how does the nervous system enable psychological reasoning?

what does the central nervous system include?

• brain & spinal cord

function of CNS

regulates, coordinates & controls major functions of the body

function of the brain

• regulates and guides other parts of the nervous system

  → body functions (ie. breathing)

  → receiving & processing info from the body & coordinating responses

  → higher order thinking

  → emotions, personalities

spinal cord

• cable-like common nerve fibres encased by bones called vertebrae

function of the spinal cord

• sends sensory/afferent information towards the brain (ie. sensations such as touch from the skin of the hand)

• sends motor/efferent information away from the brain (ie. instructions on how to move the hand)

• spinal reflex

SAME

sensory afferent (towards) , motor efferent (away)

function of the PNS

links CNS to other parts of the body

somatic NS

division of the PNS

• carries sensory information to the CNS

  → sensory receptors & neurons in the somatic NS gather info from 5 senses

• carries motor information from the CNS to skeletal muscles to initiate voluntary movement (ie. running)

autonomic NS

division of the PNS

• transmit information between CNS and organs&glands to ensure regulation without conscious awareness

sympathetic NS

division of the autonomic NS

• prepares body for action

• activates the fight-flight responses

• activates adrenaline, activating muscles & organs

increases heart rate, inhibit digestion, dilates pupil

parasympathetic NS

division of the autonomic NS

• maintains body in a state of homeostasis

• returns body to calm after action

• counter balances sympathetic NS

decreases heart rate, contracts pupuls

homeostasis

• body’s state of calm

neurons

cells within the nervous system that transmit messages to and from the brain, with various functions

sensory neurons

• transmit sensory information from the body to the brain

• via afferent pathways

• PNS

motor neurons

• transmit motor information from the brain to the body

• via efferent pathways

• PNS

process of neuron communication

1. sensory stimuli is detected by sensory receptors at a receptor site (ie. skin)

   → sensory information passed along afferent tracts by sensory neurons

2. interneurons in the brain processes and initiates motor movement, relays to motor neurons

   → motor information passed along efferent tracts by motor neurons

3. motor information is passed to muscles (ie. stomach)

unconscious responses

• responses that occur without awareness (ie. breathing)

the spinal reflex

• automatic unconscious response initiated by neurons in the spinal cord, independent of the brain

• adaptive response

why does the spinal reflex occur?

• allows for faster reaction time

when does the spinal reflex occur?

• when pain response

process of the spinal reflex

1. sensory stimuli (ie. stepping on a bee) is detected by sensory receptors

   → sensory information passed along afferent tracts by sensory neurons

2. interneuron in the spinal cord intercepts and recognises a pain message, initiating motor movement that is relayed to motor neurons

   → motor information is passed along efferent tracts by motor neurons whilst sensory information continue travelling on afferent tracts to the brain

3. motor information is passed to muscles to perform a response (ie. move away)

4. interneurons in the brain process the sensory information and feel pain

dendrites

• receives incoming neural messages

soma

• body of the neuron

• contains the nucleus with the genetic material for the neuron

axon

• pathway which the neural messages travel

myelin

• fatty tissue that encases the axon to aid in speed of transmission

axon terminals

• exit pathways for neural messages to make their way to the next neuron

terminal buttons/synaptic knobs

• releases neurotransmitters to a receiving neuron for communication purposes

process of neurotransmission

1. information is received at the receptor of dendrites

   → originally neurons are in resting potential

2. information comes in and activates the action potential

3. vesicles containing neurotransmitters are stimulated and move to the end of the terminal button

4. vesicles release neurotransmitters across the synapse

5. neurotransmitter is picked up by the receptor in the dendrite of the next neuron

vesicles

• contains neurotransmitters/neuromodulators

neurotransmission

• communication within a neuron uses electrical energy

  → once started, will keep going

• communication between neurons uses chemical energy

  → information can either continue to next neuron or stop

reuptake

• reabsorption of a neurotransmitter

when does reuptake occur?

• when neurotransmitters are released but not received by next neuron

  → terminal button can reabsorb neurotransmitter through reuptake and store it until used again

neurotransmitters

alters the chemical activity of other neurons

• chemical substance released by the terminal button of a pre-synaptic neuron to send signals to a post-synaptic neuron, necessary for neural communication

• released into the synapse

• speed of action - moderately fast

role of neurotransmitters

• transmit chemical signals to adjacent neurons

• some neurotransmitters can excite a response

• some neurotransmitters can inhibit a response

• each neurotransmitter binds with it’s specific type receptor to trigger a specific response

excitatory neurotransmitters

• increase likelihood that the neuron will fire an action potential (ie. glutamate)

inhibitory neurotransmitter

• decrease the likelihood that the neuron will fire an action (ie. GABA)

glutamate - memory

• excitatory neurotransmitter involved in memory and learning

• sends signals to other cells to create large brain networks

• helps with formation and retrieval of memory and enables learning

GABA - calming

• inhibitatory neurotransmitter associated with calming feelings of anxiety, stress or fear

• blocks and inhibits brain signal

neuromodulators

• chemical released by neurons to alter effectiveness of neural transmission

• creates longer, sustained signals which leads to lasting changes in cellular activity

• effective on a group of neurons

• released same as neurotransmitters

• speed of action - moderately slow and last for longer periods

role of neuromodulators

• alter the neural transmission of neurons by controlling the synthesis and release of neurotransmitters

• work together with neurotransmitters to enhance the inhibitory and excitatory effects, and create more widespread impacts

dopamine - pleasure

• a neuromodulator & neurotransmitter (excitatory in the reward pathway (seek activities that bring pleasure) and inhibitory in the brain (reduction in impulse/motor control & rational thinking))

• involved in drive, motivation and smooth motor movement

• associated with addictive behaviours

• reinforces neural activity in the brain

serotonin - mood

• a neuromodulator & neurotransmitter (inhibitory) that is involved in mood stabilisation

• important role in wellbeing & hapiness, digestion & metabolism, stress & sleep

• low levels of serotonin is linked to mental health problems (ie. depression)

neuroplasticity

• the ability of the brain to physically change in response to experience

developmental plasticity

• occurs naturally across lifespan

  → certain critical periods that enable greater developmental plasticity

adaptive plasticity

• occurs as a result of brain damage or trauma

• utilising critical periods for developmental plasticity helps enable greater adaptive plasticity

synaptic plasticity

• ability of synaptic connections to change overtime in response to activity or experience

• process of neuroplasticity at a single cell level

long-term potentiation

• long-lasting and experience-dependent strengthening of synaptic connections that are regularly activated

• increase in synaptic strength through high frequency stimulation of the neural pathway (things we do a lot means synapse needs to become stronger)

• “neurons that fire together wire together”

what occurs as a result of long-term potentiation in the neural connection?

• more terminal buttons, hence, also more neurotransmitters to send information more frequently

• more dendrites receving information

long-term depression

• long-lasting and experience-dependent weakening of synaptic connections between neurons that are not regularly activated

• reduction of the efficiency of synaptic connections

what occurs as a result of long-term depression in the neural connection?

• reduction in terminal buttons and dendrites as connection is not activated regularly, and resources will go towards those activated often

sprouting (LTP)

• ability of dendrites or axons to grow fibre at the synapse

• creation of new connections between neurons

rerouting (LTP)

• formation of new connections between neurons to establish alternative pathways around damaged neurons

pruning (LTD)

• elimination of synaptic connections that are not adequately activated

reward pathway

• group of structure of the brain that ar activated by rewarding a stimuli

role of dopamine in hunger

1. dopamine levels decreases below baseline in the reward pathway of the brain

2. sensation of hunger

3. increase in food seeking behaviour

4. dopamine levels in the reward pathway of the brain increase above baseline when we eat

5. pleasure is experienced

role of dopamine in addictive behaviours

1. dopamine released in reward pathway, producing pleasure

2. overtime baseline increases (more dopamine is needed to get ‘dopamine hit’) & dopamine levels drop below baseline

3. increasing urge to carry out activity to seek feelings of pleasure

4. more unhealthy addictive behaviours

(cycle)

serotonin pathway

• serotonin’s neuromodulatory system, originates in the brain stem and extends to almost all areas of the cerebrum

how is serotonin linked to aggressiveness

1. low serotonin levels weaken communication between amygdala (regulates emotions) and frontal region of cerebral cortex (making decisions)

2. makes it difficult for cerebral cortex to regulate emotional responses to anger

3. increases aggressiveness/impulsivity

changes to the physical structure of a neuron during sprouting

• growth of dendritic spines on the post-synaptic neuron → dendrites look bushier

• growth of filigree apendages on the axon terminals on the pre-synaptic neuron

• formation of additional synapses where dendritic spines and filigree appendages meet (synaptogenesis)

dendritic spines

• dendrite fibre that grows by sprouting on the post-synaptic neuron

filigree appendages

• fibre that grows by sprouting from axon terminals of pre-synaptic neuron

synaptogenesis

• formation of new synapses that result from sprouting

nervous system

• network of cells that act as a communication system between the body’s cells & organs

purpose of the nervous system

• receive, process & coordinate response

enteric NS

• digestion

• connection to CNS & communicate about digestion

• regulates gastric acid

• regulates the release of gut hormones

• regulates changes in local blood flow

• neurons detect sensory information from cell walls in the gut → convert to action potential → transmit signals to vagus nerve

why is the spinal reflex considered adaptive?

• saves time in situations that may be very harmful (ie. burn)

stressor

any event that causes stress or is perceived as a threat and a challenge to our ability to cope (ie. traffic, losing homes)

stress

state of emotional, mental & physiological tension, resulting from a stressor

• stress is a psychobiological process (ie. bio-increased heart rate, FFF response, psych-feelings of fear)

acute stress

stress that usually occurs because of a sudden threat and only lasts a short time (ie. assault)

• releases adrenaline

• quick recovery & return to homeostasis

• often more intense but can be beneficial to help overcome challenges

chronic stress

stress that lasts for a long time

• suppress immune system, affects our digestive and reproductive system, increase risk of health problems due cortisol

• less intense but more detrimental to our health

• releases cortisol

fight flight freeze response

automatic biological response to acute stress

• acute stress as it is short term and intense

• adaptive as it prepares the body to respond to threat and increases chances of survival

fight

dealing with stressor directly

• involve aggressive responses

• sympathetic NS

ie. fighting a bear

flight

evading/escaping stressor

• sympathetic NS

ie. running away from the bear

freeze

immobilising the body to avoid detection & conserving energy to fight or flight when there is a chance

• used when stressor is too much to deal with

• parasympathetic NS

ie. staying quiet to avoid the bear from noticing

cortisol

hormone produced by the adrenal glands that regulate many bodily processes (ie. metabolism) and is released in response to prolonged stress by the adrenal cortex

• released directly into bloodstream & transported throughout the body

role of cortisol

allows body to stay alert for prolonged periods of time

positive impacts of cortisol

• boosting energy levels and increase glucose levels

• heighten alertness

• increase body’s ability to repair tissue

• diverting energy from non essential bodily functions

impacts of high levels of cortisol

• suppresses immune system

• risk of cancer & psychiatric conditions

gut-brain axis

connection between the CNS & enteric NS, enables bidirectional communication between the brain & gastrointestinal tract via the vagus nerve & gut microbiota

vagus nerve

nerve that connects the brain to gut via nerve fibres (enables the bi-directional communication)

• originates in the brain stem & extends to the colon

• controls mood, immune response, heart rate

ie. gut dysbiosis → brain

digestion (stimulating stomach acids) → gut

gut microbiota

individual microorganism found in the gut

• more than 1000 microbe species found in the gut

• digest components of our food to provide their own nutrition & provides us with energy & nutrients

• production of some neurotransmitters, affecting the neural activity & cognitive function of the brain

• certain microbiota in the gut involved in regulating production, storage & release of neurotransmitters (ie. bacterium Bacteroides produce GABA)

• enables fast signals to be transmitted to the brain via the vagus nerve

frontal lobe

thinking, memory, behaviour and movement

SSRIs (selective serotonin receptor inhibitors)

antidepressants

• block/prevent serotonin from being reabsorbed into pre-synaptic neuron, increasing/stabilising mood

impact of chronic stress on gut microbiota

chronic stress → increased cortisol → gut dysbiosis (linked to anxiety & depression)

gut microbiome

collection of all microorganisms that exist within our gut

gut microbiota effects on the brain

• neurotransmitter levels (ie. serotonin)

• affects amygdala

• assists with neural processes

• gut dysbiosis can cause inflammation → impair brain function

• gut dysbiosis can cause overstimulation of HPA axis due to sensitive stress responses → excessive cortisol release → supress immune system

brain effects on gut microbiota

• psychological processes can effect the gut (ie. bloating)

• release of serotonin, dopamine & stress hormones (ie. cortisol & adrenaline) can cause gut dysbiosis (less ‘good’ bacteria) which affects immunity

selye’s general adaptation syndrome (GAS) ( biological) model of stress

biological model of stress that proposes we have a non-specific (same no matter the stressor exposed) biological response to stress that occurs in 3 stages that is identical for all

stage 1: alarm reaction

becoming aware of stressor, two phases, shock & counter-shock

• short lasting, few seconds

shock

• acute stress response

• body’s ability to to deal with stressor falls below normal

• decrease in body temp, blood sugar levels

• parasympathetic NS activated

countershock

• compensate for acute stress in the shock phase

• body’s ability to deal with stressor rises above normal

• release of adrenaline & cortisol

• activation of fight, flight, freeze response

• increased heart rate, temp & muscle tension

• sympathetic NS activated

stage 2: resistance

when stressor persists over a long time, body’s resources are maximised to cope & adapt over time (ie. increased glucose levels → extra energy to deal with stressor)

• body actively dealing with stressor

• ability to deal with stressor continues to rise above normal

• cortisol levels at highest → beginning the weakining of immune system (ie. colds)

stage 3: exhaustion

continued depletion of energy & resources

• body runs out of resources due to prolonged time dealing with stressor

• body becomes weak, susceptible to psychological illnesses/health conditions due to previous high levels of cortisol

• gut dysbiosis

• (ie. cannot function on a day-to-day basis)

SCARE

S hock

C outershock

A larm reaction

R esistance

E xhuastion

strength of the GAS model

• suggests a predictable pattern of responses that can easily be testified

• identifies various biological processes

• research and evidence conducted to support findings

• shows both acute & chronic stress

limitations of the GAS model

• rats as test subjects

• does not acknowledge psychological process, stress is subjective

• not gender representative

• does not account for individual differences

transactional model of stress

stress is only elicited if an event is perceived to exceed our ability to cope & based on our appraisal of the situation

• varied responses between individuals due to perception of stressor

appraisal

process of categorising an event on the basis of its perceived significance & how it may affect our wellbeing

irrelevant

situation or event that has no implications for an individual’s wellbeing