Physiology Flashcards
Using a single sentence for each, define the following terms 5
Myofibre
abductor
Perimysium
T-tubules
Zdisc
Myofibre- this is a single skeletal muscle cell which nis also known as muscle fibre/ muscle cell
Abductor- muscle that moves the limb away from the middle of the body
perimysium- layer of connective tissue that surrounds a fascicle in the muscle(collection of cells)
T-tubules- extensions of the reticular sarcoplasm in which action potential travel through.
Z-disc- Lines which are part of the sarcomee this is where thick and thin fillaments cross and this form the beginning and end of a sarcomere.
. Using a clearly labelled diagram briefly describe the structure of myosin
Has two heads which consist of an actin binding site and an ATP-pase binding size.
made up of four chains
two identical
two unendetical
MHC are identecal
MLC are not identical
it iks a hexamore
Define a muscle twithch and describe each of its phasis
A muscle twitch is the simplest contractile unit caused by a single action potential.
three phases
Latent phase in which there is a release of calcium in the first teo seconds from the terminal cisternia causing release of ADP and phosphate in the heads.
Contraction phase- This is where the tension increases to a peak meaning that there is an increse in calcium ions binding the troponin exposing more active sites on thin filaments being exposed and cross bridge interactions occuring.
Relaxation phase- clacium levels drop, active sites become covered by the complex number of cross bridges declines.
. Define the term refractory period of a neuronal action potential. Briefly describe the
roles played by voltage-gated Na+
channels during the absolute and relative refractory
periods.
Refractory: The time during which it is impossible (absolute) or when a stronger
stimulus is required (relative) to induce a new action potential soon after triggering one.
(1 mark).
Na channels: During depolarisation when both the activation and inactivation gates are
open and when the inactivation gate eventually closes, the channel is unresponsive to
any further stimulation creating absolute refractory period. Subsequently inactivation
gates start to open during repolarisation (recovery from inactivation), and depending on
the number of channels recovering from inactivation the nerve is responsive to stronger
stimuli (relative). (3 marks)
Briefly outline any four pathophysiological mechanisms through which chronic pain can
arise.
Guideline:
Any of the following:
a) Pain memory creation triggered by a slow healing process- wind up phenomenon –
creation of pain memory via glutamate/AMPA/NMDA receptor.
b) Nerve injury- neuropathic pain – involvement of neurotrophins in nerve sprouting or
neuroma formation – ectopic activation and abnormal synapses.
c) Autonomic stress response – sympathetically–maintained pain via sympathetic outflow
– local vasocontriction, increased metabolic rate, tissue damage – hyperalgesic response
causing further stress response.
d) Peripheral pain sensitisation – persistent stimulus – neurogenic inflammatory response
involving vessels, cells and recruitment of silent nociceptors
e) Central sensitisation – a) WDR neuron involvement (b) altered descending pathway
modulation (c) cortical reinforcement – reward/benefit.
List 6 function of skeletal muscle.
Converts chemical energy into force and mechanical work (movement and
locomotion).
* Maintains posture and body position.
* Support soft tissues (abdominal wall, floor of the pelvic cavity).
* Encircle openings of the digestive and urinary tracts.
* Heat production.
* Reservoir for protein storage
- Using a clearly labelled diagram, briefly describe the cross-bridge cycle. (12 marks
1.) resting fibre, cross-bridge not attached to actin
2) cross-bridge binds to actin
3) power stroke causes filaments to slide
4)a New ATP binds to myosin head, allowing it to release from actin.
5) ATP is hydrolysed, causing cross-bridge to return to its original orientation
a. Define the term peripheral pain sensitization. (1 marks)
b. Briefly describe three physiological responses that lead to the condition.
(4½ marks)
Guideline:
Sensitization: Exaggerated pain responses at or immediately around a site of tissue injury.
Responses:
- vascular - bradykinin release and increased prostaglandin sensitivity.
- cellular - mast cells (histamine); platelets (serotonin).
- neuronal/nociceptor - changes in threshold (recruitment of other local or silent
nociceptors).
Draw a sketch of an action potential and label the absolute and relative refractory
periods.
b. Briefly describe the role played by voltage-gated Na+
channels during these periods.
(2 marks)
…
Guideline:
Sketch: absolute to start at threshold and Relative during repolarization.
Voltage-gated Na channels: Absolute – channels fully open hence unresponsive; Relative –
channels recovering from inactivation, therefore response is stimulus strength-dependent. 1
mark for correct diagram
Using a clearly labelled diagram, describe how the patellar reflex functions. (8 marks
Patellar tendon is tapped
Spindle receptors in the quadriceps are stretched
Impulse sent to the spinal cord along the sensory neuron
Direct synapse with motor neuron
action potential is generated in the motor neuron.
Quadriceps contract
raises the leg
Involuntary reaction
. Using a single sentence for each, define the following terms: (6 marks)
(a) myofibril
(b) adductor
(c) endomysium
(d) M line
(e) motor unit
(f) summation
Myofibril- a single skeletal muscle/ muscle fibre
Adductor- this are muscles that move the limb towards the midline of the body.
Endomysium- connective tissue surrounding the cell of musculoskelenous muscle.
M-Line- this is the line that bisects the sarcomere
Motor Unit- A motor unit is a functional unit consisting of a motor neuron and the muscle fibers it innervates, responsible for generating muscle contractions in response to nervous system signals.
Summation- occurs when successive stimuli arrive before the relaxation phase has been complete.
State what percentage of total body calcium is contained in the plasma.
1%
State the name of the fibrous connective tissue that covers tissue that covers the surface of the bone.
Periosteum
Describe three ways in which parathyroid hormone (PTH) increases plasma calcium
concentration. (3 marks)
Describe three ways in which parathyroid hormone (PTH) increases plasma calcium
concentration. (3 marks)
It stimulates bone resorption; enhances intestinal calcium absorption, increases renal calcium
absorption
Name three factors that determine a bone’s response to mechanical loading.
Magnitude of strain
Rate of strain
distribution of strain
frequency of strain cylces
