AOS1 U3

Human nervous system (CPR) receives and processes information to coordinate a response

Central nervous system processes and coordinates responses to sensory stimuli from the environment which consists of the brain and spinal cord

Brain receives and processes sensory stimuli from the body and coordinates responses

• voluntary movement

• conscious thought

Intricate network of cells that plays a vital role in processing information received through neural pathways from the body and in directing actions within the body

Spinal cord

• carries sensory info to the brain, from the body

• carries motor info to the body, from the brain

Spinal reflex is an unconscious response to stimuli initiated by the spinal cord without the input of the brain

process

1. sensory stimuli is detected by sensory receptors

2. sensory neurons carry info via afferent pathway to spinal cord

3. interneurons in spinal cord initiate an involuntary motor movement

4. which are relayed to motor neurons, carried via efferent pathways to muscles

5. muscles perform response w no input from brain

Interneuron can communicate between sensory and motor neurons, only found in the CNS and spinal cord

• is only found in the spinal cord and connects both sensory and motor neurons by relaying information between the 2.

Peripheral Nervous system

• transmits info to the CNS from the body’s muscles

• acts on information from the CNS

Somatic nervous system

• sensory info (afferent) from body to brain

• motor info (efferent) from brain to body

• voluntary movement

connects the CNS to the sensory organs and skeletal muscles

Autonomic nervous system

controls the body’s internal environment in a self-regulated manner

• relays messages between the CNS and visceral internal organs and glands

• visceral muscles include: heart, lungs, stomach, intestines, bladder

• glands include: tear & salivary glands

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the somatic controls movement of skeletal muscles whereas the autonomic controls visceral muscles which are usually involuntary

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Fight-or-flight-or-freeze response is an involuntary reaction resulting in a state of physiological readiness

• when the brain (hypothalamus) perceives a stressor, the sympathetic NS is activated where adrenaline is released via the adrenal glands

Reflexes - spinal reflex

Reflex is an unlearned and innate response to sensory stimuli

Reflex arc is a reflex controlled in the spinal cord

• monosynaptic - one synapse

• polysynaptic - multiple synapses

sensory (afferent) neurons: NS → CNS

relay neurons: CNS → CNS

motor (efferent) neuron: CNS→ effector cells, down the spinal cord

neural transmission

an electrical impulse that occurs through the communication between neurons when they are activated

neurotransmitters

chemicals released from the axon terminal of the pre-synaptic neuron into the synapse to carry the electrical signal across

• communication along the neurons is electrical

• communication between neurons is chemical

The action potential reaches the axon terminal of the pre-synaptic neuron.

Synaptic vesicles move to edge of neuron and the terminal button releases neurotransmitters.

The neurotransmitters then bind to receptor sites on the dendrites of the post-synaptic neuron.

The neurotransmitter either makes the post-synaptic neuron more/less likely to fire

When an action potential

reaches the axon terminal, tiny sacs (synaptic vesicles - store NT) move to the edge of the neuron and the terminal button releases neurotransmitters into the synaptic clef (gap between axon terminal of neuron and dendrite of next) then some bind to receptors on the next neuron’s dendrite, triggering it to fire.

• neurotransmitters are stored in the synaptic vesicles in the presynaptic neuron

• receptor site is on the post-synaptic neuron that binds neurotransmitters to transmit a neural signal

• DENDRITE → axon → synapse → neurotransmitter

Lock and key process

• Neurotransmitters act as the "key", each having a chemically distinct shape.

• Receptor sites on the postsynaptic neuron act as the "lock", with a specific shape that only a matching neurotransmitter can bind to.

• When the correct neurotransmitter binds, it triggers an excitatory or inhibitory response, influencing whether the postsynaptic neuron will fire an action potential.

Conscious response

• SNS responsible in which we are aware of our stimuli to choose a response

Unconscious response

• autonomic NS makes changes to our internal organs without awareness

Main excitatory neurotransmitter - GLUTAMATE

• increases likelihood of action potential being fired

• dominant in hippocampus (memory + learning) and cerebral cortex

• high - motor neuron diseases like Parkinson’s

• caffeine increases

• alcohol decreases

• decreased likelihood of action potential being fired

• counteracts glutamates effects by slowing neural transmission

• regulates anxiety with antidepressant (benzodiazepines) work by increasing effects of GABA to slow anxiety messages in the body

• low levels can increase anxiety

GLUTAMATE

• formation of learning + memory

• stimulates neural activity

• lack → LTP

• ongoing release → LTP

GABA

• low levels associated with anxiety and depression

why? due to increased arousal in brain regions and the sympathetic NS

DOPAMINE

• reward pathway

• thirst, hunger, addiction,

SEROTONIN

• mood

• impulsivity, low levels increases likelihood of agitation, aggressive behaviour etc

Synaptic plasticity

Specific changes that occur within the synapse, between neurons due to experience

Neural plasticity - ability of the brain to change, grow and reorganise

LTP

Relatively long lasting strengthening of synaptic connections, increasing the efficiency of neural transmission

• increased tendency to fire together after they have been electrically stimulated

• resulting from repeated activation of a neural pathway

• leads to increased neurotransmitter release and more receptors on the post-synaptic neuron.

LTD

Relatively long lasting weakening of synaptic connections, increasing the efficiency of neural transmission

• makes a post-synaptic neuron less receptive to information released by the pre-synaptic neuron

• resulting from repeated low levels of stimulation

• memory refinement for adaptive learning

SPROUTING

• new extensions on a neuron to allow new connections being made

• through the growth of nerve endings on axons OR dendrites

• growth of axon sprouts called filigree appendages on the axon terminal of the presynaptic neuron

• formation of additional synapses where these dendritic spines and filigree appendages meet, referred to as synaptogenesis.

REROUTING

Formation of alternate synaptic pathways through new synaptic connections between neurons

• neurons form new synaptic connections by bypassing damaged pathways

  • enhances adaptive learning by reinforcing efficient neural connections

  • helps brain to adjust

PRUNING

Refers to the removal of weak, ineffective or unused synapses

• increases the brain’s efficiency by refining neural circuits

Gut brain axis = the network of a bidirectional communication between the CNS and ENS (brain and gut), linking emotional and cognitive centres of the brain with peripheral intestinal functions.

Enteric nervous system (ENS) is a branch of the ANS, controlling the digestive system and connects through the CNS and SNS, functioning independently of the CNS.

• dedicated to the functioning of the gastrointestinal (digestive) tract

Functions

• communicates w the CNS

  • links emo + cog centres of brain with peripheral intestinal functions

• maintains chemistry of the gut (includes hormones, digestive acids and neurotransmitters)

what can impact the gut microbiota?

• chronic stress + increased levels of cortisol

• abnormal microbiota reduces resistance and increases susceptibility to stress related disorders - stomach ulcers from stress

what does it include?

• CNS

• Gut microbiota

• Vagus nerve

• Sympathetic NS

• Peripheral NS

• ENS

Vagus nerve

• nerve from brain stem to intestines

• connects the gut + brain

• gut → brain using NT like serotonin + glutamate + gut hormones

  • ALL play vital role in; sleep, hunger, pain, stress, mood

Gut microbiota / microbiome

• complex population of bacteria and other microogasisms which reside in the gastrointestinal tract

• relationship with health:

  • depression + anxiety

  • sleep

  • stress

Acute stress - limited effect on the microbiome

Chronic stress - well-established to increase the risk of illness and disease.

Stress is a state of physiological and psychological arousal produced by stressors that are perceived by the individual as exceeding their coping ability or resources

biological responses include increase heart rate, muscle tension

psychological responses include feeling, thoughts

Internal

psychological

• expectations

• feelings

• mindset

biological

• pain

• illness

• sleep deprivation

External

environmental

• loud noises

• extreme temperatures

Sociocultural

• daily hassles

• life events

• catastrophes

Acute stress tends to be more intense and short lived, occurring due to a sudden threat

• beneficial to help deal with challenges and build resilience

Chronic stress involves prolonged periods and constant feelings of stress and tends to be more detrimental to our health

• suppress immune system

• suppress digestive & reproductive systems

reasons?

• social isolation

• loneliness

• relationship problems

Cortisol is a hormone produced by the adrenal glands, regulating bodily processes such as metabolism

benefits

• increases glucose levels

• heightens alertness

• increases body’s ability to repair tissue

• diverts energy from non-essential bodily functions, such as digestion + growth

• anti-inflammatory agent

limitations

• prolonged release of cortisol in bloodstream can be detrimental

• suppresses the immune system, increase risk in illness + autoimmune diseases

• increase risk of psychiatric conditions such as anxiety & depression

Biological

fight-flight responses

freeze response

• sympathetic NS activation precedes the freeze state, but the energy conserving actions of the parasympathetic NS takes over

GAS model

SCARE

1. Alarm stage

   Shock

   • resistance is briefly lowered

     Counter-shock

• dealing with stressor

• sympathetic NS is activated

• adrenaline released

• cortisol takes over to help resist stressor

• resistance increases

• muscles tense, heart rate increase, pupils dilate

1. Resistance

   • sustained release of cortisol

     • at highest level, helping to repair any damage to body

   • physiological signs of wear and tear (flu symptoms, headaches)

   • body’s resources are maximised to cope and adapt and ability reduces

   • resistance levels is high, continues to rise above normal

2. Exhaustion

   • bodily resources are now depleted

   • excess of cortisol suppresses immune system, becoming more susceptible to conditions such as stomach ulcers, anxiety, depression

   • resistance is at its lowest

Stress involves a transaction between the individual and the external environment

Transactional model of stress and coping

suggests that stress is elicited only if an event to one is perceived as exceeding their ability to cope which is based on their appraisal of the situation

Psychological factors that contribute to perception of stress

• prior experience with stressors

• personality

• level of self-esteem

• motivation

• coping skills

Cognitive functions due to stress includes changes to

• thinking

• learning + memory

• attention

Psychosomatic illnesses

= physiological symptoms that are experienced as a result of psychological stressors

why do they occur?

As stress suppresses the immune system, it allows for viruses and bacteria to attack

• eg. cold sores

Lazarus and Folkman’s Transactional model of stress & coping

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Need to apply this model

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Aims to describe and explain individual differences based on how individuals respond to a stressor from a psychological perspective and their assessment of the events significance as well as their coping abilities

Primary appraisal (evaluates the situation)

Benign / positive = no stress

Irrelevant = no stress

Stressful

Challenge

• potential for personal growth or positive outcome

Harm / Loss

• how much damaged has already occurred

Threat

• assessment of the potential harm/loss that may occur in the future

Secondary appraisal (evaluates resources for coping)

Adequate coping strategies

yes - no stress no - stress

Coping flexibility

refers to the ability to modify coping strategies to meet the demands of different stressful situations

• recognise whether use of a coping strategy is appropriate

• ability to discontinue a coping strategy and implement a new and alternative one that is more effective

Context-specific effectiveness

refers to when a coping strategy matches / is appropriate to the situation

Coping strategies - approach / avoidance

Approach involves efforts to confront a stressor and actively deal with it and its effects

benefits

• generally more adaptive and effective

• individuals tend to experience fewer psychological symptoms and function more effectively

• promotes resilience and reduces likelihood of prolonged distress

limitations

• some stressors cannot be actively dealt with

• ineffective if the stressor is out of ones control

• may initially / in the short term increase stress levels

Avoidance involves efforts to not deal directly with a stressor

benefits

• effective when out of ones control / dealing with unchangeable aspects

• allows you to conserve energy to focus on other stressors that can be changed

limitations

• tend to be maladaptive

• excess reliance can lead to mental health problems, stress related physical problems

• long term use can prevent individuals from responding to stressors effectively

• delaying stressor can lead to greater stress and can be detrimental when action is required