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Anatomy > Introduction to anatomy of nervous system > Flashcards

Introduction to anatomy of nervous system Flashcards

1
Q

What are the planes of orientation in anatomy?

A
  1. Sagittal:
    - Vertical plane that cuts the body medially into right and left paths.
  2. Coronal:
    - Vertical plane that cuts the body in ant. & post. path.
  3. Transverse:
    - Horizontal plane that cuts the body medially into inferior and superior paths.
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2
Q

What are the divisions of the Nervous system?

A
  • Autonomic Nervous System: regulates glands, blood vessels & internal organs. Divided further into sympathetic and parasympathetic systems.
  • Somatic Nervous System: controls voluntary function
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3
Q

What cells tissues make up the nervous system?

A
  1. Neurons
  2. Support cells
  3. Blood vessels
  4. Connective tissue
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4
Q

What is a neuron?

A
  • Nerve cells that can develop action potential on their membrane and transmit electrical impulses.
  • An electrical impulses are then converted into chemical message at the synapse and so they can be passed to the next cell.
    *Basic working unit of the brain.
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5
Q

What is the basic structure of a neuron?

A
  • Contains:
    1. Cytoplasm
    2. Nucleus
    3. Cell body (soma)
    4. Axon
    5. Dendrite
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6
Q

What are the different types of neurons?

A
  1. Pseudounipolar:
    -Pseudo = false, uni = one
    - Sensory neuron in PNS
  2. Bipolar
    - Receptor-axon-cell body-axon-CNS
    - Two extensions (one axon and one dendrite)
    - e.g. peripheral sensory neurons for olfaction (smell), vision, hearing & balance
  3. Multipolar
    - Found throughout CNS
    - Multiple dendrites-single axon
    - e.g. motor neurons
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7
Q

What are support cells?

A
  • Cells whose function is primarily to provide structural support in the epithelial membrane or tissue.
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8
Q

What are the types of support cells and where are they found?

A
  • Brain & spinal cord (CNS): Glial cells:
    1. Oligodendrocytes produce myelin
    2. Astrocytes for structural support eg insulate synapses, uptake & synthesis of neurotransmitters
    3. Microglia: specialised macrophages that remove damaged neurons and infections
    4. Ependymal cells: form the epithelial lining of the ventricles in the brain and the central canal of the spinal cord, form a secretory epithelium (choroid plexus) that produces the cerebrospinal fluid (CSF)
  • Nerves (PNS):
    1. Schwann cells produce myelin
    2. Satellite cells surrounding neuronal cell bodies in ganglia
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9
Q

What is a synapse?

A
  • The junction across which signals or action potentials are transmitted.
  • Composed of a presynaptic membrane, a synaptic cleft (the space between a presynaptic and postsynaptic neuron), and postsynaptic membrane.
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10
Q

What are the types of synapses?

A
  1. Communicating axosomatic synapses
  2. Communicating axodendritic synapses
  3. Communicating axoaxonic synapses
    *Others: dendro-dendritic or somato-somatic synapses.
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11
Q

How is the structure of a synapse determine its function?

A
  • Asymmetric synapses type 1 excitatory
  • Symmetric synapses type 2 inhibitory
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12
Q

What is axonal transport?

A
  • The process by which nerve cells transfer substances between the cell body and axon tip.
  • Occurs in 2 directions:
    1. Anterograde transport: from the cell body toward the axon tip.
    2. Retrograde transport is from the axon tip back toward the cell body.
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13
Q

What is myelination?

A
  • When specific support cells produce layers of myelin that wrap around the neuronal axons and act as a layer of insulation for the transmission of electric action potentials down the neuronal axon.
  • Myelin insulates, speeds conduction .
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14
Q

What are peripheral nerves?

A
  • They are composed of nerve fibre: prolongations of nerve cells (cell body is located elsewhere/ far away). These nerves are covered by sheaths.
  • 1 nerve cell prolongation + sheaths = nerve fibre.
  • PN: nerve fibres are grouped parallel with each other and wrapped by layers of connective tissue.
  • They have a longitudinal striated pattern when viewed microscopically.
  • good vascularisation: blood vessels run parallel to nerve fibre (red striation visible microscopically).
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15
Q

What do peripheral nerves contain and what do these carry?

A
  • Different types of nerve fibres.
  • Nerve fibres transport stimuli on their surface in form of electrical current and pass on their information by releasing neurotransmitters.
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16
Q

What is a neurotransmitter?

A

Chemical messengers that transmit signals from nerve cells to target cells.
- Each individual nerve fibres can only use one neurotransmitter and always the same one.

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17
Q

Discuss mixed nerves.

A
  • Peripheral nerve can have motor nerve fibres located beside sensory nerve fibres or even autonomic fibres.
  • However remember:
    1. One given nerve can transport different types of stimuli.
    2. One single nerve fibre, however, is able to carry only one type of stimulus.
    3. Likewise, one single neuron is able to carry out only one type of function.
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18
Q

What is a nerve plexus?

A
  • A network-like structure formed by nerve fibres e.g. nerve fibres when exiting spinal cord.
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19
Q

What are ganglia?

A
  • The locations of the nerve cell bodies in the PNS.
  • Nerve prolongations have a corresponding cell body somewhere to which the nerve fibre is connected.
  • If nerve cell is outside of CNS, they are part of PNS. These neurons are concentrated in small islets and are surrounded by connective tissue.
  • These islets of nerve cell bodies in the PNS are called ganglia.
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20
Q

What are the nerve cells that can be grouped into ganglia?

A
  • Autonomic nerve cells
  • Sensory cells
    **Ganglia cannot be mixed: They either contain sensory neurons (sensory ganglia) or contain neurons of the ANS (autonomic ganglia).
21
Q

What makes up the CNS?

A
  • Brain: within cranium
  • Spinal cord: within vertebral canal of the vertebral column
  • Continuous with each other at foramen magnum (hole at base of skull).
22
Q

What are meninges?

A
  • Connective tissue membranes that surround brain and spinal cord.
  • 3 layers:
    1. Dura matter
    2. Arachnoid matter
    3. Pia matter
  • Sub-arachnoid space between arachnoid & pia is filled with cerebrospinal fluid and contains arteries.
23
Q

What is grey matter?

A
  1. White matter:
    - Most axons surrounded by myelin (Oligodendrocytes & Schwann cells)
    - All CNS axons, most PNS axons
    - More fibrous aspect given by the high content in myelinated fibres (in image). Dark spots = endothelial cells.
  2. Grey matter:
    - Cell bodies
    - In spinal cord, grey matter = butterfly shape
24
Q

How are myelin sheaths formed?

A
  • Protrusions of oligodendrocytes wrap around axons concentrically forming multiple layers of cell membrane which will form the myelin sheath.
25
Q

What is saltatory conduction?

A
  • An electrical impulse skips from node to node down the full length of an axon via the nodes of ranvier.
  • This is enabled by the segmental axon myelination.
26
Q

What are the divisions of the brain?

A
  1. Forebrain:
    - Right & left cerebral hemispheres joined by corpus collosum.
    - Thalamic structures (Thalamus & Hypothalamus)
  2. Brain stem:
    - Midbrain
    - Pons
    - Medulla oblongata
  3. Cerebellum:
    - Behind pons
    * Gyrus = ridge, sulcus = groove.
27
Q

What are ventricles and what is their function?

A
  • A communicating network of cavities filled with CSF and located within the brain.
  • 2 lateral ventricles, the third ventricle, the cerebral aqueduct, and the fourth ventricle
28
Q

Discuss the flow of CSF.

A
  • CSF flows from the lateral ventricles to the third ventricle via the foramen of Monro.
  • From here, it flows across the cerebral aqueduct of Sylvius to the fourth ventricle and onto the subarachnoid space through the apertures of Magendie and Luschka.
29
Q

What is the location of the spinal cord?

A
  • From foramen magnum at base of skull to LI vertebra.
  • Continuous with medulla oblongata.
30
Q

What is the function of the spinal cord?

A
  • Reflex center for each spinal cord segment (e.g. spinal reflexes)
  • Conduction pathway for impulses going to and from the brain.
31
Q

What is a vertebrae?

A
  • The back bones of the spine, they surround and protect the spinal cord.
  • Include the cervical spine (C1-C7), thoracic spine (T1-T12), lumbar spine (L1-L5), sacral spine (S1-S5), and the tailbone.
  • Each vertebra is separated by a disc.
32
Q

What is the PNS?

A
  • Nerve should always mean a peripheral nerve: Cranial or Spinal nerves. Nerve fibre = collection of many axons.
33
Q

What are the cranial nerves?

A
  • 12 pairs from the brain:
    I smell
    II vision
    III, IV, VI eye movements
    V facial and scalp sensation, mandibular movements
    VII facial expression
    VIII hearing, balance
    IX, X swallowing, phonation
    XI neck and head movements
    XII tongue movements
34
Q

What are the spinal nerves?

A
  • 8 cervical (neck):
    C1-8 for neck and upper limb
  • 12 thoracic:
    T1-12 for upper limb and thorax
  • 5 lumbar:
    L1-5 for abdomen and lower limb
  • 5 sacral:
    S1-5 for lower limb and perineum
    The urinary and anal sphincters, and the external genitalia, are supplied by S2-4 (sphincters and sex)
  • 1 coccygeal.
35
Q

Describe the structure of spinal nerves?

A
  • Connected to spinal cord by a dorsal & ventral root.
  • Exit spinal cord and may form plexuses at different levels and form new nerves with specific targets or destinations.
  • They are either sensory or motor.
36
Q

What is a sensory nerve?

A
  • Afferent
  • Enters posterior aspect of spinal cord
  • Cell body in spinal (dorsal root) ganglion
  • Ganglion=cluster of neural cell bodies outside the CNS
37
Q

What is a motor nerve?

A
  • Efferent
  • Exits anterior aspect of spinal cord
  • Cell body in spinal cord (grey matter)
38
Q

What is a dermatome?

A
  • An area of skin innervated by the sensory fibers of a single spinal nerve (position, motion, temperature).
  • e.g. the dermatome of S1 is supplied by S1 nerve which arises from S1 segment of spinal nerve (Sural nerve).
  • May help to identify site of lesion.
39
Q

What is a myotome?

A
  • Skeletal muscle receives motor innervation from fibers of a single spinal nerve.
  • e.g. L3: Knee extension
40
Q

What is a reflex?

A
  • Automatic, involuntary response to a stimulus
  • Monosynaptic: Knee and Ankle
  • Polysynaptic
41
Q

What are the stages of a reflex?

A
  1. Receptor
  2. Sensory neuron
  3. Integration centre
  4. Motor neuron
  5. Effector
42
Q

What is the direction of a nerve impulse?

A
  • Towards the CNS: sensory (afferent) impulse
  • Away from CNS: motor (efferent) impulse.
43
Q

Discuss the nature of perception in the nervous system.

A
  1. Somatic sensation:
    - We are acutely aware of these; well localised (e.g. sharp pain, touch).
    - Generally originate in body wall structures rather than internal organs.
  2. Visceral sensation:
    - Either imperceptible, only vaguely localisable, or only become perceptible in disease.
    - From blood vessels and internal organs (viscera).
44
Q

Discuss the type of actions in the nervous system.

A
  • Voluntary motor impulses control skeletal muscle over which we have voluntary control.
  • Visceral (involuntary) motor or autonomic control muscle over which we do not normally have voluntary control.
45
Q

How is autonomic impulse transported in the ANS?

A
  • Autonomic impulse to smooth muscle pass
    in two peripheral neurons:
    1. Preganlionic neuron
    2. Postganglionic neuron
46
Q

Discuss the differences between autonomic and sensory ganglion?

A
  • Autonomic ganglion=Synapse <> the pre-and postganglionic neurons.
  • Sensory ganglion=where cell bodies of sensory neurons in a particular nerve are located.
  • Ganglia are either sensory or autonomic, never both.
47
Q

What is the course of sympathetic nerves?

A
  • Preganglionic (white) fibres may run up or down chain before synapsing and then exiting via a nerve
48
Q

What is the function of ACh or NE in muscle contraction?

A
  • ACh = PNS neurotransmitter. It contracts smooth muscles, dilates blood vessels, increases bodily secretions, and slows heart rate.
  • NE = SNS neurotransmitter. It increase the force of skeletal muscle contraction and the rate and force of contraction of the heart.

Anatomy (18 decks)

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