CHAPTER II PDL 101 HUMAN ANATOMY & PHYSIOLOGY. Ms. K. GOWRI. M.Pharm., Lecturer.

Transcription

1 CHAPTER II PDL 101 HUMAN ANATOMY & PHYSIOLOGY Ms. K. GOWRI. M.Pharm., Lecturer.

2 Structure of cell: Human body develops from a single cell zygote which results from fusion of the ovum andd the spermatozoan. Cell multiplication follows and as the foetus grows cells with different structural and functional specialisations develop. A cell consists of plasma membrane inside which there are a number of organelles floating in a watery fluid called cytosol.

3 Organelles are small structures with highly specialised functions : They include: Nucleus Mitochondria Ribosomes Endoplasmic reticulum Golgi apparatus Lysosomes Microfilaments Microtubules

4 Plasma membrane: Consists of 2 layers of phospholipids with some protein molecules. Phospholipids molecules have a head which is essentially enlarged and hydrophilic(water loving) and a tail which has no charge and is hyrophobic(water hating). Differences influences the transfer of substances across the membrane.

5 The membrane proteins perform functions: Branched carbohydrate molecules attached to the outside of some membrane protein molecules give the cell its immunological identity. Act as specific receptors for hormones and other chemical messengers. Some are enzymes Involve in transport across the membrane.

6 Organelles : Nucleus: contains the body s genetic material which activates the cell. Histones proteins Chromatin fine network of threads Chromosomes chromatin replicates and becomes more tightly coiled Genes subunits of chromosomes

7 Mitochondria: It is a sausage shaped structures in the cytoplasm. Sometimes described as power house of the cell. Involved in aerobic respiration. Synthesis of ATP is most efficient in final stages of aerobic respiration.

8 Ribosome's: These are tiny granules composed of RNA and protein. Synthesize proteins from amino acids using RNA as the template. Found in outer surface of endoplasmic reticulum.

9 Endoplasmic reticulum: It is a series of interconnecting membranes canals in the cytoplasm. Two types smooth and rough. Smooth endoplasmic reticulum synthesises lipids and steroid hormones. Rough endoplasmic reticulum studded with ribosomes.

10 Golgi apparatus: Consists of stacks of closely folded flattened membranous sacs. When they are packaged into membrane bound vesicles called secretory granules.

11 Lysosomes: One type of secretory vesicle formed by golgi apparatus. Contain a variety of enzymes involved in breaking down fragments of organelles and large molecules inside the cell.

12 Microfilaments: These are tiny strands of protein that provide structural support and maintain the shape of the cell. Microtubules: These are contractile protein structures in the cytoplasm involved in the movement of cell, organelles with in the cell, movement of cilia.

13 Ion channels: Active transport mechanism maintains homeostasis of the electrolytes sodium and potassium. May utilise upto 30%of the ATP required for cellular metabolism. Cations are; potassium intracellularly and sodium extracellularly. Tendency to diffuse these ions for their concentration gradients, potassium outwards and sodium into the cell. Homeostasis is maintained as excess sodium is pumped out across cell membrane in exchange for potassium.

14 Signal transduction: Signal transduction is the process by which receptor activation results in the modification of cellular structure and function. It enables extracellualr molecules to affect cellular function without entering intracellular environment. Long distance communication is accomplished by binding the against to the receptor protein and stabilising the stress in an active conformation. By the activation of intracellular pathways, gets activated by producing signals through intracellular enzymes.

15 Outcomes of signal transduction: Change in the cell membrane polarity in electrically excitable tissues such as nerves and muscles results facilitation or inhibiting the action potential. Alteration of metabolic cellular cascades results alteration in cellular function. Gene action leading to synthesis of new proteins which may modify cellular physiology.

16 Secondary messengers: G proteins activate plasma membrane bound enzymes which inturn tigger a metabolic cascade cellular response. Products are called secondary messengers. Enzymes which catalyse secondary messengers are of two categories: 1.Convert the purine biphosphate ATP and GTP to their respective cyclic monophosphates AMP, GMP. Enzymes which synthesize secondary messengers from plasma membrane phospholipids.

17 Adenyl cyclase catalyse conversion of ATP to camp. Adenylate cyclase is activated by Gs and inhibited by Gi. camp activates camp dependent protein kinases by dissociation of regulating subunits from catalytic subunits. magnitude of cellular response is proportional to concentration of camp.

18 Electrophysiology of muscle: Muscles are of three types. They are Skeletal muscle Smooth muscle Cardiac muscle

19 Skeletal muscle can be described as skeletal, striated or voluntary muscle. Smooth muscle may also described as nonstriated or involuntary. These are found in the walls of hollow organs like regulating the diameter of blood vessels and parts of respiratory tract. Propelling contents of ureters, ducts of glands and alimentary tract. Expelling contents of urinary bladder and uterus.

20 Muscle functions by alternate phases of contraction and relaxation. Skeletal muscles are stimulated by motor nerve impulses originating in the brain or spinal cord. Smooth and cardiac muscle have intrinsic ability. Muscle fibres contract all or none law.

21 Neuronal function: Nervous system consists of a vast number of cells called neurons. Neurons supported by connective tissue neuroglia. Each neuron consists of cell body and its processes one axon and many dendrites. Bundles of axons bound together called nerves. Neurons can synthesize chemical energy only from glucose. Physiological units of nervous system are nerve impulse or action potentials.

22 Neurons are actively involved in conducting nerve impulses. Neurons initiate nerve impulses while others act as relay stations whose impulses are passed on and sometimes redirected.