M edSci 2 — Excitables
10/8/08
Slide 1
Slide 2
Lecture 2 —
Muscle
• Structure, innervation &
function
– Smooth
– Cardiac
– Skeletal
• Muscle-fibre types
Nervous Tissue
– Cells
– Fibres
Dr Alan Tuffery — Physiology
Muscle — three types
Excitable Tissues
a) Fibres,
striations,
peripheral
nuclei
Learning Outcomes
To be able to:
1. describe the structure and
function of the different
types of muscle
2. comment on their
appearance in section
3. describe the fibre-types of
skeletal muscle
4. define a motor unit
5. describe the structure and
function of a neurone
6. describe myelinated and
nonmyelinated nerve axons.
Medical Sciences Physiology 2008/09
1
Slide 3
a) Skeletal muscle
b) Fibres
(branching),
striations,
central
nuclei
b) Cardiac muscle
c) Cells,
central
nuclei
c) Smooth muscle
From Passmore & Robson
Dr Alan Tuffery — Physiology
Medical Sciences Physiology 2008/09
2
Slide 4
Smooth muscle
From Stanfield & Germann 1.2
Inner layer
Plane of section:
Outer layer
Plane of section: transverse
Orientation: longitudinal
Smooth muscle — innervation
Stanfield & Germann 12.35
•
• ‘Neurogenic’
– Variable force
– E.g. airways, large arteries
• Relatively little
contractile apparatus
•
• Innervation
– Dual
(stimulatory/inhibitory)
– Weak contraction
– ‘Tone’
– Graded, spreading
contraction.
Medical Sciences Physiology 2008/09
3
Single-unit
– Greater diffusion distance
– Cells coupled
– Synchronous contraction
• Functions
Dr Alan Tuffery — Physiology
Multi-unit
– Each cell innervated
longitudinal
Orientation: circular
• ‘myogenic’
– E.g. Gut, uterus.
Dr Alan Tuffery — Physiology
Medical Sciences Physiology 2008/09
4
1
M edSci 2 — Excitables
10/8/08
Slide 5
Slide 6
Cardiac muscle
Cardiac muscle
From Stanfield & Germann 1.2
Top
• Function
Cardiac muscle
– All-or-none (‘twitch’)
– Highly resistant to
fatigue
Large cells/fibres,
central nuclei
Below
• Innervation
Purkinje fibres
Dr Alan Tuffery — Physiology
Medical Sciences Physiology 2008/09
(electrical conduction)
Stanfield & Germann 13.10
– Pacemaker cells
– Electrical conduction
(Purkinje fibres —
yellow in fig.)
5
Slide 7
Modified cardiac
muscle
Pale (unstained glycogen).
Dr Alan Tuffery — Physiology
Medical Sciences Physiology 2008/09
6
Slide 8
Skeletal muscle
Skeletal muscle — tongue
• Fibres
• Long, unbranched fibres
• Peripheral nuclei
• Most developed
contractile apparatus
Stanfield & Germann 12.2
• Arrangement
• 3 directions,
mutually at right
angles
• Many peripheral nuclei
• All-or-none, twitch
• Specialised muscle-
White adipose tissue.
fibre types.
Dr Alan Tuffery — Physiology
Medical Sciences Physiology 2008/09
7
Dr Alan Tuffery — Physiology
Medical Sciences Physiology 2008/09
8
2
M edSci 2 — Excitables
10/8/08
Slide 9
Slide 10
Motor endplate
Skeletal muscle — striations
(teased, silver-impregnated preparation)
Striations due to
alignment of filaments of
myofibrils
• One endplate per
muscle fibre
• Large,
myelinated
(alpha) axons.
Stanfield & Germann 12.3
Review sliding filament theory.
Dr Alan Tuffery — Physiology
Medical Sciences Physiology 2008/09
Dr Alan Tuffery — Physiology
9
Slide 11
Medical Sciences Physiology 2008/09
Slide 12
Motor Unit
Muscle-fibre types (SDH)
SDH — mitochondrial
enzyme (activity)
Motor unit
•
G&S Fig. 13.25
•
10
All the muscle fibres
innervated by a single
neurone
Dark: Type I
Light: Type II
Mosaic arrangement
All the fibres are of the
same type (later)
•
All fibres of a motor unit will
contract together
•
Implications?
Dr Alan Tuffery — Physiology
Neurone determines
properties
Note higher density of dark-stained capillaries around Type I fibres
(See summary table in manual).
Sherwood Fig. 8-15
Medical Sciences Physiology 2008/09
11
Dr Alan Tuffery — Physiology
Medical Sciences Physiology 2008/09
12
3
M edSci 2 — Excitables
10/8/08
Slide 13
Slide 14
Nervous Tissue
Nerve Cells
Haematoxylin & Eosin
(left)
• Cells — neurones
 Cell body
 Processes
Nerve cells
Large, pale nuclei, dark
nucleoli,
blue granules
Axons — outgoing
Dendrites — incoming
Glia/satellite cells
• Distinguish:
 anatomical nerve (named)
Methylene Blue
Nerve fibres
 nerve branches/bundles
Pale (lipid)
Axon stained pink/purple
 nerve axon
 nerve fibre (myelinated).
Sherwood Fig. 4.14
Dr Alan Tuffery — Physiology
Medical Sciences Physiology 2008/09
13
Slide 15
Dr Alan Tuffery — Physiology
Nerve cell body
Large, pale nucleus,
prominent nucleolus,
granules (ribosomes),
processes
Note. Small nuclei —
glial cells.
Medical Sciences Physiology 2008/09
14
Slide 16
TS Nerve fibres
Generalised synapse
(H&E vs Osmium staining)
Key features
H&E (no lipid)
Stained:
axon,
endoneurium
• Presynaptic side
separated by a gap
from post-synaptic
side
• Signalling by chemical
neurotransmitter
OsO4— frozen section
(lipid only)
Stained:
myelin sheath.
• Most synapses are
nerve-nerve.
Junqueira & Carneiro (2003)
Dr Alan Tuffery — Physiology
Medical Sciences Physiology 2008/09
15
Dr Alan Tuffery — Physiology
Medical Sciences Physiology 2008/09
16
4
M edSci 2 — Excitables
10/8/08
Slide 17
Slide 18
Muscle-fibre type-grouping
Learning Outcomes 1
Type I grouping
Normal mosaic
replaced by group.
Mechanism:
denervation of Type
IIs and re-innervation
by adjacent ‘Type I’
axons.
To be able to:
1. describe the structure and function of the different
types of muscle
 Smooth, cardiac, skeletal (type of contraction, innervation
etc)
2. comment on their appearance in section
 Position and rel. size of nucleus (presence/absence in
profile)
3. describe the fibre-types of skeletal muscle
 Type I , II, enzymes, properties.
Dr Alan Tuffery — Physiology
Medical Sciences Physiology 2008/09
17
Dr Alan Tuffery — Physiology
Medical Sciences Physiology 2008/09
18
Slide 19
Learning Outcomes 2
To be able to:
4. define a motor unit
• All the muscle fibres supplied by a single neurone
5. describe the structure and function of a neurone
– Processes, nuclear form, nucleolus, granules
6. describe myelinated and nonmyelinated nerve axons.
• Myelin: wrapping of cell membrane (lipid).
Dr Alan Tuffery — Physiology
Medical Sciences Physiology 2008/09
19
5