BASIM ZWAIN LECTURESMEDICAL PHYSIOLOGYCELL PHYSIOLOGY - 1

Professor Dr. Basim Zwain

Faculty of Medicine

Jabir ibn Hayyan Medical University

basimzwain@jmu.edu.iq

CELL PHYSIOLOGY

Plasma MembraneThe fluid mosaic modelIntegral and peripheral proteins

CELL PHYSIOLOGY

Proteins act as:ReceptorsEnzymesCarriersChannels

ChannelsUngated (leak)Voltage gatedLigand gated

-Direct receptor channel complex-Intracellular second messenger–gated channel-NMDA (voltage and ligand gated)

Mechanically gated

CELL PHYSIOLOGY

Clinical considerationsCystic fibrosis is an autosomal recessive disease of a direct effect on ion channels caused by mutations in the cystic fibrosis transmembrane regulator (CFTR) gene, which codes for the chloride channel gated by cAMP. Deletion of single phenylalanine molecule prevents the channel protein from reaching the plasma membrane. Reduction in chloride channels results in thick mucous secretions that block airways.

CELL PHYSIOLOGY

CYSTIC FIBROSIS

CYSTIC FIBROSIS

Clinical considerationsMyasthenia gravis is an indirect ion channel disease produced by an autoimmune disorder. Autoantibodies against the AChRs lower the receptor concentration, causing lysis of the motor endplate. The decreased number of nicotinic AChRs results in smaller postsynaptic responses and a tendency to block neuromuscular transmission. Individuals with this disease experience weakness of skeletal muscles.

CELL PHYSIOLOGY

MYASTHENIA GRAVIS

BLEPHAROPTOSIS

Clinical considerationsMalignant hyperthermia is an autosomal dominant condition occurs due to mutations in the ryanodine receptor leading to an overactive receptor to halothane and muscle relaxants such as carbachol. It results in increased Ca2+ release, sustained muscle contraction, extensive necrosis of muscle cells, release of large amounts of K+, cardiac arrhythmias, and ventricular fibrillation. High Ca2+ levels leads to increased heat production. Treated with dantrolene, inhibits the receptor.

CELL PHYSIOLOGY

Clinical considerationsBrody disease is an autosomal recessive mutation in the ER Ca2+-ATPase, which leads to exercise induced impairment of skeletal muscle relaxation.Darier disease is an autosomal dominant skin disorder (dyskeratosis follicularis) due to mutations in the ER Ca2+-ATPase, leads to loss of cell adhesion.

CELL PHYSIOLOGY

BRODY DISEASE

DYSKERATOSIS FOLLICULARIS

Clinical considerationsX-linked congenital stationary night blindness is a recessive disease of human retina due to mutations in a voltage-gated Ca2+ channel, defective glutamate release and neurotransmission. Patients have difficulty adapting to low light situations, reduced visual acuity, myopia, nystagmus, and strabismusLambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disease characterized by an increased number of LEMS antibodies against voltage-gated Ca2+ channels, leads to defective neurotransmission and weakness of proximal muscles.

CELL PHYSIOLOGY

VOLTAGE-GATED CA2+ CHANNEL

CELL PHYSIOLOGY

Transport processes across plasma membrane:

Passive transport

Active transport

Passive transportDiffusion

Simple diffusionFacilitated diffusionOsmosis

Osmolality, osmolarity, isotonic, hypotonic and

hypertonic solutions.

Filtration

CELL PHYSIOLOGY

CELL PHYSIOLOGY

Active transportPrimary activeSecondary active

Symport (cotransport)Antiport (exchange)

CELL PHYSIOLOGY

CARDIAC STIMULANTSThe natural wild flower Digitalis purpurea (foxglove) and synthetic cardiac glycosides, including ouabain and digitalis, inhibit the Na+/K+-ATPase pump.