Human Bio - Unit 3 - Common Exam Q (MOCKS)

Compare and Contrast mode of action of steroid hormones and water soluble hormones (6 marks) (WATP 2019)

- steroid hormone passes through the cell membrane
- water soluble hormone binds to receptors on the cell membrane
- steroid hormone binds directly to DNA
- water soluble hormone has a secondary messenger
- effects of steroid hormon will be longer lasting
- effects of water soluble hormone will last for a much smaller amount of time

Describe the homeostatic mechanism that causes an increase in rate and depth of breathing in poorly ventilated environment such as a basement. In your answer, describe how the body detects and maintains gas concentrations in the blood (12 marks) (ER WATP 2019)

- Stimulus: high blood CO2 concentration/increased H+/decresed pH
- Receptor: Chemoreceptors
- in the carotid and aortic bodies as well as medulla oblangata
- Modulator: Medulla Oblangata
- Effector 1: Diaphragm and
- Effector 2: intercostal muscles
- Effector 3: Sympathetic Nervous System
- Response 1: increase rate and strength of diaphragm contraction
- Response 2: intercostal muscles contract to allow deep breathing
- Response 3: Increase sympathetic nerve impulses
- Feedback: negative feedback achieved since
- breathing rate and depth of breathing returned to normal/stimulus reversed

Describe how an unmyelinated nerve cell transmits an impulse (8 marks) (ER WATP 2019)

ANY 8 OF THE FOLLOWING:
- impulse passed at each point of the membrane/impulse does not jump between Nodes of Ranvier
- resting membrane potential is -70mV
- Stimulus is received and voltage gated sodium ion channels open, allowing Na+ to enter neuron
- if threshold of -55mV is reached:
- then Na+ ions flood into the neuron causing rapid depolarisation (action potential)
- sodium gates close and potassium gates open
- K+ flood out of the neuron causing depolarisation
- Hyperpolarisation occurs and potassium gates close
- The Na+/K+ pump, pumps three Na+ out and 2 K+ into the neuron
- this restores the original ion concentration and the resting membrane potential to -70mV

How do vaccinations provide immunity against disease? (6 marks) (ER WATP 2019)

- vaccines contain dead/attenuated/sub units/toxoids derived from the pathogen
- this vaccine will be recognised by B-lymphocytes
- B-lymphocytes will become sensitised, enlarge and divide into many clones
- Most B-lymphocytes become plasma cells and secrete antibodies
- some B-lymphocytes become memory cells
- Memory cells stay in the body and will flood the body with antibodies/react much faster if the person becomes infected with the pathogen which prevents illness