Nerves and Hormones (6) Flashcards
Much of the knowledge gained about the nervous system and hormones shows some general principles about scientific research:
- it is often developed in stages using different lines of evidence
- it involves collaboration among different scientists
- it is validated by peer review, the process where other scientists of equivalent status review and comment on new research
What happens when
- someone shines a bright light in your face?
- you place your hand on something hot?
- you step on a drawing pin?
What causes this?
- Close your eyes
- Pull hand away
- jump back
- when there is a change in your environment it is called a stimulus (plural-stimuli)
- Our reactions to these stimuli are called responses
How does our body detect these changes in the environment?
Our bodies have many types of special cells called receptors, each responding to a particular type of stimulus or sense. Receptors are often found in the sense organs.
Name each sense and it’s particular sense organ
Sense - Sense Organ smell - nose taste - tongue sound - ear touch - skin sight - eyes
Explain what a receptor might cause and why?
If a receptor is stimulated by a change in the environment it may cause an effector (such as a muscle or a hormone-producing gland) to produce a response.
What is a coordinator?
This system of responding to the environment requires a coordinator to link between the receptor and the effector.
In complex animals such as humans the co-ordinator i either the brain or the spinal cord. Together these two structures make up the central nervous system (CNS).
How is co-ordination achieved?
Stimulus - this is any change inside or outside our bodies which causes a change in behaviour e.g a sound, sight, smell, pain or a touch.
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Receptors - sense cells which detect stimuli e.g pain receptors in the skin and the major sense organs; ears, eyes, tongue and nose.
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Co-ordinators - these are organs which receive information from receptors and use it to coordinate behaviour. The brain and spinal cord are coordinators.
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Effectors - these are the parts of the body which are controlled by the co-ordinators i.e. the muscles and the glands.
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Response - the behaviour resulting from the original stimulus
explain the stages of coordination and give an example of coordination.
Stimulus - receptor - brain - effector (muscle) - response
Jane texts John - John’s eye reads the text - John thinks what to do - John types a reply - John texts Jane
school bell - ears - brain - muscles in arms and legs - pack up and leave
state if the following is a receptor. coordinator, effector or response
- brain
- muscle
- burning toast
- walking to class
- salty food
- school bell
- drink water
- spinal cord
- sound receptor in ear
- standing on a nail
- coordinator
- effector
- stimulus
- response
- stimulus
- stimulus
- response
- coordinator
- receptor
- stimulus
What links the receptors to the coordinator?
Nerve cells or neurons link the receptors to the coordinator. A neuron carries information in the for of small electrical charges called nerve impulses.
label the diagram of the neuron
- dendrite (like branches)
- cell body ( around nucleus)
- nucleus
- axon ( cylinders inside tail)
- Myelin sheath (each section of tail)
What are voluntary actions? Give examples
Most of our responses are voluntary - this means we deliberately choose to do them and they involve conscious thoughts (thinking time)
e.g lifting a book, throwing a ball or opening a door
What are reflex actions? Give examples.
these do no involve conscious thought, they happen automatically and always occur in the same way and they occur very rapidly.
Such responses are beneficial as they tend to have protective roles and avoid causing unnecessary damage to the body.
e.g. cough, blink or moving hand away when touching something hot.
differences between voluntary and reflexive actions.
Voluntary Action
conscious control - yes
speed of response - slower
Reflex Action
conscious control - no
speed of response - rapid
What makes a reflexive action so rapid?
- the nerve pathway is very short e.g. the knee jerk reflex travels from the knee up to the base of the spinal cord and back into the leg.
- there are relatively few gaps between the neurons (synapses) - these are the places were impulses travel relatively slow
The pathway involved in a reflex action is called a spinal reflex arc. this route only involves the spinal cord not the brain.
What are the three types of neurones involved in a reflex action:
sensory nerve - connects receptor to the co-ordinator (spinal cord)
Association (connector) neurone - Joins the sensory and motor neurones
Motor neurone - connects co-ordinator (spinal cord) to the effector
diagram of a reflex arc
Motor neurone - carries info from spinal cord back to muscle/effector causing response
association/connector - neuron joins sensory and motor neurone
sensory neuron - carries info from receptors to spinal cord
When your hand touches a sharp object what happens/ (REFLEX)
- Pressure receptors stimulated in skin
- nerve impulse travels along sensory neuron to spinal cord
- info is passed along association neuron
- nerve impulse then travels long motor neurone to effector/muscle
- when nerve impulse reaches muscle in the hand it contractsand hand is lifted away from sharp object ie there is a response
draw word diagram of reflex arc
stimulus –> receptor – sensory neurone –> association neurone (in spinal cord) – motor neurone —. effector –> response
explain synopses and what they do.
Neurones do not make direct contact with each other.
There are small gaps called synapses between adjacent neurones - these act as junctions.
Transmission across synapses is caused by the diffusion of transmitter chemicals across the junction. The transmiter chemical is produced by the end of the neurone leading into the synapse and if produced in high enough concentration will trigger an impulse in the next neurone. While synapses may slow transmission they allow a greater degree of control at these junction points.
How are neurones specialised for their function?
- being very long
- having branched ends that allow them to transmit impulses over a greater area to make more connections with other neurones.
- having an insulating sheath that surrounds them to help them to speed up transmission of an impulse.
Label diagram of the eye.
From the top to bottom left side
- ciliary muscle
- conjunctiva
- cornea
- Aqueous humor
- pupil
- lens
- iris
- suspensory ligaments
from the right top to bottom
- vitreous humor
- retina
- optic nerve
Name the function for each of these structures
- conjunctiva
- cornea
- Iris
- Pupil
- Lens
- Ciliary muscle
- Suspensory ligaments
- Retina
- Optic nerve
- Aqueous humour
- Vitreous humour
- Conjunctiva - thin transparent protective outer cover
- Cornea - Transparent front part of eye, allows light to enter.
- Iris - Controls how much light enters the eye
- Pupil - space in iris which light passes
- Lens - refracts (bends) light
- Ciliary muscle - ring of muscle that surrounds lens, changes shape of lens
- Suspensory ligaments - attach lens to ciliary muscle, changes shape of lens
- Retina - inner coat of eye where light sensitive cells are found
- Optic nerve - contains neurones carrying info to brain
- Aqueous humour - watery fluid between cornea and lens. Keeps pressure right and allows light to pass through.
- Vitreous humour - jelly-like fluid between lens and retina. Keeps eye spherical and allows light to pass through
What is accommodation?
For a focuses image to be seen, the light rays entering the eye must be focused on the retina - the part of the eye where the light sensitive cells are found. In order to do this the light rays must be bent (refracted). Accommodation refers to how the shape of the lens is changed in order to focus the light rays on the retina.
