MODULE 8 - Non-Infectious Disease and Disorders

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Homeostasis

the process by by which organisms can maintain a relatively stable internal environment, despite a changing external environment

includes: The nervous system, endocrine system

Receptors

a stage of homeostasis:

• recieves stimulus

• includes: patches of sensetive nerve cells, complex organs such as eyes and ears in mammals

Effectors

a stage of homeostasis:

• respond to the change (detected by stimulus) and restore the organism to the stable state

• can be muscles or glands

Muscles

respond to stimuli by contracting or relaxing → bringing about movement

Glands

respond to stimuli by secreting hormones

e.g. pancreas secretes insulin in response to an increase in blood sugar levels

Feedback

when outputs of a system are routed back into the system as an input

negative feedback loop

deviation from stable state results in a response to counteract this in order to achieve homeostasis. More common

• e.g. body temp, blood glucose levels are controlled by ___

postitive feedback loop

deviation away from stable state which results in an amplification of the change, deviating further away from homeostasis. More uncommon.

• e.g. uterine contractions during childbirth, blood clotting

thermoreceptors

found in the hypothalamus, detect temperature of blood circulating body

Control of Body Temperature

Controlled by hypothalamus and pituitary glands in brain

Thermoreceptors in hypothalamus detect change

responses include: sweating/vasodilation or goose bumps/shivering/constriction of blood vessels

Control of Blood Glucose

• Controlled by pancreas: secretes insulin and glucagon

• negative feedback

Insulin

Plays role in blood glucose feedback

• promotes ↓ in blood glucose through synthesis of glycogen and cellular uptake of glucose

Glucagon

Plays role in blood glucose feedback

• promotes ↑ blood glucose through breakdown of glycogen and synthesis if glucose from amino acids

Endotherms

organisms whose body temperatures maintain fairly constant (e.g. humans and euro [mammals] and birds [kookaburra]

ambient temperature

temperature of external environment (not body temp)

Ectotherms

organisms whose body temperatures vary with the environment around them (ambient temp)

e.g. reptiles [blue tounged lizard], amphibians [frog]

adaptation

an inherited characteristic, process or behaviour that is of benefit to an organism (facilitates it’s survival in a certain habitat)

Behavioural adaptation

change in the activities and behaviours of an organism e.g. hibernation, nocturnal

Structural adaptation

change in the physical characteristics of an organism e.g. body shape and size, large thin ears

Physiological adaptation

change in the processes carried out by the structure e.g. sweating

Coordination

____ systems in the body work to achieve and maintain homeostasis

• includes the nervous and/or endocrine system

CNS (Central Nervous System)

consists of: the brain and spinal cord

function: transmits messages to and from the brain and controls spinal reflexes

PNS (Peripheral Nervous System)

consists of: branching networks of nerves. all nerves enter or leave CNS

Neurons

contain bundle fibres, either axons or dendrites, surrounded by connective tissue

function: to carry out the functions of the nervous system by conducting nerve impulses

main parts: cell body, dendrites, exon

dendrites

part of neuron

• extensions that project from the cell body

• recieves singals from other neurons and carry them to the body

axon

part of neuron

• carries messages away from the cell body

myelin sheath

covers many neurons

• white, fatty substance

sensory neuron

arise from sensory receptors (e.g. eyes, ears, taste buds) as well as internal receptors for hunger, thirst, body position, pain etc.

function: to carry messages to the CNS for processing

interneurons

connects sensory and motor neurons and are located in the CNS

function: carry impulses from sensory to motor neurons

motor neurons

function: carry impulses away from the CNS to effectors (muscles and glands that carry out the response)

synapse

gap between neurons that impulse must cross (2 types)

electrical synapse

type of synapse

• contain specialised integral proteins, gap junctions which form channels that span across the synapse.

• They connect the two nerve cells and allow impulse to travel from one neuron to the next by an electrical signal

chemical synapse

type of synapse

• neurotransmitters are released from axon terminals into the synaptic cleft

• They diffuse across the cleft and bind to receptor on the dendrite of the next neuron

• This may or may not trigger nerve impulse (depends on how much of the chemicals are secreted)

Nervous control

Usually follows these steps:

1. Stimulus

2. Receptor

3. Control centre (CNS)

4. Effectors

5. Response

Stimulus detection (NC)

Step 1 of nervous control

• Change is detected in internal or external environment

• e.g. (change in CO2 levels, internal temp) or (sound, vibration, odours, touch)

Receptor

Step 2 of nervous control

• detect stimulus and convert it into electrochemical impulses

• Transmitted by sensory neurons in one direction to the CNS

RECEPTORS INCLUDE:

• photoreceptors

• thermoreceptors

• mechanoreceptors

• chemoreceptors

photoreceptors

detect light (found in eyes)

thermoreceptors

detect heat (found in the skin and the hypothalamus)

mechanoreceptors

detect pressure, sound, touch, gravity (found in skin and inner ear)

chemoreceptors

detect taste and smell (such as olfactory receptors in the nose and taste buds)

Control centre

Step 3 in nervous control

• Response reaches CNS → carried by interneurons to the brain

• Can be sent to different parts of brain which are associated with diff functions

  • Hypothalamus - maintaining homeostasis (e.g. body temp)

  • cerebullum - muscular activity (e.g. posture and balance)

  • brainstem - control of heart, blood vessels and lung ventilation

  • cerebral cortex (cerebrum) - motor activity, sensory input, speech, sight and hearing

Effectors

Step 4 of nervous control

• motor neurons carry impulses from spinal cord to effectors

TYPES OF EFFECTORS:

• muscles (e.g. skeletal and smooth muscles in stomach)

• glands (e.g. endocrine)

• organs

Response

Step 5 of nervous control (final step)

• muscle or gland stimulated by motor neuron responds accordingly

reflex

an automatic response to stimulus involving a small number of neurons

• does not need conscious thought

• rapid response to stimuli

reflex arc

Steps:

1. sensory neuron → spinal cord

2. interneurons interpret stimuli

3. message relayed to motor neurons → response produced

membrane potential

neurons have an electrical charge difference across their cell membranes causing potential difference.

*due to different concentrations of Na+ and K+ ions

Action potential

a rapid and short change in membrane potential of an exciteable cell

• In nerve cells → causes nerve impulse

• muscle cells → contraction

Nerve impulse

Consists of 5 main steps:

1. Stimulus

2. Depolarisation

3. Repolarisation

4. Hyperpolarisation

5. Resting state (or refractory stage)

Resting potential of neuron

-70 mV

∴ inside of the cell is more -ve than the outside, ↑ number of +ve ions outside cell (cell is polarised)

• ion concentration is maintained by:

  • Sodium and potassium ion channels

  • sodium-potassium pumps

Stimulus detection (NI)

Step 1 of nerve impulse

• stimulus is applied → Na+ channels open and NaK channels close 

∴ Na+ rushes into cell, ↑ voltage

• If stimulus is strong enough, V ↑ to the threshold

• difference between threshold and resting potential is the MINIMUM ΔV needed to generate action potential (usually 15mV)

*Threshold needs to be met for the process to continue

Depolarisation

Step 2 of nerve impulse

• Na+ continue moving into cell, ∴ inside of cell more +ve than outside

• Δelectrical potential is called _____

Repolarisation

Step 3 of nerve impulse

• Na+ channels close → prevents Na+ ions entering cell

• K+ channels open and allow K+ ions to leave cell

∴ inside becomes more -ve than outside of cell again

Hyperpolarisation

Step 4 of nerve impulse

• As repolarisation was occuring, the K+ channels closed relatively slowly → inside of cell becomes temporarily more -ve than the resting potential

Resting state (NI)

Step 5 of nerve impulse (final step)

• aka. refractory stage

• NaK pumps open -→ restore conc of ions to the original levels

∴ membrane returns to its resting potential (-70mV)

Endocrine system

system that is composed many ductless glands which secrete hormones into the bloodstream

Hormones

chemical messengers that target specific cells to cause a specific response for maintaining internal homeostasis and internal communication

Hormone coordination

long lasting but relatively slow

• glands need to be activated

• hormones synthesised

• secretion

• transmitted by diffusion into extracellular fluid or bloodstream

• reaches target organ/cells

hypothalamus

links nervous system and endocrine system

• processes sensory information responsible for activities such as:

  • sex

  • hunger

  • thirst

  • pleasure

  • pain

  • anger

Pituitary gland

small gland that lies below the hypothalamus, called the master gland

• controlled by hypothalamus

• stores some hormones produced by the hypothalamus (e.g. ADH and oxytocin)

• produces hormones (e.g. prolactin, FSH, LH, growth hormone)

• secretes hormones to activate other endocrine glands (e.g. TSH → stimulated thyroid, ACTH → stimulates adrenal glands)

Auxins

Found in: shoot and root tips

• Stimulates elongation of cells

• growth

• Photo tropism

• Gravitropism

Cytokinins

Produced by: roots

Found in: embryos and fruits

• Promote cell diversity

• Growth

• Lateral growth and aging

Phototrophism

Plant bending towards the light

Gravitrophism

Response to gravity

Gibberellins

Produced by: young roots and leaves

• Cell elongation and division

• stimulates flowering and fruit developent

Abscisic acid

Produced by: leaves, stems, roots, green fruits

• Inhibits germination

• determines whether seed remains dormant or germinates

Ethylene

Produced by: aging fruits and leaves

• Triggers fruit ripening and other aging provesses

transpiration

water loss (evaporation) in plants via stomata on leaves

xerophytes

plants adapted to low water conditions

halophytes

salt tolerant plants

xeromorphic features

features in halophytes and alpine species of plants

• an adaptation to the scarcity of water and high transpirational losses in these environments

Non-infectious diseases

diseases that aren’t caused by pathogen and can’t be transferred from person to person

genetic diseases

result of mutations in germ-line cells. passed down through generation to generation.

e.g. CF, breast cancer, huntington’s disease

cancer

results from mutation in genetic material, leads to abnormal cell behaviour → leads to uncontrolled cell growth under action of genes called proto-oncogenes

malignant

describes cancer that actively invades and spreads around the body

benign

describes abnormal (potentially cancerous cells) that don’t invade surrounding tissue areas and remain confined, not considered cancerous

malnutrition

deficiencies, excesses, or imbalences in a person’s intake of energy, and/or nutrients

undernutrition

includes:

• wasting (low weight for height)

• stunting (low height for age)

• underweight (low weight for age)

micronutrient-related malnutrition

includes:

• micronutrient deficiencies (lack of important vitamins/minerals)

• micronutrient excess

overweight/obesity and diet related noncommunicable diseases

includes:

• heart disease

• stroke

• diabetes

• some cancers

nutritional diseases

malnutrition:

• undernutrition

• micronutrient malnutrition

• obsesity, overweight, noncommunicable diseases

examples:

• scurvy (vit C deficiency), rickets (vit D deficiency), night blindness (vit A deficiency), anemia (iron deficiency)

Epidemiological studies

includes the collection and statistical analysis of large quantities of data from hospitals, census etc.

impact: provide a picture of incidence, prevalence, mortality of disease, can identify cause, methods of transmission, treatment, controls and long-term measures of prevention

Epidemiology

the study of diseases that affect many people (infectious & non-infectious disease)

descripitve studies

type of epidemiological study

• study of distribution of disease in terms of age, race, ethnicity, sex etc.

analytical studies

type of epidemiological study

• Observational (case-controlled) studies

  • compares diseased individuals (case) to normal individuals (control) → draw conclusions relating to cause and risk factors of disease

  • retrospective

• Experimental (cohort) studies

  • compare individuals who have (or not) been exposed to a particular risk factor → draw conclusions about cause and risk factors of disease

  • prospective

intervention studies

type of epidemiological study

• used to evaluate treatment and prevention methods

• e.g. clinical trials

validity of epidemiological study

1. large sample size (ie large data quantities)

2. includes people from a variety of backgrounds/occupations

3. includes a control group

4. conducted over a long period of time

educational programs and campaigns to prevent disease

aim: raise awareness of risk factors associated with particular diseases

carried out by: NGOs, GOs, Aus gov, state, territory, local gov, private health professionals

types:

• paid advertising

• school-based health education

• screening programs

• policy changes

paid advertising

e.g. “Slip, Slap, Slop” → Cancer Council Victoria (1981) for melanoma rates

School-based health education

e.g. program that targets risks of hazardous and harmful drug use → NSW PDHPE curriculum (active)

screening programs

e.g. “National Bowel Cancer Screening Program” or NBCSP → Aus Department of Health (active) provides a free Bowel screening kit to Australians between 50-75y/o every two years

• early detection of cancer is beneficial

policy changes

e.g. “Tobacco Plain Packaging Act of 2011” → Aus Government

• cigarettes must display health warnings and graphic imagery

genetic engineering

direct manipulation of an organism’s genetic material → has potential to prevent genetic diseases, nutritional diseases and cancers

pre-implantation genetic testing

involves fertilisation via IVF, a single cell is removed from uterus and tested (when blastocyst has 8 cells)

tests for:

• CF

• Huntingtons

• thalassemia

• muscular dystropy

emrbyos that have the disease are discarded: ∴ 100% effective

Mitochondrial Replacement Therapy

• note: mitochondrial diseases passed from mother to child (egg contains way more mitochondria than sperm)

• MRT can be used with IVF to prevent transmission of mitochondrial diseases (involves donor)

diseases:

• Leber Hereditary optic neuropathy (LHON) and MELAS syndrome

Biofortificaiton

↑ nurtitional value of crops

process: selective breeding or genetic modification (↑ value during production rather than after harvestation)

aim: prevent nutritional diseases caused by micronutrient-related malnutrition

examples:

• Golden Rice genetically modified to include two transgenes: one from daffodil and soil bacterium → allows rice to produce beta-carotene, precursor to Vitamin A (for vitamin A defeicieny → leads to blindness in children)

pitch

frequency of sound wave

loudness/intensity

amplitude of waves

mechanoreceptors

responsible for sound reception:

• tiny hair cells in cochlea of ear

pinna

collects and focusses sound waves

tympanic membrane

sound waves travel down auditory channel to here.

• vibrates at the same frequency as the sound