Unit 2 Human Physiology

Tactile Disks (Merkel Cells)

Fine touch and pressure; small receptive fields= high sensitivity; slow to adapt (TONIC)

Meissner’s receptors

fine touch, pressure, vibration; rapidly adapting (PHASIC)

Pacinian Corpuscles

deep pressure, pulsing stimuli; Rapidly adapting (PHASIC)

Ruffini Corpuscles

pressure; slow to adapt (TONIC)

Pain

Nociceptors, simple receptor, TONIC

Temperature

thermoreceptor, simple, PHASIC

Pressure

barroreceptors, complex, PHASIC

Chemicals

chemoreceptors, complex, can be both phasic and tonic

Vision

special senses, rods and cones (photoreceptors), METABOTROPIC

Hearing

special senses; hair cells in the organ of corti, stereocilia, IONOTROPIC, mechanoreceptor

Equilibrium and Balance

special senses; hair cells in vestibular complex, IONOTROPIC, mechanoreceptors

Taste

special senses, chemoreceptors, gustatory cells in taste buds (Type 1, 2, 3)

Smell

special senses, odorant binding molecules, olfactory cilia, METABOTROPIC

Position

complex, proprioceptors, TONIC

Type 1 Gustatory Cell

senses salt; IONOTROPIC

Type 2 gustatory cell

senses bitter, sweet, umami; METABOTROPIC

Type 3 gustatory cell

senses sour; IONOTROPIC

Retinitis pigmentosa

degeneration of photoreceptor cells

Color blindness

inability to detect specific color due to defective rhodopsin or sensory receptor cells

Posterior Column pathway

fine touch, pressure, vibration, proprioception; ascending

Anterior spinothalamic pathway

crude touch, deep pressure; ascending

Lateral spinothalamic pathway

pain, temperature; ascending

Spinocerebral pathway

proprioceptive information from muscle spindles, golgi tendon organs, and joint capsules; ascending

Medial descending pathway

integration and feedback between the extrapyramidal and pyramidal tracts; change in position of upper body, response to bright lights, noises, and sudden movements, mediates arousal; UNCONSCIOUS

Lateral descending pathway

distal limb movement control and upper limb muscle tone; UNCONSCIOUS

Corticobulbar descending tracts

synapse onto motor neurons in cranial nerve motor nuclei (lower motor neuron); cranial nerve output; CONSCIOUS

Lateral corticospinal descending tracts

fine voluntary motor control of the upper limbs; synapse onto alpha motor neurons in anterior horn. CONSCIOUS

Anterior corticospinal descending tracts

voluntary movements of the trunk, shoulders, and neck (postural adjustments); CONSCIOUS

ALS

degeneration of upper and lower motor neurons; destruction of motor neurons causes atrophy of muscles

Parkinson’s disease

loss of cerebral nuclei inhibition (upper motor neurons). Increase in muscle tone, opposing muscle groups do not relax, results in jerky movements.

Myasthenia gravis

autoimmune disorder characterized by the self recognition and destruction of nicotinic acetylcholine receptors; treated with acetylcholinesterase inhibitors

Titin

large protein that provides elastic rebound from contraction; connects M line to Z disk

Nebulin

provides additional structural support for actin thin filaments; not elastic

Isotonic contraction

contraction force remains the SAME and muscle length CHANGES

Isometric contraction

contraction force is MAXIMAL muscle length DOES NOT change

Latency period

brief delay between stimulus and the onset of contraction

Contraction period

cross bridges form and tension increases as actin and myosin interact

Relaxation period

calcium ions are pumped back into the sarcoplasmic reticulum, cross bridges detach, and muscle tension decreases. 

Summation

occurs when a second stimulus arrives before the muscle has completely relaxed from the first twitch.

Treppe

when a muscle is stimulated repeatedly at the same strength after a resting period, the first few contractions gradually increase in strength.

Incomplete tetanus

at a higher frequency of stimulation, the muscle doesn’t have time to fully relax between twitches; maximal tension is not yet reached, still see individual relaxations

Complete tetanus

at very high frequency of stimulation, there is no relaxation between stimuli

Motor unit

a motor neuron and ALL of the muscle fibers it innervates