Exercise 2

Test yourself with these questions.

 

1- A rugby player suffered a knee injury when he was tackled. Identify the joint involved and all movement made by this joint. List all joints categorized according to structure and functions. Give an example where these joints could be found.

 

2- A race-car driver crashed and slipped into a coma. The doctors put him on a mechanical ventilator to help him breath. Why does he need helps in his breathing? Explain the process of respiration. How does a mechanical ventilator helps unconscious person breath?

 

3- A young female was admitted into the hospital with abdominal pain and vaginal bleed. Earlier that month, she was tested positive for pregnancy using a home pregnancy kit. The doctors later diagnosed her of having ectopic pregnancy. Explain what does this mean. How should a normal pregnancy be? Identify the process involved in ovulation that ends with a successful pregnancy.

 

4- A strong swimmer was doing his usual swimming routine in an outside pool after a cold frosty night. He eventually suffers hypothermia. Explain what does this mean. What are the symptoms of hypothermia and what are the cause of these symptoms?

 

 

The Nervous System

The functional unit of the nervous system is nerve cell or neuron.

A nerve tissue consists of hundreds of nerve cells (neurons) and neuroglial cells (Greek: glue), blood vessels, and connective tissues.

 

Neurons (nerve cells)

In general, neuron consist of three parts: dendrites, cell body (soma), and axon.

There are three structural classifications of neurons:

  1. Multipolar – which carry 1 axon and several dendrites
  2. Bipolar – which carry 1 axon and 1 dendrite, and
  3. Unipolar – where the axon and dendrite are fused together. Thus, unipolar neurons are also referred as pseudopolar.

Neurons can also be classified by its functions. There are:

  1. sensory or afferent neurons
  2. motor or efferent neurons
  3. interneuron or association neurons – these are mainly found in the central nervous system

Other than neurons, which capable of generating and propagating action potential, the nervous system also contains neuroglials cell which are neither excitable nor conducive. These cells mainly function to maintain the well being of neurons. There are six types of glial cells:

  1. astrocytes
  2. oligodendrocytes
  3. microglia
  4. ependymal cell
  5. schwann cell, and
  6. satellite cell

You can find great explanation of the neurons from AnataomyZone. Here is an example.

 

 

 

 

Action potential

Neurons are unique because not only that they can propagate electrical stimulus or nerve impulse (conductivity), they also generate electrical stimulus. This electrical stimulus is action potential generated by differences in Ca+ and K+ concentration inside and outside of the neurons.

 

 

 

 

 

The nervous system

The nervous system can also be categorized according to structure (anatomical) and function.

 

Structurally, the nervous system is divided into:

  1. Central Nervous System (CNS) – this consist of the brain and the spinal cord
  2. Peripheral Nervous System (PNS) – this consist of all nerve branches outside of CNS (12 pairs of cranial nerves (CNI-XII) and 31 pairs of peripheral nerves)

 

Functionally, the nervous system is divided into:

  1. Somatic Nervous System (SNS)
  2. Autonomic Nervous System (ANS) – is divided further into Sympathetic and Parasympathetic Nerves
  3. Enteric Nervous System (ENS) – controls the gastrointestinal (GI) tract independent of SNS and ANS.

The ENS is functionally divided into myenteric plexus (plexus=network) which controls contraction of smooth muscles, and plexus of Meissner in the submucosa layer of GI tract. Plexus of Meissner controls secretion of the organs in GI tract.

However, there is minor involvement of ANS in the nervous control of the GI tracts. The GI tracts receive innervation by parasympathetic fibres from CN-X (cranial nerve-10) and S2 (sacral-2), and sympathetic fibres from thoracic and upper lumbar region of the spinal cord.

 

 

 

 

Reflex and reflex arcs

 

The brain is responsible for processing (integrating) all information such as sensory information, learning and memorization, and personality development.

However, there are some information that was not process in the brain. Instead, information is processed only in the brain stem and spinal cord. In this case, information from sensory receptor travels through the reflex arcs (reflex circuits) in the brain stem or the spinal cord and out to the motor neurons into effector (organs). Bypassing the brain ensure rapid and immediate rapid responses during dangerous situation such as touching a hot kettle, slamming on the brake while driving, or closing the eyes when a fly flew at your face. Often, reflexes are learned and acquired from experiences.

 

 

reflex_arc_med

General component of a reflex arc. Information was not send to the brain. Instead, it enters the spinal cord through dorsal ganglion, processed in the grey matter of the spinal cord, and sent back out to the effector organs through motor neuron in the ventral root of the spinal cord.

 

There are four types of reflexes depending on where integration (information processing) happens or the effector organs involved:

  1. spinal reflex
  2. cranial reflex
  3. somatic reflex
  4. autonomic (visceral) reflex – visceral refers to inner organs such as digestive tract, heart, kidney, etc.

 

 

Exercise

1- Compare and contrast between SNS and ANS

2- Compare and contrast between somatic reflex and visceral reflex.

3- Compare and contrast between cranial reflex and spinal reflex.

3- List the components of reflex arc. Explain the process that happens when someone closes their eyes when a fly flew at their face.

 

 

The Cardiovascular (Cardiac and Blood Vessel) System

The cardiovascular system regulate distribution of blood through the body. The system involves the cardiac / heart and the blood vessels.

 

The Cardiac System

The heart is about the size of a fist. Despite its small size, the heart is capable of pumping blood through the whole body. This is made possible by heart’s special anatomy.

The heart contains four chambers: right atrium, right ventricle, left atrium, and left ventricle. The atrium receives oxygenated or deoxygenated blood and send it into the ventricles. The ventricles then pumps blood out of the heart either to the lung (right ventricle) or to the whole body (left ventricle). The walls of the left ventricle are thicker than the rest of the heart so that it could generate enough force to pump blood to the whole body. In addition, semilunar valves, tricuspid, and bicuspid valves are strategically placed inside the heart to prevent blood backflow when the heart is pumping (or when your doing head stand).

 

heart-anatomy

 

The heart muscle (cardiomyocytes) also contains features different from the skeletal muscles to ensure effective pumping function. These features are:

  1. Shorter and branched cells
  2. Intercalated discs connecting neighboring muscle fibres
  3. Smaller sarcoplasmic reticulum to ensure smaller Ca2+ reservoir
  4. Bigger and higher number of mitochondria for higher ATP generation
  5. Autoryhtmic for regular and constant muscle contraction. In this case, special patch of cardiomyocytes (sinoatrium – SA node) generate electrical impulse at constant rate to keep the heart pumping (contracting). SA node is body’s natural pacemaker.

The electrical impulse then travelled through the heart via special cardiomyocyte fibres that could conduct electrical impulses efficiently. These fibres are atrioventricular (AV) node, bundle of His, bundle branches, and Purkinje fibre.

 

 

 

 

The Blood Vessels

The blood vessels also play important role helping the heart distribute pumped blood through the body. The special features for this purpos are:

  1. Presence of smooth muscle innervated with sympathetic nerve fibres to regulate blood pressure.
  2. Presence of thick smooth muscle to withstand pressure from pumped blood.
  3. Presence of elastic fibres to propel blood forward.
  4. Presence of sphincter to regulate blood flow into the much thinner and fragile cappilaries.
  5. Presence of valve to prevent blood backflow.
  6. Located between skeletal muscles to help pump blood forward.

 

 

 

Exercises

1- Write the sequence of cardiac cycle. What happens during ventricular systole and ventricular diastole?

2- Explain how special features of cardiomyocytes ensure a proper and efficient function of the heart?

3- A man suffers from gunshot wound. He is bleeding profusely and exhibits systolic blood pressure of 40 mmHg; weak pulse of 200 beats/minute; cool, pale, and clammy skin, and he is consistently asking for water despite not producing any urine. Explain what caused his symptoms.

 

 

 

 

 

 

 

The Integumentary System

The integument (skin) is the largest organ in the body. Structurally, the skin can be divided into two parts:-

  1. Epidermis – thinnest and outer portion of the skin. Generally made of 5 layers of keratinocytes (skin cells) of different stage of differentiation i.e. stratum corneum, startum lucidum, startum granulosum, startum spinosum, and stratum basale (stratum=layer)). On top of these, there are other specialized cells in the epidermis: melanocytes, Langerhans, Merkel cells.
  2. Dermis – thickest and deeper part of the skin. Is connective tissue which contains skin accessories such as hair and hair follicles, skin glands, sensory receptors, and nails.

Deeper than dermis is the subcutaneous / hypodermis layer which contains adipose (fat) tissue and areolar connective tissue. The hypodermis is not part of the skin but function as anchor for the skin. It also contains blood vessels.

 

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The skin carry several functions and is important at maintaining body homeostasis:

  1. thermoregulation
  2. protection
  3. vitamin D synthesis
  4. blood reservoir
  5. sensation
  6. excretion and absorption

 

 

Here are detailed explanation on the integumentary system:

 

 

 

Exercises

 

1- Explain how the skin regulate body temperature when a person is jogging in a hot day and a person taking a quick swim in cold weather.

2- Explain what causes the different skin colour in a Caucasian (e.g. an English man) and an Asian. Why do skin cancer (malignant melanoma) happens more often in people with lighter skin compared to people with darker skin colour.

3- Explain why some drugs can be delivered through the skin.

4- Identify the reflex pathway involved when a hand touches a hot kettle.

 

 

 

Exercise

Once you’ve done with your revision, test yourself with these questions:

 

Cell

Arm

Epithelial

 

Structure location