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BME331 > 9. Nervous System Organisation > Flashcards

9. Nervous System Organisation Flashcards

1
Q

CNS is..

A

Central Nervous System - brain and spinal cord

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2
Q

PNS is..

A

Peripheral Nervous system - nerve fibres that carry information between the CNS and other parts of the body

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3
Q

Afferent vs. Efferent

A

Afferent - inwards towards CNS
Efferent - e.g. motor command

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4
Q

Sensory vs. Visceral stimuli

A

Related to Afferent division

Sensory - touch, see, smell etc
Visceral - input from organ sensors

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5
Q

Efferent Division

A
  • splits into somatic and autonomic nervous system
    somatic: Voluntary motor movement e.g. move my arms, skeletal muscles (aware/conscious)
    autonomic: sympathetic and parasympathetic nervous system, rest of muscle types (not consciously controlling)
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6
Q

What is this

A

CNS and PNS overview

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7
Q

3 functional classes of neurons

A
  • afferent neuron - starts in PNS, end in CNS
  • efferent neuron - start in CNS, end in PNS
  • interneurons - starts and end in CNS - (can connect afferent neuron and efferent neurons and interneurons mainly found in brain)
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8
Q

Structure and function of CNS

A

Brain and spinal cord
cognition referee to the act or process of ‘knowing’ including awareness and judgement
no part of the brain works in isolation

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9
Q

Brain diagram

A

Core vital life functions in centre of brain
Thought processes and thinking in cerebral or outer brain layer

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10
Q

Major brain functions

A
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11
Q

Protection of the CNS

A

Glial Cells - support cells (90% if cells within CNS, called neuroglia cells)
- don’t conduct nerve impulses

Astrocytes - most abundant glial cell and fills a number of critical functions

Microglia - immune cells of the CNS

Ependymal - line cavities and contribute formation of CSF (cerebral spinal fluid)

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12
Q

Protection of CNS diagram

A

Note oligodendrocyte are…

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13
Q

Blood brain barrier

A
  • Shields brain from harmful changes in the blood
  • Consists of endothelial cells
  • Tight junctions prevent exchange across the capillary wall
  • Lipid soluble substances such as oxygen and alcohol can penetrate cells
  • ie if not lipid soluble needs a carrier protein
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14
Q

Role of Oxygen and Glucose

A
  • Brain is highly dependent on constant blood supply
  • Brain can not produce ATP in absence of oxygen
  • Brain does not store glucose
  • Damage occurs if oxygen is cut off for 5 mins or glucose for more than 15 mins
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15
Q

Cerebral Cortex

A
  • largest portion of the brain
  • Two halves (right and left cerebral hemispheres joined by corpus callosum)
  • Corpus callosum allows two hemispheres to communicate and cooperate with each other
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16
Q

Brain picture

A

2 halves

note: corpus callosum is in middle

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17
Q

Cerebal Cortex colour

A
  • Thin outer shell of grey matter (neuronal cell bodies) on each hemisphere - densely packaged
  • Bundles or tracts of myelinated nerve fibres (axons) constitute the white matter - Transmit signals from one part of the cerebral cortex to another and to other regions of the CNS
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18
Q

Outer brain diagram

A
19
Q
A
20
Q
A

Motor Homunculus

(and left side brain, left side body)

21
Q

Plasticity and Neurogenesis

A
  • ability to change or be functionally remodelled in response to the demands
  • when an area of the brain is destroyed other areas of the brain may gradually assume some or all of the functions of the damaged region
22
Q
A

Sensory Input to Motor output example

  • going from low level/sensitivity data to higher level choices in brain
23
Q

Cerebral Hemispheres

A

left side is commonly dominant hemisphere for fine motor control, so most people are right handed

left side excels in logical, analytic, sequential & verbal tasks

right side excels in nonlanguage skills such as spatial perception, arts & music

24
Q

Basal Ganglia

A

consist of several masses of grey matter located deep within the cerebral white matter

– Complex role in movement

25
Q

Thalamus

A

deep in brain near the basal ganglia

  • serves as a relay station and integrating centre
26
Q

Hypothalamus

A

is an integrating centre that lies beneath the thalamus

  • multifunctional regulating the internal environment
27
Q

Limbic System

A

surrounds brain stem and not a separate structure

an interconnected ring of forebrain structures

related to

  • emotions - amygdala
  • basic behavioural patterns
  • reward and punishment centres
28
Q

Brain stem

A
  • pons
  • medulla oblongata
  • midbrain
29
Q

5 functions of the brain stem

A

Five Functions of the Brain Stem

Majority of cranial nerves arise from the brain stem

Contains centers that control cardiovascular, respiratory, and digestive function

Regulates postural muscle reflexes

Reticular activating system (RAS): controls the

overall degree of cortical alertness

Plays a role in the sleep–wake cycle

30
Q

Spinal cord

A
  • spinal cord extends from brain stem
  • paired spinal nerves emerge from the spinal cord through spaces in vertebrae
  • thick bundle of elongate nerve roots within the lower vertebral canal is called the caudal equina - like a horse’s tail
31
Q

Organization of Neural Tissue in the Spinal Cord

A

opposite in spinal cord

Spinal Cord White Matter
– Organised into tracts (ascending and descending tracts)
– Located in the outer section of the spinal cord

Spinal Cord Grey Matter

  • Dorsal (posterior) horn - receiving sensory input (afferent neurons)
  • Ventral (anterior) horn - motor input (with efferent neurons)
  • Lateral horn - autonomic processes
  • Located in inner section of the spinal cord
32
Q

Spinal Nerves

A
  • Spinal nerves connect with each side of the spinal cord by a dorsal root and a ventral root
  • A spinal nerve consists of both afferent and efferent fibres
    • A nerve is a bundle of peripheral neuronal axons enclosed by a connective tissue covering and following the same pathway
  • the arms will be higher on the spine compared to the legs for example
33
Q
A

Levels in the spinal cord

  • cervical nerves - neck
  • thoracic nerves - upper body
  • lumbar nerves - lower back, pelvis, legs
  • sacral - urinary tract
  • coccygeal nerve
34
Q

The PNS (Peripheral Nervous System)

A

The PNS consists of nerve fibres that carry information between the CNS and other parts of the body

Afferent division of the PNS: Sends information from internal and external environment to CNS (i.e. carries signals to CNS).

Efferent division of the PNS: Communication link by which CNS controls activities of muscles and glands (i.e. carries signals from CNS).

35
Q
A
  • Nerve, bundle of nerve fibres, called fascicles bundles with other fascicles and connective tissue
  • As it moves further from spinal cord it branches off and splits into single nerves
36
Q

Afferent Division - towards central nervous system

A
  • Visceral afferent
    • Incoming pathway for information from internal viscera (organs in body cavities)
  • Sensory afferent
    • somatic (body sense) sensation - arising from body surface and proprioception and where you are in space/touch
    • Special senses - vision, hearing, taste, smell
37
Q

Receptor Physiology

A

Structures (receptors) at peripheral endings of afferent neurons

Detect stimuli (change detectable by the body e.g. temperature)

Convert forms of energy into electrical signals (action potentials)

– Process is called transduction

38
Q

Types of Receptors

A

Photoreceptors - responsive to visible wavelengths of light

Mechanoreceptors - sensitive to mechanical energy (pressure, stretch, vibration)

Thermoreceptors - sensitive to temp/hot & cold

Osmoreceptors - detect changes in concentration of solutes in body fluid and resultant changes in osmotic activity

Chemoreceptors - sensitive to specific chemicals, & include receptors for smell and taste and receptors that detect O2 and CO2 concentrations in blood and chemical content of digestive tract

39
Q

Stimuli and Receptor Permeability

A

Receptors may be either

– The specialized ending of an afferent neuron

– a separate cell closely associated with peripheral ending of a neuron

  • • Stimulus alters receptor’s permeability, which leads to graded receptor potential > then reach a threshold and cause an action potential
  • nonselective opening of all small ion channels – This change in membrane permeability can lead to the influx of sodium ions
    • This produces receptor (generator) potentials

The magnitude of the receptor potential represents the intensity of the stimulus - a receptor potential of sufficient magnitude can produce an action potential.

This action potential is propagated along an afferent fibre to the CNS

40
Q

Types of receptors and speed of adaptation

A
  • receptors may adapt slowly or rapidly to sustained stimulation
    • tonic receptor - do not adapt or slowly e.g. muscle stretch receptors, joint proprioceptors
    • phasic receptor - rapidly adapting e.g. tactile receptors in skin
41
Q

Efferent Division

A

Autonomic nervous system (ANS)

– Involuntary branch of PNS

– Innervates cardiac muscle, smooth muscle, most exocrine glands, some endocrine glands, and adipose tissue

Somatic nervous system
– Subject to voluntary control

– Innervates skeletal muscle

42
Q

Autonomic Nervous System

A
  • sympathetic nervous system - fight or flight, emergency or stress
    • promotes responses that prepare body for physical activity
  • parasympathetic nervous system – quiet and relaxed situations
    • promotes body-maintence activities such as digestion
43
Q
A

Effects of autonomic nervous system on various organs

44
Q

Somatic Nervous system

A

Consists of axons of motor neurons from spinal cord or brain stem and end on skeletal muscle

Motor neurons are the final common pathway by which various regions of CNS exert control over skeletal muscle activity - areas of CNS include spinal cord, motor regions of cortex, basal nuclei, cerebellum, and brain stem

BME331 (6 decks)

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