:)))))) Flashcards
what are the majority of cells in NS?
glial cells
what do glial cells do in PNS? & CNS?
- astrocytes: main cell type. star like process. control environment around neurons. form blood brain barrier: prevents substances entering and damaging cells.
- oligodendrocytes: cells put out processes that wrap around neighbouring axons. can myelinate multiple axons
- ependymal cells: lining cells of ventricular system. they are epithelial boundary that regulate the movement of cerebral spinal fluid in/out brain tissue and ventricle system.
- macroglial cells - only active when pathogens come into brain - turn into macrophages
PNS
- Schwann cells: myelinate one axon
- Satelitte Cells: (similar role as astrocytes) - modulate environment around neuronal cell body
what are the arterires like in the brain?
- arteries are thinner walled - less smooth muscle.
- can be distended (swollen due to pressure from inside; bloated)
what type of cell is this?
astrocyte
which is this?
role?
where?
ependymal cells
- function: ciliated. move cerebral spinal fluid (CFS) around CNS.
- located: lining central canal of spinal cord and ventricular system
which parts of the brain code for the following?
- memory:
- emotion:
- coordination of complex movement:
- language comprehension and production:
- processing of multisensory information:
- detection of visual stimuli:
- memory: hippocampus
- emotion: frontal lobe
3. coordination of complex movement: cerebellum
- language comprehension and production: auditory area: temporal lobe. speeach production: frontal lobe
- processing of multisensory information: primary somatosensory cortex
- detection of visual stimuli: occipital lobe
where is the starting point of cranial nerves?
how many pairs of cranial nerves are there?
which cranial nerves exit and enter the answer to 1.? what are there functions?1
- brainstem!!
- 12 pairs of cranial nerves -
- cranial nerves III - XII -> provide main motor and sensory innervation to face and neck
what is the reticular formation?
where?
which cranial nerves DONT come from brain stem?
Cranial Nerve 1: Olfactory Nerve
Cranial Nerve 2: Optic Nerve
role of each?
- CN III
- CN VII
- CN IX
- CN X
Parasympathetic Nervous System
- CN III: pupil size and lens focusing
- CN VII: saliva focusing, tear production
- CN IX: saliva production
- CN X: everything else (90% of parasympathetic nervous system)
where does brain stem end / spinal cord start?
where does spinal cord end?
whats after spinal cord?
- brain stem continues till about C2/C3.
- here it turns into spinal cord: goes till to L1 vert.
- then forms cauda equina. typically L1-L5
what do spinal cord white matter tracks code for?
ascending tracts:
- sensory: periphery to CNS (goes up to brain).
- located on outside
a) pain, temp, position,
descending tracts:
- motor - comes down from brain
- further in
what is brown colour in brown adipose tissue samples from?
- brown colour from high levels of cytochrome oxidase in mitochondria
what is cartilage made from?
is it vascular ?
cells: chondrocytes, ECM = 95%.
contains:
- avascular: ECM crucial for surivial
- glycosaminoglycans (GAGs)
- few type II collagen fibres
how is cartilage made? (2)
- chondroblasts (immature chondrocytes): produce and deposit collagen type II and ECM.
- chondroblasts become trapped within matrix spaces (lacunae): become chondrocytes
2 mechanisms for formation of cartilage:
a) Interstitial growth - chondrocytes grow and divide and lay down more matrix inside the existing cartilage f
b) appositional growth: undiff. cells at the surface of the cartilage (perichondrium)
where do you find hyaline, fibro and elastic cartilage?
Hyaline - most common, found in the ribs, nose, larynx, trachea. Is a precursor of bone.
Fibro- is found in invertebral discs, joint capsules, ligaments.
Elastic - is found in the external ear, epiglottis and larynx.
which type of collagen is found in fibrocartilage?
type I collagen. 3
which type of cartilage doesnt have a perichondrium?
fibrocartilage
what are the three archictetural patterns of bone?
what supplies blood to bones?
what connects ^?
1. circumferential outer layer
- concentric - forms the osteons (looks like circles)
- interstitial - between 1 & 2.
also have:
- harversion canal in the osteons: tubes where BV fill
- volkmann’s canals: connect the haversion canals
what are the three mane types of bone cells?
- osteoblasts: bone formation - immature bone cells
- osteocytes: bone maintenance -
- osteoclasts: - bone resorption / remodelling. multi nucleited (osteoclast, large multinucleated cell responsible for the dissolution and absorption of bone. Bone is a dynamic tissue that is continuously being broken down and restructured in response to such influences as structural stress and the body’s requirement for calcium)
describe the intra and extracellular ion concentrations that sets up the cells resting membrane potential.
- Na+ greater outside cell
- K+ greater inside cell
- A- (proteins) greater inside cell
= creates a resting membreane potential: +ve outside, -ve inside = -70mV
how do cells get over asymmetrical ionic charge distribution caused by proteins not being permeable?
- *Active Na/K diffusion**
- 3Na+ from intracellular to extracellular
- 2K+ from extracellular to intracelluar
effects:
- high Na+ conc in extracellular space, low intracellular
- high K+ conc in intracellular space, low extracellular
32- results in +ve extraceullar space c.f. intracellluar space: sets up resting membrane potential
- *membrane permeability:**
- *-** - K+ (50:1 difference): more +ve charged ions move out of the cell: sets up more -ve charge inside cell. neuron plasma membrane is 50-100 times more permeable to K+ than Na=
- resting membrane potential of cell: approx. -70mV
what is the nernst equation?
the potential across the cell membrane at which the net diffusion of ions across thecell membrane due to conc. gradient stops
equation: Em= 61.5 log ([C]0/[C]I)
what is cell resting membrane potential a consequence of?
- concentration gradients of ions across the plasma membrane
AND
- relative ion impermeabilities of the membrane
which cell types are voltage dependent ion channels found in?2
nerve cells
muscle cells (skeletal, cardiac, smooth)
describe the structure of Na+ voltage sensitive channels
how does it work?
2 channels:
- activation gate: (in middle of channel)
a) closed in resting state
b) bridge in middle of channel stops Na+ being able to enter cell
- inactivation gate: (located intracellularly)
a) open in resting state
works by:
open in response to depolarisation:
- activation gate
a) v fast opens due to depol
-inactivation gate
a) closes due to depol
b) closes slowly after depol
= Na+ go into cell - makes cell more postivie
after repolarisation, channels return to resting
explain whats going on at resting of AP - what reeastblishes resting membrane p?
- all Na and K+ pumps closed (activation gate of Na ion channels closed, inactivation gate of Na channels are open)
- Na/K ATPase pump, leak channels and proteins establish resting membrane potential
which part of AP is postive feedback and whch is negative feedback?
postive feedback: depolarisation
negative feedback: repolarisation
what do local anaesthetics do?
- bind to open Na+ channel: become inactivated
- physically prevent Na+ reopening and generating AP: drugs stablises inactive state
- cant depolarise cell
- pain fibres cant send pain to brain
name for jumping of conduction from node of ranvier to node of ranvier?
AP jumps from one to node to the next: aka saltatory conduction
why do we have different conduction velocities and how do they achieve this?
what are the names of different size fibres with different speeds?
fastest conduction velocities have widest axon diameter and myelination:
(size goes down in order - see photo)
Aα fibres are the fastest: motor neurons, muscle spindles, golgi tendon organs
Aβ fibres: touch / mechanical pressure:
Aδ fibres: pain (fast), temp
C fibres: pain (slow), temp and itch. unmyelinated
what is summation?
addition of excitatory and inhibtory signals
name 4 important NT that are collectively called monoamines
where each expressed?
adrenaline: fight or flight. PNS
noradrenaline: concentration and arousal. PNS. undersupply can depress mood
dopamine: pleasure, learning attention and momevent. CNS. XS: schizophrenia. depleted: Parkinsons
serotonin: mood, hunger and arousal. CNS and gut. depression
= collectively known as monoamines
name three amino acid NTs?
name a peptide NT
amino acids:
gaba: calming. major inhib NT. CNS. undersupply: seizures, tremors
glutamate: memory. major excitatory NT. XS: oversupply: overstimlate brain - migraines
glycine: major inhibitory NT in spinal cord
peptides:
endorphins: euphoria
which of gaba and glutamate are excitatory / inhibitory?
gaba: inhibtory
gluatamate: excitatory
what is temporal summation?
what is spatial summation?
temporal summation
- post synaptic potentials at same syanpse (A&A) occur in rapid succession
- first potential doesnt have time to dissipate: next potentials add to previous once
spatial summation
- multiple postsynaptic potentials from different synapses (A+B) occur same time and add
- alone, EPSP not strong enough to cause AP. reinforce each other = AP.
which NT is most common in brain?
glutamate !!
which type of synapse is the most common?
axodendritic: pre - post synaptic cleft
how do inhibitory post synpatic potentials work?
give an example of direct and indirect inhibitory post synaptic pontetial
- K+ permeability increased OR increased Cl- perm.
- *indirect: Muscarinic ACh receptor:**
- G-protein activated
- acts via 2nd messenger
- indirectly opens K+ channel
- *direct: GABAA receptor:**
- opens Cl- channel
BOTH: = hyperpolarisation
which ACh receptor is ionotropic and which is metabotropic?
iontropic ACh receptor: nicotonic receptors. (PNS, bit in CNS)
metabotropic ACh receptor: muscarinic receptor
which is the main excitatory NT in CNS?
use one or both type of receptors?
how can the ionotropic receptors be classified?
- glutamate
- both ionotropic and metabatropic receptores
- 3 ionotropic receptors classified as:
a) NMDA
b) Non-NMDA
i) AMPA
ii) Kainate
describe basic overview of glutamate G-protein coupled receptor response?
G-protein coupled receptor –> G protein comple (intracellular) –> enzyme (+/-) –> 2nd messenger
its the second messenger which causes varied responses:
- e.g. cAMP released: inhibitory
- IP3 or DAG released: excitatory
how does receptor modulation by NTs occur?
receptor modulation by other NTs:
- NTs influence accumulation of opposite NTs on post-synaptic membrane
e. g. ionotropic glutamate receptor fires excitatory response BUT also feedback to GABA receptor and causes to disperse (and vice versa)
causes a balance of inhib and excitatory systems.
what are the three main type of 2nd messengers of GPCR?
- hydrophilic water soluble (IP33, cAMP, Ca2+)
- hydrophobic water insoluble (DAG and PIP3)
- gases (NO, CO and ROS)
what are:
a) tonic adaptation
b) phasic adaptation
to stimuli?
Tonic receptors adapt slowly and inform about the presence and strength of a stimulus.
phasic - rapid adaption
give skin sensory receptors example that do
rapidly adapting
slowly adapting
rapidly adapting: Meissner corpuscles (light touch), Pacinian corpsucles (vibration)
slowly adapting: Merkel cells (pressure, texture), Ruffini endings (stretching of skin)
what do the 4 skin receptors detect?
Meissner corpuscles – Light touch
- Merkel cells – Pressure, texture
- Pacinian corpuscles – Vibration •
Ruffini endings – Stretching of skin
what do enteric neurons use as their major NT?
Ach, NO and seratonin
where do the autonomic output signals go via from the hypothalamus?
what does hypothalamus maintain homeostasis of ?
integration centre for ANS: hypothalamus:
- Receives sensory stimuli and visceral sensations from the periphery (input signals, afferent fibers)
- output signals go via medulla oblongata and pituitary to target organs (smooth & cardiac muscles, exocrine glands)
- maintains homeostasis of: BP, body temp and electrolyte balance
where in the spinal cord do the neurons leave from for SNS?
- which part of the spinal cord?
where are cell bodies of SNS found?
where do SNS preganglionic fibres synapse (3)
thoracolumbar (T1-L2) outflow:
- cell bodies in lateral horn of the spinal cord
- (short preganglionic nerves, long post-ganglionic nerves)
preganglionic fibres synapse in:
i) _paravertebral ganglia of the sympathetic chain: (T1-4 sympathetic chain).
ii) p_revertebral ganglia: T5-L2 the nerve fibres from the spinal cord pass through the sympathetic ganglia and synapse outside the sympathetic trunk (prevertebral or collateral ganglia).)
iii) chromaffin cells of the adrenal medulla (pass independently)
where are sympathetic postganglionic neurons that innervate abdominal viscera located?
what do they both synapse at?
in prevertebral ganglia:
T5-T9 = great splanchnic nerve (The greater splanchnic nerve is formed from the preganglionic fibres of T5–T9, which traverse the paravertebral ganglion and terminate in the coeliac and superior mesenteric ganglia) Function: Sympathetic supply of foregut and adrenal medulla
T10-T12 = lesser splanchnic nerve
Function: Sympathetic supply of midgut
BOTH SYNAPSE ON POSTGANGLIONIC NEURONS IN THE CELIAC GANGLION
- postganglionic fibres innervate smooth muscle and glands in stomach, small intestines, liver, kidney and spleen
which sympathetic preganglionic fibres pass through the sympathetic chain and travel in lumbar splachnic nerves? what do they synapse on?
- L1-L2 sympathetic preganglionic fibres
- Synapse on postganglionic neurons in inferior mesenteric ganglion: innervates colon, rectum, bladder and genital
how is the PNS organised?
do nerve fibres orginate at differe or same levels of spinal cord?
most organs recieve dual or single innervation?
Craniosacral outflow:
a) Cranial nerves: III, VII, IX, X: organs in head
b) Sacral nerves: S2-S4: rectum, bladder and genitals
2. nerve fibres originate different levels of spinal cord
3. dual innervation
How is the enteric NS organised?
what does ENS control?
organisation: two major plexuses:
a) Myenteric plexus:
located: between circular and long. muscle layers
function: motility
b) submucosal plexus:
located: between submucosal and circular muscle layer
function: controls secretion and muscle function in the mucosal layer
controls: motility of intestine, exchange of fluids across mucosal surface, blood flow and secretion of gut hormones (The enteric nervous system (ENS) controls effector systems of the digestive tract, consisting of the musculature, secretory glands, and blood vessels)
