Nervous Flashcards
What are the divisions of the nervous system?
CNS and PNS
PNS splits into somatic and autonomic
Autonomic splits into sympathetic and parasympathetic
What is the somatic nervous system?
A division of the peripheral nervous system
Voluntary control
Sensory perception
What is the structure of a neuron?
Cell body contained nucleus
Dendrites project off cell body and receive signals
Axon is a long projection covered in myelin sheath that carries signal to the synapse
What is the myelin sheath?
Fatty covering on axon which insulates to speed up the signal transmission
Gaps in this are nodes of ranvier which help to propagate the signal
What is multiple sclerosis?
Immune mediated disease that destroys myelin sheath and the cells that produce it.
Causes slow signal transmission and nerves become prone to damage
SX: reduced strength and motor control, reduced sensation, pain
What are the 3 types of neuron?
Sensory (afferent): detects stimulus and sends to CNS
Interneuron: bridges sensory and motor neurons/integrates signals
Motor (efferent): transmit motor signal from CNS to body
What are the 4 functional properties of neurons?
Excitability: stimulated to generate signals
Action potentials: neuron membrane depolarises to send signal
Synapse: junctions between neurons
Neurotransmitters: transmit signal across junction
What is the fight/flight NT?
Adrenaline
What is the concentration NT?
Noradrenaline
What is the pleasure NT?
Dopamine
What is the mood NT?
Serotonin
What is the calming NT?
GABA
What is the learning NT?
Acetylcholine
What are the 6 phases of an action potential?
Resting state
Stimulus and depolarisation
Threshold and AP
Repolarisation
Hyperpolarisation and Refractory
AP propagation
What is the resting state phase of an AP?
The cell is at rest with a stable membrane voltage
Inside cell is more negative than outside
What is the stimulus and depolarisation phase of an AP?
A stimulus causes the voltage across the membrane to change
This opens sodium channels (voltage-gated) allowing sodium ions to enter the cell
The cell becomes less negative inside charged than outside = depolarised
What is the threshold and AP phase of an AP?
If depolarisation of cell meets the threshold, further sodium channels open rapidly causing a mass depolarisation of the cell (the inside becomes way less negatively charged than outside)
Positive feedback loop allows the AP to travel along the neuron
What is the repolarisation phase of an AP?
Sodium channels close and potassium channels. No more sodium can enter the cell but potassium exits allowing the cell to become more negatively charged
What is the hyperpolarisation and refractory phase of an AP?
Repolarisation overshoots so inside of cell becomes more negatively charged than it should be at rest.
Therefore the cell cannot fire another AP, ensuring these move in one direction only
What is the AP propagation phase of an AP?
AP travels along axon to terminal, triggering release of NTs into synapse
What is a synapse?
Junction between cells
Presynaptic cell releases NTs that stimulate receptors of postsynaptic cell
NTs housed in vessicles which fuse with membrane at axon terminal to be released into cleft
Once complete, postsynaptic cell releases the NTs which are reuptaken by presynaptic cell
What is the synapse, NT and receptor of a neuron to muscle connection?
Synapse is called neuromuscular junction
NT is acetylcholine
Receptor is nicotinic
What is the foramen magnum?
Hole in cranium that allows cord to extend from brain into spinal column
What are meninges?
Protective layers of brain
Periosteal Dura Mater (adhered to skull)
Meningeal Dura Mater (adhered to deeper structures)
Subdural space
Arachnoid Mater
Subarachnoid space (CSF)
Pia Mater
Brain
What is CSF?
Cerebrospinal fluid
Housed in subarachnoid space
Made by choroid plexus in ventricles of brain
Supply and remove waste from brain/cord to prevent blood borne issues affecting them
‘Floats’ brain/cord to protect
What are the 3 main structures of the brain?
Cerebrum (main upper part)
Cerebellum
Brain stem
What is the cerebrum?
Main upper region of brain
Two hemispheres connected by corpus callosum
Four lobes divided by sulci - frontal, parietal, temporal, occipital
Many gyri (rises) and sulci (grooves) exist to increase surface area
What is the frontal lobe for?
High cognitive functions
Personality
Motor control
What is the parietal lobe for?
Processes sensory information
Spatial awareness
What is the occipital lobe for?
Visual processing
What is the temporal lobe for?
Auditory processing
Language
Memory (hippocampus)
What is the cerebellum?
Major motor centre!!
Receives multiple information (e.g. posture, balance, motor, vision, muscles) and coordinates it to produce movement
Receives information from all over body; send information mainly to stem/cord
Has extra folds = folia
3 lobes = anterior, posterior and flocculonodular
What is the brain stem?
Connects brain to cord
Acts as relay station for signals and controls life sustaining functions + reflexes
Has 3 regions: medulla oblongata, pons and midbrain (thalamus at the top)
What is grey matter?
Composed of neuron cell bodies, dendrites and axons
Makes up outermost brain layer but inner H in spinal cord
Pink/grey colour
Processes information
What is white matter?
Composed of bundled axons coated in myelin
Connects brain areas
Connection/communication: Carries signals between grey matter and to receiving cells
What is the brain blood supply?
Left and right internal carotid artery
Left and right vertebral artery
These converge in brain at circle of Willis and then feed into other vessels. This ensures continual supply of O2 and glucose to brain even if one vessel fails.
What is cerebral palsy?
Damage to brain tissue during development
Result ranges from mild weakness to paralysis
What is dementia?
Group of disorders affecting cognitive brain function
Multiple causes (inc. Parkinson’s, infection, trauma, HIV, huntingtons)
SX: memory loss, reduced cognition, reduced communication, reduced visual perception, changed mood
Progressively worsens over time
TX: control SX, maintain safety, support
What is the spinal cord?
Cylindrical bundle of nerve tissue extending from brain through foramen magnum down to L1/2
Relays signals between brain and body
Brain to body = motor
Body to brain = sensory
Inner H grey matter with white matter surrounding it
Same 3 layer meninges
Nerve roots of sensory and motor connect to cord at each vertebral level connecting the PNS to CNS
What are the 2 pathways of the somatic nervous system?
The afferent pathway is sensory (carries signals away from body to CNS)
The efferent pathway is motor (carries signals away from CNS to body)
What is a nociceptor?
Senses pain
E.g. skin receptor
What is a proprioceptor?
Senses position/movement
E.g. tendon receptor
What are the 4 stages of pain?
- Transduction: nociceptor detects and creates an AP
- Transmission: AP travels afferent pathway to cord + brain
- Modulation: process of modifying/controlling pain
- Perception: brain interprets pain signal and creates conscious experience
What is substantia gelatinosa modulation?
At spinal cord, pain signal may interact with interneuron causing an increase or decrease in the signal
What is gate control theory?
Cord can open/close gate go pain signals
Will close the gate if stimulus is not ‘painful’
Emotional/cognitive factors can open gate
What is descending pain modulation?
Brain can send signal down the pain pathway to inhibit signals
Serotonin and endorphins can act as a painkiller
What are neuromodulation techniques?
Medications, blocks or electrical therapies can interfere with pain signal transmission
What are spinal reflexes?
Rapid, involuntary response to a specific stimulus
Mediated by spinal cord (no brain input)
Achieved with interneurons - direct connection between sensory and motor
What are the 6 PNS nerve groups?
Cranial (12 pairs) - head/neck
Spinal (31 pairs) - spine to body
Brachial plexus - low C to high T spine to arms
Sciatic nerve - L/S spine to back of legs
Femoral - L spine to legs
Vagus - PNS innervation to organs
What is the stress response?
Threat perceived
Signal to hypothalamus activates stress response
Cortisol (increases glucose availability) and adrenaline (immediate physical action) released
Sympathetic nervous system outcomes
Once threat gone, parasympathetic system will restore balance
How is the paediatric nervous system different?
Skull not fused = brain less protected
Developing brain = trauma more damaging
Mental health presents differently
Undeveloped thermoregulation system = vulnerable to hot/cold
Undeveloped control/coordination = falls
Big head with weak neck muscles = high risk damage
How does the nervous system of geriatrics differ?
Reduced neural tissue = brain loose in skull
Signal transmission speed reduced = slow movement and reflex
Reduced peripheral sensation = injury risk
Reduced memory and decision making
What is a stroke/CVA?
Blood supply to part of brain interrupted leading to tissue damage
Can be haemorrhagic or ischemic (80%)
Brain needs constant oxygen and glucose supply
SX: F (facial drop), A (arms can’t raise), S (slurred, confused) E
TX: transport to ED, support
What is an ischemic stroke?
Blood vessel is blocked or narrowed (artherosceloris)
Thrombolic stroke - blood clot in brain
Embolic stroke - blood clot from elsewhere travels to brain
What is a haemorrhagic stroke?
Blood vessel ruptures causing bleeding
Intracerebral - weakened vessel or AVM bleeds into brain tissue
Subarachnoid - bleed into space between brain and layers (usually aneurysm)
What is a cerebral TIA?
Transient ischemic attack
Mini/warning stroke
Temporary disruption to brain blood flow which eventually resolves
SX the same as CVA
What is a seizure?
Abnormal electrical activity in the brain
Big surge in excitation
Can be focal (partial) or generalised
What is a focal/partial seizure?
Originates in specific area of one hemisphere
Simple: remain conscious, tingling, flashing lights, jerking
Complex: ALOC, repetitive movement, purposeless actions, emotional change
What is a generalised seizure?
Both hemispheres are involved and there is often a loss of conscious
6 types
SX: uncontrolled muscle movement, ALOC, staring, weird sensation, no tone, stiffness, confusion, fatigue
TX: transport to ED, remove objects/protect from harm, treat cause of seizure, midazolam
What is an absent seizure?
Generalised seizure often in children
SX: brief loss of awareness, staring, blinking/lip smacking
What is a tonic seizure?
Generalised seizure
SX: stiffening usually in arms, legs and back
What is a clonic seizure?
Generalised seizure
SX: rhythmic jerking of muscles usually in face, neck and arms
What is a myoclonic seizure?
Generalised seizure
SX: sudden, brief twitches
What is an atomic seizure?
Generalised seizure
SX: sudden loss of tone causing collapse
What is a tonic-clonic/grand mal seizure?
Severe generalised seizure
SX: tonic and clonic phases (stiff and rhythmic jerking), ALOC, convulsion, dyspnoea
What can cause a seizure?
Epilepsy
Fever
Brain injury
Infection
Tumour
Drugs
Metabolic disturbance
What is a traumatic brain injury?
External mechanical force causing brain tissue damage. Acceleration or deceleration of brain within cranium.
Focal: localised damage e.g. haematoma
Diffuse: widespread e.g. concussion
What is a concussion?
Temporary TBI
Caused by blow to head or violent shaking
Symptom onset can be immediate or delayed
SX: reduced concentration and memory, balance and coordination issues, headaches, N+V, fatigue, mood change, speech slurred, sleep issues, ALOC, seizure
TX: moderate/severe transport to ED, manage pain, stabilise head/neck, monitor ABC
What is a spinal cord injury?
Movement/force exceeds structures capacity resulting in damage to cord
Level affected = level of dysfunction
Paraplegia = T, L or S spine; torso/leg dysfunction
Tetraplegia/quadriplegia = all limb dysfunction
What are the 6 mechanisms of SCI?
Flexion: head/neck bends forward
Compression: cord squeezed together
Hyperflexion: neck bent back
Flexion-rotation: spine twists
Penetration: FB
Distraction: cord stretched apart
What is autonomic dysreflexia?
Life threatening condition with SCI above T6
Exaggerated response to a stimulus below T6 (usually bladder/bowel related). Signal cannot ascend above spinal cord injury so triggers the sympathetic nervous system
Need urgent medical treatment to correct stimulus
What are the SX of SCI?
Consider mechanism
Neck/back pain worsens with movement
Reduced sensation/movement in limbs
Respiratory issues
Abnormal positioning
Bladder/bowel incontinence
What is meningitis?
Inflamed meninges caused by a pathogen
Bacterial is the most aggressive
What is meningococcal?
Neisseria miningitidus bacteria multiples in the blood damaging vessel walls
Marked by non-blanching rash
What are SX of meningitis/meningococcal?
Sudden fever/chills
Extreme headache
Stiff neck
Photophobia
Altered mental status
N+V
Non-blanching rash
Fatigue
Cold extremities
Body pain
High RR
What are SX of drug overdose?
Sedation
Altered mental state
Slurred speech
Reduced RR
Cyanosis
Weak/loss muscle control
N+V
ALOC
Low HR and BP
Pinpoint pupils
