Organisation Of The Nervous System

Front 1

What does the nervous system consist of?

Back 1

Sensory neurones, relay neurones, motor neurons and the spinal chord

Front 2

Where are relay neurones found?

Back 2

The brain

Front 3

What makes up the central nervous system?

Back 3

Neurones found in the brain and spinal chord

Front 4

What are motor and sensory neurones found in?

Back 4

The peripheral nervous system

Front 5

What is the autonomic nervous system made up of?

Back 5

Motor neurones which carry impulses to the involuntary muscles

Front 6

What are the involuntary muscles?

Back 6

Those which we generally have no conscious control over e.g iris of the eye and cardiac muscle

Front 7

What are the 2 branches of autonomic muscles?

Back 7

The sympathetic and the parasympathetic

Front 8

What can these 2 branches be described as?

Back 8

Antagonistic as they work in opposition to each other

Front 9

What happens to impulses under normal circumstances?

Back 9

Impulses travel along both branches simultaneously at a low rate

Front 10

What happens to these impulses under stress?

Back 10

The rate of the impulses increases in the sympathetic branch

Front 11

What happens to these impulses during relaxation?

Back 11

The rate of impulses is higher in the parasympathetic branch

Front 12

What is the reflex arc?

Back 12

A rapid, involuntary and short lived response to a stimulus

Front 13

What are these simple reflexes?

Back 13

They're protective and help the organism avoid danger. They're present from birth and don't need to be learnt

Front 14

What does the CNS receive sensory information from?

Back 14

A variety of receptors

Front 15

What is the function of these receptors?

Back 15

Sensory reception. They each respond to a different and specific type of stimulus

Front 16

What is sensory perception?

Back 16

This involves making sense of the information form the receptors

Front 17

What is the role of a transducer?

Back 17

To convert the change in form of energy by the stimulus into another form

Front 18

What do receptors in the nervous system do?

Back 18

They convert the energy of the stimulus into electrical energy used by neurones

Front 19

What is the resting potential?

Back 19

When a receptor hasn't been stimulated, it's in its resting state. There's a difference in charge between the inside and outside of the cell. The inside is more negatively charged so there's a voltage across the membrane. Potential difference at rest is called the resting potential

Front 20

What is the generator potential?

Back 20

When a stimulus is detected, the cell membrane is excited and becomes more permeable, allowing more ions to move in and out of the cell. This alters the potential difference and this change is called the generator potential

Front 21

What is the action potential?

Back 21

If the generator potential is big enough (reches the threshold value) it will trigger an action potential-an electrical impulse along a neurone

Front 22

What does the pacinian corpuscle do?

Back 22

It responds to mechanical pressure

Front 23

Where are pacinian corpuscles found?

Back 23

Deep in the skin, they're most abundant on the fingers and soles of the feet

Front 24

Where do they also occur and what do they do here?

Back 24

In joints, ligaments and tendons. They enable the organism to know which joints are changing direction

Front 25

What is the structure of a pacinian corpuscle?

Back 25

A single sensory neurone is at the centre of layers of tissue, each separated by a gel. This gives the appearance of an onion when cut vertically.

Front 26

What is special about the sensory neurone in a pacinian corpuscle?

Back 26

It has a special type of sodium channel in its plasma membrane (stretch mediated sodium channel). These change the permeability of sodium ions when they're deformed

Front 27

How does the stretch mediated sodium channel work?

Back 27

At rest, the channels are too narrow for sodium ions to pass through. When pressure is applied, the pacinian corpuscle is deformed, stretching the membrane around the neurone. This widens the channels and allows sodium ions to diffuse into the neurone. This influx changes the potential and depolarises the membrane producing a generator potential which creates an action potential.

Front 28

Where are photoreceptors found?

Back 28

On the retina of the eye

Front 29

What are the 2 types of photoreceptors?

Back 29

Rods and cones

Front 30

What do both types do?

Back 30

Act as transducers, converting light energy into electrical energy.

Front 31

What can rod cells not do?

Back 31

Distinguish between different wavelengths, so image in black and white

Front 32

What do they connect to?

Back 32

Many rods are connected to a single neurone in the optic nerve.

Front 33

What happens when a threshold value is acheveid?

Back 33

When this value is reached, a generator potential is created in the bipolar cells to which they are connected

Front 34

What is it called when a number of rod cells are connected to a single bipolar cell?

Back 34

Retinal convergence

Front 35

What does this retinal convergence mean?

Back 35

There's a much greater chance that the threshold value will be exceeded than if only a single rod were connected to each bipolar cell. (summation)

Front 36

What does this allow us to do?

Back 36

See in low light intensities

Front 37

What must happen in order to create a generator potential?

Back 37

The pigment in the rod cell (rhodopsin) must be broken down. There's enough energy from low light intensity light to do this

Front 38

What is a consequence of many rod cells lining to one bipolar cell?

Back 38

The light received by rod cells sharing the same neurone will only generate a single impulse travelling to the brain.

Front 39

What does this mean?

Back 39

In perception, the brain can't distinguish between the separate sources of light that stimulated them. 2 dots close together can't be resolved, so appear as a single blob

Front 40

What does this mean about the rod cell?

Back 40

They give low visual acuity (the ability to tell apart points that are close together)

Front 41

How many types of cone cells are there?

Back 41

3 and they each respond to a different wavelength of light.

Front 42

What do cone cells often have?

Back 42

Their own separate bipolar cell connected to a sensory neurone in the optic nerve.

Front 43

What does this mean?

Back 43

The stimulation of a number of cone cells can't be combined to help exceed the threshold value to create a generator potential. This means they only respond to high light intensity

Front 44

What pigment do cone cells contain and what does it require?

Back 44

Iodopsin which requires requires high light intensity to break it down.

Front 45

How do the 3 different types of cone cells differ?

Back 45

They have a different type of iodopsin, which results in them being sensitive to a different range of wavelengths

Front 46

How do cone cells differ from rod cells?

Back 46

They have good visual acuity as each cell has its own connection to a single bipolar cell.