Lecture 3: Biological Bases of Behaviour: The Nervous & Endocrine Systems and the Developing Brain

Module 1: Biological Foundations of BHD Lecture 3: The Nervous & Endocrine Systems and the Developing Brain - Tutorial 1 - Required Readings from Psychology textbook

Biopsychosocial lifespan model

Considers the whole person (biological, psychological and social)

Lifespan model

Early experiences can shape the brain that can impact people throughout the rest of their lives

Frontal lobe and prefrontal lobe

Governs executive functions - organising, planning, attentional control. Regulates behaviour.

The two subgroups of the Peripheral Nervous System

Somatic Nervous System and Autonomic Nervous System

Somatic Nervous System

Carries messages from CNS to muscles throughout the body, controlling and coordinating voluntary movement

Autonomic Nervous System

Controlling the involuntary actions of our internal organs and glands, which (along with the limbic system) participates in emotion regulation

Subgroups of Autonomic Nervous System

Sympathetic Nervous System and Parasympathetic Nervous System

Sympathetic Nervous System

Division of the autonomic nervous system engaged during a crisis or after actions requiring fight or flight (emergency situations)

Parasympathetic Nervous System

Division of the autonomic nervous system that controls rest and digestion (everyday situations)

Function of frontal lobe and pre-frontal cortex

Higher cerebral functions, abstract thought, planning, decision making.

Function of Hippocampus

New learning and formation of memory

The Hippocampus and depression

Smaller in depression - more depression related to smaller hippocampus

Function of Amygdala

Emotion centre of the brain; processes feeling. Plays key roles in fear (fear conditioning - predicting when something scary is about to happen)

The Amygdala and depression

Higher activity with depression

Function of Hypothalamus

Regulates motivated behaviour (heart rate, temperature, thirst, sexual motivation)

Hypothalamus and depression

Key in stress response system (HPA axis) and triggers stress response

Function of Thalamus

Major relay system of the brain: Sends signals to other parts of the brain to interpret information

Stress response system (HPA axis)

Stress perception triggers hypothalamus to release cortisol releasing hormone (CRH). This triggers the pituitary gland to release corticotropin (ACTH), which stimulates the adrenal glands (located on the kidney) to release cortisol and other hormones into the immune system to prepare the body to deal with the stressor.

Characteristics of Depression

• Weight loss/gain (changes in appetite)

• Sleep disturbances

• Loss of pleasure in things they previously enjoyed

• Problems thinking, concentrating

• Isolation, withdrawl from friends & activites

• Feelings of helplessness & hopelessness

Depression and GBD (noncommunicable diseases)

Depression ranks 2nd in the Global Burden of Non-communicable diseases and is the leading risk factor for suicide

Neurotransmitters associated with depression

Serotonin, Dopamine, Norepinephrine (adrenaline), Acetylcholine, Glutamate, GABA

What is dopamine associated with?

Reward and pleasure

What is Acetylcholine associated with?

Memory, learning, recall

What is Glutamate involved with?

Bipolar disorder

Serotonin levels in people with depression

Lower levels of serotonin in people with depression

What does GABA do?

Reduces anxiety

The hormones associated with depression

Cortisol, Estrogen and testosterone

Cortisol in depression

Is higher

Estrogen and testosterone in depression

Is lower

Brain development at 6 months

Neurons start to connect with other neurons around them

Brain development at 2 years

Many more connections between neurons - connectivity is important in the brain

Sequence of brain development

Primitive areas, Cortical areas and Prefrontal cortex

Brain development of Primitive areas

Limbic system develops over the first three years (emotional development) - baby develops a sleep cycle

Brain development of Cortical areas

The development of thinking and cognitive processes

Brain development of the Prefrontal cortex

Controls executive functions - develops middle childhood into adulthood (mid 20’s)

The optimal environment for a baby and why

A warm and responsive caregiving relationship - environment must be nurturing and responsive during this time to optimise positive development it is a sensitive time period where the brain is vulnerable

Positive or normal stress

Moderate, short-lived stress responses are normal part of life & learning to adjust to this kind of stress is adaptive

Tolerable stress

Serious illness, frightening accident, parental separation - tolerable if there is parental support that creates a safe environment. (e.g. a parent is hospitalised - child is away from parent for a period of time)

Toxic stress

Strong, frequent or prolonged activation of the body’s stress management system - stressors are chronic, uncontrollable & are experienced without the support of a caring adult.

When does toxic stress usually occur?

When in a harsh environment - maltreatment and neglect of children. The absence of the warm, responsive caregiving relationship

What does prolonged periods of stress mean in children? (constant activation)

Toxic stress resulting in a stress response system set permanently on high alert

Features of Occasional Inattention

Intermittent, diminished attention in an otherwise responsive environment

Effects of Occasional Inattention

Can be growth promoting under caring, supportive environments

Features of Chronic (ongoing) Under-stimulation

Ongoing, diminished level of child-focused responsiveness & developmental enrichment

Effects of Chronic (ongoing) Under-stimulation

Often leads to developmental delays and may be caused by a variety of factors

Child stress scenario in a caring household

When a child is stressed, the HPA axis (stress response system) activates - then a caring caregiver calms them down and relieves their stress and the body quickly returns to normal.

Child stress scenario in a toxic/neglected household

No caring adult present to act as a buffer against stress so the stress response stays activated

Example of child stress in a neglected household

The extended period of time away from parents can trigger the stress response system

Clinical presentations of toxic stress

• Hyperactivity - problems regulating activity level/behaviour

• Child appears withdrawn

• Hyper vigilance (stress response system becomes easily triggered)

• Child presented with learning problems

What does contuinous exposure to cortisol due to high stress levels mean?

The functions of other organs of the body will be affected. High stress levels —> physical problems

Adrenaline

Mobilises energy stores and alters blood flow, thereby allowing the body to deal with a range of stresses

Cortisol

Mobilises energy stores, suppresses immune responses

What has sustained levels of cortisol shown?

To damage the hippocampus, leading to impairments to regulate certain stress response

What is the leading cause of death for males in NZ?

Ischemic heart disease

Behavioural patterns contribution (%) to premature deaths

Contribute 40% to premature death

Genetic predisposition contribution to premature deaths

Contributes 30% to premature death

Social circumstances contribution to premature deaths

Contributes 15% to premature death

Health care contribution to premature death

Contributes 10% to premature death

Environmental exposure contribution to premature death

Contributes 5% to premature death

Tolerance

Reduction in the effect of a drug as a result of repeated use, requiring users to consume greater quantities to achieve the same effect

Withdrawal

Unpleasant effects of reducing or stopping consumption of a drug that users had consumed a lot of

Physical dependence

Dependence on a drug that occurs when people continue to take it to avoid withdrawal symptoms

Psychological dependence

Non-physiological (body) dependence on a drug that occurs when continued use of the drug is motivated by intense cravings

Hypnotic

Drug that exerts a sleep-inducing effect

What drug is categorised as a depressant?

Alcohol (and sedative hypnotics)

Stimulant

Drugs that increase activity in the central nervous system (CNS) including heart rate, respiration, and blood pressure.

What neurotransmitters does cocaine increase the activity of?

Dopamine

Narcotic

Drug that relives pain and induces sleep (e.g. opioid drugs such as heroin, morphine, and codeine)

Hallucinogenic

Causing dramatic alternations of perception, mood, and thought (e.g. marijuana)

Psychoactive drugs

Substance that contains chemicals similar to those found naturally in our brains that alter consciousness by changing chemical processes in neurons.

Pituitary Gland

Referred to as the "master gland" because it produces and releases hormones that regulate the activity of other endocrine glands in the body

Endorphins are the neurotransmitters that..

act as natural painkillers