iGCSE Biology Section 2 lesson 8

Structures and functions in living organisms Content Section 2 Structures and functions in living organisms a) Levels of organisation b) Cell structure c) Biological molecules d) Movement of substances into and out of cells e) Nutrition f) Respiration g) Gas exchange h) Transport i) Excretion j) Coordination and response

Lesson 8 Content j) Coordination and response 2.77 understand that organisms are able to respond to changes in their environment 2.78 understand that homeostasis is the maintenance of a constant internal environment and that body water content and body temperature are both examples of homeostasis 2.79 understand that a coordinated response requires a stimulus, a receptor and an effector Flowering plants 2.80 understand that plants respond to stimuli 2.81 describe the geotropic responses of roots and stems 2.82 describe positive phototropism of stems Humans 2.83 describe how responses can be controlled by nervous or by hormonal communication and understand the differences between the two systems 2.84 understand that the central nervous system consists of the brain and spinal cord and is linked to sense organs by nerves 2.85 understand that stimulation of receptors in the sense organs sends electrical impulses along nerves into and out of the central nervous system, resulting in rapid responses 2.86 describe the structure and functioning of a simple reflex arc illustrated by the withdrawal of a finger from a hot object 2.87 describe the structure and function of the eye as a receptor 2.88 understand the function of the eye in focusing near and distant objects, and in responding to changes in light intensity 2.89 describe the role of the skin in temperature regulation, with reference to sweating, vasoconstriction and vasodilation 2.90 understand the sources, roles and effects of the following hormones: ADH, adrenaline, insulin, testosterone, progesterone and oestrogen. Lesson 8 j) Coordination and response

Lesson 8 Content j) Coordination and response 2.77 understand that organisms are able to respond to changes in their environment 2.78 understand that homeostasis is the maintenance of a constant internal environment and that body water content and body temperature are both examples of homeostasis 2.79 understand that a coordinated response requires a stimulus, a receptor and an effector Flowering plants 2.80 understand that plants respond to stimuli 2.81 describe the geotropic responses of roots and stems 2.82 describe positive phototropism of stems Humans 2.83 describe how responses can be controlled by nervous or by hormonal communication and understand the differences between the two systems 2.84 understand that the central nervous system consists of the brain and spinal cord and is linked to sense organs by nerves 2.85 understand that stimulation of receptors in the sense organs sends electrical impulses along nerves into and out of the central nervous system, resulting in rapid responses 2.86 describe the structure and functioning of a simple reflex arc illustrated by the withdrawal of a finger from a hot object 2.87 describe the structure and function of the eye as a receptor 2.88 understand the function of the eye in focusing near and distant objects, and in responding to changes in light intensity 2.89 describe the role of the skin in temperature regulation, with reference to sweating, vasoconstriction and vasodilation 2.90 understand the sources, roles and effects of the following hormones: ADH, adrenaline, insulin, testosterone, progesterone and oestrogen. Lesson 8 j) Coordination and response

Lesson 8 Content j) Coordination and response 2.77 understand that organisms are able to respond to changes in their environment 2.78 understand that homeostasis is the maintenance of a constant internal environment and that body water content and body temperature are both examples of homeostasis 2.79 understand that a coordinated response requires a stimulus, a receptor and an effector Flowering plants 2.80 understand that plants respond to stimuli 2.81 describe the geotropic responses of roots and stems 2.82 describe positive phototropism of stems Humans 2.83 describe how responses can be controlled by nervous or by hormonal communication and understand the differences between the two systems 2.84 understand that the central nervous system consists of the brain and spinal cord and is linked to sense organs by nerves 2.85 understand that stimulation of receptors in the sense organs sends electrical impulses along nerves into and out of the central nervous system, resulting in rapid responses 2.86 describe the structure and functioning of a simple reflex arc illustrated by the withdrawal of a finger from a hot object 2.87 describe the structure and function of the eye as a receptor 2.88 understand the function of the eye in focusing near and distant objects, and in responding to changes in light intensity 2.89 describe the role of the skin in temperature regulation, with reference to sweating, vasoconstriction and vasodilation 2.90 understand the sources, roles and effects of the following hormones: ADH, adrenaline, insulin, testosterone, progesterone and oestrogen. Lesson 8 j) Coordination and response

The Central Nervous System

The Central Nervous System Brain

The Central Nervous System Brain Spinal cord

The Central Nervous System Brain Spinal cord Spinal nerves

The Central Nervous System Brain Spinal cord Spinal nerves Cell body Motor neurone Direction of impulse

The Central Nervous System Brain Spinal cord Spinal nerves Sensory neurone Cell body Direction of impulse

The Central Nervous System Brain Spinal cord Spinal nerves Relay neurone Cell body

Nerve cell (neurone) Neurones are specially adapted cells that can carry impulses (electrical signals)

They are very long (elongated) and connect parts of the body Nerve cell (neurone) Neurones are specially adapted cells that can carry impulses (electrical signals) They are very long (elongated) and connect parts of the body

They are very long (elongated) and connect parts of the body Nerve cell (neurone) Neurones are specially adapted cells that can carry impulses (electrical signals) They are very long (elongated) and connect parts of the body They have branched endings to allow a single neurone to link to may muscle fibres

They are very long (elongated) and connect parts of the body Nerve cell (neurone) Neurones are specially adapted cells that can carry impulses (electrical signals) They are very long (elongated) and connect parts of the body They have branched endings to allow a single neurone to link to may muscle fibres The cell body has many connections, so enabling communication with other neurones

Myelin (fatty) sheath) Nerve cell (neurone) Dendrites Cell body Myelin (fatty) sheath) Axon endings

Eg. removing the hand from a hot object. The Reflex Action A reflex action is a rapid, unlearned response to a stimulus. It has a high survival value. When specific receptors are stimulated they cause a very fast, automatic response to the presence of danger. Co-ordination between the sensory and motor neurones takes place without the need for conscious thought. Eg. removing the hand from a hot object.

The Reflex Action

Stimulus, eg. a hot object The Reflex Action Stimulus, eg. a hot object

The Reflex Action Receptor eg. in the skin

The Reflex Action Sensory neurone

The Reflex Action Relay neurone

The Reflex Action Motor neurone

The Reflex Action Effector, eg. muscle

1. The receptor is stimulated by the hot object The Reflex Action 1 1. The receptor is stimulated by the hot object

The Reflex Action 2. This causes an impulse to pass along. 1 1. The receptor is stimulated by the hot object

The Reflex Action 2. This causes an impulse to pass along. 3. The spinal cord (or brain) co-ordinates response without conscious thought. 2. This causes an impulse to pass along. 3 2 1 1. The receptor is stimulated by the hot object

The Reflex Action 2. This causes an impulse to pass along. 3. The spinal cord (or brain) co-ordinates response without conscious thought. 2. This causes an impulse to pass along. 4. An impulse is transmitted along a motor neurone 3 2 4 1 1. The receptor is stimulated by the hot object

The Reflex Action 2. This causes an impulse to pass along. 3. The spinal cord (or brain) co-ordinates response without conscious thought. 2. This causes an impulse to pass along. 4. An impulse is transmitted along a motor neurone 3 2 4 5 1 1. The receptor is stimulated by the hot object 5. The muscle contracts in response to the stimulus

1. Receptors in your foot detect a stone in your shoe The Conscious Action 1. Receptors in your foot detect a stone in your shoe 1

The Conscious Action 2. An impulse is sent along a sensory neurone 1. Receptors in your foot detect a stone in your shoe 2

The Conscious Action 2. An impulse is sent along a sensory neurone 3 3. In the spinal cord another sensory neurone takes the impulse to the brain 2. An impulse is sent along a sensory neurone 3 1. Receptors in your foot detect a stone in your shoe

The Conscious Action 4. The brain co-oordinates the input and output 4 3. In the spinal cord another sensory neurone takes the impulse to the brain 4 2. An impulse is sent along a sensory neurone 1. Receptors in your foot detect a stone in your shoe

The Conscious Action 4. The brain co-oordinates the input and output 3. In the spinal cord another sensory neurone takes the impulse to the brain 5. An impulse is sent along a motor neurone in the CNS 5 2. An impulse is sent along a sensory neurone 1. Receptors in your foot detect a stone in your shoe

The Conscious Action 4. The brain co-oordinates the input and output 3. In the spinal cord another sensory neurone takes the impulse to the brain 5. An impulse is sent along a motor neurone in the CNS 2. An impulse is sent along a sensory neurone 6. The impulse leaves the CNS via another motor neurone 1. Receptors in your foot detect a stone in your shoe 6

The Conscious Action 4. The brain co-oordinates the input and output 3. In the spinal cord another sensory neurone takes the impulse to the brain 5. An impulse is sent along a motor neurone in the CNS 2. An impulse is sent along a sensory neurone 6. The impulse leaves the CNS via another motor neurone 1. Receptors in your foot detect a stone in your shoe 7. Muscles (the effectors) lift the foot out of the shoe 7

Responding to our environment LIGHT receptors in the EYES TASTE receptors in the TONGUE SOUND receptors in the EARS SMELL receptors in the NOSE CHANGE OF POSITION receptors in the EARS (balance) TOUCH, PRESSURE and TEMPERATURE receptors in the SKIN

Responding to our environment LIGHT receptors in the EYES TASTE receptors in the TONGUE SOUND receptors in the EARS SMELL receptors in the NOSE CHANGE OF POSITION receptors in the EARS (balance) TOUCH, PRESSURE and TEMPERATURE receptors in the SKIN

The Eye

The Eye

The Eye Structure Function 1. Cornea 2. Iris 3. Lens 4. Ciliary muscle 5. Retina 6. Optic nerve

Front of the eye, helps to focus the light Structure Function 1. Cornea Front of the eye, helps to focus the light 2. Iris 3. Lens 4. Ciliary muscle 5. Retina 6. Optic nerve

The Eye Structure Function Front of the eye, helps to focus the light 1. Cornea Front of the eye, helps to focus the light 2. Iris Controls the amount of light reaching the back of the eye. 3. Lens 4. Ciliary muscle 5. Retina 6. Optic nerve

The Eye Structure Function Front of the eye, helps to focus the light 1. Cornea Front of the eye, helps to focus the light 2. Iris Controls the amount of light reaching the back of the eye. 3. Lens Focuses the light rays on the retina 4. Ciliary muscle 5. Retina 6. Optic nerve

The Eye Structure Function Front of the eye, helps to focus the light 1. Cornea Front of the eye, helps to focus the light 2. Iris Controls the amount of light reaching the back of the eye. 3. Lens Focuses the light rays on the retina 4. Ciliary muscle Alters the shape of the lens so it can focus on near and distant objects. 5. Retina 6. Optic nerve

The Eye Structure Function Front of the eye, helps to focus the light 1. Cornea Front of the eye, helps to focus the light 2. Iris Controls the amount of light reaching the back of the eye. 3. Lens Focuses the light rays on the retina 4. Ciliary muscle Alters the shape of the lens so it can focus on near and distant objects. 5. Retina Contains the light sensitive receptor cells 6. Optic nerve

The Eye Structure Function Front of the eye, helps to focus the light 1. Cornea Front of the eye, helps to focus the light 2. Iris Controls the amount of light reaching the back of the eye. 3. Lens Focuses the light rays on the retina 4. Ciliary muscle Alters the shape of the lens so it can focus on near and distant objects. 5. Retina Contains the light sensitive receptor cells 6. Optic nerve Sends impulses from the retina to the brain.

The Eye

Focusing on near and distant objects suspensory ligaments pull tight ciliary muscles relax lens is pulled thinner and so light isn’t bent as much.

Focusing on near and distant objects NEAR OBJECT suspensory ligaments relax and go slack ciliary muscles contract lens becomes fatter and so light is bent much more.

Responding to changes in light intensity The IRIS is the coloured part, and made of muscle. The PUPIL is made bigger or smaller by the iris

Responding to changes in light intensity In brighter light the pupil is made smaller by the iris, so limiting the amount of light hitting the retina In dim light the pupil is made larger by the iris, so allowing as much light as possible to hit the retina

The skin and temperature control In cold conditions, the erector muscles contract, pulling the hairs away from the skin (the ‘wet suit’ effect). The sweat glands stop producing sweat. Capillaries near the skin surface are closed, preventing excessive heat loss from the skin ( = vasoconstriction)

The skin and temperature control In hotter conditions, the erector muscles relax, the hairs lie closer to the skin surface. The sweat glands produce sweat. Capillaries near the skin surface are opened, allowing excessive heat to be lost from the skin ( = vasodilation)

Lesson 8 Content j) Coordination and response 2.77 understand that organisms are able to respond to changes in their environment 2.78 understand that homeostasis is the maintenance of a constant internal environment and that body water content and body temperature are both examples of homeostasis 2.79 understand that a coordinated response requires a stimulus, a receptor and an effector Flowering plants 2.80 understand that plants respond to stimuli 2.81 describe the geotropic responses of roots and stems 2.82 describe positive phototropism of stems Humans 2.83 describe how responses can be controlled by nervous or by hormonal communication and understand the differences between the two systems 2.84 understand that the central nervous system consists of the brain and spinal cord and is linked to sense organs by nerves 2.85 understand that stimulation of receptors in the sense organs sends electrical impulses along nerves into and out of the central nervous system, resulting in rapid responses 2.86 describe the structure and functioning of a simple reflex arc illustrated by the withdrawal of a finger from a hot object 2.87 describe the structure and function of the eye as a receptor 2.88 understand the function of the eye in focusing near and distant objects, and in responding to changes in light intensity 2.89 describe the role of the skin in temperature regulation, with reference to sweating, vasoconstriction and vasodilation 2.90 understand the sources, roles and effects of the following hormones: ADH, adrenaline, insulin, testosterone, progesterone and oestrogen. Lesson 8 j) Coordination and response

End of Section 2 Lesson 8 In this lesson we have covered: The Central Nervous System Nerve cells (neurones) The Reflex Action The Conscious Action Structure and Function of the Eye The Skin and Temperature Control