The Human Nervous System Flashcards by serena shah

How do cells carry out respiration to release energy from glucose?

they use enzymes

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what do enzymes and cells require in order to work?

very stable conditions

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enzymes cant work well if…

the conditions around them change too much

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homeostatis definition?

the maintenance of a constant internal environment

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what three things does your body maintain?

your blood glucose concentration
body temp
water balance

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Explain the three stages of the automatic control system..

-receptor cells detect the changes in the environment
- the receptor cells pass information to a coordination centre
- the coordination centre receives and processes the information from the receptor cells
-the coordination centre now sends instructions to the effector
the job of the effector is to carry out the response or restore the optimum level

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what do scientists call a change in the environment?

a stimulus

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what is the job of the effector?

to carry out the response or restore the optimum level

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What are the two parts of the nervous system?

Central nervous system

- other nerves going to or from the nervous system

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Explain the automatic control centre in TERMS OF NEURONES

Receptors detect a stimulus and send electrical impulses down neurones to the central nervous system
The CNS is the coordination centre. This now sends electrical impulses down other neurones to effectors and the effectors being about a response

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What are effectors usually? (2 things)

A muscle that contracts

- a gland that secretes a hormone

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What are the two key roles of the nervous system?

enables humans to react to their surroundings

- coordinates their behaviour

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What is one way that shows how humans react to their surroundings?

The Reflex Arc

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Explain the reflex arc in terms of neurones when you touch a hot object..

-The stimulus is detected by a receptor
-Electrical impulses now pass from the receptor along a sensory neurone to the CNS.
at the end of the sensory neurone is a synapse a chemical is released there which diffuses across to a relay neurone and reaches another synapse
once again a chemical is released
the chemical triggers an electrical impulse in the motor neurone
the electrical impulse now passes down the motor neurone to an effector in this case a muscle
the muscle now contracts and pulls the hand away from the heat
pulling the hand away is a response

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What is a stimulus?

something in the environment

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What is a receptor?

something you use to touch it

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What is at the end of a sensory neurone?

and what happens there?

A synapse

a chemical is released

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just give the stages for the reflex arc..

stimulus 
receptor
sensory neurone
synapse
relay neurone
synapse
motor neurone
effector
response

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Why are reflexes automatic and rapid?

There is no decision making from the conscious part of the brain

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In the reaction time practical what are the..
independent
dependent and control variables?

independent- person being tested
dependent- reaction time
control- starting distance between thumb and 1st finger

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Explain the Reaction Time Practical..

X measures the reaction time of Y
Y sits on a stool with upright posture
Y then places their forearm of their dominant arm across the table with their hand overhanging the edge
X holds the ruler vertically
The 0cm mark should be between Y’s first and thumb finger
X tells Y to prepare to catch the ruler with their thumb and first finger as quickly as possible when it drops
X records the measurement on the ruler that is in level with the top of Y’s thumb
this is repeated several times to calculate a mean

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What are two other tests using reaction time?

if caffeine affects reaction time

- non dominant hand vs dominant

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What organ system is the brain part of?

The CNS

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What does the brain control and how does it do this?

controls the complex behaviour

by containing billions of interconnected neurones

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What is the top section of the brain called (the wormy one)

celebral cortex

What are the celebral cortex's functions?

language memory consciousness

what is the bottom back part of the brain called (the shell one)

cerebellum

What are the functions of the cerebellum?

controls our balance | coordinates our movement

what is the small section in the centre part of your brain above the spinal cord called?

the medulla

what are the functions of the medulla?

controls our heart rate and our breathing rate

what is the brain protected by?

the skull

what two words describe the brain?

extremely delicate and easy to damage

What are the three ways that scientists use to investigate the brain?

- by looking at patients with brain damage, they can see what part of the brain links to what function - electrically stimulate diff parts of the brain and look at the effects on the persons behaviour - use MRI scanning to look at which part of the brain are most active during different activities

What type of organ is the eye?

sense organ

what does the eye contain and what are they sensitive to?

receptors sensitive to both light intensity and also the colour of light

Explain how light rays pass through the eye..

Light rays pass through the transparent front of the eye-cornea light rays then pass the pupil in the centre of the iris they then pass through the lens the light rays are now focussed to the back of the eye the retina the receptor cells now help us send electrical impulses down the optic nerve to the brain the ciliary muscles and the suspensory ligaments work with the lens

what is the job of the cornea?

to start the focussing of the light rays

What is the iris?

the coloured part of the eye

what is the job of the lens?

to focus the light rays onto the back of the eye

what is the key feature of the lens?

it can change its shape allowing us to focus on distant or near objects

what does the retina contain and what do they help us to do?

receptor cells for light | they help us detect the light intensity and light colour

what is the white part of the eye called? | and what does it do?

sclera | this tough outer structure protects the eye

what do the ciliary muscles and suspensory ligaments allow us to do TOGETHER?

focus on distant or near objects

What is the pupil?

The space in the centre of the iris that light passes through

What does the pupil allow?

light to pass into the eye

What is the job of the iris?

To control the size of the pupil

What happens when you enter a dark room?

the amount of light entering the eye is now low this drop in light intensity is detected by the light receptors in the retina these send electrical impulses to the brain the brain then sends electrical impulses to specific muscles in the iris these muscles contract causing the pupil the become larger allowing more light to enter the eye

What happens when you enter a light room?

the reflex causes the pupil to become smaller | this reduces the amount of light entering your eye and protects it from damage

How does the eye focus?

A lot of the focusing is carried out by the cornea but this is fixed focus the rest is carried out by the lens the lens allows us to focus on near and distant objects to do this the shape of the lens can change

what is accomodation?

the ability to change the shape of the lens and focus on near or distant objects

what is the lens surrounded by and what is that then surrounded by?

the lens is surrounded by suspensory ligaments and they are surrounded by ciliary muscle

how is the ciliary muscle connected to the lens?

by fibres of suspensory ligaments

How do you change the thickness of the lens?

by contracting and relaxing

when the ciliary muscle contracts and the suspensory ligaments loosens what happens?

the lens thickens and refracts light rays more strongly

when the ciliary muscle relaxes and the suspensory ligaments tightens what happens?

the lens is now pulled thin and only slightly refracts light rays

how much does light from distant objects need to be focused on?

only a relatively small amount

What happens when you focus on distant objects?

the ciliary muscle relaxes and the suspensory ligaments are pulled tight the lens is now pulled thin because the lens is thin the light rays are only slightly refracted the light rays now focused to a point on the retina

What happens when you focus on near objects?

the ciliary muscle contracts and the suspensory ligaments loosens the lens is now thickens and refract light rays more strongly the light rays now focused to a point on the retina

how much does light from near objects need to be focused on?

a large amount

What is hyperopia?

long sighted

what is the problem with long sight?

cannot focus on near objects

What happens to the eyeball in long sighted people and the light entering the eye?

the eyeball is too short so the light is focussed at a point behind the retina

How can long sight appear in elderly?

the lens can become less elastic and cannot become thick enough to focus on near objects

How can long sight be treated? | how does this method help?

using glasses with convex lenses | these partially focus the light before entering the eye

What is myopia?

short sighted

what is the problem with short sight?

cannot focus on distant objects

What happens to the eyeball in short sighted people and the light entering the eye?

the eyeball is too long so the light is focussed at a point in front of the retina

how else can short sight appear?

when the lens is too thick

how can short sight be treated? | how does this method help?

wear concave lenses | to partially un focus the light before it enters the eye

What can people use instead of glasses? | and how do they help?

hard or soft lenses | they sit on the eyeball and refract the light in the same way as glasses

How does laser eye surgery work?

it changes the shape of the cornea | so it refracts the light to a greater or less extent

how else can the lens in the eye be replaced?

using an artificial lens