Nervous system Flashcards
What do Afferent and Efferent mean?
Afferent - signal sent into CNS
Efferent - signal sent out of CNS
Describe the PNS (2)
- Detects internal/external stimuli
- Controls conscious (somatic) movement and autonomic function
Describe the CNS (3)
- Consists of brain and spinal cord
- Processes internal/ external information relayed
- Communicates with PNS to act on effectors
Describe Neurons and how they communicate (2)
- Fundamental cell units of nervous system
- Use electrical/chemical signalling to communicate
What are the 3 types of communication neurons perform?
- Input
- Computation
- Output
What are the 3 main classes of neuron?
- Sensory neurons
- Interneurons (process/relay)
- Motor neuron (effectors)
Describe how neurons communicate (3)
- Neurons sends electrical impulse (action potential) along axon to terminals
- Action potential release chemical neurotransmitter into synapse (acetylcholine)
- Neurotransmitter can initiate action potential in subsequent neuron
What are the 2 types of nerve fibres exiting the CNS to the PNS?
- Spinal nerves
- Cranial nerves
Describe nerve fibres, and what they contain (3)
Axons bundled together (contains axons, connective tissue and blood vessels etc)
Describe spinal nerves
nerve fibres exiting spinal cord
how many pairs of spinal nerves exit the spinal cord to innervate regions of the body?
31
Describe a dermatome and what it provides
- Regions of body innervated by given spinal nerve
- Provides motor control + sensation
Name the 5 dermatomes (Can The Lorax Say Cheese)
- Cervical
- Thoracic
- Lumbar
- Sacral
- Coccygeal
How many cranial nerve pairs are there?
12
Where do the cranial nerves send signals from?
brain/brainstem
What are cranial nerves responsible for? (5)
- Sensation + motor control in face, neck and eyes
- Autonomic function(vagus nerve)
- vision
- Olfaction (smell)
- Audition (hearing)
Describe sensorimotor circuits (reflexes) (3)
- Detection of stimuli (sensory afferent neurons)
- Processing info (interneurons)
- Output (motor efferent neurons)
Describe the withdrawal reflex (doesn’t require brain)
- Sensory neuron (afferents) detect painful stimuli
- Signal projected to spinal cord via dorsal root (cell bodies in dorsal root ganglion, PNS)
- Motor neuron efferents travel via ventral root to muscle effectors (motor neuron cell bodies in spinal cord grey matter (CNS)
What is the spinal cord divided into? (2)
- grey matter (cell bodies)
- white matter (axons)
Name the 2 main sensorimotor tracts in the spinal cord
- Spinothalamic tracts
- Pyramidal tracts
What are the functions of the spinothalamic and pyramidal tracts?
Spinothalamic tracts - pain, temp and light touch (afferent)
Pyramidal tracts - motor neurons (muscle movement) (efferent)
Describe the pathway of the spinothalamic tract (3)
- sensory neurons cross to contralateral (opposite) side at spinal cord
- Ascending sensory fibres pass up via medulla to thalamus
- neurons pass from thalamus to somatosensory areas in brain to process sensory info
Describe the pathway of the pyramidal tract (3)
- Upper motor neurons from motor cortex to medulla
- Motor neurons cross at medulla to contralateral side
- Lower motor neurons exit spinal cord to control skeletal muscle
What causes Brown-Sequard syndrome?
Hemi-section (half-cut) of spinal cord
What are the symptoms of Brown-Sequard syndrome? (2)
- Ipsilateral (same-side) loss of motor control
- Contralateral loss of sensory function
What are the effects of sympathetic nervous system activation? (4)
- Increase heart/breathing rate
- Inhibits digestion
- Stimulates glucose release (glucocorticoid)
- Redirects blood flow to heart, lungs and muscles (most blood vessels only controlled by SNS)
Where does the sympathetic nervous system originate?
Thoracic-lumbar spine (chain ganglia - collection of cell bodies just outside spinal cord)
What are the effects of the parasympathetic nervous system? (3)
- Decrease heart/breathing rate
- Stimulates digestion
- Stimulates glucose storage
Where does the parasympathetic nervous system originate? (2)
- Cranial nerves and sacral spine (ganglia net to target organs, no chain ganglia)
- Vagus nerve (key ParasympatheticNS nerve)
what is a ganglia?
Collection of cell bodies of the postganglionic neurons
Define pre/postganglionic and describe the order (3)
Postganglionic - neurons after ganglia
preganglionic - neurons before ganglia
Order = preganglionic -> postganglionic -> target organ
Name the neurotransmitters used by pre/postganglionic fibres of ANS (sympathetic/parasympathetic)
- Sympathetic - pre = acetylcholine, post = noradrenaline
- Parasympathetic - pre + post = acetylcholine
Why is the ANS an important drug target?
Powerful regulatory effects on organ systems
Name the effects of Beta blockers (3)
- Block noradrenergic receptors
- Reduce effects of SympatheticNS
- Decrease blood pressure, can alleviate physiological anxiety symptoms
Name the effects of lesions on autonomic and sensorimotor function (medullary syndrome - often caused by stroke of arteries supplying medulla) (3)
- Vertigo
- Impaired facial sensorimotor control
- Autonomic dysfunction (eg. pupil constriction, eyelid drooping and lack of facial sweating)
Name the effect of lesion dependant on location (Lateral/Medial) (2)
- Lateral - pyramidal tract (motor) function spared
- Medial - pyramidal tract (motor) function impaired
