1. National 5 Biology Unit 2 – Cell Biology
Section 8
Control and Communication

2. We will be learning…
Describe and identify the structures of the brain as the cerebrum, the cerebellum and the medulla and explain their main functions.
State that CNS is made up of the brain and the spinal cord.
Describe the function of the CNS as processing sensory information and bringing about appropriate responses.
Explain that reflexes are rapid responses to environmental changes and are protective in nature.
Describe the three types of neuron involved in a reflex arc.
Explain the role of sensory, inter and motor neurons in reflexes.
State that electrical impulses move along neurons.
State that the gaps between neurons are called synapses and that chemicals transfer messages between neurons.

3. Need for Co-ordination
All the body’s organs and systems need to be able to work together to allow the many functions that are essential to life.
The body needs to be co-ordinated

4. Need for co-ordination
Physical activity (exercise) is one of the body’s essential functions.
When a tennis player is about to hit the ball
Example
information is picked up about where the ball is using the sense organs (in this case the eyes).
This information is sent to the brain.
The brain sends out messages to the correct muscles to move the body in the correct way .
There are hundreds of muscles in the body, so this can be a very complex process.

5. The Nervous System The nervous system is composed of the brain,
spinal cord
nerves
The nervous system is composed of the brain,
the spinal cord and nerves.

6. The Nervous System
The spinal cord is protected by the spine.

7. The Nervous System
The brain sorts out information. The spinal cord sends information to and from the brain.
The brain and spinal cord make up the central nervous system (CNS).
Nerves carry information from the senses to the CNS.
Nerves carry information from the CNS to the muscles .
These make up the
peripheral nervous system [PNS]

8. The Nervous System
Information from the sensory nerves is sorted out by the CNS.
Information from the CNS is then carries by the motor nerves to the appropriate muscles which then contract.

9. The Brain Cerebrum Cerebellum Medulla Spinal Cord
This is the most complex organ in your body that controls the vital processes that keep you alive.
The brain is the ultimate multi-tasker e.g. you are listening, breathing and your heart is beating.
Cerebellum
Medulla
Spinal Cord

10. The Brain Cerebrum Cerebellum Medulla
Largest part of the brain. Divided into 2 halves (hemispheres – left and right). Each region is concerned with particular functions e.g. sensory area, motor area (movement), hearing, sight etc.
The cerebrum is highly developed in humans.
Cerebrum
Cerebellum
Controls balance and coordination.
Medulla
Controls the rate of breathing and heartbeat.

11. The Brain sensory area motor area
receives nerve impulses from the senses
motor area
transmits nerve impulses to muscles
sight
hearing

12. The Peripheral Nervous System (PNS)
This is a communication system made up of the brain, spinal cord and nerves.
There are three different types of nerves:
1. Sensory Neurons
2. Inter Neurons
3. Motor Neurons

13. Structure of a Neuron
The diagram below shows a typical neurone: in this case, a motor neurone. It has tiny branches at each end (the dendron) and a long fibre carries the signals (the axon).

14. The axon is surrounded by a fatty layer known as the myelin sheath
The axon is surrounded by a fatty layer known as the myelin sheath. This helps to protect the neurone and allow impulses to travel faster.
Synapses
Where two neurones meet, there is a tiny gap called a synapse. Signals cross this gap using chemicals released by a neurone. The chemical diffuses across the gap makes the next neurone transmit an electrical signal.

15. An electrical impulse travels along an axon.
This triggers the nerve-ending of a neuron to release chemical messengers called neurotransmitters.
These chemicals diffuse across the synapse (the gap) and bind with receptor molecules on the membrane of the next neuron.
4. The receptor molecules on the second neuron bind only to the specific chemicals released from the first neuron. This stimulates the second neuron to transmit the electrical impulse

16. Synapses Gaps between nerves are called synapses
Electrical impulses cannot pass
Neurotransmitters released from 1st nerve
Chemicals diffuse across synapse
Chemicals bind to receptors of next nerve
This triggers electrical impulse

17. Which type of nerve does what job?
1. Sensory nerve cells send a message to the spinal cord. A inter nerve connects the sensory nerve to the motor nerve in the spinal cord. A signal to make a muscle contract is sent down a motor nerve.

18. 2. Inter Neurons
A inter neurone is only found within the CNS. It connects the sensory and motor neurones.

19. 3. Motor Neuron
The motor neurone signal travels from the CNS to an effector such as a muscle or gland.
The response may be a rapid action from a muscle or a slower response from a gland

20. Reflex actions
A reflex action is a rapid, automatic response to a stimulus.
e.g. Imagine you accidentally touched a bunsen burner which was still hot from the previous class.
How would you respond ???
The stimulus is the heat from the bunsen (pain).
The response is that you pull your hand away very quickly. You don’t even have to think about it!!!

21. Reflex Actions
Reflex actions happen so quickly that there is often no time for the nerve impulses to reach the brain. Often the impulse only goes to the spinal cord and the brain becomes aware of the action only after it has happened.
See shared area for Diving reflex film

22. Reflex Actions Some examples are…
pulling a limb away (hand, arm, leg etc)
knee jerk reflex
eye blink reflex
So reflexes protect the body from damage.

23. Effector - Muscle or gland
Electrical impulses travel to the CNS via the sensory neurone.
The CNS processes information from our senses which needs a response
The information will pass to the relay neurone within the CNS.
Impulses pass to the motor neurone which will carry them to the muscle or gland where action will be taken.
CNS
Inter neurone
Motor neurone
Sensory neurone
Ruler reaction rate test stopclock reaction rate test
Effector - Muscle or gland
Receptor - Sense organ
Response
Stimulus

24. The Reflex Arc Skin receptor senses pain = signal sent STIMULUS
CNS
grey matter contains cell bodies
white matter contains nerve fibres
inter neurone
sensory neurone
motor neurone
Skin receptor senses pain = signal sent STIMULUS
muscles contract = movement RESPONSE

25. Discovery of Neurotransmitters
Vagus nerve slows down heart rate
Fluid passes from heart 1 container to heart 2 container
Vagus nerve stimulated in heart 1
Heart 2 slows down

26. National 5 Biology Unit 2 – Cell Biology
Section 8b
Hormonal Control

27. We will be learning… State the function of an endocrine gland.
State that hormones are chemical messengers.
State that target cells have receptors for that hormone on their surface
Explain that only cells that have the receptor for the hormone are affected by the hormone.
State that changes in blood glucose levels are detected by the pancreas.
Explain that when blood glucose levels increase, the pancreas produces more insulin which in turn activates an enzyme within its target cells (liver) that converts glucose into glycogen.

28. Hormonal Control
In addition to the control that the nervous system exerts on the body further control is brought about by hormones.
Hormones are chemical messengers secreted directly into the bloodstream by endocrine (ductless) glands.
Hormones stimulate specific target tissues.
The cells on the surface of a target tissue in contact with the bloodstream bear specific receptors for a particular hormone.

30. Target tissues have cells with receptors for hormones, so only some tissues are affected by specific hormones.
Examples of endocrine glands which release hormones include the pituitary gland (A.D.H.) and the pancreas (insulin and glucagon)
The target cell has specific receptors and the hormone fits the receptor on the target cell only

31. Endocrine System Endocrine System is made up of many glands.
These glands produce hormones - chemical messengers
Hormones travel in blood.
They are slow-acting.
Target tissue contains receptors for hormone
Hormones are specific.

32. Endocrine Glands and Secretions

33. What is Diabetes? Consequences
Diabetes is a condition caused by a communication pathway failure which;
Results in a fault in release of insulin or
Results in a failure to respond to insulin
Consequences
The main symptoms of undiagnosed diabetes can include:
passing urine more often than usual, especially at night
increased thirst
extreme tiredness
unexplained weight loss
slow healing of cuts and wounds
blurred vision

34. Type 1 diabetes
Type 1 diabetes usually develops early in life and is the most common type of diabetes in children. It occurs when the body is unable to produce any insulin.
Type 1 diabetes is treated with insulin injections, or by using an insulin pump.
About 15% of people with diabetes have Type 1

35. Type 2 diabetes
Type 2 diabetes is the most widespread form of the condition and usually develops later in life.
This develops when the body is unable to make enough insulin, or when the insulin that is produced does not work properly (known as insulin resistance).
Type 2 diabetes can be treated with diet and physical activity alone, or combining these with tablets which lower glucose levels in the blood.
Due to the progressive nature of the condition, insulin treatment may be required later in life.

36. Control of blood sugar levels
The sugar glucose is an important source of energy for the body.
Food is metabolised to release glucose, which is converted to CO2 and water during respiration and used to make ATP.
If there is too much glucose in the blood then it is converted to glycogen and stored in the liver until it is needed (it may also be stored as fat).
If the glucose levels are low then glycogen is converted back to glucose, which can then be used by the body.

37. Insulin for Diabetics
In the past, the source of Insulin for Diabetics was cattle and pigs
Cattle and pig Insulin is different in structure from Human Insulin and can therefore bring about allergic reactions
These allergic responses can have side effects such as eye damage and liver damage
With genetically engineered Insulin allergic responses are less likely to occur
Genetically engineered Insulin is produced by bacteria

38. What Insulin Does
We know from previous work that we need glucose to give us a continuous supply of energy
Cells are therefore constantly using up glucose present in our bloodstream (i.e. blood sugar)
Excess glucose in our bodies (following a meal) can be stored, in the liver, as a storage carbohydrate called glycogen
A rise in blood sugar is detected by cells in the Pancreas
Insulin is a hormone made by these cells in the Pancreas
Insulin is transported in the bloodstream to the Liver
Insulin changes glucose to glycogen in the liver –
as a result of this, the blood sugar concentration returns to normal

39. Glucagon (hormone)
When glucose is needed in the body again (when the blood sugar level drops) then the storage carbohydrate is converted back to glucose
Different cells in the Pancreas release a different hormone called Glucagon
Glucagon is transported in the bloodstream to the liver where it converts glycogen to glucose – blood sugar returns to normal again
Glucose is used for muscle contraction, nerve transmissions and making new cells etc.
Diabetics do not have enough Insulin so they don’t carry out the normal conversion of glucose to glycogen
The blood of Diabetics is so rich in glucose that it cannot be reabsorbed at the kidneys – it is excreted in the urine

40. Diabetes Mellitus
People with diabetes mellitus have the problem that some, or indeed all, of their insulin secreting cells are non-functional
Sufferers therefore produce insufficient (or no) insulin
From our previous study of the kidney nephron we learned that glucose is reabsorbed from the glomerular filtrate
The glomerular filtrate of a diabetic is so rich in glucose that much of it cannot be reabsorbed – it is excreted in the urine
In the absence of insulin, cells are unable to use glucose efficiently – fat stores become depleted, leading to loss in weight and wasting of tissues

41. Hormones Involved in Diabetes
The receptor cells that monitor the changes in blood sugar levels are found in the islets of Langerhans.
These are specialised cells in the pancreas that secrete two different hormones in response to changes in concentration of glucose in the blood:
Insulin
Glucagon

42. Insulin Insulin is secreted when the blood glucose level is high.
This hormone catalyses the conversion of glucose to glycogen in the liver.
As a result the blood glucose level falls.

43. Glucagon Glucagon is secreted when the blood glucose level is low.
This hormone catalyses the conversion of glycogen to glucose in the liver.
As a result the blood glucose level rises.

44. Soluble so easily released into the blood
insulin
Blood
Liver
glucose
glycogen
glucagon
Soluble so easily released into the blood
Insoluble so easily stored in liver cells

45. BOO!
Your heart starts beating really fast, you are very alert and you suddenly have loads of energy.
This is because of adrenaline, a hormone that the adrenal glands secrete to prepare the body for an emergency (e.g. an attack).
Adrenaline increases the body's rate of metabolism and influences the concentration of sugar in the blood.

46. Fight or Flight?
The secretion of adrenaline causes the conversion of glycogen to glucose to provide the body with enough energy to protect itself.
When the emergency is over, the adrenaline levels fall and the regulation of blood sugar levels is under homeostatic control again.

47. Control of glucose levels by Insulin and Glucagon
Insulin tells the liver to absorb MORE glucose and turn it into Glycogen
Glucagon tells the liver to breakdown LESS glycogen to glucose
Pancreas makes MORE INSULIN
and
LESS GLUCAGON
Glucose in the blood increases which pancreas detects
Eating
Less glucose in blood
Normal level of glucose in the blood
Normal level of glucose in the blood
No change
More glucose in blood
Exercise
Insulin tells the liver to absorb LESS glucose
Glucagon tells the liver to breakdown MORE glycogen to glucose
Pancreas makes LESS INSULIN
and
MORE GLUCAGON
Glucose in the blood decreases which pancreas detects

48. Diabetes Mellitus
Some people are unable to make enough (or any) insulin to regulate their blood sugar levels.
This is a common disorder that is known as diabetes mellitus (or diabetes).

49. Symptoms of Diabetes
People who suffer from diabetes have high levels of glucose in their blood as they are unable to convert it to glycogen or fat due to a lack of insulin.
This excess sugar is excreted in the urine; other symptoms include rapid weight loss, dehydration and frequent urination.
Diabetes is very dangerous and can result in a sufferer falling into a coma and dying if it is left untreated.
Fortunately, diabetes can be treated effectively with daily insulin injections and a careful diet.

50. Urine analysis Find out which person has diabetes.
Glucose in urine is a common indicator of someone who has diabetes.
Benedict’s solution can be used to test for glucose. If the Benedict’s turns ORANGE when heated, glucose IS present.
Find out which person has diabetes.

51. Method
Using a syringe, measure 5cm3 of each sample into separate test tubes.
Place a few drops of Benedict’s solution into each test tube.
Place all test tubes into the water bath for 15 minutes
Observe results in a table in your jotter
Patient sample A B C
Glucose present

52. Glossary
CNS
Central Nervous System made up of the spinal cord and the brain
Cerebellum
Controls balance and coordination.
Cerebrum
Largest part of the brain. Divided into 2 halves (hemispheres – left and right). Each region is concerned with particular functions e.g. sensory area, motor area (movement), hearing, sight etc.
The cerebrum is highly developed in humans.
Medulla
Controls the rate of breathing and heartbeat.
PNS
Peripheral Nervous System
Hormone
chemical messengers secreted directly into the bloodstream by endocrine (ductless) glands.

53. Storage carbohydrate made up of glucose molecules.
Glossary
Glucagon
Hormone produced by the pancreas which is transported to the liver to activate the reaction to break down glycogen into glucose
Insulin
Produced by cells in the pancreas as a response to high levels of glucose. It is transported to the liver where it activates the reaction of glucose to glycogen.
Glycogen
Storage carbohydrate made up of glucose molecules.
Pancreas
Produces the hormones – glucagon (low glucose levels) and insulin (high glucose levels) into the blood.
Liver
Contains receptors and enzymes that can break up glycogen into glucose and vice versa when required.

54. Glossary A reflex arc is a rapid, automatic response to a stimulus
Synapse
Gaps between nerves. Signals cross this gap using chemicals released by a neurone. The chemical diffuses across the gap makes the next neurone transmit an electrical signal.
Neurotransmitter
Chemical messengers that diffuse across the synapse (the gap) and bind with receptor molecules on the membrane of the next neuron.
Endocrine System
A system made up of many glands that secrete hormones (chemical messengers)
Reflex Arc
A reflex arc is a rapid, automatic response to a stimulus
Neuron
Neurones are nerve cells. They carry information as tiny electrical signals. There are three different types of neurones, each with a slightly different function.