6.5 Nerves, hormones, and homeostasis

Question 1

Which systems are involved in homeostasis?

           Nervous                  Endocrine

A. No Yes

B. Yes No

C. No No

D. Yes Yes

Answer 1

D. Both the nervous and endocrine systems are involved in homeostasis

Question 2

Explain how blood glucose concentration is controlled in humans.

Answer 2

pancreatic cells monitor blood glucose;
insulin / glucagon is a hormone;
low glucose level induces production of glucagon;
α-cells of pancreatic islet produce glucagon;
glucagon stimulates the liver to break glycogen into glucose;
glucagon leads to increase in blood glucose;
absorption of glucose from digestive tract causes glucose levels to rise (after meals);
high level of blood glucose induces production of insulin;
-cells of pancreatic islet produce insulin;
insulin stimulates uptake of glucose into cells (muscles);
insulin stimulates uptake of glucose into liver / storage of glucose as glycogen in liver;
insulin leads to decrease in blood glucose;
homeostatic monitoring of blood glucose levels is constantly happening;
skipping meals can cause blood glucose levels to drop;
in diabetes mellitus blood insulin low / target cells insensitive;
blood glucose regulation is an example of negative feedback;
adrenaline leads to increased blood glucose levels;

Question 3

Under which conditions would insulin be secreted?
A. After a day of fasting
B. After a meal high in protein
C. After eating chocolate
D. When blood sugar is low

Answer 3

C. After eating chocolate

Question 4

What is at point X in the following negative feedback loop?

A. Venules
B. Capillaries
C. Arterioles
D. Sweat glands

Answer 4

C. Arterioles

Question 5

Which cells secrete insulin?
A. b-cells of the pancreas
B. Cells of the liver
C. a-cells of the pancreas
D. Epithelial cells of the intestine

Answer 5

A. b-cells of the pancreas

Question 6

Which of the following is closely associated with lowering of high body temperature?
A. Constriction of blood vessels in the skin
B. Vasodilation of blood vessels in the skin
C. Increased shivering
D. Decreased sweat production

Answer 6

B. Vasodilation of blood vessels in the skin

Question 7

Describe homeostasis in relation to blood glucose concentration in humans.

Answer 7

homeostasis is maintaining internal environment at constant levels/within narrow
limits;
homeostasis involves both nervous and endocrine systems;
low blood glucose triggers glucagon release;
glucagon is produced by α-islet cells in pancreas;
glycogen is converted to glucose;
high blood glucose concentration triggers insulin release;
insulin produced by β -islet cells in pancreas;
glucose taken up by (liver/muscle) cells;
glucose converted to glycogen;
blood glucose levels controlled by negative feedback;
correct reference to lowering or raising blood glucose levels;

Question 8

Arterioles in the skin contain muscle fibres which contract. What is the function of these fibres?
A. To move capillaries further from the skin when the body is too cold
B. To reduce blood flow to the skin when the body is too cold
C. To move capillaries closer to the skin when the body is too warm
D. To increase blood flow to the skin when the body is too warm

Answer 8

B. To reduce blood flow to the skin when the body is too cold

Question 9

Under what conditions is glucagon secretion increased?
A. After fasting for a long period
B. While resting
C. After a meal rich in carbohydrates
D. When the temperature falls

Answer 9

A. After fasting for a long period

Question 10

Which of the following changes occur with the onset of exercise?
A. Increase in pH of blood
B. Increase in rate of cellular respiration
C. Decrease in rate of contraction of the diaphragm
D. Decrease in carbon dioxide concentration of the blood

Answer 10

B. Increase in rate of cellular respiration

Question 11

The diagram below illustrates the main features of homeostasis.
What are P, Q, R and S?
P Q r s
A. Feedback Receptor/detector Controller/integrator Effector
B. Receptor/detector Controller/integrator Feedback Effector
C. Feedback Receptor/detector Effector Controller/integrator
D. Effector Receptor/detector Feedback Controller/integrator

Answer 11

A. Feedback Receptor/detector Controller/integrator Effector

Question 12

What are responsible for the lowering of blood glucose levels?
I. B-cells in the pancreas
II. Insulin molecules
III. a-cells in the pancreas
A. II only
B. I and II only
C II and III only
D I, II and III

Answer 12

B. Bicells in the pancreas and the Insulin molecules

Question 13

Describe the control of body temperature in humans.

Answer 13

temperature regulated by negative feedback;
thermoreceptors detect temperature change;
thermoregulatory centre (hypothalamus) in brain;
warming the body actions: [3 max]
shivering to produce waste heat;
no release of sweat;
behaviours including increased motion / huddling/reduction of exposed surfaces;
vasoconstriction of skin arterioles;
leading to retention of heat;
cooling the body actions: [3 max]
vasodilation of skin arterioles;
leading to loss of heat by radiation;
sweating accompanied by evaporative cooling;
reduction of activity / relaxation of muscles;
loss of heat by radiation;

Question 14

Where are the chemoreceptors that detect the changes in blood pH and levels of glucose found?

       Changes in blood pH            Changes in blood glucose

A. Brain stem Small intestine

B. Carotid vein Liver

C. Carotid artery Pancreas

D. Venae cavae Liver

Answer 14

C. carotid artery and pancreas

Question 15

What is the sequence of events when a nerve impulse reaches the synaptic knob of a neuromuscular
junction?
I. Synaptic vesicles release neurotransmitter
II. Ca²⁺ ions enter the synaptic knob
III. Neurotransmitter attaches to receptors on the muscular membrane (sarcolemma)
IV. Na⁺ions enter the muscular membrane
A. I, II, III, IV
B. II, I, III, IV
C. I, IV, II, III
D. IV, II, I, III

Answer 15

B

Question 16

Which process decreases when the human body temperature decreases?
A. Blood flow to the internal organs
B. Secretion of sweat
C. Secretion of insulin
D. Shivering

Answer 16

B. secretion of sweat

Question 17

Draw the structure of a motor neurone.

Answer 17

dendrites (leading to the cell body);
cell body;
nucleus (located in the cell body);
myelin sheath/Schwann cells;
axon;
nodes of Ranvier;
synaptic knobs;

Question 18

In thermoregulation, what would happen over a short period of time in each of these areas, if a person was placed in water at ? 15 C°
Peripheral circulation Sweat glands Liver Skeletal muscle

A. Increased blood flow Increased secretion Decreased temperature Decreased shivering

B. Decreased blood flow Decreased secretion Decreased temperature Increased shivering

C. Decreased blood flow Increased secretion No change in temperature Increased shivering

D. Decreased blood flow Decreased secretion No change in temperature Increased shivering

Answer 18

D

Question 19

What are the sequence of events at synaptic transmission?
I. Neurotransmitter released
II. Ca²⁺ enters synaptic knob
III. Neurotransmitter binds with receptor
IV. Action potential opens Ca²⁺ channels
A. I, II, III, IV
B. IV, II, I, III
C. I, III, IV, II
D. IV, II, III, I

Answer 19

B

Question 20

The diagram shows how the body regulates glucose levels in the blood.

What is Y?
A. Amylase
B. Insulin
C. Glucagon
D. Glycogen

Answer 20

C. glucagon

Question 21

Which structure is responsible for passing messages directly to effector organs?

Answer 21

D

Question 22

The movement of which ion initiates an action potential?
A. Calcium
B. Magnesium
C. Sodium
D. Potassium

Answer 22

C. Sodium

Question 23

In a nerve impulse, what happens at the site following the highest point of the action potential?
A. Voltage-gated sodium ion channels open and Na⁺ is pumped in.
B. Voltage-gated sodium ion channels open and Na⁺ diffuses out.
C. Voltage-gated potassium ion channels open and K⁺ is pumped out.
D. Voltage-gated potassium ion channels open and K⁺ diffuses out.

Answer 23

D. Voltage-gated potassium ion channels open and K⁺ diffuses out.

Question 24

When a motor neuron is at its resting potential, which of the following is correct for the concentration of Na+ and K+ ions?
Inside neuron Outside neuron
A. K+ high Na+ low
B. Na+ low K+ high
C. K+ high Na+ high
D. Na+ high K+low

Answer 24

C

Question 25

What substance enters the presynaptic neuron during synaptic transmission and what substance leaves it?
Substance entering presynaptic neuron Substance leaving presynaptic neuron
A. Neurotransmitter Calcium ions (Ca 2+)
B. Neurotransmitter Sodium ions (Na+)
C. Sodium ions (Na+) Neurotransmitter
D. Calcium ions (Ca 2+) Neurotransmitter

Answer 25

D

Question 26

Explain how the nerve impulse passes along a neuron.

Answer 26

in resting potential;
sodium is pumped out by active transport and potassium in;
a concentration gradient builds up electrical potential/voltage;
negative inside compared to outside;
when impulse passes / action potential;
must pass threshold level;
sodium channels open and ions diffuse into neuron;
membrane depolarized;
potassium diffuse out across membrane through ion channels;
active transport of ions once more;
slower in un-myelinated neuron than in myelinated;
an action potential in one part of the neuron causes the action potential to develop
in the next section;

Question 27

Outline the general organization of the nervous system.

Answer 27

formed of central nervous system;
brain and spinal cord;
peripheral nervous system divided into voluntary and autonomic nervous systems;
autonomic nervous system consists of sympathetic and parasympathetic nervous system;
voluntary nervous system has motor and sensory neurons;

Question 28

When an impulse arrives at a synapse which way do calcium ions move?
A. Into the synaptic knob from the synaptic cleft
B. Into the post synaptic nerve cell from the synaptic cleft
C. Out from the synaptic knob into the synaptic cleft
D. Out from the post synaptic nerve cell into the synaptic cleft

Answer 28

A. Into the synaptic knob from the synaptic cleft

Question 29

Membrane proteins are critical components of nerve function.
Which process in nerves does not require a membrane protein?
A. Diffusion of neurotransmitter
B. Active transport of sodium
C. Propagation of an action potential
D. Binding of neurotransmitter

Answer 29

A. Diffusion of neurotransmitter

Question 30

Describe the principles of synaptic transmission in the nervous system.

Answer 30

nerve impulse reaches pre-synaptic knob / membrane;
calcium ions/ 2 Ca + enter pre-synaptic neurone / knob;
vesicles with neurotransmitter / acetylcholine release contents;
neurotransmitter diffuses across synapse/synaptic cleft;
binds to receptors on post-synaptic neurone/membrane;
sodium ions/ Na+
enter post-synaptic neurone / sodium channels open;
depolarization / action potential /nerve impulse (in post synaptic neurone);
calcium ions/ 2 Ca + pumped back into synaptic cleft/synapse;
neurotransmitter broken down;

Question 31

Explain homeostasis giving two specific examples that show the role of the endocrine or
the nervous system.

Answer 31

homeostasis is the maintenance of a constant level of the internal environment ;
within narrow limits;
involves negative feedback;

name of variable controlled;;
method of detection / monitoring;;
response to high / low levels of variable;;
how variable is brought back to set point;;

Example 1 [3 max]:
blood glucose level;
pancreas cells /islets/beta and alpha cells to monitor level;
insulin secreted with high blood glucose / glucagon with low blood glucose levels;
named method of raising / lowering level of blood glucose;
Example 2 [3 max]:
body temperature;
hypothalamus monitors temperature;
nerve impulses to skin / muscle / liver;
named method of raising / lowering level of body temperature;

Question 32

Which process triggers the uptake of Ca2+ ions in synaptic transmission?
A. The influx of Na+ ions only
B. The release of the neurotransmitter
C. The depolarisation of the post-synaptic membrane
D. The arrival of the nerve impulse in the pre-synaptic neuron

Answer 32

D

Question 33

# Define the term homeostasis and list four variables under homeostatic control in humans
(excluding water balance).

Answer 33

maintains the internal environment at a constant level / between narrow limits;
blood pH;
carbon dioxide;
blood glucose;
body temperature;

Question 34

Which division describes the central nervous system?
A. Peripheral and central
B. Voluntary and involuntary nerves
C. Brain and spinal cord
D. Sensory and motor nerves

Answer 34

C. Brain and spinal cord

Question 35

Explain how ion movements cause a nerve impulse to pass along a neurone.

Answer 35

sodium ions enter the axon/neuron/nerve fibre;
by facilitated diffusion / through (voltage gated) channels;
depolarization / inside becomes positive / inside more positive than outside;
potassium ions leave the neuron;
repolarization / inside becomes negative / outside more positive than inside;
depolarization and repolarization is an action potential/nerve impulse;
action potential propagated / depolarization of next part of axon is triggered;
diffusion of sodium ions to next part of neuron/axon;
reference to local currents;
voltage gated channels open if threshold level is reached;
concentration gradients of Na+ and K+
re-established by active transport;
sodium potassium pump/sodium pumped out and potassium pumped in;

Question 36

After depolorization what happens to restore the resting potential?
A. Sodium channels open and sodium ions diffuse out of the neuron
B. Potassium channels open and potassium ions diffuse into the neuron
C. Potassium channels open and potassium ions diffuse out of the neuron
D. Sodium channels open and sodium ions diffuse into the neuron

Answer 36

C. Potassium channels open and potassium ions diffuse out of the neuron

Question 37

What changes would occur if a person moved from a cold swimming pool to a very warm changing room?
Transfer of heat in
blood to the skin
Temperature of
the skin
Rate of blood flow in
skin arterioles
A. Decreases Increases Increases
B. Increases Decreases Increases
C. Increases Increases Decreases
D. Increases Increases Increases

Answer 37

D

Question 38

Which ion is pumped into the axon of a neuron to help maintain the resting potential?
A. Calcium (Ca2+)
B. Hydrogen (H+)
C. Potassium (K+)
D. Sodium (Na+)

Answer 38

C. Potassium (K+)

Question 39

Explain the control of glucose levels in the blood.

Answer 39

glucose levels increase in blood after eating;
pancreas cells monitor glucose levels;
beta cells (of the islets) in the pancreas detect high glucose levels;
produce insulin;
causes cells to take up glucose (for energy use);
excess stored in liver/muscle as glycogen;
decreases glucose levels;
low glucose levels stimulate alpha (islet) cells in the pancreas;
produce glucagon;
stimulate the release of glucose from liver/breakdown of glycogen;
raises glucose levels;
normal levels of glucose maintained by homeostatic / negative feedback mechanisms;