The Nervous System Flashcards
What are the components of the Central Nervous System?
- Brain
- Spinal Cord
(within the skull and vertebral column)
What are the components of the Peripheral Nervous System?
- Nerves
(connects the CNS to the other tissues in the body)
What are the 4 lobes of the brain?
- Occipital
- Temporal
- Frontal
- Parietal
How heavy is the brain?
1.5kg
How many pairs of cranial nerves are there?
12
How many pairs of spinal nerves?
31
What do cranial nerves control?
control functions of face and special senses
Where do cranial nerves arise from?
arise from the brainstem
What do spinal nerves control?
control functions of head, neck, arms, legs, thorax and internal organs
Where do spinal nerves arise from?
arise from the spinal cord
How long is the spinal cord (approx.)?
approximately 45cm
What does a bundle of neurones together in the PNS make?
a nerve
How does the brain communicate with the body?
The brain sends and receives information to and from the body via the nerves
What are examples of neurotransmitters?
- Dopamine
- Serotonin
- Acetylcholine
- Substance P
- Glutamate
- GABA
- Histamine
- Endorphins
- Adrenaline
Give (5) examples of uses of the nervous system
- movement
- sensation
- memory
- balance
- language
- behaviour
- aging
- sleep
- sweating
- hormone control
- healing and immune system
What are signs of neurological injury or illness?
- Weakness
- Sensory loss/changes
- Reduced co-ordination
- Reduced proprioception
- Altered balance
- Visual field loss
- Hearing impairment
- Altered speech
- Unable to swallow
What are symptoms of neurological injury or illness?
- Double vision
- Hearing loss
- Pins and needles
- Numbness
- Pain (but not always!)
- Weakness
- Memory problems
- Odd behaviour
- Mood changes
What are some examples of Peripheral nerve disorders?
- Carpal tunnel syndrome
- Sciatica
- Trauma
- Erb’s palsy
- Neuropathy
- Guillian Barre Syndrome
- MND
What are some examples of Central nervous disorders?
- Stroke
- Head injury
- Meningitis
- Cerebral palsy
- MND
What are some examples of neurodegenerative disease?
- Parkinson’s
- Huntington’s
- Alzheimer’s
- Multiple Sclerosis
- Prion disease
- Spinal Muscular Atrophy (SMA)
- Spino-Cerebellar Ataxia (SCA)
What are some examples of neuropsychiatry disorders?
- Seizures
- Anxiety
- Neurocognitive impairment
- Neuropathic Pain (migrane)
- Mania
- Physical Disability
- Addiction
- Epilepsy
- Mood disorder (aggression and violence)
What is the purpose of the somatic nervous system?
guides your voluntary movements.
What is the purpose of the autonomic nervous system?
regulates the activities you do without thinking about them (involuntary movements).
What is the name of the specialist receptor that connects the nervous system to the muscles?
motor end plate
Spinal nerves connect the nervous system to what?
the spinal cord
What is a nerve plexus?
a network of intersecting nerves that supply the same part of the body
What are the different Plexi?
- Cervical
- Brachial
- Lumbar
- Sacral
- Coccygeal
- Autonomic (serving internal organs and GI tract)
What area does the Cervical Plexus supply?
Head, Neck + Shoulders
What are (4) nerves in the sensory branch of the Cervical Plexus?
- Greater Auricular Nerve
- Transverse Cervical Nerve
- Lesser Occipital Nerve
- Supraclavicular Nerve
What area does the Brachial Plexus supply?
Chest, Shoulders, Arms and Hands
What are the branches of the Brachial Plexus?
- Musculocutaneous nerve supplies
- Axillary nerve supplies
- Median nerve supplies
- Ulnar nerve supplies
- Radial nerve supplies
What is Neuropraxia?
Local myelin damage with the nerve still intact
What is Axonotmesis?
- Continuity of axons is lost.
- Endoneurium, perineurium, and epineurium can remain intact.
- Loss of continuity of axons with Wallerian degeneration due to disruption of axoplasmic flow.
What is Neurotmesis?
Complete physiological disruption of entire nerve trunk.
What areas do the lumbar plexus supply?
- Back
- Abdomen
- Groin
- Thighs
- Knees
- Calves
What are the (6) branches of the lumbar plexus?
- Iliohypogastric
- Ilioinguinal
- Genitofemoral
- Lateral femoral cutaneous nerve
- Obturator nerve
- Femoral nerve
What areas do the sacral plexus supply?
- Pelvis
- Buttocks
- Genitals
- Thighs
- Calves
- Feet
What are the (5) branches of the sacral plexus?
- Superior gluteal nerve supplies
- Inferior gluteal nerve supplies
- Sciatic nerve (L4-S3) supplies
- Posterior femoral cutaneous
- Pudendal nerve supplies
Ganglion.
Collection of cell bodies
Fasciculus.
Cluster of axons forming a recognisable bundle
Funiculus.
Bundle of axons forming a raised bump on the surface of the CNS (especially in the spinal cord)
Tract.
Cluster of axons with similar functions
Nucleus.
Cluster of cell bodies with similar functions
What are the large divisions of the brain?
- Brainstem
- Diencephalon
- Cerebellum
- Cerebral Hemispheres/Cerebrum
What is the brainstem comprised of?
- Medulla
- Midbrain
- Pons
What is the source of the cranial nerves?
the brainstem
What is the role of the brainstem?
Control autonomic functions:
- Breathing
- Heart rate
- Level of consciousness
Many descending pathways of the brainstem decussate (cross over) in what?
the medulla
What is the diencephalon composed of?
- Thalamus
- Hypothalamus
- Epithalamus
What are the roles of the diencephalon?
- Integration of sensory info
- Interpretation of pain
- Some role with hormone release
How is the cerebellum attached to the brainstem?
via 3 peduncles
What is the cerebellum involved in?
maintaining balance + control
What are the (4) lobes of the cerebrum?
- Frontal
- Parietal
- Occipital
- Temporal
What are sulci (cerebrum)?
grooves
What are gyri (cerebrum)?
wrinkled with hillocks
Which fissure separates the 2 hemispheres?
central or longitudinal fissure
What white matter structure connects the 2 hemispheres?
the corpus callosum
What is the name of the groove between the frontal and parietal lobes?
central sulcus or fissure of Rolando
What are deep sulci?
fissures
What is the frontal lobe responsible for?
- Some aspects of movement
- Behaviour
- Emotion
- Higher executive function
- Expressive speech
What is the supplementary motor area involved in?
preparation of self-initiated movement
What is the name of the fissure between the temporal and frontal lobes?
Sylvian fissure
What is the role of the premotor cortex?
role in the preparation of sensory triggered movement and guiding complete behavioural acts
What is the occipital lobe responsible for?
Vision
What is the primary motor cortex responsible for?
actual execution of movement
What is the parietal lobe responsible for?
- Language
- Sensation
- Perception of space
What is the temporal lobe responsible for?
- Hearing
- Expressive speech
- Memory
What is the somatosensory cortex involved in?
complex processing of sensory info
Where does the spinal cord terminate?
approx. T12
What is the spinal cord comprised of?
- Ascending sensory tracts
- Descending motor tracts
What is the meninges made up of?
- Dura mater (dural sheath)
- Arachnoid mater
- Pia mater
Hemianopia
loss of half the visual field
What lobe is the somatosensory cortex in?
the parietal lobe
How many lobes are there in a brain?
8
What is the function of the occipital lobe?
interpretation of vision
What is the function of the cerebellum?
- Balance
- Co-ordination
- Proprioception
What is the function of the basal ganglia?
quality of movement
What is the function of the frontal lobe?
- Movement
- Higher executive function
How many neurons are there in the brain?
approx. 86 billion
Cell body.
Contains nucleus and all the things needed to sustain the metabolic activity of the neuron
Dendrites.
- Processes of cell membrane radiating from cell body in various directions
- Predominantly receive information and send it to the cell body
Axons
- Long tubular extension of the cell membrane and cytoplasm
- Extends towards atarget
- Sends information away from the cell body
Plasmalemma.
Semipermeable membrane of the neuron
Neurons.
Convey information by conducting electrical signals (action potentials)
– but use chemical information to pass messages from one neuron to the next (synapse)
Nerve fibre.
the axon + surrounding Schwann cell
Nodes of Ranvier.
junctions between Schwann cells
Oligodendrocytes.
specialist cells that perform myelination in the CNS
Schwann cells.
specialist cells that perform myelination in the PNS
Myelin.
lipid (fatty) sheath that wraps around axons
Unipolar
Autonomic nervous system:
- one single process
- axon emerges from cell body and branches into dendrites.
Bipolar.
Functionally specialised sensory cells.
- Two processes form from the cell body, one an axon that carries information to CNS, dendrites that convey information from periphery.
Psuedounipolar.
Certain sensory cells (i.e. touch or stretch).
- Bi-polar which fuses to form one axon from cell body
- One branch goes to periphery (to sensory receptors)
- Other to spinal cord
Multipolar.
Predominate form in our nervous system.
- Single axon, and typically many dendrites around cell body.
- Number dendrites correlates with number of synaptic connections
What does the distribution of Na+ and K+ lead to (in a neuron)?
an electrical gradient across the plasmalemma (greater +ve charge outside)
Depolarisation (at the post synaptic plasmalemma).
more +ve ions cross into the neuron (making the inside more +ve)
Excitatory postsynaptic potential (EPSP)
Hyperpolarisation (at the post synaptic plasmalemma).
less +ve ions to cross into the neuron (inside more -ve)
Inhibitory postsynaptic potential (IPSP)
Excitatory postsynaptic potential (EPSP).
More +ve ions tocross into the neuron (making the inside more +ve)
– Depolarisation
Inhibitory postsynaptic potential (IPSP).
Less +ve ions to cross into the neuron (making theinside more-ve)
– Hyperpolarisation
Temporal Summation.
if lots ofExcitatory postsynaptic potentials (EPSPs) arriveone after the other in quick successionthis increases the neteffect
Spatial Summation.
multipleExcitatory postsynaptic potentials (EPSPs) arriveat different locations on the dendriteincreases the net effect
When are action potentials able to occur?
If there’s enough Excitatory postsynaptic potentials (EPSPs)
- and outweighs the Inhibitory postsynaptic potentials (IPSPs) to give a net depolarisation
How do Na+ channels closing & K+ channels opening affect membrane potential?
Becomes more -ve
(no further Na+ enters the axon hillock and K+ exits the hillock)
What happens when a cell is hyperpolarised?
K+ channels to close and the cell then reverts to its resting potential
How does hyperpolarisation occur?
moreK+ leaves the hillock than Na+ has entered so thepotential overshoots
Absolute refactory period
immediately after peakNa+ conductance theNa+ channels areinactive
- so noNa+ ions can move in or out and the hillock cannot fire another action potential
Relative refactory period
Immediately after peak K+ conductance as the Na+channelsbecome active and theplasmalemma repolarises.
- to set up an action potential requires more stimulus than when in the resting state
What is the speed of propagation dependent on?
- Diameter of axon (larger = faster conduction)
- Presence of myelin (concentrates K+ and Na+ channels in nodes so increased conduction velocity)
When an action potential arrives at an axon terminal/presynaptic process what happens?
Ca++ channels open
so calcium floods into the bouton
What does an increase in Ca++ lead to?
- Synaptic vesicles dock and fuse with axon terminal membrane
- The vesicles remain fused to the membrane until the Ca++ concentration has increased to a critical point
- At this point the vesicle fuses into the membrane and releases neurotransmitter into the synaptic cleft
- Retrieves new vesicles from a storage area so that the process can be repeated.
What are (3) possible causes of injury to the nervous system?
- Direct injury to neuron(s)
- Disruption to neural function due to indirect effects of injury (decreased blood flow, oedema, cerebral metabolism, CSF)
- Synaptic loss from damaged neuron cascades that cause degeneration of neighbouring neurons (leading to further damage)
Describe Wallerian Degeneration (PNS).
- Trophic degenerationof the neuron at site of lesion and travels distally from cell body
- Swelling andgranulation
- Lasts for3-4 days
- Myelindegenerates too
- Growth factorspromote thegrowth of axonal buds
- Regenerationbegins to occur at7 days
- Growth occurs at1-4mm a day
- Processoccurs alongsiderestoration of the Schwanncells
Describe the affect of Diaschisis & Oedema on the nervous system.
- Temporary disruption of neural function (due to shock of injury or disease)
- This can occur locally to the injury or at some distance (due to altered metabolism and reduction of blood flow)
- Oedema is common around the brain following injury
- Can be local or remote
- Can be significant enough to block neural conduction
- Some function is restored when diaschisis and oedema settle
What are the (6) mechanisms of plasticity?
- Denervation
Supersensitivity - Unmasking of silent synapses
- Synaptogenesis
- Collateral sprouting
- Short- and long- term potentiation
- Cortical remapping
When does Denervation Supersensitivity occur?
when there’s a loss of input from another area of the brain
Describe Denervation Supersensitivity?
The post synaptic membrane becomes more sensitive to the release of neurotransmitter
Describe the unmasking of silent synapses.
- During recovery previously unused synapses are recruited
- Suggests the existence of structural synapses in the brain that are not normally functional due to competition
How long does Synaptogensis (Regenerative) take following injury?
Occurs within 3-7 days of injury
What happens during Collateral Sprouting (reactive synaptogenesis)?
Neighbouring, uninjured axons sprout to innervate synaptic sites previously activated by the injured neuron
What is short-term potentiation?
- A change in the performance or output of a synapse in the short term
- An increase in synaptic strength due to increase in neurotransmitter production and/or altered post synaptic receptors
What is long-term potential (LTP)?
- Change in the performance or output of a synapse in the long term
- Related to increase in pre-synaptic neurotransmitter release + structural change of the post-synaptic structure
- Related to spatial + temporal summation (LTP occurs with high frequency stimulation or pairing of stimulation)
This is how we learn!
What is Cortical Remapping?
Areas of brain cortex are modifiable by sensory input, experience and learning (as well as response to injury)
When may cortical remapping/reorganisation not be possible?
when large areas are damaged
What can cortical remapping be influenced by?
training
What may aid recovery of function (Cortical Remapping)?
Ipsilateral motor pathways (uncrossed)
What enhances/effects neuroplasticity?
- Use dependent and specific
- Repetition or practice at intensity
- Early intervention is better (first 12 weeks)
- Salience, motivation, feedback and attention
- Environment (sensory, cognitive, social and motor)
- Age, genetics, pharmacology, size of lesion and stress
- Adjunct therapies can prime the motor system to enhance neuroplasticity
What are the clinical implications of neuroplasticity?
- Multiple pathways innervating our motor + sensory cortices
- Dominant pathways show functional activity
- If these are lost, the less dominant pathways can become functional
- Experience + use are important in ensuring these less dominant pathways become functional in the short- and long-term
Describe Transneuronal degeneration.
- Axotomy: axon of a neuron is cut.
- Anterograde Degeneration: distal portion of damaged neuron degenerates.
- Retrograde Degeneration: proximal portion of damaged neuron may degenerate.
- Transneuronal Degeneration: neurons that synapsed on the damaged neuron may degenerate.
