Neurology: Physiology Flashcards
In NS: what are the 2 general groups of cells?
- Neurones
- Glial cells
What is the role of neurones?
Send and receive neurotransmitters
(they can be sensory, motor or interneurones)
What is the role of glial cells?
- Support
- Nourish
- Insulate
- Remove water products of metabolism
…for the neurones
Function of neuronal cell body? other name for it?
Stroma
- Contains nucleus + organelles
- It is the centre of neuronal metabolism (site of protein synthesis)
Function of neuronal dendrites? what are they?
- Originate from stoma and project outwards
- They transmit signals from other neurones => storm (receive info)
Function of neuronal axon ?
AP arises from axon hillock => transmitted along axon
Function of neuronal axon terminal?
synapse
- Contain neurotransmitters which are released to synapses to allow signal transmission
Schwann cell function? found where?
Insulate axon with myelin sheath?
- Found in PNS
What are the different types of glial cells? (4)
- Astrocytes
- Oligodendrocytes
- Microglia
- Ependymal
Describe neurones relationship with glycogen?
Neurones can’t produce or store glycogen but astrocytes can so store it on neurones behalf
Astrocytes function? (4)
- Metabolic support (glycogen and lactate store)
- Regulate ions (remove excess K+ => prevent spontaneous depolarisation)
- Breakdown harmful substances (excess neurotransmitter)
- Promotion of myelination by oligodendrocytes
Oligodendrocytes function
Insulation of the cells of the CNS with the myelin sheath
How many axons can oligodendrocytes and Schwann cells insulate ?
- Oligodendrocytes: one oligo can myelinated 50 axonal segments
- Schwann cell: can only myelinated one axonal segment
Glial cells: microglia function?
Resident immune cells (recognise foreign antigens => initiate phagocytosis)
Glial cells: Ependymal cell function? where are they found? together they make the?
- Thin lining of the ventricular system of brain + spinal cord
- Makes up the choroid plexus: responsible for production of CSF
What is CSF?
Clear watery fluid surrounding the brain & spinal cord
Where is CSF found?
Contained with subarachnoid space + central canal of the spinal cord
How does the contents of CSF compare to blood?
Generally everything in CSF conc is lower in everything except same osmolality and higher in protein and Na+ and Cl-
Describe the flow of CSF
- Produced continuously in choroid plexus (ependymal cells in 2 lateral ventricles + roof of 3 + 4)
- Lateral => 3rd => 4th => subarachnoid => central canal (through 2 lateral foramina of luschka or medial foramen magendie)
How does blood get filtered to become CSF?
In choroid plexus: blood freely permeates through fenestrated capillary loops and ependymal cells create blood-CSF layer
How is CSf cleared?
CSF drained into superior sagittal venous sinus through arachnoid villi
Functions of CSF?
- Bouyancy (makes brain weigh less)
- Protection (shock absorber)
- Homeostasis
- Clearing waste
Where do the waste products of the brain go?
excreted into CSF => bloodstream
What are neurotransmitters?
Endogenous chemicals that allow communication:
1) within nervous system
2) between NS and rest of body
Between what junction are neurotransmitters present?
- One neurone to another (synapse)
- Neuromuscular junction (NMJ)
- Neurone to target gland
what is most abundant NT in brain? what type?
Glutamate
- Excitatory NT (increase electrical excitability on post-synaptic side)
Name an inhibitory NT?
GABA
What 2 (/3) categories can the PNS be split into?
- Somatic
- Autonomic
(- Enteric)
What does somatic NS do?
Responsible for voluntary, conscious control of skeletal muscle
General function of SNS? PSNS?
SNS: fight or flight
PSNS: rest and digest
Spinal cord distribution of SNS? PSNS?
SNS: Thoracolumbar
PSNS: Craniosacral
Describe SNS and PSNS pre + postganglionic neurone length
SNS: Pre: short, Post: long (think sympathetic chain)
PSNS: Pre: long, Post: short
Describe SNS and PSNS pre + postganglionc neurotransmitters?
SNS: Pre: ACh, Post: NAd
PSNS: Pre: ACh, Post: ACh
What is normal resting membranes potential?
sits between -50 and -75 mV
Describe the main neuronal intractable + extra cellular ions
Intralcellular: K+
Extra: Na+, Cl-
describe AP. Channels?
AP begins at axon hillock => voltage gated Na channels open => Na+ influx => (reach threshold potential) => Na channels close + voltage gated K= channels open => K+ efflux
What ions are responsible for neuronal depolarisation? hyper polarisation? describe the direction of movement of the ions
Depolarisation: Na+ => into cell
Hyperpolarisation: K+ => out of cell
describe the 2 types of refectory periods
Absolute RP: Sodium channel enter inactive period after AP
relative RP: after absolute: as Na channels come out of inactivation => neurone can be excited with stimuli stronger than normal
Describe myelin in terms of resistance and capacitance
- Increase resistance
- Decrease capacitance (ability to store charge)
Is myelin found in cells of CNS or PNS?
both!
What is myelin sheath made out of ?
made of lipid-rich substance (mainly lipoprotein)
What makes up the CNS? which cranial nerves arise here?
brain + spinal cord (CN I + II (myelinated by oligodendrocytes))
what makes up the PNS?
- 12 pairs of CN
- 31 Paris of spinal nerves
- peripheral nerves
- NMJ
where is primary motor area in brain? primary sensory area?
- precentral gyrus - primary motor area
- post central gyrus - primary sensory area
what arteries form the vascular supply to the brain? (2)
- vertebral artery
- Internal carotid artery
what does the BBB do ?
blood brain barrier
- precent free flow of blood to brain
- Protect neural tissue from toxins
what is the medulla involved in maintenance of?
- muscle tone
- controls HR, breathing, BP
what is the cerebellum function ?
- refining motor control
- Motor leaning
What are ascending tracts?
the neural pathway by which sensory info from peripheral nerves =? cerebral cortex
what 2 categories of ascending tracts are there ?
- Conscious tracts
- Unconscious tracts
Name some conscious ascending tracts?
- DCML pathway, anterolateral system
Name an unconscious ascending tract?
spinocerebellar tracts
What sensory modalities does the DCML carry ?
- fine touch
- vibration
- proprioception
describe the ascent of the DCML ? where do they decussate ? 1st, 2nd, 3rd order neurones ?
1st: peripheral nerves => medulla
2nd: medulla => fibres decussate => thalamus
3rd: thalamus => primary sensory cortex
what sensory modalities does the anterolateral (spinothalamic) system carry?
- crude touch + pressure
- Pain + temp
describe the ascent of the anterolateral (spinothalamic) ? where do they decussate ? 1st, 2nd, 3rd order neurones ?
1st: arrise form peripheral sensory receptor => spinal cord =>ascend 1-2 vertebral levels => synapse at tip of dorsal horn
2nd: dorsal hormones => thalamus
3rd order: thalamus => primary sensory corte
What is the limbic system?
Part of the brain involved in behavioural + emotional responses
What are the basal ganglia?
subcortical nuclei responsible for motor control, motor learning, emotions
What are descending tracts?
they are the pathway by which motor signals are send from brain to LMN
what are the 2 categories of descending tracts?
- Pyramidal
- Extra-pyramidal
where do pyramidal tracts originate ? and control what ?
pyramidal (descending tracts): originate from cerebral cortex (voluntary control of body + face)
name some pyramidal tracts
pyramidal (descending tracts)
- corticospinal
- Corticobulbar
Name some extra-pyramidal tracts
extrapyramidal tracts (descending tracts)
- Vestibulospinal
- Reticulspinal
