General
Define the term Emergent Properties
Emersion properties are properties that exist when the sum of all parts creates features that do not exist within individual components
Define a reflex arc without stating its pathway
Is a sequence of cells that participate in union to achieve the coordination of a reflex
What is the name of the 24-hour cycle that controls our sleep.
Circadian Rhythm
Which part of the brain is responsible for the control of ventilation.
Medulla
What is the name of the hormone which is responsible for cell division in plants.
Cytokinin
Mention the two components of the nervous system and the specific nervous system that controls digestive system regulation.
Central Nervous System, Peripheral Nervous System,
Enteric Nervous System
Define a pain reflex.
Involuntary response that protects the body from injury
Rapid, unconscious reaction to a harmful stimulus directly initiated by the spinal cord, bypassing the brain
What is the hormone that controls the sleep cycle, and which gland is it secreted by.
Hormone - Melatonin
Gland - Pineal Gland
What are the two voluntary actions in the digestive system and what is the involuntary action in the digestive system?
Voluntary - Swallowing, Egestion
Involuntary - Peristalsis
Define positive phototropism and the hormone responsible for it. (You are not required to mention the mechanism for how it works)
Hormone - Auxin
Positive phototropism: Growth towards the light source, observed in shoots.
Mention 3 differences between conscious and unconscious actions.
2) Unconscious is performed involuntarily, and we cannot control it through thought, while conscious is performed voluntarily and can be controlled by thought.
3) Unconscious is coordinated by the brain and spinal cord while conscious is controlled only by the brain.
What is the general pathway of a reflex arc
Receptor cells or direct nerve endings
Sensory neurone
Synapse
Relay neurone in CNS (decision making station)
Synapse
Motor neurone
Effector
Mention 3 effects of adrenaline in the body.
Increased heart rate and blood pressure
Increased dilation of air passages to increase air intake by lungs
Dilation of pupils
Increased blood sugar levels by increasing glycogen to glucose conversion
Increased blood supply to muscles
Increase muscle contractions to prepare for vigorous action during a fight or flight response
How does the pH change in the blood during rigorous exercise.
During rigorous exercise the carbon dioxide levels in the blood increase.
When carbon dioxide concentrations increase in blood, it leads to a decrease in pH
Carbon dioxide reacts with water to form carbonic acid, which dissociates into bicarbonate ions and hydrogen ions
The increase in hydrogen ions lowers the pH
Explain positive feedback in fruit ripening.
Ethylene is a gaseous plant hormone responsible for fruit ripening
Its IUPAC name is ethene
When a fruit begins to ripen, it releases ethylene, which stimulates more ethylene production in surrounding fruit
This is a positive feedback because the release of ethylene causes the production of more ethylene
This leads to a rapid and synchronised ripening of fruits
Describe the structure of a myelinated neuron, and explain why the action potential is faster in myelinated axons compared to unmyelinated axons.
Myelinated neurons have Schwann cells wrapped around their axons, forming an insulating layer.
Gaps between Schwann cells are called nodes of Ranvier.
In myelinated axons, action potentials jump between nodes, allowing faster signal transmission.
Unmyelinated axons do not have this insulation and transmit signals more slowly.
Explain the role of the cerebellum
The cerebellum does not initiate movement – this is done by the motor cortex in the cerebrum
It instead fine-tunes the timing of contractions, coordinating skeletal movement and helping us maintain posture and balance
It also helps with coordinating motor memory, such as riding a bike or typing, which are stored patterns of coordinated movement, termed “muscle memory”
Explain the function of the hypothalamus and explain how it controls water content in the body.
Hypothalamus connects the nervous system to the endocrine system
Regulates the release of hormones by sending signals to the pituitary gland
The pituitary gland releases hormones that are important for maintaining homeostasis of water balance, growth, metabolism, etc.
Anti-diuretic hormone (ADH)
Hypothalamus detects low water content in the body and signals the pituitary gland to secrete ADH
ADH travels to the kidneys and causes more water to be reabsorbed, reducing water content in the urine
Explain the process of the peristaltic reflex.
A bolus of food distends the wall of the alimentary canal.
This stretch is detected by sensory receptors in the ENS.
These receptors synapse with relay neurons, which in turn activate two motor neurons:
One releases excitatory neurotransmitters behind the bolus, causing muscle contraction to push food forward.
One releases inhibitory neurotransmitters ahead of the bolus, causing muscle relaxation to allow forward movement.
This coordinated contraction and relaxation is repeated along the length of the gut to ensure smooth movement of food.
Explain how exactly auxin promotes cell growth.
Auxin stimulates the production of hydrogen ion pumps in cell membranes
H⁺ ions are pumped into the apoplast (space between cell wall and membrane), acidifying it
This loosens the cross-links between cellulose molecules in the cell wall, making the cell wall more extensible
Turgor pressure pushes on the extensible cell wall, promoting cell elongation.
Mention 5 differences between Hormonal and Electrical signaling.
1) Type of signal
Hormonal - Chemical
Electrical - Electrical
2) Medium of transmission
Hormonal - In the bloodstream
Electrical - In neurons
3) Destination of the signal
Hormonal - Widespread (multiple parts of the body, but only target cells respond)
Electrical - Highly focused – on one neuron or group of cells
4) Effectors
Hormonal - Target cell in any tissue
Electrical - Muscles or glands
5) Type of response
Hormonal - Control of only involuntary actions
Electrical - Control of voluntary and involuntary actions
6) Speed of response
Hormonal - Slower
Electrical - Rapid
Outline the whole pain reflex arc.
Receptor - A free sensory nerve ending in a sensory neurone detects the stimulus of pain or heat directly
An action potential is generated in the sensory nerve and is transmitted through the long axon of the sensory neurone to the CNS
In the CNS, the axon forms a synapse with a single interneurone in the grey matter of the spinal cord
This interneurone synapses with a motor neurone, which sends the action potential out of the spinal cord directly to the effector - skeletal muscles
The action potential results in the contraction of the skeletal muscle, which immediately pulls the limb away
Signals are still sent to the brain to register pain and awareness, but the limb is pulled away before this signal reaches the brain due to the short nature of the reflex arc
Explain how the sleep cycle is controlled.
Melatonin secretion by the pineal gland follows a diurnal pattern where melatonin levels
Rise in the evening, promoting sleep at night
Fall in the morning, promoting wakefulness during the day
Melatonin production is inhibited by light and is controlled by the suprachiasmatic nucleus (SCN)
When light stimulates the retina, the SCN sends signals to the pineal gland to suppress melatonin release
In darkness, the SCN sends signals to the pineal gland to secrete melatonin
Explain the process of controlling blood pressure in the body.
High blood pressure:
When blood pressure increases, walls of arteries are stretched outwards
This stimulus is detected by the baroreceptors
Baroreceptor sends more impulses to medulla
Medulla sends signals to the SA node pacemaker in our heart to decrease the heart rate and stroke volume
This decreases the blood pressure to counter the high blood pressure
Low blood pressure:
When blood pressure increases, walls of arteries are no longer stretched outwards
This stimulus is detected by the baroreceptors
Baroreceptor sends lesser impulses to medulla
Medulla sends signals to the SA node pacemaker in our heart to increase the heart rate and stroke volume
This increases the blood pressure to counter the low blood pressure
Explain the role of auxin efflux carriers.
Auxin is produced at the tips of shoots, roots and growing buds and must diffuse into cells from this region
Auxin can enter plant cells by diffusion but requires auxin efflux carriers (membrane proteins) to exit the cell.
These carriers work through active transport
These carriers can be predominantly placed on one side of a series of cells
By doing this, auxins will be directed through only those series of cells
This directional transport allows for differential auxin distribution, crucial for processes like phototropism