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Human Physiology- Brain > Brain > Flashcards

Brain Flashcards

1
Q

Central Nervous System (CNS)

A

Everything inside the spine and skull

cortex, subcortical structures and nuclei, spinal cord

all encased in bone

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2
Q

Peripheral Nervous System (PNS)

A

everything outside of the spine and skull

Nerves- bundles of axons connecting CNS to body

Ganglion- clusters of cells associated with nerves

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3
Q

PNS system

A

Has inputs that arrive (Afferent)

Has outputs that exit (Efferent)

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4
Q

Peripheral Motor Output System (Efferent)

A

Somatic- controls voluntary movement

Autonomic- controls involuntary unconscious movements, has two components

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5
Q

Somatic motor system (efferent)

A

peripheral nerves exit the spinal cords and contact muscles

stimulation of nerves cause contraction of muscles

controls voluntary movement

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6
Q

Autonomic (efferent)

A

controls the lungs, heart, smooth muscles and endo and exocrine glands

two autonomic systems work together to to keep system balance

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7
Q

Sympathetic v parasympathetic

A

Complex system with many functions

Parasympathetic- rest and digest

Sympathetic- fight or flight

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8
Q

Sensory (afferent)

A

5 basic sensory systems (aware)-

Visual
Auditory
Olfactory (smell)
Gustatory (taste)
Tactile sensation (touch)

Not aware-

Vestibular (sense of head movement in space)
Proprioceptive (sensations from the muscles and joints of the body)

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9
Q

Movements as a circuit

A

All movements start in the sensory domain from a sensory input

Movements are- in response to an external stimuli (saving penalty)

Directed at an external stimulus (taking penalty)

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10
Q

2 major cell types

A

Neurones- electrically excitable
cell

communicate
with other cells via
specialized connections
called synapses.

Glial cells-non-neuronal cells in the
nervous system

maintain homeostasis,
form myelin, and
support and protect for
neurones.

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11
Q

Neurone

A

send and receive signals from your brain.

A cell body, which contains the nucleus and the cytoplasm

An axon, which transmits information away from the nucleus

Dendrites, which receive messages from other neurons.

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12
Q

Information passed through neurones

A

information passes from the cell body to
the axon terminals via an electrical
signal called an action potential

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13
Q

glia/ glial cells

A

5 major types of glial cells-

schwann cells
oligodendrocyte
microglial cell
ependymal cells
astrocyte

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14
Q

astrocytes- managing the brain environment

A
  1. regulates chemicals around neurones (glucose, ion concentrations, neurotransmitter uptake)

regulate blood flow around the brain

nervous system repair- fill in spaces creating glial scars

maintenance of the blood brain barrier.

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15
Q

Oligodendrocytes

A

form the myelin sheath on axons

Myelin- a fatty protein rich sheath that wraps around axons

1 can myelinate 50 axons

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16
Q

Schwann cells

A

form myelin in PNS

assist in regeneration/ regrowth of axons

myelin increases speed

unmyelinated speeds-0.5-10m/s- slow

myelinated speeds-up to 150m/s

creates initial pain/reaction and then secondary worse pain.

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17
Q

microglia

A

the brains immune system

scavenge the CNS for plaques, damaged cells and infectious agents

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18
Q

ependymal cells

A

make up the membrane called ependyma

membrane lines central canal of the spinal cord and ventricles

produces cerebrospinal fluid

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18
Q

Summary of cells in the nervous system

A

CNS-
neurones
microglia
astrocytes
ependymal
oligodendrocytes

PNS-
neurones
satellite
schwann

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19
Q

grey v white matter

A

myelin is a sheath that insulates many neurones

it is made of fat and proteins and is white

because of this parts of the brain that are many made up of axons are white (white matter).

the brains contains mainly the cell bodies of the neurones - nuclei, ganglion,
cortex - appear pink in the fresh tissue, but grey in perfused
(grey matter).

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20
Q

basic layout of the motor system

A
  1. spinal cord
  2. medulla
  3. pons
  4. cerebellum
  5. midbrain
  6. thalamus
  7. basal ganglia
  8. cerebral cortex
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21
Q

Brainstem``

A

sits at the top of the spinal cord

made of 3 parts-
medulla
pons
cerebellum``

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22
Q

medulla

A

the lower half of the brainstem

controls very basic motor functions

cardiac- central chemoreceptors sense oxygen levels- adjust heart rate/ blood pressure

respiration- chemoreceptors sense change in blood chemistry- increase breathing rate

reflexes- vomiting’s, coughing, sneezing and swallowing

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23
Q

`pons

A

contains nuclei that relay signals from forebrain to the cerebellum

nuclei that deal primarily with sleep, respiration, swallowing, bladder control, hearing, equilibrium, taste, eye movement, facial expressions, facial sensation and posture

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24
Q

cerebellum

A

maintenance of balance and posture

coordination of movements- especially across joints

motor learning

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25
Q

midbrain

A

tectum controls rapid orientation of the head and neck-
superior colliculus- vision
inferior colliculus- sound

substantia nigra- Parkinson’s disease

associated with sleep, wake cycles, alertness, temp regulation

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26
Q

thalamus

A

acts as a switchboard

takes information from PNS and passes to cortex

NB- hypothalamus

hormones
metabolic control e.g. hunger, body temp

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27
Q

cerebral cortex

A

it plays a key role in:
* movement
* attention
* perception
* awareness
* thought
* memory
* language
* consciousness

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27
Q

basal ganglia

A
  • a series of
    interconnected nuclei
  • movement regulation
  • skill learning
  • habit formation
  • reward systems
  • selection of appropriate
    behaviours
  • self-initiation of
    behaviours
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28
Q

Spinal cord

A

Pathways to and from the brain

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29
Q

Cell and white matter
in the spinal cord

A

the middle of the cord (that looks a bit
like an H) is made up of neurones and
other cells (grey matter).

outside cord- made up of fibres (white matter) carry information up and down the cord.

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30
Q

sensory information

A

touch
proprioception
vibration
pain
temperature

sensory information enters the spinal cord at the dorsal horn

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31
Q

Motor neurones

A

located in the ventral spinal cord

the neurones make direct contact onto muscles

stimulation causes movement

each cell is part of a motor unit

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32
Q

Muscles are controlled by a “motor pool” of Neurones

A

all motor neurones that innervate a single muscle are called a motor pool

more muscle fibres than neurones
so each fibre is innervated by a single neurone

but one neurone may innervate many fibres

The size of this innervation is important as muscles that are capable of fine movements are innervated by more neurones.

32
Q

somatotopy

A

Maps are referred to as
‘somatotopic’ when that
space is related to
locations on the body, such
that adjacent neurons in
the neural tissue respond
selectively to stimuli
presented to adjacent
locations on the body.

32
Q

Spinal White Matter

A

fibre tracts that carry information to and from the brain

33
Q

Lateral descending
system

A

The corticospinal and rubrospinal
tracts

34
Q

Medial descending
system

A

The vestibulospinal and reticulospinal
tracts

35
Q

Lateral descending system

A

The corticospinal and rubrospinal tracts make up the the lateral descending system

  • fibres of the lateral system are in the dorso-
    lateral part of the spinal cord.
  • they connect to motor neurones in the
    lateral part of the ventral horn.
  • this system influences lateral musculature.
36
Q

lateral system – round up

A

Corticospinal fibers strongly influence movement of every part of the body and is particularly useful for individual finger use.

  1. Other descending fibers, primarily the rubrospinal tract, can compensate
    almost completely for the loss of descending corticospinal input.
  2. The one ability of the descending corticospinal tract for which no other
    tract can compensate is the ability to use the fingers individually.
    Individual finger movements are the sole province of the corticospinal
    system.
37
Q

Medial system (vestibulospinal and reticulospinal tracts)

A

The vestibulospinal and reticulospinal
tracts make up the the medial descending
system.

  • fibres of the medial system are in the
    ventro-medial part white matter.
  • they connect to motor neurones in the
    medial part of the ventral horn.
  • this system influences medial musculature.
38
Q

medial systems – round up

A
  1. the medial systems are involved in the control of balance and
    posture.
  2. these functions happen with little conscious control.
  3. the vestibulospinal tract retains balance when the body is
    moved – external disturbance.
  4. the reticulospinal tract helps us retain posture and balance
    during our own volitional movements – internal disturbance.
39
Q

dorsal column pathway

A

carries sensory information
from the joint and skin about:
* fine touch.
* vibration.
* two-point discrimination.
* proprioception (position) from
the skin and joints.

40
Q

Spinothalamic pathway

A

The lateral spinothalamic tract
conveys
* crude touch.
* a sense of being touched
without knowledge of where.
* pain.
* temperature.

40
Q

Nerves

A

Regardless of where
the cell bodies are,
both the sensory and
motor axons run in
the same nerves.
* These nerves are
spinal nerves.

41
Q

Information in and out of the spinal cord

A

The cell bodies of incoming sensory neurones lie outside the spine in a
series of ganglion – called the Dorsal Root Ganglion (DRG)

This is unlike the motor neurones that have their cell bodies in the
ventral horn.

41
Q

spinal nerves

A
  • There are 31 pairs of spinal nerves.
  • The positions in the spine these
    nerves will determine what part of
    the body each spinal nerve serves.
  • Because some parts of the body
    have more muscles and more
    sensory receptors. The size of the
    nerve and the amount of
    information carried by the nerve will
    be different.
42
Q

Dermatomes

A

an area of the skin
supplied by nerves
from a single spinal
root

43
Q

Shingles

A

Chickenpox is caused by
the varicella zoster virus ).
After recovery the virus
remains in your DRG.
* Sometimes in later life the
virus can reactivate
producing a painful or
itchy rash that is isolated
to a single dermatome

44
Q

2 – point
discrimination

A

is the ability to
discern that two
nearby objects
touching the
this ability reflects
how finely innervated
an area of skin is

45
Q

Motor pools are made of motor units

A

Motor units make up motor pools:
* a lower motor neurone (or alpha
motor neurone) in the spinal
cord innervates a muscle.
* each motor neuron synapses
with multiple fibres within the
muscle. The motor neurone
and all the muscle fibres it
contacts define the motor unit.
* cross section through the muscle
shows the relatively diffuse
distribution of muscle fibres (dark
fibres) contacted by a single
motor neuron

46
Q

Spinal Enlargements

A

he arms and legs (particularly the
hands and feet) have many highly
innervated muscles and have a
high density of sensory receptors.
Because of this the portions od
the spinal cord that provide the
spinal nerves to the arms and
legs are enlarged

47
Q

information flow in a spinal segment

A
  • dorsal horn - contains sensory
    neurones. these receive
    sensory information and send
    this up to the brain.
  • Ventral horn – contain
    neurones that send messages
    directly to the muscles.
  • intermediate zone –contain
    interneurones. these integrate
    information. e.g – inhibition.
48
Q

coding in nervous systems is by action potentials

A

timulus
intensity
determines size
of receptor
potential & thus
frequency of
action
potentials

firing frequency codes for
intensity (“rate code”)
very non-linear
usually codes for intensity
of contrast between two
levels.

49
Q

rate coding in the motor system

A
  • Motor neurons use a rate
    code to signal the
    amount of force to be
    exerted by a muscle.
  • An increase in the rate
    of action potentials fired
    by the motor neuron
    causes an increase in
    the amount of force that
    the motor unit generates.
50
Q

rate coding in the motor system
- recruitment & size principle

A
  • For small forces small
    motor units are
    recruited first, as the
    required force
    increases, larger motor
    units are recruited.
  • Size principle states
    that, with increasing
    strength of input onto
    motor neurons,
    smaller motor neurons
    are recruited and fire
    action potentials
    before larger motor
    neurons are recruited.
51
Q

early effects of training
are neuronal in origin

A
  • humans before and after
    dynamic training. - Note
    the increased rate of
    tension development after
    dynamic training
  • increased rate of of tension
    achieved after training is
    accompanied increase in
    rectified surface EMG
    activity in the early phase
    of contraction.
52
Q

Subcortial control of movement

A

Title

53
Q

spinal cord reflexes
e.g. stretch reflex

A

Stretching a muscle is detected in the muscle and
leads to increased activity in sensory neurones that in
turn leads to an increase in the activity of motor
neurons that innervate the same muscle, while
inhibiting the motor neurons that innervate
antagonists.

54
Q

Reflexes

A
  • rapid automatic control of movement.
  • little or no voluntary control.
  • some are very simple:
  • stretch reflex.
  • some are more complex:
  • swallowing, breathing.
  • these mainly happen in the spinal cord and low in the brain
    stem.
55
Q

brainstem

A

the brainstem sits at the top
of the spinal cord and is
made of three parts:
1. medulla
2. pons
3. midbrain

56
Q

2 important brainstem nuclei groups

A

The reticular formation is a set of
interconnected nuclei that are
located throughout the brainstem.

The vestibular nuclei (VN) are the
nuclei for the vestibular system
and are located in the brainstem.

57
Q

Vestibulospinal tract

A

The vestibular system is thesensory system that provides the
sense of balance and spatial orientation for the purpose of coordinating movement with
balance

The vestibulospinal tract originates in the vestibular nuclei. They send
most of their output to the spinal cord and to the muscles that move
the eyes.

58
Q

Reticulospinal
Tract

A
  • the reticular formation is a set of interconnected nuclei that are located throughout the brainstem.
  • It is a very old part of the brain.
  • The reticulospinal tract originates in reticular formation.
  • These tracts function in maintaining tone, balance, and posture.
59
Q

cerebellum

A
  • the cerebellum has a very
    conserved, highly folded
    structure in all animals
  • 10% volume of the brain.
  • More than neurones than
    the cortex.
  • 69Billion v 16Billion
  • input:output connections
    ratio.
  • 40:1
60
Q

input/output (40:1)

A

Superior cerebellar peduncle
* efferent (out) pathway to the red
nucleus and the cortex (via the
thalamus) & sup colliculus.

Middle cerebellar peduncle:
* most fibres originate in the pons
* input from sensory, visual, vestibular
and motor systems.
* but its largest input is from the cortex.

Inferior cerebellar peduncle
* carries information to and from the the
spinal cord (and the body) and
vestibular nuclei

61
Q

Rubrospinal Tract

A

The red nucleus is a roughly spherical
collection of cell bodies in the midbrain.
It is called the red nucleus because it is
extremely vascular. In fresh tissue the
red nucleus is distinctly pinker than the
surrounding tissue.
The red nucleus receives a very large
input from the cerebellum and from the
primary motor cortex.

62
Q

basal ganglia

A
  • movement regulation
  • skill learning
  • habit formation
  • reward systems
  • selection of appropriate
    behaviours
  • self-initiation of
    behaviours
63
Q

2 pathways- through the basal ganglia

A
  • the DIRECT pathway
    that runs DIRECTLY
    through the basal
    ganglia
  • the INDIRECT
    pathway takes a
    longer loop through
    the basal ganglia.
64
Q

the loops start and finish in the cortex

A

DIRECT
* short loop though the basal
ganglia.
* has excitatory effect on
cortex.
* Net effect is pro-movement.

INDIRECT
* long loop through the basal ganglia.
* has inhibitory effect on
cortex.
* Net effect is anti-movement.

65
Q

the BG and cerebellum do
different/complementary things

A

basal ganglia
* damage to the BG produces
states where there is too
much, or too little movement.

cerebellum
* damage to the cerebellum
produces states where
movements can still be made,
but they are uncoordinated.

66
Q

cortical control of movement

A

title

67
Q

Brain maps - homunculi

A
  • Because of the close
    relationship with the body
    surface & muscles, both the
    primary sensory and motor
    cortex have detailed
    somatotopic maps of the body in
    them.
  • Areas of the body with many
    highly innervated muscles and
    densely packed sensory
    receptors have expanded
    representations in the brain.
68
Q
  1. primary motor cortex
A

Neurones in the primary motor cortex
have a simple relationship to movement.
They fire around 5 to 100 ms before
movement onset and can code for the
basic parameters of movement, i.e.:
* Force.
* Direction.
* Extent.
* Speed

69
Q
  1. other motor cortical
    regions exist (area 6)
A

As we have seen neurones in the
primary motor cortex have a simple
relationship with movement
parameters.
Neurones in the non-primary motor
cortex have a more complex
relationship to movement. They code
for the more complex aspects of
movement

70
Q

pre-motor cortex (orange
area 6)

A

Neurones in the non-primary motor cortex
have a more complex relationship to
movement. They code for the more complex
aspects of movement, for example:
* planning movement.
* spatial guidance of movement.
* sensory guidance of
movement.

71
Q

Supplementary motor cortex
(SMA; purple area 6)

A

Neurones in the non-primary motor cortex
code for more complex aspects of
movement. They code for the more
complex aspects of movement, for
example:
* coordinating temporal sequences of
actions.
* bimanual coordination.
* initiation of internally generated as
opposed to stimulus driven
movement *NB – the SMA is well
connected to the basal ganglia.

72
Q

SMA – bimanual coordination

A
  • A monkey is trained to
    perform a complex
    bimanual task that
    requires the animal to
    push a peanut through a
    hole to collect a peanut.
  • After a lesion of the SMA
    the animal cannot perform
    this task and the function
    does not recover
73
Q

Areas closely associated with movement

A

These area are needed for complex movements and are highly interconnected with the motor areas

74
Q

primary sensory
cortex (areas 1, 2 &
3)

A
  • touch: vibration, heat, pain, pressure.
  • Proprioception: Afferent information, including
    joint position sense, kinesthesia, and sensation
    of resistance:
  • Joint position sense: The ability to
    recognize joint position in space.
  • Kinesthesia: The ability to appreciate and
    recognize joint movement or motion.
  • Sensation of resistance: The ability to
    appreciate and recognize force generated
    within a joint.
75
Q

posterior parietal
cortex. (areas 5&7)

A
  • integration of sensory, visual
    information to execute complex
    movement in the environment.
  • representations for different motor
    effectors (e.g. arm vs. eye)
  • a command apparatus for operation
    of the limbs, hands and eyes within
    immediate extrapersonal space
76
Q

corticospinal tract

A

The most important tract in the
human for precise control of the
limbs.
* Origin:
* primary motor cortex (30%)
* Premotor, supplementary (30%)
* Somatosensory, parietal,
cingulate (40%)
* About 1 million fibers in humans.
* 90% cross at lower medulla
* All are excitatory

77
Q

Increasing complexity as we go ‘up’ in the brain

A

he complexity of the movements the
nervous system controls increases as you
move toward (and through the brain):
spinal cord – simple reflexes.
medulla – complex reflexes.
cerebellum – coordinated movement.
basal ganglia – programmed movements.
cortex – complex conscious movements.

Human Physiology- Brain (8 decks)

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