Structure and Function of Muscle and Nervous Tissue What we’ll talk about…

• Structure and functional features of muscle tissues

• Structure of

• Structure and organization of the spinal cord

• Structure of peripheral nerves Skeletal muscle consists of bundles of cells wrapped in connectives tissue layers.

Epimysium

Perimysium

Endomysium H&E stain reveals striated pattern and connective tissue layers.

Cross Section Longitudinal Section

Perimysium

Nucleus

Muscle Cell

Endomysium Each is enveloped by endomysium and groups are wrapped by perimysium.

Endomysium

Capillary

Perimysium

Muscle cell

Nucleus Electron micrographs reveal the structural components of the .

T-tubule

H-band Z-disc Z-disc

M-line

Actin

Actin I-band

A-band Skeletal muscle contains cells with different mechanical and biochemical properties.

Slow-twitch

Fast-twitch Neuromuscular Junction Motor neurons innervate skeletal muscle cells at neuromuscular junctions.

Motor neuron axon

Neuromuscular junction

Skeletal muscle cell Motor neurons form synapses on muscle cells at the neuromuscular junction.

Muscle Cell

Neuromuscular Junction

Motor Neuron Axon The neuromuscular junction contains a synapse between the axon terminus and skeletal muscle cell.

Synaptic Vesicle

Axon Terminus

Basal Lamina

Acetylcholine Receptors Muscle Cell

Voltage-gated Na+ Channels

Sarcomere Cardiac muscle consists of smaller, interconnected cells called cardiomyocytes. Cardiomyocytes appear striated and have a central nucleus and connect at intercalated discs.

Nucleus Intercalated Disc

Capillary Cardiomyocytes contain , numerous mitochondria and connect at intercalated discs.

I-band

Z-disc A-band

Intercalated Disc

Mitochondria

Mitochondria Intercalated discs contain adhering junctions and gap junctions.

Intercalated Disc Sarcomere

Adhering Junction

Gap Junction

Intercalated Disc

Cardiomyoctye 1 Cardiomyoctye 2 Smooth muscle contains spindle shaped cells. Smooth muscle controls diameter of tubes such as blood vessels and bronchioles.

Smooth Muscle

Smooth Muscle Smooth muscle cells are spindle-shaped with a single, elongated nucleus.

Nucleus Cytoplasm Some organs have layers of smooth muscle oriented in different directions.

Contraction Layer 1

Nucleus

Layer 2 Dense bodies in smooth muscle cells function as Z-discs to mediate contraction.

Nucleus

Dense Bodies Cytoplasm Adhering junctions connect adjacent smooth muscle cells.

Smooth muscle cell 1

Adhering junction

Smooth muscle cell 2

Smooth muscle cell 3 Smooth muscle cells can be individually innervated or work in groups via gap junctions.

Multiunit Unitary Gap junctions allows ions and current to pass between smooth muscle cells.

Smooth muscle cell 1

Gap Junction

Gap Junction

Smooth muscle cell 2 Nervous Tissue Spinal Cord The cell bodies of motor neurons are found in the ventral horn.

Dorsal

Dorsal Horn White Matter

Ventral Horn Grey Matter Dorsal Root

Ventral Root Ventral The dorsal root contains the cell bodies of sensory neurons.

Sensory Neuron

To Spinal Cord

To Periphery Motor neurons are multiple polar neurons that are found in the ventral horn.

Dendrite

Motor Neuron

Support Cell Nissl stain labels nucleic acids and highlights the rough endoplasmic reticulum in motor neurons.

Dendrite

Nissl Bodies Motor Neuron

Axon Hillock Peripheral nerves contain three layers of connective tissue.

Epineurium

Perineurium

Endoneurium

Arteries and Veins Fascicle Myelin Axon Peripheral nerves with myelinated axons contain an unstained region around the axon.

Epineurium

Perineurium

Axon Myelin

Endoneurium Electron micrograph reveals a myelinated axon and endoneurium with collagen.

Schwann Cell

Myelin Sheath

Axon

Endoneurium Nerves with unmyelinated axons contain the same connective tissue layers.

Schwann Cell Nucleus

Epineurium

Perineurium Electron micrograph reveals unmyelinated axons and collagen in the endoneurium.

Endoneurium

Axon

Schwann Cell

Axon Peripheral nerves appear wave-like in longitudinal sections.

Schwann Cell Nucleus

Epineurium Ganglia are collections of neurons that relay signals from the CNS to the local tissue.

Neuron

Connective Tissue Satellite Cell