Muscular and Neural Tissue, Organs and Organ Systems: Quick Revision

A brief note on Muscular and Neural Tissue, Organs and Organ Systems. Read it before a test. Try each question at the end before you open its answer.

Muscular tissue

• Skeletal: attached to bones, striated, long unbranched fibres with many nuclei, voluntary.
• Smooth: walls of blood vessels, stomach and intestine, spindle shaped cells with one nucleus, no stripes, involuntary.
• Cardiac: wall of the heart, striated, branched, intercalated discs with gap junctions, involuntary.
• Cardiac output: the heart rate times the stroke volume.

Neural tissue

• Neuron: cell body (nucleus and Nissl granules), dendrites (bring the impulse in), axon (carries it away), axon terminals.
• Myelin sheath: made by Schwann cells, with nodes of Ranvier. The impulse jumps from node to node, so conduction is faster.
• Neuroglia: protect and support neurons, and make up more than half of the neural tissue.

Organs and organ systems

• Levels: cell, tissue, organ, organ system, organism.
• Organ: two or more tissues arranged for a job. The stomach has all four tissues.
• Wall of a hollow organ: mucosa, submucosa, muscularis, serosa.
• Organ systems: eleven in the usual count of the human body.

A worked example

A heart beats 70 times in a minute, and each beat pumps 60 mL. How much does it pump in a minute?

1. The volume is $70 \times 60\ \text{mL} = 4200\ \text{mL}$.
2. In litres this is $4.2\ \text{L}$.

Practice with new numbers

A program to try

The program names the muscle from its features.

Mistakes to avoid

• Saying that all striated muscle is voluntary. Cardiac muscle is striated and involuntary.
• Mixing up dendrites and axons. Dendrites bring the impulse in.
• Calling a tissue an organ. An organ has two or more tissues.
• Saying that neuroglia conduct impulses.

Check yourself

1. Which muscle has intercalated discs?

2. What makes a myelinated fibre fast?

3. Name the levels of organisation in order.

4. What is the cardiac output?

Sources

• OpenStax Biology 2e, chapter 33, The Animal Body: Basic Form and Function.
• NCERT (2023). Biology, Textbook for Class XI, chapter 7, Structural Organisation in Animals.