Enabling Courses: Human Biology · Muscle Tissues o Each muscle is an organ. It is composed of: • Muscle tissue (for contraction) • Nervous tissue (for impulses that will initiate

© Endeavour College of Natural Health endeavour.edu.au

Enabling Courses: Human Biology

Principles of Anatomy and Physiology

G.J. Tortora & B. Derrickson

13th Edition, 2012

Copyright © 2012 by Biological Sciences Textbooks, Inc and Bryan Derrickson

Published by John Wiley & Sons, Inc, NJ.

Module 4

Organ/System Level of

Organisation


Session Plan

o The skeletal system

• Functions

• Bone tissue

• Axial and appendicular skeleton

o The muscular system

• Functions

• Muscle tissue

o The nervous system

• Functions, structure and components

o The endocrine system

• Functions, structure and important glands


Introduction

o This module aims to introduce you to 4 body systems:

• Skeletal and muscular systems

• Nervous and endocrine systems

o Not covered: Cardiovascular, lymphatic, immune,

respiratory, integumentary (skin), reproductive, urinary

systems

o Remember:

Cells Tissues Organs SystemsHuman body


The Skeletal System

o The skeletal system is made of:

• Bone connected to other

bones (joints) with ligaments

• Cartilage

o Each bone is an organ. It is

composed of:

• Connective tissue: Bone,

cartilage, dense CT, blood,

adipose tissue

• Epithelium

• Nervous tissue


Functions of the Skeletal System

o Support for many soft organs of the body

o Protection

• Of organs such as the heart and lungs by the ribcage

o Movement

• Muscles pull on bones to make movement at joints

o Mineral homeostasis

• Reservoir of calcium and other minerals for blood

o Blood cell production in the bone marrow

o Fat storage

• Stored in the bone marrow in the form of triglyceride


Bone Tissue

o Bones are made up of 2 main types of osseous (bone)

tissue: compact and spongy bone

o Compact bone

• More solid: Gives bone its strength

o Spongy bone

• Consists of hollows: Lightens bone

• Contains red bone marrow

o Medullary cavity

• Hollow canal in the middle of long bones, filled with

yellow bone marrow


Bones are composed of

•Compact bone

•Spongy bone

•Medullary cavity

Bones have several parts:

•Epiphysis

•Metaphysis

•Diaphysis


Bone Tissue

o Osseous tissue is composed of 4 main cells:

o Osteogenic cells: “bone creating cells”

o Osteoblasts (immature): Develop from osteogenic cells

o Osteocytes (mature): Develop from osteoblasts

o Osteoclasts: “bone breaking down”: Dissolve bone tissue


Bone Growth

o The cartilage model: At birth,

most of our skeletal system is

cartilage

• Derived from the primary

germ tissue mesoderm

o As we grow, chondrocytes

(cartilage cells) are replaced

with osteocytes (bone cells)

o Ossification: Bone formation

from cartilage

o Growth is complete by ~25yrs1.

2.

3.

4.


Axial Skeleton

o The skeletal system is

divided into 2 major

sections for classification:

• Axial

• Appendicular

o The axial skeleton is made

of 80 bones, forming the:

• Skull

• Vertebrae (back bone)

• Rib cage

• Inner ear ossicles


Appendicular Skeleton

o The appendicular

skeleton is composed

of 126 bones, making

up the:

• Upper limb

• Shoulder girdles

• Lower limb

• Pelvic girdles


Skeletal System Activity

o Let’s label some bones!


The Muscular System

o Makes up ~50% of the weight of the

body!

o We have 3 types of muscle tissue:

• Skeletal (attached to our skeleton)

• Cardiac (forming the walls of our

heart)

• Smooth (found in the walls of

hollow internal organs)

o Note: When we talk about the

‘muscular system’, we are mainly

talking about skeletal muscle


Muscular System Functions

o Movement

• Muscles pull on bones to move the body and maintain

posture

o Controls movement and direction of substances

• Sphincters (dense bands of muscle) “guard”

entrances and exits throughout the body

o Maintains body temperature

• Heat is produced when muscles contract

• Rhythmic muscle contraction (shivering) quickly

raises body temperature


Muscle Tissues

o Each muscle is an organ.

It is composed of:

• Muscle tissue (for

contraction)

• Nervous tissue (for

impulses that will initiate

movement)

• Connective tissue:

tendons and tough

sheaths/layers (organise

muscle into bundles)


Muscle Tissues

o Muscle structure:

• Similar to a babushka

doll (one inside another)

o Largest level: Muscle belly

wrapped in protective

sheath of epimysium

• Epi = upon

• Myo = muscle


Muscle Tissues

o Level 2: Fascicles wrapped in

a sheath of perimysium

• Fascicles: bundles of

hundreds of muscle cells

• Peri = around

o Level 3: Muscle fibres

wrapped in a sheath of

endomysium

• Muscle fibres: muscle cells

• Endo = Inside


Muscle Tissues

o Level 4: Smallest working

component of the muscular

system: myofibril

o Level 5: Inside myofibrils,

smallest microscopic

components that do all the

work: myofilaments

(contractile proteins)

• Actin

• Myosin


Muscle Tissues

o Myofilaments: Contractile

proteins

• Actin (thin fibre)

• Myosin (thick fibre)

o Actin and myosin work

together to contract (shorten)

and relax (lengthen)

o When thousands of actin and

myosin filaments contract at

once: Muscle belly contracts,

producing movement


Muscle Tissue Summary

o Muscle belly

• Epimysium wrapping

o Fascicle

• Perimysium wrapping

o Muscle fibre

• Endomysium wrapping

o Myofibrils

o Microfilaments

• Actin (thin)

• Myosin (thick)


Inside a Myofibril

o Note: The

“sarcomere” is an

imaginary unit

o Extending from one

“Z disc‟ to the next

o The distance

between the Z discs

shorten as the

myosin and actin

fibres slide over

each other.


o The contraction of

the muscle at this

smallest level is

called “sliding

filament theory”

o Myosin “heads”

attach to actin

“binding sites”

o Myosin heads

pull the actin inward

toward the centre


Muscle Tissue Activity

o Can you remember the CT layers?

• Epimysium: Outer layer

• Perimysium: Intermediate layer

• Endomysium: Inner layer

o Can you remember the different levels

of muscle organisation?

• Muscle belly

• Fascicle

• Myofibre

• Myofibril

• Microfilaments: Actin and myosin


The Nervous System

o The skeletal and muscular systems essentially “build” a

body, like the frame of a house and the walls

o For a functional house, you need something to power it

• In the body, this is the nervous system

• Without the brain activating electrical (nervous)

impulses, the musculoskeletal system cannot function

o Nervous system: Command centre to activate most

bodily functions


The Nervous System Example

Lifting a cup to your mouth

o The brain processes information from your eyes to locate

the cup

o Nerve impulses are sent to your arm/hand to move it

towards the cup, grasp and lift it to your mouth

o Constantly monitoring the grip and weight prevent spills

o Success is a result of memories encoded in your brain

from your first cup-lifting experiences

o Your special senses register the temperature and

sensation of contents

o You will experience fullness to stop you drinking


Nervous System Functions

o Regulates body functions and

maintains homeostasis

• With the endocrine system

• Enables us to detect and

respond to environmental

changes

o Responsible for perception,

behaviour & memories

o Initiates voluntary movements

• Movement produced by

the skeletal system


Nervous System Structure

o 2 major divisions: CNS

and PNS

o Central nervous system

(CNS)

• Brain & spinal cord

o Peripheral nervous

system

• All nerves arising from

the central nervous

system


Nervous System Components

o Neurons: The basic component of the nervous system

• Specialised to conduct electrical impulses (action

potentials) throughout the body

o Structure:

• Cell body (head)

• Axon (tail)

o Action potential: An electrical charge

• Created by the movement of sodium and potassium

ions in and out of the cell

• Causes the synaptic end bulb (at the end of the axon)

to release neurotransmitters (chemical messengers)


Nervous System Components

o When a neurotransmitter is received by a target organ

(e.g. Skeletal muscle) at the neuromuscular junction, the

organ is stimulated into action

• E.g. Contraction of muscle tissue


Neuron Activity

Can you identify the following?

o Dendrites

o Cell body

• Nucleus

o Axon

• Myelin

o Axon terminals

o Synaptic end bulbs

o Direction of nerve impulses


The Endocrine System

o The hormone system

o Hormones: chemical

messengers

o Key player in

maintaining/regulating

homeostasis


Endocrine System Functions

o Regulates all body functions

• With the nervous system

• E.g. moods, production of energy, decision making,

running a marathon- even gaining motivation to

complete this module!

o Maintains homeostasis

• With the nervous system


Comparison of Nervous and

Endocrine Systems

Nervous System

o Uses nervous signals

(electricity)

o Fast-acting pathways

• Neurons

o Short-acting effects

o Regulates body functions


Endocrine System

o Uses hormones

(chemical messengers)

o Slow-acting pathways

• The bloodstream

o Long-acting effects

o Regulates body functions



Endocrine System

Structures

o Hypothalamus

• Situated in the centre of the brain (in the CNS)

• Connecting point of nervous and endocrine systems

• Produces hormones that inhibit or stimulate the

pituitary gland

o Pituitary gland

• Produces hormones (directed by the hypothalamus)

that have direct control over specific body regions

(e.g. Adrenal glands or gonads)

• Indirectly involved in most critical body functions (e.g.

Stimulating growth, reproduction, metabolism)


Important Endocrine Glands

o Important endocrine

glands in the body:

• Pituitary gland

• Thyroid gland

• Parathyroid glands

• Adrenal glands

• Pancreas

• Thymus

• Pineal gland

• Gonads


Endocrine System Activity

o Think back to Module 1

• Positive feedback and negative feedback systems

o Try to give an example of a hormone that is controlled by

a positive feedback loop

• E.g. Oxytocin: Childbirth and breast-feeding

o Try to give an example of a hormone that is controlled by

a negative feedback loop

• E.g. Calcitonin: Blood calcium levels


Summary

o The skeletal system

• Functions

• Bone tissue

• Axial and appendicular skeleton

o The muscular system

• Functions

• Muscle tissue

o The nervous system

• Functions, structure and components

o The endocrine system

• Functions, structure and important glands


References

o Tortora, G.J., Derrickson, B., 2012. Principles of

Anatomy and Physiology, 13th edn, John Wiley & Sons,

Inc, USA.

o Winston, R, 2004. Human, DK Publishing, London.


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Documents

Enabling Courses: Human Biology · Muscle Tissues o Each muscle is an organ. It is composed of: • Muscle tissue (for contraction) • Nervous tissue (for impulses that will initiate