Recap theme 8 summary
Physiology
Electrical synapses and neurmuscular transmission
Central synapses Endplates
Multiple neurotransmitters Acetylcholine
Multiple receptors Always excitatory
IPSPs (Cl -) and EPSPs (Na+ and K+) Every EPP = action potential
Ionotropic or metabotropic Every muscle fiber innervated by 1 motor unit
Na+ and K+ currents
The cortical motor system
Types of muscle:
- Slow oxidative (fatigue resistant)
- Fast oxidative/glycolytic (fatigue resistant)
- Fast glycolytic (fatigable)
,Types of muscle contraction:
- Eccentric: muscle lengthens
- Concentric: muscle shortens
- Isometric: muscle length stays the same
Strength is determined by:
1. Amount of motor units
2. Frequency of action potentials (tetanisation)
Sarcopenia = loss of muscle mass (loss of fast motor units)
Dynapenia = loss of muscle strength
Sensation
Sensory receptors:
- Mechanoreceptors: detect physical deformation
- Thermoreceptors: detect temperature changes
- Nociceptors: detect pain
- Photoreceptors: detect light on the retina
- Chemoreceptors: detect CO2 and O2 levels in the blood
Classification of nerve fibers:
- Type A (myelinated) vs type C (unmyelinated)
- α σ (large small diameter)
Adaptation: action potential firing becomes less when exposed to same stimulus over time.
Slowest: joint capsule receptors and muscle spindles = tonic
Fastest: hair receptors = phasic
Sensory pathways:
- Dorsal column-medial lemniscal pathway: proprioception, touch, vibration
- Spinothalamic pathway: pain, temperature, crude touch
,Pain
Two types:
1. Nociceptive: detected by nociceptors
2. Neuropathic: damage or disease to somatosensory nervous system
Directed by different nerve fibers:
- A fibers: sharp pain
- C fibers: burning, aching pain
Referred pain: pain in organs go via same route as pain in cutaneous areas cutaneous
route is used more often pain in cutaneous area
Proprioception: notion of one’s body position.
- Golgi tendon organs: detect strength use of muscle
- Muscle spindles: detect muscle stretch
, Physiology of ageing – changes in organ systems
Health paradox: humans get older, but chronic, age related diseases and symptoms are
increasing.
Respiratory system
- Decreased chest wall compliance
- Increased lung compliance
- Decreased overall compliance increased resistance
- Decreased function of respiratory muscles
- “air trapping” increased FRC + RV lower FEV
- Diminished regulation of ventilation
- Decreased blood vessel compliance
Cardiovascular system
- Decreased compliance of arteries and veins
- Decreased compliance of myocardium decreased filling
- LV hypertrophy
- Increased SBP
- Decreased DBP
- Higher pulse pressure
- Diminished regulation
- Lower CO
Nervous system
- Central:
30% loss of brain mass
Less neurotransmitters
- Peripheral: loss of motor, sensory and autonomic fibers
- Autonomic:
Increased sympathetic stimulation
Defect baroreceptor reflex
Less sensitive β-adrenergic receptors
Lab measures
- Lower albumin
Physiology
Electrical synapses and neurmuscular transmission
Central synapses Endplates
Multiple neurotransmitters Acetylcholine
Multiple receptors Always excitatory
IPSPs (Cl -) and EPSPs (Na+ and K+) Every EPP = action potential
Ionotropic or metabotropic Every muscle fiber innervated by 1 motor unit
Na+ and K+ currents
The cortical motor system
Types of muscle:
- Slow oxidative (fatigue resistant)
- Fast oxidative/glycolytic (fatigue resistant)
- Fast glycolytic (fatigable)
,Types of muscle contraction:
- Eccentric: muscle lengthens
- Concentric: muscle shortens
- Isometric: muscle length stays the same
Strength is determined by:
1. Amount of motor units
2. Frequency of action potentials (tetanisation)
Sarcopenia = loss of muscle mass (loss of fast motor units)
Dynapenia = loss of muscle strength
Sensation
Sensory receptors:
- Mechanoreceptors: detect physical deformation
- Thermoreceptors: detect temperature changes
- Nociceptors: detect pain
- Photoreceptors: detect light on the retina
- Chemoreceptors: detect CO2 and O2 levels in the blood
Classification of nerve fibers:
- Type A (myelinated) vs type C (unmyelinated)
- α σ (large small diameter)
Adaptation: action potential firing becomes less when exposed to same stimulus over time.
Slowest: joint capsule receptors and muscle spindles = tonic
Fastest: hair receptors = phasic
Sensory pathways:
- Dorsal column-medial lemniscal pathway: proprioception, touch, vibration
- Spinothalamic pathway: pain, temperature, crude touch
,Pain
Two types:
1. Nociceptive: detected by nociceptors
2. Neuropathic: damage or disease to somatosensory nervous system
Directed by different nerve fibers:
- A fibers: sharp pain
- C fibers: burning, aching pain
Referred pain: pain in organs go via same route as pain in cutaneous areas cutaneous
route is used more often pain in cutaneous area
Proprioception: notion of one’s body position.
- Golgi tendon organs: detect strength use of muscle
- Muscle spindles: detect muscle stretch
, Physiology of ageing – changes in organ systems
Health paradox: humans get older, but chronic, age related diseases and symptoms are
increasing.
Respiratory system
- Decreased chest wall compliance
- Increased lung compliance
- Decreased overall compliance increased resistance
- Decreased function of respiratory muscles
- “air trapping” increased FRC + RV lower FEV
- Diminished regulation of ventilation
- Decreased blood vessel compliance
Cardiovascular system
- Decreased compliance of arteries and veins
- Decreased compliance of myocardium decreased filling
- LV hypertrophy
- Increased SBP
- Decreased DBP
- Higher pulse pressure
- Diminished regulation
- Lower CO
Nervous system
- Central:
30% loss of brain mass
Less neurotransmitters
- Peripheral: loss of motor, sensory and autonomic fibers
- Autonomic:
Increased sympathetic stimulation
Defect baroreceptor reflex
Less sensitive β-adrenergic receptors
Lab measures
- Lower albumin
