Peripheral Nervous System Flashcards
How can the peripheral nervous system be divided?
Sensory (afferent) and motor (efferent)
The motor can be divided Into autonomic and somatic
The autonomic can be divided into sympathetic and parasympathetic
How many cranial nerves are there?
12
How many spinal nerves are there?
31
C (8)
T(12)
L(5)
S(5)
Co(1)
Where do somatic nerves convey information from?
Afferent: from skin, skeletal muscle and joints
Efferent: to skeletal muscles
What are dermatomes and myotomes?
Dermatome: an area of skin that is supplied by a single spinal nerve
Myotome: a group of muscles innervated by a single spinal nerve
What are visceral nerves?
Carry info from the thoracic, abdominal and pelvic organs
Autonomic
What can visceral efferent nerves be divided into?
Sympathetic and parasympathetic
Fight or light and rest and digest
What is a ganglion
A collection of cell bodies outside the CNS
What is a nucleus?
A collection of cell bodies inside the CNS
What is a plexus?
A network of interconnecting nerves
Where do all afferent fibres have their cell bodies?
Spinal ganglia
Where do all efferent nerves synapse?
In a peripheral ganglion
How are peripheral nerves arranged?
In fasiculi (bundle)
Surrounded by three layers of connective tissue (endoneuroum, perineurium, epineurium)
How are peripheral nerves classified?
Two systems
Conduction velocity: classed into A,B,C (A being the fastest)
Axonal diameter: sensory only. Uses Roman numerals I-IV (I being the largest diameter)
Myelinated with a large diameter have the fastest conducting velocities
What are the types of sensory receptors?
Detect external or internal info
External: exteroceptors (pain, temperature, touch, pressure)
Internal: proprioceptors (movement,joint position) enteroceptors (movement through gut, blood pH)
Or can be classified by mode of detection (chemoreceptors, photoreceptors, thermoreceptors, mechanoreceptors, nociceptors)
What are the types of proprioceptors?
Muscle spindles: detect changes in muscle length
Golgi tendon organs: detect changes In tension in tendons
Joint receptors: found in joint capsules, detect start and end of movement
What are the synapses of motor neurones?
Between a motor neurone and a muscle fibre : neuromuscular junction
What is a motor unit?
A single motor neurone along with al lure muscle fibres that it innervates. It is the smallest functional unit with which to produce force
Humans have approx 420000 motor neurones and 250 mil skeletal muscle fibres
So on average each motor neurone supplies 600 muscle fibres
Stimulation of one motor unit causes contraction of all the muscle fibres in that unit
What is a reflex?
An involuntary coordinated pattern of muscle contraction and relaxation elicited by peripheral stimuli
Bypasses the conscious brain
What are the neurotransmitters used in the autonomic nervous system?
Acetylcholine in pre ganglionic
Noradrenaline (S) and acetylcholine (P) in post ganglionic
Where do sympathetic and parasympathetic nerves emerge from the spinal cord?
Sympathetic: thoracolumbar section (T1-L2)
Para: craniosacral outflow (cranial nerves III, VII, IX,X) and (S2-S4)
