Lectures 7 & 8 (ANS + brain protection & vasculature)

Question 1

Purpose of the autonomic nervous system

Answer 1

Maintain Homeostasis
controls glands and involuntary muscles (heart + smooth muscle)
also has a sensory element: referred & visceral pain + interoception
- also called visceral nervous system

Question 2

Nervous system divisions

Answer 2

• Somatic and autonomic sensory divisions
• Peripheral nervous system (loop with central NS)
• Motor division
  
  • autonomic –> parasympathetic (rest, relaxation, rumination) OR sympathetic (fight, flight, fright)
    *each organ has a dominant branch
  • somatic

Question 3

Somatic vs Autonomic motor system (neuron type + name, axon traits)

Answer 3

Somatic:
- one neuron: lower motor neuron from spinal cord to muscle (myelinated)
Autonomic:
- two neurons: autonomic ganglia from spinal cord to destination
- preganglionic (myelinated) –> postganglionic (unmyelinated)

Question 4

What happens if all ANS to the heart is stopped

Answer 4

heart rate would increase and force of contractions would increase (heart has built in pacemaker that is normally slowed by PMS)

Question 5

Organs with only one ANS input (and which input)

Answer 5

• sweat glands (SMS)
• visceral arterioles, smallest arteries (SMS almost only)
• iris sphincter, constricts pupil (PMS)
• radial muscle of the iris, dilates pupil (SMS)

Question 6

*Dominant ANS in organs

Answer 6

• heart: PMS
• blood vessels: SMS
• gastrointestinal tract: PMS

Question 7

Sympathetic vs Parasympathetic autonomic ganglia (major diffs, receptors, neurotransmitters)

Answer 7

S: short preganglionic n. –> nicotinic cholinergic receptors –> adrenergic receptors (NE & E used on effector)
P: long preganglionic n. –> nicotinic cholinergic receptors –> muscarinic cholinergic receptors (ACh used on effector)

Question 8

Purposes of Parasympathetic MS and ganglia locations

Answer 8

SLUDD
Salivation
Lacrimation (tears)
Urination
Digestion
Defecation
- ganglia close to effectors so each action can be done separately (myelination of preganglionic ns. insulates signals)

Question 9

Purposes of Sympathetic MS and ganglia locations

Answer 9

3Fs
Fight
Flight
Fright
- all ganglia are far from effectors to broadcast message through entire SMS at once
- most ganglia are connected to form a chain: sympathetic trunk ganglia

Question 10

Receptor activation time due to acetylcholine (ACh) vs norepinephrine and epinephrine

Answer 10

• short activation: ACh breaks down fast because of anticholinesterase on postsynaptic neuron/effector
• long activation: NE and E breakdown/get removed slowly in comparison

Question 11

adrenergic receptors (subtypes, purpose)

Answer 11

x-adrenoceptors
alpha 1: contract smooth muscle, mostly blood vessels
alpha 2: dont care
beta 1: tachycardia (increase HR)
beta 2: relaxes bronchioles + uterus
beta 3: dont care

Question 12

Adrenergic drugs

Answer 12

beta blockers: slow heart + constrict bronchioles unless B1 specific
beta agonists: dilate bronchioles for asthma + speed heart unless B2 specific

Question 13

3 classes of neurons in terms of signalling (name + basic purpose)

Answer 13

• afferent: deliver sensory info (up to brain)
• efferent: deliver message to effectors (down from brain)
• interneuron: all in CNS, connect neural pathways

Question 14

Afferent neuron signal path (location of neuron structures + order)

Answer 14

sensory/visceral receptors –> peripheral axon –> cell body (in dorsal root ganglion) –> central axon (dorsal root) –> axon terminal (spinal cord) –> interneuron

Question 15

Efferent neuron signal path (location of neuron structures + order)

Answer 15

interneuron –> cell body (spinal cord) –> axon (ventral root) –> effector

Question 16

Cell types in CNS

Answer 16

Grey matter:
- ependymal cells (stem cells, make CSF)
- astrocytes (blood-brain barrier)
- neurons (signals)
White matter:
- microglia (immune)
- oligodendrocytes (myelinate CNS neurons)

Question 17

Myelination (in CNS vs PNS)

Answer 17

CNS - oligodendrocytes: form several myelin sheaths on one or multiple axons
PNS - schwann cell: one myelin sheath on one axon

Question 18

NS regeneration

Answer 18

CNS - extremely limited
- neurons degenerate when injured
- glia inhibit axon growth
PNS - 1mm/day
- distal neuron degenerates
- schwann cells proliferate for support
- macrophages remove debris
- axon regenerates + remyelinates

Question 19

Brain CNS protection (layers + in between)

Answer 19

Superficial
- skull
* meningeal arteries + nerves
- periosteal dura mater (attaches to skull)
- meningeal dura mater (separates compartments)
* bridging veins
- arachnoid mater
* sub arachnoid space (CSF, cerebral vessels inside)
- pia mater
Deep

meninges: dura, arachnoid and pia mater

Question 20

Structures formed by dura mater + purpose

Answer 20

• falx cerebri: separates L & R cerebral hemispheres
• tentorium cerebelli: separates cerebrum & cerebellum
  *formed by specifically meningeal DM

Question 21

Hematomas in CNS (name, location, BV damaged, appearance)

Answer 21

• epidural h. (skull + dura) meningeal artery, dent shape
• subdural h. (dura + arachnoid) bridging veins, crescent shape
• subarachnoid h. (arachnoid + pia) circle of willis + branches, spider web shape
• intracerebral (cerebrum) BV in brain, hole shape

Question 22

what innervates the meningeal nerves?

Answer 22

CN V - trigeminal n.

Question 23

Spinal cord CNS protection (layers + in between)

Answer 23

Superficial
- vertebrae
* epidural space (fat + veins)
- dura
- arachnoid
- pia
Deep

Question 24

Lumbar punctures (names + location)

Answer 24

• Epidural: collect epidural fat from epidural space
• Spinal tap: collect CSF from subarachnoid space, done below L1/L2 at cauda equina

Question 25

Ventricles (in order of CSF flow)

Answer 25

• *lateral ventricles
• intraventricular foramina
• *third ventricle
• cerebral aqueduct
• *fourth ventricle
• central canal (in spinal cord) OR subarachnoid space
  *CSF produced here
  (replace all CSF every 6-8 hours)

Question 26

Anatomy of the lateral ventricles

Answer 26

anterior horn, posterior horn, inferior horn

Question 27

Production of CSF

Answer 27

produced in lateral, third and fourth ventricles by ependymal cells of the choroid plexus

Question 28

drainage of CSF

Answer 28

arachnoid granulations/villi transfer CSF from subarachnoid space to:
- superior or inferior sagittal sinus to
- transverse sinus to
- sigmoid sinus to
- internal jugular veins
- heart (superior vena cava)

Question 29

CSF composition

Answer 29

essentially filtered blood
- ions (high Na, Cl, K, Ca, proteins…)
- 2/3 glucose
- very few white blood cells (*no red blood cells)

Question 30

CSF flow pathology

Answer 30

Hydrocephalus: rate of CSF production is higher than CSF drainage, ventricles enlarge
*stenosis (narrowing) somewhere in the cycle

Question 31

blood supply to brain (below cerebrum)

Answer 31

leaves heart
- common carotid
- internal carotid (to circle of willis)
- external carotid (to meninges)
- vertebral arteries R & L (to circle of willis)

Question 32

Aneurysm (explanation, vessels with highest risk)

Answer 32

localized enlargement of artery caused by weakening of arterial wall
- 85% occur in circle of willis
- highest risk: anterior communicating artery
- second high risk: posterior communicating artery

Question 33

Stroke (explanation + types)

Answer 33

blood stops flowing properly
- hemorrhagic stroke: hemorrhage in BG, blood leaks into brain
- ischemic stroke: blood clot stops blood supply, area of brain dies

Question 34

Blood brain barrier

Answer 34

capillaries in brain lined by:
- endothelial cells (no gaps)
- astrocytes (cover cell)
*barrier starts to decline with age