coordination and control

8/6/2019 Coordination and Control

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Coordination and Control

Objectives:

1. State the main divisions of the nervous system2. distinguish between a neurone and a nerve3. define a reflex action4. explain the functions of motor and sensory neurons and spinal

snyapses

5. explain the process by which voluntary action occurs6. explain the response of sense organs to stimuli7. relate the internal structures of the eye to their functions8. explain how images are formed in the eye9. explain accommodation in the eye10.explain the causes of, and corrective measures of eye defects11.identify the sites of hormone production12.explain the roles of the various hormones in the human body13.distinguish between hormonal and nervous control systems14.define mental illness


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THE SENSES, NERVOUS SYSTEM, HORMOES AND CO-

ORDINATION

1. Sense Organs

Define Sense organs List the stimuli in which sense organs respond (light , sound, touch,

temperature and chemical changes)

2. The Eye

Structure and function Control of light entering the eye Formation of images Accommodation Common eye defects (long and short-sightedness, astigmatism)

3. The Nervous System

State the main divisions of the nervous system: Central NervousSystem (CNS) comprising brain and spinal chord and peripheral

nervous system (spinal nerve)

Distinguish between neuron and nerve Define a reflex action Structure of the spinal cord The spinal reflex action The knee jerk reflex

4. Hormones

Definition Endocrine and endocrine glands Location of the endocrine glands in the body Hormone produced by endocrine glands Function of each hormone Describe the control of blood sugar levels Describe the role of oestrogen progesterone in the menstrual cycle and

in pregnancy

distinguish between quick-acting hormones (insulin) and slow acting hormones (oestrogen) distinguish between the nervous control system


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Introduction

We are capable of observing and interacting with various stimuli which are

changes in the environment. I am sure that I am not the only one who puts

on a sweater when it gets really cold or squint my eye after moving from a

dimly lit room to the outside in the sun.

Our bodies are made up in such a way that we are able to detect the changes

that occur around us. These changes can be very obvious or subtle. For

example, our eyes pick up readily on the difference in the intensity of light

(squinting in sudden very bright light) and tiny organs in our skins called

receptors easily detect pressure intensity (the prick of a needle on the finger

as opposed to a soft cushion). This automatic response to changes in the

environment is called a reflex action

A reflex action may be described as a rapid automatic response to a

stimulus (change in the environment) by a muscle or a gland which doesnot require conscious control or a process of thinking. The stimuli

(change in theenvironment) may be good or bad for our bodies, which are

mainly determined by our brain which is a part of the central nervous

system. The Central Nervous System (CNS) causes our bodies to make

appropriate responses to changes in the environment. How our bodies

respond is for our own preservation and protection.

The processes that coordinate the bodys response to various

changes in the environment enable mans chances of survival.

Changes in the environment are detected by our bodiesOur bodies coordinate a response to a particular stimulus

(change in the environment)

The automatic response towards a stimulus is ultimatelyfor mans protection and survival.

With an understanding of this definition of a reflex action, can you see how

the following are examples of a reflex action?

I. CoughingII. Sneezing

III. Knee JerkBear in mind that these responses are rapid to avoid harm to the body


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COORDINATION IN MAN

This is the process by which receptors detect stimuli both internal and

external, then passing on information to effectors causing them to respond

appropriately. This maximizes the chance of survival.

Coordination is brought about by the nervous or endocrine system. Sense

organs provide us with information about our surroundings and as a result

we are able to perform a wide range of activities daily. Responses to stimuli

may be made by muscles or groups of secretory cells called glands; together

known as effectors.

Let us look at the following concepts

1. Stimuli2. Sense organs3. Glands

Stimuli (singular stimulus)

A stimulus is simply a change in the environment e.g. a change in light

intensity or a change in pressure on the skin.

Various sources of stimuli in the environment

1. Light energy2. Sound energy3. Temperature changes4. Pressure (touch)5. Chemical changed

Sense Organs

A sense organ may be defined as a part of our bodies made up of a number

of types of tissue and cells which detect stimuli. Examples of parts of our

bodies that respond to or detect stimulus are the eyes (respond to light in

particular the cells in the retina), the tongue (responds to chemical changes.

in particular in our taste buds), the ears detect sound and the nose has small

receptors which detect various smell/scent.


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HOW VARIOUS PARTS OF THE BODY REACT TO CHANGES IN

THE ENVIRONMENT

1. How does the body respond to light energy?Study the diagram below

STRUCTURE OF THE EYE

Objective: Describe and identify from a drawing a horizontal section

through the eye and optic nerve

Fig. 1

1. Iris2. Conjunctiva3. Aqueous humour4. Cornea5. Pupil6. Lens7. Suspensory ligaments8. Cilary muscles9. Vitreous humour10.Choroid11.Selera/Selerotic coat

external eye muscle

choroid

optic nerve

sclera

retina

blind spot

vitreous huimourciliary muscle

iris

pupil

cornea

lens

suspensory

ligaments

aqueous

humour

fovea

conjunctiva


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12.Retina13.Fovea/Yellow spot14.Blind spot15.Optic nerve

FRONT VIEW OF THE EYE

Fig. 2

If possible observe the eye of a friend or simply observe your own eye in themirror and compare it to the diagram above.

FUNCTIONS OF THE EYE

We are able to see things when light is reflected from them

We will now examine how each part of the eye aids in the overall function

of seeing objects.

Eye lid

sclera

pupil

iris

tear

gland

tear

duct


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The ConjunctivaThe conjunctiva is a delicate layer of tissue covering the entir surface od the

eye and inner surfaces of the eyelids.

Aqueous Humour

The fluid bathes the eye. It also helps to maintain the shape of the eye. Itsupplies the lens and the cornea with oxygen and nutrients,

LensThe lens is located just behind the iris. In collaboration with the cornea the

lens bend light rays that enter the eye.

The RetinaThe retina is made up of nerve tissue which sense light entering the eye.

Rods and cones are light sensitive cells found in the retina. Rods only detectblack and white images and cones detect colours. The images send impulses

through the optic nerve to the brain. The brain tranfers the impulses into

images that we can see.

ChoroidThe choroid is a black layer of tissue which contains a network of blood

capillaries which supplies the retina with nutrients and oxygen.


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.

Objectives: Describe the action of the components of the eyes in forminginverted images on the retina.

To achieve the above objectives we must examine how different parts of the

eye deal with light being reflected from images at various distances.

We are able to see things when light is reflected from them. Light rays

travels in a straight line in all directions. Light from objects in the

environment is reflected in all directions. The light rays reflected from an

object enters the eye. The curved surface of the cornea and lens both bend

light rays which enter the eye, so that each ray of light from the object forms

a point of light on the retina. Points of light will form a much smaller and

an upside down image of the object on the retina.

The cornea and the aqueous and vitreous humour are mainly responsible forthe bending (refractions) of light. The lens make final adjustments to the

focusing of the image unto the retina. For the image to be clear and in focus,

the light rays must meet exactly on the retina. We will look more closely

later at images focusing to a point before and beyond the retina and how

these may be corrected. Fig 4.3 and 4.4 illustrate how light from an object

produces a focused inverted image on the retina.

Fig. 4.3


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Fig 4.4 shows how the bending of light by the lens result in the formation of

an inverted image on the retina.

All the other components of the eye work to this end directly or indirectly to

focus the image (inverted) onto the retina. Table 4A outlines the functions of

the various components of the eye in forming an inverted image onto the

retina.

The pattern of sensory cells on the retina stimulated by the points or light

from the object will produce a pattern of nerve impulses which is sent to the

brain via the optic nerve. The brain interprets the pattern and so forms animpression of the real size, distance and upright nature of the objects. Of

course all this happens really, really quickly.

Table 4A summarizes the structure and function of the components of the eyeComponent Description Function

Selera Tough, white, fiberous coating. The frontis clear allowing light to enter the eye

(this is the cornea)

1. Protects the eye ball2. Keeps the spherical

shape of the eye

Conjunctiva Thin transparent membrane continuouswith the eyelids

1. stops the entry of gritinto the eye2. Protects the cornea

Cornea Transparent front part of the selera Refract or bend light rays unto

the retina

Aqueous humour Colourless fluid 1. Refracts light2. Helps maintain the shape

of the eye

Iris Coloured (eye colour brown, blue,Ggey etc) disc composed of muscles.

Controls the amount of lightentering the eye (passing through

Fig 4.4


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How Lens Focus Light on to the Retina - Accommodation

Depending on the nearness of the object, the distance between light rays

changes as they travel from one point to another.

As said before, objects all reflect light andin orderfor us to perceive them we

have to bend and focus the light rays coming from each pointof the object. We

will now examine the mechanism involved in the focusing of light unto the

retina.

Not all rays need bending of equal amount unto the retina.

Focusing on near objects

Light rays coming from nearby objects are strongly diverging (separate,

going in different directions). Therefore they need to be bent equally strongly

inwards (converge) so that each point from that close/near object come to

focus on the retina. The lens ciliary muscle, and suspensory ligaments are

the components of the eye involved in accommodation.

Fig 4. 6 also shows accommodation for near objects. The mechanism involves

contracting of the ciliary muscle removing the tension on the suspensory ligaments.

The lens becomes fatter or more convex due to the elasticity and flexibility. A

thicker lens bends the light rays more strongly than a thin lens. The fatter shaped

lensis much better at bending light rays coming from a close/near object (light rays

aremoving away strongly from each other) than a thin lens which is better suited for

objectsat a distance (light rays almost parallel needs only a little bending)


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Focusing on distant objects

Light rays coming from an object in the distancetravel far enough so that the

rays of light coming from such an object will almost be parallelto each other.Theses rays would not require much bending.

The eye can produce a focused image of either a nearobject or a distant object.

To do this the lens changes its shape becoming thinner fordistant object and

fatter for near objects. The Change in shape is caused by contracting or

relaxing the cilliary muscle See fig. 4.5. The mechanism involves the ciliary

muscle relaxingand the suspensory ligaments holding the lens tight and thus

stretching the lens to a thin degree. The eye is now said to be focused for distantobjects. NBviewing far objects helps to rest the eye as the ciliary muscles are

relaxed. .


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Fig. 4.5

Distant Objects

Fig. 4.6

Near Ob ects


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Summary of behaviour of components during focusing

Viewing Lens Suspensory

ligaments

Ciliary

muscleDistant objects thin tightened relaxedNear objects thick looseded contracted


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The function of rods and cones in the retina in transforming

light energy into nerve impulses

As noted before light sensitive cells within the retina are of two kinds i.e.

rods and cones. Rods are extremely sensitive to light and can detect variousshades of grey/black and function in dim light or very low light intensities.

However, rods cannot distinguish colours and because of this they do not

detect edges well and produce poorly defined imaged (that is at low light

intensities). Rods are mostly located on the edge of the retina. Objects in dim

light are therefore seen more clearly from the corner of the eye.

The cones on the other hand are sensitive to colour and function in only

higher light intensities. This is why colours are not obvious at dark (when

the sun goes down at evening time. The cones are also sensitive to edges, so

they (produce sharp images which attest to the fact that we see more clearly

with brighter light.

The centre of the retina contains a tiny pit densely packed with

approximately 3 million cones called the fovea. The fovea is the most

sensitive part of the retina. The brightest rays are focused here. This part of

the eye produces the sharpest image which is why we tend to move our eyes

and our head so that the image of the object we want to see clearly falls in

that area.

The action of circular muscles in regulating entry of light into

the eye

Remember that a reflex action may be defined as a rapid automatic response

to a stimulus change in the environment by a muscle or a gland which does

not require conscious control or a process of thinking. It is a response system

geared towards protecting the body and the parts thereof.

With the consent of a friend shine a flashlight into his or her eyes and watch

closely to what happens to the iris and subsequently the pupils.


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What happens when bright light is shone into the eyes?

A reflex action occurs.This is because the cells of the retina are stimulated, generated nerve

impulses that are taken to the brain by a special nerve. (sensory nerve). A

message is then sent from the brain via another special nerve (intermediate

then to a motor) to a circular muscle of iris causing them to contract, thereby

reducing the pupil and hence limit the amount of light entering the eye. This

occurs within a fraction of a second.

There are two types of reflex: Cranial reflex which occurs in the head e.g.

blinking and swallowing. Cranial is controlled directly by the brain. The

other is the spinal reflex e.g. the knee jerk. These are controlled by thespinal chord.

All reflex action follows a similar path. Even the action is without thought

the information is picked up by the brain, which determines the details of

your final response. For example covering the eyes with the hands will offer

more protection depending on the intensity of the light. The stimulus picks

up by the receptor cells of the retina are sent directly to the brain and does

not involve the spinal chord. Whereas with other muscles of the body,

message is sent to the brain and the spinal chord.

Otherwise when there is not enough light the opposite happens, resulting in

the relaxing of the circular muscles of the iris, hence opening the pupils

allowing as much light to enter as is present.

Eye Diseases

1. Long/far sighted (hyperopia)Someone who has this condition can see objects in the distance

clearly, but objects nearby maybe blurry. This occurs because the

cornea and the lens are not evenly and smoothly curved and light rays

are not focused properly.


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2. Short/near sighted (Myopia)Someone with this condition can see near objects clearly but distant

objects do not properly focused. This occurs because the eyeballs are

toolong or the cornea is too curved so that the light entering the eye is

not properly focused.

3. AstigmatismSomeone with this condition experiences blurred vision due to either

an irregular shaped cornea or lens. This prevent light from focusing

properly on the retina and as a result distant objects are blurred.

4. Colour blindnessThe individual only sees black and white. This results from the failure

of the nerve supply of cones or failure of the cones themselves.

Hyperopia, myopia and astigmatism can be corrected by wearing

prescribed glasses, contact lens and laser surgery.


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Worksheet 1

Label the following parts on the eye above

a. Corneab. Pupilc. irisd. lense. suspensory ligamentsf. ciliary muscle

2. Name the part of the eye that decreases in size when a bright light is shone

into the eye.


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3. Explain what happens to the iris and the pupil (a) in dim light (b) bright

licht.

Dim Light

Bright light

4. Explain how the eye is nourished?

5. Explain how images are formed on the retina.

(4 marks)

6. You look at a car at a distance and then look at your book in your hand.

(1) Explain the changes the eye would go through to focus the book in

your hand away from the car in the distance.

_____________________________________________________________

_____________________________________________________________

(4 marks)


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(ii) State the name of the process explained in a(i) above.

7. Explain why objects in dim light are seen more clearly from the corner of

the eye?

8. A boy walks into a dimly lit room from a bright sunny day on the out side.

Explain how the eye would adjust to this environmental change.

9. (i) What is astigmatism?

(ii) How can it be corrected?


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THE NERVOUS SYSTEM AND ITS DIVISIONS

Objectives: State the main divisions of the nervous system

The nervous system consists of many nervous or nerve cells ofdifferent types. Almost like a big system made up many smaller

systems the nervous system is where all the sensory information

picked up by receptors (internal and external) are sent and reflex

actions and other actions are coordinated and worked out.

The main divisions of the nervous system are the: The Central Nervous System (CNS) The Peripheral Nervous System (PNS)

The CNS consists of the brain and the spinal cord which is enclosedby the cranium and vertebral column respectively

Fig. 4.7

Human Nervous System

Central Nervous

S stemPeripheral Nervous

System

Brain SpinalCord

Cranial/Sensory

Spinal/Motor


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The PNS consists ofpaired cranial/sensory nerve and spinal/motornerve There are 12 pairs of cranial nerves that control the function of

smell, vision, taste, facial expression, tongue movement etc.

These nerve comes from the base of the brain (cranial) and go tomainly structures of the head e.g. pair of eyes and pair of ears. Cranial

nerves go to both sides of the head in a pair. Spinal/ Motor nerves

come from out of the spinal cord, running to the pair of arms, legs and

various structures in the trunk (like the kidneys).The spinal/Motor

nerve control movement.

Fig 4.8

The brain and the spinal cord make up the central nervous system.


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Objective : Distinguish between neurone and nerve

If you are ever asked to distinguish between a neurone and a nerve (orif you want to know) just think of a rope.

Like a rope the nerve is made up of many single strands of fibres. Thestrands fibres that make up the rope are similar to that of the neurons

that make up the nerve. However, the single strands are intertwined.

In other words, a nerve of the CNS of which there are many, consistsof bundles of fibres (neurons) bound together or held together in a

sheath. This sheath is a tough material called connective tissue or

nerve sheath. .

Therefore neurons do not run through our bodies on their own, but areusually in several hundreds (found in one nerve). An example of a

neurone.

These help us to respond quickly to harmful stimuli which is usuallyour first defense against danger.

Fig. 4.9

neurone


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Nerve consists of several neurones

HOW DOES IT WORK?

The nervous systems main function is to carry or transmit messagesfrom one part of your body to another.

The function of our nervous system is facilitated or made possiblebecause of a network of nerve fibres (neurons) running throughout our

body.

The network of nerve fibres work pretty much like telephone cables.Messages are taken from one end to another along cables.

Why is such a network so essential to the human body? It is simply forcommunication; Just imagine if we did not have this network.


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Objective: State the role of the sensory, intermediate and relay

neurone and spinal synapses

Role of Neurone and Synapses

Before we go any further, I hope we are comfortable with what nervesare as opposed to neurons. A nerve leading away from a receptor

consists only of sensory neurone. A nerve leading to muscle consists

of motor neurons. Sensory intermediate/relay and motor neurone are

also referred to as nerve cells.

Characteristics of Nerve CellsAs you know by now a whole nerve cell is called a neurone/neuronThere are long processes or extensions from the cell bodies of the

nerve cells called dendrons. Dendrons conduct/carry impulses towardsthe cell body.

Axons conduct/carry impulses away from the cell bodyAxons and dendrons are surrounded by myelin sheathThe sheath is for:

1. Insulation of the electrical impulses

2. For fast and efficient movement of the impulses inside the

neurone

Additionally there is what we call nodes or little junction along thelength of the neuroneThese are small gaps in the sheath which increase the rate of

conduction of impulses along the neurone

The myelin sheath cause electric impulses to move rapidly by jumpingnode to node along the length of the fibre.

Role of Spinal SynapsesSynapses are small gaps between dendrites of adjacent neurone.

They allow a large number of neurone to interconnect and ensure

that impulse travel in one direction only.

A nerve impulse can only travel so far along a neurone. Eventuallyit reaches the end of the axon. Usually positioned very close to

another or to a muscle cell or gland.

When a nerve impulse gets to the end of an axon, It must cross thesynapse if it is to continue.


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Messages do not just jump across a synapses. Instead they arecarried by chemical messengers called neurotransmitters.

When the nerve impulse arrives at the synapse it cause the releaseof chemicals from vesicles (or little bubbles).

The chemicals are packaged in these vesicles at the top of the axonThe neurotransmitters diffuse across the synaptic space and bind to

receptors in the membrane on the other side to make an impulse

flow in the other neighbouring neurone

Synapses will occur at the point or junction of connection betweenrelay neurons and sensory neurons

Objective: Describe and recognize from a drawing a simple spinal reflex

arc. You must be able to describe, i.e. state in words or by use of

drawing what a simple reflex arc is?

A Simple Spinal Reflex Arc

When Paul touches the lit match the receptor cells/pain sensors in his

skin pick up the change in temperature (heat) in the environment and

send a stream of nerve impulse through the sensory neurone of the

dorsal root which runs up the arm to the spinal cord.

In the spinal cord, a synaptic connection is made with a relay or

(intermediate) neurone of the ventral root which is stimulated to

generate its own impulse.

This impulse then travels across another synapse to the motor neurone

in the same spinal nerve to an effector muscle which is stimulated to

contract so that the hand is withdrawn

The importance of this action is to protect Paul from being burnt.

Reflex action aids survival.


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Fig 4.10

A Reflex Arc

Study the diagram carefully. You may be asked to reproduce it or parts

of it. Note the connection of the three neurone (the sensory neurone, the

relay or intermediate and the motor neurone)

Role of Each type of Neurone1. Sensory neurone: These conduct impulses from receptors or sensory

cells to the CNS.

2. Motor neurons: These conduct impulses from the CNS to theeffector, which is either a muscle or a gland

3. Intermediate neurone: Conduct impulses throughout the CNS,linking sensory and motor neurone

Steps to the Pathway of Spinal Reflex Arc

1. Stimulus- change in environment outside or within the body e.g.change in temperature or pressure (outside) or decrease/increase in the

glucose concentration in the blood before or after a meal.2. Specific receptors are stimulated: initiation of impulse3. Impulse generated travels along sensory neurone and into the spinal

cord.

4. Message/impulse from a sensory neurone is linked to a motorneurone via a relay/intermediate neurone

Impulse leave spinal cord and travels along motor neurone


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5. Impulse cause effector (e.g. muscle) to contract causing a action/response to occur e.g. withdrawal of hand from heat source or leg to

rise/kick forward upon tapping below the knee jerk response)

There are two types of reflex: Cranial reflex which occurs in the head e.g.

blinking and swallowing. Cranial is controlled directly by the brain. Theother is the spinal reflex e.g. the knee jerk. These are controlled by the

spinal chord.


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H0RMONES

We have looked at how the body responds to external stimuli e.g. heat, light

cold etc. Let us now discuss how our body responds to internal stimuli.

Our bodies also coordinate to respond to internal stimuli (changes) which

function mainly in keeping the internal conditions at a normal level.

For example, a person who has difficulty in maintaining their blood sugar at

a standard level is said to be diabetic. The hormone insulin from the

pancreas controls blood sugar levels.

What is the function of insulin and glucagon?

Insulin helps your liver control the amount of glucose in the blood. Ifyou eat a meal, particularly one containing a lot of glucose, the levels

of glucose in your blood goes up (because digestion releases glucose

from complex sugars and starch).

Islets of Langerbans in the pancreas detects this change in the bloodsugar level (stimuli) and then secreats insulin into the blood.

When insulin arrives at the liver and muscle, it makes them absorbglucose from the blood, where it is used in the muscles for respiration.

Respiration also occurs in the liver but the main action of the liver isthat of converting the glucose or building up into glycogen molecules.

Why? Because it is useful and effective storage form of

carbohydrates. Glycogen is stored in the liver and muscles as

glycogen granules.

When the blood glucose has dropped to the right level, the pancreasstopped secreting insulin and the liver and muscles stop taking up

glucose from the blood.

This control of the blood glucose is an important part of homostasis(maintaining the constant conditions of the body despite the changesin the surroundings).

On the other hand after not eating for some time (fasting), the glucoselevel in the body falls below the normal. This change in blood glucose

level is detected by cells of the Islets of Langerbans.

The hormone glucagon is secreted into the blood. When glucagonarrives at the liver cells, it cause the breakdown of glycogen into


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glucose. What would this do? This action would release glucose

from the storage molecule into the blood until normal glucose levels

are restored.

If changes internally are not addressed or responded to, the bodywill not function at an optimal or efficient level. Hormones are

responsible for regulating body processes. If a person has problems

maintaining their salt or sodium level they are said to be hypertensive

(high blood pressure) or hypotensive, (low blood pressure). This

shows that an inability to maintain a constant internal environment

leads to disease conditions or harmful effects.

Nerves can carry electrical messages very quickly from one part ofyour body to another, but your body also uses chemical messages

though not as quick as impulses. These chemicals are calledhormones.


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What are hormones?

They are chemical substances produced by glands and

transported by the blood stream to control the activities of

certain cells or organs.

Hormones are chemical messengersThey carry messages from glands to organs.This is similar to neurons carrying an impulse

RevisionA gland is a group of similar cells which manufacture and secrete substances

such as hormones and enzymes. An organ is a part of the body whichfunctions as a unit, e.g. heart, kidneys, lungs. Tissues are grouped together to

form organs.

Glands are either ducted or ductless. Ducted glands are those which secrete

enzymes through ducts to the organs needed. Examples include the salivary

gland which secretes saliva into the mouth and the sweat glands into the

skin. Ductless glands are those which secrete hormones directly into the

blood stream. These include the adrenal and the pituitary gland.

Hormones are secreted directly into the blood stream via ductless glands

also called endocrine glands into the blood stream. They travel in the blood

stream to targeted tissues or organs. Cells respond to hormones when they

express specific receptors for that hormones i.e. cells have protein receptors

which recognize the hormone and accepts it. The message that is delivered

by the hormones can only be received by organs that will act on that

message (effectors)

Hormones are responsible for the processes of growth and development,

metabolism, sexual function, reproduction and mood. Some hormones causequick responses such as adrenalin but most are very slow.


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Hormones when released in blood becomes dissolved in the placenta.Although the blood may carry many hormones at a time, they only

affect certain parts of the body. So one could say that hormones are

specific, for a specific effector.

How are hormones dealt with after use?

Once they are used, hormones are changed in the liver to inactivecompounds and are excreted by the kidney. Hence, inactive hormone

compounds form apart of the urine after it has been used.

The human endocrine system consists of endocrine gland whichsecreted hormones directly into the blood fig 4.12 below show the

positions of the main endocrine glands of the human body. Table 4B

shows the different hormones that are secreted by each gland.

Fig, 4.12

The endocrine system consists of endocrine glands which secrete hormones

directly into the blood


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TABLE 4B

The table shows where hormones are made and secreted from and their

function in the body.

Gland Hormone Function/ effect on body

Pituitary Gland (master

gland)

Pituitary growth

hormone

Antidiuretic hormone

(ADH)

Stimulates growth, promoting

bone growth

Secreted when plasma becomes

too concentrated. Stimulates

kidneys to reabsorb more water

from filtrate

Thyroid glands Thyroxine Controls physical growth, mental

growth and metabolic rate. Cause

eretinism: if too little is producedthere is retarded physical and

mental development.

Too little: Low metabolic rate,

sluggishness, obesity: Too much :

high metabolic rate, weight loss,

overactivity, fast heart beat.

Adrenal Gland Adrenalin

When frightened, excited, anxiou

relesed in large amounts

Speed up metabolism, byincreasing blood sugar level,

heartbeat, breathing rate and

blood supply to muscles.


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Kinds of glands

The salivary glands which are found beneath the tongue. They secretesaliva into the salivary duct, which carries it to the buccal cavity(mouth) or empties into the mouth.

The pancreas is actually two glands in one. Most of the pancreas is anordinary gland (ducted) which make pancreatic juice. Which flows

along the pancreatic duct and into the duodenum (revise notes on

digestion)

The rest of the pancreas consists of a group of cells called the (Isletsof Langerbams)

The Islets of Langerbans do not make pancreatic juice (carries outdigestive functions), but make the hormones; Insulin and Glucagon

Insulin and glucagon are secreted directly into the blood, so the isletsof langerbans are endocrime glands


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Objective: describe the role oestrogen and progesterone in the

menstrual cycle and in pregnancy.

MALE HORMONES

Male sex hormones are called androgens. The most important of theseis called testosterone. This is made in the testees or scrotal sacs.

The hormones regulate the development of the male sex organs. Theyalso control the development of secondary characteristics. These

characteristics include:

Growth of facial and pubic hair Breaking of voice (more mature sound) Muscular development

FEMALE HORMONES

In the female, the ovaries produce two groups of hormones; oestrogenand progesterone Oestrogen regulates the development of the

female sex organ, the female secondary characteristics, and the

menstrual cycle. The secondary characteristics include.

Growth of pubic hair

Development of breast Pelvic girdle widening so as girls develop they are able to

carry a child

Males, once into puberty, make sperms all the time. At birth, a femaleOvary contains many thousands of potential egg cells and ova.

However, it is not until she is into puberty that she is able to produce

an egg. After puberty only one egg is developed each month and this

varies for different people. Somewhere around late 40s and early

50s, she no longer produces eggs. All her life as an egg producing

entity, a womans body is controlled by her sex hormones. When thereis a cease in production or reduction of the hormones, the female ages

rapidly and experiences many discomforts, which is why women that

are in menopause (no longer experiencing menstruation) are often

advised or should consider hormone treatment and therapy.


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Role of Oestrogen and Progesterone in the Menstrual Cycle

Since women only produce eggs at times the sex hormonesare released into the blood. The sex Hormones play a special

role in the process and must somehow be regulated.

The release of an egg from the ovary is called ovulation. Thisprocess occurs on a monthly basis.

Ovulation is a part of what is called the menstrual cycle ormenstruation.

Menstrual cycle is the actual breaking down of the uteruswalls in the event that the ovum released did not get fertilized

by a male sperm cell. Fig. 4.14 summarizes the role of

oestrogen and progesterone, observe carefully different

stages.


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Summary of Ovulation

1. Potential ova (plural) inside primary follicle2. Ovum matures inside graafian follicle and produces oestrogen that

builds up the walls of the uterus.

3. Ovulation - graafian follicle moves to edge of ovary, burst releasingmature ovum and the follicle remaining stops secreting oestrogen

4. The follicle becomes a corpus luteum, which starts producingprogesterone, which keeps the uterus lining thick and spongy.

OvulationThe graafin follicle stops secreting oestrogen and becomes a

corpus luteum: the corpus luteum starts to secrete another

hormone progesterone.

Progesterone keeps the uterus lining thick, spongy and wellsupplied with blood in case the egg is fertilized.

If fertilization does not occur, then the corpus leteum graduallydisappears.

Progesterone is not secreted anymore and so the lining of theuterus breaks down and menstruation happens.

The cycle continues when a new follicle starts to develop in theovary a few days after menstruation


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Fast-acting Hormones

Fast and effective, yet very short-lived (think of a fire-craker)This group comprises of hormones, which includes insulin and

adrenalin (the flight or fight hormone) The effect is very fast actingand effective but very short-lived.


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Objective: Distinguish between the hormonal and nervous control

systems

The nervous system and the endocrine systems are the two communicationsystems that regulate all responses and functions of the body.

Table 4c illustrates the distinguishing features of the Endocrine and

nervous Communication system

Nervous System Endocrine System

Control Control

Chemical Substance or Impulse

Messages carried as electrical impulses Messages carried by chemicalalong nerves (bunch of neurone messages in the blood

enclosed by a protein sheath

Speed of Response

Messages are sent rapidly Messages are transmitted slowly

Widespread or Localized Responses

Messages are carried to the precise Messages are carried to moreRegion of the body generalized regions or an area of

the body

Long-term or Short-lived Response

Messages are short-lived or Messages have a long-term or l

Short-lasting effect on the body have a long-lasting effect on the

body

Study the table focusing your attention on how systems differ. Note -

1. Whether or not chemical substances or impulse are used to respond2. What is the speed of the response3. whether or not there is a widespread or localized response4. Long-lived or short-lived response


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Worksheet 2

1. Define a reflex action (2 marks)___________________________________________________________

___________________________________________________________

2. Give an example of a reflex action (1 mark)___________________________________________________________

___________________________________________________________

3. Paul accidentally touches a hot plate and quickly withdraws her hand.Describe the series of events in the nervous system that would cause

paul to react this way. (6 marks)

______________________________________________________________________________________________________________________

___________________________________________________________

___________________________________________________________

___________________________________________________________

___________________________________________________________

___________________________________________________________

4. Explain the importance of Pauls reaction (1 mark)___________________________________________________________

___________________________________________________________

5. Sketch a diagram of the human body showing three glands (6 marks)


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6. State the hormone associated with each gland shown. (3 marks)

_____________________________________________________________

_____________________________________________________________

_____________________________________________________________

7.

Refer to the diagram in this unit showing the pathway by which messages

travel in bringing about the knee jerk. When the tendon is tapped, receptorsin the muscles are stretched and this causes the messages to be set off.

(i) Which structure is stimulated by the tapping of the hammer?_____________________________________________________ (1 mark)

(ii) Give the name of the structure which carries impulses awayfrom the spinal cord?

_____________________________________________________ (1 mark)

(iii) Which structure shortens or moves as a result of the reflex?_____________________________________________________ (2 marks)

*Remember when muscles contract they shorten allowing movement to

occur.

(iv) Name the structure which carries the message back to the muscle for

the appropriate action?

_____________________________________________________(3 mark)

8. (i) Your lunch was a meal rich in carbohydrates and a very sweet soda.

What happens will happen to your blood sugar level?

_____________________________________________________________

_____________________________________________________________


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(2 marks)

(ii) What action is taken by the body to return this to a normal level?

_____________________________________________________________

______________________________________________________ (4 mks)

(iii) Why is it important to control the internal environment of the body?

______________________________________________________ (1mls)

16. Define the term drug dependence

______________________________________________________ (2mks)

9. List below the four (4) main differences between control by the nervous

system and control by the endocrine system.

Nervous Endocrine

1.

2.

3

4

18. State what you would tell someone about the effects of heroine, who is

attempting to start this use.

Short-term

_____________________________________________________________

___________________________________________________ (2 marks)

Long-term

_____________________________________________________________

____________________________________________________ (2 marks)


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10. Distinguish between a neurone and a nerve.

_____________________________________________________________

_______________________________________________________(2 mks)

20. Distinguish between quick-acting hormones and fast acting hormones. In

both cases give an example.

_____________________________________________________________

_____________________________________________________________

_____________________________________________________________

_____________________________________________________________

______________________________________________________(2 mks)

Essay Questions (50 marks)

1. A man pricks his finger while cutting some rose buds. He immediatelywithdraws his hand from the source of pain and cries out. Explain

what is happening to his nervous system to bring about these two

responses.

2. Describe clearly the role of oestrogen and progesterone in themenstrual cycle and in pregnancy. Use annotated diagrams to assist

your explanation.

3. Discuss the misuse of alcohol in Jamaica? What suggestions can youoffer in reducing their ill effects?

Include in your answer a consideration of the consequences for:

(i) The bodys ability to respond to stimuli-reaction time(ii) Coordination(iii) The ability to make quick rational decisions


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coordination and control

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