response and regulation. o what does your nervous system do for you?

RESPONSE AND REGULATION

O What does your nervous system do for you?

The Nervous System

Learning OutcomesO know that sense organs are groups

of receptor cells, which respond to specific stimuli: O light, sound, touch, temperature,

chemicals, O Know that the sense organs relay

this information as electrical impulses along neurones to the central nervous system.

The Nervous SystemO The nervous system controls our

bodies and helps us respond to external stimuli.

O The nervous system works by sending electrical impulses along neurones (nerve cells).

Responding to external Stimuli

O Sense Organs contain receptor cells detect changes in the environment

O These changes are called Stimuli

O Make a list of receptor cells in the human body, and write down what they are sensitive to.

SensitivityO Receptor cells can be found in

O Eyes O sensitive to light

O Ears O sensitive to soundO respond to changes in position and enable us to

keep our balance.O Tongue and nose

O sensitive to chemicals, enable us to taste and smell.

O Skin O sensitive to touch, pressure, pain and

temperature

The Nervous SystemO The information from the sense

organs to the central nervous system along neurones

O There are two main parts to the nervous system:O Central nervous system

O brain and spinal cordO Peripheral Nervous System

O A network of neurones

Responding to changesReceptor

s in the body

detect a change inside or

outside of the body

Central nervous system

co-ordinates the body’s responses

effectors cause a

response by moving part of the

body or secreting a hormone

Learning OutcomesO investigate sensitivity and reaction

times.

How Sensitive is your skin?

O Your skin contains touch receptors scattered across its surface

O If the skin is touched between these “detection areas” the body will not detect it.

O Some areas of your skin have these touch receptors more closely packed than others.

O Sensitivity of your skin varies in different parts of your body.

Investigating Skin Sensitivity

O We can investigate how sensitive different areas of the skin are using an experiment designed to test how good the skin is at distinguishing between two separate contact points which are close together.O Sensitive areas will detect that they

have been touched twiceO Less sensitive areas will detect only

one touch.

Risk AssessmentO There is no significant risks

associated with this experiment.

Standard ProcedureO Working in PairsO One person will be the test subject,

the other will be the experimenter.O Bend the paper clip into the shape

shownO Set the points so that they are 10mm

apart.

O Ask the test subject to look awayO Touch the paper clip to the subject’s

fingertip 20 times –touching with either one or two points (randomly)

O The subject must say whether they were touched with one point or two points.

O On your table of results record how many times the subject was right/wrong.

Areas of Skin

O Repeat the test twice moreO Examples

O ElbowO Palm of handO Back of handO Inside of wrist

O Test all three areas again with the paperclip points at different distances apartO 8mmO 6mmO 4mm

Summary of ProcedureO Bend the paper clip O Set the points so that

they are 10mm apart.O Ask the test subject to

look awayO Touch the paper clip to

the subject’s fingertip 20 times –touching with either one or two points (randomly)

O The subject must say whether they were touched with one point or two points.

O Repeat the test twice moreO Examples

O ElbowO Palm of handO Back of handO Inside of wrist

O Test all three areas again with the paperclip points at different distances apartO 8mmO 6mmO 4mm

Extending the practicalO Hypothesis

O The skin of people aged over 60 is less sensitive than the skin of people under 20.

O Design an experiment to test this hypothesis, and explain how you would process and analyse your results in order to come to an accurate conclusion.

ReactionsO A chain of events occurs in order for

us to respond to a stimulus

O Stimuli = changes in surroundingsO Receptor = detect the changesO Central Nervous System coordinatesO Effector = is a muscle or a glandO Response = reaction to change

Example – ReactionO Example: sitting on a drawing pin

O Stimuli O ReceptorO Co-ordinationO EffectorO Response

O Information from the receptors pass along neurones to the brain, the brain then co-ordinates a response.

Investigating Reaction Time

O The time taken between the stimulus and the response is known as reaction time.

O HypothesisO Practice will reduce the reaction time

O The hypothesis must be built on scientific principlesO There must be evidence

Scientific principles to support hypothesis

Evidence against hypothesis

Evidence in support of hypothesis

O The time taken for a signal to travel along a nerve is fixed

O Every time you catch the ruler, the signals will travel along the same nerve

O So time taken will always be the same

O Catching a ruler does not involve a simple pathway

O You may be able to O anticipate the ruler dropO Develop greater powers

of concentrationO These skills can be

improved with practice

Scientific principles to support hypothesis

O Based on this evidence is the suggested hypothesis validO YES

O Although we don’t know for certain that it is true there is scientific evidence to back it up.

Equipment and Risk Assessment

O EquipmentO Metre ruler

O Risk AssessmentO There is no significant risk associated

with this practical

Investigating Reaction TimeStandard Procedure

O Mark a pencil line down the centre of the subject’s thumb nail on the right hand.

O Ask subject to sit sideways at a bench or table with their forearm resting flat on the benchO Their hand should be over the edge

O Hold a ruler vertically between the subject’s first finger and thumbO The zero should be opposite the line

on the thumbO The ruler should not be touching the

finger or thumbO The distance between finger and

thumb should be the same for every trial

O Ask the subject to watch the zero markO As soon as you release the ruler, the

subject must try to catch it between their finger and thumb

O On a results table record the distance on the ruler opposite the mark on the thumb.

O Repeat this four more times and calculate the average distance.

O Convert this average distance to a time using the graph provided

Testing your hypothesisO Using this method

O Design and carry out an experiment to test the hypothesis that practice improves reaction time in this exercise.

O Your reportO Describe your methods, results and

conclusionsO Evaluate your experimental design

Further investigations into reaction time

O Practice is just one factor that could influence reaction time

O Other factors that could affect reaction time includeO O O O O

Factors affecting reaction time

O AgeO HandednessO Hand useO GenderO PracticeO Involvement in sportO Length of fingersO Concentration

Prep: reaction timesO Produce a hypothesis for one factor

that affects reaction timeO Give some background information

which supports your hypothesis (scientific principles)

Reflex Action(extension notes)

O Some responses to stimuli are automatic and rapid these are called reflex actions.

O In a reflex action three types of neurone are involved sensory, relay and motor neurones. 

O In a reflex action:O Impulses from a receptor pass

along a sensory neurone to the central nervous system.

O At a junction (synapse) between a sensory neurone and a relay neurone in the CNS, a chemical is released which causes an impulse to be sent along a relay neurone.

O  A chemical is then released at the synapse between a relay neurone and a motor neurone in the CNS. This causes impulses to be sent along a motor neurone to the organ (effector), which brings about the response.

O Effector is either a muscle or a gland. A muscle responds by contracting, a gland by releasing chemical substances.

Reflex Arc

Reflex Arc

Learning OutcomesO explore experimentally the positive

response of plant shoots to light, phototropism, and plant roots to gravity, gravitropism.

O Know that phototropism is due to a plant hormone.

Investigating TropismsO The investigation work for this topic

will be completed in the summer term when there is more sunlight available.

Plant ResponsesO Plants make directional and non-

directional responses to external stimuli.O Nastic responses

O Non-directional responses to an external stimulus

O e.g. trees shedding leaves in response to day length

O Tropic responsesO Directional responses to an external stimulusO e.g. plant shoot bending towards the light

Tropic ResponsesO Examples

O Phototropism response to lightO Geotropism response to gravity

O Tropic responses can be towards a stimulus (positive) or away from a stimulus (negative).

Tropisms in a plantO Plant shoot

movementO Positive phototropismO Negative geotropism

O Plant rootsO Positive geotropism

Prep: PhototropismO Hypothesis

O if the intensity of light increases, the speed at which phototropism occurs will increase

O Give some background information which supports your hypothesis (scientific principles)

Plant HormonesO Tropic responses are controlled by a

hormone which promotes growth.

O The hormone diffuses from the tip to where it promotes growth.

PhototropismO Hormone diffuses to the dark side of

the shoot away from the light, promoting more growth on this side; the shoot bends towards the light.

Pupil ActivitiesO Prep Worksheet

O AuxinsO Plant growth regulators

Learning OutcomesO understand the reasons why animals

need to regulate the conditions inside their bodies to keep them relatively constant and protected from harmful effects.

Background to teachingO Humans depend on the maintenance of a

constant internal environment.O This is called homeostasis.O Humans can only survive if variables such

as body temperature, and the amount of water, urea and carbon dioxide in the blood are kept relatively constant.

O Reason – enzymes only work at specific temperatures and pHs, which can be affected by these variables.

O The brain controls those organs which are specialised to maintain a constant internal environment.

O These include:O Kidneys – control water and urea levels in

the bloodO Skin – control of temperatureO Lungs – control of carbon dioxide levels

O Control is usually by negative feedback, this is a mechanism which keeps variables within narrow defined limits.

HomeostasisO Homeostasis is the maintenance of a

constant internal environment within the body.

O The brain has overall control of our body processes, when blood flows through the brain it checks temperature and the concentration of chemicals.

The brain controls many conditions inside the body

HomeostasisO Body temperature is kept constant at

37oCO Blood sugar level is kept constant by

the liver and pancreasO Water level is controlled by the kidneyO pH is kept constant at 7.4

O the kidneys remove excess ionsO Carbon dioxide levels in the blood are

controlled by the brain (and lungs)

Negative FeedbackO All of these rely on negative

feedback if they are to be kept constant.

O To be kept constant any increase in a factor must be accompanied by a decrease.O Heat gain = heat lossO Water gain = water loss

Negative feedback example

O heating system in a houseO Thermometer = receptorO Heater = effector

O Negative feedback change in temperature feeds back to heater, causing it to act to negate that change

Negative Feedback controlHeating System

O Heater switches on and water heats up

O The thermometer detects the increase in temperature

O When it gets too high, a message is sent to the heater to switch it off.

O Heater switches off and temperature reduces

O The thermometer detects the decrease in temperature

O When it gets too low, a message is sent to the heater to switch it on.

Learning OutcomesO understand that hormones are chemical

messengers, carried by the blood, which control many body functions.

O Investigate data showing the relationship between glucose and insulin levels in the blood.

O Understand that glucose levels need to be kept within a constant range so when the blood glucose level rises, the pancreas releases the hormone insulin, a protein, into the blood. This causes the liver to reduce the glucose level by converting glucose to insoluble glycogen and then storing it.

Hormonal ControlO Hormones

O Chemical messengers that are released from glands into the blood where they are transported to their target organs

O Endocrine GlandsO Parts of the body that release (secrete)

hormonesO Target organ

O Organ that a specific hormone acts upon

DefinitionsO Pancreas

O Organ that monitors and controls blood glucose concentration

O Produces the hormones insulin and glucagonO Insulin

O Hormone that converts glucose into glycogen for storage in the liver and muscles cells

O DiabetesO Sufferers do not produce enough insulin in

their pancreas, which leads to dangerous blood glucose levels

Control of Blood Glucose(INSULIN ONLY)

Control of blood glucose

O Adrenaline raises blood glucose concentration in an emergency

O hormones produced in the pancreas control the level of blood glucoseO Insulin

O Removal of glucose from the bloodstreamO Increases the use of glucose in respirationO Conversion of glucose to glycogen in the

liver

Control of blood glucose

glucose glycogeninsulin

Negative feedback control of blood glucose

Normal blood glucose levels

Food intake

Glucose levels rise

Detected by pancreas

Pancreas secrete insulin

Glucose glycogenIn liver

Glucose levels fall

Learning OutcomesO understand the principles of

negative feedback mechanisms to maintain optimum conditions inside the body as illustrated by the control of glucose levels by insulin and glucagon

Control of Blood Glucose

(INSULIN AND GLUCAGON)

Control of blood glucose

O Adrenaline raises blood glucose concentration in an emergency

O two hormones produced in the pancreas work together to control the level of blood glucoseO Insulin

O Removal of glucose from the bloodstreamO Increases the use of glucose in respirationO Conversion of glucose to glycogen in the liver

O GlucagonO Stimulates liver cells to breakdown glycogen

into glucose

EXTENSION NOTES – Higher Tier Only

Control of blood glucose

glucose glycogen

insulin

glucagon

EXTENSION NOTES – Higher Tier Only

Negative feedback control of blood glucose

Normal blood glucose levels

Food intake

Glucose levels rise

Detected by pancreas

Pancreas secrete insulin Glucose glycogen

In liver

Glucose levels fall

Glycogen glucose

In liverDetected by pancreas

Pancreas secrete

glucagon

Glucose levels fall(exercise)

Glucose levels rise

EXTENSION NOTES – Higher Tier Only

Learning OutcomesO know that diabetes (type 1) is a

condition in which a person's blood glucose may rise to a fatally high level because the body does not produce enough insulin. Understand that it can be diagnosed by the presence of glucose in the urine and the methods of treating the condition.

Why control blood glucose levels?

O HypoglycaemiaO Blood glucose levels drop dangerously low

O HyperglycaemiaO Blood glucose levels get too high

O Both of these conditions can result inO disorientationO Loss of consciousnessO Fall into a comaO death

DiabetesO Insulin controlled diabetes (type I)

O The body is unable to produce insulinO Diabetics take insulin injections and control

glucose intake in their diet. O Blood glucose levels need to be tested

several times a day

O Adult-onset diabetes (type II)O The body produces insulin, but the liver

does not respondO Blood glucose levels are controlled by diet

alone

Symptoms of DiabetesO Sugar in urineO Patient produces a lot of urine

O The body is trying to flush out the glucose

O Patient gets thirstyO Due to the volume of water lost in the

urineO Patient feels tired

New deal for diabetics

design a leaflet to explain what’s involved in islet tissue

transplantation

Transplant data

Transplant data

Learning OutcomesO Carry out testing of artificial urine

samples for glucose using a suitable method, such as Benedicts.

Diagnosing DiabetesO Doctors diagnose diabetes by the

presence of sugar in the urineO Diastix

O Are testing sticks with a sample area at the bottom

O This area changes colour when dipped in urine

O This colour change can be used to measure how much sugar is in the urine

Testing Urine for Glucose

O Benedict’s solution is a test for reducing sugars.

O Benedict’s will change colour if sugar is presentO No glucose = blueO Glucose = green orange red

O this depends on how much glucose is present

Risk AssessmentO Wear eye protectionO Benedict’s solution is an irritantO Bunsen Burner and boiling water

O Beaker may crack

ApparatusO Benedict’s

solutionO 4 “urine”

samples labelled A-D

O 250cm3 measuring cylinder

O 250cm3 beaker (water bath)

O 4 boiling tubesO TripodO GuazeO Heating matO Bunsen burner

Learning OutcomesO recognise and label a simplified given

diagram of a vertical section through the skin to show: hair, erector muscle, sweat gland, sweat duct, sweat pore, blood vessels.

O Understand the role of these structures in temperature regulation: change in diameter of blood vessels, sweating, erection of hairs; shivering as a means of generating heat.

Learning OutcomesO understand the principles of

negative feedback mechanisms to maintain optimum conditions inside the body as illustrated by the control of body temperature.