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MCD > Tissues 2 > Flashcards

Tissues 2 Flashcards

1
Q

Name the 4 cerebral hemispheres and locate them

A

Frontal, Temporal, Parietal, Occipital

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2
Q

Name the convoluted ridges of the brain

A

Gyri are the ridges

Sulci are the grooves

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3
Q

What is the brainstem composed of

A

Midbrain, pons and medulla

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4
Q

What is the function of the brainstem

A

Target source of all cranial nerves with numerous functions

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5
Q

Locate the cerebellum and give its function

A

Hindbrain attached to the brainstem

Motor coordination, balance and posture

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6
Q

What is the function of the spinal cord

A

Conduit for neural transmission

Co-ordinates some reflex actions

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7
Q 
Outline the following:
Unipolar
Pseudo-unipolar
Bipolar
Multipolar
A

Unipolar - 1 axonal projection (Rare)
Pseudo-unipolar - single axonal projection dividing into 2
Bipolar - 2 projections from the cell body
Multipolar - numerous projections from the cell body (only 1 axon)

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8
Q

Give 3 examples of multipolar neurones

A

pyramidal
Purkinje
Golgi

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9
Q

Describe astrocytes

A

Most abundant in the CNS
Able to proliferate
Neuroglial

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10
Q

What are the functions of astrocytes

A

Structure
Cell repair
Immune cells
Neurotransmitter release and re-uptake

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11
Q

Describe an oligodendrocyte

A

Variable morphology and function
Numerous projections that form internodes of myelin
Myelinates axons

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12
Q

What is the function of Schwann cells

A

Produces myelin for peripheral nerves

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13
Q

What is the function of Microglial cells

A

Immune functions in the CNS

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14
Q

What is the function of ependymal cells and where is it found

A

Regulates the production and movement of cerebrospinal fluid. Found lining fluid filled ventricles

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15
Q

Explain the process of intracellular communication through a synapse

A
  1. AP propagates along the axon
  2. AP opens voltage-gated channels at the presynaptic terminal
  3. influx causes vesicle exocytosis
  4. NT binds to receptors on the post synaptic membrane to activate them for post-synaptic activity
  5. NT dissociates from the receptor and is metabolised by enzymes in the synaptic cleft or is recycled by transporter proteins
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16
Q

Give some common features of neurones

A

Soma - contains nucleus and ribosomes
Axons - originates from the soma at the axon hillock and branch off into collaterals (myelinated)
Dendrites - highly branched endnote covered in myelin, receiving signals from other cells

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17
Q

What are the 4 major physiological ions for RMP

A

potassium, sodium, chloride, calcium

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18
Q

How is resting membrane potential generated in neurones

A

Cell membranes are impermeable to some ions so transportation is regulated by channels and pumps which cause uneven ion distribution. Differences in concentration produces the potential difference

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19
Q

Describe the process of action potential generation in neurones

A
  1. sodium channels open to induce sodium influx
  2. depolarisation
  3. potassium channels open at a slower rate
  4. depolarisation of the cell
  5. sodium potassium ATPase restores the gradient
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20
Q

What is the function of myelin

A

Prevents AP propagation

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21
Q

What is the function of nodes of Ranvier

A

Provides small gaps that the AP can jump across for faster transmission

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22
Q

What is the function of skeletal muscle

A

Produces movement relative to the external environment

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23
Q

What do antagonist muscle pairs consist of

A

Flexor (bicep)

Extensor (tricep)

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24
Q

What is isotonic contraction ands what are the two types

A

Muscle changes length while tension remains the same
concentric - shortening
eccentric - lengthening
muscle tension > force exerted by load

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25
Q

What is isometric contraction

A

tension develops but muscle does not change in length e.g. carrying a bag
muscle tension = force exerted by load
myosin heads reattach to the same point on the actin chain

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26
Q

Describe the ultrastructure of skeletal muscle myofibres

A 
Consists of myofibres (bundles)
large and cyclindrical
multinucleated
packed with myofibrils
sarcoplasmic reticulum - calcium stores 
T-tubules
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27
Q

Describe the structure of a sarcomere

A

Z-line - Lateral boundaries
Actin - Polymeric thin filament composed of two twisted 𝛼-helices - displays polarity
Myosin - Thick filaments with globular heads that interact with actin
Titin - Very large springy filaments anchoring myosin to the Z-line
Nebulin - Large filaments associated with actin
Tropomyosin - Elongated protein bound to actin
CapZ & Tropomodulin - associated with +ve & –ve ends of actin, respectively

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28
Q

Explain sliding filament theory

A
  1. Ca2+ release -> movement of troponin from tropomyosin
  2. Exposure of the myosin binding site on the actin chain
  3. Charged myosin heads bind to the exposed sites
  4. Binding + ADP discharge causes the myosin head to pivot (power stroke), pulling the actin filament towards the centre of the sarcomere
  5. ATP binding releases myosin head from the actin chain
    ATP hydrolysis provides energy to recharge the myosin head
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29
Q

Explain the process of excitation in skeletal muscle

A
  1. Action potential propagates along the myofibre membrane (sarcolemma) 7 T-tubules
  2. Depolarisation activates dihydropyridine receptors (DHPR)
  3. Conformational change in DHPR
  4. Transmission to ryanodine receptors (RyR) on sarcoplasmic reticulum
  5. Opening of RyR & release of Ca2+ from intracellular stores
  6. Depolarisation -> increase in intracellular Ca2+
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30
Q

What are the pacemaker cells of the heart

A

SA node : small empty spindle shaped cells that are spontaneously active
AV node: spindle shaped network of cells at the base of the right atrium

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31
Q

What are the conducting fibres of the heart

A

Bundle of His: fast conducting cells adjoining AV node and Purkinje fibres
Purkinje fibres: large cells for rapid conduction

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32
Q

What are intercalated disks in cardiac muscle

A

specialised regions connecting individual cardiomyocytes

contains numerous gap junctions for APs to spread

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33
Q

Describe excitation contraction coupling in cardiomyocytes

A

Same as skeletal muscle

depolarisation opens voltage-gated calcium channels

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34
Q

What effects does calcium have in cardiac muscle

A

Ca2+ induced Ca2+ release by binding to RyR on SR
Initiate contraction binding to troponin
Further depolarisation

35
Q

Describe the structure of smooth muscle

A

in walls of hollow organs e.g. blood vessels and the GI tract
doesn’t have the regular arrangement of actin and myosin

36
Q

Explain the process of excitation contraction coupling in smooth muscle

A
  1. Depolarisation activates voltage gated Ca2+ channels
  2. Ca2+-CaM complex activates myosin light chain kinase
  3. MLCK phosphorylates myosin light chains
  4. Cross -bridges form with actin filaments -> contraction
37
Q

Why do cells communicate

A

process information, self preservation, voluntary movement, homeostasis

38
Q

Describe endocrine signalling and give an example

A

hormone travels via blood vessels to act on a distant target cell
Glucagon is secreted from the pancreas travels in the blood stimulates glycogenolysis and gluconeogenesis in the liver
others: insulin acting on liver, muscle cells and adipose tissues
adrenaline from glands acting on the trachea

39
Q

Describe paracrine signalling and give an example

A

Hormone acts on an adjacent cell
insulin released by beta cells inhibits glucagon secretion in adjacent alpha cells (+endocrine)
others: NO in endothelial cells in blood vessels
Osteoclast activating factor produced by adjacent osteoblasts

40
Q

Describe aubocrine signalling and give an example

A

Signalling molecule acts on the same cell
Activated TCR initiates a cascade of reactions in the cell, expressing interleukin 2 receptor. Secretion of IL-2 also binds to IL-2 receptor on the same cell
other: acetycholine
growth factors e.g. TGFB form tumour cells

41
Q

Describe signalling by membrane attached proteins and give an example

A

plasma membrane proteins on adjacent cells interacting
APCs presenting parts of the pathogen through MHC I
circulating T cells engage with MHC molecules through TCR
others: HIV GP120 glycoprotein
bacterial cell wall components

42
Q

Describe ionotropic receptors

A

Ligand binding opens an ion permeable pore leading to a signal transduction event

  1. ligand binds to receptor
  2. change in conformation of channel
  3. pore opens
  4. movement of ions according to gradient
43
Q

Give an example of ionotropic receptor action

A

nicotinic acetylcholine
Acetylcholine causing muscle contraction in skeletal muscle

GABAa (gamma amino butyric acid) causes a decreases in neuronal excitability in neurones

44
Q

Describe G-protein coupled receptors

A

Ligand binds to activate an intracellular G-protein
1. 7-TM receptor + heterotrimeric G-protein are inactive
2. Ligand binds changing conformation of the receptor
3. G-protein binds to the receptor
4. GDP exchanged for GTP
5. G-protein dissociates into 2 active units (alpha & gamma+beta)
6. units bind
7. GTPase dephosphorylates GTP to GDP
8. alpha subunit dissociates and becomes active
Receptor is active as long as the ligand is bound

45
Q

What are the 3 types of G-protein coupled receptors and what are their functions (+examples)

A

Gs - stimulates adenyl cyclase
ATP -> cyclic AMP -> Activated protein kinase A
e.g. beta adrenergic receptor to increase heart rate

Gi - inhibits adenylyl cyclase
reduces PKA levels
e.g. Muscarinic receptor to decrease heart rate

Gq - stimulates phospholipase C
PIP2 -> IP3 + DAG -> calcium release + PKA activation
e.g. angiotensin receptor to vasoconstrict

46
Q

Describe enzyme-linked receptors

A

Ligand binds to cause clustering of receptors

  1. ligand binds
  2. receptors cluster to activate enzymes
  3. enzymes phosphorylate the receptor
  4. signal proteins bind to cytoplasmic domain
  5. recruit other signal proteins to generate the signal
47
Q

Give an example of enzyme-linked receptors

A 
insulin receptor (CD220)
insulin causes glucose uptake

ErbB
Epidermal growth factor causing cell growth and proliferation

Guanylyl-cyclase
Atrial natriuretic peptide causes vasodilation to decrease blood pressure

Ser/Thr-kinase
Transforming growth factor beta causes apoptosis

48
Q

Describe type 1 signal transduction

A

cytoplasmic
association with chaperone molecules (heat shock proteins)
1. hormone binds to receptor
2. HSP dissociates
3. 2 hormone-bound receptors -> homodimer
4. translocates -> nucleus + binds to DNA

49
Q

Describe type 2 signal transduction

A

nuclear

  1. hormone ligand binds
  2. transcriptional regulation
50
Q

Give an example of signal transduction

A

glucocorticoid
cortisol/corticosterone causes a decrease in immune response and an increase in gluconeogenesis

Thyroid hormone
T4 and T3 cause growth and development

51
Q

Give 3 common skin diseases

A

acne
eczema
psoriasis

52
Q

Give some functions of skin

A

Protection against injury and pathogenic organisms
Waterproofing and fluid conservation
Thermoregulation (~36.8) through blood flow (sympathetic) and sweating
Protection against radiation, absorption of ultra violet radiation and vitamin D production
Surface for grip
Sensory organ
Cosmetic

53
Q

What are the 4 layers of the epidermis

A 
Keratinocytes
Stratum Corneum
Stratum granulosum
Stratum spinosum
Stratum basale
54
Q

Outline the very basic structure of the skin

A

Epidermis
Basement membrane
Dermis

55
Q

Give some other components of the skin

A

desmosome
sweat glands
hair/ hair follicle
sebaceous glands

56
Q

Describe the Stratum corneum

A

corneocytes (flat with no nuclei)
Protective
Filagrin gene mutation leads to eczema

57
Q

Describe Stratum Spinosum

A

prickle/spinous cells that produce keratin

Desmosomes

58
Q

Describe Stratum Basale

A

Basal cells that connect to eh basement membrane

Keratinocytes found here

59
Q

Give some other components of the epidermis

A 
Melanocytes (production of melanin)
Langerhans cells (antigen presenting)
Merkel cels (sensation)
60
Q

Describe the basement membrane in the skin

A

Highly specialised region where epidermis meets dermis
via hemidesmosomes, anchoring plaques and proteins
Blisters are common e.g. epidermolysis bullosa

61
Q

Describe the structure of the basement membrane in skin

A

hemidesmosomes
tonofilaments
demo-epidermal junctions
anchoring fibrils

62
Q

Describe the dermis

A

supportive connective tissues - collagen, elastin, GAG
Thickness varies between 0.1mm and 3mm
contains fibroblasts that synthesises collagen, elastin and GAG
Dendritic cells found here

63
Q

Describe the subcutaneous layer

A

Connective tissue and fat

64
Q

Describe the pilo-sebaceous unit of the skin

A

Follicle
Hair shaft
Sebaceous gland
Pilo-erecti muscle

65
Q

What are the two types of sweat glands found in skin

A

Apocrine - only located in the axillary and groins that produce discus sweat - subject to bacteria and therefore produce odour
Eccrine

66
Q

What are the components of the dermo-epidermal junction

A 
Lamina lucida
Lamina densa
Anchoring fibrils
Hemidesmosomes 
Anchoring filaments
67
Q

Explain the role of melanocytes and their development

A

Dendritic cells in Stratum Basale
Produces melanin pigment in the melanosome, which is then packed into granules that are transferred to adjacent keratinocytes via phagocytosis
Granules form a protective cap around the nuclei to protect DNA from UV (which stimulates melanin production)
Variation in pigmentation is from no. and size of melanosomes

68
Q

What are the 3 types of hair

A

Lanugo
Vellus
Terminal

69
Q

Describe Lanugo hair

A

Fine whispy and long hair
Found in the foetus at 20 weeks and in anorexic people
Shed before birth

70
Q

Describe vellus hair

A

Short, fine, light hairs that cover the body

71
Q

Describe terminal hair

A

Long, thick, dark hair
Scalp, eyebrows, eyelashes, pubic, axillary
Starts at vellus and androgens make it terminal

72
Q

Describe the hair follicle

A 
Made up of pilo-sebaceous units
Hair follicle
Hair shaft
Erector pili muscle
Sebaceous gland
Hair bulb- blood from the dermal papilla
73
Q

What are the 3 stages in hair growth

A

anagen
catagen
telogen

74
Q

Describe anagen in hair growth

A

growth phase (85% cells)
Energy intensive + highly vascularised
Most metabolically active
Rate depends on body site

75
Q

Describe catagen in hair growth

A

Cell devision slows and stops
End of shaft keratinises to form a club shape
Dermal papillae and club moves to the base of muscle insertion

76
Q

Describe telogen in hair growth

A

Hair is shed actively
Next anagen phase begins
Club hair takes 4-6 weeks

77
Q

What is synchronicity in hair growth

A

when a baby is born, all the hair growth cycles are in synchronicity

78
Q

How does age affect hair growth

A

Telogen effluvium - the thinning of hair due to early entry to telogen
Due to emotional and physiological stress or hyperthyroidism, sepsis and anaemia

79
Q

How do sex hormones affect hair growth

A

testosterone on the follicles
There is a surge during puberty which grows terminal hair
Pubic and axillary, then beard and chest, then nose and ear hair
Androgen sensitivity - balding pattern

80
Q

What are nails made of

A

Hard hair keratin

81
Q

Describe the growth of nails

A

Nails grow from the Germinal matrix

82
Q

Describe the structure of the nail

A

Distal end is the lunula/germinal matrix (critical to growth) - white moon
eponychium - skin cover
hyponychium
onychodermal band - overhang of nail

83
Q

Describe the growth of nails

A

Fingernails - 3mm a month
Toenails - 1mm a month
Due to adhesion and nail folds, the nail grows out and not up
Nail surface is produced by the proximal nailbed

MCD (13 decks)

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