peripheral nervous system Flashcards
1
Q
- What is a dermatome?
- What is a myotome?
A
Area of skin that is supplied by a single spinal nerve
Group of muscles innervated by a single spinal nerve
2
Q
- How many pairs of cranial nerves are there?
- How many pairs of spinal nerves are there?
A
12
31
3
Q
- What can visceral efferent nerves be divided into?
- What do these types of nerves innervate?
A
Parasympathetic and sympathetic
Sympathetic efferent nerves innervate the viscera (organs) **and periphery** (vasculature and sweat glands) Parasympathetic efferent nerves innervate the viscera (organs) only
4
Q
- What is a ganglion?
- What is a nucleus?
- What is a plexus?
A
Collection of cell bodies outside the CNS
Collection of cell bodies inside the CNS Network of interconnecting nerve
5
Q
- Where do all afferent fibres have their cell bodies?
- Where do visceral efferent nerves synapse?
A
Spinal ganglia
peripheral ganglia
6
Q
- How are the peripheral nerves arranged?
A
Fasciculi (singular fasciculus) - bundles of neurons
3 layers of connective tissue: 1. Epineurium - external vascular layer 2. Perineurium - covers individual fascicles 3. Endoneurium - individual axons covered
7
Q
- How can you classify conduction velocity and axonal diameter of peripheral nerves?
A
Based on conduction velocity:
Use letters A,B and C - A is the fastest Based on axonal diameter (sensory only): Use Roman numerals I-IV; with I being the largest diameter
8
Q
- What 2 properties do the faster conducting peripheral nerves have?
A
Myelination
Larger diameter
9
Q
- What type of sensory receptors respond to external stimuli and give examples of these stimuli?
A
Exteroreceptors
Pain, temperature, touch and pressure
10
Q
- What types of sensory receptors respond to internal stimuli and give examples of these stimuli?
A
Proprioreceptors → Movement and joint position
Enteroreceptors → Movement through gut and blood pH
11
Q
- List other types of sensory receptors classified by their mode of detection and what they detect
A
- Chemoreceptor- Detector molecules which bind to receptor e.g. in olfactory bulb
- Photoreceptor- Detect light in retina
- Thermoreceptors- Detect temperature in skin
- Mechanoreceptors- Mechanical opening of ion channels; e.g. touch receptors in skin
- Nociceptors- Detect tissue damage → then interpreted as by NS as pain
12
Q
- Where are proprioreceptors found and what is detected at each of these locations?
A
- Muscle spindles- Small sensory organs in skeletal muscles that detect whether muscle has been stretched
Detect changes in muscle length- Golgi tendon organs- Detect changes in tension in tendons
- Joint receptors- Found in joint capsules and detects start and end of movement (give you a sense of where your body is in space)
13
Q
- What is a neuromuscular junction?
- What is a motor unit?
A
Specialised synapse between a motor neurone and a muscle fibre
Single motor neurone together with all the muscle fibres that it innervates It is the smallest functional unit with which to produce a force
14
Q
- How many motor neurones and skeletal muscles do humans have approximately?
- What does the stimulation of one motor unit cause?
A
420,000 motor neurones
250 million skeletal muscle fibres On average each motor neurone supplies about 600 muscle fibres Contraction of all the muscle fibres in that unit
15
Q
- What is a reflex action?
A
Involuntary coordinated pattern of muscle contraction and relaxation elicited by peripheral stimuli
16
Q
- Outline the process of the tendon reflex action
A
- Stretching stimulates sensory receptors (muscle spindle)
- Sensory neurone activated
- Sensory neurone activates motor neurone within the spinal cord (integrating centre)
- Motor neurone is activated
- Effector (quadricep muscle of thigh) contract