The Tissues of the Human Body: Muscle & Nervous Tissue

Question 1

Muscle Tissue

Answer 1

Consists of elongated cells (muscle cells; or muscle fibres or myocytes) that use energy from the hydrolysis of ATP (adenosine triphosphate)to generate force.

Question 2

Muscle Tissue

Answer 2

As a result of contraction收缩, muscle tissue produces body movements, maintains posture and generates heat.

Question 3

There are three types of muscle comprising ~50% of the body tissue mass:

Answer 3

Skeletal Muscle
Cardiac Muscle
Smooth Muscle

Question 4

Skeletal Muscle

Answer 4

There are ~650 named skeletal muscles in the body

Usually attached to bones via tendons.

Appear striated under the microscope.

Contraction收缩 is under conscious有意识的 control (voluntary自愿的; sometimes not always - posture)

Fibres纤维 (remember = cells) cylindrical圆柱形

Question 5

Skeletal Muscle Tissue

Answer 5

Location:

Attached to bones by tendons

Structure:

Long cells;
Striated;
Multinucleate (many peripheral nuclei pushed to the side)

Control:
Voluntary

Functions:
Motion, Posture, Heat, Protection

Question 6

The striations条纹 of skeletal muscle fibres (cells) are due to the highly organised arrangement of myofibrils肌原纤维 within the cells

Answer 6

Myofibrils(2 μm diam) more or less fill the cytoplasm细胞质 (sarcoplasm肌质) of the muscle fibre and extend its entire length within the cell

Question 7

The striations of skeletal muscle fibres (cells) are due to the highly organised arrangement of myofibrils within the cells

Answer 7

Myofibrils are composed of two types of filaments (myofilaments):
–Thin filaments: mostly actin; 8 nm diam; 1-2 μm long
–Thick filaments: myosin; 16 nm diam; 1-2 μm long

Question 8

Myofilaments do not extend the length of the muscle fibre but are arranged in compartments隔间 called sarcomeres

Answer 8

The sarcomere is the basic functional unit of a myofibril

Question 9

The connective tissue of skeletal muscle

Answer 9

Epimysium: surrounds anatomical muscle

Perimysium包膜: around fascicles

Endomysium肌内膜: around muscle fibres (“cell”) –(layer for capillaries/nerves)

Sarcolemma肌纤维膜: actual cell plasma membrane

Sarcoplasm肌质: cell cytoplasm

Question 10

Cardiac Muscle心肌 Tissue

Answer 10

Structure:

Striated.
Branched.
Single central nucleus.
Fibres join end-to-end through intercalated discs.

Question 11

Intercalated夹层的 discs contain:

Answer 11

1. Desmosomes细胞桥粒(bind intermediate filaments) Provide adhesion in contraction
2. Gap junctions (communication) (coordinated; rapid conduction).

Question 12

Cardiac Muscle Tissue

Answer 12

Location:

Heart

Question 13

Smooth Muscle (no striations)

Answer 13

Located in the walls of hollow空心 internal structures

e.g. intestines肠 (peristalsis); blood vessel walls (constriction); also: Iris of the eye, reproductive; digestive; respiratory; urinary; skin erector pili 皮肤毛肌

Question 14

Smooth muscle fibres are non-striated, but still have bundles束 of thin (e.g. actin) and thick (e.g myosin) filaments肌丝.

Answer 14

• Thin filaments (e.g. actin) attach to “dense bodies”, functionally similar to Z discs. (Dense body: a major protein is Actinin).
• Intermediate filaments (non-contractile elements) also connect to dense bodies

Question 15

Nervous Tissue

Answer 15

Nervous tissue is the essential component of the nervous system.

Question 16

The nervous system has two main subdivisions:

Answer 16

–Central nervous system (CNS): brain and spinal cord (and optic nerve)
–Peripheral外围的 nervous system (PNS): all nervous tissue outside CNS

Question 17

The nervous system helps to

Answer 17

Maintain homeostasis体内平衡(along with the endocrine system内分泌系统)
Initiates voluntary movements
Responsible for perception感知, behaviour and memory.

Question 18

Nervous tissue consists of two types of cells

Answer 18

neurons (nerve cells that can be very large)

neuroglia (supportive cells – usually small)

Question 19

Neurons

Answer 19

Have a cell body into which short, branched dendrites convey nerve impulses (action potentials) and from which a longer, single axon conducts nerve impulses to another neuron or tissue.

Question 20

Neurons

Answer 20

Dendrites树突: The receiving/input part of the neuron.

Axon 轴突: carries the nerve impulse away from the neuron. It is the output portion of the neuron.

For our purposes neurons: Do not divide. High metabolic rate. (die rapidly without O2)

Question 21

Multipolar多极 Neurons

Answer 21

• Have 2 or more dendrites and a single axon.
• Most common neurons in CNS
• All motor neurons (control skeletal muscle) are in this class
• Some of longest (spinal cord to toe muscles)

Question 22

Bipolar Neurons

Answer 22

• Two distinct processes–1 dendritic process (can branch at the tip but not at cell body)–And 1 axon
• Has cell body between axon and dendrite
• Rare and small (30μm)
• Special sense organs (sight, smell, hearing) relay information from receptor to neurons

Question 23

Unipolar Neuron

Answer 23

• The dendrites and axon are continuous
• Cell body off to one side
• Whole thing from where dendrites converge called the axon
• Most sensory nerves are unipolar
• Very long (1m) like motor nerves CNS-toe tip.

Question 24

Anaxonic neuron

Answer 24

• Rare and function poorly understood
• Anatomy cannot distinguish dendrites from axons
• Found in the brain and special sense organs

Question 25

Neuroglia 神经胶质

Answer 25

• Found in both CNS and PNS.
• Makeup ~50% of the volume of the CNS (“glue”).
• Smaller than neurons but more numerous (5-50x)
• Do not propagate action potentials but can communicate.
• Can divide within the mature nervous system

Question 26

Neuroglia

Functions

Answer 26

• Physical structure of nervous tissue
• Repair framework结构 of nervous tissue
• Undertake phagocytosis吞噬作用
• Nutrient supply to Neurons
• Regulate interstitial fluid组织液 in neural tissue.

Question 27

Classification of Neuroglia

1. CNS Neuroglia

Astrocytes

Answer 27

Astrocytes星形胶质细胞:

a. Star-shaped; largest; most numerous of neuroglia. Syncytium network.
b. Support (have microfilaments) and repair (scar).
c. Communicate with neurons via ‘gliotransmitters’ e.g. glutamate
d. Maintain environment around neuron by e.g. regulating ions.
e. Maintain blood-brain barrier via endothelium. Wrap around vessels and influence their permeability

Question 28

Classification of Neuroglia

1. CNS Neuroglia

Oligodendrocytes

Answer 28

Oligodendrocytes少突胶质细胞::

–Form insulating绝缘的 multilayered myelin sheath髓鞘 ( protein-lipid layer)around CNS axons.

–Can myelinate脱髓鞘 more than one neuron cell’s axon. Accelerate the action potential.

Question 29

Classification of Neuroglia

1. CNS Neuroglia

Microglia

Answer 29

Microglia小神经胶质细胞:

Phagocytic吞噬 (resident macrophages常驻巨噬细胞) - protection

Question 30

Ependymal室管膜 cells

Answer 30

Produce cerebrospinal fluid脑脊液 (CSF)

Line the Cerebrospinal Fluid (CSF)-filled ventricles心室 in the brain and the central canal of the spinal cord.

• These single layer of predominantly cuboidal cells have cilia (flow) and microvilli (sampling).
• Located in ventricles and in other locations where CSF found.
• CSF mechanical buffer; moves nutrients and waste

Question 31

Peripheral Nervous System Neuroglia外周神经系统神经胶质

Answer 31

Schwann cells雪旺细胞 (“PNS version of CNS oligodendrocyte”): form insulating myelin sheath around axons or can just support and surround several non-myelinated axons. (Note: One Schwann cell per axon for myelination but more axons/cell if just support).

Satellite cells卫星细胞: surround neuron cell bodies. Support and fluid exchange (Equiv. to astrocytes in CNS).