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Anatomy > Topic 19 -Nervous System Histology and protective features > Flashcards

Topic 19 -Nervous System Histology and protective features Flashcards

1
Q

2 divisions of nervous system

A

Central Nervous system

Peripheral Nervous System

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2
Q

Central Nervous System

A
  • command centre
  • brain + spinal cord
  • processes + integrates information
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3
Q

Peripheral Nervous System

  • consists of:
A

a) cranial nerves to/ from brain

b) spinal nerves to/ from spinal cord

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4
Q

2 divisions of peripheral nervous system

A

a) sensory/afferent division
- has sensory receptors that detect stimuli (changes in the internal or external environments
- nerves convey impulses toward CNS

b) motor/efferent division
- nerves convey impulses away from CNS
- innervates (supplies nerves to) effectors = muscles + glands (endocrine or exocrine)

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5
Q

relationship between CNS and PNS

A

Receptors detect stimuli -> PNS afferent (sensory) neurons -> CNS integrates -> PNS efferent (motor) neurons -> effector muscle or gland

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6
Q

Nervous system organization

A

stimulus -> sensory (PNS) -> CNS -> motor (PNS) -> somatic (skeletal muscle) OR autonomic (smooth and cardiac muscle, glands) -> sympathetic OR parasympathetic

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7
Q

Cell types of nervous system

A

Neurons

Neuroglia

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8
Q

Neurons

A
  • conduct impulses
  • make up CNS + PNS
  • mostly amitotic (irreplaceable)
    exceptions = taste, olfaction, memory
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9
Q

Neuron structure

A

a) cell body
- typical organelles
- RER called Nissl bodies
- groups/clusters in CNS = nuclei (gray matter)
- groups/clusters in PNS = ganglia
b) processes from cell body:
i) dendrites
- receive incoming messages + relay to cell body
ii) axon
- carries impulses away from cell body - axon hillock - where axon meets cell body
- axon terminal → typically branched with synaptic end bulbs (enlarged tips)
- may be:
① myelinated – wrapped in many layers of cell membrane from Schwann cells (PNS) or oligodendrocytes (CNS) - electrical insulation - gaps in myelin sheath are called nodes of Ranvier - myelinated axon bundles in: - CNS = tracts (white matter) - PNS = nerves
② unmyelinated - no myelin

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10
Q

Neuroglia (glial cells)

types

A
  • support neurons = can undergo mitosis (prone to cancer – brain tumour)
    CNS neuroglia
    PNS neuroglia
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11
Q

CNS neuroglia

A

i) oligodendrocytes - produce myelin around axon
ii) microglia - protective ⇒ become phagocytic if detect infected, dead or damaged neurons (because immune cells can’t enter CNS)
iii) astrocytes
- surround blood capillaries to form part of blood brain barrier (BBB)
- help control capillary permeability
iv) ependymal cells - neural epithelium - line brain ventricles + central canal of spinal cord
- secrete cerebrospinal fluid (CSF) + circulate it (cilia)

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12
Q

PNS neuroglia

A

i) Schwann cells - form myelin around axons in PNS
ii) Satellite cells - surround neuron cells bodies in ganglia
- protection and support

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13
Q

Neuron types based on structural/anatomical

A
  • based on number of processes coming off cell body
    a) unipolar
  • 1 process that divides into two: central + peripheral
  • peripheral end has dendrites = sensory receptors (pain, touch etc)
  • remainder is axon
  • always sensory
    b) bipolar
  • 2 processes: 1 axon, 1 process with dendrites
  • sensory ⇒ retina, nose (olfaction
    c) multipolar
  • 3 or more processes: 1 axon, many dendrites
  • all interneurons + motor neurons
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14
Q

Functional types of neurons

A
  • based on direction of impulse conduction
    a) Sensory/Afferent neurons
  • mostly unipolar
  • from sensory receptors to CNS
    b) Interneurons
  • within CNS (between sensory + motor)
  • 99% of neurons (mostly multipolar)
    c) Motor/Efferent neurons
  • CNS to effectors (all multipolar)
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15
Q

Neuronal junctions

A

1) Neuronal junction:
- neuron to neuron
- can be chemical (use neurotransmitters) or electrical (ions)
2) Neuromuscular junction:
- motor neuron to skeletal muscle cell
3) Neuroglandular junction:
- motor neuron to smooth or cardiac muscle, or a gland

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16
Q

Chemical Neuronal Synapses:

A

1) Presynaptic Neuron
- neuron bringing impulse
- has axon terminal with synaptic end bulbs
- inside end bulb = synaptic vesicles containing neurotransmitter (nt)
- presynaptic membrane (cell membrane facing space)
2) Synaptic Cleft
- space between neurons
3) Postsynaptic Neuron
- receives the signal
- has postsynaptic membrane = cell membrane of dendrites or cell body with receptors for nt

17
Q

Central Nervous system Protective features

A 
Bone
meninges 
Cerebrospinal fluid 
Blood-brain barrier 
Cerebral arterial circle
18
Q

bone

A

skull and vertebral column

19
Q

Meninges

A
  • CT around brain + spinal cord
  • layers:
    dura mater
    arachnoid matter
    Pia mater
20
Q

Meninges: dura mater

A
  • brain = 2 fused layers
  • separated in some places to form spaces = venous (dural)
    sinuses - contain blood
  • spinal cord - 1 layer
  • deep to dura mater = subdural space
  • filled with ISF
  • superficial to dura mater = epidural space (spinal cord only)
  • filled with fat, blood vessels, CT etc
21
Q

Meninges: arachnoid mater

A
  • avascular
  • subarachnoid space
  • contains cerebrospinal fluid (CSF)
  • web-like strands of CT secure it to pia mater (below)
  • has arachnoid granulations (villi) (brain only)
  • project into dural sinuses
  • CSF enters granulations (villi) to return to blood
22
Q

Meninges: pia mater (inner)

A
  • on surface of CNS (brain and spinal cord)

- vascular

23
Q

meningitis

A

inflammation of meninges

24
Q

Cerebrospinal fluid

Where is it

Formed by?

Produced by?

A
  • surrounds brain + spinal cord
  • in brain ventricles + central canal of spinal cord
  • cushions CNS – brain buoyant
  • formed from blood plasma (similar composition)
  • produced by choroid plexuses (blood capillaries) found in each ventricle
25
Q

ventricles of brain

A
  • spaces inside brain (filled with CSF)
  • 2 lateral ventricles (1st and 2nd) – in cerebrum
  • 3rd ventricle - in diencephalon
  • 4th ventricle - surrounded by pons, medulla oblongata, cerebellum
26
Q

Central canal

A

space in spinal cord`

27
Q

Circulation of CSF

A

Choroid Plexuses -> Lateral ventricles 1st and 2nd OR 3rd ventricle OR 4th ventricle

lateral ventricles 1st and 2nd -> interventricular foramina -> 3rd ventricle -> cerebral aqueduct -> 4th ventricle -> median (1) and lateral (2) aperatures -> subarachnoid space (of brain and spinal cord) -> arachnoid villi -> dural sinus (venous blood) -> internal jugular veins -> heart -> arterial blood -> choroid plexus

28
Q

Blood brain barrier

Where is it not in brain?

A
  • 2 cell types:
    a) endothelial cells (of capillaries) with tight junctions
    b) astrocytes - foot processes wrap around endothelial cells
  • selectively permeable
  • allows: glucose, fat soluble material to cross - not toxins, antibiotics etc
  • in most parts of brain except:
  • posterior pituitary, hypothalamus, vomiting centre
29
Q

Cerebral arterial circle

A
  • cerebral arteries form circle at base of forebrain
  • circles pituitary gland and optic chiasma (where optic nerves cross)
  • unites the 2 major blood supplies to the brain (anterior and posterior)
  • provides an alternate route for blood if vessels blocked
30
Q

Blood flow to brain posteriorly means in circle

A

vertebral arteries -> basilar arteries -> posterior cerebral arteries

31
Q

Blood flow to brain anteriorly means in circle

A

internal carotid arteries -> middle cerebral arteries OR posterior communicating artery OR anterior cerebral arteries -> anterior communicating arteries

32
Q

Blood return from brain

A

Cerebral arteries -> capillaries -> cerebral veins -> dural sinuses -> superior vena cava

Anatomy (26 decks)

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