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Topic 2 – Neuronal Physiology

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Topic 2 – Neuronal Physiology Index Topic 2 – Neuronal Physiology - Resting membrane potential - The NA+-K+ pump - Channels - Graded potentials - Action potentials - Voltage-gated channels o Voltage-gated Na+ channel o Voltage-gated K+ channel § Repolarisation § Depolarisation - Propagation of action potentials Topic 3 – The Peripheral Nervous System - Efferent division o Somatic nervous system o Autonomic nervous system § Sympathetic nervous sysmte § Parasympathetic nervous system o Cholinergic neurons o Adrenergic neurons o Dominance o Rules about neurons o Neuromuscular junction o Comparison of a synapse and a neuromuscular junction Topic 4 – Skeletal Muscle - General points - Organisation of a muscle - Thick filaments - Thin filaments o Actin o Tropomyosin o Troponin - Transverse tubular system (t-tubules) - Sarcoplasmic reticulum - Contraction of a skeletal muscle fibre - Filament slide switch - Muscle twitches o Amount of fibres o Amount of force o Twitch response o Twitch summation o Tetanic contraction o ATP and skeletal muscle contraction o Direct phosphorylation o Oxidative phosphorylation o Glycolysis Topic 5 – Smooth Muscle - Similarities with skeletal muscle - Differences with skeletal muscle - Structure of smooth muscle - Dense bodies - Smooth muscle contraction ‘switch’ - Relaxation - Multi-unit smooth muscle - Single-unit smooth muscle o Pacemaker potentials o Slow-wave potentials Topic 6 – Gastrointestinal Physiology - Processes o Mobility o Secretion o Digestion o Absorption - Digestive system composition o List of organs o Importance of ‘separation’ o Digestive tract composition - Regulation of digestive function o Autonomous smooth muscle function o Intrinsic nerve pulses o Extrinsic nerves o Gastrointestinal hormones - Receptors o Types of receptors o Types of neural reflexes - Tour of the digestive system o Salivary glands § Salivia § Salivation § Functions of saliva o Pharynx o Oesophagus § Swallowing § Oropharyngeal stage § Oesophageal stage § Gastro-oesophageal sphincter o Stomach § Structure § Functions § Motility • Gastric filling o Plasticity of smooth muscle o Receptive relaxation • Gastric storage • Gastric mixing • Gastric emptying o Factors in the stomach o Factors in the duodenum § Fat § Acid § Hypertonicity § Distension • Gastric digestive juices o Types of secretory cells o Mucus secretion o Pepsinogen secretion o HCI secretion o Intrinsic factor secretion o Gastrin secretion o Stomach reduction o Stomach ulcers o Absorption o Pancreatic and biliary secretions o Pancreas § Exocrine process • Enzymatic secretion o Trypsinogen o Chyymotrypsinogen o Procarboxypeptidase o Pancreatic Amylase o Pancreatic Lipase • Aqueous alkaline secretion o Biliary system § Composition § Bile salts § Sphincter of Oddi o Small intestine Topic 7 – Endocrine Physiology - Hormones o Negative feedback control o Control of hormone release o Major endocrine organs o Other hormone producing structures o Disorders of the endocrine system § Hyposecretion • Causes • Treatment § Hypersecretion • Causes • Treatment - Absorptive state metabolism - Regulation of fuel metabolism o Pancreas § Islets of Langerhans • Insulin • Glucagon - Diabetes o Type I diabetes o Type II diabetes - Pituitary gland and hypothalamus o Posterior pituitary § Vasopressin § Oxytocin o Anterior pituitary and hypothalamus - Growth o Factors o Growth in children o Growth in soft tissue o Growth in bone o Abnormal secretion § Hyposecretion of growth hormone in children § Hyposecretion of growth hormone in adults § Hypersecretion of growth hormone in children § Hypersecretion of growth hormone in adults o Other essential growth hormones § Thyroid § Insulin § Androgen § Oestogen - Thyroid gland o Arrangement § Colloids and follicular cells § C cells o Synthesis of thyroid hormoens § Formation and storage of thyroglobulin § Iodine trapping and oxidation to iodine § Iodination § Coupling of T1 and T2 § Colloid endocytosis § Cleavage of hormones for release o Transport of thyroid hormones o Functions of the thyroid hormone § Effect on metabolic rate § Calorigenic effect § Intermediary metabolism § Sympathomimetic effect § Cardiovascular system § Growth and the nervous system o Regulation of thyroid hormone o Abnormalities of thyroid function § Hypothyroidism § Hyperthyroidism § Goiter - Parathyroid glands o Parathyroid hormone o Calcitonin Topic 8 – Reproductive Physiology - Male reproductive system o Testes o Spermatogenesis o Spermatozoa o Sertoli cells o Control of testicular function o Accessory glands o Vasectomy - Female reproductive system o Ovaries o Oogenesis o Muturation of ova o Ovarian cycle § Follicular phase • Proliferation of granulosa cells • Formation of secondary follicles • Maturation of follicles (Graafian follicle) • Ovulation § Luteal phase • Non-fertilisation • Fertilisation o Hormonal control § Control of follicular function • FSH • LH § Control of the corpus luteum - Uterine changes linked to hormonal changes in the ovarian cycle o Uterus o Menstrual cycle § Menstrual Phase § Proliferation Phase § Secretory Phase o Contraception - Fertilisation o Oviduct o Transport of sperm o At the ovum o Development form fertilisation to implantation o Implantation o The placenta Topic 2 – Neuronal Physiology Resting Membrane Potential - Resting membrane potential is where excitable cells are not producing electrical signals - ALL plasma membranes have a membrane potential (i.e. are electrically polarized) - This can be one of two things… o The separation of opposite charges across the plasma membrane; OR o The differences in the relative number of cations in the ICF and ECF - This means that there is a slight excess of positive charges on the outside of the cell, and a slight excess of negative charges on the inside of the cell - Potential is measured in units of millivolts (mV), and as such a typical nerve cell has a membrane potential of -70mV - The cells of muscle and nerve cells are excitable cells i.e. they have the ability to produce rapid, transient changes in their membrane potential when excited - The ions primarily responsible for the resting membrane potential are… o NA+ – This is greater in concentration in the ECF o K+ – Much greater concentration in the ICF o A+ The magnitude of the potential depends on the degree of separation of the opposite charges The greater the number of charges separated, the larger the potential The NA+ – K+ Pump - This pump establishes and maintains the concentration differences between NA+ and K+ at the expense of energy by essentially transporting the same number of K+ that had leaked out back into the cell, whilst simultaneously transporting the Na+ that leaked in - Inevitably this contributes to membrane potential… o 20%: Pumps 3 Na+ out for every 2 K+ transported in, resulting in more positive ions outside than inside the cell o 80%: The passive diffusion of K+ and Na+ down concentration gradients - NOTE: K+ has a much greater influence on the resting membrane potential than Na+ The Nerve/Muscle NA+ – K+ Pump Nerve and muscle cells have developed a specialized use for the membrane potential... - They are able to rapidly and transiently alter the permeability of their membranes to the ions involved to the appropriate stimulation, bringing about fluctuations in membrane potential - Rapid fluctuations in membrane potential are responsible for… o Producing nerve impulses in nerve cells o Triggering contraction in muscle cells Terminology - Excitable Tissue: Capable of producing electrical signals when excited o Nerves: Use electrical signals to receive, process, initiate and transmit messages (i.e. the body’s messenger code’) o Muscles: Use electrical signals to ‘turn on’ the contractile process o There are two forms of electrical signal… § Graded Potential: These are SHORT distance signals § Action Potential: These are LONG distance signals - Electrical signals are created by the movement of ions through ion channels in the plasma membrane… o NOTE: The magnitude of potential is directly proportional to the number of positive and negative charges separated by the membrane o Polarization: The membrane has a potential; there is a separation of charge across the plasma membrane o Depolarization: The membrane potential becomes less polarized (i.e. less negative) than resting membrane potential o Repolarization: The membrane retuens to resting membrane potential after depolarization o Hyperpolarization: The membrane becomes more polarized (more negative) than resting membrane potential Channels - The changes in the permeability of the plasma membrane to specific ions allows for ionic movement to be brought about - However, the ions responsible for carrying charge (that result in polarization) are water soluble and cannot penetrate the plasma membrane - As such, ions channels are required to move these ions across the plasma membrane; there are two types of ion channels… o Leak Channels: These are open all the time o Gated Channels: These can be open or closed in response to triggering events Graded Potentials - These are local changes in membrane potential - Occur in varying degrees - Usually produced by a specific triggering event - Gated channels open in a specific part of the membrane - They cannot spread far from the area surrounding the site of stimulation o This is because the degree of depolarization decreases with distance because the cytosol offers considerable resistance to ion movement ANY stimulus that opens a gated channel will produce a graded potential RULE: The stronger the triggering event, the more gated channels that
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