FINAL EXAM - BIOL 1410 > Nervous System > Flashcards

Nervous System Flashcards

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1
Q

2 Divisions of the Nervous System?

A
  1. Central Nervous System (CNS)
  2. Peripheral Nervous System (PNS)
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2
Q

Central Nervous System (CNS)

A
  • “command centre”
  • Brain and spinal cord
  • Processes and integrates info
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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)
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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)

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5
Q

Peripheral Nervous System

A

Sensory
↓
Central Nervous System
↓
Motor
↓
Somatic or Autonomic
↓
Sympathetic or Parasympathetic

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6
Q

What are the 2 cell types?

A
  1. Neurons
  2. Neuroglia (glial cells)
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7
Q

Neurons

A
  • Conduct impulses
  • Make up CNS and PNS
  • Mostly amitotic (irreplaceable)
    • Exceptions = taste, olfaction, memory
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8
Q

Structure of Neurons

A
  1. Cell body
  2. Processes from cell body
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9
Q

Cell Body

A
  • Typical organelles
  • RER called - Nissl Bodies
  • Groups/clusters in CNS = nuclei (gray matter)
  • Groups/clusters in PNS = ganglia
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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
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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
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12
Q

Neuroglia (glial cells)

A
  • Support neuron cells = can undergo mitosis (prone to cancer – brain tumor)
  • Types:
    1. CNS neuroglia
    2. PNS neuroglia
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13
Q

CNS neuroglia

A
  1. Oligodendrocytes
  2. Microglia
  3. Astrocytes
  4. Ependymal – neural epithelia
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14
Q

Oligodendrocytes

A

Produce myelin around axon

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15
Q

Microglia

A
  • Protective
    • Become phagocytic if detect infected, dead, or
      damaged neurons (because immune cells can’t enter CNS
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16
Q

Astrocytes

A
  • Surround blood capillaries to form part of blood brain barrier (BBB)
  • Help control capillary permeability
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17
Q

Ependymal – neural epithelia

A
  • Line brain ventricles and central canal of the spinal cord
  • Secrete cerebrospinal fluid (CSF) and circulate it (cilia)
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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
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19
Q

Neuron Classification

A
  1. Structural/Anatomical types
  2. Functional types
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20
Q

Structural/Anatomical types

A
  • Based on # of cell processes off of cell body
    1. Unipolar
    2. Bipolar
    3. Multipolar
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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
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22
Q

Bipolar

A
  • 2 processes: 1 axon, 1 process with dendrites
  • Sensory – retina, nose (olfaction)
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23
Q

Multipolar

A
  • 3 or more processes: 1 axon, many dendrites
  • All interneurons and motor neurons
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24
Q

Functional types

A
  • Based on direction of impulse conduction
    1. Sensory/Afferent Neurons
    2. Interneurons
    3. Motor/Efferent Neurons
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25
Sensory/Afferent Neurons
- Mostly unipolar - From sensory receptors to CNS
26
Interneurons
- Within CNS (between sensory and motor) - 99% of neurons (mostly multipolar)
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Motor/Efferent Neurons
CNS to effectors (all multipolar)
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Neuron Junctions (Synapses)
1. Neuronal junction 2. Neuromuscular junction 3. Neuroglandular junction
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Neuronal junction
- Neuron to neuron - Can be chemical (use neurotransmitters) or electrical (ions)
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Neuromuscular junction
Motor neuron to skeletal muscle
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Neuroglandular junction
Motor neuron to gland
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Chemical Neuronal Synapses
- Most common - Structure: 1. Chemical Neuronal Synapses 2. Axon Terminal 3. Synaptic Cleft 4. Postsynaptic Neuron
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Presynaptic Neuron
Neuron bringing impulse
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Axon Terminal
- Within synaptic end bulbs - Inside the end bulb (presynaptic membrane) = synaptic vesicles containing neurotransmitter (nt)
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Synaptic Cleft
Space between neurons
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Postsynaptic Neuron
- Receives the impulse - Has postsynaptic membrane - = cell membrane of dendrites or cell body with receptor sites for nt
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Protective Features (Central Nervous System)
1. Bone 2. Meninges 3. Cerebrospinal Fluid (CSF) 4. Blood Brain Barrier (BBB) 5. Cerebral Arterial Circle
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Bone
Skull and vertebral column
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Meninges
- Connective tissue around brain and spinal cord - Layers: 1. Dura mater (outer) 2. Arachnoid mater (middle) 3. Pia mater (inner)
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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
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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
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Pia mater (inner)
- On surface of CNS (brain and spinal cord) - Vascular
43
Meningitis
Inflammation of meninges
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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
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Central Canal
Space in spinal cord
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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
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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
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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
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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
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Gyri = ridges
- Examples: - Postcentral gyrus in parietal lobe - Precentral gyrus in frontal lobe
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Sulci = shallow grooves (separate gyri)
- Example: - Central sulcus – between frontal and parietal lobes
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What are the 3 layers of Forebrain
1. Cerebral cortex 2. Tracts (white matter) 3. Basal nuclei
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Cerebral cortex
- 2 – 4 mm thick, gray matter - Has functional areas: 1. Motor areas 2. Sensory areas 3. Association Areas 4. Others
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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
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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
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Association areas (Cerebral Cortex)
- Recognize info from memories - Parietal, occipital, temporal lobes
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others (Cerebral Cortex)
- Memory - Temporal lobes - Conscious intellect (personality, learning, ideas, judgement, etc.) - Prefrontal cortex
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Tracts (white matter)
- Types: 1. Association tracts 2. Commissural tracts 3. projection tracts
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Association tracts
From gyrus to gyrus in same hemisphere
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Commissural tracts
- From gyrus to gyrus in opposite hemispheres - E.g. corpus callosum
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Projection tracts
Run vertically (brain to spinal cord / spinal cord to brain)
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Basal nuclei
- Paired masses of gray matter (within white matter) - Control skeletal muscle movement
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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
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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
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Hindbrain
1. Pons 2. Medulla 3. Cerebellum
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Pons
- Anterior to cerebellum - Tracts between brain and spinal cord, and tracts to/from cerebellum - Pontine respiratory centres
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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
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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
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Functional Systems
1. Limbic System 2. Reticular Formation
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Limbic System
- Nuclei in cerebrum and diencephalon - Regulates emotions (laughing, crying, etc.) - Contains areas involved in memory (memories evoke emotional responses
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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
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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
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Spinal Cord Cross-Sectional Structure
1. Anterior median fissure and posterior median sulcus 2. Central canal 3. Gray Matter 4. White Matter
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Anterior median fissure and posterior median sulcus
Separate cord into right and left halves
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Central canal
Contains CSF
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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
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White Matter
- Myelinated axons containing ascending (sensory) or descending (motor) tracts - Forms columns: 1. Dorsal column 2. Lateral column 3. Ventral column
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Functions of the Spinal Cord
- Sensory and motor impulses - Produces reflexes - Fast, predictable, automatic responses to changes in environment - E.g. withdrawal reflex
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Structures of the Peripheral Nervous System
1. Cranial Nerves 2. Spinal Nerves 3. Cross Section of a Nerve
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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
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Sample Mneumonic Devices
Oh Once One Takes The Anatomy Final Very Good Vacations Are Had
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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
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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
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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
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Dorsal Root
Sensory neurons; cell bodies in dorsal root ganglion
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Ventral Root
Autonomic and somatic motor neurons; cell bodies in ventral or lateral horn
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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
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Spinal Nerve Plexuses
1. Cervical 2. Brachial 3. Lumbar 4. Sacral
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Cervical
- Spinal Nerves: - C1 - C5 - Important Nerves: - Phrenic
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Brachial
- Spinal Nerves: - C5 - C8, T1 - Important Nerves: - Axillary, Radial, Ulnar, Median, Musculocutaneous
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Lumbar
- Spinal Nerves: - L1 - L4 - Important Nerves: - Femoral
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Sacral
- Spinal Nerves: - L4 - S4 - Important Nerves: - Sciatic → divides into: Tibial + Common Fibular
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Cross section of a nerve
- CT wrappings: 1. Epineurium - Around whole nerve 2. Perineurium - Around fascicles 3. Endoneurium - Around axon and myelin
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Sensory (Afferent) Division
1. Receptors 2. First Order Neurons
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Receptors
- Detect changes in environment - Classified by: 1. Location 2. Type of stimulus received 3. Structure of Receptor (general senses only)
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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
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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
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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
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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
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Motor (Efferent) Division
- 2 subdivisions 1. Somatic 2. Autonomic
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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)
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Autonomic
- Effector = smooth muscle, cardiac muscle, glands - 2 successive multipolar neurons from CNS to effector: 1. Preganglionic neuron 2. Postganglionic neuron
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Preganglionic neuron
- Myelinated - Cell body in brain stem or lateral horn of spinal cord
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Postganglionic neuron
- Unmyelinated - Cell body in autonomic ganglion (outside CNS)
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2 subdivisions of Autonomic
1. Sympathetic (SNS) 2. Parasympathetic (PSNS)
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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)
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Nervous System Pathways
1. Ascending Pathway (Sensory) 2. Descending Pathway (Motor):
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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
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First Order Neuron
Receptor to spinal cord (PNS)
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Second Order Neuron
- Interneuron, multipolar (CNS) - Cell body in dorsal horn of spinal cord or medulla (CNS) - Decussates (crosses over) in medulla
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Third Order Neuron
- Interneuron, multipolar - Cell body in thalamus – impulses to postcentral gyrus (sensory cortex) (CNS)
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Dorsal (Posterior) Column Pathway/Tract
- Sensations can be precisely located (touch) - Receptors = free nerve endings, Meissner’s etc.
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Spinothalamic Pathway/Tracts
- Non-specific, difficult to localize - Receptors = temperature, pain
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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
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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
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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
FINAL EXAM - BIOL 1410
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