Lab Midterm Study Notes

• Study notes for the lab midterm are presented below

Getting Started with LT

• Pulse transducer is the equipment used for pulse reading
• A pulse reading measures heart rate, counting beats per minute
• Pulse readings provide insight into cardiovascular health
• Pulse readings reflect changes in pressure from pulsatile blood flow in the arteries, indicated by a pressure wave with each heartbeat

Biological Membranes

• Spectrophotometer helps measure absorbance, reflection, and transmittance of light through a substance
• Spectrophotometer process involves turning on the device before setting the wavelength to 460 nm and waiting 15 minutes for warm-up
• A "blank" solution contains all components of a sample, except the substance being measured
• A blank calibrates the spectrophotometer for a baseline reading, accounting for optical density due to the tube and solvent

Components and Functions of Biological Membranes

• Saturated fatty acids have no double bonds, resulting in linear orientation
• Unsaturated fatty acids have one or more double bonds, creating "kinks" in their structure
• Saturated fatty acids are solid at room temperature, while unsaturated fatty acids are liquid
• Membranes with unsaturated lipids are more flexible due to disrupted lipid packing, increasing permeability to smaller molecules
• Phospholipids form the majority of the membrane in a double layer
• Hydrophobic tails face inward while hydrophilic heads face outward, allowing for bilayer formation with flexibility
• Integral proteins transport molecules across the membrane through channels or carriers
• Integral proteins are embedded in the phospholipid bilayer and also act as receptors, relaying signals into the cell and maintaining cell shape
• Cholesterol maintains membrane fluidity, provides support, stabilizes, and reduces permeability to water-soluble molecules
• Cholesterol allows the membrane to adjust to temperature and stress
• Glycolipids maintain cell membrane stability and facilitate cell recognition, through lipids with attached carbohydrates
• Hot temperatures increase membrane fluidity by making phospholipids more fluid and mobile
• Cold temperatures decrease membrane fluidity by causing phospholipids to pack more tightly

Sensory Physiology

• Equilibrium is perceived by the semicircular canals filled with endolymph, which detect head rotations
• The utricle and saccule detect linear acceleration and gravity's effects to maintain balance
• Gustation (taste) receptors detect sweet, salty, sour, and bitter flavors

Touch and Pain

• Proprioception is the perception of body position, providing the awareness of where body regions are located
• Nociception is the perception of pain
• Transduction involves nociceptors converting harmful stimuli into electrical signals
• Transmission: Electrical signals from stimuli travel to the brain and spinal cord via peripheral nerves
• Perception: The brain interprets pain signals, resulting in the conscious experience of pain
• Modulation: The nervous system regulates pain through inhibitory and excitatory pathways

Adaption of the Eye

• Adapting the eye includes pupillary reflexes and photoreceptor adjustments, optimizing vision in different light levels
• Accommodation is controlled by the parasympathetic nervous system, contracting the ciliary muscle for near vision
• Ciliary muscles contract during near vision and relax during far vision
• Pupils constrict in light and dilate in darkness
• The pupillary light reflex is polysynaptic

Sensory Photoreceptors of the Eye

• Rods enable black-and-white vision in low light
• Cones enable color and daylight vision

Electroencephalography (EEG)

• EEG equipment involves connecting CH1 NEG, CH1 POS, and EARTH electrode cables to the Bio Amp cable and attaching these to the volunteer via disposable ECG electrodes
• EEG is usefull to detect epilepsy/seizures, autism, tumors, stroke, and alzheimer's
• EEGs captures electrical activity in the brain as waveforms, reflecting neuronal activity via postsynaptic potentials (PSPs)

EEG Waveforms

• Gamma (30-50 Hz) indicates high-level cognitive function, problem-solving, thinking, focus, and peak mental performance
• Beta (13-30 Hz) indicates awake, alert individuals with eyes open
• Alpha (8-13 Hz, 30-50 amplitude) indicates relaxation with eyes closed
• Theta (4-8Hz) is normal for sleeping adults and awake children
• Delta (0.5-4 Hz) is dominant in sleep stages 3 and 4, not seen in the conscious adult, and has the highest amplitude and lowest frequency
• Brain activity correlates to the frequency and amplitude of EEG, where more active brain higher frequency and lower amplitude

Brain Structure and Pathways

• Frontal lobe houses the motor cortex and is responsible for executive functioning, abstract thought, planning, and social behavior
• Parietal lobe contains somatosensory cortex and processes sensory information, including auditory, visual, somatosensory, and proprioceptive information
• Temporal lobe has the auditory cortex (hearing), Wernicke's area, and the hippocampus (memory)
• Occipital lobe contains the visual cortex

Neuronal Divisions in Brain Lobes

• Frontal lobe: Motor control, decision-making, speech, precentral gyrus (motor cortex), Prefrontal cortex, Broca's area
• Parietal lobe: Sensory perception, spatial awareness, Postcentral gyrus (somatosensory cortex), Somatosensory association area
• Temporal lobe: Hearing, language, memory, Primary auditory cortex, Auditory association area, Wernicke's area, Hippocampus
• Occipital lobe: Vision, Primary visual cortex, Visual association area
• Monosynaptic: Has one synapse between a sensory and motor neuron in reflexes
• Polysynaptic: Has multiple synapses, with interneurons for processing/inhibition of the reflex by the brain

Reflexes

• Stretch reflex (knee jerk) is monosynaptic, involving motor and sensory neurons
• Flexion withdrawal reflex- polysynaptic, withdrawing a limb from pain
• Plantar reflex- polysynaptic, stroking the sole causes the big toe to flex and foot to invert
• Ankle jerk reflex- monosynaptic; tapping the Achilles tendon dorsiflexes the foot

Brain Damage Markers

• Accommodation reflex: Constricts pupils to view near objects
• Babinski sign: Abnormal reflex in adults over 2 years; normal in children under 2 years
• Corneal (blink) reflex: Closes the eye to protect it from hazards
• Flexion withdrawal reflex: Removes a limb from painful stimuli
• Pupillary light reflex: Modifies pupil diameter in response to light
• Crossed extensor reflex: Occurs in conjunction with flexion-withdrawal to provide postural support

Neuronal Damage Levels

• Mild: Brief or no loss of consciousness, short-term memory loss (post-traumatic amnesia), mild neurological symptoms like headache, etc
• Moderate: Longer loss of consciousness (up to 24 hours), prolonged post-traumatic amnesia, neurological deficits, vomiting, and potential signs on neuroimaging
• Severe: Prolonged loss of consciousness (over 24 hours), significant neurological deficits, may be permanent, with signs of injury visible on neuroimaging
• Brain injury diagnosis hinges on extent/duration of consciousness loss, post-traumatic amnesia, and neurological deficits

Motor Neuron Lesions

• Upper motor neuron lesions show muscle paresis/paralysis, tenseness (hypertonia), spasticity, weakness without wasting, poor motor control, and exaggerated reflexes
• Upper motor neuron lesions show the clasp-knife response, muscle twitches/spasms, and the Babinski sign
• Lower motor neuron lesions show muscle paresis/paralysis, muscle wasting, reduced muscle tone (hypotonia), and diminished/absent reflexes
• Lower motor neuron lesions shows muscle fasciculation (twitches)
• Lesions in the brain affect muscle contraction, which indicate upper motor neuron lesions

Cerebrovascular Accident

• Cerebrovascular accident (CVA) or stroke occurs when blood flow to the brain is blocked
• Stroke initially decreases reflexes, can later increase due to loss of inhibitory control
• Spasticity, hyperreflexia, and the Babinski sign can be stroke consequences