Biology Unit Two: Homeostasis and Infectious Disease

Vocabulary flashcards covering the Nervous System, Homeostatic Regulation, the Endocrine System, Thermoregulation, and Infectious Diseases based on Biology Unit Two notes.

CNS

The Central Nervous System, which consists of the brain and spinal cord.

PNS

The Peripheral Nervous System, which consists of all other nerves in the body and sends signals from sense receptors to the CNS.

Cerebellum

Part of the brain that controls body movement, posture and balance.

Cerebrum

Part of the brain that controls memory, emotion and language, and sensory processing.

Thalamus

The relay centre for the brain.

Hypothalamus

Part of the brain that controls homeostatic functions such as appetite, thirst, body temperature and sleep.

Brainstem

Assists the hypothalamus in controlling homeostasis in automatic functions such as heart rate, breathing and cough/vomit reflexes.

Dendrites

Branches at the top of the neuron that recieve chemical signals secreted over the synaptic cleft.

Stoma

The cell body of a neuron that processes chemical signals into eletrical signals to create action potential.

Axon

A cable transmitting action potential down the neuron towards the axon terminals.

Myelin Sheath

A fatty substance coating the axon to protect the eletrical signal and ensure fast, clear communication.

Schwann Cell

A cell in the myelin sheath assisting in the proper flow of the signal down the axon.

Node of Ranvier

Connects the myelin sheath to the axon and each other, allowing the electrical signal to “jump” down the axon.

Sensory Neurons

Neurons that gather information from receptors to go to the CNS.

Interneurons

Neurons found in the CNS connecting sensory and motor neurons together.

Motor Neurons

Neurons that take messages from the CNS to the effector organ to cause a response in the muscle, organ, or gland.

Reflex Arc

A pathway in the brain allowing nerve impulses to have an immediate response through fast unconscious movements that bypass the brain.

Optimum Range

The range in which the human body is at its peak performance within its tolerance limits.

Homeostatic mechanisms

Processes that produce a stable internal environment by maintaining variables within a narrow limit, such as body temperature between $36.1-37.8\,^{\circ}C$.

Stimulus Response Model

The model all responses in the body follow: Stimulus \rightarrow Receptor \rightarrow Modulator/Control Centre \rightarrow Effector \rightarrow Response.

Negative Feedback Loops

Acts as a counteract to the original change to return the body to the normal levels.

Positive Feedback Loops

Mechanisms that increase normal values from the ideal ranges, such as in pregnancy and giving birth.

Osoregulation

The maintenance of water and electrolyte levels in the body, primarily involving the kidneys.

Exocrine Glands

Glands that secrete through ducts, such as sweat glands.

Endocrine Glands

Glands that secrete hormones directly into the blood stream, such as the adrenal gland.

Structural Mechanisms

Physical or body structures of an organism used to maintain ideal body temperature, such as elephants flapping their ears.

Hibernation

A prolonged time of reduced activity where metabolism slows to keep the animal warm.

Torpor

Reduced metabolic activity during sleep in colder months.

Astivation

A form of hibernation occurring in warm months to reduce energy and water loss.

Kleptothermy

A behavioral mechanism where animals share the metabolic thermogenesis of other animals, such as penguins huddling.

Pathogens

The overall category of harmful organisms that cause infectious disease, including bacteria, fungi, protozoa, and viruses.

Bacillus

Rod-shaped bacteria.

Coccus

Sphere-shaped bacteria.

Spirillus

Spiral-shaped bacteria.

Binary Fission

The process of DNA replication and division used by single-celled bacteria.

Disease

Where normal bodily functions fail in some way

Infectious Disease

Illness caused by the invasion of a harmful organsim in the body

Bacteria

• Microbe = bacteria

• Classed into 3 groups: bacillus (rods), coccus (spheres), spirillus (spirals)

• Single celled organisms that undergo binary fission (DNA replication)

• Genetic material not contained in the neuclus

Virus

• Not classified as living; need a host in order to live

• Intracellular parasite → found inbetween cells

• Host range = spectrum of host cells the virus can invade

Infection of a Virus

Receptor-Mediated Fusion

• Bonds to a specific receptor on a cell so a virus can inject it’s DNA. Cell with replicate the DNA and then explode

Endocytosis Pathway

• Whole virus will be engulfed through a vesicle so it can pass through the plasma membrane and enter a cell

Multicellular Parasites

Endoparasites are specialised to live in the host and cause disease directly (e.g. tape worm)

Ectoparasites act as a vector (host) by carrying the disease to pass on (blackdeath being carried by fleas to pass onto humans)

Virulence Factor

• Characteristics of pathogens enhancing their ability to cause a disease

Adherence Factor → Ability to attach to a host’s cell receptors (e.g. pili in bacteria)

Invasion Factor → How it get’s inside your body or a cell (e.g. enzymes breaking down tissue)

Capsules → Protective outer layer surrounding bacteria

Toxin → Substances produced that damage host tissue (e.g. mosquito venom that dirupt platelets that causes you to bleed more)

Life Cycle → Adaptations in a pathogens life cycle that enhance speed and survival (e.g. Paradite reproduction is fast)

Transmission of Disease

Contact Transmission → transmission by touch

Vechile Transmission → Needs something to hold onto

Vector Transmission → Needs a living organism

1st Line of Defence

The external stopping of harmful pathogens from invading the body. This is a type of physical defence that prevents the entry of pathogens.

2nd Line of Defence

White blood cells in the body to initate a phisological response. This is a type of chemical defence that kills or harms the pathogens

Cells in the 2nd Line of Defence

Esoinophils → produce toxins against certain pathogens

Basophil → release of heparin/histamine to cause inflamation

Neutrophil → cells engulf and destory foreign material

• Engages natural killer cells (NK cells) and white blood cells that are specific for killing infected and disease cells

Phagocytes

• White blood cells that ingest microbes by phagocytosis:

1. Detection → detects microbes by the chemicals they give off

2. Ingestion → phagocyte wraps pseudopodia around the microbe engulfing it

3. Phagosmome forms → phagosome is formed enclosing microbe in a membrane

4. Fusion with lysosome → phagosome fuses with lysosome for acids and chemicals to digest

5. Digestion → microbe is broken down by enzymes

6. Discharge → material is discharged from phagocytes

*Pseudopdia = membrane forming a vesicle

*Phagosome = what the vesicle is called once engulfed

Inflammation

• The increase of blood flow to a damaged area surrounding a pathogen

• white blood cells destroy the cause of infection

• red blood cells (for oxygen) and platlets (for clotting) repair the tissue

The Complement System

• group of proteins in the blood to defend against infection

• Causes a cascade: chain reaction where proteins are activiated leading to the formation of membrane attack complex

• Activation of cascade occurs 3 ways:

• 1. Classical - triggered to antibodies binding to pathogens

• 2. Lectin - proteins recognise specific sugars on bacteria or virus surface

• 3. Alternative - sponanteous activation but is enhanced by presence of pathogen

Fever

When temperature rises above 37 degrees, pushing the bacteria out of their opitumum range, killing it. Fevers set off the complement cascade causing an interferon

*Interferon → chemical stopping the replication of bacteria

3rd Line of Defence

Physiological adaption of cells in order to become specific to a pathogen

Lymphatic System

Part of the 3rd Line of Defence, consisting of a network of vessles that drain the fluid.

Contains lymph nodes that actively fight off a pathogen

B-Cells

Create antibodies to target antigens

• Can either be memory cells or plasma cells

• Memory Cells → when cells encounter some antigens, they rapidly differentiate into antidoy-producing plasma cells

• Plasma Cells → Secrete antibodies against antigen

T-Cells

• Defends against intracellular bacteria and viruses by tightly squeezing between cells

• Different types of T-cells have different jobs (e.g. Helper T-Cells that call for help to come)

Antigen

Protein mark identifier on the outside of cells and pathogens

Antibody

Folded proteins that are specific to an antigen in a lock & key method to destroy the antigen

Cell Mediated Immunity

1. Antigens are identifed by killer T-Cells

2. Helper T-Cells call for more T-Cells

3. Killer T-Cells destory foregin cell or pathogen

Humoral Immunity

1. Foregin antigen activates a specific B-Cell

2. B-Cells recognise that it fits the antigens of the pathogen through a lock & key method. B-Cells create plasma cells to fight off invader.

3. Through multiple exposure, memory cells will rapidly call for plasma cells to kill the pathogen

Autoimmune Disease

When your body fails to recognise self and non-self, so will start attacking you (e.g. lupis)

Epideiology

The study of disease in frequency (# of people) and distribution (location of spread)

Spread of Diseased is Influenced By:

Length of time in host (Persistance) → 1 day, 1 week, 1 month etc

Transmission mechanism → how it is transmitted

Proportion of population who are immune/immunised

Mobility of individual → can you leave the house or are you confined?

Mechanisms of Disease Transmission

• How the pathogen moves from host to host

→ Droplet transmission

→ Airborne transmission

→ Contaminated objects

Persistence of a Disease

Length of time a pathogen can survive in a host

High persistence → survive for a long time

Low persistence → unable to survive for long

Immunisation

• The protection against the disease

→ High immunisation = low spread of disease

→ Low immunisation = high spread of disease

Individuals vulnerable to the disease rely on herd immunity for protection

Ro - Reproduction Number (R nort number)

• Number of secondary people who will get infected from the primary source

• Assumes everyone is vulnerbale → does not account for immunity or health preventions

Ro Values

Ro > 1 = infecting more than one person so the disease is increasing

Ro = 1 = transmission is stable

Ro < 1 = transmission is decreasing in that population

Ro Value is Influenced by:

• Length of infection in a host

• Probability of transmission (25% VS 75%)

• Contact with individuals (social distancing VS physical touch)

• Population density of area (close together or far apart)

• Virulence of disease (how spreadable it is)