Chapter 7 Science Revision
Nerves and reflex actions:
Two main nervous systems, the central nervous system (CNS) and the peripheral nervous system (PNS)
The CNS is made up of the brain and spinal cord
The PNS is made up of the nerves which connect the CNS to other parts of the body
Nerves act as messengers inside the body carrying information from one part of the body to another
Nerves are made up of nerve cells (neurones)
Neurones or nerve cells carry electrical messages called nerve impulses
Motor neurones carry messages from the CNS to muscles or glands
Sensory neurones carry messages from the sense organs to the CNS
Receptors detect changes in the environment
Stimulus is anything that activates a receptor
Types of receptors: Mechanoreceptors- sensitive to touch stimulation, photoreceptors- sensitive to light stimulation in the eye, thermoreceptors- sensitive to changes in heat, chemoreceptors- sensitive to chemicals such as those found in food
Reflex actions are immediate reactions that happen very fast without warning from the brain. An impulse is sent from the pain receptor to the spinal cord and is acted upon immediately then a message is sent to the brain shortly after which registers pain.
When the electrical impulse gets to the end of the axon they release a chemical message called a neurotransmitter into the space between the next neurone, the dendrite of the next neurone then receives the chemical message
The Essay on Analyzing Messages
Composing, sending, and receiving productive, developed messages require a high level of awareness by the sender and receiver. Senders should be well-versed in the varying tones he or she may portray in reference to the point attempting to be made and receivers should remain open to feedback and maintain the ability to delineate between negative and positive messages. “No communication skill ...
The myelin sheath electrically insulates the fibres from one another and increases the speed of the impulse
Groups of receptors form sensory organs
Effectors are muscles and glands where the messages carried by the nerves end up and are carried out and put into “effect”
The parts of the CNS that contain nerve fibres covered in myelin are called white matter
The main part of the brain is grey matter which is mainly made up of cell bodies
Habituation is becoming so used to a stimulus that you stop responding to it. Eg. When you go in water and eventually your body stops feeling the cold
Nerve impulses travel through neurons.
Focus on two glands:
Ear:
The pinna directs sound through the auditory canal into eardrum which vibrates and sends vibrations to tiny bones in the middle of the ear, the vibrations move to the cochlea which set hair cells vibrating which convert the vibrations into impulses which then are sent through the auditory nerve to the brain
Eye:
Cones are responsible for colour vision in bright light
Rods are responsible for night vision in dim light
iris
pupil
lens
cornea
aqueous body
ciliary body
vitreous humour (gel)
sclera
optic nerve
blood vessels
fovea
retina
PART | FUNCTION |
Cornea | It protects the eye from harmful matter and from entering the pupil. It controls and focuses the entry of light into the eye. |
Iris | It regulates the amount of light that enters the eye by contracting and dilating. |
Pupil | The pupil is the hole that lets light enter the eye. |
Lens | It focuses light onto the back of the eyeball. |
Vitreous humour (gel) | It holds the shape of the eye together. |
Aqueous humour (water) | Fills the space between the lens and the cornea |
Optic nerve | Transfers visual information formed by the retina to the brain |
Retina | Receives the image seen through your eye and transmits it down the optic nerve |
Conjunctiva | Protects the eye by producing mucus or tears |
The Essay on The Eye Light Brain Eyes
How Do We See? Seeing involves more than opening our eyes. Through simple and fun experimentation the class will learn how the interaction of light, the eyes and the brain create the world we see. How Do We See? Our eyes are constantly feeding information to us. When we are born our eyes need time to get used to seeing and understanding what exactly it is that you are seeing. Given time and ...
Sclera | Is the white outer layer of the eye which protects it from diseases |
Ciliary Body | Contains muscles which change the shape of the lens |
Retinal blood vessels | |
Brain:
Cerebrum: Two main parts of the brain, in humans there are two cerebral hemispheres which are what the cerebrum is divided into (left and right sides of the brain)
Cerebellum: Is responsible for coordination and balance
Corpus Callosum: Links the two parts of the brain together
Brain Stem: Very important part of brain as it controls the body’s vital functions like breathing, blood pressure and heart rate
Chemical Messengers in Animals:
Hormones are chemical substances that act as messengers in our body, the travel straight through the blood stream to the “target organ”
They are produced by endocrine glands and are part of the endocrine system
Pituitary Gland: Is also known as the “master gland” as it controls the activities of other endocrine glands. It also produces its own hormones and controls our sleep cycles and patterns, body temperature, water balance and growth.
Adrenal Gland: Controls the production of adrenalin and gives it off in hard or bad situations.
Steroids: Synthetic form of the male sex hormone testosterone
Effects:
Male | Female |
Baldness | Facial hair |
Liver tumours | Deepened voice |
Development of breasts | Brest reduction |
Shrinking testes | Male-pattern baldness |
Chemical Messengers in Plants:
Plant responses are called tropisms, an example of this is when a plant grows towards light, this is called a phototropism and is caused by the hormone auxin. The growth of roots downwards in response to gravity is known as a positive geotropism.
Ethene causes ripening in mature fruits, ethene made in old leaves causes leaves to fall off
Abscisic acid made in old leaves causes leaves to fall off also causes dropping of fruits and flowers
Cytokinins made in young fruits are needed for growth, cause cell division
Gibberellin and Auxin combine and are produced in young leaves and buds and are involved in growth and promote the thickening of stems and roots
