COURSE CODE: GNS 110

COURSE TITLE: ANATOMY AND PHYSIOLOGY

PLACEMENT: FIRST YEAR FIRST SEMESTER

MJ ADENIYI MSC

CELL BIOLOGY (UNIT I)

Introduction

Cell theory

Structure and function of cells

Genetics

Cells, the building block of tissues (types), organs (types) and systems

Intercellular communication (tight, gap junction and synapse)

Properties of cells

Movements within and across the cell membrane

Growth of cells

Cellular respiration

Cellular responses and sensitivity

Nutrition

Aging and death

Cell and its environment

Body fluid

Homeostasis

Tissue adaptation (hypertrophy and hyperplasia)

PHYSIOLOGY OF MUSCLE CONTRACTION (UNIT II)

Introduction

Contractile apparatus

Mechanism of skeletal, cardiac and smooth muscle contraction

oxygen debt

NUCLEUS AND THE GENE

A gene is a basic unit of inheritance capable of transmitting characteristics from one generation to another.

Genetic information is stored in form of code, carried via mRNA (transcription) out of the nucleus, decoded by tRNA and protein synthesis is earned by rRNA (translation)

Genetic disorders include mutation, sex linked disorders, nondisjunction of autosome (down syndrome), nondisjunction of sex chromosomes, mosaicism etc.

ORGANIZATION OF LIFE

Cells of related structures and functions- Tissue

Types of tissues are epithelial, connective, nervous and muscle

Tissues of related structures and functions Organs

At least there are 22 internal organs in the body

Organs of related structures and functions systems

Systems in the body include cardiovascular, nervous, endocrine, musculoskeletal, respiratory, reproductive, renal, immune, integumentary and digestive

Cell are connected to one through:

Tight junction (eg blood brain barrier, blood csf barrier , blood testis barrier).

Gap junction (eg cardiac muscles cells, monounit smooth muscles).

Synapses are junctions between a neuron and another neuron or a muscle cell

PROPERTIES OF CELLS

MOVEMENT: cells can change their position through amoeboid movement (eg white blood cells and fibroblast) and ciliary action (ovum). Cells are capable to move due to their cytoskeleton most especially the microfilaments (actin, myosin).

CELLULAR RESPIRATION takes place within the cell and results in production of energy stored in form of ATP. Aerobic respiration increases ATP production by more than 8 fold the energy release during anaerobic process

NUTRITION: All living cells require nutritive substances to grow.

RESPONSES TO STIMULI: cells do have receptors which sense any change in their environment

GROWTH AND REPRODUCTION: Eukaryotes increase in number and size through mitosis. Meiosis occurs during reproduction.

CELLULAR EXCRETION: Metabolic waste products leave the cells by passive diffusion, active transport, exocytosis.

AGING AND DEATH: The exact cause of aging is unknown but may be due to increase production of free radicals and advanced glycation end product.

Programmed cell death (beneficial death) is called apoptosis while necrosis is the death of cells in a tissue or organ caused by injury or disease.

Clinical death and biological death.

CELL AND ITS ENVIRONMENT

Body fluid is about 60% of adult male body weight and 55% of adult female body weight.

Body cells are bathed by fluid, the internal milieu (internal environment).

It is 40liters and made up of intracellular fluid ICF (22L) and extracellular fluid ECF(18L).

ECF consists of vascular fluid (the plasma (2.75L)) and interstitial fluid and lymph (12L).

Body fluid is reduced in dehydration, diarrhoea, burns etc

Body fluid as a medium for exchange of materials

The processes through which substances can be exchanged between cells and the internal environment are:

Passive Transport: Down hill movt of substances from area of higher conc. to area of lower conc. requiring no energy. Eg are diffusion, carrier mediated or facilitated diffusion. Affected by temperature, surface area, con gradient,etc.

Active transport: Uphill movt. Requires energy in form of ATP. It is against the conc. Gradient, electrical or electrochemical gradient. Eg are primary active transport (Na+-K+ATPase) and secondary active transport.

Endocytosis (phagocytosis, pinocytosis), exocytosis and bulk flow

The fluid serves as a medium through which cellular metabolism takes place.

TONICITY

The ratio of effective osmole to plasma is called tonicity

Hypertonic has greater effective osmole than plasma and tend to result in crenation of cells.

Hypotonic fluid results in swelling (eg hemolysis)

Isotonic is same as plasma.

Inorganic substances or electrolytes are expressed in milliequivalent/l , organic substances are expressed in mg/dl etc

Osmolality is the amount of osmole per kg weight of solution. Osmolarity is no of osmole per liter of a solution

CONCEPT OF HOMEOSTASIS

Steady state of internal environment despite external challenges.

Consists of receptor (input), control centre and effector

Negative feedback and feed forward feedback helps in achieving stability

Positive feedback is also known as vicious cycle

Acid/base equilibrium as a form of homeostasis

pH of the ECF is 7.35-7.45. Decrease below 7.35 results in acidosis and increase above 7.45 results in alkalosis.

pH of ICF is 7.0. Decrease below 7 results in acidosis and increase above 7 results in alkalosis.

pH is kept steady by the buffer system, respiratory and renal mechanisms.

metabolic acidosis occurs diarrhea, diabetes, etc. metabolic alkalosis occurs in vomiting and hyperaldosteroidism

Respiratory acidosis occurs during hypoventilation (high partial pressure of Carbondioxide). COPD can result in respiratory acidosis.

Respiratory alkalosis occurs during hyperventilation. Emotions, etc, pregnancy and drug abuse can result in respiratory alkalosis

High plasma hydrogen and OH ions are called acidemia and alkalemia respectively

CELLULAR ADAPTATION

Hypertrophy: Increase in size as a result of addition or recruitments of subcellular structures. Eg exercise induced cardiac hyper trophy (eccentric hypertrophy) and Left ventricular hypertrophy in congestive heart failure (concentric hypertrophy)

Hyperplasia : Increase in size of a tissue as a result of cell multiplicity

Atrophy: Decrease in size of an organ

UNIT II: MUSCLES

INTRODUCTION Muscles are specialized tissues or organ located

beneath the skin. They are excitable tissues. Excitation can be

chemical, electrical and mechanical with the production of an action potential.

CLASSIFICATION OF MUSCLES

Muscles can be classified based on four criteria: presence of striation, control, function and location.

In striated muscles, thin and thick filaments are arranged in regular pattern. Examples are cardiac and skeletal muscles.

Skeletal muscle can be consciously stimulated (voluntary muscle) and is under the control of somatic nervous system. Smooth and cardiac muscles are involuntary and are under autonomic nervous system.

Based on function, muscles can be divided into

-Antagonist: some muscles work opposite to each other

to achieve a specific movement eg the role of tricep and bicep brachii during push down and push up

-Agonist are muscles that work in unison to achieve a specific movement: Eg inspiration involves the contraction of inspiratory muscles-the external intercoastal muscle and diaphragm.

-Adductors move part of the body toward the median plane. Contraction of adductor muscles of larynx (lateral cricoarytenoid, interarytenoid and cricothyroid) pull the vocal cords together in order to produce a vocal sound

-Abductors are muscles that move the body part away from the median plane. Contraction of abductor muscles of the larynx pulls the vocal cords apart resulting in the opening of glottis during inspiration

-Suppinators cause outward and upward rotation of the body or body part.

-Pronators cause an inward rotation of body or body parts.

Based on location, cardiac muscle is form the musculature of the heart, smooth muscles are present in body viscera and skeletal muscle are in association with bone

STRUCTURE OF MUSCLES

Muscles consist of muscle cells called muscle fibers or myocytes. The composition of cellular components in muscle and the density of the components vary. However, the following are common:

Sarcolemma (muscle cell membrane), nucleus, mitochondria, golgi bodies, myofibril( microfilaments as in actin, myosin and (tropomyosin and troponin are present in skeletal and cardiac muscle only)), sarcoplasmic reticulum (calcium store house in skeletal and cardiac muscle) and (calmouduline in smooth muscle), lysosome, ribosome and rough endoplasmic reticulum.

PROPERTIES OF MUSCLE

Defatigability: While skeletal muscle is defatigable, smooth muscle are indefatigable.

Tetanus: Skeletal muscle can be tetanized because of its short refractory period.Smooth and cardiac muscles are not.

Muscle tone: Maintenance of a partial state of contraction.

Excitability: The response of muscle to stimulus through the production of action potential.

-stimulus is a change in cell environment which triggers response.

-stimulus can be weak (subthreshold), of sufficient strength (threshold) and above threshold (suprathreshold)..

-An excitable tissue responds to stimulus of sufficient strength (threshold) or suprathreshold or does not respond to weak stimulus at all. This is All-or-none principle.

-The higher the strength of a stimulus, the shorter the duration for response (action potential). Strength of stimulus α 1/time taken to produce action potential.

-Action potential is a series of changes that occur in membrane potential. It consists of resting membrane potential, depolarization and repolarization.

-Resting membrane potential is the potential difference between the exterior and interior parts of muscle cells at rest. It is -90mv in skeletal muscle and cardiac muscle and -49 to-70mv in smooth muscle. It is due to Na+-K+ atpase and leak potassium channels.

-Depolarization: This is an increase in membrane potential. It is due to influx of sodium ions into the cells. In cardiac and smooth muscle cells depolarization is prolonged due to activation of slow opening calcium channels and influx of calcium ions producing what is known as a plateau.

-Repolarization: Decrease in membrane potential towards the resting level. It is due to activation of slow opening potassium channel and efflux of potassium ions (+ve ions). The membrane potential may fall below the resting level. This is known as after hyperpolarization.

ACTION POTENTIAL IN CARDIAC MUSCLE

SKELETAL MUSCLES

Figure 1 showing the morphology of skeletal muscle

Skeletal muscles weigh about

31kg and constitute around 45% of adult male

body mass.

Morphology of skeletal muscle

TYPES OF SKELETAL MUSCLES

Morphology of skeletal muscle

NEUROMUSCULAR JUNCTION AND EXCITATION CONTRACTION COUPLING

The junction between muscle and nerve is called neuromuscular junction. It is well developed in skeletal muscle and poor in cardiac and smooth muscles.

The nerve cell ends as uncapsulated ending loosing its myelin sheath and forming motor endplate (presynaptic cell).

The motor end plate contacts the muscle fiber(postsynaptic cell ) through synaptic cleft. Cholinergic receptor are located on post synaptic membrane

Neuromuscular junction of skeletal muscle

Neuromuscular junction in smooth muscle. That of cardiac muscle looks like this

Step by step mechanism of muscle contraction

SKELETAL MUSCLE CONTRACTION

Excitation contraction coupling in smooth muscles

Spread of excitation to smooth muscles

Binding of receptors to muscarinic receptors

Development of endplate potential

Influx of calcium ion into the smooth muscle cells and binding of calcium with calmouduline. Calcium calmouduline activates light chain kinase .

Activation of myosin head (in smooth muscle) by myosin light chain kinase

Prolonged sliding of actin over myosin (latch bridge mechanism) in smooth muscle.

Some drugs enhance the activity of acetylcholine by inhibiting cholinesterase. Such drugs are called depolarizing blockers eg are neostigmine, physiostigmine.

Drug that bind nicotinic cholinergic receptors prevent transmission of signal are known as non depolarizing blockers eg are curare (block nicotinic receptor) and atropine (muscarinic receptor) .

Myasthenia gravis is an autoimmune reaction against nicotinic cholinergic receptor

Tetanus is an apparent sustained contraction due to repeated stimuli of high frequency

Fatigue is a decrease in muscular activities due to shortage of neurotransmitter, energy, and increase in lactic acid

OXYGEN DEBT

Aerobic resynthesis of energy stores does not keep pace with utilization.

Characterized by depletion of glucose, oxygen store (hemoglobin and myoglobin) and energy store (ATP phosphagen system i.e phosphorylcreatine)

Accumulation of lactic acid in tissue decreases pH.

Extra oxygen consumption post-exercise is divided into lactic acid (to remove lactic acid) and alactacid oxygen debt (to restore phosphagen system, myoglobin, etc)

THANKS