biology m3 response
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Lesson 5: RECEPTORS AND EFFECTORSLesson 6: CENTRAL NERVOUS SYSTEMLesson 7: PERIPHERAL NERVOUS SYSTEM
Module 3 Unit 10
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RECEPTORS AND EFFECTORS
Module 3 Unit 10 Lesson 5
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Objectives
You should be able to:1. define receptors and effectors.2. describe the relationship
between the receptor, the central nervous system and the effector.
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What is the overall job of the nervous system?
Our survival depends on us being sensitive to our surroundings - i.e. to be able to detect any changes both externally and internally and be able to respond to them in appropriate ways so that we maintain homeostasis.
We do that through our nervous system.
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A blind cricketer bowling!
The nervous system consists of: the brain,spinal cord, nervesand sense organs.Even if there is damageor impairment of somesense organs, ournervous system still enables us to dovarious activities!
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What is a stimulus?
A stimulus is any change in the internal or external environment, perceived by sense organs or sensory cells.
Examples are sounds/noises, smells, light, increased heat/cold, increase/decrease in chemicals/sugars in the blood, etc.
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What is Response?
Response is the change in behaviour of an organism, because of a stimulus.
In animals, responses can be learned or are in-born/innate, and are carried out by muscles (so involve movement) or glands.
A response can also be in the form of growth of specific body parts, e.g. breathing roots that grow in mangroves.
Responses usually ensure homeostasis and are important for survival.
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Receptors
You have the ability to receive external stimuli via receptors in four sense organs (of sight, hearing, smell, and taste) located in specific parts of your body, but, your sense of touch is found all over.
Your internal organs also have sensory nerve endings with their sensory receptors which receive stimuli from your internal environment - e.g. about concentration of chemicals, temperature.
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Magnified surface of human skin
Your skin is a largesense organ that gives you information about things with which your body comes in contact.
Look at your own skin surface with a hand lens; what can you see? Well, you cannot see any sensory receptors, but they are present in your skin!
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Skin receptors
Your body has different types of nerve endings scattered throughout your skin, many with receptors at the endings, that all receive stimuli from outside.
The most common receptors in skin are: touch or pressure, pain, heat and cold. Look at them in the diagram in the next slide.
Pain receptors are probably the most important for your safety because they can protect you by sending impulses to your brain that your body is hurt!
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The skin receptors
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Dermis
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Receptors/Effectors at work
How do these receptors in your skin relate to other parts of your nervous system? Watch the video at the website below: http://health.howstuffworks.com/adam-200012.htm
View the next slide which shows a
flow chart of the sequence of events from stimulus received to the response by an effector. Talk about it with your teacher. 12
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Stimulus
Receptor
Sensory neurone
CentralNervousSystem
Motor neurone
Effector
Response
Flow chart of the sequence of events from stimulus received to the response by an effector
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START ANIMATIO
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Receptors working with effectors
Our sense organs contain special receptor cells which will detect a change in our external/internal environment (a stimulus)
The receptor cells will change the stimulus into an electrical impulse which is passed along nerve cells
The message will usually go to the brain, and sometimes to the spinal cord, which will then process and interpret it
The brain/spinal cord then sends an electrical message along nerve cells to an effector organ (usually a muscle or a gland)
The effector organ will then give a response (e.g. a muscle will move, or a gland will produce a hormone)
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The Central Nervous SystemModule 3 Unit 10 Lesson 6
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Introduction
Review the pictures on the previous slide.
What emotions are the dancers feeling? Are the babies happy or sad? How hard are the respiratory organs and
muscles of the ball players responding? Perhaps their hearts are beating faster than usual? Their eyes opened wider? Their breathing is deeper and faster?
What digestive juices are flowing in the little boy’s body as he eats his apple?
The Nervous system controls all of these!
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Objectives
You should be able to:1. describe the parts of the
central nervous system.2. list the main function/s that
each part performs.
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The parts of the nervous system The nervous system consists of: the brain,
spinal cord, nerves and sense organs. Central nervous system = brain and brain
stem and the spinal cord; Peripheral nervous system = all nerves off
the brain (cranial nerves), nerves coming off the spinal cord (spinal nerves) and sense organs.
Talk with your teacher about the
organizational flow chart in the next slide.18
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Human Nervous System
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Brain
Spinal cord
Cerebellum
Cerebrum
Medulla oblongata
The Central Nervous System (CNS)
CNS = Brain, Brain stem (Medulla oblongata) and Spinal Cord
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Parts of the Brain
The brain is the centre of the nervous system, like the microprocessor in a computer. The Cerebrum is the biggest and
heaviest part. It is the ‘thinking part’ of the brain controlling voluntary or conscious activities such as learning, judgment etc.
The Cerebellum is at the back of the brain below the cerebrum; controls balance, movement and co-ordination. 21
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Parts of the Brain
Brain stem or Medulla Oblongata - connects the brain and the spinal cord; controls all the body functions like breathing, blood pressure, heart rate, circulating blood and swallowing)
Pituitary gland is tiny but produces and releases hormones, which help you grow and help children change into adults.
Hypothalmus regulates the body temperature.
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The Lobes of the human brain
Note: Each brain lobe coloured differently
Visit the websitesto read about thehuman brain. http://en.wikipedia.org/wiki/Lobes_of_the_brain
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Functions of each cerebral lobe Frontal lobe - conscious thought; damage can
result in mood changes Parietal lobe - plays important roles in
integrating sensory information from various senses, and in the manipulation of objects; portions of the parietal lobe are involved with visuo-spatial processing
Occipital lobe - sense of sight; lesions can produce hallucinations
Temporal lobe - senses of smell and sound, as well as processing of complex stimuli like faces and scenes.
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Functions of the brain
Sense organs receive external and internal stimuli so they act as receptors. Each type of receptor is sensitive to only one type of stimulus.
When a receptor is stimulated, it generates nerve impulses that are transmitted to the spinal cord and/or the brain, but we are conscious of a sensation only if the impulses reach the cerebrum.
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The Spinal Cord
The spinal cord is a bundle of nerve tissues. It is protected by a series of doughnut-shaped bones called vertebrae which surround it.It is about 43 - 45 cm long and approximately as wide as a human finger. About 13,500,000 neuronstransmit their electro-chemical signals through the spinal cord.
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Functions of the Spinal Cord
Serve as a conduit for sensory information, which travels up the spinal cord.
Serve as a conduit for motor information, which travels down the spinal cord.
Serve as a centre for coordinating certain reflexes.
http://en.wikipedia.org/wiki/Spinal_cord 28
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Module 3 Unit 10 Lesson 7
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Peripheral NervousSystem
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Objectives
You should be able to:1. describe the parts of the
peripheral nervous system.2. list the main function/s that
each part performs.
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Peripheral Nervous System
Consists of: Sensory division and Motor division; so, it includes all, nerves and sense organs, sensory and motor neurons.
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Peripheral Nervous System
You should be able to:distinguish between a nerve and a
nerve cell or neuron. identify and label diagrams of each
type of neuron, and state the main function of each type.
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What is a Nerve?
The nerves that are easily visible to the unaided eye within our body are not single cells. Rather, each nerve is a bundle of nerve fibers from nerve cells or neurons, each fibre being a portion of a nerve cell.
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Nerves
The fibers that make up a nerve are all traveling in the same direction and are bound together with connective tissue for the sake of convenience, though the individual fibers of the bundle may have widely differing functions.
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X.S. of a Nerve showing one nerve fibre from a neuron, also in X.S.
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Nerves
There are no cell bodies of neurons in nerves – only fibres; the cell bodies of neurons (nerve cells) are found only in the CNS or in the ganglia.
Nerves carry electrochemical signals to and from different areas of the nervous system and between the nervous system and other tissues/organs. 36
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Nerves
Nerves are divided into four classes:1. Cranial nerves connect your sense organs
(eyes, ears, nose, mouth) to your brain. 2. Central nerves connect areas within the
brain and spinal cord. 3. Peripheral nerves connect the spinal cord
with your limbs. 4. Autonomic nerves connect the brain and
spinal cord with your organs (heart, lungs, bladder, digestive organs, skin, etc.).
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Underside of the brain showing twelve pairs of cranial nerves
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Spinal Cord and Nerve Structures
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What is a Neuron?
A neuron is a long, wiry, nerve cell that carries nerve impulses or electrical messages to and from the brain, and throughout the nervous system, at up to 200 mph.
The messages come from receptors in the eyes, skin, nose, ears, tongue as well as in various internal organs/glands.
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What does a neuron look like?
The neuron consists of a cell body with branching dendrites or signal receivers and a projection called an axon, along which the nerve signal travels.
At the other end of the axon, the axon terminals or transmitters pass the electro-chemical signal across a synapse (the gap between the axon terminal and the receiving cell).
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Types of Neurons
Neurons are named according to their function
1. Sensory (Receptor/Afferent) Neuron:
Receives stimuli from the environment.
‘Afferent’ means carrying towards a central organ or point e.g. brain or spinal cord.
Relays nerve impulses from receptors to the brain or spinal cord.
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Types of Neurons
2. Motor (Effector/Efferent) Neuron ‘Efferent’ means moving away
from a central organ or point e.g. brain/spinal cord.
Takes nerve impulses from the brain or spinal cord to the effectors which are muscles, glands and organs.
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Types of Neurons
3. Interneuron (relay neurone) ‘Inter’ means between.Relays nerve message from sensory
neuron to motor neuron. They are located within the brain and spinal cord.
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Relationship between neurons
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Relationship between neurons Sensory receptors receive stimuli and send that
“information” as an electrical message that we call a ‘nerve impulse’ along the fibre of afferent neurons to the spinal cord/brain, where the impulse can be registered and interpreted.
A response message is sent as another nerve impulse along efferent fibres to the effector.
Muscle movement, glandular secretion or sight, speech etc. occurs as a direct response to the stimuli.
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Sensory Neuron
Interneuron
Motor Neuron Sensory Neuron
Interneuron
Motor Neuron
Muscle Contracts
Synapse
Synapse
Synapse
Passage of a nerve impulse
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The Autonomic Nervous System The autonomic nervous system (ANS) is the
command network that the CNS uses to maintain the body's homeostasis.
It automatically regulates heartbeat and controls muscle contractions in the walls of blood vessels, digestive, urinary, and reproductive tracts.
It also carries messages that help stimulate glands to secrete tears, mucus, and digestive enzymes.
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Some organs controlled by the Autonomic Nervous system
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Summary
The brain is the control centre for our nervous system. It determines how our body works. The brain works out what the messages it receives are so we know what we are seeing, touching, hearing, smelling and tasting, and if something hurts, feels good or makes us happy.
The brain makes sure our heart keeps beating and our lungs and other organs/glands keep working without us having to think about it. Part of the brain makes our muscles work, so we move.
The biggest part of the brain makes us think, see, hear, feel and taste; other parts maintain balance, controls growth and influences development and also maintains homeostasis.
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References
Brain (2007). [Online], Available:www.kidcyber.com.au
http://www.enchantedlearning.com/subjects/anatomy/brain/Spine.shtml
http://www.childrensuniversity.manchester.ac.uk/interactives/science/brainandsenses/brain.asp
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