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102 T1 anatomy > Nervous system > Flashcards

Nervous system Flashcards

1
Q

Describe a neuron

A 
functional unit of the nervous system
Soma/cell body 
 Contains the nucleus
 Synthesis of proteins/ion channels
- Important for cellular metabolism

Dendrites (dendritic tree)
Receives inputs
Convey information towards soma
- Large surface area (spines) for synapse formation

Axon hillock
- Origin of the axon
Very excitable

Axon/nerve fibre
- Transmits action potential
Usually only one (although often branches)

Axon terminals
Synapse on other neurons, effector organs or forms specialized ending

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2
Q

Describe unipolar neuron

A

E.g. Primary sensory neurons

  • Cell bodies in ganglia (found close to intervertebral foramen)
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3
Q

Describe bipolar neuron

A

One axon and one dendrite

E.g. Specialized sensory neurons

  • Found in retina
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4
Q

Describe Multipolar neuron

A

One axon and multiple dendrites

  • E.g. Majority of neurons in brain
  • Also, motor neurons
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5
Q

What are the two types of neutrons in terms of function

A

Afferent – Carry information to central nervous system

Efferent – Carry information away from central nervous system

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6
Q

Describe axons

A

Can be myelinated (>1µm diameter)

Saltatory conduction:

Very rapid (up to 120m/s)

Action potential passes from node to node

Can be unmyelinated (<1µm diameter)

  • Very slow (<1.5m/s)
  • E.g. Pain fibre

Larger axon diameter = faster conduction

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7
Q

Describe synapses

A

Junction between axon terminal and target cell
- E.g. neuron (dendrite) or muscle (neuromuscular junction)

Chemical synapses:
Majority of synapses are chemical synapses

Use neurotransmitters (e.g. acetylcholine)

  • Depolarisation of presynaptic membrane opens Ca+ channels
  • Vesicles fuse to membrane and release neurotransmitter
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8
Q

Describe astrocytes

A

Provide structural support

Supply nutrients

Maintain ionic environment (remove K+)

Neurotransmitter uptake

Repair of the nervous system

  • Form barrier around vessels
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9
Q

Describe Oligodendrocytes

A

Production and maintenance of myelin sheath

  • One oligodrocyte myelinates multiple axons
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10
Q

Describe microglia

A

Immune cells

  • Phagocytic (like macrophages)
  • Cytotoxic (releasing H2O2)
  • Promote repair
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11
Q

Discuss the neuroglia of the PNS

A

Schwann cells are the neuroglia of the PNS

Myelinate axons (spiral wrapping)

Important for regeneration
(provide substrate for axon to grow along)

One Schwann cell myelinates one axon

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12
Q

Describe the central nervous system

A

Brain is divided into forebrain, midbrain and hindbrain

Made up of grey and white matter

FOREBRAIN:
Cerebral hemispheres
Thalamus
Hypothalamus

MIDBRAIN:

HINDBRAIN:
Cerebellum
Pons
Medulla

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13
Q

Describe the forebrain

A

The cerebral hemispheres are highly developed

The outer grey matter layer is the cerebral cortex

Function is to process motor and sensory information

Although, 80% of cortex functions in cognition

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14
Q

Describe the lobes of the cerebral hemisphere

A

Frontal lobe: Primary motor cortex

Parietal lobe: Primary somatosensory cortex (pain, touch and proprioception)

Temporal lobe: Primary auditory cortex + olfaction

Occipital lobe:
Primary visual cortex

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15
Q

Describe the thalamus

A

The thalamus is the relay centre of the brain

Paired structure

Centrally located

All sensory information (except smell) is relayed via the thalamus

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16
Q

Describe the hypothalamus

A

The hypothalamus is important in homeostasis

Sits below thalamus

Controls:
- Autonomic nervous system

  • Endocrine system
17
Q

Describe the brainstem

A

The brainstem is formed by the midbrain and hindbrain

  1. Connects cerebral cortex to spinal cord
  2. Controls respiration and the cardiovascular system

damage will most likely be fatal

18
Q

Describe the hindbrain

A

The cerebellum coordinates complex muscular movements

Sits behind the brainstem

19
Q

Describe the spinal cord

A

Extends from atlas to first lumbar vertebra (L1)

Sits within vertebral canal

Conveys information from PNS to brain (sensory)

Conveys information from brain to PNS (motor)

Involved in reflexes

Segmentally organised

Inner core of gray matter
Neuronal cell bodies

Outer, white matter
Myelinated axons
Convey information to/from brain

20
Q

Describe the peripheral nervous system

A

Connects CNS with periphery

Nerve supply to muscles, glands, skin, vessels, viscera

Peripheral nerves convey motor, sensory and autonomic axons

21
Q

Describe the somatic component of the PNS

A

Comprises:
Somatic motor neurons
- Axons of the motor neurons that supply the skeletal muscles

Somatosensory neurons
- Axons of the primary sensory neurons

  • Carries information about external environment (Exteroceptive)
  • Carries information from within body (Proprioceptive)
22
Q

Describe the origin of peripheral nerves

A

All peripheral nerves arise from:

Brain or brainstem as Cranial nerves

Spinal cord as Spinal nerves

23
Q

Describe spinal nerves

A

Spinal nerves provide motor and sensory supply to whole body, except head and neck

Also sympathetic supply to whole body

Excellent segmental organisation

  • One pair of spinal nerves at each vertebrae

Dorsal and ventral roots merge to form spinal nerves

Mixed nerves (motor, sensory and sympathetic)

Exit through intervertebral foramen

24
Q

Describe the spinal nerve organisation

A

8 cervical: Upper limb/head/neck

Note, only 7 cervical vertebrae

C1-7 exit above vertebrae, C8+ exit below

12 thoracic: Thorax/abdomen

5 lumbar: Pelvis/lower limb

5 sacral: lower limb

1 coccygeal nerve

25
Q

Describe the dorsal and ventral roots

A

Nerve roots connect spinal nerves to the spinal cord

Ventral root – Efferent (motor/sympathetic)

Dorsal root – Afferent (sensory)

Nerve roots sit within vertebral canal

26
Q

Describe the primary rami

A

Spinal nerves divide into:
- Dorsal/posterior primary ramus

  • Ventral/anterior primary ramu
27
Q

Describe the dorsal primary ramus

A

Supplies:
Skin over paravertebral gutter

Erector spinae muscles

Facet joints of vertebral column

28
Q

Describe the ventral primary ramus

A

Supplies rest of the body (i.e. skin and musculoskeletal system)

Much larger nerve

29
Q

Describe the map of ventral primary rami

A

Form intercostal nerves and four nerve plexuses

A nerve plexus is where ventral primary rami merge

Forms nerves contain axons from multiple spinal nerves

Important for innervation to limbs (large muscle groups)

30
Q

Describe dermatomes and myotomes

A

Segmental organization of spinal nerves results in dermatomes and myotomes

Dermatome:
- An individual area of skin innervated by a single spinal nerve (primary ramus)

Myotome:
An individual muscle group innervated by a single spinal nerve (primary ramus)

31
Q

Describe the Embryonic development of dermatomes and myotomes

A

Dermatomes and myotomes develop from somites (mesoderm) during embryonic week 3

Somites are paired blocks that form horizontal bands

One pair of spinal nerves (ectoderm) grows into one pair of somites

32
Q

Discuss the clinical importance of dermatomes

A

Loss/altered sensation/pain from dermatome indicates injury to spinal cord, nerve root or spinal nerve

  • Easy to determine location of injury from dermatomes

E.g. loss of sensation from skin over umbilicus may indicate damage to……

Also, visceral (organ) pain can be referred to skin (dermatomes) as cutaneous pain

E.g. Diaphragm irritation referred to shoulder

(C3-C5 dermatomes)

33
Q

Describe myotomes

A

Conserved in thorax

Intercostal muscles supplied by intercostal nerves (T1-T11)

More complicated in limbs (more than one spinal nerve innervating muscle groups)

34
Q

Describe the autonomic component of PNS

A

Involuntary part of the peripheral nervous system

Involuntary control:

  • Regulates operation of the internal organs
  • Maintains internal environment

Two main divisions of the ANS:
SYMPATHETIC

PARASYMPATHETIC

35
Q

Discuss the origin of ANS

A

Parasympathetic
Origin: Brainstem

Sympathetic
Origin: Thoracic/lumbar spinal cord

Parasympathetic
Origin: Sacral spinal cord

36
Q

Describe the sympathetic trunk

A

Interconnected paravertebral ganglia

Sits either side of vertebral column

All preganglionic sympathetic axons enter the sympathetic trunk

Postganglionic axons exit via spinal nerves to - musculoskeletal system

(Constriction of blood vessels,
piloerection, sweating)

Postganglionic axons exit through branches to heart, lungs or head

(Bronchodilation, increase cardiac output,
pupil dilation, increase sweating)

37
Q

Describe the prevertebral ganglia

A

Some preganglionic axons enter splanchnic nerves and pass to prevertebral ganglia in abdomen

Postganglionic axons project to - abdominal/pelvic organs

(Inhibit peristalsis/gastric secretions, stimulates glucagon release)

38
Q

Describe the Cranial parasympathetic

A

Cell bodies of preganglionic neurons in brainstem

Ganglia located close to effector organs

39
Q

Describe sacral parasympathetic

A

From sacral part of spinal cord

Preganglionic axons exit via pelvic splanchnic nerves

Synapse with postganglionic axons
on the pelvic organs

102 T1 anatomy (5 decks)

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