Human Physiology IV: Main Exam, 26 March 2026

Mount Kenya University · Department of Clinical Sciences · Diploma in Community Oral Health, Diploma in Dental Technology · DDS2111/DMP2104

Human Physiology IV past paper from Mount Kenya University 2025-2026 with model answers for each question.

SECTION A: SHORT ANSWER ESSAY QUESTIONS (30 marks)

Answer ALL questions. Each question carries 6 Marks.

1. Outline the roles of melanin and keratin in the skin. (6 marks)

Model answer
  • Melanin: absorbs ultraviolet radiation, protecting deeper skin layers from DNA damage.
  • Melanin: contributes to skin colour, influencing thermoregulation by reflecting/absorbing solar heat.
  • Melanin: scavenges free radicals, reducing oxidative stress.
  • Keratin: provides mechanical strength and waterproofing to the epidermis.
  • Keratin: forms a barrier that limits transepidermal water loss.
  • Keratin: aids in the formation of the cornified layer, protecting against abrasion and microbial invasion.

2. State the structural organization of the skin, naming its major layers and one function of each. (6 marks)

Model answer
  • Epidermis (outermost): provides a protective barrier and prevents water loss.
  • Dermis: contains collagen and elastin; supplies nutrients, houses blood vessels and sensory receptors.
  • Hypodermis (subcutaneous tissue): stores fat for insulation and energy, and anchors skin to underlying structures.

3. Outline six functions of the skin that contribute to maintaining normal body physiology. (6 marks)

Model answer
  • Regulates body temperature through sweating and vasomotor control.
  • Protects against mechanical injury and UV radiation.
  • Prevents dehydration by limiting transepidermal water loss.
  • Synthesises vitamin D3 via UV‑B exposure.
  • Houses sensory receptors for touch, pain, temperature and pressure.
  • Acts as a barrier to microbial invasion and participates in immune responses.

4. State six differences between normal body temperature and fever in terms of physiological regulation. (6 marks)

Model answer
  • Set‑point: normal temperature is tightly regulated around 37 °C; fever raises the hypothalamic set‑point.
  • Trigger: pyrogens (exogenous or endogenous) induce fever; normal temperature is maintained by routine metabolic heat production.
  • Heat production: fever increases basal metabolic rate and shivering; normal state relies on basal metabolism.
  • Vasomotor response: fever causes peripheral vasoconstriction initially, then vasodilation for heat loss; normal state maintains balanced vasomotor tone.
  • Behavioural changes: fever produces chills and seeking warmth; normal temperature has no such drives.
  • Duration: fever is transient until the set‑point resets; normal temperature is continuous.

5. Identify six types of general sensory receptors and state the stimulus detected by each. (6 marks)

Model answer
  • Mechanoreceptors (Meissner’s corpuscles): detect light touch and low‑frequency vibration.
  • Mechanoreceptors (Pacinian corpuscles): detect deep pressure and high‑frequency vibration.
  • Thermoreceptors: detect changes in temperature (cold or warm).
  • Nociceptors: detect tissue‑damaging stimuli (pain).
  • Proprioceptors (muscle spindles): detect muscle stretch and length.
  • Proprioceptors (Golgi tendon organs): detect tension in tendons.

SECTION B: LONG ANSWER ESSAY QUESTIONS (40 marks)

Answer Question ONE and any other ONE question. (Each question carries 20 Marks.)

1. Discuss the physiology of body temperature regulation and the clinical consequences of abnormal temperature states. In your answer:

  1. a) Explain how heat is produced in the human body.
    Model answer
    • Heat production: basal metabolic processes (oxidation of nutrients) generate ATP, releasing heat as a by‑product.
    • Heat production: shivering thermogenesis – rapid involuntary muscle contractions increase metabolic rate and heat output.
    • Heat production: non‑shivering thermogenesis in brown adipose tissue via uncoupling protein‑1, converting fatty‑acid oxidation energy to heat.
    • Heat production: hormonal stimulation (thyroid hormones, catecholamines) raises basal metabolic rate, augmenting heat generation.
    • Heat production: post‑prandial thermogenesis (diet‑induced thermogenesis) after food intake.
    • Heat production: physical activity – skeletal muscle contraction converts chemical energy to mechanical work and heat.
  2. b) Describe the mechanisms by which heat is lost.
    Model answer
    • Radiation: emission of infrared heat from skin surface.
    • Conduction: direct transfer of heat to cooler objects in contact with skin.
    • Convection: movement of air or water across skin, carrying heat away.
    • Evaporation: loss of heat when sweat vaporises from the skin.
    • Respiratory heat loss: warm air exhaled from the lungs carries heat away.
    • Vasodilation: increased skin blood flow enhances heat transfer to the environment.
  3. c) Discuss the clinical consequences of fever, hypothermia, and hyperthermia
    Model answer
    • Fever: enhances immune function, inhibits microbial growth, raises metabolic rate; may cause dehydration, tachycardia, and increased oxygen demand.
    • Hypothermia: reduces enzymatic activity, depresses CNS, leads to shivering, arrhythmias, coagulopathy, and can progress to cardiac arrest.
    • Hyperthermia (heat stroke): causes protein denaturation, cellular injury, CNS dysfunction, coagulation disturbances, and multi‑organ failure if not treated promptly.

2. Explain the physiology of the visual and auditory systems. In your answer:

  1. a) Describe the visual pathway from the retina to the visual cortex.
    Model answer
    • Retina: photoreceptors (rods & cones) convert light into neural signals.
    • Optic nerve (CN II): carries retinal ganglion cell axons to the optic chiasm.
    • Optic chiasm: fibers from nasal retina cross to the opposite side.
    • Optic tract: continues posteriorly to the lateral geniculate nucleus (LGN) of thalamus.
    • Lateral geniculate nucleus: relays and organizes visual information.
    • Optic radiations (geniculocalcarine tract): project from LGN to the primary visual cortex.
    • Primary visual cortex (V1, Brodmann area 17): located in the occipital lobe; initial cortical processing of visual input.
  2. b) Explain the role of the cochlea in hearing.
    Model answer
    • Sound wave entry: vibrations travel through the external auditory canal to the tympanic membrane.
    • Middle ear transmission: ossicles (malleus, incus, stapes) amplify and convey vibrations to the oval window.
    • Fluid movement: stapes motion creates pressure waves in the perilymph of the scala vestibuli.
    • Basilar membrane motion: pressure differences across the cochlear partition cause the basilar membrane to vibrate; specific frequencies peak at characteristic locations.
    • Hair cell activation: deflection of inner‑hair cell stereocilia opens mechano‑electrical transduction channels, generating receptor potentials.
    • Neurotransmitter release: depolarisation triggers glutamate release onto afferent auditory nerve fibers.
    • Auditory nerve firing: action potentials travel via the cochlear nerve to the brainstem for further processing.

3. Describe the physiology of taste, smell, and oral sensation. In your answer:

  1. a) Explain the physiology of taste and smell.
    Model answer
    • Taste (gustation): soluble chemicals dissolve in saliva, bind to G‑protein‑coupled receptors on taste receptor cells in taste buds (fungiform, foliate, circumvallate). Signal transduction via second messengers (IP₃/DAG for sweet, bitter, umami; cAMP for salty) leads to depolarisation and neurotransmitter release to afferent fibers of the facial (VII), glossopharyngeal (IX) and vagus (X) nerves.
    • Smell (olfaction): odorant molecules volatilise, enter the nasal cavity and dissolve in the mucus of the olfactory epithelium. They bind to olfactory receptors on bipolar neurons; activation of G‑protein (Golf) increases cAMP, opening cyclic‑nucleotide‑gated channels, causing depolarisation. Axons form the olfactory nerve (I) and project to the olfactory bulb, then via the olfactory tract to the piriform cortex, amygdala and orbitofrontal cortex for perception.
  2. b) Discuss the role of oral sensory receptors (pain, temperature, pressure, tooth sensation) in oral health practice.
    Model answer
    • Pain receptors (nociceptors): free‑nerve endings detect tissue damage; transmit via trigeminal (V) or glossopharyngeal (IX) pathways, alerting to caries, pulpitis or trauma.
    • Temperature receptors: thermoreceptors (cold and warm) in mucosa signal via the same cranial nerves, important for detecting thermal injury from hot foods or drinks.
    • Pressure receptors: mechanoreceptors (Meissner’s, Pacinian) in periodontal ligament sense bite force and tooth displacement, guiding occlusal adjustments.
    • Proprioceptive receptors: muscle spindles and joint receptors provide feedback on jaw position, aiding in functional rehabilitation.
    • Clinical relevance: assessment of these sensations helps diagnose pulp vitality, periodontal health, occlusal trauma and guides pain management and preventive strategies.

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