Nervous Tissue (5) Flashcards
(27 cards)
What does nervous tissue consist of?
It consists of neurons and neuroglia.
What is the nervous system consist of?
The nervous system is made up of many millions of special cells called neurons that form a continuous network, extending all over the body. They form the structural units of the nervous system.
What do neurons need to function for a life time?
The correct conditions.
Neurons cannot undergo ___, so they cannot be ___ if replaced. Stem cells may be used to replace ____ neurons.
Mitosis
Replaced
Damaged
Why can neurons not survive for more than a few minutes without oxygen?
Neurons have a very high metabolic rate and need continuous supplies of oxygen and glucose to survive.
What do glial cells do?
They are supporting cells which play a critical role in making myelin and supporting and protecting the neurons.
What is the structure of neuron? (4)
Neurons are made up of the same basic parts as other animals. Membrane Cytoplasm Cell organelles Nucleus
What additional structure do neurons have and how are these useful?
They have long, thin processes-fibres of cytoplasm that extend from the cell body. These make it possible for nerve impulses to be carried long distances.
What are the two fibres in a typical neuron? (2)
- Dendrites
- Axons
What are dendrites?
Dendrites conduct impulses TOWARDS the cell body. They are short, tapering processes that branch extensively to provide a large surface area to receive signals from other neurons.
What are axons?
Axons conduct impulses AWAY from the cell body. Each neuron has a single axon although certain axons may give off branches along their length. An axon usually branches extensively at its end to form terminal breaches.
What are sensory/unipolar neurons?
These are afferent neurons as they carry impulses from receptors towards the CNS, where the sensation is interpreted.
Define unipolar.
One fibre attached to the cell body.
What are connector neurons?
These are multipolar neurons found in the CNS and make up 99% of the neurons of the body. They receive impulses from sensory neurons and pass them onto other neurons.
Define multipolar.
Many fibres attached to the cell body.
What are motor neurons?
These are efferent neurons as they carry impulses away from the CNS to effectors so that the appropriate response can be brought about.
Function of dendrite.
Collect information from other cells and pass it on to cell body.
Function of the cell body.
Controls the metabolism of cell.
Function of the node of Ranvier.
Allows rapid conduction of impulses by forcing them to jump from one node to the next.
Function of a Schwann cell.
Secretes the myelin sheath.
Function of the axon.
Extended to carry impulses away from the cell body over long distances.
Function of myelin sheath.
Forms electrical insulation around the axon preventing impulses being disrupted from activity in neighbouring cells.
Function of terminal branches.
Carry impulses to the synaptic knobs/ end plates.
Function of the synaptic knob.
Forms a synapse with another neuron, a muscle cell or gland cell.
