Enabling Courses: Human Biology

Transcription

1 Enabling Courses: Human Biology Module 4 Organ/System Level of Organisation Principles of Anatomy and Physiology G.J. Tortora & B. Derrickson 13 th Edition, 2012 Copyright 2012 by Biological Sciences Textbooks, Inc and Bryan Derrickson Published by John Wiley & Sons, Inc, NJ.

2 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

3 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 Systems Human body

4 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

5 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

6 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

7 Bones are composed of Compact bone Spongy bone Medullary cavity Bones have several parts: Epiphysis Metaphysis Diaphysis

8 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

9 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 ~25yrs

10 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

11 Appendicular Skeleton o The appendicular skeleton is composed of 126 bones, making up the: Upper limb Shoulder girdles Lower limb Pelvic girdles

12 Skeletal System Activity o Let s label some bones!

13 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

14 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

15 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)

16 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

17 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

18 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

19 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

20 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)

21 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.

22 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

23 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

24 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

25 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

26 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

27 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

28 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)

29 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

30 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

31 The Endocrine System o The hormone system o Hormones: chemical messengers o Key player in maintaining/regulating homeostasis

32 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

33 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 o Maintains homeostasis Endocrine System o Uses hormones (chemical messengers) o Slow-acting pathways The bloodstream o Long-acting effects o Regulates body functions o Maintains homeostasis

34 o Hypothalamus Endocrine System Structures 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)

35 Important Endocrine Glands o Important endocrine glands in the body: Pituitary gland Thyroid gland Parathyroid glands Adrenal glands Pancreas Thymus Pineal gland Gonads

36 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

37 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

38 References o Tortora, G.J., Derrickson, B., Principles of Anatomy and Physiology, 13th edn, John Wiley & Sons, Inc, USA. o Winston, R, Human, DK Publishing, London.

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