Tissues 2 Flashcards
(83 cards)
1
Q
Name the 4 cerebral hemispheres and locate them
A
Frontal, Temporal, Parietal, Occipital
2
Q
Name the convoluted ridges of the brain
A
Gyri are the ridges
Sulci are the grooves
3
Q
What is the brainstem composed of
A
Midbrain, pons and medulla
4
Q
What is the function of the brainstem
A
Target source of all cranial nerves with numerous functions
5
Q
Locate the cerebellum and give its function
A
Hindbrain attached to the brainstem
Motor coordination, balance and posture
6
Q
What is the function of the spinal cord
A
Conduit for neural transmission
Co-ordinates some reflex actions
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)
8
Q
Give 3 examples of multipolar neurones
A
pyramidal
Purkinje
Golgi
9
Q
Describe astrocytes
A
Most abundant in the CNS
Able to proliferate
Neuroglial
10
Q
What are the functions of astrocytes
A
Structure
Cell repair
Immune cells
Neurotransmitter release and re-uptake
11
Q
Describe an oligodendrocyte
A
Variable morphology and function
Numerous projections that form internodes of myelin
Myelinates axons
12
Q
What is the function of Schwann cells
A
Produces myelin for peripheral nerves
13
Q
What is the function of Microglial cells
A
Immune functions in the CNS
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
15
Q
Explain the process of intracellular communication through a synapse
A
- AP propagates along the axon
- AP opens voltage-gated channels at the presynaptic terminal
- influx causes vesicle exocytosis
- NT binds to receptors on the post synaptic membrane to activate them for post-synaptic activity
- NT dissociates from the receptor and is metabolised by enzymes in the synaptic cleft or is recycled by transporter proteins
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
17
Q
What are the 4 major physiological ions for RMP
A
potassium, sodium, chloride, calcium
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
19
Q
Describe the process of action potential generation in neurones
A
- sodium channels open to induce sodium influx
- depolarisation
- potassium channels open at a slower rate
- depolarisation of the cell
- sodium potassium ATPase restores the gradient
20
Q
What is the function of myelin
A
Prevents AP propagation
21
Q
What is the function of nodes of Ranvier
A
Provides small gaps that the AP can jump across for faster transmission
22
Q
What is the function of skeletal muscle
A
Produces movement relative to the external environment
23
Q
What do antagonist muscle pairs consist of
A
Flexor (bicep)
Extensor (tricep)
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
25
What is isometric contraction
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
26
Describe the ultrastructure of skeletal muscle myofibres
```
Consists of myofibres (bundles)
large and cyclindrical
multinucleated
packed with myofibrils
sarcoplasmic reticulum - calcium stores
T-tubules
```
27
Describe the structure of a sarcomere
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
28
Explain sliding filament theory
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
29
Explain the process of excitation in skeletal muscle
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+
30
What are the pacemaker cells of the heart
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
31
What are the conducting fibres of the heart
Bundle of His: fast conducting cells adjoining AV node and Purkinje fibres
Purkinje fibres: large cells for rapid conduction
32
What are intercalated disks in cardiac muscle
specialised regions connecting individual cardiomyocytes
| contains numerous gap junctions for APs to spread
33
Describe excitation contraction coupling in cardiomyocytes
Same as skeletal muscle
| depolarisation opens voltage-gated calcium channels
34
What effects does calcium have in cardiac muscle
Ca2+ induced Ca2+ release by binding to RyR on SR
Initiate contraction binding to troponin
Further depolarisation
35
Describe the structure of smooth muscle
in walls of hollow organs e.g. blood vessels and the GI tract
doesn't have the regular arrangement of actin and myosin
36
Explain the process of excitation contraction coupling in smooth muscle
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
Why do cells communicate
process information, self preservation, voluntary movement, homeostasis
38
Describe endocrine signalling and give an example
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
Describe paracrine signalling and give an example
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
Describe aubocrine signalling and give an example
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
Describe signalling by membrane attached proteins and give an example
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
Describe ionotropic receptors
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
Give an example of ionotropic receptor action
nicotinic acetylcholine
Acetylcholine causing muscle contraction in skeletal muscle
GABAa (gamma amino butyric acid) causes a decreases in neuronal excitability in neurones
44
Describe G-protein coupled receptors
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
What are the 3 types of G-protein coupled receptors and what are their functions (+examples)
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
Describe enzyme-linked receptors
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
Give an example of enzyme-linked receptors
```
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
Describe type 1 signal transduction
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
Describe type 2 signal transduction
nuclear
1. hormone ligand binds
2. transcriptional regulation
50
Give an example of signal transduction
glucocorticoid
cortisol/corticosterone causes a decrease in immune response and an increase in gluconeogenesis
Thyroid hormone
T4 and T3 cause growth and development
51
Give 3 common skin diseases
acne
eczema
psoriasis
52
Give some functions of skin
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
What are the 4 layers of the epidermis
```
Keratinocytes
Stratum Corneum
Stratum granulosum
Stratum spinosum
Stratum basale
```
54
Outline the very basic structure of the skin
Epidermis
Basement membrane
Dermis
55
Give some other components of the skin
desmosome
sweat glands
hair/ hair follicle
sebaceous glands
56
Describe the Stratum corneum
corneocytes (flat with no nuclei)
Protective
Filagrin gene mutation leads to eczema
57
Describe Stratum Spinosum
prickle/spinous cells that produce keratin
| Desmosomes
58
Describe Stratum Basale
Basal cells that connect to eh basement membrane
| Keratinocytes found here
59
Give some other components of the epidermis
```
Melanocytes (production of melanin)
Langerhans cells (antigen presenting)
Merkel cels (sensation)
```
60
Describe the basement membrane in the skin
Highly specialised region where epidermis meets dermis
via hemidesmosomes, anchoring plaques and proteins
Blisters are common e.g. epidermolysis bullosa
61
Describe the structure of the basement membrane in skin
hemidesmosomes
tonofilaments
demo-epidermal junctions
anchoring fibrils
62
Describe the dermis
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
Describe the subcutaneous layer
Connective tissue and fat
64
Describe the pilo-sebaceous unit of the skin
Follicle
Hair shaft
Sebaceous gland
Pilo-erecti muscle
65
What are the two types of sweat glands found in skin
Apocrine - only located in the axillary and groins that produce discus sweat - subject to bacteria and therefore produce odour
Eccrine
66
What are the components of the dermo-epidermal junction
```
Lamina lucida
Lamina densa
Anchoring fibrils
Hemidesmosomes
Anchoring filaments
```
67
Explain the role of melanocytes and their development
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
What are the 3 types of hair
Lanugo
Vellus
Terminal
69
Describe Lanugo hair
Fine whispy and long hair
Found in the foetus at 20 weeks and in anorexic people
Shed before birth
70
Describe vellus hair
Short, fine, light hairs that cover the body
71
Describe terminal hair
Long, thick, dark hair
Scalp, eyebrows, eyelashes, pubic, axillary
Starts at vellus and androgens make it terminal
72
Describe the hair follicle
```
Made up of pilo-sebaceous units
Hair follicle
Hair shaft
Erector pili muscle
Sebaceous gland
Hair bulb- blood from the dermal papilla
```
73
What are the 3 stages in hair growth
anagen
catagen
telogen
74
Describe anagen in hair growth
growth phase (85% cells)
Energy intensive + highly vascularised
Most metabolically active
Rate depends on body site
75
Describe catagen in hair growth
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
Describe telogen in hair growth
Hair is shed actively
Next anagen phase begins
Club hair takes 4-6 weeks
77
What is synchronicity in hair growth
when a baby is born, all the hair growth cycles are in synchronicity
78
How does age affect hair growth
Telogen effluvium - the thinning of hair due to early entry to telogen
Due to emotional and physiological stress or hyperthyroidism, sepsis and anaemia
79
How do sex hormones affect hair growth
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
What are nails made of
Hard hair keratin
81
Describe the growth of nails
Nails grow from the Germinal matrix
82
Describe the structure of the nail
Distal end is the lunula/germinal matrix (critical to growth) - white moon
eponychium - skin cover
hyponychium
onychodermal band - overhang of nail
83
Describe the growth of nails
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
