Tolerance Limits
Give an example of a factor that organisms have a tolerance limit for.
Temperature, Water Availability, BGL, Carbon Dioxide Concentration
Define: Negative Feedback
A response that inhibits the original or initial stimulus, resulting in the control of a homeostatic variable (body condition).
Name the type of specialised cell that makes up the nervous system.
Neuron
Name the process by which a chemical message is transmitted between neurons.
Neurotransmission (or Synaptic Transmission)
Name the process used by organisms to regulate their BGL.
Glucoregulation
Draw and label the stimulus–response model, including the types of neurons involved.
See Board
Which of the following correctly compares the central nervous system (CNS) and peripheral nervous system (PNS)?
J. The CNS includes all nerves, while the PNS includes only the brain and spinal cord.
K. The CNS detects stimuli, while the PNS processes information.
L. The CNS includes the brain and spinal cord, while the PNS includes sensory and motor nerves.
M. The CNS and PNS perform exactly the same functions.
L. The CNS includes the brain and spinal cord, while the PNS includes sensory and motor nerves. ✅
Describe the function of the nervous system.
Sense and respond to changes in an animal's internal and external environment.
Define: Tolerance Limit
The maximum and minimum amount of a given factor a species or organism can tolerate before it becomes too hard to maintain life processes.
Describe what a sensory receptor is, and name a specific type of sensory receptor. (2 Marks)
Description: A specialised cell, or group of cells, that detect stimuli both inside and outside of the body. (1 Mark)
Specific Types: Chemoreceptor (Smell and Taste), Mechanoreceptor (Touch), Nociceptor (Pain), Thermoreceptor (Temperature), Photoreceptor (Light) (1 Mark)
A neuron that has its soma at the start of the axon and is unmyelinated is most likely to:
J. Rapidly transmit impulses to muscles and glands.
K. Connect sensory and motor neurons within the central nervous system.
L. Carry impulses from receptors to the spinal cord and brain.
M. Transmit impulses over long distances using a myelin sheath.
K. Connect sensory and motor neurons within the central nervous system. ✅
Which one of the following nerve pathways represents the reflex response to the stimulus of stepping on a sharp object?
J. Receptor → Motor Nerve → Spinal Cord → Sensory Nerve → Muscle in Foot
K. Receptor → Motor Nerve → Brain → Sensory Nerve → Muscle in Leg
L. Receptor → Sensory Nerve → Brain → Motor Nerve → Muscle in Foot
M. Receptor → Sensory Nerve → Spinal Cord → Motor Nerve → Muscle in Leg
M. Receptor → Sensory Nerve → Spinal Cord → Motor Nerve → Muscle in Leg
Describe a consequence that may occur if an organism's body temperature becomes dysregulated.
Below TL: The rate of enzyme-catalysed reactions are too slow. Or:
Above TL: Denaturation of enzymes, which decreases the rate of enzyme-catalysed reactions.
Draw a labelled stimulus–response model for a specific example, including the types of neurons involved.
Various
Describe the function of the dendrite in a neuron.
Receive nerve impulses from other neurons or receptors and transmit them towards the cell body (soma).
Caffeine is a drug that reduces the effect of the neurotransmitter adenosine. Adenosine is responsible for inducing sleep in a healthy person. Caffeine prevents adenosine from binding to receptors in the hypothalamus.
Caffeine
J. decreases the amount of time it takes for a healthy person to fall asleep.
K. binds to the active site of adenosine.
L. reduces the number of nerve impulses triggered by adenosine.
M. acts as an inhibitor that prevents the release of adenosine.
L. reduces the number of nerve impulses triggered by adenosine.
A person has been exposed to carbon dioxide levels above their tolerance limit. Which of the following is most likely to occur?
J. Hypocapnia and respiratory alkalosis, causing an increase in blood pH.
K. Hypercapnia and respiratory acidosis, causing a decrease in blood pH.
L. Blood glucose levels increase, causing dehydration.
M. Body temperature decreases, causing hypothermia.
K. Hypercapnia and respiratory acidosis, causing a decrease in blood pH. ✅
Hypothermia in humans occurs when the core body temperature drops below 35°C. As core body temperature decreases, the rate of enzyme-controlled metabolic reactions decreases, resulting in a further decrease in core body temperature.
Hypothermia
J. demonstrates negative feedback, because the response inhibits the initial stimulus.
K. demonstrates negative feedback, because the response does not inhibit the initial stimulus.
L. does not demonstrate negative feedback, because the response inhibits the initial stimulus.
M. does not demonstrate negative feedback, because the response does not inhibit the initial stimulus.
M. does not demonstrate negative feedback, because the response does not inhibit the initial stimulus.
A patient develops a neurological condition that selectively damages the axon terminals of motor neurons. Electrical impulses are still successfully transmitted along the axons, but the patient experiences muscle weakness and reduced movement. Which explanation best accounts for these symptoms?
J. The damaged axon terminals cannot convert chemical signals from the brain into electrical impulses, preventing the impulse from travelling along the neuron.
K. The damaged axon terminals cannot release neurotransmitters into the synapse, preventing the muscle cells from receiving the signal to contract.
L. The damaged axon terminals prevent the soma from maintaining the neuron's resting potential, stopping the formation of electrical impulses.
M. The damaged axon terminals reduce the myelin sheath around the axon, causing impulses to travel more slowly along the neuron.
K. The damaged axon terminals cannot release neurotransmitters into the synapse, preventing the muscle cells from receiving the signal to contract. ✅
Describe the role of neurotransmitters in the synapse. (4 Marks)
A nerve impulse stimulates the release (exocytosis) of the neurotransmitter into the synapse (1). Neurotransmitter molecules diffuse across the synapse (or synaptic cleft) (1) and bind to complementary receptors (1) in the membrane of the adjacent (or postsynaptic) neuron. This enables the nerve impulse (message) to be passed from one neuron to the next (1).