OCR A-level Biology - Neuronal communication

What is a neurone

A specialised nerve cell that transmits electrical impulses around the body

What is the role of the cell body

It contains the nucleus and genetic material allowing the cell to function and it’s the site of neurotransmitter production

What is the structure and function of the dendrons

they are extensions of the cell body which divide into dendrites and transmit electrical impulses towards the cell body

What is the structure and function of axons

Nerve fibres which transmit electrical impulses away from the cell body towards the axon terminals

What is the role of a sensory neuron

To transmit electrical impulses from sensory receptors to relay neurons/CNS

What is the role of a motor neurone

To transmit electrical impulses from relay neurons in the CNS to effectors (muscles/glands)

What is the role of a relay neurone

To transmit electrical impulses between sensory and motor neurones

Where is the cell body located in a sensory neurone

Between the dendrites

Where is the cell body located in a motor neurone

Between the dendron and the axon

What is the structure of a relay neurone

An intermediate neurone with very short axons and dendrites

What is the sequence of a reflex arc

Stimuli, receptor, sensory neurone, relay neurone, motor neurone, effector and response

What is myelin sheathing composed of

Phospholipid bilayers

Where are layers of myelin sheaths produced

Schwann cells

What are the gaps between myelin sheaths called

Nodes of Ranvier

What is it called when the impulse jumps between nodes of ranvier

Saltatory conduction

why are some neurones covered in myelin sheath

It speeds up the rate of neuron transmission and allows saltatory conduction

How does cell signalling occur

A cell releases a chemical which acts on a target cell

What is an example of local cell signalling

Cell signalling between synapses

What is an example of cell signalling travelling across large distances

Using hormones

What is homeostasis

Maintaining a relatively constant internal environment

What is an example of external environmental changes

Temperature/humidity/light intensity

What is an example of internal environmental changes

Blood glucose concentration/water potential/temperature/cell pH

What occurs in people who have multiple sclerosis

An autoimmune response causes the myelin sheath to thin/break down leading to the breakdown of the axon, affecting the speed of neuronal transmission

What is a mechanoreceptor

A sensory receptor sensitive to pressure and movement

What is a chemoreceptor

A sensory receptor sensitive to chemicals

What is a thermoreceptor

A sensory receptor sensitive to temperature/heat

What is a photoreceptor

A sensory receptor sensitive to light

What is an example of a key mechanoreceptor

The Pacinian corpuscle

What is a transducer

Generator potentials that convert stimuli to electrical impulses

What occurs in the Pacinian corpuscle at normal resting state

The stretch mediated sodium ion channels are closed/maintaining resting potential/the concentration of sodium ions is higher outside the neurone

What occurs in the Pacinian Corpuscle when pressure is applied

The neurone membrane stretches as the corpuscle changes shape leading to the stretch mediated sodium ion channels to open

What happens when the stretch mediated sodium ion channels in the Pacinian corpuscle open

The sodium ions diffuse into the sensory neurone through the stretch mediated ion channels along the electrochemical gradient causing the membrane to become depolarised generating an action potential along the sensory neurone

Where are Parcinian corpuscle cells commonly found

In the fingertips/skin/joints/feet