the conditions in your body need to be kept steady even when the external environment changes
Homeostasis is the regulation of the conditions inside your body to maintain a stable environment
you have lots of automatic control systems in your body that regulate your internal environment, this includes both hormonal and nervous communication systems
there are control systems that maintain your body temperature, bloody glucose level, and your water content
what does the central nervous system consist of?
brain and spinal cord
what are the sensory neurones?
the neurones that carry information and electrical impulses from the receptors to the Central nervous system
what are the motor neurones?
the neurones that carry information as electrical impulses from the central nervous system to effectors
what are the effectors?
all your muscles and glands which respond to nervous impulses
receptors are the cells that detect stimuli
effectors respond to nervous impulses and bring about a change
the central nervous system is a coordination centre - it receives information from the receptors and then coordinates a response which is then carried out by the effectors
the connection between two neurons is called a synapses
at the synapses the nerve signal is transferred by chemicals which diffuse across the gap and set off a new electrical signal in the next neuron
reflexes are rapid, automatic responses to certain stimuli that don't involve the conscious part is the brain
the passage of information in a reflex is called a reflex arc
stimualtion
impulse travels along the sensory neurone
impulsesare passed along a relay neurone
impulses travel along a motor neurone
impulses reach a muscle, it contracts
label the brain:
A) cerebellum
B) medulla
C) spinal cord
D) cerebral cortex
E) hypothalamus
F) pituitary gland
what does the cerebral cortex do?
it is responsible for consciousness, intelligence, memory and language
what does the medulla do?
controls unconscious activities like breathing and your heartbeat
what does the cerebellum do?
it is responsible for muscle coordination
electrical stimulation of the brain can help reduce muscle tremors caused by nervous system disorders such as Parkinson's disease
label the eye:
A) suspensory ligament
B) iris
C) pupil
D) conjuctiva
E) cornea
F) ciliary muscle
G) lens
H) retina
I) optic nerve
J) fovea
what does the sclera do?
it is the tough, supporting wall of the eye
what does the cornea do?
it is the transparent outer layer found at the front of the eye, it refracts light into the eye
what does the iris do?
it contains muscles that allow it to control the diameter of the pupil and therefore how much light enters the eye
what does the lens do?
it focuses the light onto the retina
what do the ciliary muscles and suspensory ligaments do?
they control the shape of the lens
what does the optic nerve do?
it carries impulses from the receptors on the retina to the brain
what happens to the eye when bright light is detected?
the circular muscles in the iris contract and the radial muscles relax, making the pupil wider
what happens to the eye in dim light?
the radial muscles contract and the circular muscles relax making the pupil wider
what happens to the eye to look at a near object?
the ciliary muscles contract, which slackens the suspensory ligaments
the lens becomes fat (more curved)
this increases the amount by which it refracts light
what happens to the eye to look at far objects?
the ciliary muscles relax, which allows the suspensory ligaments to pull tight
this makes the lens go thin (less curved)
so it refracts light by a smaller amount
why does long sightedness occur?
it occurs when the lens is the wrong shape and doesn't refract the light enough or the eyeball is too short. The images of near objects are brought into focus behind the retina.
how do you fix long sightedness?
you can use glasses with a convex lens which refracts the light rays so they focus on the retina
why does short sightedness occur?
it occurs when the lens is the wrong shape and refracts the light too much or the eyeball is too long. The images of distant objects are brought into focus in front of the retina
how do you fix short sightedness?
you can use glasses with a concave lens which curves light inwards to allows light rays to focus on the retina
what do they do during laser eye surgery?
it vaporises tissue, changing the shape of the cornea
what are the treatments of for vision defects?
contact lenses, laser eye surgery, replacement lens surgery
there is a thermoregulatory centre in the brain, which contains receptors that are sensitive to the temperature of the blood flowing through the brain
what is vasodilation?
where the blood vessels supplying the skin dilate so more blood flows close to the surface of the skin allowing energy to transfer from the skin to environment