Transcript Biology 3.5 Responding to Stimuli

Pituitary
O
Responding to Stimuli
Thyroid
Pancreas
Adrenal
By the end of today’s lesson you
should be able to:
• Know the four structures of response in living things
• Outline the nervous system components: central nervous
system (CNS) and the peripheral nervous system (PNS)
• Receptor messages are carried through these systems
by nerve cells or neurons.
•
• The structure and function of a neuron:
variation in size and shape.
• Neuron -- Three part structure:>
dendrite(s), the axon the cell body,
• Outline the structure & function of the
neuron including:
cell body, dendrites, axon, myelin sheath,
schwann cell, and neurotransmitter
vesicles & synaptic cleft
Response
• Living things sense and respond
to environmental changes in a
variety of ways.
• Response is a form of defence
that allows organisms to survive
in their environments.
3.5.1 Structures for response
•
Living things respond in various ways:
1.
2.
3.
4.
Nerve and organ systems
Chemical or hormonal response
Muscular and skeletal systems
Immune systems
Human responses – the nervous
system
The Nervous System
 A stimulus is any change in your
environment
e.g. a flash of light, a noise, a fly
landing on your nose.
 A nervous system allows an
organism to detect and respond to
stimuli in its internal or external
environment.
The nervous system in the
human is made up of two
different parts:
 The central nervous system (CNS)
is your brain and spinal cord.
 The peripheral nervous system
(PNS) is the nerves branching
from the CNS to all parts of the
body.
Check your learning..
• What is a stimulus?
• How does our nervous system help to
protect us?
• What is the difference between the CNS
and the PNS?
By the end of today’s lesson you
should be able to:
• Three different types of neuron
• The structure and function of a neuron: variation in size
and shape.
• Neuron -- Three part structure:> dendrite(s), the axon the
cell body,
• Outline the structure & function of the neuron including:
cell body, dendrites, axon, myelin sheath, schwann cell,
and neurotransmitter vesicles & synaptic cleft
 A neuron is a specialised cell that carries electrical messages
(impulses) around the body.
 They vary in size and shape depending on their job.
There are three types of Neuron :
 Sensory neuron –carries
messages from the sense
organ to the central nervous
system (CNS).
 Interneuron –connects
sensory and motor neurons
and so carries messages
within the CNS.
 Motor neuron –carries
impulses from the CNS to
muscles and glands.
Carrying messages along neurons
• Messages are carried around the body by
the neurons.
• The conduction of an impulse along a
neuron involves the movement of ions.
 Dendrites receives information and carry it towards the cell
body.
 The cell body contains the nucleus and other organelles and
produces neurotransmitter chemicals.
 The axon conducts impulses away from the cell body.
 Many Schwann cells wrap their fatty cell membranes
around an axon, forming a myelin sheath.
 The myelin sheath insulates the neuron from electrical
impulses flowing in other neurons.
By the end of today’s lesson you
should be able to:
• Outline the structure & function neurotransmitter vesicles
& synaptic cleft
• Outline impulse movement & synapse.
• Explain activation & inactivation of neurotransmitter.
 Synapse—place where two neurons come into close contact.
 Synaptic cleft—the gap between two neurons
Carrying messages along neurons
• When an impulse reaches the end of a
neuron it causes chemicals to be released
called neurotransmitters.
• The neurotransmitters are said to be
activated
 Neurotransmitter—chemical released across a synaptic
cleft to carry a signal from one neuron to another.
Carrying messages along neurons
• The neurotransmitters diffuse across the
synaptic cleft.
• They are taken in by the next neuron and
cause a new impulse to be started here!
Deactivation of neurotransmitters
• Some neurotransmitters remaining in the
synaptic cleft will be broken down by an
enzyme – this is called inactivation
• The remaining chemicals are reabsorbed
into the presynaptic neuron and used
again to make new neurotransmitters.
Nervous System Disorder
Parkinson’s disease is a nervous system
disorder in which muscles become rigid and
movement is slow and difficult, with persistent
tremors [shaking].
Causes of the disease
In people with Parkinson’s disease it is found
that the brain has reduces the normal amount of
dopamine that it makes.
The lack of dopamine neurotransmitter causes
signalling problems in the body – some
messages can’t be carried properly
Treatment
There is at present no means of
preventing it, but giving L-dopa (which the
body changes into dopamine) can relieve
the symptoms in many patients.
Think...
• Depression is known to be caused by a
lack of the neurotransmitter serotonin in
the brain
• How could a pharmacologist tackle this
problem?
Can you…
• Outline the structure & function of the neuron
including:
cell body, dendrites, axon, myelin sheath,
schwann cell, and neurotransmitter vesicles &
synaptic cleft
• Outline impulse movement & synapse.
• Explain activation & inactivation of
neurotransmitter.
 Outline disorders from NS disorders: Parkinson's
including:Cause/Treatment
By the end of today’s class…
• Outline the role of CNS, brain & spinal cord.
 State location & function of cerebrum /
hypothalamus / pituitary gland / cerebellum /
medulla oblongata
The central nervous system
 The central nervous system (CNS) is
your brain and spinal cord.
The Brain
 The cerebrum is our
conscious brain, with
different parts having
different jobs to do.
hypothalamus
 The hypothalmus is
the centre for the
regulation of the
internal organs.
pituitary
 The pituitary gland secretes hormones that stimulate
other glands to release their hormones.
cerebrum
 The cerebellum co-ordinates processes that we have
learned to do automatically, such as speaking.
Medulla
oblongata
cerebellum
 The medulla oblongata co-ordinates involuntary,
automatic processes — such as breathing, heartbeat.
Conscious actions
A conscious action is one where the brain makes a considered response.
Here’s what happens:
4) The brain
3) Here another sensory neuron
decides to move
carries the signal to the brain
away the hand
5) This impulse is
sent by MOTOR
NEURONS to the
hand muscles (the
effectors) via the
spinal chord…
2) The impulse is carried
by SENSORY NEURONS
to the spinal chord
1) Receptors in
your skin detect
a stimulus
Stimulus
6) Which then
moves the hand
away
Receptor
Motor Neuron
Sensory Neuron
Effector Muscle
Coordinator
Response
Consider this
You've got an itchy ear!!
What will you do???
Think about how the message will get passed around your body and how your
body would respond
LEARNING CHECK
• Name the 3 main parts of the brain and one
function of each.
• How is the brain protected?
• What is meant by “conscious action”?
• What does the term “involuntary” mean?
• Distinguish between the cerebrum and the
cerebellum.
By the end of today’s class you
should be able to:
• Outline the role of CNS, brain & spinal
cord
 The spinal cord is
protected by the
vertebrae, meninges
(three membranes) and
cerebrospinal fluid.
 It sends impulses to
and from the brain and
controls many reflex
actions.
Grey matter contains cell bodies and dendrites
Outside the grey matter, the spinal cord consists of white
matter (containing axons only).
spinal nerves branch off
from the spinal cord.
 The dorsal root consists of
nerve fibres carrying
information into the spinal
cord from the senses
The ventral root consists of
nerve fibres carrying
information out from the spinal
cord, to the muscles and
glands.
Peripheral nervous systems
 The peripheral nervous system
(PNS) is the nerves branching
from the CNS to all parts of the
body.
PNS
• The dendrites and axon parts of some
neurons are found in the PNS.
• The cell body part of neurons are
found in the CNS or in ganglia
REFLEX ACTION --- The Reflex Arc
 A reflex action is a quick, automatic response to a particular stimulus.
Interneuron
Suppose you touch a hot flame.
A message is sent from pain receptors in the skin to the
spinal cord by a sensory neuron
In the spinal cord, the message is passed on to an interneuron
and then to a motor neuron, and so into muscles that respond by
contracting and pulling your hand from the flame.
Interneuron
By the end of today’s lesson you
should be able to:
• Know that sense organs contain receptors,
with the brain as an interpreting centre for
received information.
• Knowledge of the five senses and related
organs.
• Study the eye– recognition and function of
the main parts.
SENSE ORGANS
 Animals collect information about their environment by
using receptor cells.
 A receptor is a cell that can detect a stimulus (any
change in the environment).
 Each of our sense organs contain receptor cells.
 We have five sense organs – the eye, the ear, the
tongue, the nose and the skin.
 The five senses are sight, hearing, touch, taste and
smell.
Our nose
Sense
Organ
Sight
Eye
Hearing
Ear
Touch
Skin
Taste
Tongue
Smell
Nose
Stimulus detected
light [by rods and cones in the retina]
sound [receptors in cochlea]
touch, pressure, temperature and pain
[receptors spread throughout body]
chemicals [taste buds detect sweet, sour,
salt and bitter].
chemicals [receptors in the nasal cavity
detect vapours]
The eye
Section through a mammalian eyeball
The EYE
 Eyelids
can
cover
and
protect
the
eyes.
Eyelid
Conjunctiva
Cornea
 Conjunctiva
— thin
transparent
lining
protecting
the cornea.
 Cornea—front transparent part of the sclera. It focuses light
rays on the retina.
Sclera
Choroid
Retina
 Sclera—tough
fibrous outer
layer – the
‘white’ of the
eye;
it maintains the
shape of the
eyeball.
 Choroid—contains blood vessels supplying food and
oxygen to the cells of the eye.
 Retina—the innermost layer that contains the receptor
cells [rods and cones].
Conjunctivitis
• is an inflammation of the conjunctiva most
commonly due to an allergic reaction or an
infection (usually bacterial, but sometimes
viral).
 The fovea is
where our
best vision is
[mainly
cones]
Fovea
Iris
 Iris—controls the amount of light entering the eye
[through the pupil].
Pupil
 In bright light, pupil
decreases in size
 In dim light, the
pupil increases
in size
 Ciliary body [muscle] —controls the shape of the lens
Ciliary muscle
 Suspensory
ligaments —
hold the lens
in place.
Suspensory ligaments
Lens
 Lens—it focuses the light rays on the retina.
A cataract is a clouding that develops in the
lens of the eye which obstructs the passage of
light
Seeing things at different distances
For distant objects,
the ciliary muscle
relaxes and the shape
of the lens is thinner–
the light doesn’t bend
as much.
For close objects the
ciliary muscle contracts,
and the shape of the
lens to goes fatter, thus
bending the light more.
 Aqueous humour— keeps the shape of the cornea and lens.
Aqueous humour Vitreous humour
 Vitreous humour—gel that helps maintain the shape of the
eye.
 When light rays focus on the retina, receptor cells are
stimulated and impulses are carried along the optic nerve to
the brain.
Optic nerve
Blind
Spot
 Blind spot—where the optic nerve fibres pass through the
retina and there is no room for receptors!
Can you…
• Recognise the main parts of the eye and
explain their functions?
The eye
Section through a mammalian eyeball
The eye
Section through a mammalian eyeball
Objectives
• Today:
• You should learn the parts of the ear, and
all of their functions.
• How the ear works
• One disease of the ear – cause and
correction
The Outer ear
 Pinna—funnels
sound into the ear
canal.
 Ear canal —tube leading
to the ear drum. It has
hairs and wax glands to
trap dirt and germs.
 Eardrum—membrane of
skin that vibrates when
sound waves hit it.
Eardrum
Pinna
Ear
Canal
Middle
Ear
 Ossicles— 3 small bones
[hammer, anvil and stirrup], that
amplify the sound.
Ossicles
 Eustachian tube- keeps air
pressure equal on each side of
the eardrum.
Eustachian
tube
 Cochlea—a coiled, fluidfilled tube that convert
sound vibrations into
electrical impulses.
Inner Ear
Semi-circular canals
 Semi-circular canals—help
us keep our balance and
posture.
Cochlea
How does the ear hear?
How does the ear hear?
1.Sound waves are
collected by the
pinna,
6.The auditory nerve
takes the signals
to the brain.
6
4
1
2
3
5
2. The waves
travel along
the ear canal.
3.The waves
make the ear
drum vibrate.
4.The ossicles
amplify the
vibrations.
5.Tiny hairs in the
cochlea sense the
vibrations and turns
them into electrical
signals.
Glue ear
• A hearing disorder in children which results in some
deafness.
• Cause –Eustachian tube becomes blocked and too much
sticky fluid collects in the middle ear. Prevents the bones in
the middle ear from vibrating!
• Correction – nose drops taken to decongest and unblock the
Eustachian tubes.
Can you….
• Name the parts of the ear, and all of their
functions?
• Explain how the ear works
• Describe one disease of the ear – cause
and correction!
How loud is loud?
decibels
aircraft
overhead
160
personal stereo
140
permanent
ear damage
120
100
loud
bell
80
quiet
countryside
60
40
pin being
dropped
circular saw
at 2m
20
0
can just
be heard
Ear Defects – additional info
Deafness
Deafness can be caused by long exposure to a high level of
noise, drugs, or ear infections.
Damage to the eardrum, ossicles [bones], and cochlea,
which can be caused by loud sounds, produces incurable
deafness.
Workers exposed to
prolonged sounds of over 90
decibels [dB] are obliged by
law to wear ear protection.
Any exposure to 140 dB
causes immediate damage
to hearing.