Psych Unit 3

CNS

Transmission and reception of neural information to and from the peripheral nervous system.

CNS brain role

Organising, interpreting and integrating neural information

CNS spinal cord role

Relay station between brain and peripheral nervous system

PNS

Carries messages to and from the CNS

PNS - Somatic NS

Carries sensory info to CNS and motor info from CNS to initiate voluntary movements

PNS - Automatic NS

• Carries neural messages between CNS and internal muscles, organs and glands

• Self-regulating and controls involuntary and autonomic functions that people don’t normally think about

Parasympathetic NS

• Calms body down after arousal

• Maintains homeostasis

Sympathetic NS

Prepares body by activating visceral muscles, organs and glands for vigorous activity or to deal with a stressful or threatening situation

Enteric NS

• Controls digestive system and is directly connected to CNS

• ENS has 2 way connections to CNS and the 2 systems work together to control digestive system

• ENS completes some functions independently of the brain

• Multiple roles:

  • detecting physiological condition of gastrointestinal tract

  • integrating information about state of gastrointestinal tract

  • controlling gut movement

  • nutrient management

  • regulating gastric secretions

Sensory Neurons (somatic NS)

• Afferent Neurons

• Carry/relay sensory info from sensory receptors in body to spinal cord

Interneurons (Central NS)

• Transmits info within CNS

• Relays messages between sensory and motor neurons within CNS

Motor Neurons (Somatic NS)

• Efferent Neurons

• Carry/relay motor info from spinal cord to muscles for voluntary bodily movements

Conscious Response

1. Sensory neurons carry the sensory information of seeing Batata occupying her space to the spinal cord.

2. Interneurons in the spinal cord send the information to the brain.

3. The brain would process this information as a voluntary, conscious response.

4. The brain sends a neural messages to the skeletal muscles in Martha's lower end so that she can sit on Batata via motor neurons.

Unconscious Response

1. Sensory neurons carry the sensory information of feeling extreme heat at the head to the spinal cord

2. Interneurons in the spinal cord send/relay a signal via motor neurons to initiate an automatic/unconscious motor responses of moving his hat away from the heater

GABA

• Primary inhibitory neurotransmitter  

• Suppress or slow down post-synaptic neuron activity, decreasing the likelihood of firing  

• Essential in maintaining neurotransmission at an optimal level 

Glutamate

• Primary excitatory neurotransmitter  

• Enhances information transmission by making post-synaptic neurons more likely to fire 

• Essential in the formation of long-term memory and learning 

GABA + Glutamate

The inhibitory action of GABA counterbalances the excitatory activity of glutamate and vice versa. Consequently, GABA and glutamate have important roles in regulating CNS arousal. 

Dopamine

• excitatory or inhibitory effect on neurons 

• brain’s dopamine-producing areas and neural pathways are collectively known as the dopaminergic systems

dopamine - reward seeking behaviour

• reward seeking behaviour

  • Dopamine release produces feelings of pleasure and euphoria.

  • Released during certain behaviours, creating a desire to repeat the behaviour.

  • great for reward based learning, harmful for gambling and drug addictions

  • high dopamine is linked to hallucinations in schizophrenia

dopamine - coordinating movements

Neurons in substantia nigra in midbrain produce dopamine which travel to primary motor cortex to coordinate muscle movements

• Damage to dopamine-producing neurons causes irregular or reduced messages to muscles, resulting in muscle rigidity and stiffness in Parkinson’s disease

Serotonin

• Has inhibitory effect.  

• Produced in brainstem and travels through serotonergic system

serotonin - mood stabiliser

Allows us to feel calm, and have a stable mood. 

• Low levels associated with mood disorders such as depression and anxiety disorders (OCD) 

serotonin - sleep-wake cycles

Works with pineal gland to produce melatonin (feels sleepy)

• Increased levels of serotonin reduces the amount of REM sleep 

Synaptic Plasticity

Ability of synapse to change over time

LTP

Long-lasting strengthening of synaptic connections. Repeated high-intensity stimulation by neurotransmitter between pre- and post-synaptic neurons 

LTP steps and role

1. Increase in the amount of neurotransmitters 

2. Greater effects of neurotransmitters at the receptor sites 

3. Result in sprouting and rerouting

Repeated use of information strengthens neural pathways through LTP, making information easier to retrieve

LTD

Long-lasting weakening in the strength of synaptic connections. Repeated low-intensity stimulation by neurotransmitter between pre- and post-synaptic neurons

LTD steps and role

1. Neurons being less responsive to neurotransmitters  

2. Result in pruning  

• Clears old memories and unused neural pathways

• Corrects thinking during problem-solving and adjusts movements when learning new motor skills.

Structural changes of synapses - Sprouting

Growth of additional axons or dendrites to enable new connections with other neuronsand increased, more flexible neural communication.

Structural changes of synapses - Rerouting

In response to damaged synaptic connections, healthy neurons develop alternate neural pathways to compensate for damage and restore brain functioning.

Structural changes of synapses - Pruning

Elimination of weak, ineffective, unused synapses (and therefore connections to other neurons) to encourage increased efficiency of neural communication.

Stress

State of physiological or psychological arousal produced by internal or external stressors, that are perceived by individual as challenging or exceeding their ability to cope.

Stressor

Stimulus that contributes to stress.

• Internal Stressor

  • originates within the individual

• External Stressor

  • originates outside the individual from situation or events in environment

Acute Stress

Stress that lasts for a relatively short time.

• Body can bounce back quickly

• Beneficial to help us deal with challenges

Acute stress - fff response

• Involuntary, physical reaction that occurs in response to sudden and immediate threat.

• Adaptive responses to deal with threat at hand and help minimise it.

  • Fight - confronting and fighting off the threat

  • Flight - escaping and running away to safety

  • Freeze - keeping still and silent, avoiding detention.

fight-flight response

• When we respond by fighting or fleeing a stressor sympathetic nervous system is dominant over the parasympathetic nervous system

• Sympathetic NS sends message to adrenal glands to secrete hormones adrenalin and noradrenalin to activate various organs for FFF response

Freeze response

• Both sympathetic and parasympathetic NS are active, but parasympathetic is dominant

• Conserves energy until threat has passed or organism can act

Chronic Stress

Stress that continues for a prolonged period of time.

• Likely to be harmful for psychological and physical health

• Can be debilitating and overwhelming

cortisol

• Stress hormone produced by adrenal glands

• Cortisol acts more slowly and is longer lasting than adrenaline and noradrenaline

in chronic stress, cortisol:

1. Keeps the body at an elevated level of arousal

2. Energies the body by increasing energy supplies and enhancing metabolism

3. Diverting energy from non-essential bodily functions such as digestion and immunity

Excessive amount of cortisol over prolonged period of time:

1. Impaired immune system functioning

2. Increased vulnerability to disease/infection or other physical problems

3. Slows healing

4. Psychological problems, e.g. impaired cognitive performance

GBA

Bidirectional, multi-faceted communication link between the central and enteric nervous systems (vagus nerve). It connects cognitive and emotional areas in the brain with the gastrointestinal tract.

Gut microbiota, stress and nervous system function: emerging research

• Stress alters gut microbiota composition and deficiencies in certain bacteria, linked to anxiety and depression.

• Stress-associated microbiota increase anxiety-related behaviours.

• Early-life or adult stress exposure can change an organism’s microbiota composition.

• The types of microbes in the gut shape stress responsiveness.

• Treatment with healthy microbiota reduces anxiety-like behaviour in humans and mice.

Gut Microbiota

Every individual has a personal composition of gut microbiota, therefore no standard definition of a healthy gut microbiome.

• Comprised of all bacteria, viruses and fungi present in the digestive tract

• Gut microbiota and brain communicate with each other in the GBA

features used to determine an individuals gut health:

• Number of different species of microbiota (microbiota richness)

• Diversity of microbiota

• Stability of population

• Resilience to change

General Adaptation Syndrome

• A three-stage physiological response to stress

• Occurs regardless of the stressor that is encountered