What are the differences between central and peripheral nervous system?
CNS = brain and brain PNS = all nerves outside of this area
What are the differences between somatic and autonomic nervous system?
PNS divides into the motor division and the sensory division
Sensory = “afferent” brings info to CNS through sensory neurons
Motor = somatic and autonomic
-Somatic control is voluntary
-Autonomic control is involuntary, it splits into the sympathetic division (flight and fight) and the parasympathetic division (rest and digest)
Visceral motor, functional (smooth muscles and glands)
Describe the structure of a peripheral motor nerve - micro
- Nucleus
- Dendrites
- Soma (cell cytoplasm)
- Axon hillock (where the neuron attaches to axon)
- myelin shealth
- node of ranvier
- schawn cell
- terminal button
- neurotransmitters
Describe the physiology of an action potential
- Resting potential is about -70mv (-40–90)
- Na+/K-ATPase pumps 3Na+ out and 2K+ in (some Na+ flow in, some K+ leak out)
- Neurotransmitter binds to specific ligand-gated ion channel on post-synaptic membrane, Na+ influx = initial depolarization,
- Na+channels begin to close, slow K+ channels open
- K+ outflux along conc grad = repolarisation and then hyperpolarisation
- K+ gates close and resting potential is restored
- Absolute refractory stage -2nd action potential cannot occur
- Relative refractory stage - 2nd action potential can occur but only if it is significantly greater than usual
What are they modalities of sensation?
- Chemoreception - smell and taste
- Photoreception - vision
- Mechanoreception - pressure, touch and vibration
- Nociception -pain, damage to tissue
a) cuntaneous (skin)
b) somatic (joints and bones)
c) Visceral (body organs) - Thermoreception - temp change
- Proprioception - info on relative positions of parts of the body
What occurs in the knee-jerk reflex? (basic actions) What could change the reflex?
Patellar reflex - monosynaptic reflex arc (no interneurons in pathway)
1. Patellar ligament is struck with a reflex hammer
2. leg extends once and comes to rest
(sleep or LMN lesion may cause absence, multiple extensions can may be due to cellebellar disease, UMN may cause exagerated)
What do muscle spindles do
Detects muscle length
- Gamma motor neurones
- Small sensory organs enclosed in a capsule. They have contractile proteins (thick and thin filaments) at either end. –The central region is wrapped by sensory dendrites.
- They are found in parallel with extrafusal fibres.
What does the golgi apparatus do?
Muscle contraction (golgi tendon measures muscle tension) In the tendons (attach bone to muscle), the sensory dendrites are interwoven with collagen fibrils
What occurs in Brown Sequard syndrome?
Damage or lesion to one half on the spinal cord it causes;
1) Hemiplegia (paralysis of ipsilateral side of lesion and loss of proprioception (posterior column) -corticospinal
2) Hemianasthesia - loss of pain and temp on contralateral side (spinothalamic)
3) Hypertonia - increased tone on ipsilateral side
What are a group of neurons in the CNS/PNS called?
CNS = nucleus PNS = ganglion
What are a bundle of axons in the CNS/PNS called?
CNS = tract PNS = nerve
Describe the structure of a peripheral motor nerve - how does one axon form an motor nerve
Axon (wrapped in myelin sheath), wrapped in endoneurium
small bundle of axons wrapped in perineium = fasicle
bundle of fasicles plus blood vessels wrapped in epineurium = nerve
Describe conduction of a nerve impulse down an axon
- Action potential flows down an axon but depolarizing the adjacent membrane causing Na+ channels to open
- Propagation can only travel in one direction due to refractory periods
- Propagation speed increases due to myelination, this means that saltatory conduction can occur as the action potential can jump along nodes of ranvier (gaps in myelination)
What are the 5 senses?
- Sight - rods (light) and cones (colours)
- Hearing - mechanoreceptors, perception and vibration
- Smell - olfactory bulbs in nose
- Taste - taste buds in tongue
- Touch - afferent pathways
What occurs in the knee-jerk reflex? (neurons)
- Strike the patellar ligament, just below the patella (L2-L4 nervous tissue)
- This stretch this muscle spindle in quadriceps femoris muscle - produces 2 responses
- a) signal travels via sensory neurone to dorsal root ganglion into spinal cord at L4.
b) The bipolar neurone synapses without an interneuron to an alpha-motor neurone.
c) The alpha-motor neurone carries an efferent impulse back to the quadriceps femoris muscle = triggering a contraction.
4a) The other axon of the sensory neuron synapses with an inhibitory interneuron (Golgi bottle neuron)
b) This synapses with an alpha-motor neuron which carries an impulse to the antagonistic ham string muscle
c) this causes the hamstring to relax
What could cause Brown Sequard syndrome?
- Spinal cord tumour
- Trauma (gun shot wound)
- Infectious disease
- IV drug use
- Meningitis
- Herpes
- Syphilis
