BioSci 107 - Muscle and Nerve Tissue

What is muscle tissue made of?

Elongated cells called muscle fibres (myocytes) that use ATP to generate force

What are the 3 functions of muscle tissue?

1. Body movement

2. Maintain posture

3. Generate heat

What are the 3 tyoes of muscle tissue?

1. Skeletal muscle

2. Cardiac muscle

3. Smooth muscle

Where is skeletal muscle found?

Attached to bones via tendons

Is skeletal muscle voluntary or involuntary?

Voluntary (concious control)

What does skelete muscle look like under a microscope?

Striated (stripped) appearance

How many skeletal muscles are in the body?

About 650 named

What are the two main skeletal muscles out of 650?

1. Stapedius

2. Sartorius

What is the structure of skeletal muscle cells

1. Long cylindrical cells

2. Multinucleate (many nuclei)

3. Striated

What are myofibrils?

Long structures inside muscle cells made of myofilaments that create striations

What are two types of myofilaments?

1. Thin filaments (actin)

2. Thick filaments (myosin)

What is a sarcomere?

The basic functional unit of muscle contraction

What separates sarcomeres?

Z discs (Z lines)

What is epimysium?

Connective tissue that surrounds the entire muscle

What is perimysium?

Connective tissue surrounding muscle fascicles (bundles of fibres)

What is endomysium?

Connective tissue surrounding individual muscle fibres

Where is the cardiac muscle found?

In the heart

Is cardiac muscle voluntary or involuntary?

Involuntary

What are the key features of cardiac muscle cells?

1. Striated

2. Branched

3. Single central nucleus

4. Intercalated discs

1. What are intercalated discs?

Connections between cardiac cells containing desmosomes and gap junctions

Where is smooth muscle found?

Walls of internal organs like intestines, blood vessels and bladder

Is smooth muscle striated?

No, it is non-striated

Is smooth muscle voluntary or involuntary?

It is involuntary

What is the shape of smooth muscle cells?

Spindle-shaped with a single nucleus

Whar are the main functions of the nervous system?

1. Maintain homeostasis

2. Initate voluntary movement

3. Perception, behavior and memory

What are the two subtypes of the nervous system?

1. CNS: brain and spinal cord

2. PNS: nerves outside the CNS

What are the 3 major nervous functions?

1. Sensory

2. Integrative

3. Motor

What are the 2 cell types in nervous tissue?

1. Neurouns

2. Neuroglia

What are dendrites?

The input/receiving part of a neuron

What is an axon?

The part of a neuron that carries impluses away from the cell body

Do neurons divide?

No, they generally do not divide

What is a multipolar neuron

A neuron with many dendrites and one axon (most common)

What is a bipolar neuron?

A neuron with one dendrite and one axon, found in special sense organs

What is a unipolar neuron?

A neuron where dendrites and axon form one continuous process

What are neuroglia?

Support cells of the nervous that assist neurons

What are the 4 CNS neuroglia?

1. Astrocytes

2. Oligodendrocytes

3. Microglia

4. Ependymal cells

What is an anaxonic neuron?

A rare neuron where dendrites and axons cannot be distinguised

Approximately what percentage of the CNS volume is neuroglia?

About 50%

Can neuroglia divide?

Yes

What do astrocytes do?

1. Support neurons

2. Maintain environment

3. Help maintain blood-brain barrier

What do oligidendrocytes do?

Form myelin sheath around CNS axons

What do micorglia do?

Phagocytosis and immune protection

What do ependymal cells do?

Produce and circulate cerebrospinal fluid (CSF)

What do schwann cells do?

Form myelin sheath around PNS axons

What do satellite cells do?

Surround neuron cell bodies and support fluid exchange

What is the smallest skeletal muslce in the human body?

Stapedius muscle in the ear

What does the stapedius muscle do?

Stabilises the stapes bone and helps prevent overly loud sounds (hyperacusis)

What is the longest skeletal muscle in the body?

Sartorius muscle

What movements does the sartorius muscle perform?

1. Hip flexion

2. Hip abduction

3. Lateral rotation

4. Knee flexion

What is hyperacusis?

Increased sensitivity to sound caused by stapedius nerve damage

What is the role of gap junctions in cardiac muscle?

Allow rapid communication and coordinated contraction of heart cells

What happens to smooth muscle during contraction?

The cell twists as tension is transmitted through intermediate filaments

What happens to neurons if they do not receive oxygen?

They die rapidly due to their high metabolic rate