Nervous System Flashcards

1
Q

2 Divisions of the Nervous System?

A
  1. Central Nervous System (CNS)
  2. Peripheral Nervous System (PNS)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Central Nervous System (CNS)

A
  • “command centre”
  • Brain and spinal cord
  • Processes and integrates info
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Peripheral Nervous System (PNS)

A
  • Consists of:
    1. Cranial nerves
      • To/from brain
    2. Spinal nerves
      • To/from spinal cord
  • 2 divisions of PNS:
    1. Sensory/afferent division
      • Has sensory receptors that detect stimuli (change in internal or external
        environments)
    2. Motor/efferent division
      • Nerves convey impulses away from CNS
      • Innervates (supplies nerves to) effectors = muscles and glands (endocrine or exocrine)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Relationship between CNS and PNS

A

Receptors (Detect stimuli)
↓ (PNS - afferent, Sensory neurons)
CNS (Integrate)
↓ (PNS - efferent, motor neurons)
Effector (Executes response - muscles + glands)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Peripheral Nervous System

A

Sensory

Central Nervous System

Motor

Somatic or Autonomic

Sympathetic or Parasympathetic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the 2 cell types?

A
  1. Neurons
  2. Neuroglia (glial cells)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Neurons

A
  • Conduct impulses
  • Make up CNS and PNS
  • Mostly amitotic (irreplaceable)
    • Exceptions = taste, olfaction, memory
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Structure of Neurons

A
  1. Cell body
  2. Processes from cell body
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Cell Body

A
  • Typical organelles
  • RER called - Nissl Bodies
  • Groups/clusters in CNS = nuclei (gray matter)
  • Groups/clusters in PNS = ganglia
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Processes from cell body

A
  1. Dendrites
    • Receive incoming messages and relay to cell body
  2. Axon
    • Carry 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
      2. Unmyelinated
      - No myelin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Myelinated

A
  • 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
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Neuroglia (glial cells)

A
  • Support neuron cells = can undergo mitosis (prone to cancer – brain tumor)
  • Types:
    1. CNS neuroglia
    2. PNS neuroglia
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

CNS neuroglia

A
  1. Oligodendrocytes
  2. Microglia
  3. Astrocytes
  4. Ependymal – neural epithelia
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Oligodendrocytes

A

Produce myelin around axon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Microglia

A
  • Protective
    • Become phagocytic if detect infected, dead, or
      damaged neurons (because immune cells can’t enter CNS
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Astrocytes

A
  • Surround blood capillaries to form part of blood brain barrier (BBB)
  • Help control capillary permeability
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Ependymal – neural epithelia

A
  • Line brain ventricles and central canal of the spinal cord
  • Secrete cerebrospinal fluid (CSF) and circulate it (cilia)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

PNS neuroglia

A
  1. Schwann cells
    • Form myelin around axons in PNS
  2. Satellite cells
    • Surround neuron cell bodies in ganglia – protection and support
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Neuron Classification

A
  1. Structural/Anatomical types
  2. Functional types
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Structural/Anatomical types

A
  • Based on # of cell processes off of cell body
    1. Unipolar
    2. Bipolar
    3. Multipolar
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Unipolar

A
  • 1 process that divides into two: central and peripheral
  • Peripheral end has dendrites = sensory receptors (pain, touch etc) -
    remainder is axon
  • Always sensory
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Bipolar

A
  • 2 processes: 1 axon, 1 process with dendrites
  • Sensory – retina, nose (olfaction)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Multipolar

A
  • 3 or more processes: 1 axon, many dendrites
  • All interneurons and motor neurons
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Functional types

A
  • Based on direction of impulse conduction
    1. Sensory/Afferent Neurons
    2. Interneurons
    3. Motor/Efferent Neurons
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Sensory/Afferent Neurons
- Mostly unipolar - From sensory receptors to CNS
26
Interneurons
- Within CNS (between sensory and motor) - 99% of neurons (mostly multipolar)
27
Motor/Efferent Neurons
CNS to effectors (all multipolar)
28
Neuron Junctions (Synapses)
1. Neuronal junction 2. Neuromuscular junction 3. Neuroglandular junction
29
Neuronal junction
- Neuron to neuron - Can be chemical (use neurotransmitters) or electrical (ions)
30
Neuromuscular junction
Motor neuron to skeletal muscle
31
Neuroglandular junction
Motor neuron to gland
32
Chemical Neuronal Synapses
- Most common - Structure: 1. Chemical Neuronal Synapses 2. Axon Terminal 3. Synaptic Cleft 4. Postsynaptic Neuron
33
Presynaptic Neuron
Neuron bringing impulse
34
Axon Terminal
- Within synaptic end bulbs - Inside the end bulb (presynaptic membrane) = synaptic vesicles containing neurotransmitter (nt)
35
Synaptic Cleft
Space between neurons
36
Postsynaptic Neuron
- Receives the impulse - Has postsynaptic membrane - = cell membrane of dendrites or cell body with receptor sites for nt
37
Protective Features (Central Nervous System)
1. Bone 2. Meninges 3. Cerebrospinal Fluid (CSF) 4. Blood Brain Barrier (BBB) 5. Cerebral Arterial Circle
38
Bone
Skull and vertebral column
39
Meninges
- Connective tissue around brain and spinal cord - Layers: 1. Dura mater (outer) 2. Arachnoid mater (middle) 3. Pia mater (inner)
40
Dura mater (outer)
- 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
41
Arachnoid mater (middle)
- Avascular - Subarachnoid space - Contains cerebrospinal fluid - Web-like strands of CT secure it to pia mater below - Has arachnoid granulations (brain only) - Project into dural sinuses - CSF enters granulations to return to blood
42
Pia mater (inner)
- On surface of CNS (brain and spinal cord) - Vascular
43
Meningitis
Inflammation of meninges
44
Cerebrospinal Fluid (CSF)
- Surrounds brain and spinal cord - In brain ventricles and central canal of spinal cord - Ventricles - Central canal - Cushions CNS – brain buoyant - Formed from blood plasma (similar composition) - Produced by choroid plexuses (blood capillaries) found in each ventricle
45
Ventricles
- 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, cerebrum
46
Central Canal
Space in spinal cord
47
Blood Brain Barrier (BBB)
- 2 cell types: 1. Endothelial cells (of capillaries) with tight junctions 2. Astrocytes – foot processes wrap around endothelial cells - Selectively permeable - Allows: glucose, fat soluble material - Not toxins, antibiotics, etc
48
Cerebral Arterial Circle
- Cerebral arteries form circle at base of forebrain - Circles pituitary gland and optic chiasma (where optic nerves cross) - Unites the two major blood supplies to the brain (anterior and posterior) - Provides an alternate route for blood if vessels blocked
49
Blood Flow to Brain (Posteriorly)
Vertebral Arteries ↓ Basilar Artery ↓ Posterior Cerebral Arteries
50
Blood Flow to Brain (Anteriorly)
Internal Carotid Arteries ↓ Middle Cerebral Arteries or Anterior Cerebral Arteries or Posterior Communicating Artery OR Anterior Cerebral Arteries ↓ Anterior Communicating Artery (Joins two anterior cerebral arteries)
51
Blood Return from the Brain (Posteriorly)
Cerebral Arteries ↓ Capillaries ↓ Cerebral Veins ↓ Dural Sinuses ↓ Superior Vena Cava
52
Brain (Central Nervous System)
1. Forebrain 2. Diencephalon 3. Midbrain 4. Hindbrain 5. Functional Systems
53
Forebrain (Cerebrum)
- Lobes 1. Frontal 2. Temporal 3. Parietal 4. Occipital 5. Insula – deep to temporal lobe - Surface Features 1. Fissures = deep grooves 2. Gyri = ridges 3. Sulci = shallow grooves (separate gyri)
54
Fissures = deep grooves
1. Longitudinal fissure - Separates right and left cerebral hemispheres 2. Transverse fissure - Separates cerebellum and cerebrum 3. Lateral fissure - Separates temporal lobe from rest of cerebrum
55
Gyri = ridges
- Examples: - Postcentral gyrus in parietal lobe - Precentral gyrus in frontal lobe
56
Sulci = shallow grooves (separate gyri)
- Example: - Central sulcus – between frontal and parietal lobes
57
What are the 3 layers of Forebrain
1. Cerebral cortex 2. Tracts (white matter) 3. Basal nuclei
58
Cerebral cortex
- 2 – 4 mm thick, gray matter - Has functional areas: 1. Motor areas 2. Sensory areas 3. Association Areas 4. Others
59
Motor Areas (Cerebral Cortex)
- All in frontal lobe - Control skeletal muscle movement - 3 regions: 1. Primary motor area (precentral gyrus) 2. Premotor area 3. Broca’s area (motor speech
60
Sensory Areas (Cerebral Cortex)
1. General sensory area (pain, touch, temp, pressure) - Postcentral gyrus in parietal lobe 2. Vision - Occipital lobe 3. Auditory and olfaction - Temporal lobe 4. Taste and visceral sensation (e.g. full bladder) - Insula
61
Association areas (Cerebral Cortex)
- Recognize info from memories - Parietal, occipital, temporal lobes
62
others (Cerebral Cortex)
- Memory - Temporal lobes - Conscious intellect (personality, learning, ideas, judgement, etc.) - Prefrontal cortex
63
Tracts (white matter)
- Types: 1. Association tracts 2. Commissural tracts 3. projection tracts
64
Association tracts
From gyrus to gyrus in same hemisphere
65
Commissural tracts
- From gyrus to gyrus in opposite hemispheres - E.g. corpus callosum
66
Projection tracts
Run vertically (brain to spinal cord / spinal cord to brain)
67
Basal nuclei
- Paired masses of gray matter (within white matter) - Control skeletal muscle movement
68
Diencephalon
- All gray matter 1. Thalamus - 2 lobes connected by intermediate mass (bridge through 3rd ventricle) - Relay station for impulses coming to cortex (from spinal cord) 2. Hypothalamus - Inferior to thalamus, above pituitary - Major regulator of the internal environment (visceral control) - E.g. blood pressure, heart rate
69
Midbrain
- Connects pons and diencephalon - Contains cerebral aqueduct - Anterior portion = cerebral peduncles (projection tracts) - Posterior portion = 4 nuclei = corpora quadrigemina - 2 superior colliculi - Visual reflexes - 2 inferior colliculi - Hearing
70
Hindbrain
1. Pons 2. Medulla 3. Cerebellum
71
Pons
- Anterior to cerebellum - Tracts between brain and spinal cord, and tracts to/from cerebellum - Pontine respiratory centres
72
Medulla
- Inferior to pons - Ends at foramen magnum - 2 bulges (called pyramids) = large motor tracts (= part of corticospinal tracts) - Just above spinal cord = decussation (crossover) of pyramids - 3 vital centres in medulla: 1. Cardiac 2. Vasomotor (blood vessels) 3. Respiratory - Several non-vital centres for swallowing, sneezing, vomiting NOTE: Brain Stem = midbrain, pons, medulla
73
Cerebellum
- Posterior to pons/medulla - Has folds similar to gyri = folia - Cortex = gray matter - Arbor vitae (deep to cortex) = white matter - Coordinates skeletal muscle contraction - Balance, posture
74
Functional Systems
1. Limbic System 2. Reticular Formation
75
Limbic System
- Nuclei in cerebrum and diencephalon - Regulates emotions (laughing, crying, etc.) - Contains areas involved in memory (memories evoke emotional responses
76
Reticular Formation
- Nuclei in brain stem - Cortex, thalamus, and hypothalamus involved - (together form RAS = Reticular Activating System) - Regulates alertness and attention - Filters stimuli and only sends new/unusual signals to other brain areas - Sleep results when inhibited - If damaged = coma
77
Spinal Cord Structure Overview
- Foramen magnum to L1/L2 (conus medullaris) - Nerves continue down from spinal cord through vertebral foramina as cauda equina (horse’s tail) - Exit at intervertebral foramina - Filum terminale - Is a connective tissue extension of pia mater that anchors conus medullaris of spinal cord to coccyx - Location where CSF samples taken
78
Spinal Cord Cross-Sectional Structure
1. Anterior median fissure and posterior median sulcus 2. Central canal 3. Gray Matter 4. White Matter
79
Anterior median fissure and posterior median sulcus
Separate cord into right and left halves
80
Central canal
Contains CSF
81
Gray Matter
- Cell bodies and dendrites of motor neurons and interneurons - H-shaped: - Cross bar = gray commissures - Horns 1. Dorsal horn = sensory 2. Lateral horn = motor 3. Ventral horn = motor
82
White Matter
- Myelinated axons containing ascending (sensory) or descending (motor) tracts - Forms columns: 1. Dorsal column 2. Lateral column 3. Ventral column
83
Functions of the Spinal Cord
- Sensory and motor impulses - Produces reflexes - Fast, predictable, automatic responses to changes in environment - E.g. withdrawal reflex
84
Structures of the Peripheral Nervous System
1. Cranial Nerves 2. Spinal Nerves 3. Cross Section of a Nerve
85
Cranial Nerves Names
- 12 pairs total 1. Olfactory 2. Optic 3. Oculomotor 4. Trochlear 5. Trigeminal 6. Abducens 7. Facial 8. Vestibulocochlear 9. Glossopharyngeal 10. Vagus 11. Accessory 12. Hypoglossal
86
Sample Mneumonic Devices
Oh Once One Takes The Anatomy Final Very Good Vacations Are Had
87
Brain Regions → Cranial Nerves I-XII
- Forebrain 1. Olfactory 2. Optic - Midbrain 3. Oculomotor 4. Trochlear - Pons 5. Trigeminal 6. Abducens 7. Facial 8. Vestibulocochlear - Medulla Oblongata 9. Glossopharyngeal 10. Vagus 11. Accessory 12. Hypoglossal
88
Cranial Nerves
- 2 pairs = only sensory neurons - I and II - 1 pair = mainly sensory neurons - VIII - 9 pairs = mixed nerves - Carry both sensory and motor neurons - Motor neurons have cell bodies in brainstem nuclei - Sensory neurons have cell bodies in ganglia of PNS - E.g. trigeminal nerve (V) - Motor function = chewing - Sensory function = conveys general sensations (touch, pressure, pain, temperature) from face to CNS
89
Spinal Nerves
- 31 pairs = all mixed nerves - 8 cervical - 12 thoracic - 5 lumbar - 5 sacral - 1 coccygeal - Exit via intervertebral foramina (except 1st – between atlas and occipital) - Each has 2 points of attachment to spinal cord: 1. Dorsal Root 2. Ventral Root
90
Dorsal Root
Sensory neurons; cell bodies in dorsal root ganglion
91
Ventral Root
Autonomic and somatic motor neurons; cell bodies in ventral or lateral horn
92
What is Spinal Nerve?
- Joining of dorsal and ventral roots - Immediately divide into branches = rami: 1. Dorsal ramus - Innervate skin and muscles of the back 2. Ventral ramus - Forms thoracic nerves (T2 – T12) ) OR further branch and join up forming nerve plexuses (= nerve network 3. Rami communucantes - Connect ventral ramus (spinal nerve) to sympathetic trunk - Contain autonomic nerve fibres (neurons
93
Spinal Nerve Plexuses
1. Cervical 2. Brachial 3. Lumbar 4. Sacral
94
Cervical
- Spinal Nerves: - C1 - C5 - Important Nerves: - Phrenic
95
Brachial
- Spinal Nerves: - C5 - C8, T1 - Important Nerves: - Axillary, Radial, Ulnar, Median, Musculocutaneous
96
Lumbar
- Spinal Nerves: - L1 - L4 - Important Nerves: - Femoral
97
Sacral
- Spinal Nerves: - L4 - S4 - Important Nerves: - Sciatic → divides into: Tibial + Common Fibular
98
Cross section of a nerve
- CT wrappings: 1. Epineurium - Around whole nerve 2. Perineurium - Around fascicles 3. Endoneurium - Around axon and myelin
99
Sensory (Afferent) Division
1. Receptors 2. First Order Neurons
100
Receptors
- Detect changes in environment - Classified by: 1. Location 2. Type of stimulus received 3. Structure of Receptor (general senses only)
101
Location
1. Exteroceptors - Stimulus in external environment = receptors at body surface (e.g. touch, special senses) 2. nteroceptors - Stimulus in internal environment (in viscera, blood vessels, etc.) 3. Proprioceptors - Located in joints, skeletal muscles, etc. - Monitor body position (stretch receptors, muscle spindles ) – balance and movement
102
Type of stimulus received
1. Mechanoreceptors - Mechanical stimuli (e.g. pressure, touch, hearing) 2. Thermoreceptors - Temperature 3. Chemoreceptors - Chemical 4. Photoreceptors - Light 5. Nociceptors - Pain
103
Structure of Receptor (general senses only)
1. Free nerve endings - Terminal dendrites of unipolar sensory neurons - E.g. pain, root hair plexus 2. Encapsulated nerve endings - Terminal dendrites enclosed in CT - E.g. Meissner’s and Pacinian corpuscles
104
First Order Neurons
- Unipolar neuron attached to or associated with receptor (may be encapsulated) - Axon travels in cranial/spinal nerves to CNS - Cell bodies in: 1. Sensory ganglia of cranial nerves 2. Dorsal root ganglia of spinal cord - Axon terminals in: 1. Brain 2. Dorsal horn of spinal cord
105
Motor (Efferent) Division
- 2 subdivisions 1. Somatic 2. Autonomic
106
Somatic
- Effector = skeletal muscle - Consists of lower motor neurons: - = single multipolar neuron 1. cell bodies in ventral horn of spinal cord to effector 2. cell bodies in motor nuclei of brainstem to effector (e.g. facial motor nucleus for CN VII)
107
Autonomic
- Effector = smooth muscle, cardiac muscle, glands - 2 successive multipolar neurons from CNS to effector: 1. Preganglionic neuron 2. Postganglionic neuron
108
Preganglionic neuron
- Myelinated - Cell body in brain stem or lateral horn of spinal cord
109
Postganglionic neuron
- Unmyelinated - Cell body in autonomic ganglion (outside CNS)
110
2 subdivisions of Autonomic
1. Sympathetic (SNS) 2. Parasympathetic (PSNS)
111
SNS
1. Cell Body of Preganglionic neuron - Lateral Horn (of T1 - L2) 2. Autonomic Ganglia - Trunk ganglia (either side of vertebral column) OR collateral ganglia (close to large abdominal arteries) 3. Postganglionic neurons - Long axons 4. Functions - Fight or flight 5. Exit CNS (nerves) - Mainly as thoracic nerves
112
PSNS
1. Cell Body of Preganglionic neuron - Brain Stem & S2 - S4 2. Autonomic Ganglia - Terminal ganglia (at or in the organ/effector wall) 3. Postganglionic neurons - Short axons 4. Functions - Rest & digest 5. Exit CNS (nerves) - Mainly (80%) via vagus nerve (cranial nerve X)
113
Nervous System Pathways
1. Ascending Pathway (Sensory) 2. Descending Pathway (Motor):
114
Ascending Pathway (Sensory)
- Conducts impulses from general sense receptors into brain - 3 successive neurons from receptor to cortex: 1. First Order Neuron 2. Second Order Neuron 3. Third Order Neuron - Axons of 1st and 2nd order neurons form ascending spinal tracts: 1. Dorsal (Posterior) Column Pathway/Tract 2. Spinothalamic Pathway/Tracts 3. Spinocerebellar Pathway/Tracts
115
First Order Neuron
Receptor to spinal cord (PNS)
116
Second Order Neuron
- Interneuron, multipolar (CNS) - Cell body in dorsal horn of spinal cord or medulla (CNS) - Decussates (crosses over) in medulla
117
Third Order Neuron
- Interneuron, multipolar - Cell body in thalamus – impulses to postcentral gyrus (sensory cortex) (CNS)
118
Dorsal (Posterior) Column Pathway/Tract
- Sensations can be precisely located (touch) - Receptors = free nerve endings, Meissner’s etc.
119
Spinothalamic Pathway/Tracts
- Non-specific, difficult to localize - Receptors = temperature, pain
120
Spinocerebellar Pathway/Tracts
- Ascending tracts from spinal cord to cerebellum - Receptors = proprioceptors - 2nd order neuron directly to cerebellum (no 3rd order) - No conscious perception - No decussation
121
Descending Pathway (Motor)
- Conduct impulses from brain to effector - 2 neuron pathway: 1. Upper Motor Neuron (CNS) 2. Lower Motor Neuron (cell bodies in CNS and axons in PNS) - Axons of upper motor neurons form descending spinal tracts: 1. Corticospinal Tracts 2. Indirect Tracts
122
Upper Motor Neuron (CNS)
- Multipolar interneurons - Cell bodies in cortex or brainstem nuclei
123
Corticospinal Tracts
- Cell bodies in cerebral cortex - Tracts mainly decussate in medulla
124
Indirect Tracts
- Cell bodies in brainstem nuclei - Receive impulses from motor cortex, basal nuclei, cerebellum