CNS sends signals through somatic nervous system to muscles, joints and skin to initiate, modulate or inhibit movement.

Autonomous Nervous System

Regulates internal environment of the body. Stimulates glands (i.e sweat glands), and organs (i.e heart, liver, lunges, pupils …). Nerves of ANS project signals from these targets to CNS

Is divided into sympathetic and parasympathetic systems. They are opposing systems in terms of outcome

Sympathetic signalling:

prepares body for action. Chronic stress leads to increased activity of this system

Dilates pupils, relaxes bronchi, accelerates and strengthens heartbeat, inhibits activity in intestines, contracts vessels

Parasympathetic signalling:

returns body to resting state

Contracts pupils, constricts bronchi, slows heartbeat, stimulates activity in intestines, dilates vessels

endocrine system

A commutation network that influences thought, behaviour and actions. It works together with the nervous system(preparing body to deal with perceived threats). Communicates through hormones.

Signals slower than nervous system. Uses hormones to influence breaking and body. These hormones are released into the bloodstream and can have wide-spread effects on the body and brain

Is primarily controlled by the hypothalamus via signals to the pituitary gland,, located at the base of the hypothalamus

Hypothalamus

Secretes hormones corticotropin-releasing hormone (CRH) that promotes pituitary gland to release adrenocorticotropic hormone (ACHT) which increases cortisol production of the adrenal gland

Cortisol, on the other hand, inhibits production of the CRH and ACHT ina negative feedback loop.

Central nervous system

Santiago Ramon y Cajal (1852- 1934)
- Neuroanatomist who won Nobel prize in 1906, for establishing the neuron or nerve cell as the basic unit of the nervous structure

Consists of the spinal cord and brain

Building blocks of central nervous system are neurons and glial cells

spinal cord

Nerve cable that emerges from the base of the brain and extends down about two thirds of the length of the vertebral column

glial cells

Essential part of the nervous system allowing neurons to function. There are microglia and these are macroglia.

Microglia

protect CNS neurons. They are smaller than the other glial cells and are mobile within the brain. They can metabolize dead tissue and are involved in keeping the CNS healthy

macroglia types

Astrocytes:
Link neurons to blood vessels, forming part of the blood-brain barrier. They engulf synapses (where neurons connect), regulating neurotransmitter release during synaptic transmission

Oligodendrocytes :
Surround axons in the CNS, forming the myelin sheath that insulates axon, which allows the electrical signal that travels in the axon to travel faster.

Anatomy of neurons// neuron cycle

A signal is received at the dendritic spines at the post-synaptic terminals where the neuron synapses with the axon of another neuron.

This signal can produce an electric current that travels from the dendrite to the soma of the neuron

If the signal accumulating at the axon hillock in the soma is strong enough, the receiving neuron will “fire” i.e it will produce an electrical impulse at the axon hillock

This electrical impulse travels down the axon toward the terminal buttons 9the pre-synaptic terminals)

When the electrical impulse reaches the pre-synaptic terminal, it can produce a chemical signal: the release of neurotransmitters

When neurotransmitters reach the post-synaptic terminal of the receiving neuron and the cycle restarts.

The resting potential (part of the action potential)

Electrical potential refers to how much energy is stored up in a system

At rest, when a neuron is not active, the electrical charge inside and outside the neuron is different

This difference is called a potential. It is the potential electric charge that could be released

A neuron at rest has the resting potential of around -70millivolts (i.e there are more negatively charges inside the neuron than outside of it)

Change of the resting potential

If the electrical stimulation is strong enough, it exceeds the threshold of excitation and the axon of the stimulated neuron will fire an action potential

During the action potential, the neuron is briefly depolarizer so the membrane potential reaches about 40mV

Diffusion

Particles tend to move from a region of high concentration to a region of low concentration, eventually reaching equilibrium of equal dispersion

Diffusion results from Brownian movement which correlates with temperature

Diffusion is a force that pushes particles against their concentration gradient

Electrostatic pressure

Equally charged particles repel each other and differently charged particles attract each other. As applied to neurons: negatively charged molecules (anions such as Cl-) tend to move away from each other and so do cations (positively charged molecules like Na)

Anions and cations are moving towards each other

Resting potential: diffusion and electrostatic pressure

At rest, the concentration of negative ions inside the neuron is larger than outside, which has more positively charged particles than the inside. Unequal distribution of K+ and Na+ causes resting potential

In the extracellular space(outside the neuron) there’s a high concentration of Na and Cl particles in equal proportion and some K+ molecules.

In the intracellular space(inside neuron) there are many negatively charged large proteins 9organic anions), K+, and low amounts of Na+ and Cl-

As a consequence, during rest, the inside of the neuron has more negatively charged particles than the outside, which has more positively charged particles. This is why the resting potential of the neuron is negative

Dynamics of diffusion and electrostatic reassure to determine the resting potential

Cl- is in greatest concentration outside, diffusion forces it inside. However, because there are many negatively charged organic anions inside, electrostatic pressure pushes Cl- out

K+ is higher concentrated inside, diffusion pushes it outside. However the outside is positively charged therefore at the same time electrostatic pressure pushes K+ in

Na+ is in greater concentration outside, so diffusion forces it inside. At the same time, because it is positively charged and the inside has more negatively charged particles, electrostatic pressure pushes Na+ also inside. This is why there is the sodium potassium pump

Organic anions cannot leave the neuron

Sodium potassium pump

3 sodium ions bind to intracellular sites on the sodium potassium pump

Phosphate group s transferred to the pump via hydrolysis of atp

The pump undergoes a conformational change, translocating sodium across the membrane

Conformational change exposes two potassium binding sites on the extracellular surface of the pump

The phosphate group is released which causes the pump to return to its original conformation

This relocates the potassium across the membrane completing the ion exchange

Ion channels in the neuron membrane

There are proteins in the neuronal membrane that form little channels(pores) connecting the inside of the neurons with the outside. Some of these proteins allow certain types of ions to pass. These channels are called ion channels. There are for example sodium channels and potassium channels

Some ion channels open only under certain conditions, for example when the potential across the neuron membrane has a certain value. These channels are called voltage-dependent ion channels

voltage dependent channels

Sodium channels are voltage dependent channels: they open and Na+ rushes into neuron(driven by force of diffusion and electrostatic pressure). This depolarizers the neuron membrane potential

ion flow during action potential

Sodium channels are voltage dependent channels: they open and Na+ rushes into neuron(driven by force of diffusion and electrostatic pressure). This depolarizers the neuron membrane potential

When depolarisation reaches a point close to 0mV, potassium channels open. K+ leaves neuron due to force of diffusion (less K+ outside), and driven by electrostatic pressure from inside due to increase in positive charge from Na+ influx

When depolarisation reaches about 40mV the sodium channels enter a refractory state and close: no more Na+ can enter the neuron

The forces of diffusion and electrostatic pressure continue to force K+ out of the neuron. This reduces the positive charge inside the neuron, repolarising it i.e driving down the membrane potential

When potential reaches resting potential, k+ channels close

There is a slight hyperpolarisation the end, neuron reaches -70mV. Sodium-potassium pumps restore resting potential

agonist modulate neurotransmission

agonist drugs can increase how much neurotransmitter is made, so there is more inside each vesicle
they can block the reuptake of neutransmitters
they can mimic a particular neurotransmitter, binding to that neurotransmitter's postsynaptic receptors and either activating them or increasing the neurotransmitter's effect

eg. banzodiazepines (anti-axiety), agonist for GABA-A receptor

antagonist modulate neurotransmission

antagonist drugs can decrease the release of neurotransmitters so there are fewer inside each vesicle

they can help destroy neurotransmitters in the synapse
they can mimic a particular neurotransmitter, binding to that neurotransmitter's postsynaptic receptors enough to block neurotransmitter binding

eg. ketamine(narcotic), antagonist for NMDA receptor

signal transmission summary of core events

When the action potential reaches the pre-synaptic terminal, it is converted from an electrical signal into
a chemical signal.
‣ First, the action potential causes Ca2+ entry into the presynaptic terminal. This promotes that vesicles
loaded with neurotransmitters (proteins) fuse with the presynaptic membrane.
‣ This causes neurotransmitters to be released into the synaptic cleft. There, they diffuse and eventually
bind to receptors (proteins), that swim in the membrane of the post-synaptic cell.
‣ There are several different types of receptors in the post-synaptic membrane of neurons in the CNS.
Each receptor can bind a particular neurotransmitter. For example, the AMPA and NMDA receptors are
glutamate receptors, binding the neurotransmitter glutamate.
‣ Binding the neurotransmitter can cause a specific action of the receptor. For example, some receptors
can form channels that allow electrically charged molecules (ions) to enter the post-synaptic terminal.
Now the chemical signal has been converted back into an electrical signal.
‣ This influx of electrically charged molecules can cause a depolarisation of the post-synaptic neuron,
which can then lead to the neuron firing an action potential. Some neurotransmitters can have the
opposite outcome, they are inhibitory, not excitatory.
‣ Some receptors do not lead to changes in charge when neurotransmitters bind to them, but they
influence biochemical processes in the neuron, which can change the structure or functioning of the
neuron.
‣ Released neurotransmitters are removed from the synapse by enzymatic degradation or reuptake into
the presynaptic terminal.
‣ Some psychopharmacological drugs influence these processes. SSRIs (selective serotonin reuptake
inhibitors) for example artificially increase the amount of the neurotransmitter serotonin in the synapse,
which is used as antidepressant treatment.

basic structure of neurons

soma- cell body
dendrite
axon hillock
axon
node of ranvier
myelin
axon terminal

inside synapse, vesicles with neurotransmitters, presnaptic terminal , neuro transmitter, postsnyaptic terminal

release and binding of neurotransmitters

Neurotransmitter binding, depending on the transmitter and the receptor can have a variety of outcomes.
‣ Some neurotransmitters can have an inhibitory
effect (e.g., GABA): they make it less likely that the post-synaptic neuron will fire. Some have an excitatory effect (e.g., glutamate): they make it more likely that the post-synaptic neuron will fire

control of neurotransmitter release

synapse consists of: presynaptic termina, synaptic cleft, post-synaptic terminal. it also includes glial cells (astrocytes) that enclose three parts:
1. autoreceptor
2.reuptake
3.enzymatic degradation

autoreceptor

sense the amount of released neurotransmitter to regulate exocytosis

reuptake

a reuptake mechanism recycles neurotransmitter from the synaptic cleft, moving it back into the presynaptic terminal. some antidepressants interfere with this process for the neurotransmitter serotonin (SSRIs)

enzymatic degradation

enzymes in the synaptic cleft actively degrade released neurotransmitters

hippocampus

a complex neural structure consisting of grey matter and located on the floor of each lateral ventricle.

center for episodic memories. No new memories of events may be formed if there is damage to the hippocampus

logically set up. Neurons are perfectly lined up in the same way and the information flow goes through a loop

anatomy of the human brain

**MEMO THE PARTS OF THE BRAIN

two hemispheres, cerenellum, fissure, gyri, sulci.

folded structure
fissure: (space between two hemispheres/ spaces within the nodes

size of the brain

reflects the size of the animal. receives input from all sides of the body so if u wanna represent the body u need a certain amount of neurons to do that. the bigger the animal the bigger the brain.

why is the brain folded

the brain is folded because it gets u more space. neurons are all at the outer layers so the more u fold it the higher the neuron count and sometimes this goes along with higher computational power

posterior view of the brain

frontal lobe
olfactory bulb (synapse point of cranial nerve 1)
optic chiasma
optic nerve (2)
optic tract
mammillary body
midbrain
pons
temporal lobe
medulla oblongata
cerebellum
spinal cord

corpus callosum

Corpus callosum consists of
millions of myelinated axons
that connect the two
hemispheres.
‣ Importance of this connection
apparent in split brain
patients

wide shape bc its axons.
having epilepsy a treatment would be to cut the corpus callosum which prevents one hemisphere from talking to the other. but it also prevents that if u have epilepsy from one brain area to travel to the entire brain so if u have seizures they're much more reduced in severity because they can no longer become global seizures.

contralateral organization

in the eye, the part of the retina that gets the right visual field gets projected to the right hemisphere

corpus callosum transmits information from one hemisphere to the other so that both hemispheres get the input of what is being seen although only one side gets the input

right hemisphere better with spatial relationships
left hemisphere better with language

because the hemispheres are somewhat specialized, in split brain patients two independent forms of knowledge exist

Left hemisphere critical for language: if split patient sees object with right eye, this is projected into the left hemisphere and therefore the object can be names

what patient sees with left eye(project into right hemisphere) cannot be named bc the right side does not have access to language system. however, patient can choose this item with the left hand (controlled by right side)

- show patient a a picture of a spoon and a fork. ask what they see they say fork. ask to pick up the object with the left hand, will pick up a spoon

lobes

frontal lobe
pariental lobe
temporal lobe
occipital lobe

frontal lobe functions

executive functions
deals with cognition and memory
ability to concentrate, judgement, consequence, analysis, problem solve, plan, personality(including emotional traits)
control eye movement
planning
can inhibit certain actions easier

parietal lobe function

integrating information from several senses
processes spatial orientation, some parts of speech, visual perception, and pain and touch sensations

visual processing pathway that gets split up and goes to occipital lobe- refered to as the what pathway and where pathway

occipital lobe function

visual processing center of the brain. contains most of what is referred to as the visual cortex is also the part of the brain where dreams originate. if this is lesioned u are blind even if ur eyes are perfectly functioning

vision isn't limited to here, on the temporal lobe (where objects are represented)

temporal lobe function

chief auditory receptive area and contains the hippocampus, which is the chief region where long-term memory is formed. also deals with high level visual processing (faces and scenes)

penfields mapping studies

cut open the brain, doesn't hurt, patient is conscious, have to go through the brain so before u cut stuff away you stimulate it with an electrode and see what happens

u find a path to the target that destroys as little essential functions as possible

wilder penfield did this kind of surgey and found out if u stimulate certain areas people respond with different experiences (i smell roses...). important bc linked brain activities to the state of experiences, so brain and mind have some sort of relationship because brain stimulation can lead to certain experiences

primary motor and sensory cortex

neurons devoted to the thumb compared to the rest of the hand is a larger area. human face has a lot of motor control in the mouth. u can see that the lips area of the face also has a high sensitivity

basically by analyzing how many neurons the cortex has u can see how sensitive/ how much motion an area on the body has bc more neurons devoted to that area to process it. u can see whats more important for humans

brain stem: basic survival functions

medulla oblongata - involuntary functions like sneezing, vomiting, respiration and other autonomic functions, breathing, some areas control of the heart, control of the sleep wake cycle

Brain stem is the superior end of spinal cord.
‣ Brain stem a main communication pathway between brain and body.
‣ Houses nerves that control basic functions, such as breathing, heart rate, swallowing, vomiting, urinating,
orgasm

Reticular formation: projects into cerebral cortex, affects general alertness. Involved in sleep regulation

cerebellum

Cerebellum (“little brain”) critical for proper motor function. For example, damage causes head tilt, balance problems.
‣ Cerebellum essential for motor learning and motor memory.
It operates independently.
‣ Cerebellum also involved in planning, event memory, language, emotions.

subcortial structures, thalamus

Thalamus is gateway to cortex. With the exception of odour information, it receives all other sensory modalities. Smell, the oldest and most fundamental sense, has a direct route to cortex.
‣ During sleep, thalamus partially shuts down incoming sensory stimulation.

hypothalamus

Hypothalamus (below thalamus). Indispensable for survival.
‣ Receives afferents from almost every body and brain region.
‣ Affects functions of many internal organs, regulates body temperature, blood
pressure, blood glucose levels.
‣ Involved in motivated behaviours, e.g, thirst, hunger, aggression, lust.

basal ganglia

Basal ganglia are critical for planning and producing movement.
‣ Afferents from entire cerebral cortex. Efferents to motor centres of brain stem.
‣ Damage can cause tremors and rigidity in Parkinsons’s disease, or loss of movement control in Huntington’s disease. (no inhibition for the muscles to stop moving in huntingtons disease, almost all muscle functions are affected even swallowing -kills people)
‣ Nucleus accumbens is part of basal ganglia, and is important for reward processing and motivating behaviour. This involves dopamine activity in the nucleus accumbens.

limbic system

Hippocampus essential for episodic and certain spatial memories.
‣ Hippocampus and amygdala densely connected. Amygdala processes emotions, such as fear.
‣ Amygdala modulates processes in the hippocampus (and other brain regions), might signal importance of events, thus increasing their likelihood of being retained.

interaction between amydala and hippocampus can make certain memories stronger and more important, amygdala sends a signal and allows that space to be better remembered bc something significant happened there.

Psychophysics

the science of defining quantitative
relationships between physical and psychological events.
Research aimed at relating physical stimuli to the contents of consciousness

absolute threshold

level of stimulus intensity required to create a conscious experience

just noticeable difference

smallest magnitude of stimulus required to detect discrete stimuli (advanced in weber's law)

signal detection theory

accounts for individual biases

sensation

the ability to detect a stimulus. features of the environment that are used to create understanding of the world

perception

the act of giving meaning to a detected stimulus
combining of sensations arriving from the sensory ssytem with prior knowledge

how do we assign meaning to incoming sensory information?

transduction

conversion of one energy to another. process where stimuli i.e light are converted to neural electrochemical energy

bottom-up processing

processing the elementary messages from the environment

top-down processing

applying memory, knowledge etc to understand and create a perception

extramission theory of vision

the proposal that visual perception is accomplished by rays of light emitted by the eyes, has been replaced by the intromission theory

plato - 4th century bc
first proposed extromission theory of vision; that the eye sends out vision beams which seize objects

galen, 2nd venture AD
further supported extromission theory, widely influence in European thinking for the next millennia

winer et al. 2002
found that 50% of American adults believe in extromission theory

intromission theory

has replaced extromission theory of vision. visual perception comes from some representation of the object entering the eyes

light

electromagnetic energy exists as both particles (photons) and waves

we only detect a small band ~400 - 700 nm

wavelength

perceived hue

frequency

cycle rate

amplitude

perceived intensity

things in the eye

cornea
iris/pupil
lens
retina
fovea

cornea

transparent tissue which allows light rays to enter the eye and focus on objects

iris/pupil

coloured part of the eye, consists of muscular diaphragm which regulated light entering the eye by expanding and contracting the pupil (center of the iris)

lens

crystalline lens inside the eye that enables the changing of focus (accomodation)

retina

contains photoreceptors (light-sensitive neurons)

neural signal pathway:
1. photoreceptors
2. bipolar cells
3. ganglion cells

fovea

small pit that cointains the highest concentration of colour sensitive light receptors- has the highest visual acuity in the retina

photoreceptors

transduce light into neural activity

two main parts: rods and cones

rods

Dim light (“night vision”)
• Sensitive to all wavelengths of light
• Black and white vision
• Low resolution (one bipolar cell: many rods)
• Around 100 million rods in each human eye

cones

Bright light (“day light vision”)
• Sensitive to blue/ red/ green wavelengths of light
• Colour vision
• High resolution (one bipolar cell: one cone)
• Around 5 million cones in each human eye

there are three types of cones

types of cones

s- cones
m-cones
L-cones

s-cones

short-wave length cones (blue)

m-cones

medium-wave length cones (yellow and greens)

L-cones

long--wave length cones (reds)

tetrachromats

humming birds also see uv

photoreceptors location in the retina

Rods are found in the periphery.
• Respond to amount of light
• Signal information about motion

Cones are found in the fovea (centre).
• Respond to quality of light.
• Signal information about detail.

blindspot

Where the optic nerve leaves the eye -> No photoreceptors in this area.
• Visual system usually fills in blindspot with information from surrounding area

bipolar cells

Intermediate cells that determine the information flow from photoreceptors to ganglion cells.

two types: diffuse bipolar cells and midget bipolar cells

diffuse bipolar cells

In the periphery.
• Respond to around 50 rods -> increase
sensitivity but reduced acuity (1 diffuse
bipolar: 50 rods
• Convergence of information: Many
rods:one diffuse bipolar cel

midget bipolar cells

Found in the fovea (centre).
• Receive input from a single cone and pass on info to a single ganglion (1 midget bipolar: 1 cone)

ganglion cells (retinal ganglia)

final layer of the retina

m-cell and p-cell

Retinal Ganglion Cell (RGC) axons form
the optic tract.

m-cell (large ganglion cell)

Mostly respond to rod cells via diffuse bipolar cells

P-cell (small ganglion cell)

Mostly respond to cone cells via midget bipolar cell

receptive field

the region on the retina in which visual stimuli influence neural firing rate

Receptive fields of individual retinal ganglion cells

ON-center, OFF-surround cell
A ganglion cell that increases firing in response to increase in light intensity in it’s receptive field center.
• When light hits the center - firing rate at maximum
• When light covers full receptive field - firing rate returns to baseline
• When light on surround -> baseline firing is repressed

off-center, on-surround cell retinal ganglia

A ganglion cell that increases firing in response to decrease in light intensity in it’s receptive field

function: Contrast in illumination help detect object edges, whether is it day time/ night time, whether indoors/ outdoors etc.
Also thought to be involved in colour processing

Opponent process theory (colour detection)

P-cells fire rapidly to one wavelength and
reduce to another- forms pairs of
colours.
• Red-Green (P-cell)
• Blue-Yellow (P-cell)
• Black-White (M-cell)
(e.g. the reduction of red firing = green)

Trichromatic theory

Colour vision occurs by comparing the activation of the three different cones.

the visual pathway

Information from the retina leaves the eye
via the optic nerve
• Information from the optic nerve travels to
the optic chasm (CROSS OVER).
• Lateral geniculate nucleus (LGN) of
thalamus.
• Visual Cortex/Striate Cortex/V1

processing after visual cortex

what stream
ventral stream - temporal lobe
object recognition

where stream
dorsal -> parietal lobe
location of objects in space

gestalt principles

Refers to theories of visual perception developed by
German psychologists in the 1920s
• Gestalt psychology describes how people tend to
organise visual elements into whole entities. Gestalt
psychologists believe we are born with specific
predisposed ways of organizing information so that
it has utility.
• Six Gestalt Principles