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Biomedicine 1 > Nervous system 2 > Flashcards

Nervous system 2 Flashcards

1
Q

Central Nervous system (CNS)

A

Consists of the brain and spinal cord.
Spinal cord; Protected by the vertebral column and meninges
Brain; Protected by the cranium, cranium meninges, cerebral fluid (CSF) and the blood brain barrier (BBB)

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2
Q

Meninges

A

The meninges consist of three layers of connective tissue that cover the brain and spinal;
1) Dura mater (outer later)
Subdural space (interstitial fluid)
2) Arachnoid mater (middle layer)
Subarachnoid space (cerebrospinal fluid (CSF))
3) Pia mater (inner layer)

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3
Q

Meninges;
Dura mater

A

AKA tough mother
The tough outer-layer (support and protection); divides into two layers in the brain to create venous sinuses that allow blood to drain out of the brain into the jugular veins

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4
Q

Meninges;
Arachnoid mater

A

Similar to spider web
Middle layer, consists of collagen and elastic fibres
Subdural space between arachnoid mater and dura mater is filled with interstitial fluid

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5
Q

Meninges;
Pia mater

A

Delicate
Inner layer; thin transparent layer that contains blood vessels that supply the spinal cord
Between the pia mater and arachnoid mater is the sub-arachnoid space filled with cerebrospinal fluid

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6
Q

Cerebrospinal fluid (CSF)

A

A clear liquid that protects the brain and spinal cord from mechanical and immunological trauma
* Made from filtered blood, is mostly water with ions and glucose. Blood cells are too large to filter through, making CSF colourless
* Occupies the subarachnoid spaces and the ventricles (cavities) in the brain, as well as the central canal of the spinal cord
* Produced by ependymal cells continuously at a rate of 500ml / day. However, the brain can only contain 150ml, so large amounts are absorbed back into the blood

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7
Q

Cerebrospinal fluid (CSF); Functions

A
  • Supports and protects the brain and spinal cord, acting as a shock absorber
  • Maintains uniform pressure around the brain – in case of brain enlargement, compensation occurs by reduction of CSF
  • Keeps brain and spinal cord moist
  • Circulates nutrients and waste
  • Optimal chemical environment for nerve signaling; i.e. ions
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8
Q

Cerebrospinal fluid (CSF); choroid plexi

A

The choroid plexi produces CSF: They are networks of capillaries in the walls of ventricles and are covered by ependymal cells

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9
Q

Blood brain barrier (BBB)

A
  • The BBB protects the brain from toxins, harmful substances and bacteria that enter the bloodstream by maintaining tight junctions of the capillaries and the junctions between cells
  • The BBB is maintained by ‘astrocytes’
    (astro = star, cytes = cell)
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10
Q

Blood brain barrier (BBB); Transport

A

Transport across the BBB:
* Lipid soluble substances cross easily; e.g. alcohol, anaesthetics
* Glucose crosses by active transport
* Gases diffuse easily; e.g. oxygen, carbon dioxide
* Ions diffuse slowly across
* Proteins and some drugs DO NOT pass

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11
Q

The Brain; sections

A

The brain consists of four major parts:
1. The brain stem; divided into the medulla oblongata, pons and midbrain
2. Diencephalon (‘interbrain’); divided into thalamus, hypothalamus and epithalamus
3. Cerebrum (4 x lobes = frontal, temporal, parietal, occipital)
4. Cerebellum (‘little brain’)

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12
Q

The brain parts; brainstem

A

The brainstem is a continuation of the spinal cord in the cranium (beyond the ‘foramen magnum’)
It is divided into the medulla oblongata, pons and midbrain

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13
Q

The brain parts: brainstem; Medulla oblongata

A
  • Contains the respiratory and cardiac centres (regulates heartbeat and breathing)
  • Controls reflexes such as vomiting, sneezing and hiccupping
  • Contains four cranial nerves (nine – twelve)
  • Contains motor tracts (corticospinal tract)
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14
Q

The brain parts: brainstem; pons

A
  • Helps to control breathing
  • Four pairs of cranial nerves (five to eight)
  • Relays motor tracts
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15
Q

The brain parts: brainstem; midbrain

A
  • Contains the ‘substantia nigra’ (large darkly-pigmented area that contains dopamine releasing neurons that help control subconscious muscle activities)
  • Eye reflexes and tracking
  • Two cranial nerves (three and four)
  • Auditory tracts
  • Movement of head and neck
  • Transfers motor tracts
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16
Q

The brain parts; Diencephalon

A

Contains 3 areas:
1. Thalamus
2. Epithalamus
3. Hypothalamus
(dia = across, cephal = brain, hypo = low)

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17
Q

The brain parts: Diencephalon; Thalamus

A
  • The core of the brain, making up 80% of the diencephalon
  • ‘Major relay centre’ – relays sensory information for the cerebrum
  • Integrates sensory and motor information
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18
Q

The brain parts: Diencephalon; Epithalamus

A
  • Connects limbic system to other parts of the brain
  • Contains the pineal gland which secretes melatonin
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19
Q

The brain parts: Diencephalon; Hypothalamus

A

(Part of the emotional brain)
* Hormone regulation and homeostasis
* Received sensory information (i.e. from viscera, smell)
* Controls the ANS (a major regulator of visceral activities)
* Controls body temperature
* Regulates emotional and behavioural patterns (limbic), eating and drinking (appetite / satiety) and regulation of circadian rhythms

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20
Q

The brain parts: Cerebellum

A

‘Little brain’; maintenance of balance and posture, coordinates movement
* Located in the inferior and posterior aspect of the cranium. (Of the 100 billion neurons in the brain, half of them are packed into the cerebellum, despite it only accounting for one-tenth of brain mass).
* Susceptible to injury from chronic alcohol abuse. Cerebellar damage may also result from Coeliac’s disease or a thiamine (vit. B1) deficiency
* Cerebellar disease = symptoms of ataxia; lack of muscle co-ordination. Commonly results in stumbling, unsteadiness, slurred speech and an intention tremor (e.g. hand tremor when putting key in lock

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21
Q

The brain parts: Cerebellum; functions

A
  • Maintenance of posture and balance
  • Functions to co-ordinate and smooth complex (‘skilled’) sequences of movements
  • Correction of errors during ongoing movement. Discrepancies are detected by cerebellum which sends feedback to cerebrum via the thalamus (e.g. learning to walk, learning an instrument)
  • Also thought to play a role in cognition, thought and language processing
  • It alters motor behaviour by altering circuits that influence motor pathways (corticospinal tracts)
    (Cerebellum = little brain)
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22
Q

The brain parts: the cerebrum - structure / sides

A

The cerebrum is divided into two hemispheres (left and right)
* Contains an outer cerebral cortex that contains grey matter (cell bodies). It has multiple foldings (fissures)
* The deeper region of cerebral is white matter (myelinated axons)
* The two hemispheres are connected by the ‘corpus callosum’, allowing coordination of movement between sides (e.g. walking)
* The brain does not decide what a person does. The individual uses the brain like a computer

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23
Q

The brain parts: the cerebrum; functions

A
  • Sensory perception
  • Motor control of skeletal muscles (movement)
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24
Q

The brain parts: the cerebrum; cerebral hemispheres

A

Motor neuron axons join to form the corticospinal tract. These motor tracts cross over in the medulla oblongata (decussating)
* This means the left side of the brain co-ordinates the right side of the body and the right side of the brain co-ordinates the left side of the body

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25
Q

The brain parts: the cerebrum; lobes

A

Each cerebral hemisphere can be further subdivided into four lobes, which are named after the bones that cover them; frontal, parietal, temporal, occipital
Each of these lobes performs different functions;
1. Frontal lobe = motor skills
2. Temporal lobe = hearing
3. Parietal lobe = contains sensory cortex
4. Occipital lobe = vision

26
Q

Limbic system

A

The limbic system is area of the brain that is active with different emotions
* Formed of several functionally and anatomically interconnected structures including parts of the cerebrum, diencephalon and midbrain
* Key structures within it include the hypothalamus, hippocampus and amygdala
* Becomes active when dealing with emotional responses to our environments
* The Amygdala is a key area of emotions, whilst the hippocampus plays an essential role in encoding and retrieving memories

27
Q

Brain blood supply

A

The brain has very limited ability to store oxygen or glucose, therefore, a constant supply is necessary
* Brain receives about 20% of cardiac output (about 750ml per minute) despite accounting for 2% of body mass
* Cardiovascular health is important for brain health
* The blood supply to the brain is from two major arterial systems: carotid and vertebral
* The two arterial systems meet to form the Circle of Willis. This is a common located for aneurisms to develop (Berry aneurysms)

28
Q

Cranial nerves

A

There are 12 cranial nerves with different functions:
i. Olfactory (sensory)
ii. Optic (sensory)
iii. Oculomotor (motor)
iv. Trochlear (motor)
v. Trigeminal (both)
vi. Abducens (motor)
vii. Facial (both)
viii. Vestibulocochlear (sensory)
ix. Glossopharyngeal (both)
x. Vagus (both)
xi. Accessory (motor)
xii. Hypoglossal (motor)

29
Q

Cranial nerves; origin

A

2 from the cerebrum (Olfactory and Optic)
2 from the mid brain (Oculomotor and Trochlear)
4 from the pons (Trigeminal, Abducens, Facial and Vestibulochlear)
4 from the medulla oblongata (Glossopharyngeal, Vagus, Accessory, Hypoglossal)

30
Q

Cranial nerve; I (name and tract)

A

i. Olfactory; (sensory)

31
Q

Cranial nerve; ii (name and tract)

A

Optic; (sensory)

32
Q

Cranial nerve; III (name and tract)

A

Oculomotor; (motor)

33
Q

Cranial nerve; iv (name and tract)

A

iv. Trochlear; (motor)

34
Q

Cranial nerve; v (name and tract)

A

Trigeminal; (both sensory and motor)

35
Q

Cranial nerve; vi (name and tract)

A

Abducens; (motor)

36
Q

Cranial nerve; vii (name and tract)

A

Facial nerve; (both sensory and motor)

37
Q

Cranial nerve; viii (name and tract)

A

Vestibulocochlear; (sensory)

38
Q

Cranial nerve; ix (name and tract)

A

Glossopharyngeal; (both sensory and motor)

39
Q

Cranial nerve; x (name and type)

A

Vagus nerve; (both sensory and motor)

40
Q

Cranial nerve; xi

A

Accessory (spinal) nerve (motor)

41
Q

Cranial nerve; xii

A

Hypoglossal (motor)

42
Q

Cranial nerve: i; Olfactory

A

Sense of smell

43
Q

Cranial nerve:
Viii; Vestibulocochlear

A

Hearing and balance

44
Q

Cranial nerve:
Vii; Facial

A

Taste, facial expressions and salivary glands

45
Q

Cranial nerve:
ii; Optic

A

Vision (sight)
The optic nerve is only visible in the retina
The optic nerve spans through the majority of the cranium so is useful to assess in cases of suspected intracranial lesions

46
Q

Cranial nerves:
iii; Oculomotor
iv; Trochlear
vi; Abducens

A

Oculomotor;
Moves eyeballs, elevates eyelid (four out of six muscles)

Trochlear;
Rotates eyes, i.e. for reading (one of six eye muscles)

Abducens abducts eyes (one of six eye muscles)

Damage to one of these nerves can lead to strabismus (one eye crossed), ptosis (drooping of upper eyelid) and diplopia (double vision)

47
Q

Cranial nerve:
V; Trigeminal

A

Facial sensations, mastication, some taste
CN v has three branches; Ophthalmic, maxillary and mandibular

48
Q

Cranial nerve:
Ix; Glossopharyngeal

A

Taste, swallowing and tongue sensations

49
Q

Cranial nerve:
X; vagus

A

‘Wandering nerve’ – long course
ALL sensory information from the chest and abdomen (heart, GI tract, lungs); e.g. sensation from epiglottis, detects gas levels in arteries
The largest nerve of the autonomic NS – mostly parasympathetic but some sympathetic (increases BP)
Both sensory and motor function but 90% of fibres are afferent (sensory)
Injuries may result in tachycardia, dysphagia, vaso-vagal syncope (fainting).

50
Q

Cranial nerve:
Xi; Accessory (spinal) nerve

A

Innervates trapezius and sternocleidomastoid, causing shoulder elevation and neck side bending / rotation

51
Q

Cranial nerve:
Xii; Hypoglossal

A

Tongue, movement and speech

52
Q

Spinal cord

A

Begins at the foramen magnum and terminates at the vertebral level L2 as the ‘conus’.
The meninges continue beyond L2 to the level of S2 (sacrum)
The causa equina (horses tail) consists of spinal nerves that continue beyond the conus

53
Q

Spinal cord physiology; white matter and tracts

A

The spinal cord consists of white matter around a core of grey matter:
White matter;
Consists of bundles of myelinated axons
Made up of ‘tracts’ (highways):
1. Motor (descending) tracts: voluntary and involuntary movement (coordination, posture, balance)
2. Sensory (ascending) tracts: transmit impulse from skin, tendons, muscles and joints (e.g. touch, vibration, proprioception)

54
Q

Spinal cord physiology; grey matter

A

The spinal cord consists of white matter around a core of grey matter:
Grey matter:
Consists of cell bodies and dendrites
Receives and integrates incoming and outgoing information. Divided into:
1. Posterior (dorsal) horn); receives sensory impulses
2. Anterior (ventral) horn; sends out motor impulses

55
Q

Spinal cord ‘tracts’ physiology; acronyms

A

MOVED:
* Motor
* Output
* Ventral (horn)
* Efferent (exit)
* Descending

SIDAA:
* Sensory
* Input
* Dorsal (horn)
* Afferent (in)
* Ascending

56
Q

Spinal cord; tracts

A

Sensory columns (ascending) =
1. Dorsal columns; light touch, vibration, proprioception

  1. Spinothalamic tract; pain and temperature

Motor tracts (descending)
3. Corticospinal tract; voluntary movements

Damage to any of the spinal tracts would lead to loss of the tract’s function below that level in the body

Tract = axon bundles in spinal cord, thalamic = temperature, proprioception = awareness of position)

57
Q

Reflex Arcs

A

A reflex is a fast, automatic, unplanned sequence of actions that occurs in response to a stimulus
If the integration takes place in the spine it is known as a ‘spinal reflex’

Reflex arcs include the following:
1. Sensory receptor
2. Sensory neuron
3. Integrating centre (interneuron)
4. Motor neuron
5. Effector organ
Apply these components to the following example; placing hand on hot surface

58
Q

Spinal Nerves

A

The spinal cord contains extensions called spinal nerves, which exits the vertebral column through holes in the vertebra called vertebral foramina (holes). Each spinal nerve corresponds with a vertebral foramen.

59
Q

Brain ; Blood flow

A

Blood flows to the brain from the vertebral and carotid arteries
* Brain uses 20% of the body’s oxygen and glucose at rest – neurons die within minutes of being deprived of oxygen

60
Q

Cranial nerves nmemonic

A

ONLY = olfactory
ONE = optic
OF = oculomotor
THE = trochlear
TWO = Trigeminal
ATHLETES = abducens
FELT = facial
VERY = vestibulocochlear
GOOD = glossopharyngeal
VICTORIOUS = vagus
AND = accessory
HEALTHY = hypoglossal

61
Q

Cranial nerves nmemonic - sensory / motor

A

SOME = S = olfactory
SAY = S = optic
MONEY = M = oculomotor
MATTERS = M = trochlear
BUT = B = Trigeminal
MY = M= abducens
BROTHER = B = facial
SAYS = S = vestibulocochlear
BIG = B = glossopharyngeal
BRAINS = B = vagus
MATTER = M = accessory
MORE = M = hypoglossal

S = sensory
M = motor
B = both

62
Q

Spinal cord tracts

A

Made up of ‘tracts’ (highways):
1. Motor (descending) tracts: voluntary and involuntary movement (coordination, posture, balance)
2. Sensory (ascending) tracts: transmit impulse from skin, tendons, muscles and joints (e.g. touch, vibration, proprioception)

Biomedicine 1 (39 decks)

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