Health Psychology Chapter 2 - Systems of the Body

Nervous System

Nervous System communicates via chemical signals called neurotransmitters

1. CNS (Central Nervous System)

   1. brain

   2. spinal cord

2. Peripheral nervous system

   1. somatic nervous system

   2. autonomic nervous system

      1. sympathetic nervous system: “fight or flight”

      2. parasympathetic nervous system: “rest and digest”

CNS (Central Nervous System): Brain

Hindbrain

• medulla: regulates HR (heart rate), BP (blood pressure) and respiration

• pons: controls respiration

• cerebellum: coordinates voluntary muscle movement & maintains balance & equilibrium, muscle tone & posture

Midbrain

• coordination of vidual and auditory reflexes

Forebrain

• cerebral cortex

• hypothalamus

• amygdala

• hippocampus 

Limbic System: Stress & Emotional Responses

• hypothalamus: releases hormones, linked to emotional functioning

• amygdala: general arousal, threat detection

• hippocampus: memory (emotional)

CNS involved in SNS activation

SNS activation triggers release of catecholamines (type of neurotransmitter)

• epinephrine & norepinephrine

orchestrates a host of systemic (stress-like) responses simultaneously

• cardiovascular: increased HR, blood vessel constriction, BP

• Respiratory: increased respiration, airflow into lungs

• Digestive: decreased digestion and urination 

Nervous System: Diseases 

• epilepsy 

• parkinson’s disease

• cerebral palsy

• multiple sclerosis 

• huntington’s disease

• dementia/alzheimer’s disease 

  • amyloid & tau (protein) deposits in the brain

  • cerebrovascular disease

  • sleep (lack of) as sleep removes amyloid

Endocrine System

made up of several glands that secrete hormones into the blood stream to stimulate activity in the organs

1. pituitary glands

   1. and the hypothalamus regulate the endocrine system

2. adrenal glands

   1. made up of the adrenal medulla & adrenal cortex

   2. secrete hormones implicated in stress response

in response to stress, activation of the HPA axis (hypothalamic-pituitary-adrenal-axis)

Endocrine System: Diseases

• diabetes: chronic inability to manufacture or properly use insulin

• Type I Diabetes: autoimmune disorder where the immune system erroneously destroys body’s own cells that are needed to produce insulin 

  • early in life

  • partly genetic

• Type II Diabetes: insuff insulin produced by the body

  • largely lifestyle related

  • typically happens after 40

• comorbid with coronary heart disease & kidney disease

Cardiovascular System

• BP (Blood Pressure)

• PEP (Pre-ejection period)

• CO (Cardiac Output)

• TPR (Total Peripheral Resistance)

BP (Blood Pressure)

force on the blood vessel walls from systolic and diastolic processes

• systole: heart contracts, pump blood out

• diastole: heart relaxes, take in blood 

PEP (Pre-ejection period)

time between left ventricle contraction and aortic valve opening 

• a pure measure of SNS activation

CO (Cardiac Output)

volume of blood pumped per min

• indicator of cardiac functioning

TPR (Total Peripheral Resistance)

vascular resistance to blood flow

• index of “stiffness” in the arteries

Cardiac Efficiency

High cardiac efficiency

• blood pumped quickly (short PEP), in high volumes (high CO) and at low resistance (low TPR)

• physically fit individuals 

Low cardiac efficiency

• blood pumped slowly (low PEP), in low volumes (low CO), at high resistance (high TPR)

• physically unfit individuals 

Heart-Rate-Variability (HRV)

or vagal tone

is the variation in time between heart beats

variability occurs when the vagus nerve exerts control of the heart i.e. PNS activity

Heart Rate: is the no. of heart beats in 1min (norm is 60-100bpm)

in general, higher HRV (vagal tone) is associated with

• better fitness

• better adaptability

• better cognition

• better general health

• lower SNS activation in response to stimuli/stressor

• higher HRV “car accelerator & brake”: PNS activity is akin to applying a brake to reduce SNS activity. this balancing contributes to inter-beat variability. the amount of such variability is HRV. high HRV indicates body’s ability to continuously balance itself in response to any stimuli.

• lower HRV not alw bad: HRV decr from baseline whenever you engage mental effort 

Cardiovascular System: Diseases

• Atherosclerosis: narrowing of arteries due to deposits of substances (mostly cholesterol) on arterial walls

• Hypertension (or high blood pressure): too high CO or TPR

• Thrombosis: clotting of blood vessels 

Respiratory System

Inspiration: causes lungs to expand in the thorax, oxygen is brought in

Expiration: reduces vol in the lungs, CO₂ is elim from the system

The lungs are connected to the heart through the pulmonary artery and pulmonary vein

Respiratory System: Diseases

• Bacterial infection (e.g. sore throat, tuberculosis)

• Viral infection (e.g. common cold, covid-19)

• Pneumonia

• Lung cancer: malignant cancer cells in the lungs that grow into a tumor. smoking is pri cause

Immune System

how the body deals with transmission of disease by infection — the invasion and growth of microbes in the body 

microbes can spread via:

• direct transmission

• indirect transmission (air, water)

• biological transmission (mosquito bite)

• mechanical transmission (typhoid mary)

Immunity

is the body’s resistance to invading organisms

How to acquire:

• natural immunity

  • breastfeeding, passed from mother to child

  • through getting a disease

• artificial immunity

  • vaccinations and inoculations

Immune System: Mechanisms

1. nonspecific: general responses to any kind of infection

• types of responses

  • anatomical barriers

  • phagocytosis

  • antimicrobial substances

  • inflammatory responses

2. specific: fight particular kinds of microbes 

• types of responses

  • lymphocytes

nonspecific immunity is triggered as first defence

specific immunity is triggered several days after to mount full defence

Immune System: Nonspecific Mechanism 

general responses to any kind of infection

Anatomical barriers: block microbes from the body 

• skin, mucus membrane lining nose and mouth

Phagocytosis: is triggered by the production of phagocytes (white blood cells) that eat up microbes

Antimicrobial substances: are chemicals produced by the body that kill microbes

• HCl (hydrochloric acid mostly in stomach), enzymes

Inflammatory responses: are reactions to infection

• histamine released into site of infection, incr blood and fluids to the side

• clot forms around site to isolate the microbes prevents spread to other areas

• e.g. reddening, swelling from insect bites, runny nose from allergies

Immune System: Specific Mechanism 

fights particular kinds of microbes 

• lymphocytes are cells with unique receptors on their surfaces that fit with only 1 kind of antigen (responds to only one kind of “invader” or microbe)

• when activated, lymphocytes divide and create a population of cells 

• compared to nonspecific immunity, specific immunity is slower 

Disorders related to the Immune System

• AIDS

• Tonsillitis

• Lymphoma

• Covid-19

• Autoimmune disease: occurs when body fails to recognise its own tissue, interprets it as an invader and attacks it

  • e.g. Type 1 diabetes, rheumatoid arthritis, lupus

Immune System: Diseases 

infectious diseases are generally under control due to vaccinations that create immunity 

Herd immunity: indirect protection from an infectious disease that happens when a population is immune (impt as not everyone can take vaccines like children, elderly, pregnant women)

chronic inflammation (particularly due to stress) is implicated in chronic diseases 

Genetics & Health

genetic studies have provided valuable info about the heritability of a wide-range of diseases

Types of genetic studies:

• family studies: compare related indivs VS unrelated

• twin studies: compare identical twins VS frat twins VS non twin siblings

• adoption studies: compare adopted child with biological parents/siblings (genetic) VS adoptive parents/siblings (environment)

Issues

• ethical issues: fosters fatalistic beliefs about one’s health and deters behavioural change. elicits defensiveness and downplaying of risks

• Genetic counselling: should people with a family history for certain diseases be screened for genetic vulnerabilities (impt life decisions, treatment decisions)

• learning about one’s genetic risk is not distressing in the long run, especially for those with treatable disorders. but chronically anxious indivs do suffer more distress and require counselling