3.8 Parts of the nervous system

For labelling and short questions

What does the central nervous system (CNS) consist of?

The brain and the spinal cord

What does the peripheral nervous system (PNS) comprise of?

Comprises of the somatic nervous system (pairs of nerves that originate in the brain or spinal cord) and the autonomic nervous system

What are reflex arcs?

The neural pathway taken by the nervous impulses of a reflex action, they are rapid and automatic

What is a stimulus?

A detectable change in the internal or external environment of an organism which produces a response

What are neurones/ nerve cells?

Specialised cells adapted to rapidly carry nervous impulses from one part of the body to the other

What is the role of sensory neurons?

They carry impulses from the sense receptors or organs into the CNS (Afferent)

What is the role of interneurons?

They receive the impulses from the sensory neurones or other relay neurones and transmit them to motor neurones or other relay nuerones(Relay)

What is the role of motor neurons?

They carry impulses from the CNS to the effector organs e.g glands or muscles (Efferent)

What is a nervous impulse?

The transmission of a change in potential along a nerve fibre associated with the movement of sodium ions

What’s the role of grey matter?

It enables individuals to control movement, memory and emotions

What’s the role of white matter?

It’s essential for impulse conduction

What’s the role of the dorsal root?

It transmits sensory information, forming the afferent sensory root of a spinal nerve

What’s the function of the dorsal root ganglion?

It relays the sensory nerve impulses from the periphery to the peripheral nervous system

What’s the role of the ventral roots?

They allow motor neurons to exit the spinal cord

What’s the role of meninges?

They are three membranes that protect the brain and spinal cord

What’s the role of the central canal?

It transports cerebrospinal fluid which, when the spine is injured it helps transfer nutrients to the spinal cord and softens the effect of a force

What is the function of the cell body?

Contains a nucleus and granular cytoplasm

What’s the function of the nucleus?

Holds the cells DNA

What are Nissl granules?

Cytoplasmic granules comprising ribosomes grouped on RER

What is the function of the dendrites?

Thin fibres carrying impulses towards the cell body (the cell body is likely to have many)

What is the function of the axon?

Thin nerve fibre carrying impulses away from the cell body (only one)

What is the function of the axon ending?

It secretes neurotransmitter, which transmits impulse to adjacent neurone

Describe the structure of an axon

It’s highly thin, thinner than dendrites and longer too

What are myelinated axons?

These are axons surrounded by a many-layered lipid and protein covering called the myelin sheath, which is formed by the Schwann cells

What is the myelin sheath?

Electrical insulator that speeds up the transmission of impulses

What are Schwann cells?

They are lipids which surround and support nerve fibres, the cell plasma membrane becomes extended to from them

Describe a feature of Schwann cells

As it’s lipid it prevents the movement of Na+ and K+ ions into/out of the nerve fibre

What are the nodes of ranvier?

They are gaps found within the myelinated axons, they speed up the movement of action potentials via saltatory conduction

What is the synaptic end bulb and what is it’s role?

It’s the swelling at the end of an axon in which neurotransmitter is synthesised