WEEK 7 Flashcards

Question

What does each cerebral hemisphere consist of? Describe how it receives sensory impulses & dispatches motor impulses.

Answer 1

Cerebral cortex, cerebral white matter and nuclei Receives sensory impulses from, and dispatches motor impulses to, the opposite side of the body. The body is represented in an upside down fashion in the sensory and motor cortices

Answer 2

a. Motor areas: primary motor cortex and premotor of FRONTAL lobe b. Sensory areas: primary somatosensory cortex and somatosensory association cortex of PARIETAL lobe c. Visual areas in the OCCIPITAL lobe d. Auditory and Olfactory areas in the TEMPORAL lobe

Answer 3

In most people, the left hemisphere is dominant (i.e., specialized for language and mathematical skills), the right hemisphere is specialized for visual-spatial skills and creativity

Answer 4

Thalamus hypothalamus encloses the 3rd ventricle

Answer 5

a. sensory impulses ascending to the sensory cortex b. inputs from subcortical nuclei and the cerebellum travelling to the cerebral motor cortex HYPOTHALAMUS = an important autonomic nervous system (ANS) control centre. It maintains water balance and regulates thirst, eating behaviour, gastrointestinal activity, body temperature, and the activity of the anterior pituitary gland.

Answer 6

MIDBRAIN contains Superior & inferior colliculi (visual & auditory reflex centres) • Red nucleus (subcortical motor centre) • Pyramidal tracts (on ventral surface of cerebral peduncles) • Substantia nigra • Motor nuclei of CN III, IV • Surrounds cerebral aqueduct The mid-brain surrounds the cerebral aqueduct. PONS is mainly a conduction area. Its nuclei contribute to regulation of respiration and cranial nerves V-VII. MEDULLA OBLONGATA has pyramids on its ventral surface (descending corticospinal tracts). The fibres cross-over at the decussation of the pyramids before entering the spinal cord. Important nuclei in the medulla oblongata regulate respiratory rhythm, heart rate, and blood pressure and serve cranial nerves VIII-XII. The cough, sneezing, swallowing, and vomiting centres are in the medulla.

Answer 7

(i) consists of two hemispheres marked by convolutions. (ii) connected to the brain stem by sup, middle, and inf cerebellar peduncles. (iii) processes and interprets impulses from the motor cortex and sensory pathways and coordinates motor activity so that smooth, well- timed movements can occur. It is also important in balance.

Answer 8

The spinal cord is a two-way impulse conduction pathway and reflex centre. It resides within the vertebral column and extends from foramen magnum to end of L1 vertebra. It is protected by meninges and CSF.

Answer 9

In cervical and lumbar regions - where spinal nerves serving the limbs arise

Answer 10

Dorsal rami serve the muscles and skin of posterior body trunk Ventral rami within the cervical and lumbar spinal cord form plexuses that serve the limbs. T1-T12 ventral rami give rise to intercostal nerves that serve the thorax wall and abdominal surface.

Answer 11

The central grey matter of the cord is H shaped. Anterior horns mainly contain somatic motor neurons. Lateral horns contain visceral (autonomic) motor neurons. Axons of neurons of the lateral and anterior horns emerge from the cord via the ventral roots. Posterior horns contain interneurons. Axons of sensory neurons (with cell bodies located in the dorsal root ganglion – DRG) enter the posterior aspect of the cord and form dorsal roots. Each side of the white matter of the cord has posterior, lateral, and anterior columns, and each column contains ascending and descending tracts. All tracts are paired and most decussate.

Answer 12

Lipids have low solubility in water They include phospholipids, fats, sterols and some vitamins Sources of energy, forms membranes, participates in cell signalling

Answer 13

bile acids steroid hormones vitamins cell membranes

Answer 14

Gaucher's (most common) Fabry disease Defects in enzymes which metabolise lipids leading to lipid accumulation Largely affect neurological system, liver, spleen and bone marrow Failure to thrive

Answer 15

it has a hydrophilic head which is attracted to water and a hydrophobic tail which dislikes water and looks to aggregate with other hydrophobic molecules Hydrophilic heads face water and hydrophobic tails are shielded from the water and lie next to each other

Answer 16

1. compartmentalisation 2. organelles as well as plasma membrane 3. highly selective barriers 4. have sensors to respond to internal and external conditions

Answer 17

The phospholipid bilayer is a fluid matrix The bilayer is a two-dimensional solvent The lipids and proteins can undergo rotational and lateral movement Peripheral proteins (extrinsic proteins) Integral proteins (intrinsic proteins

Answer 18

1. PHOSPHOLIPIDS - choline, ethanolamine, serin, inositol 2. GLYCOLIPIDS - have sphingosine core

Answer 19

Membrane synthesis occurs in the ER. The new membrane is then transported to other parts of the cell. This occurs through a series of vesicle budding and fusion. Bits of the membrane pinch off from the ER to form vesicles and then fuse with other membranes

Answer 20

a new phospholipid is synthesised by enzymes at the ER facing the cytosol using fatty acids that are available in the cytosol. They release the new phospholipid into the outer leaflet of the ER bilayer Lipids are then transferred to the other side by flippases Some flippases are selective for particular phospholipids so different types may be concentrated in each monolayer

Answer 21

(i) Delivery of lipids (and membrane proteins) to cell membrane. It allows movement of other molecules out of cell (ii) Movement of material into cells via membrane bound vesicles. It is especially important in the immune response. May be mediated by specific receptors

Answer 22

1. TRANSMEMBRANE: they tend to have a number of hydrophobic amino acid residues which “shun” the aqueous environment on the inside and outside. Some proteins can have a range of these domains which come together. This can form a channel or pore where the groups are selective for a particular cargo. If the groups on the inside are hydrophilic this can be the structure of an aqua pore. 2. MEMBRANE ASSOCIATED: usually contain domains that selectively bind to phospholipids. Compartment-specific association E.g. pleckstrin homology domains (PH) Approx. 100 amino acid region found in many proteins that bind to certain types of phospholipid Removal of PH domain alters a protein’s membrane binding properties (e.g. Phospholipase C-n2) 3. LIPID-LINKED GPI (glycosylphosphatidylinositol) anchors 4. PROTEIN-ATTACHED especially important in signal transduction

Answer 23

Phospholipids not only make up the lipid bilayer, they participate in cell signalling mechanisms by giving rise to intracellular second messengers. They also serve as precursors for the compounds that are released from cells and act on other cell types, called eicosanoids - inflammatory mediators. 1. Synthesis of signal 2. Release of the signalling molecule by the signalling cell: exocytosis, diffusion, cell-cell contact. 3. Transport of the signal to the target cell 4. Detection of the signal by a specific receptor protein 5. A change in cellular metabolism, function or development triggered by the receptor-signal complex 6. Removal of the signal or desensitisation

Answer 24

LONG RANGE - - ENDOCRINE = hormone released by endocrine cell and carried in bloodstream to distal target cells. E.g. FSH released from pituitary acts upon ovary - NEUROTRANSMISSION e.g. Breathing – the phrenic and thoracic nerves send impulses from the brain to the diaphragm SHORT RANGE- - PARACRINE = signalling molecules only affect target cells in clsoe proximity to secreting cells e.g. somatostatin release by pancreas cells acts locally - AUTOCRINE = cells respond to substances that they themselves release e.g. Some neurotransmitters and growth factors bind to the cells that release them. - MEMBRANE BOUND PROTEINS = A signalling cell expresses specific molecules on the cell surface and an adjacent target cell has receptors for these and binds acting as a trigger for a cellular process e.g. signalling T cells in the immune system

Answer 25

Insulin acts on cells far away (endocrine) which regulate uptake of glucose Acts in an autocrine manner after a certain amount of insulin is secreted it binds to receptors on the cell to stop insulin secretion. It also acts in an paracrine way binding to alpha cells to prevent secretion of glucagon.

Answer 26

Most things that affect cell activity or function do not actuallyenter cells. Instead, they act on membrane-bound receptors that control the production of intracellular chemicals (second messengers), these mediate cell activity.

Answer 27

1. LIGAND GATED ION CHANNELS (ionotropic) - the receptor is also a channel and when the signalling molecule binds to receptor it allows ions to flow into the cell either depolarising or polarising the cell and causing a cellular effect. 2. G-PROTEIN COUPLED RECEPTORS (metabotropic) - usually have 7 transmembrane domains and exist on the plasma membrane surface. When they bind to the signalling molecule a G-protein that is normally bound to the receptor is disengaged evoking a cellular effect. Common pathways caused by liberation of G-proteins are opening of ion channels, bind and activate enzymes to produce second messenger to release calcium or activate kinases. This is a fast type of signalling. 3. KINASE-LINKED RECEPTORS - once the signalling molecule is recognised they phosphorylate a protein which often happens as part of a cascade, and eventually a transcription factor is switched on causing a protein to be synthesised. This is a slow form of signalling as it requires the synthesis of a new protein. 4. NUCLEAR RECEPTORS - Lipid Soluble Molecules can pass through the plasma membrane and be recognised by intracellular receptors e.g. steroid hormones. The receptor-signal complex often switches on a family of transcription factors causing a slower form of signalling

Answer 28

Phosphatidylinositol 4,5-bisphosphate (PIP2) is a phospholipid found in the lipid bilayer. The enzyme phospholipase C (PLC), liberates two signalling molecules from PIP2; inositol 1,4,5 trisphosphate (IP3) and diacyglycerol (DAG). PLC can be activated down stream from uncoupled G-protein receptors, this enzyme recognises PIP2 and cleaves it into IP3 and DAG. IP3 can bind to receptors such as ligand activated channels that reside in the endoplasmic reticulum allowing Ca2+ to move into the cytosol. At the same time DAG is recognised by protein kinase C (PKC) and this activates the kinase. Through the activation of the kinase and the change in the Ca2+ concentrations in the cytosol, cellular responses are evoked. Calcium can activate cellular pathways by binding to groups of proteins strongly at high concentration, and this calcium switches on these molecules. These proteins are responsible for exocytosis, contraction, metabolism and gene transcription. So for a short period of time these responses will be evoked but once the calcium levels fall the response ends.

Answer 29

1. “Conventional” require DAG and Ca2+ 2. “Novel” require DAG but not Ca2+ 3. “Atypical” doesn’t require DAG or Ca2+ 1. tumour suppressor p53 - prevents tumour formation through inducing apoptosis 2. CaV 1.2 calcium channel - heart muscle contraction 3. IKK𝛂 - B cell activation (immune function)

Answer 30

prostaglandins, thromboxanes and leukotrienes Arachidonic acid

Answer 31

The initial and rate-limiting step in eicosanoid synthesis is the liberation of arachidonic acid by phospholipase A2 (PLA2) - PLA2 is acitvated by a variety of receptor-mediated signals. 1. Cyclo-oxygenase and peroxidase to give thromboxanes and prostaglandins 2. Lipoxygenases to give leukotrienes

Answer 32

1. Vasocontriction/dilation 2. Inhibit/promote platelet aggregation 3. Inflammatory response and thermoregulatory (fever) and pain

Answer 33

(i) Platelets (ii) stimulate platelet aggregation vasocontrictor

Answer 34

(i) WBC's (ii) immune response, they are heavily implicated in asthma and allergy

Answer 35

A bi-product of arachidonic acid liberation Synthesised in leukocytes (and also by injured tissue e.g. endothelial cells) 1. Platelet aggregation 2. Vasoconstriction 3. Inflammations 4. Immune response (also anaphylaxis)

Answer 36

Through the nuclear pore complex = a basket on the inside of the nucleus and the cytosolic fibrils on the cytoplasmic side. This process is tightly controlled, and is energy dependent which requires the reorganisation of the proteins at the core of the nuclear pore. Some small molecules can diffuse across the nuclear envelope but other molecules passage are controlled by the nuclear pores. After mRNA passes through the nuclear pore the cap-binding protein is exchanged for an initiation factor which binds to 5’ cap.

Answer 37

The starting point is defined by the initiation codon (**AUG**). The ending point is defined by the stop codon (**UGA**) which defines the end of open reading frame

Answer 38

1. INITIATION The 5’ cap structure of the mRNA is recognised by the cap-binding protein complex which then recruits ribosomes. The ribosomes ‘scan’ through the 5’non-coding region until the initiation codon is found. Requires initiation factors 2. ELONGATION the (correct) charged tRNAs then bind and a peptide bond is made between the amino acids. Once the peptide bond is formed, the ribosome moves along the mRNA one codon. The deacylated tRNA exits the complex and a new, charged, tRNA binds (specified by the next codon of the mRNA)........etc., etc., until 3. TERMINATION the termination codon is encountered at the end of the open reading frame and the bond between the protein and the (last) tRNA is broken to release the finished protein. The whole complex disassociates. Requires termination factors

Answer 39

1. DELETION or INSERTION (nonsense or frameshift) - the reading frame is shifted as bases are either inserted or deleted 2. SUBSTITUTION (missence or point shift) 3. SILENT MUTATION TH**E** BIG RED ANT ATE ONE FAT BUG TH**A** BIG RED ANT ATE ONE FAT BUG _NOTE_: a POLYMORPHISM is not a mutation, it is a minor change in DNA sequences that is present in \>1% of the population

Answer 40

1. Translocation to relevant part of cell 2. Protein folding 3. Post-translational modification

Answer 41

Translocation within the cell can happen co-translationally. As a protein is being made the amino acids encoded in the protein form a signal sequence that is recognised by other proteins and direct it to the endoplasmic reticulum membrane. There are channels in the ER membrane that recognise the protein and allow the protein and the ribosome with it, as it is still being synthesised, into the ER hence rough ER. The signal sequences can code for movement to destinations such as the nucleus, ER, mitochondrion etc.

Answer 42

Signals can also dictate post-translation modifications such as **glycosylation**. N-linked glycosylation tends to start in the ER and occur in the Golgi. Too much as well as too little modification can be harmful, **tau-hyperphosphorylation** is associated with neurofibrillar tangles in dementia.

Answer 43

Damage to tissues Damage to blood vessels Presence of a foreign body (sutures) Reduced efficacy of inflammatory response

Answer 44

1. Acquisition during surgery 2. Acquisition post operatively 3. Endogenously (pts own microflora) 4. Exogenously (other pt or staff)

Answer 45

1. Dehiscence - reopening of a closed wound (can lead to evisceration) 2. Abscess development 3. Localised spread of infection 4. Systemic spread of infection

Answer 46

1. Type of surgical wound(clean/dirtyetc.) 2. Pre-, intra- and post operative care 3. Surgical team 4. Age and general health of pt 5. Extent of tissue injury 6. Infection prevention procedures 7. Presence of prosthesis or foreign body 8. Presence or absence of drain 9. Duration of surgery 10. Place in operation list

Answer 47

``` **Clean (class I)** – Elective surgery ``` – No acute inflammation – Do not involve R, GI or GU tracts **Clean / contaminated (class II)** – Urgent/emergencycase – Clean wounds with higher risk of infection – Uncomplicated R, GI or GU tract surgery ``` **Contaminated (class III)** – Outside object comes into contact with wound – Large amounts of spillage from GI tract into wound ``` **Dirty class (IV)** – Purulent inflammation – Foreign object lodged in wound – Traumatic or infected wounds

Answer 48

SKIN Staphylocossus aureus Streptococci spp Enterococci spp BOWEL E.coli Bacteroides fragilis Clostridium perfringens Enterococci Anaerobic cocci

Answer 49

Preoperative showering Do not remove hair Give antibiotic prophylaxis before: – Clean surgery (prosthesis or implant only) – Clean-contaminated surgery – Contaminated surgery Do **not** routinely use nasal decontamination Do **not** routinely use mechanical bowel preparation unless harvesting gut

Answer 50

Shaving inflicts microtrauma and increases susceptibility to colonization by bacteria

Answer 51

(i) gauze non-adhesive fabrics (ii) hydrocolloids polyurethane films

Answer 52

1. Keep pre-operative length of stay in hospital to a minimum 2. Elective surgery should be postponed if evidence of infection pre-op 3. Keep length of surgery as short as possible 4. Maintain good operative technique 5. Debridement of dead and necrotic skin - to bleeding tissue 6. Ensure adequate vascularization - never close a dusky wound

Answer 53

1. Skill of individual surgeon 2. Quality of aseptic technique 3. Adequacy of protective clothing 4. Wearing of gloves 5. Carriage of S. aureus

Answer 54

1. Always wash hands before procedure 2. Wear gloves when handling catheter 3. Use single use antiseptic wipe 4. Cover insertion site with dressing

Answer 55

Diabetes mellitus Rhematoid arthritis Malnutrition Obesity

Answer 56

Blood culture Collection of pus by needle aspiration Bone biopsy Raised ESR and CRP CLINICAL EXAMINATION Radiological imaging

Answer 57

Staphylococcus aureus Staphylococcus epidermidis Streptococcus pyogenes Gram negative bacilli Anaerobes

Answer 58

Direct examination culture sereology molecular

Answer 59

(i) Rapid Simple to perform Cheap Not very sensitive OR specific Requires considerable expertise (ii) More sensitive than smear Allows susceptibility testing Allows rapid presumptive diagnosis Allows detailed identification Rendered negative by antibiotics (iii) Rapid identification of bacteria Does not provide susceptibilities Delayed by slow growth Of no value if antibiotics render cultures negative

Answer 60

1. Identify the infecting organism **DIAGNOSTIC ADVICE** 2. Susceptibility testing **TREATMENT ADVICE** 3. Identify clustered organisms over-represented in the community **INFECTION CONTROL**

Answer 61

Detect high IgG concentration Detect rising of falling titres Detect IgM/IgA Measure avidity of binding Detect antigen Examples = agglutination, precipitation, complement fixation, virus neutralisation etc

Answer 62

1. DNA hybridisation 2. Nucleic acid amplification testing 1. PCR 2. LCR (ligase chain reaction) 3. Automated DNA amplification 4. Real time PCR

Answer 63

(i) The ability of a test to detect all of the _true positives_. It is equal to the number of positives obtained divided by the total number of positives (ii) Ability to identify the number of _true negatives_. It is equal to the number of negatives obtained divided by the number of true negatives

Answer 64

Atoms Simple molecules Macromolecules Basic biostructures Subcellular organelles Cells Tissues Organs Organ Systems

Answer 65

(i) The basic and structural functional unit (ii) an aggregate of a specialised cell type with a particular function e.g. muscles, epithelial, nervous (iii) Sspecialised tissue organised by connective tissue and served by nerves, blood vessels and more depending on function e.g. kidney, liver, pancreas (iv) A group if integrated organs that collectively perform a function .e.g. cardiovascular, urinary.

Answer 66

Fundamentally all cells remain viable using common basic cellular pathways controlled by housekeeping genes. On top of this differentiated cells express genes that allow the cell to perform a special function(s). E.g. muscle cells generate force and produce motion nerve cells initiate and propogate electrical signals epithelial cells form boundaries between different compartments endothelium defines vessels e.g. blood vessels connective tissue cells connect, anchor and support structures of the body

Answer 67

the functional internal environment

Answer 68

Bathes the cells and tissues and is the internal environment of the body

Answer 69

1. Primarily operate through a negative feedback mechanism 2. Stability is achieved through balancing the inputs and outputs (irrespective of the absolute magnitude of change) 3. Unable to maintain complete constancy of the internal environment (range of normal values) 4. Unable to maintain every system constant (hierarchy of importance) 5. The set point of some control systems can be reset

Answer 70

Physiological control systems maintain the internal environment in a relatively stable state. Homeostatic balance is the result of the regulated and integrated activity of tissues and organ systems. Homeostatic regulation involves mechanisms that feedback, FEEDBACK can only occur in a system where the outputs are routed back in someway as inputs.

Answer 71

(i) the feedback action reduces the effect of the circuit/pathway (most common in maintaining homeostasis) **PROMOTES STABILITY** (ii) the system ANTICIPATES the need for change **ANTICIPATES CHANGE** (iii) the feedback action produces a positive or heightened effect **PROMOTES CHANGE IN ONE DIRECTION, INSTABILITY**

Answer 72

The effectiveness of a negative feedback system

Answer 73

1. What is the **variable** that is being maintained in the face of changing conditions? 2. What are the **receptors** that detect change? 3. Where is the **integrating** **centre** and what are the afferent and efferent pathways? 4. What are the **effectors** and how do they alter their activities to maintain the set point?

Answer 74

THERMOREGULATION - Body temperature controlled at ~37oC Ambient temp can be ;50oC ; +50oC Main sensor = skin Controller = hypothalamus •Effectors = skin (sweating, hairs trap heat) and muscle. BARORECEPTORS - see diagram GLUCOSE - Fasting blood sugar tightly maintained at 3.5 to 8 mmolL-1 Glucose sensor = specialised pancreatic cells that receive blood via portal circulation Controller = autonomic nervous system Effectors = α Pancreatic cells in islets of Langerhans (secrete glucagon for glucose release) β Pancrea0c cells in islets of Langerhans (secrete insulin for glucose uptake by cells)

WEEK 7 Flashcards

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