Control and coordination in mammals

Myofibrils in striated muscle are made up of contractile units known as sarcomeres. When an impulse causes striated muscles to contract, calcium ions are discharged from the sarcoplasmic reticulum.

Feb/March 2016

Most reflex arcs pass through the spinal cord and include more than one type of neurone. Name and state the functions of the three neurone types in a spinal reflex arc.

Feb/March 2017

Motor neurones are cells in the nervous system.

Feb/March 2018

Section B. Answer just one question.

Feb/March 2019

Dogs possess an exceptionally acute sense of smell. They are able to detect molecules in the air at a concentration of one part per trillion ($10^{12}$).

Feb/March 2021

Fig. 7.1 shows a synapse linking a chemoreceptor cell from a human taste bud with a dendrite of a sensory neurone. In an experiment, the microvilli of the chemoreceptor cell were exposed to different concentrations of sodium chloride solution. For each concentration, the membrane potential of the chemoreceptor cell and that of the sensory neurone dendrite were measured. The resting potential of this chemoreceptor cell is $-50\,\text{mV}$ and the resting potential of the dendrite of this sensory neurone is $-70\,\text{mV}$. The results are given in Table 7.1, with sodium chloride concentrations in $\text{g dm}^{-3}$ and membrane potentials in $\text{mV}$.

Feb/March 2023

Fig. 9.1 shows a relaxed sarcomere in striated muscle.

Feb/March 2023

Striated muscle is made up of myofibrils. The myofibrils contain several structural proteins, including troponin, tropomyosin, actin and myosin.

Feb/March 2024

Describe the arrangement of a myelinated sensory neurone.

May/June 2010

Follicle stimulating hormone (FSH) and luteinising hormone (LH) each have two polypeptide chains, the $\alpha$ and $\beta$ chains. • The $\alpha$ chains in FSH and LH are identical. • FSH has a $\beta$ chain of 111 amino acids, whereas LH has a $\beta$ chain of 121 amino acids. • FSH and LH attach to different receptors in the cell surface membranes of their target cells. • This attachment causes steroid synthesis in the target cells.

May/June 2010

Describe the structure of a myelinated sensory neurone.

May/June 2010

Follicle stimulating hormone (FSH) and luteinising hormone (LH) are each made of two polypeptide chains, the $\alpha$ and $\beta$ chains. The $\alpha$ chains in FSH and LH are the same. The $\beta$ chain in FSH contains 111 amino acids, whereas the LH $\beta$ chain contains 121 amino acids. FSH and LH attach to different receptors in the cell surface membranes of their target cells. This attachment causes steroid synthesis by the target cells.

May/June 2010

Fig. 3.1 is a drawing of a section through an ovarian follicle. State the names of the parts labelled A-D in Fig. 3.1.

May/June 2011

In girls, the first menstrual cycle starts at the beginning of puberty.

May/June 2012

Outline the biological mechanism behind the effect of the contraceptive pill.

May/June 2012

In girls, the first menstrual cycle begins at the onset of puberty.

May/June 2012

Fig. 6.1 shows the way a cholinergic synapse operates.

May/June 2013

Fig. 5.1 illustrates several of the stages involved in in-vitro fertilisation (IVF).

May/June 2013

Fig. 6.1 shows how a cholinergic synapse operates.

May/June 2013

The passage below explains how sensory receptors function.

May/June 2014

FSH (follicle stimulating hormone) has key functions in mammalian reproduction.

May/June 2014

The passage below explains how sensory receptors function. Complete it by inserting the most suitable scientific term(s). A sensory receptor cell reacts to a stimulus by opening ion __________ in its cell surface membrane. Sodium ions move into the cell causing the membrane to become __________. This is called the __________ potential. If this potential is large enough to reach a __________ then an action potential is transmitted to the central nervous system. As stimulus strength increases, the __________ of action potentials transmitted increases.

May/June 2014

The Indian cobra (Naja naja) is a venomous snake species native to South Asia. Fig. 6.1 depicts an Indian cobra.

May/June 2015

Fig. 5.1 shows a neurone type located in the brain, known as a pyramidal cell.

May/June 2015

The Indian cobra ($Naja\,naja$) is a venomous snake species found across South Asia. Fig. 6.1 displays an Indian cobra.

May/June 2015

Fig. 8.1 is a diagram showing a sensory neurone together with some receptor cells.

May/June 2016

Fig. 8.1 shows an electron micrograph of part of a cholinergic synapse.

May/June 2016

Fig. 8.1 shows a sensory neurone and several receptor cells.

May/June 2016

Describe the structure of a motor neurone.

May/June 2017

Describe how tropomyosin functions in the sliding filament model of muscle contraction.

May/June 2017

Section B. Attempt one question.

May/June 2017

Fig. 3.1 presents a diagram showing two sarcomeres in relaxed striated muscle.

May/June 2017

Section B. Answer any one question.

May/June 2017

Describe the role of tropomyosin in the sliding filament model of muscle contraction.

May/June 2017

Describe the main structure of a sensory neurone.

May/June 2018

In mammals, the nervous system and the endocrine system work together to coordinate responses to changes in the internal and external environments.

May/June 2018

Describe how the arrival of an action potential at a presynaptic neurone can lead to acetylcholine being released into the synaptic cleft.

May/June 2018

Describe the effect on the kidney of a high concentration of ADH in the blood.

May/June 2018

Fig. 1.1 shows an electron micrograph of a myelinated neurone in cross-section.

May/June 2019

Fig. 1.1 depicts a cholinergic synapse.

May/June 2019

In mammals, ACTH is secreted by the anterior pituitary gland. It causes cells of the adrenal glands to make the hormone cortisol. This is an instance of cell signalling. The principal stages of cell signalling involving ACTH are comparable with the main stages of cell signalling by adrenaline.

May/June 2020

Thyrotoxic myopathy (TM) is a neuromuscular disorder resulting from excessive production of the thyroid hormone thyroxine. A major symptom of TM is muscle fatigue. Fig. 6.1 shows the effects of excessive thyroxine production on striated muscle.

May/June 2020

Diabetes insipidus (DI) is a human disorder that makes a person very thirsty, so they drink more than usual. In one type of DI, a tumour develops in the part of the hypothalamus involved in osmoregulation.

May/June 2020

A nerve is made up of bundles of different kinds of neurone. Fig. 5.1 illustrates the mean speed at which impulses are transmitted by three sensory neurone types, C, $A^\delta$ and $A^\beta$. Information given: • Impulses from pain receptors in the skin travel along sensory neurones C and $A^\delta$. • Sensory neurones C and $A^\delta$ make synapses in the spinal cord with relay neurones called projection neurones. • Projection neurones carry impulses to the region of the brain that detects pain. • Impulses from touch receptors in the skin move along sensory neurones $A^\beta$, which may also make synapses with projection neurones in the spinal cord. • Sensory neurones $A^\delta$ and $A^\beta$ have myelin. • Sensory neurones C lack myelin.

May/June 2021

Fig. 1.1 shows part of a neurone membrane when it is at resting potential.

May/June 2021

GLP-1 (glucagon-like peptide-1) is a hormone made up of 31 amino acids. It is released by specialised intestinal epithelial cells called L cells. Fig. 6.1 shows how GLP-1 is secreted and how it acts on the pancreas, brain and stomach.

May/June 2021

Fig. 1.1 shows a diagram of part of a sarcomere in striated muscle.

May/June 2021

Describe how sodium ions function in selective reabsorption in the nephron and how calcium ions function in a cholinergic synapse.

May/June 2021

Motor neurones and sensory neurones carry out different jobs in nervous coordination. Contrast the structure and function of sensory neurones and motor neurones.

May/June 2022

In mammals, sensory receptor cells detect stimuli and then generate action potentials in sensory neurones. In human taste buds on the tongue, there are chemoreceptor cells. Different chemoreceptor cells respond to different chemical stimuli. Fig. 8.1 shows chemoreceptor cells within a taste bud.

May/June 2022

In mammals, sensory receptor cells detect stimuli and produce action potentials in sensory neurones. On the human tongue, taste buds contain chemoreceptor cells. Different chemoreceptor cells are sensitive to different chemical stimuli. Fig. 6.1 shows a diagram of chemoreceptor cells in a taste bud.

May/June 2022

Fig. 9.1 presents a cross-section of a myelinated neurone.

May/June 2022

Sarcomeres are the functional units within the myofibrils of the muscle fibres (muscle cells) in striated muscle. When an action potential reaches the sarcoplasmic reticulum of a striated muscle fibre, a sarcomere may shorten. This happens by the sliding filament model. Outline the sequence of events after stimulation of the sarcoplasmic reticulum that leads to shortening of a sarcomere.

May/June 2023

Dopamine is a neurotransmitter that is released at certain synapses in the brain. Its release and action are comparable to those of acetylcholine. Fig. 9.1 shows a brain synapse in which dopamine acts as the neurotransmitter.

May/June 2023

Humans sense the sweet taste of sucrose sugar through chemoreceptor cells in taste buds on the tongue. In the red admiral butterfly, Vanessa atalanta, sucrose is detected by chemoreceptor cells found on the antennae and on the tarsi (feet). The way the chemoreceptors in V. atalanta work is like the system in humans. Fig. 10.1 shows where the chemoreceptor cells are located on V. atalanta.

May/June 2024

Coordination in humans depends on two main systems: the nervous system and the endocrine system. Paracrine cell signalling is a third means by which coordination happens. In paracrine signalling, one cell releases a chemical that diffuses only a short distance to act on cells that are very close to the secreting cell.

May/June 2024

Fig. 8.1 shows a diagram of a sensory neurone.

May/June 2024

Fig. 10.1 presents a section of a neurone membrane while the resting potential is being kept.

May/June 2024

As an action potential develops, the potential difference across a neurone membrane alters. Table 10.1 gives the potential difference across the neurone membrane at three successive time points X, Y and Z, immediately before and during an action potential.

May/June 2025

An axon membrane is described as being at its resting potential when no action potential is occurring. Describe and explain how a resting potential in an axon membrane is maintained.

May/June 2025

Most carnivorous mammals need to move in order to hunt their prey. Outline why a carnivorous mammal relies more on its nervous system than on its endocrine system when it hunts.

May/June 2025

Fig. 8.1 shows a transmission electron micrograph of striated muscle. On Fig. 8.1: • use the letter P with a label line to indicate a region containing only actin • use the letter Q with a label line to indicate a region containing only myosin • use the letter R with a label line to indicate a region containing both actin and myosin.

May/June 2025

A newer development in fertility treatment is called in-vitro maturation (IVM). This costs less and is safer than the standard method used in in-vitro fertilisation (IVF), particularly for women with polycystic ovaries. Hormone treatment can be hazardous for women with this condition, in which several ovarian follicles mature at the same time. IVF and IVM are compared in Fig. 3.1.

Oct/Nov 2010

Describe how a resting potential is kept in an axon.

Oct/Nov 2011

Outline how gametogenesis differs in a man compared with a woman.

Oct/Nov 2011

Describe the way a resting potential is kept in an axon.

Oct/Nov 2011

Outline how gametogenesis differs between a man and a woman.

Oct/Nov 2011

If a body part is damaged or injured, action potentials are carried to the regions of the brain that detect pain. Explain how the arrangement of a sensory neurone can allow the action potentials to reach the brain very quickly.

Oct/Nov 2011

Nerve impulses must cross synapses. Table 1.1 lists the events that allow a nerve impulse to pass across a cholinergic synapse. The events are not arranged in the correct sequence.

Oct/Nov 2012

Nerve impulses must cross synapses. Table 1.1 sets out the steps that allow a nerve impulse to pass across a cholinergic synapse. The steps are not in the correct sequence.

Oct/Nov 2012

Fig. 1.1 depicts a neurone making three synapses with nearby neurones.

Oct/Nov 2012

Blood was collected each day for 44 days from a 29 year old woman. The concentrations of oestrogen, progesterone and luteinising hormone (LH) in the sample were determined. The results are shown in Fig. 4.1.

Oct/Nov 2013

Table 6.1 gives the average axon diameter and the average speed of conduction of impulses for four different animals.

Oct/Nov 2013

Many women use knowledge of their menstrual cycle as a family-planning method by avoiding sexual intercourse during the part of the cycle when fertilisation can happen. This part is called the fertile window. In women with regular, $28$-day menstrual cycles, ovulation is likely to occur on day $14$. Most guidelines say that the fertile window extends from day $10$ to day $17$ of the menstrual cycle.

Oct/Nov 2013

Fig. 6.1 is a trace showing how a neurone’s membrane potential changes during an action potential.

Oct/Nov 2013

Section B. Respond to one question.

Oct/Nov 2014

Neurones pass impulses from one region of a mammal’s body to another region. The table shows statements about motor neurones and sensory neurones.

Oct/Nov 2014

Neurones carry impulses from one region of a mammal’s body to another. The table lists statements about motor neurones and sensory neurones.

Oct/Nov 2014

Asparagus, Asparagus officinalis, is a green vegetable plant cultivated in many regions of the world. Fig. 6.1 shows some asparagus shoots.

Oct/Nov 2014

Scorpions are predatory arthropods. They possess a pair of grasping claws at the front of the body and a tail ending in a stinger. The stinger injects venom into prey to bring about paralysis.

Oct/Nov 2015

Outline how the oestrogen/progesterone contraceptive pill prevents pregnancy.

Oct/Nov 2015

Scorpions are carnivorous arthropods. At the front of their bodies they possess a pair of pincers, and their tail ends in a stinger. They use the stinger to inject venom into prey, causing paralysis. Fig. 6.1 shows a scorpion.

Oct/Nov 2015

Section B. Choose one question to answer.

Oct/Nov 2015

Section B. Answer only one question.

Oct/Nov 2015

Fig. 6.1 shows how the concentrations of four hormones in a woman’s blood vary across one menstrual cycle.

Oct/Nov 2016

Fig. 7.1 illustrates a neuromuscular junction in a mammal.

Oct/Nov 2016

Using examples, outline why homeostasis is important in a mammal.

Oct/Nov 2016

Fig. 6.1 illustrates how the concentrations of four hormones change in a woman’s blood over one menstrual cycle.

Oct/Nov 2016

Fig. 7.1 depicts a neuromuscular junction in a mammal.

Oct/Nov 2016

Fig. 6.1 illustrates the concentrations of two hormones, oestrogen and progesterone, in a woman’s blood over one menstrual cycle.

Oct/Nov 2016

Fig. 7.1 shows an electron micrograph of part of striated muscle.

Oct/Nov 2016

Explain the importance of the myelin sheath in action potential transmission.

Oct/Nov 2017

Cloves are the fragrant flower buds produced by the tree Syzygium aromaticum. Eugenol is a drug obtained from cloves. Eugenol alters the passage of sodium ions across the cell surface membranes of sensory neurones.

Oct/Nov 2017

Explain why the myelin sheath is important in the transmission of action potentials.

Oct/Nov 2017

Outline the functions of sensory receptor cells in the mammalian nervous system.

Oct/Nov 2018

Describe how a spinal reflex arc works and explain why it benefits a mammal.

Oct/Nov 2018

Fig. 4.1 presents a transmission electron micrograph of a cross-section through striated muscle.

Oct/Nov 2018

Outline the functions of sensory receptor cells in the mammalian nervous system.

Oct/Nov 2018

Therapeutic proteins help to treat disease. Human growth hormone (hGH) is one example of a therapeutic protein. In childhood, hGH has key roles in growth, and in adulthood it helps regulate metabolism.

Oct/Nov 2019

Identify the exact location in a cholinergic synapse that each statement refers to: • a region with many mitochondria; • a region where ACh is released by exocytosis; • a region containing voltage-gated channel proteins; • a region containing ligand-gated channel proteins.

Oct/Nov 2020