Normal Body systems and physiology Flashcards by Jessica Russ

What is a muscle?

Soft tissue which cells are rich of protein filaments actin and myosin that slide past one another, producing contraction; derives from mesoderm.

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What are the main functions of muscle?

(Produce force and motion)
-Maintaining and changing of posture
-Locomotion
-Movement of the internal organs e.g. contraction of heart or breathing

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What are the types of muscle tissue?

Skeletal muscle tissue
Cardiac muscle tissue
Smooth muscle tissue

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What does syncytium mean? What are the two types and give examples.

Multinucleated cell that can result from multiple cell fusions of uninuclear cells.

Structural syncytium- skeletal muscle
Functional syncytium- cardiac muscle, smooth muscle

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What are the key structures of a myofiber?

Myofibrils, mitochondria, nucleus and sarcolemma

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What are the characteristics of cardiomyocytes?

-Single central nucleus
-Branching structure
-Plenty of mitochondria
-Reserve of myoglobin (to store oxygen)
-Each cell is in contact with adjacent cells

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What is a sarcomere?

Repeating functional unit of a myofibril or cardiomyocyte

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What are the two contractile filaments of the sarcomere?

Thick- myosin (fibrillar protein)
Thin- actin (globular protein)

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Explain the structure of the sarcomere.

A band (dark band)- full length of myosin (thick) filament

I band (light band)- from Z disk to the ends of thick filament. Thin filaments only

M line: centre of sarcomere, Protein where the thick filaments attach

H zone- Thick filaments, no thin

Z disk- filamentous network of
protein, attaches actin
myofilaments

Titin filaments (accessory
proteins): elastic chains of
polypeptides: keep thick and thin
filaments aligned

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What does the head and neck of a filament represent?

Head- actin binding site
Neck- ATP binding site

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What are the phases of contraction?

A) Resting stage-> ATP is hydrolysed
B) Ca2+ binds to troponin and myosin binds to actin
C) Power stroke occurs, the sarcomere contracts, ADP and Pi dissociate from myosin
D) New ATP binds to myosin, causes myosin to detach from actin, hydrolysis of ATP to ADP and pi causes reckocking of the myosin head

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What is the importance of calcium (Ca2+)?

-Ca2+ is responsible for depolarization and propagation of excitation
-Ca2+ is responsible for activation of contraction of muscles
-Ca2+ is an important signal molecule and second messenger

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b) Describe the role and action of calcium in cardiomyocyte
contraction.

Ca2+ enters through L-type channel (0.5 marks)
Ca2+ -induced calcium release (CICR) occurs, involving
stimulation of Ca2+ release from Sarcoplasmic Reticulum. (0.5
marks)
Ca2+ binds to Troponin-C on thin filaments, which exposes site
on actin which can bind to myosin head (0.5 marks)
ATP hydrolysis supplies energy for actin-myosin
conformational change (0.5 marks)
‘Ratcheting’ of actin-myosin and shortening of the sarcomere
occurs, causing myocyte contraction (0.5 marks)
Intracellular Ca2+ reabsorbed into SR via the sarco-
endoplasmic reticulum Ca ATPase (SERCA) pump and
removed from the cell via Na+/ Ca2+ exchanger and ATP-
dependent Ca2+ pump. (0.5 marks)
Ca2+ dissociates from TN-C and myosin unbinds from actin
with energy from ATP, and the binding site on actin is
inhibited. (0.5 marks)
Cycle ends when ATP binds to myosin and the sarcomere
returns to original length. (0.5 marks)

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What is the definition of epithelial tissue?

Tissue covering external surfaces of the body and lining hollow structures
(Except blood and lymphatic vessels which are lined by endothelial cells)

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What are the functions of epithelial cells?

-Defence and protection
(wear and tear, immune response)
-Secretion
-Absorption
-Exchange/communication
-Sensation

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What is the difference between single and stratified epithelial tissue?

Simple= one layer on basement membrane
Stratified= multilayer

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What is the mechanism of vascular smooth muscle contraction?

Excitation-depolarization due to opening of voltage-gated L-type Ca2+ channels
Ca2+ induced Ca2+ release from ER/SR via ryanodine receptors, increases conc of Ca2+
Ca2+ binds calmodulin
Ca2+-calmodulin complex activates myosin light chain kinase
Myosin light chain kinase phosphorylates myosin head group and stimulates contraction

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What are the two types of smooth muscles?

Vascular- arteries, veins and lymphatic vessels
Visceral- airways, gastrointestinal tract, urinary system, myometrium, pelvic organs

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What shape are smooth muscles?

Spindle-shaped

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What is the mechanism for contraction?

1&2. Excitation of Na+ channels and L-type Ca2+ channels (depolarization)
3. Ca2+ induced channels release Ca2+ from ryanodine receptors
4. Ca2+ stimulates the contractile apparatus

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What is the mechanism for relaxation?

Ca2+ reuptake into sarcoplasmic reticulum
Withdrawal of Ca2+ to the extracellular media
Exchange of Ca2+ for 3Na+ with Na2+/Ca2+ exchanger then 3Na+ exchanged for 2K+ with Na+/K+-ATPase
Activation of K+ channels
(2,3,4= repolarization)

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What are the two anatomical divisions of the endocrine system?

The central endocrine glands
The peripheral endocrine glands

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What does the central endocrine glands consist of?

Hypothalamus, Pituitary gland, Pineal gland

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What does the peripheral endocrine glands consist of?

Thyroid glands, Adrenal glands, Endocrine pancreas, Parathyroid glands

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What does the endocrine system do?

-Regulate and control important cellular & body functions -Cellular metabolism -Cell growth & development and reproduction -Adaptive changes -Circulatory and digestive systems

What are the chemical classifications of hormones?

Amines & Amino acids Polypeptides, proteins & glycoproteins Steroids

How are endocrine hormones synthesised?

Vesicle-mediated pathways -Synthesised in rER and packaged in vesicle (protein hormones) Non-vesicle-mediated pathway -Synthesised in sER and directly released (Steroid hormones)

What are the two types of hormonal receptors?

Cell surface (Receptor-ion channels, G-protein coupled receptors, Tyrosine kinase-linked receptors) Intracellular or nuclear

Why might endocrine disorders occur?

Hyposecretion (Too little), Hypersecretion (Too much), Abnormal target cell responsiveness

What are the two lobes of the pituitary glands and what do they do?

Anterior pituitary- secretes and releases 6 major hormones Posterior pituitary- stores and releases 2 hormones

Where are the hypothalamus and pituitary glands located?

In the diencephalon

What does the hypothalamus do?

Neuroendocrine transducer Chemical messages Secretion of pituitary hormones Peripheral endocrine glands

What is the role of growth hormone?

Important role in intermediary metabolism- increases free fatty acid (FFA) mobilization and use as fuel Increases blood glucose levels and decreases use of glucose as fuel

What is secretion of growth hormone modulated by?

GHRH & somatostatin from hypothalamus Ghrelin from gastric fundus

What is the function of FSH?

Stimulates growth & development of ovarian follicles. Promotes ovarian secretion of oestrogen Required for sperm production Secretion stimulated by GnRH from the hypothalamus

What does Luteinizing hormone (LH)?

Responsible for ovulation & development of corpus luteum Regulates ovarian secretion of sex hormones Stimulates testes to secrete testosterone Stimulated by GnRH from hypothalamus

What does prolactin (PRL) do?

Enhances breast development & milk production in females Overproduction can lead to infertility Inhibited by DA from hypothalamus

What are all the posterior pituitary hormones?

FSH, LH, Prolactin, Thyroid stimulating hormone (TSH), Adrenocorticotropic hormone, Vasopressin, Oxytocin.

What is vasopressin and what does it do?

Antidiuretic hormone (ADH) Controls water balance in body, promotes renal water re-absorption

Where is the pineal gland located and what does it do?

Located in diencephalon, secretes melatonin, Promotes sleep and synchronizes body's circadian rhythms with light-dark cycle

What are the two types of distinct secretory cell types?

Follicular cells- secrete tetra-iodothyronine (T4/ Thyroxine) and Tri-iodothyronine (T3) Parafollicular/ C cells- Secrete calcitonin

What are the functions of the thyroid hormone?

Normal growth & CNS development Metabolic rate & heat production Intermediary metabolism Sympathetic activity

What are the two types of secretory organs that the adrenal glands consist of?

Outer adrenal cortex Inner adrenal medulla

What are the 3 hormones secreted by the outer adrenal cortex?

Sex hormones, Mineralcorticoids, Glucocorticoids

What does the inner adrenal medulla secrete?

Catecholamines

What hormone does the pineal gland secrete?

Melatonin

What hormones do the adrenal glands secrete?

Adrenaline, Cortisol

What are the main functions of adrenaline & noradrenaline? and where are they secreted?

Secreted by the adrenal medulla Fight-or-flight increases respiratory rate, increase glycogenolysis and glucose mobilisation, increases lipolysis and mobilisation of FFA

What are the secretory cells in the pancreas called?

Islets of Langerhans

What are the 3 types of secretory cells comprised by the islets of Langerhans? and what do they secrete?

Alpha- glucagon Beta- insulin Delta- somatostatin

What is an immunogen?

Molecule that stimulates the immune system to produce a response

What is an antigen?

Part of the immunogen that reacts with immune effector cells or soluble antibodies

What is an epitope?

Part of the antigen that reacts with immune effector cells or soluble antibodies

What are the 4 types of pathogen?

Bacteria, Viruses, Fungi, Parasites

What are the classifications of lymphoid cells?

1) Small lymphocytes- B cells, T cells 2) Large lymphocytes- NK cells

What are the 3 classifications of myeloid cells?

1) Granulocytes- Neutrophil, Eosinophil, Basophil 2) Antigen presenting cells- Monocytes, Macrophages, Dendritic cells 3) Mast cells

What are the types of lymphoid organs?

Primary- Bone marrow, thymus Secondary- Speen, adenoids, tonsils, appendix, lymph nodes

What are the 2 types of immunity and what are the differences?

Innate immunity- Rapid response (hours) no memory, Fixed, Limited specificity, constant during response. Adaptive immunity- Slow response (days to weeks) memory, variable, highly specific, improve during response

What cells originate in the bone marrow?

B cells and T cells but B cells mature in it and T cells leave at an immature stage

Which cells mature in the thymus and where do they go once they differentiate?

Immature T cells migrate in thymus to complete maturation. T cells progress from cortex into the medulla.

Do immune responses occur in the primary lymphoid tissues?

No- lymphocytes are only produced and matured. Lymphocytes activated in secondary lymphoid tissues.

Where do lymph nodes lie?

At junctions of a network of lymphatic vessels

How is lymph returned to the blood vessels?

Via thoracic duct

What happens when after a pathogen is trapped by dendritic cells and macrophages in the lymphatic vessels?

B and T cells meet the pathogen and become activated, undergo clonal expansion and differentiation. As lymphocytes gross in number the lymph node increases in size (swollen glands)

What does MALT stand for and what are they?

Mucosa Associated Lymphoid Tissue- specialised tissues that are distributed in submucosal layers of the gastrointestinal, genital, respiratory and urinary tracts.