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SECTION 2

BIOLOGY BRIEF

You are about to learn a lot about your body, but for those who did not study A Level or higher Physical Education, Sports Science, or Biology, here is a recap to blow away the cobwebs and refresh those memories

2.1: DEFINITIONS

ANATOMY: Despite meaning “cutting open” in ancient Greek, it refers to the internal and external structures of the body, relating to questions of what and where.

 

PHYSIOLOGY: Also of ancient Greek origin, it refers to the study of the various functions of the body, relating to questions of how and why.

 

HOMEOSTASIS:

Through a plethora of physiological processes, the body maintains a state of equilibrium, which collectively is called homeostasis.

 

PROPRIOCEPTION:

An individual’s awareness of their position and movement. A ‘proprioceptor’ is a sensor that monitors position and movement.

 

CONTENTRIC CONTRACTION:

Where a muscle shortens to produce power, such as the biceps during a bicep curl.

 

ECCENTRIC CONTRACTION:

Where the muscle lengthens whilst producing force, such as the triceps during a bicep curl.

 

AGONIST vs ANTAGONIST:

Muscle pairs (skeletal muscle) situated either side of the joint, one performing a concentric contraction and the other performing an eccentric contraction, thus working together to enable movement.

 

CNS:

Central Nervous System (brain and spinal cord)

 

PNS:

Peripheral Nervous System (nervous system outside of the brain and spinal cord)

2.2: THE 6 LEVELS OF THE BODY

From the smallest to largest atom, the body can be classified on six different levels:

  • Chemical – Everything in the universe, alive or not, is made of atoms which create the building blocks for all the elements and chemicals. Chemicals that are made entirely of atoms are called elements. Thus, the smallest part of every human are the atoms, and the main elements of EVERY human are oxygen, carbon, hydrogen, nitrogen, calcium, phosphorus, potassium, sodium, chlorine, magnesium, sulphur, iron and iodine (trace elements include silicon, fluorine, copper, manganese, zinc, selenium and cobalt).

  • Cellular: A cell on the other hand relates to the chemicals which give you life, they are the smallest living part of the body and are extremely complex. They can specialise to perform certain functions, transport vital chemical elements to wherever they are needed, respond to your internal and external environment, and can divide through mitosis and meiosis as they carry your DNA which is the coding that makes you ‘you’.

  • Tissue – A group of cells which share the same function is called tissue, such as your skeletal muscle is different to your skin, your teeth are different to your tongue and there is the recently recognised tissue called fascia which has its own section at Section 4. In general, there are 4 main types of tissue:

    • Epithelial: Covers all surfaces exposed to the external environment, covers the walls of internal passages, chambers, blood vessels and the heart, and forms glands, All types lack a blood supply, relying on blood vessels nearby, yet most types have an excellent nerve supply to provide sensory information.

    • Connective Tissue: The most abundant tissue of the body as it provides the internal framework which gives the body structure. There are 6 types: loose connective tissue (adipose, areolar and reticular tissues), dense connective tissue, bone, cartilage, blood and lymph. Loose connective tissue and dense connective tissue fall under the term Connective Tissue Proper. Each type of connective tissue can be differentiated by the content of 3 distinguishable fibres: collagenous, elastic and reticular. Connective tissue has thixotropy properties in that when cold or left undisturbed it solidifies, and when warmed or moved, it liquifies. It has 5 main functions:

      • Framework

      • Transport

      • Sensory

      • Protection

      • Storage

    • Muscle Tissue: The human body has 3 different types of muscles, skeletal, cardiac, and smooth, all three enabling the skeleton to move and function and are primarily made of varying types of collagen depending on an individual’s DNA. Whilst they share the same contraction mechanisms, they are all vary regarding their microscopic appearance, strength and duration of contraction, what controls/instructs them, and what their responsibilities and thus functions are. Depending on whether a muscle specialises in speed or endurance will depend on whether they are slow or fast twitch fibre focused. (Discussed in more depth below).

    • Nerve Tissue: Composed of two types of cells, one being neurons whose structure depends on its function and location. Neurons can be classified in what information they are responsible for:

      • Sensory Neuron: Includes visceral afferents which innervate organs, and somatic afferents which transport information from the surface of the body to the CNS such as touch and extent of touch (e.g. light or heavy compression, thus can assess threshold and how much adaptation is required). Also includes proprioceptors whose responsibility is to assess position and movement of skeletal muscles to provide information about the body in space at any given moment (proprioception will be discussed in greater detail from Section 4 Fascia and onwards).

      • Motor Neurons: Includes somatic motor neurons deliver information from the CNS to the body such as muscles and skin, and visceral motor neurons which are part of the Autonomic Nervous System (ANS) instruct various organs of the digestive, respiratory, reproductive, cardiovascular, and renal systems.

      • Interneurons: the most abundant in the bodyii, these neurons are located between any two neurons, and their responsibility is to relay sensory information to various parts of the CNS, and modulate motor neuron activity.

Neurons can also be classified by how much information they relay, of which there are three types:

  • bipolar (2 processes from either end of the cell body, dendrite and axon, found in the retina of the eye).

  • unipolar (one process from one side of the cell body, including sensory neurons).

  • multipolar (most common type of neuron, the cell body having numerous dendrites to one axon, including motor neurons for skeletal muscle).

The second type of cell in nervous tissue is neuroglia, also known as glia/l cells, and they are five times more abundant in the body than neuronsii. Whilst they do not deliver sensory or motor information because they do not have electrical impulse capacity, they support and protect neurons. There are four types of glial cells in the CNS:

  • Ependymal cells

  • Astrocytes

  • Microglia

  • Oligodendrocytes

And there are two types in the PNS:

  • Schwann cells

  • Satellite cells

  • Organ – A group of different tissues which share the same function is called an organ, such as the stomach for example relies on muscle tissue, blood vessels, glands, epithelial tissue, and nervous tissue.

  • Systemic – A group of organs sharing the same function is called a system, to which there are 12 systems, noting an organ be a part of more than 1 system.

    • Integumentary (hair, skin and nails)

    • Skeletal (bones, joints, bone marrow)

    • Muscular (cardiac, smooth, skeletal)

    • Nervous (Central Nervous System (CNS): brain, and Peripheral Nervous System (PNS): spinal cord and peripheral Nerves)

    • Cardiovascular (heart, blood vessels)

    • Lymphatic (tonsils, thymus gland, spleen, lymph vessel, lymph node)

    • Respiratory (nose, nasal cavities, pharynx, larynx, trachea, bronchial tubes, lungs)

    • Endocrine (hormones, pituitary gland, thyroid gland, parathyroid gland, adrenal glands, pancreas, ovary (female), testes (male))

    • Reproductive (Female: mammary glands, fallopian tubes, ovaries, uterus, vagina, Male: accessory glands, vas deferens, penis, testis)

    • Digestive (mouth, pharynx, oesophagus, stomach, small intestine, large intestine)

    • Urinary (kidneys, ureter, urinary bladder, urethra)

  • Organismal – The highest level of organisation throughout the body is you, every human is an organism… it may seem dull from this perspective but considering the body is made of between 20,000 to 25,000 genes[i] which are all coded differently, it can be quite interesting once you have found your reason to become interested.

[i] https://ghr.nlm.nih.gov/primer/basics/gene

2.3: HOMEOSTASIS IN MORE DETAIL

As defined in 2:1 - “through a plethora of physiological processes, the body maintains a state of equilibrium, which collectively is called homeostasis.”

All systems of the body constantly utilizing all levels of the body to maintain survival and overall health, and because everyone is different, homeostasis is never truly the same for all, and rather homeostasis is an objective process that functions subjectively. Some subjective examples include:

  • some prefer colder temperatures and others warmer temperatures

  • some people have a slow metabolism and others slower

  • some have low blood pressure and others high

  • some prefer fast twitch events such as sprinting and others slow twitch such as marathons.

Although everyone is different, homeostasis functions the same, such as cooling the body down vs warming it up, despite people having varying preferred internal and external temperatures. Illness can impact homeostasis whilst the body attempts to attack any infection and heal because of it, a prime example is the common cold where some can have trouble in maintaining a comfortable internal temperature.

 

Moreover, whilst everyone is different, the concept of balance generally applies to all. Whilst it is understandable that too much of a ‘bad’ thing such as foods high in saturated fats can detrimentally impact homeostasis, too much of a good thing can also negatively impact. An example of this good vs bad applied subjectively is sleep which is something we all need for overall health and wellbeing, the concept being too little sleep vs too much sleep with each adult requiring a different amount of sleep to function optimally with some preferring as little as 5-6 hours, and others as much as 9-10 hours.

2.4: SYSTEMIC SYSTEM IN MORE DETAIL:

All eleven systems have different responsibilities and functions yet work together to maintain homeostasis, to make you ‘you’, and an impact on one system can create a butterfly effect on other systems, such as exercise (nervous and muscular) can help digestion, and healthy nutrition via digestion can help mental health (nervous and endocrine).

Note, too much of a good thing is not necessarily good however, and rather the concept is balance – homeostasis after all is based upon balance, such as rest vs exercise. This relationship between the various systems will be discussed in greater detail throughout the platform.

2.5: MUSCULAR SYSTEM IN MORE DETAIL

As skeletal muscle is the one covered the most due to the topics covered in this platform, we will save that one to last.

 

  • CARDIAC:

As suggested by the name, this muscle group is associated with the heart. Cardiac muscle can be found in the walls of the heart and their contracting-lengthening/relaxing relationships is what pumps the blood through the heart. Thus, when the muscles relax, the chambers of the heart fill with blood, and upon contracting, they push the blood back out. Rather than be controlled by the brain, it is predominantly instructed by hormones, blood ion levels and specialised nerves. As all the fibres run parallel to each other in an organised fashion, cardiac muscle appears striated (muscle fibres running parallel to form a striped effect).

 

  • SMOOTH:

Found within the walls of hollow organs such as those of the Gastrointestinal tract such as stomach and intestines, urinary tract, reproductive organs, small arteries and veins, large arteries, and also walls of the bronchi in the lungs, muscles for hair follicles, and eye muscles controlling the pupil and lensi[i].  The predominant responsibility and function of smooth muscle in the walls of hollow organs is to move fluid and food matter whilst maintaining pressure, with the ability to contract even if the muscle is overly stretched or shortened. These muscles are instructed and impacted by hormones, ion levels, pH level, temperature and stretch. Unlike cardiac or skeletal muscle, they are spindle shaped and therefore are not striated, of which there are two types of smooth muscle in accordance to their muscle fibres:

  • Single Unit: Fibres forming a large network connected by gap junctions which enables them to contract in a wave like manner when stimulated at one end, such as the walls of small arteries and veins, and the walls of hollow organs such as the intestines.

  • Multiunit: Similar to skeletal muscle, each fibre must be independently stimulated in order to produce a contraction or relaxation/lengthening, and this type of fibre is found in the walls of the bronchi in the lungs, muscles of hair follicles, large arteries, and muscles of the eye controlling the pupil and lens.

 

  • SKELETAL:

Equating to around 40-50% of body weight[ii] they are attached to your skeleton, and have these functions:

  • MOVEMENT: Through contracting mechanisms, they pull on the skeleton at various points to enable you to move those bones, to produce movement. This can be unconscious such as a reflex reaction (e.g. touching a hot surface) or sleep walking, or conscious such as running a marathon or writing/typing.

  • HEAT: The movement of skeletal muscle produces heat which helps towards the management of homeostasis. For example, your body may shiver to produce rapid contractions, and why exercise in cold temperatures keeps you warm.

  • STABILISE THE BODY/POSTURE: By attaching to the skeleton, they help to prevent your joints from dislocating and enable you to stand and move despite gravitational pressures, without them your bones would collapse in a heap.

 

PICTURE OF MUSCLE CONSTITUTION

Similar to cardiac muscle, they consist of cylindrical muscle fibres encased in endomysium which run parallel to each other creating a striated appearance. These fibres are then bundled together by perimysium to form fascicles, and the whole muscle is encased in epimysium. The epimysium is then continuous with the tendons on either end, the tendons then connect to the periosteum which is a dense layer of connective tissue that surrounds bones, except for joints. This relationship between muscles and the periosteum of bones enables the muscles to translate power from muscle fibres to bone, the more power created by the muscle increases the amount of power the bone must absorb.

To enable movement, skeletal muscles work together in concentric and eccentric contractions (see section 2:1 definitions), working as agonists and antagonists, yet one pair does not do one movement and rather groups of muscles work together. A prime example is knee flexion, the simple movement of bending the knee, requires 8 muscles to concentrically contract and 4 muscles to extend with eccentric contraction, with knee extension being vice versa (4 muscles concentrically contracting and 8 muscles eccentrically contracting). Noting this example of knee flexion is the most simple of all knee flexions, thus, the knee and ankle moving directly below the hip as if in a straight line, if the knee or ankle is not bending directly below the hip, the movement will require different and potentially more muscles. An important note is that not all of the muscles are situated in the area of movement alone, and rather involves muscles either side of the area of movement, such as the primary hip flexor, the Psoas Major, starts at the lumbar vertebra (spine of the lower back) and finishes off at the top of the inside femur (upper leg bone), thus starts and ends either side of the hip joint. Moreover, moving your right ankle can impact soft tissue as high as the jaw and skull, of which this will be discussed in greater detail in Section 4: Fascia.

 

FUN FACT: There are therapy techniques which treats the mouth and jaw to help treat as far as the ankle and calf muscles. For example, there can be a trigger point in the roof of the mouth which can release the gastrocnemius muscle in the calf (lower leg). However, a therapist requires specific qualifications in order to use such techniques to ensure they do it correctly and safely as a lack of understanding not only shows disrespect to the technique, but you the client could incur an injury. Kim learnt off the highly renowned Susan Findlay, and has successfully worked on many jaws for various reasons since qualifying.

 

SLOW vs FAST TWITCH MUSCLE FIBRES:

 

Skeletal muscles can be characterized by whether they are slow or fast twitch, thus, how quickly they need to respond to stimulus. Fast twitch fibres can respond to stimulus in 0.01 seconds and are associated with speed and strength, yet they rely on anaerobic metabolism meaning they fatigue quick. Slow twitch fibres however respond 3 times slower than fast twitch fibres and are associated with stamina and endurance, including posture, with higher amounts of myoglobin which helps oxygen levels which links with their reliance on aerobic metabolism.  An example of slow vs fast twitch is quads vs hamstrings – the hamstrings on the back of the upper leg are slow twitch, and the quads on the front of the upper leg are fast twitch.

Regarding efficiency, aerobic metabolism uses oxygen, and via the Krebs cycle, produces numerous ATP molecules which is required to generate muscle power, whereas anaerobic metabolism uses glucose, not oxygen, and via glycolysis, produces only 2 ATP’s.

As discussed in further detail in Section 4: Fascia and thereafter, how you move and hold yourself can cause dysfunction between the slow vs fast twitch muscles. For example, holding an anteriorly rotated pelvis in posture increases load on the fast twitch fibres of the quads, thus asking them to withstand stamina and endurance which they are physiologically not efficiently equipped for.

 

 

 

So now we have had a recap, and before we get going with the more advanced stuff, take a moment or 2 to just absorb it, it is important you have a good grasp of it as the following sections will make A LOT more sense meaning you get more for your money!

 

i] Premkumar, K. (2004). The massage connection: Anatomy and physiology. Lippincott Williams & Wilkins. P. 150-170.

[ii] Premkumar, K. (2004). The massage connection: Anatomy and physiology. Lippincott Williams & Wilkins.

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Know Your Body

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