Nervous About Immunity (All Topics)

What is the function of motor neurons?

Carry nerve impulses from the CNS to muscles or glands (effectors).

Describe the structure of a motor neuron.

• Dendrites: Receive impulses

• Cell body: Contains nucleus

• Axon: Transmits impulse

• Myelin sheath: Insulates axon, speeds transmission

• Axon terminals: Pass impulse to effector

What is an example of a motor neuron function in a reflex?

• In a withdrawal reflex, the motor neuron tells arm muscles to contract and pull away from a hot surface.

What is the role of a motor neuron in a reflex arc?

Receives signals from the interneuron and sends the impulse to the effector for immediate action.

What happens to red litmus in base?

Turns blue.

What happens to blue litmus in acid?

Turns red.

What is the pH range of acids?

0-7.

What is the pH range of alkaline?

7–14.

What is the product of a neutralisation reaction?

Salt and water.

What does a pH indicator show?

Whether a solution is acidic, neutral, or basic.

What is the first line of defence?

Physical and chemical barriers that prevent pathogens from entering the body.

Is the first line of defence specific or non-specific?

Non-specific – it defends against all pathogens equally.

What are the main physical barriers in the first line of defence?

• Skin: Impermeable barrier to pathogens.

• Mucous membranes: Trap pathogens in the nose, throat, and lungs.

• Cilia: Tiny hairs that move mucus and trapped particles out of the respiratory tract.

What are the chemical components of the first line of defence?

• Stomach acid: Destroys ingested pathogens.

• Enzymes in saliva and tears (e.g., lysozyme): Break down bacterial cell walls.

• Sweat and sebum (skin oils): Slightly acidic, inhibits bacterial growth.

What activates the second line of defence?

Pathogens that get past the first line of defence and enter the body.

Is the second line of defence specific?

No – it targets all invaders the same way.

What are the key components of the second line of defence?

• Phagocytes: White blood cells (like macrophages) that engulf and digest pathogens.

• Inflammation: Increased blood flow brings immune cells to infected areas, causing redness, heat, swelling, and pain.

• Fever: Raises body temperature to slow pathogen reproduction.

• Complement proteins: Help mark pathogens and destroy their membranes.

What is phagocytosis?

The process by which phagocytes engulf and break down pathogens.

Is the third line of defence specific?

Yes – it targets specific pathogens based on their antigens.

What are antigens?

Molecules on the surface of pathogens that trigger an immune response.

What are B cells and what do they do?

• B cells are white blood cells that produce antibodies specific to antigens.

• Some become plasma cells (make antibodies), others become memory B cells.

What is the function of antibodies?

Bind to pathogens, marking them for destruction or neutralising them directly.

What do T cells do?

• Helper T cells: Activate B cells and other immune cells.

• Cytotoxic T cells: Kill infected cells directly.

What is immunological memory?

After an infection, memory cells remain and respond faster to future infections by the same pathogen.

What is an infectious disease?

Caused by pathogens and can spread between people.

Give 3 examples of infectious diseases.

Flu (virus), TB (bacteria), malaria (protist).

What is a non-infectious disease?

Not caused by pathogens; not spreadable.

Give 3 examples of non-infectious diseases.

Diabetes (lifestyle), cystic fibrosis (genetic), skin cancer (environmental).

How do infectious and non-infectious diseases differ?

Cause, spread, treatment approach.

What is an epidemic?

 A disease outbreak in a specific region.

What is a pandemic?

A global disease outbreak.

What is an endemic?

 A disease constantly present in a population.

What does insulin do?

Lowers blood glucose by promoting uptake into cells.

What does glucagon do?

 Raises blood glucose by triggering glycogen breakdown.

What controls blood glucose?

Pancreas, via negative feedback.

What is homeostasis?

Maintaining a stable internal environment (e.g., temperature, glucose).

Which systems help maintain homeostasis?

Nervous and endocrine systems.

 What is a hormone?

A chemical messenger secreted by glands into the blood that affects target organs.

Which gland controls growth and other glands?

Pituitary gland.

What hormone does the thyroid release and what is its function?

Thyroxine; regulates metabolism.

What hormone does the adrenal gland release and what does it do?

Adrenaline; prepares body for fight or flight.

Which hormones does the pancreas release?

Insulin and glucagon.

What do the ovaries and testes produce?

Oestrogen and testosterone.

What is the function of the cerebrum?

Voluntary movement, thinking, memory, senses.

What is the function of the cerebellum?

Coordination and balance.

 What does the brainstem control?

Involuntary functions like heartbeat and breathing.

What does the hypothalamus do?

Controls homeostasis and hormone release.

What is the function of the corpus callosum?

Connects the left and right brain hemispheres.

What are the 3 types of neurons and their functions?

• Sensory: Carries signals from receptors to CNS

• Interneuron: Connects neurons within CNS

• Motor: Sends signals from CNS to effectors

What is a reflex arc?

A fast, involuntary neural pathway that bypasses the brain to produce a response.

List the components of a reflex arc in order.

Receptor → Sensory neuron → Interneuron → Motor neuron → Effector

What is the function of reflexes?

To produce quick, automatic responses to triggers.