Practise mammalian control and coordination by tracing sensory signals and synapses, then following neuromuscular activation into sarcomere contraction.
The passage outlines the endocrine system.
Complete the passage by using the most appropriate scientific terms.
The endocrine system consists of tissues and __________,
which secrete hormones such as insulin, glucagon and antidiuretic hormone (ADH). Glucagon only affects target cells that have complementary receptors, which are located on the __________. Glucagon binds to these receptors and this leads to the production of a __________, which transfers the signal throughout the cytoplasm. The target cells for insulin are in the liver, __________ and adipose tissue. The target cells for ADH are those of the distal convoluted tubule and the __________ of the kidney nephron. These hormones are involved in __________, which is the maintenance of a constant internal environment.
Outline the differences between the endocrine system and the nervous system.
Fig. 8.1 is a diagram of a sensory neurone.
Fig. 8.1
Name the type of cell represented by cell A.
Name a type of cell that forms a synapse with structure B.
Name the cells that form the myelin sheath.
State and explain the differences in the transmission of impulses between myelinated and unmyelinated neurones.
Opioids are therapeutic drugs that are used to relieve pain. Morphine is an example of an opioid. It affects the functioning of synapses.
Fig. 8.2 is a diagram of a cholinergic synapse.
Fig. 8.2
With reference to Fig. 8.2, describe the differences between ion channel A and ion channel B.
Morphine binds to the opioid receptor in the presynaptic membrane. This stops the ion channel A from opening.
Suggest and describe the effects of the binding of morphine to this opioid receptor on the functioning of the cholinergic synapse.
Morphine also binds to the opioid receptor in the postsynaptic membrane. This results in the opening of ion channel C, allowing potassium ions to diffuse out of the cell.
Suggest how this would affect the synapse.
Fig. 8.1 is a diagram of a sensory neurone.
Fig. 8.1
Name a type of cell that forms a synapse with structure B.
The role of sensory receptor cells in mammals is to detect stimuli and generate action potentials in sensory neurones.
Human taste buds on the tongue contain chemoreceptor cells. Different chemoreceptor cells respond to different chemical stimuli.
Fig. 6.1 is a diagram of chemoreceptor cells in a taste bud.
Name the structures in the region Y and describe their function in a chemoreceptor cell.
Humans detect the sweet taste of sucrose sugar using chemoreceptor cells in taste buds on the tongue. The red admiral butterfly, Vanessa atalanta, detects sucrose using chemoreceptor cells located on its antennae and on its tarsi (feet). The mode of action of the chemoreceptors in V. atalanta is similar to that in humans.
Fig. 10.1 shows the locations of the chemoreceptor cells on V. atalanta.
Fig. 10.1
Describe how the presence of sucrose causes an action potential in the sensory neurone associated with a chemoreceptor cell in V. atalanta.
In some brain synapses, the neurotransmitter gamma-aminobutyric acid (GABA) is released. This results in an influx of chloride ions into the postsynaptic neurone.
Suggest and explain whether an action potential would be generated in the postsynaptic neurone if GABA is released into a brain synapse.
Fig. 10.1 is a graph of an action potential in a mammalian neurone.
Fig. 10.1
With reference to Fig. 10.1 suggest why:
- no further action potential can occur during A and B
- it is difficult for a further action potential to occur during C.
The plant Strychnos toxifera produces the toxin curare, which can cause muscle paralysis in mammals.
The toxin acts by binding to receptors on the cell surface membranes (sarcolemma) of muscle cells at neuromuscular junctions.
Suggest how binding of curare to receptors may cause muscle paralysis.
Suggest why the action of curare may lead to the death of a mammal.
Fig. 9.1 is a diagram of a relaxed sarcomere in striated muscle.
Fig. 9.1
On Fig. 9.1, use label lines and letters to label:
- an actin filament with the letter P
- a myosin filament with the letter R.
Striated muscle is composed of myofibrils. Myofibrils contain several structural proteins including troponin, tropomyosin, actin and myosin.
Outline the roles of these four structural proteins in the contraction of a sarcomere.
(b) Drugs that cause muscle paralysis (paralytic drugs) are used during surgery to stop the patient moving. One commonly used paralytic drug is succinylcholine, which works by preventing contraction of muscles. Succinylcholine is able to prevent muscles contracting because it has a similar shape to acetylcholine.
Suggest how succinylcholine is able to prevent muscles contracting.
(c) Duchenne muscular dystrophy (DMD) is a genetic disease that is caused by a single gene. DMD affects striated muscle, and symptoms of the disease first appear at an early age.
A fibrous protein, dystrophin, stabilises muscle fibres during contraction. A person with DMD produces non-functioning dystrophin or no dystrophin at all. The disease occurs in about four in 100000 people and mainly affects boys.
Suggest and explain why boys are more likely to have DMD than girls.