11 application case & what if questions

A student falls and fractures the scaphoid. Which region is injured, and is the bone axial or appendicular?

Wrist (carpal); appendicular. The scaphoid is a carpal bone, not part of the arm

A knife wound is in the area of the ascending colon. Which abdominal region?

Right lumbar. The ascending colon sits in the right middle row of the 9-region grid

A patient has jaundice (yellow skin) and liver pain. Which abdominal region would you palpate?

Right hypochondriac. The liver sits below the right ribs

A patient stands in anatomical position and turns the left palm to face backward. What movement?

Pronation. In anatomical position the palm faces forward; turning it posteriorly is pronation

A physiotherapist says "invert your foot." Which way does the sole turn?

Toward the midline. Inversion = sole tilts medially; eversion = away

An MRI shows the brain cut into top and bottom halves. Which plane?

Transverse (axial)

An MRI shows a cut down the exact midline, separating left and right halves equally. Which plane?

Midsagittal (median)

Describe a mid-shaft ulna fracture relative to the radius

Medial. The ulna is on the pinky (medial) side of the forearm

A patient's body temperature rises while hiking. What is the stimulus, control centre and effector?

Stimulus = temperature above 37°C; control centre (and receptor) = hypothalamus; effectors = sweat glands, dilating skin blood vessels

A person is very cold. Name two effectors and what they do

Skin blood vessels constrict (conserve heat); skeletal muscles shiver (make heat). The thyroid also raises metabolism

The thyroid gland is pinned at a station. What is its role in temperature homeostasis?

Effector. It releases thyroid hormone (T3/T4) to raise metabolic rate

A hypothalamic lesion prevents temperature control. Which feedback components are damaged?

Receptor and control centre. The hypothalamus is both

A type 1 diabetic can't produce insulin. Which component of the glucose loop is affected?

The pancreas (detector + control centre) can't send its signal (insulin); blood glucose stays high

After a big carb meal, the pancreas releases insulin. Is this positive or negative feedback?

Negative. Insulin brings high blood glucose back down

Na+ entry opens more Na+ channels, letting more Na+ in. What feedback type?

Positive feedback (action potential)

In a patient with no platelets, which part of the clotting loop still exists?

The stimulus (the broken vessel). Platelets are the detector, control centre and effector

What ends the positive feedback loop of labour?

Birth (parturition) removes the cervical stretch stimulus

Lactation: what is the effector?

Breast myoepithelial cells (contract to eject milk in response to oxytocin)

A patient reports nausea; the nurse measures a fever. Which is the sign and which is the symptom?

Fever = sign (objective, measured); nausea = symptom (subjective, reported)

A drug blocks Na+ leak channels. What happens to the resting membrane potential?

Becomes more negative. Less positive Na+ leaks in

A mutant Na+/K+ pump moves 2 Na+ out and 4 K+ in. Effect on the membrane?

Depolarizes (more positive). More positive charge now enters than leaves

A drug blocks voltage-gated K+ channels. Which AP phase is NOT affected?

Depolarization. That phase depends on voltage-gated Na+ channels

A drug blocks voltage-gated K+ channels. Which phases ARE affected?

Repolarization, hyperpolarization and the relative refractory period

A toxin blocks voltage-gated Na+ channels on the axon. What happens?

No action potential can be generated or propagated

A neuron receives two small EPSPs a few milliseconds apart at the same spot. What can happen?

Temporal summation. If they reach threshold (~-55 mV) at the axon hillock, an AP fires

A neuron gets more excitatory than inhibitory input, but stays below threshold. Result?

An EPSP (depolarized) but no action potential

A second stimulus arrives during repolarization. Can a new AP fire?

No. This is the absolute refractory period

A strong stimulus arrives during the hyperpolarization phase. Can a new AP fire?

Yes, but it's harder. This is the relative refractory period

How does the nervous system signal "this pain is stronger"?

Higher AP frequency. AP amplitude is always the same (all-or-nothing)

In Lambert-Eaton syndrome, presynaptic voltage-gated Ca2+ channels don't work. What fails?

Neurotransmitter release. Ca2+ influx triggers vesicle fusion

A patient takes an acetylcholinesterase inhibitor. What happens to ACh in the synapse?

ACh increases (not broken down) → more neurotransmission

A patient takes atropine. What happens to cholinergic neurotransmission?

Decreases. Atropine blocks ACh (muscarinic) receptors

A patient takes fluoxetine (SSRI). What happens?

Serotonin reuptake blocked → more serotonin stays in the synapse

A patient takes an MAO inhibitor. Which NT is NOT affected?

Acetylcholine. MAO breaks down catecholamines (and serotonin), not ACh

Someone grabs a live AC wire and can't let go. What's happening and why?

Tetany (death grip). Forearm flexors are stronger than extensors

Why can't an AP travel backwards up the axon?

The membrane behind it is in its refractory period

Why is the heart able to contract as one synchronized unit?

Electrical synapses (gap junctions) between cardiac cells

A patient has expressive aphasia (knows what to say but can't produce speech). Which area and lobe?

Broca's area, frontal lobe

A stroke patient speaks fluently but makes no sense and can't understand speech. Which area?

Wernicke's area (posterior superior temporal gyrus, temporal lobe)

After an injury, a patient's personality and problem solving change. Which lobe?

Frontal lobe

A lesion of the left precentral gyrus causes what?

Weakness/paralysis on the RIGHT side of the body. Motor cortex controls the opposite side

A lesion of the right postcentral gyrus causes what?

Loss of touch sensation on the LEFT side of the body

A patient with MS has slowed reactions. Is the problem conduction or transmission, and why doesn't it heal?

Conduction. CNS oligodendrocytes don't regenerate, and one lost oligodendrocyte affects many axons

Why do most Guillain-Barré patients recover within weeks?

PNS Schwann cells dedifferentiate, multiply and remyelinate axons

A lesion cuts the corpus callosum. What fibre type, and what is impaired?

Commissural fibres; communication/coordination between hemispheres

The fornix is pinned. What fibre type is it?

Association fibre (connects areas within one hemisphere)

Which fibre type is the internal capsule, and what does it carry?

Projection fibres; motor and sensory info between cortex and brainstem/spinal cord

Damage around the lateral ventricles causes memory loss and emotional changes. Which system?

Limbic system

Damage lateral to the ventricles causes trouble with basic movement. Which structures?

Basal nuclei (caudate, putamen, globus pallidus)

A specimen shows white matter. What gives it its colour and which CNS cell makes it?

Myelin; oligodendrocytes

Why does touch travel faster than dull, aching pain?

Touch uses large myelinated A-beta fibres; dull pain uses small unmyelinated C fibres

A specimen under the microscope shows branched, striated cells. What muscle?

Cardiac muscle

During contraction, which sarcomere parts shorten and which stays the same?

H zone and I band shorten; A band stays the same

Why does rigor mortis occur?

No ATP after death, so myosin can't detach from actin

A drug prevents Ca2+ release from the sarcoplasmic reticulum. What happens?

No contraction. Ca2+ is needed to bind troponin and move tropomyosin off the binding sites

What lets an AP reach the deep myofibrils of a large muscle fibre?

T-tubules

A bodybuilder's biceps get bigger. Did the number of fibres increase?

No. Each fibre gains more myofibrils/sarcomeres (hypertrophy)

A leg cast is removed after 6 weeks and the calf is smaller. Term?

Atrophy (from immobilization)

Why is maximum tetanic force 3-5x greater than a single twitch?

Repeated APs let Ca2+ build up, so more cross-bridges form

A marathon runner relies mostly on which fibre type?

Slow oxidative (fatigue resistant, aerobic)

During a heavy squat, which fibres are recruited last?

Fast glycolytic (largest; size principle)

Why does a muscle produce less force when overstretched?

Too little actin-myosin overlap, so too few cross-bridges

A hockey player is hit at the side of the head over the pterion. Which vessel and which bleed?

Middle meningeal artery → epidural hematoma

An older patient after a fall has a slow venous bleed. Which space?

Subdural space (bridging veins / venous sinus)

A ruptured cerebral artery aneurysm bleeds into which space?

Subarachnoid space

A stroke causes numbness in the LEFT hip and leg. Which artery?

Right anterior cerebral artery (supplies the medial cortex/lower limb area)

A stroke causes weakness of the RIGHT face and arm, plus language problems. Which artery?

Left middle cerebral artery

A stroke causes loss of the LEFT visual field. Which artery?

Right posterior cerebral artery (occipital lobe)

Why doesn't the circle of Willis prevent a stroke from a clot in the middle cerebral artery?

The circle only protects before it; terminal cerebral arteries have no anastomoses

A clot blocks a cerebral artery. Stroke type and treatment?

Ischemic; anticoagulants

A cerebral vessel ruptures. Stroke type and treatment?

Hemorrhagic; stop the bleed (anticoagulants would worsen it)

MRI: lateral and 3rd ventricles enlarged, 4th ventricle normal. Where is the blockage?

Cerebral aqueduct

MRI: only the right lateral ventricle is enlarged. Where is the blockage?

Right interventricular foramen

A doctor needs a CSF sample. Where does the needle go?

Lumbar puncture into the subarachnoid space in the lower back (below where the cord ends, L1-L2)

A pregnant patient gets an epidural. Which space receives the anaesthetic?

Epidural space (fat and vessels outside the dura)

Where does CSF re-enter the blood?

Through arachnoid granulations into the superior sagittal sinus

Why can't many water-soluble drugs reach the brain?

Blood-brain barrier: endothelial tight junctions + astrocyte processes block hydrophilic molecules

Trace venous blood from the top of the brain to the neck

Superior sagittal sinus → confluence of sinuses → transverse → sigmoid → internal jugular vein

A patient can't shrug the right shoulder. Which nerve?

Right CN XI (accessory) - trapezius

A patient's tongue doesn't move properly. Which nerve?

CN XII (hypoglossal)

A patient has lost sensation on the cheek. Which nerve and branch?

CN V, maxillary branch (V2)

A patient can't chew properly. Which nerve?

CN V, mandibular branch (V3) - muscles of mastication

A patient has a droopy eyelid and the eye rests down and out. Which nerve?

CN III (oculomotor)

A patient's right eye can't look laterally and drifts medially. Which nerve?

Right CN VI (abducens) - lateral rectus

A basilar artery stroke damages the pons. Which cranial nerve deficits are likely?

CN V-VIII, e.g. loss of facial (cheek) sensation from CN V

A patient has lost taste on the front of the tongue. Which nerve?

CN VII (facial)

A patient has lost taste on the back of the tongue and has trouble swallowing. Which nerve?

CN IX (glossopharyngeal)

A drug reduces vagus nerve output. What happens to heart rate?

It increases (less parasympathetic braking)

Right facial nerve is cut (LMN, like Bell's palsy). What deficit?

Complete paralysis of the entire RIGHT side of the face, including the forehead

A stroke damages the left motor cortex for the face (UMN). What deficit?

Weakness of the lower RIGHT face; forehead is spared (bilateral input)

Damage to the superior colliculi causes what?

Visual reflex deficits (e.g. tracking)

You turn toward a sudden loud noise behind you. Which midbrain structure is involved?

Inferior colliculus (auditory reflexes)

Parkinson's disease: which structure degenerates and what is lost?

Substantia nigra (midbrain); dopamine to the basal nuclei

A lesion of the right cerebellar hemisphere causes clumsiness on which side?

Right side (cerebellum is ipsilateral); limbs

A patient sways and can't keep the trunk steady. Which part of the cerebellum?

Vermis (axial control)

A brainstem lesion stops breathing and heart rate control. Which part?

Medulla

Where do the corticospinal (motor) tracts cross?

Pyramidal decussation in the medulla

The dorsal horn of the spinal cord is damaged. Sensory or motor loss?

Sensory (dorsal = sensory, ventral = motor)

A patient has damage to the hippocampus. What type of memory is most affected?

Forming new episodic (declarative) memories

A patient can still ride a bike but can't remember what they ate this morning. Which memory types?

Procedural memory intact (cerebellum/basal nuclei); new episodic memory impaired