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46 Cards in this Set

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What does the nervous system consist of?

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

Where are relay neurones found?

The brain

What makes up the central nervous system?

Neurones found in the brain and spinal chord

What are motor and sensory neurones found in?

The peripheral nervous system

What is the autonomic nervous system made up of?

Motor neurones which carry impulses to the involuntary muscles

What are the involuntary muscles?

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

What are the 2 branches of autonomic muscles?

The sympathetic and the parasympathetic

What can these 2 branches be described as?

Antagonistic as they work in opposition to each other

What happens to impulses under normal circumstances?

Impulses travel along both branches simultaneously at a low rate

What happens to these impulses under stress?

The rate of the impulses increases in the sympathetic branch

What happens to these impulses during relaxation?

The rate of impulses is higher in the parasympathetic branch

What is the reflex arc?

A rapid, involuntary and short lived response to a stimulus

What are these simple reflexes?

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

What does the CNS receive sensory information from?

A variety of receptors

What is the function of these receptors?

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

What is sensory perception?

This involves making sense of the information form the receptors

What is the role of a transducer?

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

What do receptors in the nervous system do?

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

What is the resting potential?

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

What is the generator potential?

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

What is the action potential?

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

What does the pacinian corpuscle do?

It responds to mechanical pressure

Where are pacinian corpuscles found?

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

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

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

What is the structure of a pacinian corpuscle?

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.

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

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

How does the stretch mediated sodium channel work?

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.

Where are photoreceptors found?

On the retina of the eye

What are the 2 types of photoreceptors?

Rods and cones

What do both types do?

Act as transducers, converting light energy into electrical energy.

What can rod cells not do?

Distinguish between different wavelengths, so image in black and white

What do they connect to?

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

What happens when a threshold value is acheveid?

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

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

Retinal convergence

What does this retinal convergence mean?

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)

What does this allow us to do?

See in low light intensities

What must happen in order to create a generator potential?

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

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

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

What does this mean?

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

What does this mean about the rod cell?

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

How many types of cone cells are there?

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

What do cone cells often have?

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

What does this mean?

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

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

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

How do the 3 different types of cone cells differ?

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

How do cone cells differ from rod cells?

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