Neurology - basics Flashcards
What is the morphological classification of the NS?
CNS - brain and spinal cord
PNS - everything else incl cranial and spinal nerves
Direction of flow classification?
Afferent/sensory system - information toward from CNS/PNS
Efferent/motor system - information away from CNS/PNS
Physiological classification?
Somatic/voluntary - coordinates voluntary control
Visceral/involuntary - involuntary activities such as digestion
What is grey and white matter?
Grey matter - cell bodies
White matter - axons
What is the blood supply to the brain?
Via the carotis arteries, which pools in cerebral arterial circle before distributed to the brian.
Brain requires rich blood supply.
What is the ventricular system of the brain?
A system of cavities through the brain, which contain ependymal cells. These secrete cerebrospinal fluid from the choroid plexus.
What is cerebrospinal fluid?
Its ultra-filtrated blood, containing glucose and minerals for nutrition and provides shock support.
What are the layers that protect the brain?
Skull bone
-Epidural space
-Dura mater
-Subdural space
-Arachnoid layer
-Subarachnoid space
-Pia mater
What is the epidural space?
Loose connective tissues, veins and lymphatics. This cusions the brain.
What is the dura mater?
Thick, dense fibrous tissue fused with bone
What is the subdural space?
Contains lubricating fluid
What is the arachnoid layer?
Has cerebrospinal fluid and blood vessels providing nutrition and cushioning
What is the subarachnoid space?
Cerebrospinal fluid leaking from the ventricular system with varying thickness
What is the pia mater?
A thin layer on the brain with many tiny blood vessels.
What are the elevations and depressions called?
Folds - gyri
Grooves - sulci
What is the peripheral NS?
links the environment with the central nervous system using efferent and afferent fibres.
All spinal nerves are a mix of sensory and motor.
What are cranial nerves?
Sensory
I - olfactory
II - optic
VIII - vestibulocochlear
Motor
III - oculomotor
IV - trochlear
VI - abducten
XI - accessory
XII - hypoglossal
Mixed
V - trigeminal
VII - facial
IX - glossopharyngeal
X - vagus
What is the anatomy of the neurones?
Cell body/soma - converts signal to membrane potential, contains nucleus
Dendrites/receptor segment - conducts impulse and recieves information
Axon/neurone fibre - relays impulses to other neurones and effector organs. Myelinated for insulation by Schwann cells in PNS and Oligodendrocytes in CNS
What are the protein molecules on the nerve membrane?
Receptor proteins - bind to neurotransmitters
Channel proteins - acts as pores for ion movements
Transport proteins - transfer ions
What are the different classifications of neurones?
Multipolar - most common. Multiple dendrites and one axon e.g. motor neurones
Bipolar - one dendrite and one axon e.g. olfactory, retina and ear. Cell body in middle.
Pseudopolar - sensory information from skin and organs to spinal cord e.g. sensory neurones
What makes up the support matrix?
Neuroglia surrounds neurones and supports it all. Capable of mitotic activity.
Fibrillary and protoplasmic astrocytes - nourishment and metabolic support
Oligodendrocytes - insulate the cells of CNS
Microglia - macrophages of the CNS and 10-15% of the brain cells
Action potential formation?
Resting potential - usually -75mV, due to electrical difference across the membrane. Maintained due to selective permeability (readily in to K+ and slightly to Na+) and sodium-potassium pump (Na+ out and K+ in)
Action potential - voltage gated Na+ channels open, Na+ floods in. Up to +30mV.
Repolarisation - Na+ gates close and K+ open, removing K+ from inside and bringing back down to -90mV.
What happens when the AP reaches the end?
- Voltage gated Ca2+ channels open, leading to an influx of Ca2+
- This causes vesicles with neurotransmitters to fuse to membrane, releasing contents into synapse.
- The neurotransmitters diffuse across the synapse and bind to the post-synaptic receptors
- Neurotransmitters are then either recycled or broken down by an enzyme
What happens when the AP reaches the end?
- Voltage gated Ca2+ channels open, leading to an influx of Ca2+
- This causes vesicles with neurotransmitters to fuse to membrane, releasing contents into synapse.
- The neurotransmitters diffuse across the synapse and bind to the post-synaptic receptors
- Neurotransmitters are then either recycled or broken down by an enzyme
What are the types of neurotransmitters?
Peptides that are either excitatory, inhibitory or modulatory. Two main types:
-ACh, Acetylcholine - released at neuromuscular junctions and ANS.
>Nicotinic receptors - preganglionic neurones in neuromuscular junctions and autonomic nS
>Muscarinic receptors - pre- and post-ganglionic in parasympathetic and pre-ganglionic sympathetic
-NAd, Catecholamines - in sympathetic nervous system on post-ganglionic neurones.
>Adrenoreceptors, B1 in heart excitatory, B2 smooth muscle relaxatory
Also glutamine (brain), glycine (SC inhibitor), GABA (CNS inhibitor), dopamine, serotonin
What can block neurotransmitters?
Agonists - make transmission more likely
e.g. preventing reuptake of neurotransmitters (prozac/cocaine), trigger the receptor itself (nicotine) or making receptor more responsive (anti-anxiety)
Antagonists - make transmission less likely.
e.g. blocking receptor site (snake venom) or preventing release of neurotransmitter (anti-psychotic drugs)
What makes up the autonomic nervous system?
Parasympathetic - slows down
Sympathetic - speeds up
What makes up the somatic nervous system?
Sense organs and voluntary muscles
Afferent - toward CNS
Efferent - away from CNS
What makes up the peripheral nervous system?
The somatic nervous system and the autonomic nervous system
Whats an example of a reflex arc?
Organ>Sensory receptor>Visceral afferent>Integrating centre>Pre-/Post-efferent>visceral efector
What is the efferent 2-neurone system?
- Pre-ganglionic in CNS - longer in parasympathetic, shorter in sympathetic. Typically uses ACh
- Post-ganglionic in PNS -
> Longer in sympathetic and shorter in parasympathetic. Located very near, if not in the walls of the effector organs
> Parasympathetic uses ACh and sympathetic uses NAd
Does the somatic nervous system have 2 neurone system?
No it is just one neruone from CNS to skeletal muscle
What is the nerve distribution of sympathetic system?
They originate in the lateral horns of T1 - 12 and L2-3 of spinal cord (thoracolumbar)
What is the nerve distribution of the parasympathetic system?
Originates in brainstem (II, VII, IX and X) and in S2-4. The most important is X which arises from the medulla oblongata.
What is the somatic nervous system??
Makes up part of peripheral nervous system involving voluntary movement.
What makes up the SNS?
- Afferent nerves - reception of internal and external stimuli
- Processing centre - somatomotor cortex and cerebellum down to spinal cord
- Efferent nerves - from CNA to skeletal muscle to move the limb
Only one neuronal pathway with ACh.
What is a neuromuscular junction synapse/
Between nerve and muscles. Its grooved to fit the surface of skeletal muscle and increase surface area. It contracts a muscle completely (all or nothing)
What does a Golgi receptor do?
Measures muscle tension via tendons
What do muscle spindles do?
Measure muscle length
What do meisner corpuscles do?
Measure light touch
What do merkels disks do?
Measure deep touch
what do pacinan corpuscles do?
Measure pain/deep pressure
What do ruffini corpuscles do?
Measure stretch
What do free nerve endings do?
Measure pain
What is a reflex arc?
Does not pass the brain to allow quick movement. Brain does eventually recieve sensory input while the action is occuring.
Receptor > sensory neurone > spinal cord > interneuron > motor neurone > effort organ
What is the patella reflex?
- Tapping patella stretches quad
- Sensory neurones fire to spinal cord
- Spinal cord detects signal and sends a response via interneurone. L4-L6 for femoral nerve leads to stifle extension
- Motor neurone carries response to muscle contracting the quads
What is the withdrawal reflex?
- Forceps pinch web between toes
- Pain receptors fire to spinal cord
- Spinal cord detects signal and sends reponse via interneurone. L6-S1 via sciatic nerve.
- Flexor muscles and limb is protracted (hamstring)
What other reflexes are there?
-Cranial tibial reflex via peroneal nerve (L6-7)
-Perineal reflex via pudendal nerve (S1-3)
What is the largest foramen?
Foramen magnum - passage for the centra nervous system, connecting brain and SC
What are the intervertebral space and foramina?
Intervertebral foramen is the root of spinal nerves, arteries and ligaments.
Vertebral foramina - vertebral canal
Transverse foramen - holes by big hole, occupied by veins/arteries
What is the antlo-occipital joint?
Base of head, where it joins the vertebrae
How far do the nerves go down the spine?
To L1-2 and then spread to cauda equina
What is the dorsal root ganglia?
A collection of nerves that emergy from the dorsal root of spinal nerves
What are the four main nerves in the forelimb?
