SAQ Test 3 PDF

SAQ Renal The structure & functions of nephron (Renal Lecture Slide 25 to 36) Structure & Functions Each kidney contains 1 million nephrons. One nephron is a functional unit of kidney. Consist of: Renal corpuscle - Glomerulus and Bowman’s capsule (consists of blood arrives at glomerulus...

SAQ Renal The structure & functions of nephron (Renal Lecture Slide 25 to 36) Structure & Functions Each kidney contains 1 million nephrons. One nephron is a functional unit of kidney. Consist of: Renal corpuscle - Glomerulus and Bowman’s capsule (consists of blood arrives at glomerulus through afferent arterioles. Leaves via efferent arterioles) - Filtration Membrane (allow water, metabolic wastes, ions, nutrients and other solutes to enter capsular space) Renal tubule - Long tube through which many processes takes place and urine is formed. Urine is emptied into the collecting duct system. - Proximal convoluted tubule (PCT) - Loop of Henle (Descending and Ascending limbs) - Distal convoluted tubule (DCT) (Located near afferent and efferent arterioles of glomerulus) - Collecting Duct (Makes final adjustments to the composition of urine) Steps in urine formation (Renal Lecture Slide 25 to 36 and 79) 1) Filtration 2) Reabsorption 3) Secretion 4) Excretion 1) Filtration Function of renal corpuscle - Produce filtration 2) Reabsorption & Secretion Function of Proximal convoluted tubule (PCT) - Reabsorb water, ions, and other nutrients Function of loop of Henle - Reabsorb water (descending limb) - Reabsorb Na+ & Cl ions (ascending limb) Function of distal convoluted tubule (DCT) - Active secretion of ions, drugs, and toxins. - Na+ absorption with water in exchange of H+, K+ - Under control of hormone aldosterone. 3) Excretion Collecting Duct - Reabsorbs water only in the presence of antidiuretic hormone (ADH) Normal waste products in urine (Renal Lecture Slide 78) To maintain homeostasis by regulating volume, composition of blood Involves excretion of waste products Urea Most common organic waste Produced during breakdown of amino acids Creatinine Produced in skeletal muscle from breakdown of creatinine phosphate Uric acid Produced during breakdown of ribonucleic acid (RNA) Endocrine Structure of adrenal gland & hormones (Endocrine Lecture Part 5 Slide 9 to 17) Structure of the Adrenal Glands The adrenal glands, also known as suprarenal glands, are yellow, pyramid-shaped, retroperitoneal organs located on the superior border of each kidney. They lie at the level of the 12th ribs and are firmly attached to the kidneys by a fibrous capsule. The glands are highly vascularized. 1. Adrenal cortex (Outer part) Zona Glomerulosa o Outer most layer o Produce mineralocorticoids Zona Fasciculata o Forms 78% of cortical volume o Produce glucocorticoids Zona Reticularis o Narrow band next to medulla o Produce small amount of androgens (gonadocorticoids) 2. Adrenal medulla (Inner part) o Produce catecholamines o Adrenaline (epinephrine) o Noradrenaline (norepinephrine) Hormones of Adrenal Cortex 1. Mineralocorticoids (Zona Glomerulosa) o Affect electrolyte balance in body fluids o Aldosterone o The principal mineralocorticoids o Secreted in response to low plasma Na +, low BP, high plasma K+, or presence of angiotensin II o Triggers reabsorption of sodium ions and elimination of potassium ions 2. Glucocorticoids (Zona Fasciculata) o Affect glucose metabolism o Most important are cortisol (hydrocortisone), corticosterone, and cortisone o Secreted in response to ACTH o Increase rates of glucose synthesis and glycogen formation, resulting increase in blood glucose levels o Also act as anti-inflammatory 3. The Androgens (Zona Reticularis) o Small quantities produced in both males and females o Stimulate development of pubic hair in boys and girls before puberty o Not important in adult men o In adult women, produce muscle mass, blood cell formation, and support sex drive Hormone of Adrenal Medulla The Catecholamines - Epinephrine (adrenaline) - Norepinephrine (noradrenaline) - Increase cardiac activity, blood pressure, glycogen breakdown, blood glucose levels, release of lipids by adipose tissue. Structure of pituitary gland & hormones (Endocrine Lecture Slide 20 to 39) Pituitary Gland (Location) - Also called the hypophysis - Protected by the sella turcica of the sphenoid bone - Hangs from hypothalamus by infundibulum - Divided into anterior and posterior lobes 4. Anterior Pituitary (Adenohypophysis) 5. Posterior Pituitary (Neurohypophysis) The Anterior Lobe of the Pituitary Gland - Known as adenohypophysis. It contains endocrine cells. - Cells are surrounded by a complex capillary bed called the hypophyseal portal system - Regulatory hormones from the hypothalamus diffuse onto target cell in anterior lobe through hypophyseal portal system Seven Hormones from Anterior Lobe of the Pituitary Gland 1. Thyroid-stimulating hormone (TSH) o Released in response to thyrotropin-releasing hormone (TRH) from hypothalamus o Targets thyroid gland and triggers the release of thyroid hormones. o Increases in thyroid hormones cause decrease in TRH and TSH secretion (negative feedback) 2. Adrenocorticotropic hormone (ACTH) o Released in response to corticotropin-releasing hormone (CRH) from the hypothalamus o Targets adrenal cortex and stimulates secretion of glucocorticoids o Increases in glucocorticoids cause decrease in ACTH and CRH secretion o Gonadotropins Released in response to gonadotropin-releasing hormone (GnRH) from hypothalamus o Target the male and female gonads 3. Follicle-stimulating hormone (FSH) Females o Promotes ovarian follicles development o Secretion of oestrogen Males o Promotes sperm maturation 4. Luteinizing hormone (LH) Females o Induces ovulation o Secretion of estrogens and progesterone Males o Secretion of testosterone 5. Prolactin (PRL) o Released in response to prolactin-releasing factor (PRF) from the hypothalamus o Targets mammary glands in females o In pregnancy and nursing, stimulates production of milk 6. Growth hormone (GH) Regulated by: - Growth hormone-releasing hormone (GH–RH) and growth hormone- inhibiting hormone (GH–IH) from the hypothalamus - Stimulates cell growth and replication of all cells, especially skeletal muscle and chondrocytes 7. Melanocyte-stimulating hormone (MSH) - Increases activity of melanocytes in skin to increase melanin production - Appears to be nonfunctional in adults Posterior Lobe of the Pituitary Gland - The two hormones secreted by neurons in the hypothalamus and transported to the posterior pituitary are: 1) Antidiuretic hormone (ADH) 2) Oxytocin (OXT) Antidiuretic Hormone (ADH) Stimuli for its release - an increase in concentration of solutes in the blood - decrease in blood volume and pressure Primary target is the kidneys Effects - to increase reabsorption of water Oxytocin (OXT) - stimulates contraction of uterine muscles during labour and delivery - stimulates contraction of cells surrounding milk secretory cells in mammary glands (milk letdown reflex) Nervous system Structure of neuron (Part 1b Neuron Lecture Slide 17 to 19) 1) Cell body (soma) o Large round nucleus o Prominent nucleolus o No centrioles - Cannot divide, Cannot regenerate and Cannot be replaced if lost to injury or disease o Numerous mitochondria o Produce energy o Clusters of rough endoplasmic reticulum (RER) and ribosomes o Produce neurotransmitters o Form Nissl bodies o Make neural tissue appear gray (Gray matter) Axon hillock o Thickened region near axon o Starting point for generation of action potential 2) Dendrites o Many, short, branched o Sensitive to stimulation 3) Axon o Single & long o Transmits electrical signal o Has branches (collaterals) which end in axon terminals o Communicate with other cells via synapses ChatGPT 1. Cell Body (Soma) - Contains a large, round nucleus with a prominent nucleolus. - Lacks centrioles, meaning neurons cannot divide, regenerate, or be replaced if damaged. - Numerous mitochondria provide the energy needed for neuron function. - Clusters of rough endoplasmic reticulum (RER) and ribosomes produce neurotransmitters and form Nissl bodies, which make neural tissue appear gray (Gray matter). - The axon hillock, a thickened region near the axon, serves as the starting point for generating action potentials. 2. Dendrites - Numerous, short, and branched structures. - Sensitive to stimulation, receiving signals from other neurons. 3. Axon - Single, long projection that transmits electrical signals. - Contains branches (collaterals) that end in axon terminals. - Communicates with other neurons or cells through synapses. Classification of neurons (Part 1b Neuron Lecture Slide 24 to 27) 1. Multipolar neurons Most common neurons in CNS Found in all motor neurons to skeletal muscles Multiple dendrites and 1 long axon 2. Unipolar neurons Found in sensory neurons of peripheral nervous system (PNS) Dendrites and axons are continuous, with the cell body is pushed to 1 side 3. Bipolar neurons Small and rare that are found in special sensory organs (sight, smell, hearing) 1 dendrite & 1 axon Functional Classification 1. Sensory Neurons known as afferent neurons Carry information from sensory receptors to CNS 2 types Somatic sensory neurons - Monitor external environment Visceral sensory neurons - Monitor internal environment 2. Motor Neurons known as efferent neurons Carry instructions from CNS to effectors 2 types Somatic motor neurons - Innervate skeletal muscles Visceral motor neurons- Innervate cardiac muscle, smooth muscles & glands 3. Interneurons Located in the brain, and spinal cord Connect sensory and motor neurons Responsible for distribution of sensory information and coordination of motor activity Also involved in higher functions like memory, planning & learning. Structure of spinal cord segment (Part 4b Lecture Slide 23 to 26) Each spinal segment has a pair of Dorsal roots Contain axons of sensory neurons Dorsal root ganglia Contain cell bodies of sensory neurons Ventral roots Contain axons of CNS motor neurons Dorsal and ventral roots join distally to form spinal nerves Spinal nerves are mixed nerves that have both sensory and motor fibers Gray matter - Forms “H” around central canal - Contains neuron cell bodies - Has projections (gray horns) o Posterior gray horn ▪ Contains sensory nuclei o Anterior gray horn ▪ Contains somatic motor nuclei o Lateral gray horn ▪ Found only in thoracic and lumbar segments ▪ Contains visceral (autonomic) motor nuclei o Gray Commissures ▪ Contain axons that cross from 1 side of the spinal cord to the other ▪ Connect the horns on either side of the spinal cord White matter - More superficial - Divided into 3 columns containing bundles of sensory (ascending) & motor (descending) nerve fibres tracts - Posterior white columns - Anterior white columns - Lateral white columns Structure of synapse (Part 2c Synapse Lecture Slide 38-39) Presynaptic neuron Neuron on sending side of synapse Axon terminal holds vesicles containing neurotransmitters Neurotransmitters are released and diffuse across synaptic cleft Postsynaptic neuron Neuron on receiving side of synapse Has receptors for neurotransmitters Events occurring at synaptic transmission (Part 2c Synapse Lecture Slide 40- 41) 1. An action potential arrives and depolarizes the axon terminal 2. Extracellular 𝐶a2+enters the axon terminals and triggers the exocytosis of acetylcholine (ACh) 3. ACh diffuses across synaptic cleft 4. ACh binds to receptors and triggers depolarization of the postsynaptic membrane 5. ACh is removed by AChE (acetylcholinesterase) Divisions of autonomic nervous system (Part 5b Lecture Slide 21 to 32) Autonomic Nervous System (ANS) Involved in the autonomic regulation of body functions. Uses two motor neurons to connect the CNS to effectors (cardiac and smooth muscle, glands, and fat cells). Preganglionic neurons communicate with ganglionic neurons, whose axons are called postganglionic fibers. Sympathetic division “fight-or-flight” - Preganglionic fibers leave thoracic and lumbar spinal segments - Ganglia located near spinal cord - Short preganglionic fibers - Long postganglionic fibers Effects - Increase in alertness, metabolic rate, sweating, heart rate, blood flow to skeletal muscle - Dilates the respiratory bronchioles and the pupils - Blood flow to the digestive organs is decreased - E and NE from the adrenal medullae support and prolong the effect Neurotransmitters at Specific Synapses - All preganglionic fibers (both sympathetic & parasympathetic) are cholinergic (release acetylcholine - ACh), which is excitatory - Postganglionic fibers: - Parasympathetic: Cholinergic (release ACh) → Effects can be excitatory or inhibitory, depending on the receptor. - Sympathetic: Mostly adrenergic (release norepinephrine - NE) → Effects are usually excitatory. Sympathetic Division Components 1. Sympathetic Chain Ganglia o Arises from spinal segments T1–L2. o Preganglionic fibers enter sympathetic chain ganglia, located just outside the spinal column. 2. Adrenal Medullae o Center of the adrenal glands. o Innervated by preganglionic fibers. o Modified sympathetic ganglia that function like endocrine glands. o Secrete norepinephrine (NE) and epinephrine (E) into the bloodstream. o Effects are similar to sympathetic postganglionic stimulation. Parasympathetic division “rest-and-digest” - Preganglionic fibers originate in brain stem and sacral spinal region - Ganglia located near or within target organs - Long preganglionic fibers - Short postganglionic fibers - Less divergence than in the sympathetic division, so effects are more localized Effects - Constricts pupils, increases digestive secretions, increases digestive tract smooth muscle activity - Stimulates urination and defecation - Constricts bronchioles, decreases heart rate