B13 Nervous system and homeostasis Flashcards
Function of the nervous system
Enables humans to react to their surroundings and to coordinate their behaviour
Voluntary and involuntary reactions
Structure of the nervous system
CNS and Network of Nerves
What comprises the CNS?
(Central Nervous System)
Brain and spinal cord
How does the nervous system respond to stimuli?
Stimulus is detected by receptors
Information from receptors is passed along neurones to the CNS as electrical impulses
Coordinator- CNS coordinates the body’s response to the stimulus
Effector brings about a response via glands secreting hormones or muscles contracting
Body responds to the stimuluse
What are reflex actions?
Responses that do not involve the conscious part of the brain.
Give the pathway of a nervous response
Stimulus -> Receptor -> Coordinator -> Effector -> Response
Why are reflex actions important?
For survival to prevent damage to the body
What are neurones?
They carry electrical impulses around the body
Relay neurones connect sensory neurones to motor neurones
What are synapses?
Gaps between neurones, which allow electrical impulses in the nervous system to cross between neurones
How does a synapse work?
Impulse arrives at neurone
Chemicals are released in to the gap between the neurone
Chemicals attach to the next surface of the next neurone and set up to a new electrical impulse
Cerebral cortex
Outer layer of the brain
Important for consciousness, intelligence memory and language
Cerebellum
At the back of the brain
Coordinates muscle activity
Medulla oblongata
Above the spinal cord
Controls unconscious activities such as breathing and heart beating
Hypothalamus
The hypothalamus in the brain contains the temperature monitoring centre for the body.
Pituitary gland
The pituitary gland releases hormones in response to changes detected by the hypothalamus.
Why is it difficult to treat brain disorders?
Brain is very complex and delicate
What is homeostasis?
Maintenance of a constant internal environment
3 internal conditions controlled by homeostasis
Body Temp
Blood glucose concentration
Water levels
3 things all control centres include
Receptors
Coordination centres
Effectors
Cornea
lets light in and changes directions so light is focused on the retina
iris
coloured part of eye
contains muscles that contract to change the size of pupil
lets more/less light in
ciliary muscle
contracts and relaxes to change shape of lens
retina
layer of receptors at the back of the eye
rods and cones
optic nerve
nerve that connects eye to brain
lens
sits behind pupil and focuses light on retina
how do eyes focus on a NEAR object
ciliary muscles contract
so lens becomes thicker
and more curved
and refracts light rays more strongly
how do eyes focus on a DISTANT object
ciliary muscles relax
so lens is thinner and flatter and only refracts light rays partially
myopia
short sightedness
Q
what type of lens is used to aid myopia
concave lens
hyperopia
long sightedness
what type of lens is used to aid hyperopia
convex lens
How can eye defects be treated?
-spectacle lenses
-contact lenses
-laser surgery
-replacement lenses in the eye
What is accommodation
The process of changing the shape of the lens to focus on objects
What part of the brain controls body temperature
hypothalamus
What happens if body temperature is too high?
Vasodilation
Sweat is produced
Hair on body lies flat
What happens when body temperature is too low?
Vasoconstriction
Sweating stops
Shivering
Hair on body stands up
