Sensory Flashcards
What is the nervous system?
A highly specialised part of the body that coordinates action and controls body function.
What are three characteristics of the nervous system?
- irritability
- conduction
- integration
Describe irritability?
It responds to stimuli
Describe conduction?
Transmits via action potentials over long distances
Describe integration?
Can analyse and interpret information
Describe nervous tissue?
Composed of neurons (nerve cells) and glial cells (supporting cells)
A single nerve is composed of thousands of nerve axons
Describe a neuron?
- Composed of a cell body, including nucleus
- attached dendrites for receiving chemical signals from other neutrons
- Axon composed of nerve fibre and myelin sheath
- Axon terminal at bottom
What are the two divisions of the nervous system?
The Central Nervous System
The Peripheral Nervous System
What is the CNS?
The brain and spinal cord
What is the PNS?
The nervous system that extends out from the brain and spinal cord to the rest of the body
What are PNS nerves extending from the brain called?
Cranial Nerves
What are PNS nerves extending from the spinal cord called?
Spinal nerves
Any PNS nerve will contain two kinds of nerve axons that transmit from the PNS to the CNS, what are they?
Sensory or Afferent
and
Motor or Efferent
What are PNS Sensory/Afferent Axons?
Axons that transmit action potentials from the periphery of the body to the CNS
What are Motor of Efferent Axons?
Axons that transmit action potentials from the CNS to the body periphery
Describe the hierarchy of a nerve, top to bottom.
- neuron each with their own membrane called an endonuerium
- Several neurons together form a nerve fascicle
- The fasicle has a membrane called a perineurium
- Several Fascile’s together form a nerve
- Nerve has a membrane called a epineurium
- There are blood vessels running through the nerve to supply oxygen, nutrients & metabolism
For sensory neurones, more information is required such as?
Location and type of stimulus
In order to transmit this specialised information what do some sensory nerves have?
Specialised nerve endings that only respond to one type of input
Name some examples of specific sensory inputs that are analysed by the brain?
Sight, taste, smell, blood gas levels, limb position, blood pressure
Discuss the layout of sensory receptors in the skin.
There are various types of specialised nerve ending as well as nerve endings lodged at different depths within the skin.
Do all areas of skin have the same number of sensory receptors?
No, some more than others.
What are sensory nerve receptors connected to?
Sensory nerve fibres
What is the area of skin supplied by a single sensory neuron called?
A receptive field ( a receptive field may contains many receptors)
Describe the two prick test in relation to receptive fields.
If two stimulus are detected across two receptive fields. Two distinct stimulus will be detected. If two stimulus are detected but only across one receptive field, only one single stimulus will be detected.
What three things determine the ability to localise a stimulus?
- number of receptors
- sensitivity of receptors
- size and arrangement of receptive fields
Describe sensory adaptation.
Some stimuli are harmless though consistent and so nerve endings quieten down and diminish the number of AP’s. Pain nerve endings do not show sensory adaptation
